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TANAKA Atsuhiro

    Department of Applied Chemistry　Lecturer
Last Updated :2024/04/19

Researcher Information

Degree

  • Ph.D. in Engineering（Kinki university）

URL

J-Global ID

Research Interests

  • Photocatalysis, Catalysis, Gold nanoparticles, Surface plasmon resonance, Metal nanoparticle   

Research Areas

  • Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Catalytic processes and resource chemistry
  • Nanotechnology/Materials / Energy chemistry
  • Nanotechnology/Materials / Green/sustainable/environmental chemistry
  • Nanotechnology/Materials / Inorganic and coordination chemistry
  • Nanotechnology/Materials / Basic physical chemistry

Academic & Professional Experience

  • 2020/04 - Today  Kindai UniversityFaculty of Science and Engineering, Department of Applied Chemistry講師
  • 2018/10 - 2022/03  科学技術振興機構さきがけ研究者（兼任）
  • 2016/04 - 2020/03  Kindai Univ.Faculty of Science and Engineering, Department of Applied ChemistryAssistant Professor
  • 2015/04 - 2016/03  Ritsumeikan UniversityDepartment of Applied Chemistry, College of Llife Science助教
  • 2014/04 - 2015/03  Research Fellow of the Japan Society for the Promotion of Science (JSPS) （PD）
  • 2013/04 - 2014/03  Research Fellow of the Japan Society for the Promotion of Science (JSPS) （DC2）

Education

  •        - 2014/03  Kinki university  Graduate School of Science and Engineering Research  Molecular and Material Engineering
  •        - 2009/03  Kinki university  Faculty of Science and Engineering  Applied Chemistry

Association Memberships

  • The Japanese Photochemistry Association   Catalysis Society of Japan   The Chemical Society of Japan   

Published Papers

  • Hongxuan Qiu; Akira Yamamoto; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    ACS Applied Energy Materials American Chemical Society (ACS) 6 (22) 11592 - 11601 2574-0962 2023/11
  • Hiroshi Kominami; Reo Akamata; Atsuhiro Tanaka
    Chemistry – A European Journal Wiley 29 (43) 0947-6539 2023/07 
    Abstract Deprotection of pyridine N‐oxides under mild conditions with an inexpensive and environmentally friendly reducing reagent is an important chemical procedure. The use of biomass waste as the reducing reagent, water as the solvent and solar light as the energy source is one of the most promising approaches with minimal impact on the environment. Therefore, a TiO2 photocatalyst and glycerol are suitable components of this type of reaction. Stoichiometric deprotection of pyridine N‐oxide (PyNO) with a minimal amount of glycerol (PyNO:glycerol= 7 : 1) was achieved, with only CO2 being produced as the final oxidation product of glycerol. The deprotection of PyNO was thermally accelerated. Under solar light, the temperature of the reaction system increased to 40–50 °C and PyNO was also quantitatively deprotected, indicating that solar energy, i. e., UV light and thermal energy, can be effectively used. The results provide a new approach in the fields of organic chemistry and medical chemistry using biomass waste and solar light.
  • Hongxuan Qiu; Akihiko Anzai; Tayyebeh Soltani; Akira Yamamoto; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    ACS Applied Energy Materials 2023/05
  • Eri Fudo; Yusuke Kiyota; Ryuto Osawa; Atsuhiro Tanaka; Hiroshi Kominami
    Applied Catalysis A: General Elsevier BV 657 119156 - 119156 0926-860X 2023/05
  • Kousuke Nakanishi; Sakae Araki; Kousuke Nomoto; Yuichi Onoue; Ryosuke Yagi; Hiroyuki Asakura; Atsuhiro Tanaka; Tsunehiro Tanaka; Hiroshi Kominami
    Physical Chemistry Chemical Physics Royal Society of Chemistry (RSC) 25 (33) 21868 - 21874 1463-9076 2023 
    Cyclohexanecarboxylic acid as the ring hydrogenation product of benzoic acid was successfully obtained when Ru and Pd were simultaneously loaded on TiO2, indicating that this bimetallic system can be used in place of an Rh cocatalyst.
  • Eri Fudo; Hiroyuki Asakura; Atsuhiro Tanaka; Hiroshi Kominami
    Sustainable Energy & Fuels Royal Society of Chemistry (RSC) 7 (4) 1077 - 1083 2023 
    Plasmonic water splitting to H2 and O2 with the ratio of 2 : 1 occurred continuously under irradiation of visible light when an Au/Ta2O5/FTO photoanode was used under an externally applied potential of 0.8 V vs. RHE to a Pt counter electrode.
  • Hiroshi Kominami; Kazuhiro Onogi; Atsuhiro Tanaka
    Journal of Photochemistry and Photobiology A: Chemistry Elsevier BV 430 113963 - 113963 1010-6030 2022/09 [Refereed]
  • Hiroshi Kominami; Ryuichi Yato; Atsuhiro Tanaka
    ChemCatChem Wiley 1867-3880 2022/08 [Refereed]
  • Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami
    ACS Applied Nano Materials American Chemical Society (ACS) 5 (7) 8982 - 8990 2574-0970 2022/07 [Refereed]
  • Xuanwen Xu; Hiroyuki Asakura; Saburo Hosokawa; Tsunehiro Tanaka; Kentaro Teramura
    Catalysis Today Elsevier BV 410 273 - 281 0920-5861 2022/06 [Refereed]
  • Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami
    Catalysis Today Elsevier BV 0920-5861 2022/05 [Refereed]
  • Yuhei Yamamoto; Hibiki Toda; Atsuhiro Tanaka; Hiroshi Kominami
    ChemCatChem Wiley 14 (5) 1867-3880 2022/03
  • Xuanwen Xu; Kentaro Teramura; Hiroyuki Asakura; Saburo Hosokawa; Tsunehiro Tanaka
    Applied Catalysis B: Environmental Elsevier BV 298 120508 - 120508 0926-3373 2021/12 [Refereed]
  • Surya Pratap Singh; Akira Yamamoto; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    ACS Catalysis American Chemical Society (ACS) 11 (22) 13768 - 13781 2155-5435 2021/11 [Refereed]
  • Shota Imai; Yasumi Kojima; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami
    Applied Catalysis A: General Elsevier BV 624 118331 - 118331 0926-860X 2021/08 [Refereed]
  • Tayyebeh Soltani; Akira Yamamoto; Surya Pratap Singh; Akihiko Anzai; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    ACS Applied Energy Materials American Chemical Society (ACS) 4 (7) 6500 - 6510 2574-0962 2021/07 [Refereed]
  • Tayyebeh Soltani; Xing Zhu; Akira Yamamoto; Surya Pratap Singh; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    Applied Catalysis B: Environmental Elsevier BV 286 119899 - 119899 0926-3373 2021/06 [Refereed]
  • Hiroyuki Asakura; Tsunehiro Tanaka
    Chemistry Letters The Chemical Society of Japan 50 (5) 1075 - 1085 0366-7022 2021/05 [Refereed]
  • Eri Fudo; Atsuhiro Tanaka; Shoji Iguchi; Hiroshi Kominami
    Sustainable Energy & Fuels Royal Society of Chemistry (RSC) 5 3303 - 3311 2021 [Refereed]
     

    Plasmonic water splitting (H2O → H2 + 1/2O2) over a metal-loaded metal oxide under irradiation of visible light is still difficult, although conversion of organic compounds over plasmonic photocatalysts has...

