研究者詳細 - 坪田　敏樹

論文 - 坪田　敏樹

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The investigation of activated carbon by K<inf>2</inf>CO<inf>3</inf> activation: Micropores- and macropores-dominated structure 査読有り国際誌

Khuong D.A., Kieu T.T., Nakaoka Y., Tsubota T., Tashima D., Nguyen H.N., Tanaka D.

Chemosphere 299 2022年07月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, the K2CO3 activation of bamboo was investigated in detail, and the structure and properties of the prepared activated carbons were tested for the feasibility of CO2 capture application and the potential for both ion and bacteria adsorption for use in the field of hazardous wastewater treatment. Activated carbons were produced with different activator ratios, from 0.5 to 6 according to the sample mass ratio. The ratio of H or O to C (H/C or O/C) increased with the increasing amount of K2CO3 added for the activation. The samples had a highly-porous microporous structure, in which the micropore volume was calculated to be 0.6 cm3 g−1 by the DR method of the CO2 adsorption isotherm at 298 K. The BET surface area and total pore volume estimated from the N2 adsorption isotherms at 77 K of the activated materials increased according to the increase of the K2CO3 impregnation ratio to a maximum value of 1802 m2 g−1 and 0.91 cm3 g−1, respectively. Moreover, the K2CO3-activated samples had a specific morphology, that is, macropores which are presumed to be derived from bubbles. The X-ray-CT images showed that the bubble-like structure is not only on the surface but also inside the samples. The results of gas adsorption methods, mercury porosimetry, and SEM showed the co-existence of micropores (<2 nm) and macropores (100–10,000 nm). The results highlighted the unique pore structure, that is, the coexistence of micropores and macropores that would contribute to forming solutions for carbon sequestration in the atmosphere and wastewater treatment.

DOI： 10.1016/j.chemosphere.2022.134365

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Activated carbon produced from bamboo and solid residue by CO2 activation utilized as CO2 adsorbents 査読有り国際誌

Duy AnhKhuong, Hong NamNguyen, ToshikiTsubota

Biomass and Bioenergy 148 106039 2021年05月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Bamboo and its solid residue after hydrothermal treatment were converted successfully into porous carbon by physical activation with the CO2 agent. The solid residue exhibits a higher potential to form activated carbon thanks to its very low ash content (almost 0%). The porosity and CO2 uptake of the carbon materials were characterized by the N2 and CO2 adsorption/desorption techniques. The results showed a dominant microporous structure in the carbon derived from both bamboo and solid residue. The highest BET surface area that the carbon material from bamboo could achieve was 976 m2 g−1, meanwhile, this value at the carbon prepared from solid residue activated at the same temperature was 1496 m2 g−1. The microporosity structure of activated carbon could be stimulated and enhanced at the optimal condition of CO2 activation. The CO2 adsorption capacity of the carbon made from bamboo and the solid residue was also analyzed with good capacity (3.4 mmol g−1) comparing to the 3 reference materials at the same condition of adsorption (293 K, 1 atm).

DOI： 10.1016/j.biombioe.2021.106039

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CO2activation of bamboo residue after hydrothermal treatment and performance as an EDLC electrode 査読有り国際誌

Duy Anh Khuong, Hong Nam Nguyen, Toshiki Tsubota

RSC Advances 11 ( 16 ) 9682 - 9692 2021年02月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

CO2activation of the solid residue of bamboo after hydrothermal treatment, which is used for the production of xylo-oligosaccharide, was investigated in detail. The reference temperature for carbonization and CO2activation was 800 °C. The activated carbon from a solid residue was demonstrated to have a higher potential for making EDLC electrodes than bamboo activated carbon thanks to its very low ash content (almost 0) and high porosity structure with a BET surface area up toca.2150 m2g−1. The electrochemical performance of ELDC electrodes prepared from solid residue-derived activated carbon in 1 M H2SO4aqueous solution was measured and well compared with carbon from bamboo. Through investigation, it is clear that the capacitance of the electrode made from the solid residue has a better capacity than that of raw bamboo.

DOI： 10.1039/d1ra00124h

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Utilization of pine tree biochar produced by flame-curtain pyrolysis in two non-agricultural applications 査読有り国際誌

Kalderis D., Tsuchiya S., Phillipou K., Paschalidou P., Pashalidis I., Tashima D., Tsubota T.

Bioresource Technology Reports 9 2020年02月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 Elsevier Ltd Main objective of this work was to demonstrate the applicability of biochars obtained from pine tree residues through low cost, easy to operate, flame-curtain pyrolysis, in two distinctively different applications. In the first application, it was shown that base-oxidized pine tree biochar had an excellent adsorption behavior towards U(VI) in aqueous solutions, achieving a qmax value of 800 mg g−1. It was also demonstrated that surface interactions with biochar's oxygen-containing groups dominated over physical interactions with the pore structure. In the second application, KOH-activated pine tree biochar showed a very promising behavior as an electrode material in an electron double-layer capacitor. Due to its high surface area (2500 m2/ g), capacitance values of 190 F g−1 at 10 mA g−1 for discharge process were achieved. As a conclusion, it was shown that flame-curtain pyrolysis biochars are suitable for non-agricultural applications, in the cases where soil application is not an option.

DOI： 10.1016/j.biteb.2020.100384

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Retraction Note: Low-cost novel nano-constructed granite composites for removal of hazardous Terasil dye from wastewater (Environmental Science and Pollution Research, (2022), 30, 34, (81333-81351), 10.1007/s11356-022-21367-8) 査読有り

Khalil M., Hanif M.A., Rashid U., Ahmad J., Alsalme A., Tsubota T.

Environmental Science and Pollution Research 31 ( 51 ) 2024年11月

掲載種別：記事・総説・解説・論説等（その他）

The Publisher has retracted this article in agreement with the Editor-in-Chief. An investigation by the publisher found a number of articles, including this one, with a number of concerns, including but not limited to compromised peer review process, inappropriate or irrelevant references, containing nonstandard phrases or not being in scope of the journal. Based on the investigation's findings the publisher, in consultation with the Editor-in-Chief therefore no longer has confidence in the results and conclusions of this article. The Publisher has not been able to obtain a current email address for Maria Khalil. The other authors have not responded to correspondence regarding this retraction.

DOI： 10.1007/s11356-024-35374-4

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Comprehensive Understanding of the Impact of Alkaline-Activated Bamboo-Derived Carbon for Enhancing Supercapacitor Performance 査読有り

Khuong D.A., Tsubota T., Nguyen H.N.

Journal of Physical Chemistry C 128 ( 41 ) 17313 - 17327 2024年10月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

This study explored the potential of steam-treated bamboo-derived activated carbon (AC) for electric double-layer capacitor (EDLC) applications, using KOH, K2CO3, and Na2CO3 as activation agents to improve electrode materials. The activation process significantly affected the textural properties: KOH enhanced the surface area and micropore volume, K2CO3 impacted micropores and macropores, and Na2CO3 contributed to mesopores and macropores. TEM and SEM images showed distinct morphologies, with K2CO3 exhibiting bubble-like structures and Na2CO3 displaying a foam-like appearance. X-ray photoelectron spectroscopy analysis revealed specific surface modifications of ACs. Electrochemical performance assessments, including charge-discharge behavior, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS), demonstrated the superiority of KOH-AC in EDLC applications due to its high specific area and microporosity. The discharge capacitance of EDLC made from KOH-AC reached 24 F g-1 at a current density of 100 mA g-1, while those from K2CO3 and Na2CO3-AC did not surpass 14 F g-1 under the same conditions. Fitting EIS data with the electrical circuit model partially revealed correlations between ion diffusion and capacitance values, although further durability studies are needed for practical applications. This investigation provides valuable insights into optimizing steam-treated bamboo-derived AC for advanced energy storage systems.

DOI： 10.1021/acs.jpcc.4c04228

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Valorization of bamboo and cedar bark residues for the production of biochars as adsorbents of CO<inf>2</inf> and radionuclides 査読有り国際誌

Trinh K.T., Khuong D.A., Viet D.D., Tsubota T., Ioannidis I., Pashalidis I., Kalderis D.

Sustainable Chemistry and Pharmacy 41 2024年10月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The escalating issues of rising CO2 emissions and radioactive pollution, specifically from isotopes like 232U and 241Am, present critical global environmental challenges. This study utilized bamboo and Japanese cedar as biomass sources for biochar production, aiming to investigate the influence of carbonization temperature on the biochars capacity to adsorb CO2 and radionuclides. The biochars were produced at 500, 600 and 700oC and underwent a comprehensive structural and material property analyses employing electron microscope, gas adsorption isotherms, and spectroscopy methods. Characterization revealed that the biochar samples predominantly consisted of micropores, whereas the Japanese cedar biochars exhibited elevated mesoporous surfaces compared to bamboo-derived biochars, along with the presence of oxygen-containing moieties on their surface. Remarkably, the results indicate a positive correlation between carbonization temperature and adsorption capacity for both CO2 and the radionuclides. Notably, biochars produced at 700 °C exhibited the highest CO2 adsorption capacity of 2.21 mmol g−1. While both bamboo and cedar biochars exhibited comparable adsorption behavior against CO2, Japanese cedar biochars demonstrated superior capacity for adsorbing 232U and 241Am compared to bamboo biochars. JC700 showed the optimum adsorption behavior, achieving 91 and 88% removal of 232U and 241Am at pH 4, respectively. These findings highlight the potential of both bamboo and Japanese cedar biochars as effective adsorbents for mitigating CO2 emissions and radioactive pollution.

DOI： 10.1016/j.scp.2024.101677

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Simultaneous syngas and CO<inf>2</inf> adsorbent production via rice straw gasification: An experimental study 査読有り国際誌

Nguyen H.N., Tran-Nguyen P.L., Khuong D.A., Tsubota T.

Biomass and Bioenergy 183 2024年04月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Despite being a promising biomass source for gasification, the practical use of rice straw in Vietnam is hindered by its low gasification efficiency. This study introduces an innovative approach by integrating the production of syngas and CO2 adsorbent during the gasification process of rice straw, departing from the conventional focus solely on improving gasification efficiency. Results showed that the gasification of rice straw, conducted in the 20 kWe commercial gasification system (PP20 All Power Lab), attained a thermal conversion efficiency of 58.7%. Syngas produced exhibited consistent composition, with CO and H2 content ranging from 12.1% to 15%, CO ranging from 16.9% to 22.1%, and CH4 ranging from 1.9% to 3.9% throughout the operation, demonstrating relative stability. Notably, a considerable amount of residual char, accounting for 22.1 wt% of the initial feedstock, was generated. Characterized by notable traits such as high surface basicity, aromaticity, and a dense concentration of (ultra-)micropores, the residual char demonstrates suitability for applications in CO2 adsorption. In controlled laboratory conditions (25 °C, 1 atm, without heat-mass transfer limitations), the adsorption capacity reached 1.2 mmol g−1. Transitioning to more practical conditions (40 °C, 1 atm, within a 2-cm adsorbent bed subject to diffusion constraints), the CO2 adsorption capacity of the residual char ranged between 2% and 4.8% of the adsorbent's weight, while the CO2/N2 selectivity measured between 25.5 and 29.7. These findings underscore the significant potential of integrating syngas and CO2 adsorbent production through rice straw gasification, indicating a promising avenue for sustainable energy and carbon capture technologies.

DOI： 10.1016/j.biombioe.2024.107137

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Autohydrolysis treatment of bamboo and potassium oxalate (K<inf>2</inf>C<inf>2</inf>O<inf>4</inf>) activation of bamboo product for CO<inf>2</inf> capture utilization 査読有り国際誌

Viet D.D., Thao D.T., Anh K.D., Tsubota T.

Frontiers of Chemical Science and Engineering 18 ( 4 ) 2024年04月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Typically, the hydroxide agents, such as sodium hydroxide and potassium hydroxide, which have corrosive properties, are used in the carbon activation process. In this study, potassium oxalate (K2C2O4), a less toxic and non-corrosive activating reagent, was used to synthesize activated carbon from the solid residue after autohydrolysis treatment. The effect of the autohydrolysis treatment and the ratio of the K2C2O4/solid residue are presented in this study. Moreover, the comparison between the activated carbon from bamboo and biochar from the solid residue are also reported. The resulting activated carbon from the solid residue exhibited a high surface area of up to 1432 m2·g−1 and a total pore volume of up to 0.88 cm3·g−1. The autohydrolysis treatment enhanced the microporosity properties compared to those without pretreatment of the activated carbon. The microporosity of the activated carbon from the solid residue was dominated by the pore width at 0.7 nm, which is excellent for CO2 storage. At 25 °C and 1.013 × 105 Pa, the CO2 captured reached up to 4.1 mmol·g−1. On the other hand, the ratio between K2C2O4 and the solid residue has not played a critical role in determining the porosity properties. The ratio of the K2C2O4/solid residue of 2 could help the carbon material reach a highly microporous textural property that produces a high carbon capture capacity. Our finding proved the benefit of using the solid residue from the autohydrolysis treatment as a precursor material and offering a more friendly and sustainable activation carbon process. (Figure presented.)

