研究者詳細 - 坪田　敏樹

論文 - 坪田　敏樹

分割表示118 件中 41 - 60 件目／全件表示 >>

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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