  • Sakae Araki; Kousuke Nakanishi; Atsuhiro Tanaka; Hiroshi Kominami
    Journal of Catalysis Elsevier BV 389 212 - 217 0021-9517 2020/09 [Refereed]
  • Yamamoto, Akifumi; Tanaka, Atsuhiro; Kominami, Hiroshi; Fujioka, Daiki; Sanada, Tomoe; Kojima, Kazuo
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AMER SCIENTIFIC PUBLISHERS 20 (7) 4131 - 4137 1533-4880 2020/07 [Refereed]
     
    Disk-shaped tungsten(VI) oxide (D-WO3) particles were synthesized according to a previously reported method consisting of pyrolysis, precipitation, and calcination, and the calcination temperature was changed (200-600 degrees C). The samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, the Brunauer-Emmett-Teller single-point method, and diffuse reflectance spectroscopy. In addition, to evaluate the photocatalytic activities of the samples, the mineralization of acetic acid to carbon dioxide (CO2) was measured by loading Pt particles onto the surface of the samples by photodeposition and irradiating them in an aqueous suspension with a blue light-emitting diode. Increasing the calcination temperature was associated with several changes: the crystallites grew larger, increasing the crystallinity; the specific surface area decreased, decreasing the adsorption capacity; and the rate of the photocatalytic CO2 evolution reaction increased. Pt-loaded (0.1 wt%) D-WO3 calcined at 600 degrees C showed the highest activity with a CO2 evolution rate of 5.9 mu mol h(-1). These results indicated that improving the crystallinity of the D-WO3 samples was effective in increasing their photocatalytic activities.
  • Makoto Fukui; Atsuhiro Tanaka; Hiroshi Kominami
    Industrial & Engineering Chemistry Research American Chemical Society (ACS) 59 (25) 11412 - 11418 0888-5885 2020/06 [Refereed]
  • Makoto Fukui; Atsuhiro Tanaka; Hiroshi Kominami
    ChemCatChem Wiley 12 (12) 3298 - 3305 1867-3880 2020/06 [Refereed]
  • Facet-selective deposition of a silver–manganese dual cocatalyst on potassium hexatitanate photocatalyst for highly selective reduction of carbon dioxide by water
    Xing Zhu; Akira Yamamoto; Shota Imai; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    Applied Catalysis B: Environmental 274 119085  2020/04 [Refereed]
  • Makoto Fukui; Atsuhiro Tanaka; Hiroshi Kominami
    Applied Catalysis A: General Elsevier BV 591 117412 - 117412 0926-860X 2020/02
  • Imai, Shota; Nakanishi, Kousuke; Tanaka, Atsuhiro; Kominami, Hiroshi
    CHEMCATCHEM WILEY-V C H VERLAG GMBH 1867-3880 2020/02 [Refereed]
     
    Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H-2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core-Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two-step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. Thus-prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4-octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4-Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4-octyne was semihydrogenated to cis-4-octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4-octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H-2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.
  • Makoto Fukui; Wakiko Koshida; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    Applied Catalysis B: Environmental Elsevier BV 268 118446 - 118446 0926-3373 2019/12 [Refereed]
     
    Since reduction and oxidation reactions simultaneously occur over a photocatalyst, a hole scavenger (a hydrogen source in the field of organic chemistry) is required to obtain a reduced product. The use of organic waste as the hole scavenger is environmentally favorable because the organic waste is degraded during the photocatalytic reduction. In this study, methylamine was used as the hole scavenger for photocatalytic reduction (hydrogenation) of nitrobenzenes over a titanium(IV) oxide photocatalyst. Corresponding anilines were obtained almost quantitatively at room temperature and under atmospheric pressure without the use of a precious metal and hydrogen gas. Nitrobenzenes having reducible functional groups such as chloro and acetyl groups were chemoselectively hydrogenated to corresponding anilines with the groups being preserved. Various parameters affecting the efficiency and the rate of the photocatalytic reaction are discussed on the basis of results of the physicochemical analyses.
  • A silver–manganese dual co-catalyst for selective reduction of carbon dioxide into carbon monoxide over a potassium hexatitanate photocatalyst with water
    Xing Zhu; Akira Yamamoto; Shota Imai; Atsuhiro Tanaka; Hiroshi Kominami; Hisao Yoshida
    Chem. Commun. 55 13514 - 13517 2019/09 [Refereed]
  • Fudo, Eri; Tanaka, Atsuhiro; Kominami, Hiroshi
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 48 (8) 939 - 942 0366-7022 2019/08 [Refereed]
     
    Gold (Au)-modified tantalum(V) oxide (Ta2O5) prepared by using a colloid photodeposition method produced H-2 without the aid of a cocatalyst under visible light irradiation due to the sufficiently negative potential of electrons injected from Au nanoparticles into the conduction band of Ta2O5 (-0.47 V).
  • Kinoshita, Atsufumi; Nakanishi, Kousuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    CHEMPHOTOCHEM WILEY-V C H VERLAG GMBH 3 (7) 559 - 567 2367-0932 2019/07 [Refereed]
     
    Photocatalytic ring hydrogenation of phenol proceeded in an aqueous suspension of palladium-loaded TiO2 at room temperature in the presence of oxalic acid as a hole scavenger, and cyclohexanone was produced in a high yield (90 %) without the use of hydrogen gas. Cyclohexanone was formed via keto-enol tautomerism of cyclohexenol. The effects of hole scavengers and solvents on the hydrogenation of phenol can be explained by the adsorption behaviour of phenol and hole scavengers in the solvents. Over a Pd-TiO2 photocatalyst, the apparent activation energy (Ea) in the ring hydrogenation of phenol and the Ea value in the hydrogenation of cyclohexanone were estimated to be 25 kJ mol(-1) and 36 kJ mol(-1), respectively, as calculated by using the Arrhenius equation. We concluded that the difference in the Ea values is attributable to the selective production of cyclohexanone and the decreased production of cyclohexanol in the ring hydrogenation of phenol over a Pd-TiO2 photocatalyst.
  • Fudo, Eri; Tanaka, Atsuhiro; Kominami, Hiroshi
    CATALYSIS SCIENCE & TECHNOLOGY ROYAL SOC CHEMISTRY 9 (12) 3047 - 3054 2044-4753 2019/06 [Refereed]
     
    There is little information on the effect of the conduction band (CB) position on plasmonic hydrogen (H-2) formation under visible light irradiation over gold (Au) nanoparticles supported on semiconductors because there were no appropriate materials for which the CB position gradually changes. In this study, we analyzed the flatband potential of strontium ion (Sr2+)-doped cerium.IV) oxide (CeO2:Sr) and found that the CB position gradually shifted negatively from +0.031 V to -1.49 V vs. NHE with an increase in the Sr2+ mole fraction. Plasmonic photocatalysts consisting of Au nanoparticles, CeO2:Sr and a platinum (Pt) cocatalyst were prepared and characterized by using X-ray diffraction, UV-vis spectroscopy, and transmission electron spectroscopy. Photocatalytic reaction under visible light irradiation revealed that H-2 was produced over Au nanoparticles supported on CeO2:Sr having the CB potential of -0.61 V vs. NHE and that the negative limit of the CB position for electron injection from Au nanoparticles existed between -0.61 V and -1.49 V vs. NHE. We found that Au/CeO2:Sr plasmonic photocatalysts also produced H-2 without the aid of a Pt cocatalyst due to the sufficiently negative potential of electrons injected into the CB of CeO2:Sr.
  • Fukui, Makoto; Omori, Yuya; Kitagawa, Shin-ya; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    JOURNAL OF CATALYSIS ACADEMIC PRESS INC ELSEVIER SCIENCE 374 36 - 42 0021-9517 2019/06 [Refereed]
     
    Hydrogen (H-2)-free and poison (lead and quinoline)-free semihydrogenation of alkynes to cis-alkenes under gentle conditions is one of the challenges to be solved. In this study, a titanium(IV) oxide photocatalyst having two functions (visible light responsiveness and semihydrogenation activity) was prepared by modification with 2,3-dihydroxynaphthalene (DHN) and a copper (Cu) co-catalyst, respectively. The photocatalyst (DHN/TiO2-Cu) showed high performance for diastereoselective semihydrogenation of alkynes to cis-alkenes in water-acetonitrile solution under visible light irradiation without the use of H-2 and poisons. Alkynes having reducible functional groups were converted to the corresponding alkenes with the functional groups being preserved. The addition of water to acetonitrile changed the amount of alkynes adsorbed on the photocatalyst, which was a decisive factor determining the rate of hydrogenation. A relatively large apparent activation energy, 27 kJ mol(-1), was obtained by a kinetic study, indicating that the rate-determining step of this reaction was not an electron production process but a thermal catalytic semihydrogenation process over the Cu co-catalyst. Semihydrogenation and hydrogen evolution occurred competitively on Cu metals and the former became predominant at slightly elevated temperatures, which is discussed on the basis of the kinetic parameters of two reactions. (C) 2019 Elsevier Inc. All rights reserved.
  • Kinoshita, Atsufumi; Nakanishi, Kousuke; Yagi, Ryosuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    APPLIED CATALYSIS A-GENERAL ELSEVIER 578 83 - 88 0926-860X 2019/05 [Refereed]
     