DOI： 10.1007/s11705-024-2402-8

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Valorization of Aloe vera waste for the production of Ca and P-rich hydrochars 査読有り国際誌

Kalderis D., Stavroulakis G., Tsubota T., Çalhan S.D.

Sustainable Chemistry for the Environment 5 2024年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

The production of gel from Aloe vera plants is an emerging industry, however the residual leaves are considered waste and are not utilized. The purpose of this work was to prepare hydrochars from Aloe vera leaves under different conditions, and determine the fate of macro- and micronutrients in the solid products, in view of developing a novel biofertilizer. In this framework, distilled water, citric acid and potassium hydroxide solutions were used as feedwaters and the experiments were performed at the temperatures of 180 and 220 °C and treatment times of 1 – 8 h. All obtained hydrochars had increased Ca and P contents compared to the feedstock, whereas the highest Ca and P concentration of 10.4% and 7382 mg kg−1, respectively, were achieved under alkaline conditions after 8 h of treatment. Citric acid promoted carbonization, achieving H/C = 1.11, O/C = 0.34 of the hydrochar obtained at 220 °C after 8 h of treatment. The use of KOH counterbalanced the production of acids from the degradation of the biomass, thus restricting the carbonization progress. The metals K, Fe, Cu and Mg showed high solubilization tendencies, however their concentrations on the hydrochars increased beyond the 4 h treatments due to precipitation and re-sorption phenomena. The N content in the hydrochars ranged between 0.56 – 1.12%, increasing with temperature and time due to the formation and precipitation of pyridine, pyrroline and pyrrolidine derivatives. Overall, due to the high ash content, low pH and increased Ca and P concentrations, the hydrochars may be suitable as substrates for the development of bio-fertilizers purposed for alkaline soils.

DOI： 10.1016/j.scenv.2023.100057

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Experimental investigation of CO<inf>2</inf> adsorption using adsorbents derived from residual char of agricultural waste gasification 査読有り国際誌

Nguyen H.N., Khuong D.A., Tsubota T.

Thermal Science and Engineering Progress 49 2024年03月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

This study proposed a novel approach, suggesting a cascading utilization of agricultural residues for both energy generation and the production of CO2 adsorbents through gasification. Gasification was carried out employing a 20 kWe commercial gasification system with macadamia nut shell, bagasse, and rice straw. Subsequently, post-gasification residues were meticulously collected, analyzed and utilized for CO2 adsorption experiments. Among these residual chars, macadamia nut shell demonstrated the highest CO2 adsorption capacity, followed by bagasse, while rice straw showed moderate performance. In laboratory conditions (25 °C, 1 bar, without the influence of ambient moisture or CO2 diffusion constraint), the post-gasification residue from macadamia nut shell achieved a CO2 adsorption capacity of 2.8 mmol g−1, followed by bagasse (2.4 mmol g−1). Transitioning to more practical conditions (25 °C, 1 bar, considering the influence of ambient moisture and CO2 diffusion limitations within an adsorbent bed), the macadamia nut shell and bagasse residual chars reached 2.7 mmol g−1 and 2.3 mmol g−1, respectively. Moreover, these chars exhibited noteworthy CO2/N2 selectivity and recyclability, making them comparable to various advanced CO2 adsorbents investigated in prior studies. The superior performance of the macadamia nut shell-derived residual char can be attributed to its highest microporous/ultra-microporous volumes and concentrations of basic and aromatic functional groups on the char's surface. The results of this study open up the potential for different strategies in combining the production of energy and affordable and upscalable CO2 adsorbents for industrial applications.

DOI： 10.1016/j.tsep.2024.102446

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Synergistic effect of the heterojunction g-C<inf>3</inf>N<inf>4</inf>/Bi<inf>2</inf>MoO<inf>6</inf>/clinoptilolite to enhance the photocatalytic degradation of antibiotics in water in the presence of persulfate 査読有り

Le P.T., Nguyen T.P., Do T.H., Nguyen H.N., Dinh T.M.T., Phan T.T., Tsubota T., Nguyen T.D.

Environmental Science: Water Research and Technology 2024年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

A novel and highly efficient photocatalyst, g-C3N4/Bi2MoO6/clinoptilolite nanocomposite (CNBC), was synthesized by a hydrothermal method and acted as a Z-scheme heterojunction for efficient activation of peroxydisulfate (PDS) to degrade oxytetracycline (OTC) under visible light (vis) irradiation. The morphology and structure of the photocatalyst were determined by XRD, FT-IR, FE-SEM, EDX, BET, TGA, UV-vis DRS, PL, and XPS. The results showed that CNBC-30 had the best photocatalytic performance with an OTC removal efficiency of more than 87% within 120 min under the conditions of [OTC] = 20 mg L−1, [catalyst] = 500 mg L−1, [Na2S2O8] = 1.26 mM, and pH = 4 at room temperature, which was much better than those of pure g-C3N4, Bi2MoO6, and CNB composites. This superiority is due to the excellent adsorption ability of clinoptilolite that effectively forms the g-C3N4/Bi2MoO6 heterojunctions, thus improving the ability to separate charge carriers while decreasing the recombination rate of electron-hole pairs. Furthermore, the effect of catalyst dosage, oxidant concentration, initial pollutant concentration, solution pH, and coexisting anions on the OTC degradation was comprehensively studied. The results showed that the CNBC-30/PDS system had high reusability and adaptability at different pH levels (3.0-11.0). Quenching tests showed that 1O2, O2˙−, and h+ played the main roles in OTC degradation. In addition, OTC intermediates were identified and degradation pathways were proposed based on the results of MS analysis. DFT calculations successfully predicted the positions on the OTC molecule with high Fukui numbers that are suitable for attack by oxidants. CNBC-30 was stable for OTC degradation after four cycles with a degradation efficiency of above 78%, demonstrating its durability and potential for practical applications. This study provides insight into PDS activation in the visible light region by a clinoptilolite-based Z-scheme heterojunction for organic pollutant degradation.

DOI： 10.1039/d4ew00549j

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Europium removal from aqueous solutions by oxidized biochar prepared from waste palm tree fronds 査読有り国際誌

Georgiou E., Ioannidis I., Pashalidis I., Viet D.D., Tsubota T., Kalderis D.

Sustainable Chemistry for the Environment 4 2023年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Palm oil is a product of major economic importance worldwide however, palm tree cultivation generates large quantities of palm fronds as waste. In this work, the sorption of Eu3+ from aqueous solutions by oxidized biochar derived from palm tree fronds was studied at pH 3 by batch type experiments under ambient conditions. Following biochar production, the sample was oxidized using HNO3 to increase the oxygen-containing moieties on its surface. The oxidized biochar was characterized through surface and spectroscopic techniques. As indicated by the coefficient of determination value of 0.99, Eu3+ adsorption was best described by the Langmuir isotherm model. The optimum adsorption capacity was determined at qmax= 0.81 mol kg−1. Adsorption was an entropy-driven process and followed the 2nd order kinetics, reaching a plateau value of 50% relative adsorption within 60 min. Furthermore, Fourier Transform InfraRed spectroscopic data and the effect of ionic strength indicated that adsorption proceeded via the development of inner-sphere complexes between Eu3+ and the carboxylic groups on the biochar surface.

DOI： 10.1016/j.scenv.2023.100040

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Effect of solvent and acid catalyst selection on lignin recovery and purity in autoclave-assisted organosolv extraction 査読有り国際誌

Farid M.A.A., Ibrahim I., Lease J., Tsubota T., Andou Y.

Bioresource Technology Reports 24 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

This study leverages the autoclave-assisted method to explore a range of acid catalysts (H2SO4, HCl, HNO3, H3PO4) and solvents (methanol, ethanol, acetone, 2-butanol, 2-propanol) for lignin extraction, with a focus on identifying optimal efficiency-enhancing combinations. By contrasting the performance of various acid catalysts and solvents, this work transcends previous efforts in this field. Notably, H2SO4 yields the highest lignin recovery (44.7 %) but with lower purity (78.4 %) compared to HCl (85.7 %) in the same solvent. Methanol yields the highest recovery (45.1 %), yet lower purity (79.2 %) than ethanol (85.7 %) with a similar catalyst. A pivotal improvement lies in the elucidation of structural purity, substantiated by IR and NMR resulting signals, supported by microscale morphology and chemical composition (SEM-EDX). This study extends current understanding, providing profound insights into optimizing extraction procedures for producing lignin with desired attributes.

DOI： 10.1016/j.biteb.2023.101622

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Use of the Wise method as a pretreatment for the selective removal of lignin when preparing bamboo-activated carbon 査読有り国際誌

Tsubota T., Khuong D.A., Nagaoka H., Kumagai S., Andou Y.

Advances in Bamboo Science 5 2023年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The Wise method, which is known in wood science as a technique for the quantitative analysis of holocellulose, was applied as a pre-treatment to prepare a porous precursor for activated carbon. The precursor has a specific pore size structure derived from the organizational architecture of the natural plant. The lignin in the plant tissue of the bamboo was successfully removed in a stepwise fashion by the Wise method treatment. All the N2 adsorption isotherms at 77 K for the carbonized samples, including the samples treated by the Wise method, were similar in shape. Specifically, they were type I as classified by IUPAC with low-pressure hysteresis, and there was no specific effect of the selective removal of lignin from the carbonized sample. However, after CO2 activation for more than 2 h, samples treated with the Wise method had slit pores, which is type H4 as classified by IUPAC. The slit width calculated by the INNES method, which is the theory for slit-type mesopores, was ca. 2.5 nm. When samples delignified by more than 60% were activated by CO2 for 3 h, the percentage of the micropores in the total pores was ca. 40%. Samples treated by the Wise method for the stepwise selective removal of lignin, should enable pore structure derived from plant tissue to be controlled in the activated carbon.

DOI： 10.1016/j.bamboo.2023.100049

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Supercapacitors composed of Japanese cedar bark-based activated carbons with various activators 査読有り国際誌

Trinh K.T., Tsubota T.

Materials Chemistry and Physics 307 2023年10月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

This study provided an overview of how pore structures and functional groups influence the electrochemical behaviors of activated carbons derived from a new type of biomass waste - Japanese cedar bark (JCB) with four different activators, i.e., KOH, K2CO3, H3PO4, and ZnCl2. Based on the chemical composition, microstructure, gas adsorption isotherms, and electrochemical analytical techniques, relationships between the pore structures, functional groups, and electrochemical behavior of the activated samples were assessed. The K2CO3 and KOH activated materials, designated KC-6 and KO-6, respectively, with an activation ratio of 6 (6 g an activator/1 g of JCB), were well rated for their electrochemical capabilities. At 10 mA g−1, these two samples had a specific capacitance of roughly 210 F g−1. The high electrochemical potential of KC-6 was attributed to a particular hierarchical structure comprised of micro-meso-macropores and rich oxygen functional groups on its surface, allowing faster ion diffusion and more effective ion adsorptions. Furthermore, in the case of the 1 M H2SO4 electrolyte, KO-6 had the largest specific surface area of 3000 cm2 g−1 and appropriate micropores (diameters (d) < 1.2 nm) for the electrolyte ion adsorptions, thus allowing this model to maintain an 80% specific capacitance for approximately 6500 Cyclic Voltammetry cycles at 1 mV s−1. The pore properties, functional groups, and electrochemical properties of the activated material derived from JCB can be controlled to some extent by the activator selections and experimental conditions.

DOI： 10.1016/j.matchemphys.2023.128148

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The production of high-value products derived from bamboo by steam pretreatment: Sugar-contained water solution and solid residue as a precursor for EDLC electrode 査読有り国際誌

Khuong D.A., Saza S., Tsubota T.

