研究者詳細 - 山方　啓

論文 - 山方　啓

分割表示 227 件中 81 - 100 件目／全件表示 >>

Time-Resolved Spectroscopy of Defect-Induced Effects on Photocarrier Dynamics in SrTiO3 Powder

Akira Yamakata, Kosaku Kato

ECS Meeting Abstracts {MA}2020-02 ( 56 ) 3873 - 3873 2020年11月

Optically Transparent Colloidal Dispersion of Titania Nanoparticles Storable for Longer than One Year Prepared by Sol/Gel Progressive Hydrolysis/Condensation 査読

Keito Sano, Fazalurahman Kuttassery, Tetsuya Shimada, Tamao Ishida, Shinsuke Takagi, Bunsho Ohtani, Akira Yamakata, Tetsuo Honma, Hiroshi Tachibana, Haruo Inoue

ACS Applied Materials & Interfaces 12 ( 40 ) 44743 - 44753 2020年10月

掲載種別：研究論文（学術雑誌）出版者・発行元：American Chemical Society ({ACS})

Copyright © 2020 American Chemical Society. The molecular catalyst sensitized system (MCSS), where an excited molecular catalyst adsorbed on a semiconductor such as TiO2 injects electrons to the conduction band of the semiconductor leading to hydrogen evolution/CO2 reduction coupled with an oxidation of water on the molecular catalyst, has been one of the most probable candidates in the approach to artificial photosynthesis. For a full utilization of visible light, however, a serious light scattering of the aqueous suspension of TiO2 in the visible region, which is generally experienced, should be avoided. Here, we report a preparation of optically transparent colloidal dispersion of TiO2 by the sol/gel reaction of TiCl4 through progressive hydrolysis/condensation under the basic condition without any calcination processes. The TiO2 nanoparticles (TiO2(NPs)) obtained were characterized as an amorphous particle (∼10-15 nm) having a microcrystal domain of anatase within several nm by XRD, Raman spectroscopies, XRF, XAFS, TG/DTA, and HRTEM, respectively. The energy-resolved distribution of carrier electron traps in TiO2(NPs) as a fingerprint of TiO2 was characterized through reversed double-beam photo-acoustic spectroscopy to have a close similarity to that of TiO2(ST-01) as well as the observation of carrier traps by transient absorption spectroscopy. Though the powder TiO2(NP) itself was not dispersed well in aqueous solution, the wet TiO2(NPs) as prepared before being dried up provided a completely transparent aqueous dispersion under the acidic condition (1 M HCl). Addition of methanol enabled the colloidal dispersion (TiO2(NPs, MeOH/H2O, 0.1 M HCl)) to keep the optical transparency for longer than 1 year (550 days), which is the first example of TiO2 dispersion storable for such a long period. TiO2(NPs, MeOH/H2O) exhibited a moderate photocatalytic reactivity of H2 evolution with a quantum yield of ∼2.6% upon 365 nm light irradiation. An optically transparent thin film of TiO2(NPs, MeOH/H2O) was also successfully prepared on a glass plate to exhibit an enhanced hydrophilicity upon UV light irradiation.

DOI： 10.1021/acsami.0c12951

Scopus

PubMed

researchmap

Investigation on the highly active SrTiO3 photocatalyst toward overall H2O splitting by doping Na ion 査読

Junzhe Jiang, Kosaku Kato, Hirotaka Fujimori, Akira Yamakata, Yoshihisa Sakata

Journal of Catalysis 390 81 - 89 2020年8月

Synthesis of Three-Layer Perovskite Oxynitride K2Ca2Ta3O9N·2H2O and Photocatalytic Activity for H2 Evolution under Visible Light 査読

Ya Tang, Kosaku Kato, Takayoshi Oshima, Hiroto Mogi, Akinobu Miyoshi, Kotaro Fujii, Kei-ichi Yanagisawa, Koji Kimoto, Akira Yamakata, Masatomo Yashima, Kazuhiko Maeda

Inorganic Chemistry 59 ( 15 ) 11122 - 11128 2020年8月

Heteroatom Dopants Promote Two‐Electron O2 Reduction for Photocatalytic Production of H2O2 on Polymeric Carbon Nitride 査読

Peng Zhang, Yawen Tong, Yong Liu, Junie Jhon, M. Vequizo, Hongwei Sun, Can Yang, Akira Yamakata, Fengtao Fan, Wei Lin, Xinchen Wang, Wonyong Choi