    Since photocatalytic reactions are almost consistent with the concept of green chemistry, substance conversion using photocatalysts has recently attracted the attention of researchers in the fields of organic chemistry, physical chemistry and material chemistry. We investigated photoinduced ring hydrogenation of phenol over a metal-loaded titanium(IV) oxide (TiO2) photocatalyst without the use of H-2 gas and we report here the effects of various parameters, including the type and amount of metal co-catalyst loaded on TiO2 and the kinds of solvents and hole scavengers, on the ring hydrogenation. We found that the combination of an Rh co-catalyst, water and oxalic acid resulted in the highest yield of cyclohexanol. Detailed analyses revealed that phenol was first hydrogenated to cyclohexanone via keto-enol tautomerism of cyclohexenol followed by hydrogenation of cyclohexanone to cyclohexanol and that adsorption of phenol onto Rh-TiO2 is a factor of great importance for the ring hydrogenation.
  • Yamamoto, Yuhei; Fukui, Makoto; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    CATALYSIS SCIENCE & TECHNOLOGY ROYAL SOC CHEMISTRY 9 (4) 966 - 973 2044-4753 2019/02 [Refereed]
     
    A titanium.IV) oxide photocatalyst modified with 2,3-dihydroxynaphthalene (DHN/TiO2) responds to visible light, and electrons are photogenerated to the conduction band of TiO2 under light irradiation in the presence of a suitable hole scavenger. The reducing potential of DHN/TiO2 was applied for photocatalytic conversion of a nitro group to an amino group of aromatics having other reducible groups under hydrogenfree and noble metal-free conditions at room temperature. Various nitro aromatics having vinyl, chloro, bromo, and acetyl groups were converted to amino aromatics with high yields with the reducible groups being preserved. Some parameters affecting the catalytic performance were investigated, and the reaction rate was almost determined by the amount of the substrate adsorbed on DHN/TiO2.
  • Kominami, Hiroshi; Shiba, Misaki; Hashimoto, Akimi; Imai, Shota; Nakanishi, Kousuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Imamura, Kazuya
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS ROYAL SOC CHEMISTRY 20 (29) 19321 - 19325 1463-9076 2018/08 [Refereed]
     
    A copper-loaded titanium(IV) oxide photocatalyst exhibited perfect selectivity in hydrogenation of alkynes to alkenes in an alcohol solution at 298 K under hydrogen-free and poison-free conditions. A slight elevation in the reaction temperature to 323 K greatly increased the reaction rate with the selectivity being preserved and the formation of an H-2 by-product being suppressed. The apparent activation energy of 4-octyne semihydrogenation was determined to be 54 kJ mol(-1), indicating that the rate determining step of this photocatalytic reaction was not an electron production process but a thermocatalytic hydrogenation process under light irradiation.
  • Kojima, Yasumi; Fukui, Makoto; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    CHEMCATCHEM WILEY-V C H VERLAG GMBH 10 (16) 3605 - 3611 1867-3880 2018/08 [Refereed]
     
    Lindlar's catalyst, i.e., calcium carbonate-supported palladium (Pd) modified with lead, has been used for semihydrogenation of an alkynyl group in the presence of hydrogen gas (H-2). We examined hydrogenation of an alkynyl group in organosilane and hydrocarbon in methanolic suspensions of a Pd-loaded titanium(IV) oxide (Pd-TiO2) photocatalyst without the use of additives and H-2. In the photocatalytic reaction, Pd particles worked as co-catalysts for hydrogenation and alkyne hydrogenation had priority to alkene hydrogenation. Since the Pd co-catalyst was temporarily deactivated during the reaction owing to accumulation of the oxidized product(s) of methanol, the capacity of hydrogenation of the unsaturated C-C bond was limited. By optimizing the capacity and amount of alkynes, almost complete semihydrogenation of alkynes was achieved under a poison-free condition. Pd-TiO2 can be regenerated by very simple treatments, i.e., washing and drying at room temperature.
  • Imamura, Kazuya; Kato, Hiroko; Wada, Yuichiro; Makabe, Kazuhiro; Onda, Ayumu; Tanaka, Atsuhiro; Kominami, Hiroshi; Sato, Katsutoshi; Nagaoka, Katsutoshi
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 54 (53) 7298 - 7301 1359-7345 2018/07 [Refereed]
     
    In the presence of a palladium-loaded TiO2 photocatalyst, the cleavage of benzyl phenyl ether in low-molecular-weight alcohol solvents under de-aerated conditions afforded toluene and phenol simultaneously in a 1:1 molar ratio.
  • Kaneyama, Yuka; Tanaka, Atsuhiro; Sanada, Tomoe; Kominami, Hiroshi; Kojima, Kazuo
    MATERIALS RESEARCH BULLETIN PERGAMON-ELSEVIER SCIENCE LTD 102 56 - 61 0025-5408 2018/06 [Refereed]
     
    We synthesized various cuboid-type tungsten trioxide (WO3) particles using a hydrothermal method followed by calcination at various temperatures between 200 and 500 degrees C. Visible-light photocatalysis of these particles was investigated for oxygen (O-2) evolution from water in the presence of sacrificial silver(I) sulfate. The calculated crystallite diameters increased with increasing calcination temperature, suggesting that the level of crystallinity increased with calcination temperature. The average specific surface area of the particles was almost the same for all calcination temperatures in the range 200-400 degrees C, but was decreased at 500 degrees C. The photocatalytic reaction rate of O-2 formation increased with increasing calcination temperature up to 400 degrees C, and then decreased as calcination temperature was further increased to 500 degrees C. We therefore concluded that the rate increased with calcination temperature up to 400 degrees C due to the increasing crystallinity, but then decreased due to the decreased specific surface area.
  • Zeai Huang; Kentaro Teramura; Hiroyuki Asakura; Saburo Hosokawa; Tsunehiro Tanaka
    CATALYSIS TODAY ELSEVIER SCIENCE BV 300 173 - 182 0920-5861 2018/02 [Refereed]
     
    A facile one-pot flux method was applied to fabricate K2RETa5O15 (RE = rare-earth element) with tetragonal tungsten bronze (TTB) structures. Pure TTB structures of K2RETa5O15 (RE = La, Ce, Pr, Nd, and Sm) with rodlike morphologies were obtained using KCl as the potassium source and flux. For other potassium rare-earth tantalates, the TTB structure was dominant, with an additional RETaO4 phase present. Among all these K2RETa5O15, K2YTa5O15 gave the highest activity for photoreduction of CO2 with good selectivity toward CO evolution using H2O as an electron donor, even in the presence of additional YTaO4 phase. YTaO4 fabricated using the flux method under same condition was inactive for photoreduction of CO2 using H2O. It was found that the activity for the photoreduction of CO2 to be significantly affected by the weight ratio of potassium chloride to yttrium oxide and tantalum oxide (K/YT) in the fabrication process. The highest photoreduction activity achieved in CO evolution was 91.9 mu mol h(-1) (for 1.0-g catalyst , with CO selectivity of 84.9%, at K/YT= 1.0. Surface analysis of these tantalates fabricated with different K/YT ratios showed that a high ratio of surface yttrium to tantalum (Y/Ta) was important to achieve a high CO evolution rate.
  • Wada, Noriyuki; Yokomizo, Yuji; Yogi, Chihiro; Katayama, Misaki; Tanaka, Atsuhiro; Kojima, Kazuo; Inada, Yasuhiro; Ozutsumi, Kazuhiko
    JOURNAL OF MATERIALS RESEARCH CAMBRIDGE UNIV PRESS 33 (4) 467 - 481 0884-2914 2018/02 [Refereed]
     
    To investigate the effects of adding Au nanoparticles (AuNPs) to TiO2 films on the crystallization, phase transformation, and photocatalysis, films of both TiO2 and TiO2 embedded with AuNPs (Au-TiO2) with various characteristics were prepared by using the dip-coating method with preheating and post-heating treatments. The AuNPs acted as anatase nucleation agents and crystallized a lot of small anatase crystals with sizes of tens of nanometers, which suppressed the growth of anatase crystals that are large enough for them to transform into rutile crystals, resulting in repression of the transformation from anatase into rutile. The AuNPs affected the progress of the photocatalytic and adsorption reactions, resulting in improved photocatalytic activity. Of all the films we tested, the Au-TiO2 film preheated at 400 degrees C and post-heated at 400 degrees C (AT400-400), which consisted of small anatase crystals with high covalent character and high crystallinity, contained dispersed AuNPs with the smallest average crystallite size and showed the highest photocatalytic activity. This high activity resulted from the high reaction rate constants for adsorption and photocatalysis.
  • Nakanishi, Kousuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 47 (2) 254 - 256 0366-7022 2018 [Refereed]
     