Materials Chemistry and Physics 304 2023年08月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, the effect of steam treatment on bamboo in several conditions was comprehensively investigated. The sugar-contained water derived from bamboo could be extracted by the proper condition of steaming time and temperature. The highest amount of sugar content was 1.9oBx, found at the steaming condition of 200 °C and 2.5 h. The raw bamboo and the solid residue after steam treatment were converted into porous carbon by KOH activation. By the N2 adsorption/desorption isotherm analysis, the textural structures of activated carbons in the research were determined as the dominated-microporous structure. The BET specific area of activated carbon derived from the solid residue was up to 3445 m2 g−1. The microporous structure stimulated by KOH activation helped enhance the electrical performance of the carbon electrode for EDLC. Based on the electrochemical measurements, the capacitances of the samples derived from the solid residue were higher than that derived from bamboo. The results suggested that the steaming process was an effective pretreatment to take full advantage of the properties of bamboo.

DOI： 10.1016/j.matchemphys.2023.127853

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Catalytic graphitization of biomass-derived ethanosolv lignin using Fe, Co, Ni, and Zn: Microstructural and chemical characterization 査読有り国際誌

Farid M.A.A., Zheng A.L.T., Tsubota T., Andou Y.

Journal of Analytical and Applied Pyrolysis 173 2023年08月

記述言語：英語掲載種別：研究論文（学術雑誌）

Bamboo has just recently emerged as a sustainable source of lignin extraction, paving the way for the development of sophisticated nano- and biomaterials based on lignin. Catalytic pyrolysis effectively synthesized graphitic carbon from biomass resources. This article investigates the influence of various metals (Fe, Co, Ni, and Zn) as catalysts in the catalytic graphitization of bamboo biomass-derived lignin. The graphitization process was carried out through thermal treatments conducted in a tightly closed muffle furnace at 1100 ℃ for a duration of 4 hrs. The metals-catalyzed graphitic carbons appeared flake-like microstructures under SEM with > 80 wt% graphitized carbon composition detected by XPS. Enhancement in the degree of graphitization, crystallite size, interlayer distance, and structural order was achieved within the order of Fe>Co>Ni>Zn. These are corroborated by XRD, indicating Fe-catalyst resulted in lignin graphite with a degree of graphitization of 92.07%, crystallite size (Lc) of 230.2 nm, and interlayer distances of 0.336 nm that are closer to commercial graphite. Raman revealed the Fe-catalysed lignin graphite has a lower defective ratio (ID/IG) of 0.55, while all graphitized lignin showed IG/I2D of > 1.0, indicating multiple layers of graphitic carbon. These findings might pave the way for future high-value graphite-based materials made from low-cost biomass, making it an intriguing prospect.

DOI： 10.1016/j.jaap.2023.106064

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Recycling marine plastic waste to energy storage devices 査読有り国際誌

Tashima D., Kashio T., Eguchi T., Kumagai S., Tsubota T., Madden J.D.W.

Materials Letters: X 18 2023年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, a method was developed for the management of marine plastic waste via the production of activated carbon. The specific surface area, micropore volume, and mesopore volume of marine-plastic-based activated carbon prepared at selected temperatures and using selected activator weight ratios were measured, and the specific capacitance and supercapacitor electrode performance were evaluated. At an activation temperature of 800 °C and a raw material to 8 M KOH weight ratio of 1:7, a specific capacitance of 201F/g and a high surface area of 2389 m2/g were obtained. Therefore, marine plastic waste-based activated carbon can be used as the electrode material in supercapacitors.

DOI： 10.1016/j.mlblux.2023.100193

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Bamboo-derived adsorbents for environmental remediation: A review of recent progress 査読有り国際誌

Kalderis D., Seifi A., Kieu Trang T., Tsubota T., Anastopoulos I., Manariotis I., Pashalidis I., Khataee A.

Environmental Research 224 2023年05月

記述言語：英語掲載種別：研究論文（学術雑誌）

The bamboo family of plants is one of the fastest-growing species in the world. As such, there is an abundance of bamboo residues available for exploitation, especially in southeast Asian, central African and south American regions. The preparation of efficient adsorbents from bamboo residues is an emerging exploitation pathway. Biochars, activated carbons or raw bamboo fibers embedded with nanoparticles, each class of materials has been shown to be highly efficient in adsorption processes. This review aims to summarize recent findings in the application of bamboo-based adsorbents in the removal of organic, inorganic, or gaseous pollutants. Therefore, this review first discusses the preparation methods and surface modification methodologies and their effects on the adsorbent elemental content and other basic properties. The following sections assess the recent progress in the adsorption of heavy metals, organics, and gaseous substances by bamboo-based adsorbents, focusing on the optimum adsorption capacities, adsorption mechanisms and the optimum-fitting kinetic models and isotherms. Finally, research gaps were identified and directions for future research are proposed.

DOI： 10.1016/j.envres.2023.115533

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Characterization of the Electromagnetic Shielding Effectiveness of Biochar-Based Materials 査読有り

Nikolopoulos C.D., Baklezos A.T., Kapetanakis T.N., Vardiambasis I.O., Tsubota T., Kalderis D.

IEEE Access 11 6413 - 6420 2023年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Biochar and biochar-based composites are multi-functional materials with a wide range of environmental and other applications. A new and emerging application is in the field of modern communication systems as materials with significant electromagnetic shielding effectiveness. In this study, biochar was prepared from olive tree prunings which was subsequently used at various dosages to prepare composite samples with carbon black and polytetrafluoroethylene as binder. The electromagnetic shielding effectiveness of the samples were measured in the frequency range of 1-3 GHz, using a simple, user-friendly and reliable experimental set-up. The results showed that raw, unmodified biochar had a low shielding effectiveness in the range of 1.5-4 dB however, it slightly increased as the thickness of the sample increased from 0.1 to 0.5 mm. Modifying biochar with the 20 %w/w acetylene black largely increased its shielding effectiveness, reaching the value of 39 dB in the same frequency range. Our approach demonstrated that raw biochar can be used as a substrate to develop composite materials with significant shielding effectiveness and assess their performance with a quick and simple laboratory method.

DOI： 10.1109/ACCESS.2023.3237327

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Adsorption characteristics of ciprofloxacin and naproxen from aqueous solution using bamboo biochar 査読有り国際誌

Pham T.D., Nguyen D.T., Nguyen H.L., Nguyen M.Q., Tran T.M., Nguyen M.V., Nguyen T.L., Ngo T.M.V., Namakamura K., Tsubota T.

Biomass Conversion and Biorefinery 2023年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Adsorption of the drugs ciprofloxacin (CFX) and naproxen (NPX) using bamboo biochar was systematically investigated. Bamboo biochar was characterized by SEM, TEM, FT-IR, BET, and ζ measurement. Bamboo biochar has a porous structure with high specific surface area and contains carboxyl groups with negative charge. Batch adsorption of CFX on bamboo biochar was optimal at pH 4, 7.5 g/L adsorbent dosage, and adsorbed in 90 min while the best conditions for NPX adsorption were pH 3, with 10 g/L and contact time 90 min. Adsorption isotherms of CFX and NPX on bamboo biochar surface at different ionic strengths were achieved with Freundlich better than Langmuir. Adsorption of CFX and NPX on bamboo biochar is controlled by electrostatic and non-electrostatics, while NPX adsorption is mainly controlled by electrostatic interactions. The CFX and NPX removal efficiencies were still greater than 60% after four regenerations, indicating that bamboo biochar is an excellent adsorbent for pharmaceutical contaminants removal in water. Graphical abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s13399-023-05092-x

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Glycerol-Based Retrievable Heterogeneous Catalysts for Single-Pot Esterification of Palm Fatty Acid Distillate to Biodiesel 査読有り国際誌

Hazmi B., Beygisangchin M., Rashid U., Mokhtar W.N.A.W., Tsubota T., Alsalme A., Ngamcharussrivichai C.

Molecules 27 ( 20 ) 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

The by-product of the previous transesterification, glycerol was utilised as an acid catalyst precursor for biodiesel production. The crude glycerol was treated through the sulfonation method with sulfuric acid and chlorosulfonic acid in a reflux batch reactor giving solid glycerol-SO3H and glycerol-ClSO3H, respectively. The synthesised acidic glycerol catalysts were characterised by various analytical techniques such as thermalgravimetric analyser (TGA), infrared spectroscopy, surface properties adsorption-desorption by nitrogen gas, ammonia-temperature programmed desorption (NH3-TPD), X-ray diffraction spectroscopy (XRD), elemental composition analysis by energy dispersive spectrometer (EDX) and surface micrographic morphologies by field emission electron microscope (FESEM). Both glycerol-SO3H and glycerol-ClSO3H samples exhibited mesoporous structures with a low surface area of 8.85 mm2/g and 4.71 mm2/g, respectively, supported by the microscopic image of blockage pores. However, the acidity strength for both catalysts was recorded at 3.43 mmol/g and 3.96 mmol/g, which is sufficient for catalysing PFAD biodiesel at the highest yield. The catalytic esterification was optimised at 96.7% and 98.2% with 3 wt.% of catalyst loading, 18:1 of methanol-PFAD molar ratio, 120 °C, and 4 h of reaction. Catalyst reusability was sustained up to 3 reaction cycles due to catalyst deactivation, and the insight investigation of spent catalysts was also performed.

DOI： 10.3390/molecules27207142

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Environmentally Safe Magnetic Nanocatalyst for the Production of Biodiesel from Pongamia pinnata Oil 査読有り国際誌

Sami H.Q.u.A., Hanif M.A., Rashid U., Nisar S., Bhatti I.A., Rokhum S.L., Tsubota T., Alsalme A.

Catalysts 12 ( 10 ) 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Biodiesel is an alternative fuel in many developing and developed countries worldwide. Biodiesel has significant and numerous economic, environmental, and social benefits. However, the problem with conventional biodiesel production is the high industrial production cost, mainly contributed by the raw materials. Therefore, catalysts and feedstock are essential in increasing total biodiesel production rates and minimizing production costs. Magnetic nano-catalysts play a crucial role in heterogeneous catalysis due to their easy recovery, recyclability, excellent selectivity, and fast reaction rates, owing to their larger surface area. This research activity used heterogeneous magnetic nano-catalysts of ICdO, ISnO, and their modified form, to produce biodiesel. The synthesized nano-catalysts were made through co-precipitation and found quite efficient for transesterifying Pongamia pinnata oil. The effect of various parameters on biodiesel yield in the presence of prepared magnetic nano-catalysts has been studied. In the transesterification supported by ISnO, high yield, i.e., 99%, was achieved after 2 h of reaction time at 60 °C. The nano-catalysts were magnetically recovered and reused 4–5 times without any change in their activity. All the synthesized magnetic nano-catalysts performed SEM analysis. Each fraction of the produced biodiesel was assessed for different quality parameters, and the results were per ASTM standards. The components present in biodiesel produced from Pongamia pinnata oil were determined by GCMS.

DOI： 10.3390/catal12101266

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A Heterogeneous Bifunctional Carbon Nanocatalyst from Plastic Waste to Efficiently Catalyze Waste Cooking Oil into Biodiesel 査読有り国際誌

Hazmi B., Rashid U., Kawi S., Mokhtar W.N.A.W., Ahangar F.A., Yaw T.C.S., Tsubota T., Alharthi F.A., Ngamcharussrivichai C.

Catalysts 12 ( 8 ) 2022年08月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, black carbon derived from polyethylene terephthalate (PET) wastes was utilized as the precursor for heterogeneous bifunctional nanocatalyst, which successively catalyzed waste cooking oil into biodiesel. The nano-sized catalysts were prepared by impregnation method with different heat treatment techniques, such as reflux, hydrothermal, and microwave solvothermal, to provide good distribution of K2O and NiO particles on PET activated carbon mesoporous surface. The sample treated with microwave solvothermal technique (MAC-K2O-NiO) exhibited a high surface area of 120 m2/g with good dispersion of nanoparticles, as shown by FESEM image, large crystallite size of 62.2 nm, and consisted of a highest density of basicity (2.58 mmol/g) and acidity (1.79 mmol/g) for improving transesterification to a maximum yield. The catalytic transesterification of MAC-K2O-NiO was optimized with 3 wt.% of catalyst loading, 18: 1 methanol-oil molar ratio, 65 °C for 3 h of reaction, with a maximum yield of 97.2%. The catalyst reusability was performed, and it was found to maintain the catalytic activity up to six reaction cycles, with a yield of 72.9%. The physiochemical quality of the optimized biodiesel was examined in accordance with the American Society for Testing and Materials, ASTM D6751 testing method.

DOI： 10.3390/catal12080874

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Comparison of consecutive impacts of wood and rice husk gasification biochars with nitrogen fertilizer on soybean yield 査読有り国際誌

Hien T.T.T., Tsubota T., Taniguchi T., Shinogi Y.

Paddy and Water Environment 20 ( 3 ) 303 - 313 2022年07月

記述言語：英語掲載種別：研究論文（学術雑誌）

Demand for gasification biochar is expected to increase, owing to the bioenergy requirements of a sustainable society. Here, we assessed the applicability of gasification biochars from cedar wood (W) and rice husk (R) for the agricultural soil amendment and compared their ability in enhancing soybean yield in two consecutive cropping cycles. The pot experiment included four treatments: F0 (control 1), without both nitrogen fertilizer (Nfer) and biochar, F (control 2), using only Nfer, W–F, using W with Nfer, and R–F, using R with Nfer. Both gasification biochars had higher pH, CEC, and greater nitrogen retention than the soil. In the first cropping cycle, the W application showed an immense impact on some soil physical properties, including bulk density reduction (12%) and water-holding capacity increment (25%) while the R amendment significantly increased exchangeable K (45%) and soil pH. In addition, other changes in soil chemical due to W and R applications included enhancement of available phosphorus (P, 8–14%) and reduction of ammonium content (12–21%). After two consecutive cropping cycles, W–F indicated the largest content of soil available P and the highest soil pH. Ultimately, the co-application with Nfer of W and R had the same significant impact on soybean yield compared with control 1 in the first and two consecutive cropping cycles. In addition, the W application specifically recorded a significantly higher soybean yield than control 2 in the first and two cropping cycles, unlike the R amendment.

DOI： 10.1007/s10333-021-00875-2

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Numerical analysis of the micropore structure of activated carbons focusing on optimum CO<inf>2</inf> adsorption 査読有り国際誌

Kwiatkowski M., Kalderis D., Tono W., Tsubota T.

Journal of CO2 Utilization 60 2022年06月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In this work, the porous structure of activated carbons prepared from Moso bamboo were mathematically analysed. At first, the raw material was subjected to two-stage activation process i.e. in the first stage, phosphoric acid or zinc chloride was used followed by second stage physical activation or chemical activation with potassium hydroxide. Then, nitrogen and carbon dioxide adsorption isotherms were determined. Subsequently, a novel, clustering-based adsorption analysis method was applied, combined with a numerical procedure for the fast multivariant identification of adsorption systems. The mentioned method takes into consideration the heterogeneity of the adsorbent surface and allows the determination of the adsorption energy as well as the shape and size of the clusters of adsorbate molecules formed in the pores of the analysed material. Additionally, the Quenched Solid Density Functional Theory was selected to determine the cumulative pore volume, pore size distributions and other micropore parameters. The analyses revealed a considerable degree of complexity of the carbons’ porous structure, including differences in the adsorption of CO2 and N2. The complementarity of the applied methods leads to the reliable determination of the optimum activated carbon for CO2 adsorption and assists reverse engineering approaches in the production and activation stage.

DOI： 10.1016/j.jcou.2022.101996

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Towards sustainable biomass gasification: Evolution of bagasse char characteristics throughout gasification 査読有り国際誌

Nguyen H.N., Khuong D.A., Tran-Nguyen P.L., Tsubota T.

Biomass and Bioenergy 158 2022年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

The development of a sustainable bagasse gasification system using bagasse as feedstock could be realized if a complete understanding of bagasse gasification was established. In this study, the evolution of the char characteristics throughout the gasification process was deeply investigated. The low ash content, high heating value, and fast char conversion rate highlighted the suitability of bagasse for gasification. The char morphology underwent significant changes with rupture of beehive-like structures that make up the char when conversion X [0, 1] is higher than 0.5. On the contrary, changes in carbon structures were observed more clearly at the beginning of char conversion (X < 0.5). The gasified chars had high porosity made of micro-mesoporous structures, and the maximum value of total specific surface area (SBET = 877 m2 g−1) and total pore volume (VBET = 0.49 cm3 g−1) were observed at X = 0.75. The high values of SBET and VBET - even when gasification is nearing its end - highlighted the potential of using residues after gasification as an alternative to expensive commercial activated carbons. The results of this study would contribute to forming solutions for some challenges for the industrialization of biomass gasification, such as the formation of soot and tar, or the treatment/reuse of post-gasification residues.

DOI： 10.1016/j.biombioe.2022.106384

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Thermal induced changes of rice straw phytolith in relation to arsenic release: A perspective of rice straw arsenic under open burning 査読有り国際誌

Nguyen M.N., Nguyen A.T.Q., Dultz S., Tsubota T., Duong L.T., Nguyen A.M., Pham N.T.T.

Journal of Environmental Management 304 2022年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

On-site open burning is a common practice for handling rice straw, but its negative impacts, e.g., biomass loss and air pollution, are largely debated worldwide. To address the negative effects of open burning, many efforts have been made to ‘ignite’ worldwide bans. However, these bans are likely based on a singular view in which some positive aspects of open burning are overlooked. In this study, we aimed to determine the thermal-induced changes of straw and straw arsenic (As) under open burning and heat-treatments (in the temperature range from 300 to 900 °C). It was found that silica phase in rice straw (so-called phytolith) can encapsulate As in its structure. Open burning or heat-treatment of straw resulted in a tighter association of As and phytolith, thereby reducing dissolution of As. We proposed an opinion that open burning causes air pollution, but it can increase the activity of phytolith in sequestrating As, enabling delayed As cycle in rice ecosystems. The combat of on-site open burning of rice straw to reduce air pollution will alter straw handling routines, thereby changing the cycle of straw phytolith and the route of straw As.

DOI： 10.1016/j.jenvman.2021.114294

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Potential heterogeneous nano-catalyst via integrating hydrothermal carbonization for biodiesel production using waste cooking oil 査読有り国際誌

Abdullah R.F., Rashid U., Hazmi B., Ibrahim M.L., Tsubota T., Alharthi F.A.

Chemosphere 286 2022年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Hydrothermal carbonization (HTC) provides alternatives technique to produce a nanosize activated carbon from biomass with a high surface area. Herein, this study we prepared empty fruit bunch-based activated carbon (EFBHAC) using HTC technique. The activated carbon was then functionalized with K2CO3 and Cu(NO3)2 to produce bifunctional nano-catalyst for simultaneous esterification-transesterification of waste cooking oil (WCO). The physicochemical properties were performed i.e. N2 sorptions analysis, TPD-CO2/NH3, FESEM, EDX, FTIR and XRD analysis. The results revealed that produced EFBHAC possessed a BET surface area of 4056.17 m2 g−1, with pore volume of 0.827 cm3 g−1 and 5.42 nm of pore diameter resulting from hydrolysis, dehydration decarboxylation, aromatization and re-condensation during HTC process. Impregnation of EFBHAC with K2CO3 and Cu(NO3)2 granted a high amount of basicity and acidity of 9.21 mmol g−1 and 31.41 mmol g−1, respectively, accountable to high biodiesel yield of 97.1%, produced at the optimum condition of 5 wt% of catalyst loading, 12:1 of methanol to oil molar ratio at 70 °C for 2 h. More than 80% of biodiesel was produced after the 5th cycle depicted the good reusability. The transformations from WCO to biodiesel was confirmed via 1H NMR, FTIR and TGA analysis. Fuel properties revealed kinematic viscosity of 3.3 mm2 s−1, cetane number of 51, flash point of 160.5 °C, cloud and pour point of 11 °C and −3 °C, respectively. These results show the excellent potential of waste materials to prepare bifunctional nano-catalysts to produce higher biodiesel yield which has potential to be commercialized.

DOI： 10.1016/j.chemosphere.2021.131913

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Low-cost novel nano-constructed granite composites for removal of hazardous Terasil dye from wastewater 査読有り国際誌

Khalil M., Hanif M.A., Rashid U., Ahmad J., Alsalme A., Tsubota T.

Environmental Science and Pollution Research 30 ( 34 ) 81333 - 81351 2022年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

The hazardous dyes on mixing with water resources are affecting many life forms. Granite stone is popular worldwide for decorating floors, making other forms of decorative materials and items. Granite stone powder waste can be obtained free of cost from marble factories as factories spend on the disposal of this waste. In the present study, novel granite stone powder waste composite has been prepared and utilized for the effective removal of Terasil dye. Two types of granite including gray granite and white granite were used in pure, calcinized, and chemically modified forms. Freundlich adsorption isotherm model best explained the adsorption mechanism of dye removal using granite composites as compared to other adsorption isothermal models. Characterization techniques like scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used for the determination of morphological features and functional groups of granite composites. The obtained results were statistically analyzed using analysis of variance (ANOVA) along with the post hoc Tukey test. An extraordinarily high Terasil dye uptake capacity (more than 400 mg/g) was exhibited by granite composites prepared using sodium metasilicate. The synthesized novel nano-constructed composites provided a viable strategy as compared to the pure granite stone for dye removal from wastewater water. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s11356-022-21367-8

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Physicochemical Properties of Waste Palm-Based Catalysts Synthesized from Pyrolyzed and Hydrothermalized Chars for Biodiesel Production 査読有り国際誌

Rashid U., Hazmi B., Abdullah R.F., Ibrahim S.F., Alsalme A., Tsubota T.

Topics in Catalysis 66 ( 9-12 ) 723 - 739 2022年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Carbon precursor derived from biomass waste gained significant interest as a component of heterogeneous catalysts that can be functionalized with active groups and provides the advantage of separating the catalyst from reactant and products, unlike common homogeneous catalyst. In this study, palm kernel shell (PKS) based char was developed by pyrolysis and hydrothermal carbonization methods and subsequently utilized for synthesizing bifunctional carbon catalyst. The wet impregnation method by loading K2CO3 and CuO provided bi-functional characteristics to the produced chars for conversion into efficient catalysts, which were suitable for concurrent esterification and transesterification processes. The prepared catalysts were characterized by BET, XRD, FESEM, FTIR, TGA, and CO2/NH3 TPD analysis. The report showed that the sample of hydrothermal-assisted carbonization (HTC) treatment possessed higher surface area (4056 m2/g) due to the steady degradation of lignocellulosic composition, thus improving the porous quality of carbon structure compared to normal pyrolytic carbon (2658 m2/g). Additionally, the PKSHAC@K2CO3-CuO catalyst sample embraced more potent acid-basic properties than PKSAC@K2CO3-CuO, yielding 98.4% and 96.7% of FAME respectively, at optimized reaction conditions, the temperature of 65 °C for 3 h, with 15:1 molar ratio of methanol to WCO with 3 wt% of catalysts loading.The reusability test showed that PKSHAC@K2CO3-CuO could catalyse up to 80.1% of FAME, while PKSAC@K2CO3-CuO recorded a yield of 60.1%. The biodiesel from waste cooking oil was analyzed to meet the ASTM D6751 standard for diesel fuel. The synthesized heterogeneous catalysts using different chars might be widely suitable for low-cost oil feedstocks used for biodiesel production. Graphical Abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s11244-022-01736-w

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Dependence of pore structure of activated carbon on the performance of electrical double layer capacitor with NaCl aqueous electrolyte 査読有り国際誌

Onodera H., Tsubota T.

Journal of Porous Materials 30 ( 4 ) 1101 - 1108 2022年01月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, electric double layer capacitors (EDLC) were fabricated as laminate type by using NaCl aqueous solution, which should be relatively safe electrolyte against environments and biological objects, for the investigation of the performance from a practical point of view. The capacitance value of the cell depended on the kind of activated carbon used as electrodes. The capacitance values of the EDLCs fabricated from the best activated carbon were ca. 38 F g− 1 at 0.36 mA cm− 2 of discharging current value and at 1.2 V of charging voltage. The capacitance value should be equivalent to commercial EDLCs although the charging voltage is smaller. The relationship between the properties related to pores of activated carbon and the capacitance value was examined. The enumerated values obtained from the Dubinin-Astakhov (DA) method for the activated carbons of this study were between 1 and 2, which could indicate that the micropore distribution of the activated carbons used in this study was heterogeneous. The capacitance value was found to be strongly related to the micropore volume calculated by the DA method from the adsorption isotherm of CO2 at 298 K. That is, the micropore volume estimated from the DA method should be used as the indicator for the selection of high-performance activated carbon for electrode of EDLC containing NaCl aqueous solution electrolyte.

DOI： 10.1007/s10934-022-01407-x

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Evolution of physico-chemical properties of Dicranopteris linearis-derived activated carbon under various physical activation atmospheres 査読有り

Mai N.T., Nguyen M.N., Tsubota T., Nguyen P.L.T., Nguyen N.H.