    Photocatalytic hydrogenation of furfural (FAL) was examined in 2-pentanol suspensions of TiO2 under metal-free and hydrogen-free conditions. High chemoselectivity was observed, i.e., only the carbonyl group of FAL was reduced to a hydroxymethyl group, resulting in almost quantitative conversion to furfuryl alcohol (FOL) with an apparent quantum efficiency of 17%. 2-Pentanol was simultaneously converted to 2-pentanone satisfying a high stoichiometry with FAL to FOL, indicating that double up-grading of FAL and alcohol was possible via a photocatalytic process.
  • Nakanishi, Kousuke; Yagi, Ryosuke; Imamura, Kazuya; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi
    CATALYSIS SCIENCE & TECHNOLOGY ROYAL SOC CHEMISTRY 8 (1) 139 - 146 2044-4753 2018/01 [Refereed]
     
    There are various possibilities of co-catalyst-assisted photocatalytic reduction (CPR) over a titanium(IV) oxide (TiO2) photocatalyst, especially H-2-free and chemoselective CPR. We examined the photoinduced ring hydrogenation of aromatics having a carboxyl group over metal-loaded TiO2 under H-2-free conditions and found that the aromatics were almost quantitatively hydrogenated to the corresponding cyclohexanes having a carboxyl group when rhodium, water and oxalic acid were used as a metal co-catalyst, solvent and hole scavenger, respectively. The effects of different metal co-catalysts, solvents and hole scavengers on the ring hydrogenation were also examined. Based on the results obtained under various conditions, the light dependency and adsorption behavior of the aromatics and hole scavengers, the functions of TiO2 and the co-catalyst, and the reaction process are discussed.
  • Kousuke Nakanishi; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS ROYAL SOC CHEMISTRY 19 (30) 20206 - 20212 1463-9076 2017/08 [Refereed]
     
    The use of metal co-catalysts broadens the application of photocatalytic reduction without the use of dihydrogen (H-2) gas. We examined photocatalytic hydrogenation of furan, a representative heterocyclic compound and a compound derived from biomass, in alcoholic suspensions of metal-loaded titanium(IV) oxide (TiO2) under a H-2-free condition and we found that furan was almost quantitatively hydrogenated to tetrahydrofuran with a high apparent quantum efficiency of 37% at 360 nm when palladium was used as a co-catalyst. Effects of different metal co-catalysts, different amounts of the co-catalyst, the type of TiO2, the type of alcohol, light wavelength and reusability for furan hydrogenation were investigated. Based on the results, the functions of TiO2 and the co-catalyst and the reaction process are discussed.
  • Sho Kitano; Masaaki Sadakiyo; Kenichi Kato; Miho Yamauchi; Hiroyuki Asakura; Tsunehiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    APPLIED CATALYSIS B-ENVIRONMENTAL ELSEVIER SCIENCE BV 205 340 - 346 0926-3373 2017/05 [Refereed]
     
    For a rhodium ion-modified TiO2 (Rh3+/TiO2) photocatalyst responding to visible light, control of the structure of the Rh3+ modifier and effects of the structures of the Rh3+ modifier on photocatalytic activities were examined. A TiO2 support was pre-calcined to maintain crystallinity and specific surface area during post-calcination, and the structure of the Rh3+ modifier for Rh3+/TiO2 was changed by post-calcination without causing changes in the crystallinity and specific surface area of the TiO2 support. In mineralization of acetone under irradiation of visible light, the photocatalytic activities of the post-calcined Rh3+/TiO2 showed a volcano-like tendency as a function of post-calcination temperature. The results of this study showed that an atomically isolated structure of the Rh3+ modifier was preferable for high activities and that aggregation of the Rh species led to a decrease in the activities. (C) 2016 Elsevier B.V. All rights reserved.
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 53 (35) 4759 - 4762 1359-7345 2017/05 [Refereed]
     
    By using a facile calcination method, we succeeded in the preparation of partially spherical gold particles supported on TiO2 exhibiting photoabsorption due to surface plasmon resonance at around 620 nm. Surprisingly, the selective oxidation of benzyl alcohol to benzaldehyde occurred in an aqueous suspension of thus-prepared Au/TiO2 under irradiation of light from a Xe lamp with an R60 cut-off filter (lambda > 600 nm), and the apparent quantum efficiency reached 7.2% at 625 nm and 4.2% even at 700 nm.
  • Makoto Fukui; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 53 (30) 4215 - 4218 1359-7345 2017/04 [Refereed]
     
    An organically modified titanium dioxide photocatalyst prepared by a simple impregnation method chemoselectively and almost quantitatively converted benzaldehydes having other reducible functional groups to the corresponding benzyl alcohols under visible light irradiation.
  • A. Tanaka; K. Teramura; S. Hosokawa; H. Kominami; T. Tanaka
    CHEMICAL SCIENCE ROYAL SOC CHEMISTRY 8 (4) 2574 - 2580 2041-6520 2017/04 [Refereed]
     
    We found that plasmonic Au particles on titanium(IV) oxide (TiO2) act as a visible-light-driven photocatalyst for overall water splitting free from any additives. This is the first report showing that surface plasmon resonance (SPR) in a suspension system effectively induces overall water splitting. Modification with various types of metal nanoparticles as co-catalysts enhanced the evolution of H-2 and O-2. Among these, Ni-modified Au/TiO2 exhibited 5-times higher rates of H-2 and O-2 evolution than those of Ni-free Au/TiO2. We succeeded in designing a novel solar energy conversion system including three elemental technologies, charge separation with light harvest and an active site for O-2 evolution (plasmonic Au particles), charge transfer from Au to the active site for H-2 production (TiO2), and an active site for H-2 production (Ni cocatalyst), by taking advantage of a technique for fabricating size-controlled Au and Ni nanoparticles. Water splitting occurred in aqueous suspensions of Ni-modified Au/TiO2 even under irradiation of light through an R-62 filter.
  • Makoto Fukui; Hideki Kouda; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMISTRYSELECT WILEY-V C H VERLAG GMBH 2 (7) 2293 - 2299 2365-6549 2017/03 [Refereed]
     
    Chemoselective reduction of benzaldehydes having other reducible functional groups without the use of a reducing agent such as metal hydrides is important because metal hydrides simultaneously produce a large amount of undesirable waste containing metal compounds. Here we report that a titanium(IV) oxide (TiO2) photocatalyst is effective for heterogeneous Meerwein-Ponndorf-Verley (MPV)-type reduction of various benzaldehydes having reducible functional groups to corresponding benzyl alcohols at room temperature under a metal-free condition. We also investigated the effects of physical properties of TiO2 samples on chemoselective reduction of p-chlorobenzaldehyde (CBAD) to p-chlorobenzyl alcohol (CBAO) and we observed a linear correlation between the amount of CBAD adsorbed and the rate of CBAO formation, suggesting that ability of TiO2 for CBAD adsorption is one of the key factors for effective MPV-type reduction of CBAD to CBAO.
  • Jiaguang Zhang; Mahmoud Ibrahim; Vincent Colliere; Hiroyuki Asakura; Tsunehiro Tanaka; Kentaro Teramura; Karine Philippot; Ning Yan
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL ELSEVIER SCIENCE BV 422 188 - 197 1381-1169 2016/10 [Refereed]
     
    Surface decoration strategy is applied to design NP catalyst for the selective hydrogenolysis of C-O bond without hydrogenating benzene ring, which is critical in lignin conversion under hydrogen treatment. The synthesized NiOx/Rh NPs are featured with-Rh core whose surface is partially blocked by NiOx which segregated the surface terrace zones into smaller segments, preventing the coordination and hydrogenation of benzene rings. Moreover, the NiOx shows, no electronic modification to the Rh core, thereby the blockage effect of NiOx only inhibits the hydrogenation of benzene ring but not affect the hydrogenolysis activity-of Rh core. (C) 2016 Elsevier B.V. All rights reserved.
  • Makoto Fukui; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 45 (8) 985 - 987 0366-7022 2016/08 [Refereed]
     
    p-Chlorobenzaldehyde was almost quantitatively and chemoselectively reduced to p-chlorobenzyl alcohol in alcoholic suspensions of a metal-free titanium(IV) oxide photocatalyst under hydrogen-free conditions. Since alcohols act as electron donors and hydrogen sources, this reaction can be regarded as a heterogeneous Meerwein-Ponndorf-Verley-type reduction over a photocatalyst. Excellent chemoselectivity was also observed in the intermolecular competitive reduction of benzaldehyde (BA) and chlorobenzene (CB), i.e., only BA was reduced to benzyl alcohol, with CB not being reduced.
  • Sho Kitano; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    APPLIED CATALYSIS A-GENERAL ELSEVIER SCIENCE BV 521 202 - 207 0926-860X 2016/07 [Refereed]
     