Scientific Reports 11 ( 1 ) 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

This work emphasizes the effect of the physical activation using CO2 and steam agents on the physicochemical properties of activated carbon produced from Dicranopteris linearis (D. linearis), a fern species widely distributed across tropic and subtropic ecoregions. The D. linearis-derived chars produced under pyrolysis at 400 °C for 1 h were activated in various CO2-steam proportions. As revealed by the IR and Raman spectra, the structure of the activated chars was heavily dependent on the relative proportion of CO2 and steam. The total specific surface area (SSA) of the activated chars proportionally increased with the increase in steam proportion and was comparable to the values of commercial activated char products. Specifically, the activation under CO2− and steam-saturated conditions has correspondingly resulted in SSA increasing from 89 to 653 m2g−1 and from 89 to 1015 m2g−1. Steam also enhanced the development of mesoporous structures of the D. linearis-derived char products, thereby extending their potential applications, particularly for industries that require high rigidity in the product such as pharmaceutical and cosmetic sectors.

DOI： 10.1038/s41598-021-93934-x

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Fungicide application can intensify clay aggregation and exacerbate copper accumulation in citrus soils 査読有り

Dao T.T., Tran T.T.T., Nguyen A.M., Nguyen L.N., Pham P.T.M., Tsubota T., Nguyen M.N.

Environmental Pollution 288 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Fungicide application for controlling fungal diseases can increase copper (Cu) accumulation in soil. More urgently, Cu released from fungicides can associate with soil clay and favour the mutual aggregation of Cu and soil clay, thereby potentially intensifying the accumulation of Cu. We investigated the effects of Cu salt and six common Cu-based fungicides on colloidal dynamics of a clay fraction from citrus cultivated soil. Batch experiments were carried out to provide the loading capacity of the clay fraction for Cu. The colloidal dynamic experiments were performed over a pH range from 3 to 8 following a test tube method, while surface charge, the key electrochemical factor of the solid-liquid interface, was quantified by a particle charge detector. It was found that all the studied fungicides, via releasing Cu2+, acted to effectively favour clay aggregation. The dissolved organic matter obtained from the dissolution of polymers in fungicides can theoretically stimulate clay dispersion. However, their effects were obscured due to the overwhelming effect of Cu2+. Therefore, Cu2+ appears as the most active agent in the fungicides that intensifies clay aggregation. These findings imply that the intensive application of fungicides for plant protection purposes can inadvertently reduce clay mobility, favour the co-aggregation of clay and fungicides, and hence potentially exacerbate the contamination of the citrus soil.

DOI： 10.1016/j.envpol.2021.117703

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Conversion of waste polyethylene terephthalate (Pet) polymer into activated carbon and its feasibility to produce green fuel 査読有り

Ahangar F.A., Rashid U., Ahmad J., Tsubota T., Alsalme A.

Polymers 13 ( 22 ) 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, a novel idea was proposed to convert the polyethylene terephthalate (PET) waste drinking-water bottles into activated carbon (AC) to use for waste cooking oil (WCO) and palm fatty acid distillate (PFAD) feasibility to convert into esters. The acidic and basic char were prepared by using the waste PET bottles. The physiochemical properties were determined by employing various analytical techniques, such as field emission scanning electron microscopy (FESEM), thermo-gravimetric analysis (TGA), Fourier transform infrared (FTIR), Brunauer–Emmett–Teller (BET) and temperature-programmed desorption – ammonia/carbon dioxide (TPD-NH3 /CO2 ). The prepared PET H3 PO4 and PET KOH showed the higher surface area, thus illustrating that the surface of both materials has enough space for impregnation of foreign precursors. The TPD-NH3 and TPD-CO2 results depicted that PET H3 PO4 is found to have higher acidity, i.e., 18.17 mmolg−1, due to the attachment of phosponyl groups to it during pretreatment, whereas, in the case of PET KOH, the basicity increases to 13.49 mmolg−1 . The conversion results show that prepared materials can be used as a support for an acidic and basic catalyst for the conversion of WCO and PFAD into green fuel.

DOI： 10.3390/polym13223952

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Assessment of biochar produced by flame-curtain pyrolysis as a precursor for the development of an efficient electric double-layer capacitor 査読有り

Tsubota T., Tsuchiya S., Kusumoto T., Kalderis D.

Energies 14 ( 22 ) 2021年11月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Pine tree biochar produced by flame-curtain pyrolysis, an inexpensive and simple pyrolysis methodology, was used as the starting material for KOH-activated carbon. Flame-curtain pyrolysis is a simple, low-technology methodology that can be performed by non-specialized personnel. The elemental analysis of the biochars highlighted the high reproducibility of the process. The N2 adsorption isotherms indicated that KOH activation was effective for the preparation of high-surfacearea activated carbons from the biochar. The BET specific surface area increased with the quantity of KOH added in the activation process, achieving a maximum value of 3014 m2 g−1 at 85.7 wt.% of KOH addition. The adsorption isotherms of all samples were IUPAC type I, establishing their microporous nature. Results from the Mikhail–Brunauer (MP) method and αs plot indicated that the pore size distribution became wider and the pore volume increased as the KOH content increased. The measured capacitance values followed the same dependence on KOH content. The maximum capacitance value at 1 mV s−1 was determined as 200.6 F g−1 for the sample prepared at 75 wt.% of KOH addition. Therefore, pine tree biochar prepared by simple pyrolysis equipment is a suitable precursor for the development of an electric double-layer capacitor.

DOI： 10.3390/en14227671

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An easily fabricated palladium nanocatalyst on magnetic biochar for Suzuki-Miyaura and aryl halide cyanation reactions 査読有り

Turunç E., Akay S., Baran T., Kalderis D., Tsubota T., Kayan B.

New Journal of Chemistry 45 ( 28 ) 12519 - 12527 2021年07月

記述言語：英語掲載種別：研究論文（学術雑誌）

Biochar is a carbon-rich solid, the surface of which is covered with a high density of functional carbonyl, hydroxyl and carboxylic acid groups. In this work, palladium nanoparticles were embedded on magnetic biochar and a new reusable and environmentally-friendly catalyst was developed and applied for the promotion of Suzuki-Miyaura C-C coupling and cyanation reactions. The high-carbon (77%), low-ash content (5.8%) and the relatively high surface area (266 m2g−1) of pine tree biochar (PTB) suggested that it might be highly suitable as a catalyst substrate. The Fe3O4-Pd-biochar nanocomposite was successfully characterized using SEM, TEM, EDX, FT-IR, BET and XRD. Its catalytic role was initially evaluated usingp-NO2C6H4I as a model reactant (for both types of reactions) and later for the production of biaryls and benzonitriles from a wide range of aryl halides under mild reaction conditions. Biaryls and benzonitriles were characterized using GC-MS. In the case of the Suzuki-Miyaura reaction, the optimum yield of 98% was obtained with a catalyst concentration of 0.04 mol%, microwave irradiation of 400 W, and a residence time of 5 min, using K2CO3as the base. With respect to the cyanation reaction, dimethylformamide, Na2CO3and 6 h were the optimum solvent, base and reaction duration, respectively. Subsequently, the nanocatalyst showed excellent catalytic activity in both reactions, achieving >88% yields in most cases, regardless of the aryl iodide or bromide used and the type of substitution.

DOI： 10.1039/d1nj00941a

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Towards engineered hydrochars: Application of artificial neural networks in the hydrothermal carbonization of sewage sludge 査読有り

Kapetanakis T.N., Vardiambasis I.O., Nikolopoulos C.D., Konstantaras A.I., Trang T.K., Khuong D.A., Tsubota T., Keyikoglu R., Khataee A., Kalderis D.

Energies 14 ( 11 ) 2021年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

Sewage sludge hydrochars (SSHs), which are produced by hydrothermal carbonization (HTC), offer a high calorific value to be applied as a biofuel. However, HTC is a complex processand the properties of the resulting product depend heavily on the process conditions and feedstock composition. In this work, we have applied artificial neural networks (ANNs) to contribute to the production of tailored SSHs for a specific application and with optimum properties. We collected data from the published literature covering the years 2014–2021, which was then fed into different ANN models where the input data (HTC temperature, process time, and the elemental content of hydrochars) were used to predict output parameters ((higher heating value, (HHV) and solid yield (%)). The proposed ANN models were successful in accurately predicting both HHV and contents of C and H. While the model NN1 (based on C, H, O content) exhibited HHV predicting performance with R2 = 0.974, another model, NN2, was also able to predict HHV with R2 = 0.936 using only C and H as input. Moreover, the inverse model of NN3 (based on H, O content, and HHV) could predict C content with an R2 of 0.939.

DOI： 10.3390/en14113000

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Correction to: Enhancing soil water holding capacity and provision of a potassium source via optimization of the pyrolysis of bamboo biochar (Biochar, (2021), 3, 1, (1-3), 10.1007/s42773-020-00075-x) 査読有り

Hien T.T.T., Tsubota T., Taniguchi T., Shinogi Y.

Biochar 3 ( 1 ) 2021年03月

Enhancing soil water holding capacity and provision of a potassium source via optimization of the pyrolysis of bamboo biochar 査読有り

Hien T.T.T., Tsubota T., Taniguchi T., Shinogi Y.

Biochar 3 ( 1 ) 51 - 61 2021年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

Rapid expansion of cultivated bamboo negatively impacts on biodiversity and soil microbial community. As such, it is important to properly manage and use bamboo to prevent and control such issues. This study focuses on optimizing pyrolysis conditions to produce bamboo biochar for agricultural soil amendment, particularly soil potassium (K) and water holding capacity. Bamboo chips were pyrolyzed under nitrogen gas at 400, 600, and 800 °C for 1 and 2 h of retention. A total of six biochar products were created: 400-1 (i.e., 400 °C in 1 h), 400-2, 600-1, 600-2, 800-1, and 800-2. The 600 °C bamboo biochar products were observed to have the greatest potential in increasing soil K and water holding capacity. The 600-1 product had the highest potassium content (4.87%), with a water holding capacity of 3.73 g g−1, while the 600-2 product had the second-highest potassium content (4.13%) and the highest water holding capacity (4.21 g g−1) and cation exchange capacity. The K release in 600 °C products was larger and slower than that of the 400 °C and 800 °C products, respectively. The results also indicated that the physicochemical characteristics of bamboo biochar, such as yield, pH, surface area, water holding capacity, and K content, were significantly impacted by temperature, retention time, or a combination of these parameters. The outcomes from this study are a valuable reference for bamboo biochar production targeting agricultural soil amendment, particularly when it is directed at increasing soil K and water holding capacity.

DOI： 10.1007/s42773-020-00071-1

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Surface Functionalization of Biochar from Oil Palm Empty Fruit Bunch through Hydrothermal Process 査読有り国際誌

Izzudin Ibrahim, Toshiki Tsubota, Mohd Ali Hassan, Yoshito Andou

Processes 9 ( 1 ) 1 - 14 2021年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

The use of biochar as an adsorbent for wastewater treatment purposes has been hindered due to its lower surface area compared to activated carbon. Current research on increasing surface functional groups on biochar surfaces to improve its adsorption performance suggests using high chemical concentration and long period of modification. This study solves these problems by focusing on improving surface functionalities of biochar via the hydrothermal functionalization process. Oil palm empty fruit bunch biochar was functionalized using autoclave with nitric acid as the functionalization agent. Functionalized biochar properties such as Brunauer–Emmett–Teller (BET) surface area and surface functional groups were analyzed and compared with untreated biochar. Fourier Transform Infrared (FTIR) spectroscopic analysis shows a significant increase in absorption by oxygen functional groups and is corroborated with energy dispersive X-ray (EDX) analysis. The process does not result in any major change in surface morphology and reduction in surface area value. Methylene blue (MB) adsorption test shows 7 times increase in adsorption performance. These results show that the simple hydrothermal functionalization process successfully functionalizes the biochar surface and improves its performance without affecting its surface area at lower concentration, and shorter time compared to previous studies. This result, with future large-scale experimentation using real-life equipment in palm oil mills, would provide a better technology that can be implemented in the industry.

DOI： 10.3390/pr9010149

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Carbonization and H<inf>3</inf>PO<inf>4</inf> activation of fern Dicranopteris linearis and electrochemical properties for electric double layer capacitor electrode 査読有り国際誌

Trinh T.K., Tsubota T., Takahashi S., Mai N.T., Nguyen M.N., Nguyen N.H.