    Metal ion-modified TiO2 photocatalysts designated by combinations of various metal ions and TiO2 powders that respond to visible light and exhibit controllable photocatalytic oxidative performances were examined. The photocatalytic oxidative performances were evaluated by selective oxidation of benzyl alcohol in water in the presence of O-2 under irradiation of visible light. The TiO2 samples modified with Ru3+, Pd2+ and Rh3+ (Ru3+/TiO2, Pd2+/TiO2 and Rh3+/TiO2) exhibited high levels of photocatalytic activity. The effects of metal ions and the kind of TiO2 on photocatalytic performances of Rh3+/TiO2 and Ru3+/TiO2 were investigated in detail. (C) 2015 Elsevier B.V. All rights reserved.
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMISTRY-A EUROPEAN JOURNAL WILEY-V C H VERLAG GMBH 22 (13) 4592 - 4599 0947-6539 2016/03 [Refereed]
     
    Gold particles supported on tin(IV) oxide (0.2wt% Au/SnO2) were modified with copper and silver by the multistep photodeposition method. Absorption around =550nm, attributed to surface plasmon resonance (SPR) of Au, gradually shifted to longer wavelengths on modification with Cu and finally reached =620nm at 0.8wt% Cu. On the other hand, the absorption shifted to shorter wavelength with increasing amount of Ag and reached =450nm at 0.8wt% Ag. These Cu- and Ag-modified 0.2wt% Au/SnO2 materials (Cu-Au/SnO2 and Ag-Au/SnO2) and 1.0wt% Au/SnO2 were used for mineralization of formic acid to carbon dioxide in aqueous suspension under irradiation with visible light from a xenon lamp and three kinds of light-emitting diodes with different wavelengths. The reaction rates for the mineralization of formic acid over these materials depend on the wavelength of light. Apparent quantum efficiencies of Cu-Au/SnO2, Au/SnO2, and Ag-Au/SnO2 reached 5.5% at 625nm, 5.8% at 525nm, and 5.1% at 450nm, respectively. These photocatalysts can also be used for selective oxidation of alcohols to corresponding carbonyl compounds in aqueous solution under visible-light irradiation. Broad responses to visible light in formic acid mineralization and selective alcohol oxidation were achieved when the three materials were used simultaneously.
  • Zheng Wang; Kentaro Teramura; Zeai Huang; Saburo Hosokawa; Yoshihisa Sakata; Tsunehiro Tanaka
    CATALYSIS SCIENCE & TECHNOLOGY ROYAL SOC CHEMISTRY 6 (4) 1025 - 1032 2044-4753 2016 [Refereed]
     
    Stoichiometric evolutions of CO, H-2, and O-2 were achieved for the photocatalytic conversion of CO2 with H2O as an electron donor using Ag-loaded Zn-modified Ga2O3. The selectivity toward the evolution of CO over H-2 can be controlled by varying the amount of Zn species added in the Ag-loaded Zn-modified Ga2O3 photocatalyst. The production of H-2 gradually decreased with increasing amounts of Zn species from 0.1 to 10.0 mol%, whereas the evolution of CO was almost unchanged. The XRD, XAFS, and XPS measurements revealed that a ZnGa2O4 layer was generated on the surface of Ga2O3 by modification with Zn species. The formation of the ZnGa2O4 layer eliminated the proton reduction sites on Ga2O3, although the crystallinity, surface area, and morphology of Ga2O3 as well as the particle size and chemical state of Ag did not change. In conclusion, we designed a highly selective photocatalyst for the conversion of CO2 with H2O as an electron donor using Ag (the cocatalyst for the CO evolution), ZnGa2O4 (the inhibitor of the H-2 production), and Ga2O3 (the photocatalyst).
  • Yongjun Gao; Xi Chen; Jiaguang Zhang; Hiroyuki Asakura; Tsunehiro Tanaka; Kentaro Teramura; Ding Ma; Ning Yan
    ADVANCED MATERIALS WILEY-V C H VERLAG GMBH 27 (32) 4688 - 4694 0935-9648 2015/08 [Refereed]
  • Yuri Nishino; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 44 (4) 518 - 520 0366-7022 2015/04 [Refereed]
     
    Two kinds of photoabsorption of Ag-deposited silver iodide (AgI) due to band-gap excitation of AgI and surface plasmon resonance of Ag particles each contributed to photocatalytic partial oxidation of alcohol, and a synergy effect on the reaction rate was observed when two kinds of light were simultaneously irradiated on Ag-AgI.
  • Jiaguang Zhang; Jason Teo; Xi Chen; Hiroyuki Asakura; Tsunehiro Tanaka; Kentaro Teramura; Ning Yan
    ACS CATALYSIS AMER CHEMICAL SOC 4 (5) 1574 - 1583 2155-5435 2014/05 [Refereed]
     
    In this paper, NiRu, NiRh, and NiPd catalysts were synthesized and evaluated in the hydrogenolysis of lignin C O bonds, which is proved to be superior over single-component catalysts. The optimized NiRu catalyst contains 85% Ni and 15% Ru, composed of Ni surface-enriched, Ru Ni atomically mixed, ultrasmall nanoparticles. The Ni85Ru15 catalyst showed high activity under low temperature (100 degrees C), low H-2 pressure (1 bar) in beta-O-4 type C-Obond hydrogenolysis. It also exhibited significantly higher activity over Ni and Ru catalysts in the direct conversion of lignin into monomeric aromatic chemicals. Mechanistic investigation indicates that the synergistic effect of NiRu can be attributed to three factors: (1) increased fraction of surface atoms (compared with Ni), (2) enhanced H-2 and substrate activation (compared with Ni), and (3) inhibited benzene ring hydrogenation (compared with Ru). Similarly, NiRh and NiPd catalysts were more active and selective than their singlecomponent counterparts in the hydrogenolysis of lignin model compounds and real lignin.
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AMER CHEMICAL SOC 136 (2) 586 - 589 0002-7863 2014/01 [Refereed]
     
    Photocatalytic H-2 and O-2 formations under visible light irradiation (lambda > 400 nm) are demonstrated using Pt-Au nanopaticles for the reduction site and WO3 for the oxidation site in solid-state Pt/Au/WO3.
  • Atsuhiro Tanaka; Satoshi Sakaguchi; Keiji Hashimoto; Hiroshi Kominami
    CATALYSIS SCIENCE & TECHNOLOGY ROYAL SOC CHEMISTRY 4 (7) 1931 - 1938 2044-4753 2014 [Refereed]
     
    Titanium(IV) oxide (TiO2) having both smaller and larger gold (Au) particles was successfully prepared by a multi-step (MS) photodeposition method. When 0.25 wt% Au loading per photodeposition was repeated four times, smaller and larger Au particles having average diameters of 1.4 and 13 nm, respectively, were fixed on TiO2, and the Au/TiO2 sample exhibited strong photoabsorption around 550 nm due to surface plasmon resonance (SPR) of the larger Au particles. Various Au/TiO2 samples were prepared by changing the Au loading per photodeposition and the number of photodepositions. Effects of the conditions in MS photodeposition and sample calcination on Au particle distribution and photoabsorption properties were investigated. These samples were used for hydrogen (H-2) formation from 2-propanol and mineralization of acetic acid in aqueous suspensions under irradiation of visible light. In the case of H-2 formation under deaerated conditions, the reaction rate of Au/TiO2 having both larger and smaller particles was 4 times higher than that of the Au/TiO2 sample without smaller Au particles, indicating that smaller Au particles acted effectively as a co-catalyst, that is, as reduction sites for H-2 evolution. On the other hand, in the case of mineralization of acetic acid under aerated conditions, carbon dioxide formation rates were independent of the presence of smaller Au particles, indicating that the smaller Au particles had little effect on the mineralization of acetic acid. To extend the possibility of Au/TiO2 for H-2 formation under irradiation of visible light, H-2 formation from ammonia (NH3) as biomass waste was examined under deaerated conditions; NH3 was decomposed to H-2 and nitrogen with a stoichiometric ratio of 3 : 1.
  • Hiroshi Kominami; Satoshi Yamamoto; Kazuya Imamura; Atsuhiro Tanaka; Keiji Hashimoto
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 50 (35) 4558 - 4560 1359-7345 2014 [Refereed]
     