Scientific Reports 10 ( 1 ) 2020年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Today, the world’s climate change is a growing problem, plant carbon sequestration is one of the effective ways to mitigate climate change by reducing greenhouse gases, mostly carbon gases. Dicranopteris linearis (D. linearis), a common fern species in the tropic or subtropic ecoregions, has been recently recognized as a potential feedstock to produce highly porous biochar. This study aims to enhance the specific surface area (SSA) and pore volumes of biochars derived from the D. linearis by H PO activation and examine electrical properties of the activated biochars and their possible usage for the electric double-layer capacitor (EDLC) electrode. The treated raw fern was activated with H PO 85% by the three different mixing ratios 1:0, 1:1, and 1:3 (w/w) and then pyrolysis under N flow maintained at 500 °C for 1 h. The performance as the electrode for an EDLC was evaluated in 1 mol L H SO solution for the H PO -activated samples. The SSA and pore volumes were drastically increased after activation. The maximum SSA and pore volume were 1212 m g and 1.43 cm g , respectively for the biochar activated at 400 °C with a weight mixing ratio 1:3 (w/w) between the fern and H PO acid while these values of the biochar at 400 °C were 12 m g and 0.02 cm g , respectively. The biochar activated at 600 °C with the mixing ratio 1:1 (w/w) showed the maximum capacitance value, ca. 108 F g at 1 mV s . The activation using H PO showed a positive tendency to enhance electrochemical properties and it could be a premise toward a higher performance of EDLC from the D. linearis derived activated biochar. 3 4 3 4 2 2 4 3 4 3 4 3 4 −1 2 −1 3 −1 2 −1 3 −1 −1 −1

DOI： 10.1038/s41598-020-77099-7

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Kinetic and structural changes during gasification of cashew nut shell char particles 査読有り国際誌

Hong Nam Nguyen, Duy Anh Khuong, Thi Thu Ha Vu, Thi Nga Mai, Toshiki Tsubota, Van Bay Tran, Joel Blin, Laurent Van De Steene

Environmental Progress and Sustainable Energy ( Environmental Progress and Sustainable Energy ) 40 ( 3 ) 2020年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Cashew Nut Shell (CNS), an abundant waste from the cashew nut production, could become a promising material for gasification. Nevertheless, engineering data regarding this technology is still small and fragmented. In this study, the evolution of the char textural properties during gasification, as well as the effect of operating conditions on char gasification kinetics were extensively investigated and quantified. The textural properties of cashew nut shell char changed significantly following different pathways between CO2 and H2O gasification. Micropores and mesopores were well developed along with the conversion in the case of H2O gasification instead of only micropores in the case of CO2 gasification. Regarding char gasification kinetics, an increase of the temperature from 800 to 1000°C enhanced five times the conversion rate under an H2O atmosphere and 15 times under a CO2 atmosphere. The conversion rate increased two times when the concentration of reacting gases changed from 20 to 60 vol % for both atmospheres. Similarities in terms of gasification kinetics between CNS chars and wood chip chars were found in this range of operating conditions.

DOI： 10.1002/ep.13580

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Hydrochars as emerging biofuels: Recent advances and application of artificial neural networks for the prediction of heating values 査読有り国際誌

Vardiambasis I.O., Kapetanakis T.N., Nikolopoulos C.D., Trang T.K., Tsubota T., Keyikoglu R., Khataee A., Kalderis D.

Energies 13 ( 17 ) 2020年09月

記述言語：英語掲載種別：記事・総説・解説・論説等（学術雑誌）

In this study, the growing scientific field of alternative biofuels was examined, with respect to hydrochars produced from renewable biomasses. Hydrochars are the solid products of hydrothermal carbonization (HTC) and their properties depend on the initial biomass and the temperature and duration of treatment. The basic (Scopus) and advanced (Citespace) analysis of literature showed that this is a dynamic research area, with several sub-fields of intense activity. The focus of researchers on sewage sludge and food waste as hydrochar precursors was highlighted and reviewed. It was established that hydrochars have improved behavior as fuels compared to these feedstocks. Food waste can be particularly useful in co-hydrothermal carbonization with ash-rich materials. In the case of sewage sludge, simultaneous P recovery from the HTC wastewater may add more value to the process. For both feedstocks, results from large-scale HTC are practically non-existent. Following the review, related data from the years 2014-2020 were retrieved and fitted into four different artificial neural networks (ANNs). Based on the elemental content, HTC temperature and time (as inputs), the higher heating values (HHVs) and yields (as outputs) could be successfully predicted, regardless of original biomass used for hydrochar production. ANN3 (based on C, O, H content, and HTC temperature) showed the optimum HHV predicting performance (R2 0.917, root mean square error 1.124), however, hydrochars' HHVs could also be satisfactorily predicted by the C content alone (ANN1, R2 0.897, root mean square error 1.289).

DOI： 10.3390/en13174572

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Complete Parametric Study of Bagasse Pellets during High-Temperature Steam Gasification 査読有り

Nguyen H.N., Tsubota T.

Journal of Thermal Science and Engineering Applications 12 ( 4 ) 2020年08月

記述言語：英語掲載種別：研究論文（学術雑誌）

A complete parametric study of bagasse pellets under high-temperature steam gasification in relevant industrial operating conditions was investigated. Regarding thermal behaviors, the maximum rate of weight loss (Rmax = 0.55%/°C) occurred at the temperature Tmax = 305 °C. The final pyrolysis temperature and heating rate were proportional to the mechanical strength, the bulk density, as well as the char yield and energy yield. However, the changes were not significant after 600 °C. Regarding steam gasification kinetics, an increase from 850 to 1000 °C and from 0.1 to 0.4 atm accelerated 10 times and two times the conversion rate of bagasse pellet char, respectively. Gasification kinetics of a pellet char produced at 2000 °Cmin-1 was 1.4 higher compared with a pellet char produced at 5 °C min-1. An empirical model that takes into account all the changes in the reactive surface could successfully predict the conversion of the bagasse pellet char during high-temperature steam gasification. Experimental results and the kinetic model proposed could be useful for the calculation of industrial or academic codes, necessary for the conception of new efficient gasifiers.

DOI： 10.1115/1.4045698

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Humidity adsorption characteristics of Moso bamboo charcoal oxidized at room temperature by HNO<inf>3</inf> 査読有り国際誌

Viet D.D., Tsubota T., Shinogi Y.

Journal of the Indian Academy of Wood Science 17 ( 1 ) 34 - 41 2020年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020, Indian Academy of Wood Science. The bamboo charcoals (BC) in various range pyrolysis (400–900 °C) were modified by HNO3, and then the samples were tested for water vapor adsorption. The adsorption experiments were conducted follows to Japanese industrial standard JIS A 1470-1-2002. The physical and chemical properties of the samples were studied by scanning electron microscope, Brunauer–Emmett–Teller surface area analysis, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The humidity adsorption tests show that the modified BC samples with HNO3 at room temperature (about 22 °C) in pyrolysis temperature (400–500 °C) have a significant enhancement than the control one at lower relative humidity (< 60%). This characteristic is an advantageous application in conservation needs extremely low humidity. Specific surface area and total pore volume are supposed to play an important role for humidity adsorption at high relative humidity (> 60%). Whereas, at low relative humidity, surface functional groups on BC are a dominant factor compared to specific surface area on humidity adsorption.

DOI： 10.1007/s13196-019-00251-y

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Release kinetics of potassium from silica-rich fern-derived biochars 査読有り国際誌

Nguyen A.T.Q., Bui T.A., Mai N.T., Tran H.T., Tran S.V., Nguyen N.H., Tsubota T., Shinogi Y., Dultz S., Nguyen M.N.

Agronomy Journal 112 ( 3 ) 1713 - 1725 2020年05月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 The Authors. Agronomy Journal © 2020 American Society of Agronomy Recently, low input agriculture has been encouraged because of its sustainability and environmentally friendly vision. Conversion of biomass into control-released materials is one of the approaches to upcycle biomass and nutrients. This study aims at examining the dynamics of K release from Si-rich biochars formed from various pyrolysis strategies with the findings expected to be applicable to develop new refinery strategies for biomass nutrients. A Si-rich fern species [Dicranopteris linearis (Burm.f.) Underw.] was selected to prepare biochars under various pyrolysis conditions (e.g., temperature, N2 supported). It was found that K was re-located during pyrolysis and occurred as free K+ ions, associated with organic matter and occluded in silica structure. Pyrolysis can be strategically applied to alter either the organic phase or the silica phase in the biochars in term of porosity and chemical reactivities, whereby controlling K release kinetics. The maximum level of released K was at 600 °C (5.4 g kg−1) which was about one order of magnitude higher than the minimum level of released K at 200 °C (0.55 g kg−1). This discrepancy in the release rates of K suggests that adjusting pyrolysis temperature can be a strategical practice to control K release and to develop biochar-based K fertilizers.

DOI： 10.1002/agj2.20209

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KOH activation of solid residue of Japanese citron after extraction by microwave process and property as EDLC electrode 査読有り

Tsubota T., Hohshi Y., Ohno T., Kumagai S.

Journal of Porous Materials 27 ( 3 ) 727 - 734 2020年01月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. The solid residue of Japanese citron after its compression to obtain juice and then the extraction of oil was used as the raw material of activated carbon in order to substantiate the cascading use of Citrease for several high value products. Most of the inorganic compounds in the carbonized samples were K4H2(CO3)3·1.5 H2O and CaCO3. Although the amount of these inorganic compounds was independent of the carbonization temperature, most of these inorganic compounds were removed by the KOH activation process. The BET specific surface area of the sample after the KOH activation increased with the increasing amount of KOH added for activation, and the value was greater than 1900 m2 g−1 when the amount of KOH was greater than 67 wt%. The pore sizes and pore volumes were calculated by several methods, such as the Langmuir, t method, αs method, MP method, BJH method, and INNES method, in order to analyze in detail the surface condition related to the pores. The capacitance value of the sample activated at KOH 75 wt% was 157 F g−1 at 1 mV s−1.

DOI： 10.1007/s10934-019-00855-2

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Fern Dicranopteris linearis-derived biochars: Adjusting surface properties by direct processing of the silica phase 査読有り

Mai N.T., Nguyen N.H., Tsubota T., Shinogi Y., Dultz S., Nguyen M.N.

Colloids and Surfaces A: Physicochemical and Engineering Aspects 583 2019年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 Elsevier B.V. This work specifically emphasizes the effect of the silica phase contained in the fern Dicranopteris linearis (D. linearis), a common shrub occurring widely throughout tropical and subtropical regions, on biochar surface properties. Slow pyrolysis was performed in the temperature range from 400 to 900 °C under various ambient reaction conditions, i.e., non-biochar-oriented conditions (open pyrolysis) and biochar-oriented conditions (closed and N2-supported pyrolysis). The resulting changes in micromorphology and different surface properties, specific surface area and surface charge, were elucidated. Open pyrolysis resulted in excessive decomposition of biomass and condensation of silica, while the closed and N2-supported pyrolysis methods showed notable enhancement of biochar yield. The presence of silica as an inter-embedded part of the fern D. linearis and the derived biochars likely supported a carbon-silica structural model in which these two components might be integrated or decomposed during pyrolysis. In general, joint processing of organic carbon and silica greatly altered the surface properties. At lower temperatures and during N2-supported pyrolysis, condensation of organic compounds limited the development of high surface charge densities. At higher temperatures and during open pyrolysis, intensification of the silica phase was accompanied with an increasing number of charged surface sites, thereby increasing the surface charge density. Based on the porous structure, large surface area (up to 701 m2 g−1) and high surface charge density (up to 0.5 μmol(−) m−2), D. linearis-derived biochars can be highlighted as potential agro-environmental materials.

DOI： 10.1016/j.colsurfa.2019.123937

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Preparation of Porous Carbon Material Derived from Cellulose with Added Melamine Sulfate and Electrochemical Performance as EDLC Electrode 査読有り

Tsubota T., Maguchi Y., Ishimoto K., Katamune Y., Kamimura S., Ohno T.

Journal of Electronic Materials 48 ( 2 ) 879 - 886 2019年02月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018, The Minerals, Metals & Materials Society. Activated carbon derived from cellulose with added melamine sulfate, which is known as one of the chemicals having a flame-retardant effect on the cellulose, was produced in order to dope dual hetero elements, such as nitrogen and sulfur, and was used to improve the yields of the carbonization process and carbon dioxide (CO 2 ) activation process. The addition of melamine sulfate resulted in suppression of the BET specific surface area. The Brunauer–Emmett–Teller (BET) specific surface area for the CO 2 -activated sample with 30 wt.%-added melamine sulfate was 578 m 2 g −1 . The existence of nitrogen atoms was confirmed in the CO 2 -activated sample with the added melamine sulfate. However, no peak assigned to the sulfur atom appeared in the x-ray photoelectron spectroscopy spectrum for the sample with the 30 wt.%-added melamine sulfate. In spite of the lower specific surface area of the samples containing the added melamine sulfate, the capacitance values of the carbon material derived from the cellulose with added melamine sulfate were higher than those of the carbon material derived only from cellulose.