    (2,3-Epoxypropyl) benzene was chemoselectively reduced to allylbenzene along with formation of ketones in alcoholic suspensions of a silver-loaded titanium(IV) oxide photocatalyst at room temperature under atmospheric pressure without the use of reducing gases, and various epoxides were also reduced to the corresponding alkenes.
  • Kazuya Imamura; Yuki Okubo; Tomohiko Ito; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    RSC ADVANCES ROYAL SOC CHEMISTRY 4 (38) 19883 - 19886 2046-2069 2014 [Refereed]
  • Sho Kitano; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS ROYAL SOC CHEMISTRY 16 (24) 12554 - 12559 1463-9076 2014 [Refereed]
     
    Photocatalytic oxidation of benzyl alcohols in aqueous suspensions of rhodium ion-modified titanium(IV) oxide (Rh3+/TiO2) in the presence of O-2 under irradiation of visible light was examined. In the photocatalytic oxidation of benzyl alcohol, benzaldehyde was obtained in a high yield (97%) with >99% conversion of benzyl alcohol. Rh3+/TiO2 photocatalysts having various physical properties were prepared using commercially available TiO2 powders as supporting materials for Rh3+ to investigate the effect(s) of physical properties of TiO2 on photocatalytic activities of Rh3+/TiO2 for selective oxidation. Adsorption properties of benzyl alcohol, benzaldehyde and benzoic acid on TiO2 were also investigated to understand the high benzaldehyde selectivity over the Rh3+/ TiO2 photocatalyst. The reaction mechanism was discussed on the basis of the results of photocatalytic oxidation of various p-substituted benzyl alcohol derivatives.
  • Tanaka, Atsuhiro; Nakanishi, Kousuke; Hamada, Ryosuke; Hashimoto, Keiji; Kominami, Hiroshi
    ACS CATALYSIS AMER CHEMICAL SOC 3 (8) 1886 - 1891 2155-5435 2013/08 [Refereed]
     
    Titanium(IV) oxide (TiO2) having both small platinum (Pt) nanoparticles and large gold (Au) particles without alloying and nanoparticle coagulation was successfully prepared by the combination of traditional photodeposition of Pt and subsequent Au colloid photodeposition onto TiO2-Pt. The Au/TiO2 and Au/TiO2-Pt samples exhibiting strong photoabsorption due to surface plasmon resonance (SPR) of supported Au particles were used for the reduction of hexavalent chromium (Cr6+ in Cr2O72-) in aqueous suspensions under irradiation of visible light from a green light emitting diode (LED). These SPR-type photocatalysts reduced Cr6+ and evolved dioxygen (O-2) with O-2-reduced Cr6+ ratio of 3:4 until consumption of Cr6+, indicating that these SPR-type photocatalysts had the ability to oxidize water (H2O) utilizing visible light (lambda = 540 nm) and that a photocatalytic reaction (2Cr(2)O(7)(2-) + 16H(+) -> 4Cr(3+) + 3O(2) + 8H(2)O) occurred. The Au/TiO2 Pt sample exhibited a reaction rate about twice larger than that of Pt-free Au/TiO2, and the apparent quantum yield reached 1.0% at 550 nm and 0.47% even at 700 nm, indicating that functionalization of Au/TiO2 was successfully achieved by introduction of a Pt cocatalyst. This reaction can be used as a test reaction for evaluation of O-2 evolution ability of photocatalysts because this reaction does not induce irreversible changes in photocatalysts.
  • Atsuhiro Tanaka; Kojirou Fuku; Takuya Nishi; Keiji Hashimoto; Hiroshi Kominami
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 117 (33) 16983 - 16989 1932-7447 2013/08 [Refereed]
     
    Gold (Au) nanoparticles supported on titania (TiO2) and ceria have been applied to a visible-light-responding plasmonic photocatalyst and functionalization of Au/TiO2 photocatalysts with cocatalysts were achieved by separate loading of Au nanoparticles and cocatalyst nanoparticles without alloying and nanoparticle coagulation. Here we report effectiveness of another functionalization by formation of a core-shell structure in photocatalytic reaction induced by SPR of Au/TiO2. Newly functionalized core-shell gold-palladium particles supported on TiO2 (Au@Pd/TiO2) were successfully prepared by using a two-step photodeposition method, and Au@Pd/TiO2 with a shell thickness of 1.0 nm quantitatively converted chlorobenzene and 2-propanol to benzene and acetone under irradiation of visible light. Thickness control of the Pd shell was very important for both a satisfactory cocatalyst effect and absorption due to SPR of Au nanoparticles. The results of this study provide useful information for design of functionalization of plasmonic photocatalysts by formation of a core-shell structure.
  • Sho Kitano; Naoya Murakami; Teruhisa Ohno; Yasufumi Mitani; Yoshio Nosaka; Hiroyuki Asakura; Kentaro Teramura; Tsunehiro Tanaka; Hiroaki Tada; Keiji Hashimoto; Hiroshi Kominami
    Journal of Physical Chemistry C 117 (21) 11008 - 11016 1932-7447 2013/05 [Refereed]
     
    A rhodium(III) ion (Rh3+)-modified TiO2 (Rh 3+/TiO2) photocatalyst, prepared by a simple adsorption method and exhibiting high levels of photocatalytic activity in degradation of organic compounds, was investigated by using X-ray absorption fine structure (XAFS) measurements, (photo)electrochemical measurements, double-beam photoacoustic (DB-PA) spectroscopic measurements, and photoluminescence measurements. Based on the results, the features of the Rh3+ modifier and the working mechanism of the Rh3+/TiO2 photocatalyst are discussed. XAFS measurements revealed that the Rh3+ species were highly dispersed and almost atomically isolated on TiO2. The (photo)electrochemical measurements, DB-PA spectroscopic measurements, and photoluminescence showed a unique bifunction of the Rh3+ modifier as a promoter for O2 reductions and an electron injector to the conduction band of TiO2 for response to visible light. The reasons for the Rh3+/TiO2 photocatalyst exhibiting higher levels of photocatalytic activity than those of TiO2 photocatalysts modified with other metal ions are also discussed on the basis of obtained results. © 2013 American Chemical Society.
  • Yasutomo Sasaki; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 42 (4) 419 - 421 0366-7022 2013/04 [Refereed]
     
    Copper(II) oxide (CuO)-modified indium oxide (In2O3) prepared by physical mixing efficiently mineralized acetone under irradiation of light from a blue LED. The reaction rate increased with additional irradiation of light from a red LED, though no reactions occurred over CuO and In2O3 under irradiation of the red light, indicating that band-gap excitation of CuO contributed to photocatalytic reaction over CuO-In2O3. The effect of CuO modification was also observed in action spectra with and without irradiation of the red light.
  • Atsuhiro Tanaka; Satoshi Sakaguchi; Keiji Hashimoto; Hiroshi Kominami
    ACS CATALYSIS AMER CHEMICAL SOC 3 (1) 79 - 85 2155-5435 2013/01 [Refereed]
     
    Titanium(IV) oxide (TiO2) having both small platinum (Pt) nanoparticles and large gold (Au) particles without alloying and nanoparticle coagulation was successfully prepared by the combination of traditional photodeposition of Pt in the presence of a hole scavenger (PH) and subsequent Au colloid photodeposition in the presence of a hole scavenger (CPH) onto TiO2-Pt. Au particles having an average diameter of 13 nm were fixed on both TiO2 and TiO2-Pt samples without change in the original size of Au particles, and the Au/TiO2 and Au/TiO2 Pt samples exhibited strong photoabsorption around 550 nm as a result of surface plasmon resonance (SPR) of Au to which the large size of Au particles was attributed. Bare TiO2, TiO2-Pt, Au/TiO2, and Au/TiO2-Pt samples were used for photoinduced hydrogen (H-2) formation from 2-propanol in aqueous solutions under irradiation of visible light. The first two samples yielded no H-2 because of no response to visible light, but the latter two formed H-2, indicating that SPR photoabsorption of supported Au particles contributed to the H-2 evolution under irradiation of visible light. The H-2 formation rate of the Au/TiO2-Pt sample was similar to 7-times larger than that of the Pt-free Au/TiO2 sample, indicating that Pt nanoparticles loaded on TiO2 acted effectively as a cocatalyst, that is, as reduction sites for H-2 evolution. The combination of the PH and CPH methods was effective for preparation of Au/TiO2 having other metal cocatalysts (M) including Au, that is, Au/TiO2 Au, and H-2 evolution rates decreased in the order of M; Pt > Pd > Ru > Rh > Au > Ag > Cu > Jr. An inverse correlation between the rate and the hydrogen overvoltage (HOV) of M, that is, it was observed that the higher the HOV, the more difficult it is to reduce protons by photogenerated electrons. Since the amounts of Au and M loaded on TiO2 were changed independently, the effects on photoabsorption and the rate of H-2 evolution were examined. A linear correlation was observed between rate and light absorption due to SPR, suggesting that SPR photoabsorption by Au particles was one of the important factors determining the rate of the H-2 evolution.
  • Tanaka, Atsuhiro; Nishino, Yuri; Sakaguchi, Satoshi; Yoshikawa, Takayuki; Imamura, Kazuya; Hashimoto, Keiji; Kominami, Hiroshi
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 49 (25) 2551 - 2553 1359-7345 2013 [Refereed]
     
    A functionalized plasmonic Au/TiO2 photocatalyst with an Ag co-catalyst was successfully prepared by the combination of two types of photodeposition methods, and it quantitatively converted nitrobenzene and 2-propanol to aniline and acetone under irradiation of visible light.
  • Tanaka, Atsuhiro; Hashimoto, Keiji; Ohtani, Bunsho; Kominami, Hiroshi
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 49 (33) 3419 - 3421 1359-7345 2013 [Refereed]
     
    Nearly second-order (1.87th) light-intensity dependence was observed for photocatalytic oxidation of formic acid in aqueous solutions induced by visible-light surface-plasmon resonance absorption of gold nanoparticles loaded on titanium(IV) oxide prepared by the colloid-photodeposition method using a hole scavenger, indicating that the photocatalytic reaction proceeds through a non-linear process.
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AMER CHEMICAL SOC 134 (35) 14526 - 14533 0002-7863 2012/09 [Refereed]
     
    Au/CeO2 samples with various Au contents were prepared by the multistep (MS) photodeposition method. Their properties including Au particle size, particle dispersion, and photoabsorption were investigated and compared with properties of samples prepared by using the single-step (SS) photodeposition method. The MS- and SS-Au/CeO2 samples were used for selective oxidation of benzyl alcohols to corresponding benzaldehydes in aqueous suspensions under irradiation by visible light from a green LED, and the correlations between reaction rates and physical properties of the MS- and SS-Au/CeO2 samples were investigated. Difference in the two photodeposition methods was reflected in the average size and number of Au nanoparticles, for example, 92 nm and 1.3 x 10(12) (g-Au/CeO2)(-1) for MS photodeposition and 59 nm and 4.8 x 10(12) (g-Au/CeO2)(-1) for SS photodeposition in the case of 1.0 wt % Au samples. Fixation of larger Au particles resulted in strong photoabsorption of the MS-Au/CeO2 samples at around 550 nm due to the surface plasmon resonance, and the Kubelka-Munk function of the photoabsorption linearly increased with increase in Au content up to 2.0 wt %, in contrast to the photoabsorption of SS-Au/CeO2 samples, which was weak and was saturated even at around 0.5 wt %. Due to the strong photoabsorption, the MS-Au/CeO2 samples exhibited reaction rates approximately twice larger than those of SS-Au/CeO2 samples with the same Au contents, and apparent quantum efficiency of MS-Au/CeO2 reached 4.9% at 0.4 mW cm(-2). Linear correlations were observed between reaction rates (r) and surface area of Au nanoparticles (S) in both MS- and SS-Au/CeO2, samples, though the two slopes of r versus S plots were different, suggesting that oxidation of benzyl alcohol occurred on the Au surface and that S was one of the important factors controlling the reaction rate. Photocatalytic oxidation of benzyl alcohol having an amino group revealed that the Au/CeO2 photocatalyst exhibited high chemoselectivity toward the hydroxyl group of alcohol, i.e, the Au/CeO2 photocatalyst almost quantitatively converted aminobenzyl alcohol to aminobenzaldehyde with 99% yield.
  • Atsuhiro Tanaka; Asako Ogino; Moe Iwaki; Keiji Hashimoto; Akira Ohnuma; Fumiaki Amano; Bunsho Ohtani; Hiroshi Kominami
    LANGMUIR AMER CHEMICAL SOC 28 (36) 13105 - 13111 0743-7463 2012/09 [Refereed]
     
    Colloidal gold (Au) nanoparticles were prepared and successfully loaded on titanium(IV) oxide (TiO2) without change in the original particle size using a method of colloid photo-deposition operated in the presence of a hole scavenger (CPH). The prepared Au nanoparticles supported on TiO2 showed strong photoabsorption at around 550 nm due to surface plasmon resonance (SPR) of Au and exhibited a photocatalytic activity in mineralization of formic acid in aqueous suspensions under irradiation of visible light (>ca. 520 nm). A linear correlation between photocatalytic activity and the amount of Au loaded, that is, the number of Au nanoparticles, was observed, indicating that the activity of Au/TiO2 plasmonic photocatalysts can be controlled simply by the amount of Au loading using the CPH method and that the external surface area of Au nanoparticles is a decisive factor in mineralization of formic acid under visible light irradiation. Very high reaction rates were obtained in samples with 5 wt % Au or more, although the rate tended to be saturated. The CPH method can be widely applied for loading of Au nanoparticles on various TiO2 supports without change in the original size independent of the TiO2 phase. The rate of CO2 formation also increased linearly with increase in the external surface area of Au. Interestingly, the TiO2 supports showed different slopes of the plots. The slope is important for selection of TiO2 as a material supporting colloidal Au nanoparticles.
  • Siyu Yao; Yuan Yuan; Chaoxian Xiao; Weizhen Li; Yuan Kou; Paul J. Dyson; Ning Yan; Hiroyuki Asakura; Kentaro Teramura; Tsunehiro Tanaka
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 116 (28) 15076 - 15086 1932-7447 2012/07 [Refereed]
     
    The mechanism of formation of rhodium nanocubes in the presence of tetradecyltrimethylammonium bromide and polyvinylpyrrolidone in ethylene glycol was studied in situ by XAFS, in conjunction with other ex situ techniques including MALDI-TOF MS, XRD, TEM, and UV-vis spectroscopy. Detailed analysis of the XAFS data reveals that Rh nanocubes are formed in four distinct stages comprising ligand substitution., slow nucleation, continued nucleation/fast growth of nuclei, and shape correction, which were corroborated by the other techniques. All the main types of Rh species and the chemical transformations taking place at each stage were clearly identified. In particular, combined XAFS and MAILD-TOF MS techniques provide compelling evidence that a Rh4 cluster acts as the critical nuclei species for the formation of the nanocubes. Other key findings include (1) RhBr3 is the true precursor of the Rh nanocubes, (2) the consumption rate of the precursor appears to follow Finke-Watzky type kinetics, and (3) non-cubic-shaped nanoparticles can be transformed into nanocubes, even if all the precursor has been exhaust. These results provide a clear understanding of the formation mechanism of the rhodium nanocubes, which is essential for rational design of nanoparticles.
  • Atsuhiro Tanaka; Satoshi Sakaguchi; Keiji Hashimoto; Hiroshi Kominami
    CATALYSIS SCIENCE & TECHNOLOGY ROYAL SOC CHEMISTRY 2 (5) 907 - 909 2044-4753 2012 [Refereed]
     
    Au/TiO2 samples exhibiting stronger photoabsorption at around 550 nm due to surface plasmon resonance were prepared by using a multi-step photodeposition method and the samples exhibited higher levels of activity for H-2 production from various compounds such as 2-propanol, ethanol and ammonia in aqueous suspensions under visible light irradiation.
  • Green LED responding photocatalytic oxidation of alcohols with Au/CeO2
    A. Tanaka; K. Hashimoto; H. Kominami
    SYNFACTS (8) 1377  2012
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMCATCHEM WILEY-BLACKWELL 3 (10) 1619 - 1623 1867-3880 2011/10 [Refereed]
     