DOI： 10.1007/s11664-018-6799-z

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Cascade use of bamboo as raw material for several high value products: production of xylo-oligosaccharide and activated carbon for EDLC electrode from bamboo 査読有り

Tsubota T., Ishimoto K., Kumagai S., Kamimura S., Ohno T.

Journal of Porous Materials 25 ( 5 ) 1541 - 1549 2018年10月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The cascade use of bamboo as the raw material for high-value products, that is, the production of xylo-oligosaccharide and the preparation of activated carbon for EDLC electrode, was proposed as an economically effective use of bamboo in this study. Xylo-oligosaccharides, such as xylobiose and xylotriose, were successfully produced from bamboo in a water solution by a hot compressed water process. The solid residue of bamboo after the treatment of the hot compressed water was carbonized at 400–800 °C, then activated with KOH. The KOH activation was effective for the preparation of activated carbon having a high BET specific surface area of ca. 2600 m g from the solid residue. The amount of ash drastically decreased by the hot compressed water treatment, which should be an advantage as the precursor for EDLC electrodes. The capacitance values measured in a 1 M H SO aqueous solution of the activated carbon derived from the solid residue compared well with those from the bamboo. 2 −1 2 4

DOI： 10.1007/s10934-018-0567-6

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Photoelectrochemical synthesis of aniline from nitrobenzene in a neutral aqueous solution by using a p-type Cu<inf>2</inf>ZnSnS<inf>4</inf>electrode 査読有り国際誌

Kamimura S., Kubo Y., Tsubota T., Ohno T.

Applied Catalysis B: Environmental 225 445 - 451 2018年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 We fabricated a CZTS electrode by the sol-gel and spin-coating method on an Mo/glass substrate and performed photoelectrochemical (PEC) reduction of nitrobenzene (NB) in an aqueous environment under visible light irradiation (420 < λ < 800 nm). By using the CZTS electrode, a six-electron reduction reaction of NB to aniline (AN) proceeded in an aqueous solution under visible light irradiation. We found that NB reduction reaction was strongly dependent on the electrode potential; large cathodic polarization is kinetically favorable for hydrogen evolution over a CZTS electrode, which leads to hindrance of the PEC NB reduction reaction, resulting in a decrease in the yield of AN ( < 20%). At small cathodic polarization, conversion of NB reached to > 99% and the yield of AN was calculated to be > 50%. Moreover, we found that the proton concentration in an aqueous electrolyte had a significant effect on the PEC NB reduction reaction. In this study, we investigated the PEC NB reduction reaction over a CZTS electrode in conjunction with the structural and optical properties.

DOI： 10.1016/j.apcatb.2017.12.021

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Solar-driven H<inf>2</inf>evolution over CuNb<inf>2</inf>O<inf>6</inf>: Effect of two polymorphs (monoclinic and orthorhombic) on optical property and photocatalytic activity 査読有り国際誌

Kamimura S., Abe S., Tsubota T., Ohno T.

Journal of Photochemistry and Photobiology A: Chemistry 356 263 - 271 2018年04月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 We synthesized two different polymorphs (monoclinic and orthorhombic phases) of CuNb 2 O 6 as a d 0 –d 9 photocatalyst by a solid-state reaction route and performed photocatalytic H 2 evolution from water under AM 1.5G solar light irradiation. The monoclinic phase (P21/c) was transformed to the orthorhombic phase (Pcna) at ambient temperature ( > 700 °C), and XRD data revealed that the direct environment of octahedral sites was occupied by Cu 2+ cations. The difference in the local crystal structure of the CuO 6 octahedral in the two polymorphs of CuNb 2 O 6 was closely related to the optical absorption property. For monoclinic CuNb 2 O 6 , the optical band gap transition was a metal-to-metal charge transfer between Cu 2+ and Nb 5+ , and d-d absorption of Cu 2+ was a forbidden transition by the Laporte selection rule due to its symmetric CuO 6 octahedral. For orthorhombic CuNb 2 O 6 , d-d absorption of Cu 2+ was partially allowed because of its distorted CuO 6 octahedral. We experimentally revealed that d-d absorption of Cu 2+ contributed a significant effect on the photocatalytic activity of both polymorphs of CuNb 2 O 6 ; the photocatalytic activity of the monoclinic phase was insensitive to d-d transition in Cu 2+ ions, while the photocatalytic activity of the orthorhombic phase was strongly influenced by d-d transition in Cu 2+ ions because an electron configuration as d 9 readily induces structural distortion by Jahn-Teller effects in an octahedral crystal field. The distortion was avoided by trapping photo-generated electrons, leading to a decrease in photocatalytic activity. We discuss the photocatalytic activities of both polymorphs of CuNb 2 O 6 in conjunction with structural, optical and electrochemical properties. We also show that a deposition of platinum nanoparticles on CuNb 2 O 6 further improved the photocatalytic activity.

DOI： 10.1016/j.jphotochem.2017.12.039

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P-57 水熱処理によるイナワラからのフルフラール製造査読有り

井上誠一, 熊谷聡, 坪田敏樹

バイオマス科学会議発表論文集 ( 一般社団法人日本エネルギー学会 ) 13 ( 0 ) 159 - 160 2018年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

<p>Rice straw was treated under hydrothermal condition for producing furfural, which is one of the degradation products of hemicellulose. The highest furfural yield (19.6 mg/g-rice straw) was obtained at 220°C for 15min under hydrothermal condition. Main product was furfural, but the other oxygenated compounds, such as acetic acid and formic acid, were also obtained at this condition. When the phosphoric acid solution was added to the compressed water, the yield of furfural increased remarkably, and the highest yield (26.0 mg/g-rice straw) of the furfural was obtained at 220 °C for 15min. It is shown that addition of phosphoric acid solution to the compressed water provided the higher yield to obtain the furfural from rice straw.</p>

DOI： 10.20550/jiebiomassronbun.13.0_159

Performance as electrode of electrical double layer capacitor of activated carbon prepared from bamboo using guanidine phosphate and CO<inf>2</inf> activation 査読有り国際誌

Tsubota T., Morita M., Kamimura S., Ohno T.

Journal of Porous Materials 24 ( 6 ) 1507 - 1512 2017年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017, Springer Science+Business Media New York. The electrochemical performances of an electrical double layer capacitor were investigated regarding the activated carbon prepared from bamboo by a new approach, that is, the combination of delignification, addition of guanidine phosphate, and CO 2 activation. In this study, a 1 M H 2 SO 4 aqueous solution was used as the electrolyte of the capacitor. The physical properties, such as the BET specific surface area of the carbon material, depend on the preparation conditions of the activated carbon. A TEM image indicated that the addition of guanidine phosphate did not facilitate the graphitization and did not prevent activation by CO 2 . The apparent reaction equation for the CO 2 activation was first-order, which is reasonable for physical activation. The electrochemical performances of the carbon material depended on the preparation conditions of the carbon material, such as the heat treatment temperature, amount of added guanidine phosphate, and CO 2 activation time. The sample prepared under the following conditions (the amount of added guanidine phosphate: 9 wt%, the heat treatment temperature: 800 °C, CO 2 activation time: 3 h) had the highest performance (153 F g −1 at 1000 mA g −1 ) because the sample had the highest BET specific surface area (2001 m 2 g −1 ).

DOI： 10.1007/s10934-017-0390-5

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Platinum and indium sulfide-modified Cu<inf>3</inf>BiS<inf>3</inf>photocathode for photoelectrochemical hydrogen evolution 査読有り国際誌

Kamimura S., Beppu N., Sasaki Y., Tsubota T., Ohno T.

Journal of Materials Chemistry A 5 ( 21 ) 10450 - 10456 2017年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 The Royal Society of Chemistry. A polycrystalline Cu 3 BiS 3 film as a photoelectrode was fabricated by an electrodeposition method on a molybdenum-coated glass substrate for photoelectrochemical hydrogen evolution. The Cu 3 BiS 3 film was composed of dense crystallites with thicknesses of ca. 0.65 μm, and the optical bandgap was estimated to be ca. 1.6 eV. Photoelectrochemical characterization revealed that the Cu 3 BiS 3 film was a p-type semiconductor with a flat band potential of ca. +0.1 V (vs. Ag/AgCl at pH 6), which is suitable for water reduction but cannot be used for water oxidation. Deposition of an In 2 S 3 buffer layer, by which effective contact between p-type Cu 3 BiS 3 and n-type In 2 S 3 was formed, resulted in a significant increase in the photocurrent and a large shift of the photocurrent onset to the positive region. H 2 evolution under AM 1.5G simulated solar light was demonstrated using the Pt-In 2 S 3 /Cu 3 BiS 3 electrode combined with a Pt electrode under an applied bias (0 V vs. RHE).

DOI： 10.1039/c7ta02740k

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P-67 竹のカスケード利用によるキシロオリゴ糖の製造と電気二重層キャパシタ電極用炭素材料の開発査読有り

坪田敏樹, 石本航太郎, 熊谷聡, 林信行

バイオマス科学会議発表論文集 ( 一般社団法人日本エネルギー学会 ) 12 ( 0 ) 183 - 184 2017年01月

担当区分：筆頭著者記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

<p>In order to use bamboo as the starting material for some high-value products, the production of carbon material, which is activated carbon, for the electrode of electric double layer capacitor (EDLC) was attempted from the bamboo residue after the compressed hot water treatment, which can produce xylo-oligosaccharide from bamboo. The bamboo powder after the treatment of 200 degrees C for 1 hour was used as the starting material of carbon material. The yield from the residue to activated carbon was ca. 10 % regardless of the carbonization temperature. The estimated specific surface areas by BET method for the prepared samples were ca. 2500 m2/g, except for the sample carbonized at 800 degrees C. The capacitance values of the samples were small at high current density. The reason for the small values should be large IR drop.</p>

DOI： 10.20550/jiebiomassronbun.12.0_183

Partial delignification as pretreatment for nanoporous carbon material from biomass 査読有り国際誌

Tsubota T., Nagata D., Kamimura S., Ohno T.

Journal of Nanoscience and Nanotechnology 17 ( 1 ) 815 - 820 2017年01月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

For the pretreatment in order to nano prepare porous carbon from biomass such as bamboo, a mixture of acetic acid and hydrogen peroxide was used for the partial delignification of bamboo. The pretreatment should be effective for the removal of lignin because the lignin percentage after the pretreatment depended on the treatment time and the treatment temperature. For the concentration of the mixture used for the pretreatment in this study, a small amount of lignin (ca. 2 wt%) remained even after a sufficiently-long treatment time. The BET specific surface area of the carbon material prepared by the heat treatment at 800 degrees C for 1 h under flowing N2 was related to the pretreatment conditions, and the specific surface areas of the samples were found to be related to the lignin percentage. The removal of lignin while maintaining the microstructure derived from plant tissue could be the reason for the local maximum of the specific surface area at ca. 5%of the lignin.

DOI： 10.1166/jnn.2017.12534

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Photoelectrochemical CO<inf>2</inf>reduction by a p-type boron-doped g-C<inf>3</inf>N<inf>4</inf>electrode under visible light 査読有り国際誌

Sagara N., Kamimura S., Tsubota T., Ohno T.

Applied Catalysis B: Environmental 192 193 - 198 2016年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2016 Elsevier B.V. Graphitic carbon nitride (g-C 3 N 4 ) has attracted much attention as a metal-free semiconductor having visible light absorption and relatively high chemical stability under visible light irradiation. Graphitic carbon nitride (g-C 3 N 4 ) and boron-doped g-C 3 N 4 (B-doped g-C 3 N 4 , BCNx) were prepared by heating melamine and a mixture of dicyanodiamide and BH 3 NH 3 , respectively. X-ray diffraction, a Brunauer, Emmett and Teller (BET) apparatus, and UV-vis spectra were used to analyze the physical properties of the prepared samples . Electrodes of these samples were prepared by using the electrophoresis method. X-ray photoelectron spectroscopy analyses confirmed the incorporation of boron atoms in the g-C 3 N 4 framework as well as the amount of boron atoms.Au, Ag or Rh as a co-catalyst was coated on the surface of g-C 3 N 4 and B-doped g-C 3 N 4 by using the magnetron sputtering method. The photocurrent response was observed using a solar simulator as a light source. The photocurrent response of B-doped g-C 3 N 4 was about 5-times larger than that of pure g-C 3 N 4 . B-doped g-C 3 N 4 coated with Rh as a co-catalyst showed the highest photocurrent response under solar light irradiation, its photocurrent being about 10-times larger than that of original g-C 3 N 4 . Under photoelectrochemical conditions, we also observed the products in gas phase and aqueous phase. C 2 H 5 OH was observed as a main product, while small amounts of CO and H 2 were observed in gas phase. We also discuss the relationship between co-catalysts and photocurrent responses and the carbon source of C 2 H 5 OH as a main product. The source of carbon of C 2 H 5 OH obtained by CO 2 reduction is discussed on the basis of results of a labeling experiment using 13 CO 2 .