    Gold and copper nanoparticles supported on cerium(IV) oxide (CeO(2)) powder, which were prepared using a simple multistep photodeposition method, showed strong absorptions at around lambda = 620 nm attributed to the surface plasmon resonance of Cu-Au nanoparticles and exhibited a higher level of activity than that of Au/CeO(2) in the mineralization of organic acids (formic acid and acetic acid) in aqueous suspensions under light irradiation (lambda = 640 nm) from a red light-emitting diode. The action spectrum in the mineralization of formic acid indicates that this mineralization involved a photoinduced step by the SPR of Cu-Au supported on CeO(2). The apparent quantum efficiency reached 7.5% at lambda = 625 nm and 5.2% even at lambda = 700 nm.
  • Hiroshi Kominami; Atsuhiro Tanaka; Keiji Hashimoto
    APPLIED CATALYSIS A-GENERAL ELSEVIER SCIENCE BV 397 (1-2) 121 - 126 0926-860X 2011/04 [Refereed]
     
    Gold (Au) nanoparticles supported on cerium(IV) oxide (CeO2) were prepared by the photodeposition method. These samples showed strong absorption at around 550 nm due to localized surface plasmon resonance (LSPR) of Au. These Au/CeO2 samples were used for mineralization of organic acids (formic acid, oxalic acid and acetic acid) in the aqueous suspensions under irradiation of visible light (>ca. 520 nm) and three acids were stoichiometrically decomposed to carbon dioxide. Apparent activation energy for mineralization of formic acid was very small (2.4 kJ mol(-1)) compared with those by thermocatalytic reactions, and the action spectrum was in good agreement with the photoabsorption spectrum, indicating that the rate-determining step in mineralization of organic acids in the irradiated Au/CeO2 system was different from the thermal activation process and that this mineralization involved a photoinduced step by LSPR of Au supported on CeO2. When a green light-emitting diode (center wavelength = 530 nm) was used as the light source of visible light, mineralization of formic acid also occurred. Apparent quantum efficiency of formic acid mineralization increased with decrease in the intensity of the green light and reached 4.7% at 0.4 mW cm(-2). (C) 2011 Elsevier B.V. All rights reserved.
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 40 (4) 354 - 356 0366-7022 2011/04 [Refereed]
     
    Photocatalytic activity of cerium(IV) oxide (CeO2) particles in decomposition of acetic acid in aqueous suspension was examined under irradiation of visible light. Acetic acid was decomposed to carbon dioxide (CO2) and the rate of CO2 formation was increased by loading of 0.1 wt% cocatalysts (Pt, Au, Rh, Ru, Pd, Ag, Cu, and Ir) on CeO2 by photodeposition. Cocatalysts showed almost the same levels of enhancement of CO2 evolution, i.e., Ag/CeO2 and Cu/CeO2 exhibited rates similar to that of Pt/CeO2. The action spectrum revealed that decomposition of acetic acid was induced by photoabsorption of CeO2.
  • Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi Kominami
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 47 (37) 10446 - 10448 1359-7345 2011 [Refereed]
     
    Gold nanoparticles supported on cerium(IV) oxide powder showing strong absorption at around 550 nm due to surface plasmon resonance oxidized aromatic alcohols to corresponding aldehydes almost quantitatively in an aqueous suspension under irradiation of green light.
  • Hiroshi Kominami; Atsuhiro Tanaka; Keiji Hashimoto
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 46 (8) 1287 - 1289 1359-7345 2010 [Refereed]
     
    Gold nanoparticles supported on cerium(IV) oxide powder showed strong absorption at around 550 nm due to localized surface plasmon resonance of Au and exhibited a higher level of activity than other Au-supporting samples in mineralization of organic acids in aqueous suspensions under irradiation of visible light (>ca. 520 nm).

MISC

Awards & Honors

  • 2023/03 プラズモニック化学研究会 若手奨励賞 最優秀賞
     機能化したプラズモニック光触媒による化学変換
  • 2014/03 第113回触媒討論会 若手優秀講演賞（討論会B）
  • 2013/12 日本エネルギー学会関西支部 第58回研究発表会、石油学会関西支部 第22回研究発表会 優秀研究賞
  • 2011/11 第21回キャラクタリゼーション講習会 最優秀賞受賞
  • 2010/10 触媒学会西日本支部 優秀研究賞
  • 2010/07 TOCAT6 Best Presentation Award

Research Grants & Projects

  • 光照射波長によって電子移動・化学選択性が変化するプラズモニック光触媒の創製と物質変換反応
    JST さきがけ：
    Date (from‐to) : 2018/10 -2022/03
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2017/04 -2020/03 
    Author : TANAKA ATSUHIRO
     
    Many efforts have been devoted to synthesis of photocatalysts that respond to visible light. In previous study, Au nanoparticles supported on metal oxide have been applied as a new type of photocatalysts responding to visible light. We found that action spectra in photocatalytic reactions over Au/metal oxide were in good agreement with their absorption spectra, which suggested that photocatalytic reactions were induced by photoabsorption due to surface plasmon resonance (SPR) of the supported Au nanoparticles. In this study, we reported (1) the change in the shape of Au particles loaded on TiO2 and the redshift of SPR of the Au particles and (2) the selective oxidation of alcohols under irradiation of visible light in aqueous suspensions of Au/TiO2 before and after post-calcination. In addition, we examined H2 evolution over Au/MOx (CeO2:Sr and Ta2O5) without a Pt cocatalyst under visible light irradiation and found that Au/MOx produced H2 without the aid of a cocatalyst.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2015/04 -2017/03 
    Author : TANAKA Atsuhiro
     
    Many efforts have been devoted to synthesis of photocatalysts that respond to visible light. In previous study, Au nanoparticles supported on metal oxide have been applied as a new type of photocatalysts responding to visible light. we found that action spectra in photocatalytic reactions over Au/metal oxide were in good agreement with their absorption spectra, which suggested that photocatalytic reactions were induced by photoabsorption due to surface plasmon resonance (SPR) of the supported Au nanoparticles. In this study, we examined control of absorption due to SPR by modification of Au nanoparticles supported on metal oxide with Ag and Cu. These samples were active for mineralization of formic acid and selective oxidation of alcohols to carbonyl compounds under visible-light irradiation and exhibited the best performance when irradiated by light overlapping with their SPR.
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 2013/04 -2015/03 
    Author : 田中 淳皓
     
    本研究では，太陽光エネルギーを最大限に利用した光触媒の構築のために，金（Au）の表面プラズモン共鳴（SPR）を可視光光触媒反応への応用を目的としている．報告者はこれまでに、AuのSPR誘起型光触媒の光触媒反応を積極的に検討してきた．種々の化学反応への応用，それぞれの化学反応に適応した材料の創出を考えた．交付申請書の「研究実施計画」には「まず，Au粒子担持酸化物を調製し，SPR光触媒の種々の化学反応への応用について検討する．」と記載した． ＜具体的内容＞ 酸化反応（水の酸化）と還元反応（プロトンからの水素生成）をそれぞれ達成することができる新たなSPR光触媒系としてPt/Au/WO3の合成に成功し，その成果を第114回触媒討論会で発表した．さらに，論文として，J. Am. Chem. Soc.に掲載された．他方で，多層構造を有する金属ナノ粒子内包型光触媒の創製を目指したが，金属－酸化物内包構造には至っていない．その前段階として，上記に示した金属－金属内包構造を達成することができ，Catal. Sci. Technol.への論文掲載に至った． ＜意義・重要性＞ 以上の結果より、はじめのPt/Au/WO3においてはAuのSPR粒子とWO3のバンドギャップ励起を用いた光触媒を創生することができた．この光触媒ではAu粒子状にPt粒子を担持したPt/Au粒子上でプロトンの還元反応，WO3上で水の酸化反応が起こっていると予想される．これにより，これまで問題となっていたSPR光触媒の低活性をWO3の半導体光触媒で補えたといえる．この研究中に両者の光機能を補助光照射アクションスペクトルにより達成することができた．また，Au上へのPt粒子の生成は今後，申請者が目指している多層構造を有するSPR光触媒の創生につながるといえる．

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