DOI： 10.1016/j.apcatb.2016.03.055

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(Au@Ag)@Au double shell nanoparticles loaded on rutile TiO<inf>2</inf>for photocatalytic decomposition of 2-propanol under visible light irradiation 査読有り国際誌

Kamimura S., Miyazaki T., Zhang M., Li Y., Tsubota T., Ohno T.

Applied Catalysis B: Environmental 180 255 - 262 2016年07月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2015 Elsevier B.V. We synthesized (core@shell)@shell ((Au@Ag)@Au) nanoparticles (NPs) by a multistep citrate reduction method for utilization as photosensitizers of TiO 2 . The (Au@Ag)@Au NPs exhibited strong photoabsorption in visible light response due to LSPR excitation of the Ag shell, and its LSPR characteristics were stable under visible light irradiation for a long time because oxidation of the Ag shell was prevented by the outermost Au shell. Furthermore, we successfully loaded (Au@Ag)@Au NPs on rutile TiO 2 by an impregnation method. (Au@Ag)@Au/TiO 2 could oxidize 2-propanol into acetone and CO 2 under visible light irradiation (λ > 440nm), and its acetone evolution rate was approximately 15-times higher than that of Au/TiO 2 . From a comparison of action spectra for acetone evolution and the Kubelka-Munk function, it was confirmed that photocatalytic activity of (Au@Ag)@Au/TiO 2 was induced by photoabsorption based on LSPR excitation of the Ag shell. In addition, photoelectrochemical measurements revealed electron injection from LSPR-excited (Au@Ag)@Au NPs into TiO 2 under visible light irradiation. We proposed the photocatalytic reaction process of (Au@Ag)@Au/TiO 2 in conjunction with optical, structural and photoelectrochemical properties.

DOI： 10.1016/j.apcatb.2015.06.037

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Improvement of selectivity for CO<inf>2</inf>reduction by using Cu<inf>2</inf>ZnSnS<inf>4</inf>electrodes modified with different buffer layers (CdS and In<inf>2</inf>S<inf>3</inf>) under visible light irradiation 査読有り国際誌

Kamimura S., Sasaki Y., Kanaya M., Tsubota T., Ohno T.

RSC Advances 6 ( 113 ) 112594 - 112601 2016年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

© The Royal Society of Chemistry. Cu 2 ZnSnS 4 (CZTS) electrodes modified with different n-type buffer layers (CdS and In 2 S 3 ) were used as photocathodes for CO 2 reduction under visible light irradiation (420 < λ < 800 nm) in aqueous media. Compared to a bare CZTS electrode, CZTS electrodes modified with n-type buffer layers (CdS and In 2 S 3 ), by which a p-n heterojunction between CZTS and the n-type buffer layer is formed, showed a significant increase in the photocurrent assigned to CO 2 reduction. In addition, product selectivity of CO 2 reduction was improved by surface modification with an n-type buffer layer: that is, selective CO 2 reduction into CO was achieved by using a CdS/CZTS electrode, while HCOOH selectivity was observed over an In 2 S 3 /CZTS electrode. In this study, we investigated the photoelectrochemical properties of CZTS electrodes modified with n-type buffer layers (CdS and In 2 S 3 ) in conjunction with the structural and optical properties, and we investigated their activity for PEC CO 2 reduction.

DOI： 10.1039/c6ra22546b

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Photocatalytic reduction of CO<inf>2</inf>over exposed-crystal-face-controlled TiO<inf>2</inf>nanorod having a brookite phase with co-catalyst loading 査読有り

Ohno T., Higo T., Murakami N., Saito H., Zhang Q., Yang Y., Tsubota T.

Applied Catalysis B: Environmental 152-153 ( 1 ) 309 - 316 2014年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photocatalytic reduction of carbon dioxide (CO 2 ) was carried out using exposed-crystal- face-controlled titanium(IV) oxide (TiO 2 ) having a brookite phase. Methanol (CH 3 OH) was detected as the main product, and trace amounts of formic acid, carbon monoxide, methane, and hydrogen were also detected in some cases. The prepared nanorod-shaped brookite TiO 2 with large {210} and small {212} exposed crystal faces showed larger CH 3 OH generation than that of commercial brookite TiO 2 powder (Kojundo Chemical Laboratory Co., Ltd.). The activity of a brookite TiO 2 nanorod for CO 2 reduction depended on its aspect ratio because the {210} crystal faced worked as a reduction site, whereas an oxidation site was assigned to {212} crystal faces. Photodeposition of gold (Au) or silver (Ag) nanoparticles on the nanorod-shaped brookite TiO 2 induced a dramatic increase in CH 3 OH production because the deposited metal particles work as reductive sites for multi-electron reduction of CO 2 . Among the co-catalyst-loaded brookite TiO 2 nanorods, nanorod-shaped brookite TiO 2 loaded with Ag showed higher activity. The source of carbon of CH 3 OH obtained by CO 2 reduction is discussed on the basis of results of a labeling experiment using 13 CO 2 . © 2014 Elsevier B.V.

DOI： 10.1016/j.apcatb.2014.01.048

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Complete oxidation of acetaldehyde over a composite photocatalyst of graphitic carbon nitride and tungsten(VI) oxide under visible-light irradiation 査読有り

Jin Z., Murakami N., Tsubota T., Ohno T.

Applied Catalysis B: Environmental 150-151 479 - 485 2014年05月

記述言語：英語掲載種別：研究論文（学術雑誌）

Graphitic carbon nitride (g-C 3 N 4 ) was prepared by heating melamine and then its specific surface area was enlarged by hydrothermal treatment in aqueous sodium hydroxide solution. The g-C 3 N 4 samples were blended with tungsten(VI) oxide (WO 3 ) using a planetary mill in order to improve photocatalytic activity. The composite photocatalyst with optimized amounts of these contents showed higher photocatalytic activity for decomposition of acetaldehyde under visible-light irradiation than did original samples. From the results, we concluded that the composite photocatalyst utilizes both high oxidation ability of WO 3 and high reduction ability of g-C 3 N 4 by Z-scheme charge transfer. © 2014 Elsevier B.V.

DOI： 10.1016/j.apcatb.2013.12.048

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Synthesis of nanofibrous carbon with herringbone structure on Ni-supported SiC particles using hot CVD apparatus 査読有り

Tsubota T., Matsuo H., Murakami N., Ohno T., Yajima H.

Diamond and Related Materials 48 104 - 109 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

A nanofibrous carbon material having a herringbone structure was synthesized using Ni-supported silicon carbide (SiC) particles as the catalyst for the hot chemical vapor deposition (CVD) process using CH 4 as carbon source. The amount of the deposits during the CVD process strongly depended on the CVD treatment temperature. The enhancement of weight and the TG data indicated that the quantity synthesis of the deposits was achieved at 823 K. The specific surface area of the deposits was estimated at ca. 120 m 2 g - 1 . It was confirmed from the TEM images that the deposits synthesized in this study had a herringbone-like structure. From the data of Raman spectra and XRD patterns, the herringbone-like structure started to deposit after 30 minutes in the case of 823 K. The Ni-supported SiC can be used as the catalyst for the synthesis of nanofibrous carbon materials. © 2014 Elsevier B.V.

DOI： 10.1016/j.diamond.2014.07.009

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Photocatalytic reduction of carbon dioxide over shape-controlled titanium(IV) oxide nanoparticles with co-catalyst loading 査読有り

Murakami N., Saruwatari D., Tsubota T., Ohno T.

Current Organic Chemistry 17 ( 21 ) 2420 - 2426 2013年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photocatalytic reduction of carbon dioxide (CO 2 ) was carried out using titanium(IV) oxide (TiO 2 ). Methanol (CH 3 OH) was detected as the main product, and trace amounts of formic acid, carbon monoxide, methane, and hydrogen were also detected. The prepared decahedral-shaped anatase TiO 2 with larger {011} and smaller {001} exposed crystal faces showed larger CH 3 OH generation than that of commercial anatase TiO 2 powder, ST-01 (Ishihara Sangyo Co.). Photodeposition of silver and gold nanoparticles on the decahedralshaped anatase TiO 2 induced an increase in CH 3 OH production because the deposited metal particles work as reductive sites for multielectron reduction of CO 2 . © 2013 Bentham Science Publishers.

DOI： 10.2174/13852728113179990055

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Development of highly efficient sulfur-doped TiO<inf>2</inf>photocatalysts hybridized with graphitic carbon nitride 査読有り

Kondo K., Murakami N., Ye C., Tsubota T., Ohno T.

Applied Catalysis B: Environmental 142-143 362 - 367 2013年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Graphitic carbon nitride (g-C 3 N 4 ) has attracted much attention as a metal-free semiconductor having visible-light absorption and relatively high chemical stability. In the present study, we hybridized g-C 3 N 4 with sulfur-doped TiO 2 , which is a visible light-responsive photocatalyst with high oxidation ability, in order to improve photocatalytic activity under visible-light irradiation. Hybrid photocatalysts were prepared by three methods: agate mortar, sonication, and planetary mill. Activities of the hybrid photocatalysts depended on the mixing method. The sample prepared by a planetary mill showed the highest photocatalytic activity, 4-times higher than that of sulfur-doped TiO 2 . We concluded that the high activity of the hybridized sample under visible-light irradiation is induced by charge transfer between the two photocatalysts mimicking the Z-scheme in photosynthesis. © 2013.

DOI： 10.1016/j.apcatb.2013.05.042

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Solution-processed amorphous niobium oxide as a novel electron collection layer for inverted polymer solar cells 査読有り

Hamada K., Murakami N., Tsubota T., Ohno T.

Chemical Physics Letters 586 81 - 84 2013年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Amorphous niobium oxide (NbO x ) as an electron collection layer in inverted polymer solar cells was prepared by a solution process. The power conversion efficiency of inverted polymer solar cells based on a blend of poly(3-hexylthiophene) and[6,6]-phenyl C61 butyric acid methyl ester was improved to 2.22% by inserting an NbO x layer between the active layer and indium tin oxide electrode. An energy level diagram of component materials in the inverted polymer solar cell indicated that the NbO x layer works as both an electron collection layer and hole blocking layer in polymer solar cells. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2013.08.015

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Improvement of capacitance value as the electrode of an electrochemical capacitor by mixing starch with guanidine phosphate 査読有り

Toshiki Tsubota,Yoshihoti Miyauchi,Naoya Murakami,Teruhisa Ohno

Journal of Power Sources 196 ( 13 ) 5769 - 5773 2011年04月

Development of a visible-light-responsive photocatalyst by site-selective modification of iron(III) ion on {111} exposed crystal faces of rutile rod 査読有り

N. Murakami,A. Ono,M. Nakamura,T. Tsubota,T. Ohno

APPLIED CATALYSIS B-ENVIRONMENTAL 97 115 - 119 2010年10月

Development of a visible-light-responsive rutile rod by site-selective modification of iron(III) ion on {1 1 1} exposed crystal faces 査読有り

Murakami N., Ono A., Nakamura M., Tsubota T., Ohno T.

Applied Catalysis B: Environmental 97 ( 1-2 ) 115 - 119 2010年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

{1 1 1} exposed crystal faces of shape-controlled rutile titanium(IV) oxide (TiO 2 ) were site-selectively modified with trivalent iron(III) (Fe 3+ ) ions by utilizing adsorption property of iron(III)/iron(II) (Fe 3+ /Fe 2+ ) ions. The rutile TiO 2 with site-selective modification of Fe 3+ ions showed high photocatalytic activity under visible-light irradiation as a result of separation of redox sites, i.e., oxidation and reduction proceed over Fe 3+ ions on {1 1 1} faces and the bare TiO 2 surface on {1 1 0} faces, respectively. Double-beam photoacoustic spectroscopic analyses suggest that the high activity of TiO 2 with site-selective modification of Fe 3+ ions is attributed to not efficient electron injection from Fe 3+ ions but efficient reduction by injected electrons on {1 1 0} faces. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcatb.2010.03.030

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