Angewandte Chemie International Edition 59 16209 - 16217 2020年6月

Efficient photocatalytic hydrogen evolution on single-crystalline metal selenide particles with suitable cocatalysts 査読

Shanshan Chen, Junie Jhon, M. Vequizo, Takashi Hisatomi, Mamiko Nakabayashi, Lihua Lin, Zheng Wang, Akira Yamakata, Naoya Shibata, Tsuyoshi Takata, Taro Yamada, Kazunari Domen

Chemical Science 11 ( 25 ) 6436 - 6441 2020年4月

Activation of a Pt-loaded Pb<inf>2</inf>Ti<inf>2</inf>O<inf>5.4</inf>F<inf>1.2</inf> photocatalyst by alkaline chloride treatment for improved H<inf>2</inf> evolution under visible light 査読

Wakayama, H., Kato, K., Kashihara, K., Uchiyama, T., Miyoshi, A., Nakata, H., Lu, D., Oka, K., Yamakata, A., Uchimoto, Y., Maeda, K.

Journal of Materials Chemistry A 8 ( 18 ) 9099 - 9108 2020年4月

How g-C3N4 Works and Is Different from TiO2 as an Environmental Photocatalyst: Mechanistic View

Jonghun Lim, Hyejin Kim, Jihee Park, Gun-Hee Moon, Junie Jhon M Vequizo, Akira Yamakata, Jinwoo Lee, Wonyong Choi

Environmental science & technology 54 ( 1 ) 497 - 506 2020年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NLM (Medline)

Graphitic carbon nitride (CN) as a popular visible light photocatalyst needs to be better understood for environmental applications. The behaviors of CN as an environmental photocatalyst were systematically studied in comparison with a well-known TiO2 photocatalyst. The two photocatalysts exhibit different photocatalytic oxidation (PCO) behaviors and dependences on the experimental conditions (e.g., pH, Pt loading, and the kind of organic substrate and scavenger). The PCO of organic substrates was significantly enhanced by loading Pt on TiO2 under UV light (λ &gt
320 nm), whereas Pt-CN exhibited a lower PCO activity than bare CN under visible light (λ &gt
420 nm). While the presence of Pt enhances the charge separation in both TiO2/UV and CN/visible light systems (confirmed by transient IR absorption spectroscopic analysis), the opposite effects of Pt are ascribed to the different mechanisms of •OH generation in the two photocatalytic systems. The negative effect of Pt on CN is ascribed to the fact that Pt catalytically decomposes in situ-generated H2O2 (a main precursor of OH radical), which hinders •OH production. The production of OH radicals on CN is favored only at acidic pH but 1O2 generation is dominant in alkaline pH. The pH-dependent behaviors of reactive oxygen species generation on CN were confirmed by electron paramagnetic resonance spin trap measurements.

DOI： 10.1021/acs.est.9b05044

Scopus

PubMed

researchmap

Identification of Individual Electron- and Hole-Transfer Kinetics at CoOx/BiVO4/SnO2 Double Heterojunctions 査読

Akira Yamakata, Chandana Sampath, Kumara Ranasinghe, Naruki Hayashi, Kosaku Kato, Junie Jhon, M. Vequizo

ACS Applied Energy Materials 3 ( 1 ) 1207 - 1214 2020年1月

時間分解分光測定による粉末欠陥への光励起キャリアー捕捉過程と光触媒活性に及ぼす影響査読

山方啓* and Junie Jhon M. Vequizo,

触媒【特集号: 触媒設計を拓く欠陥構造のキャラクタリゼーション】 62 ( 1 ) 22 - 28 2020年1月

Synthesis of Copolymerized Carbon Nitride Nanosheets from Urea and 2-Aminobenzonitrile for Enhanced Visible-Light CO2 Reduction with a Ruthenium(II) Complex Catalyst 査読

Kengo Shibata, Kosaku Kato, Constantine Tsounis, Tomoki Kanazawa, Daling Lu, Shunsuke Nozawa, Akira Yamakata, Osamu Ishitani, Kazuhiko Maeda

Solar RRL 4 ( 8 ) 1900461 2020年1月

How g-C3N4 Works and Is Different from TiO2 as Environmental Photocatalyst: Mechanistic View 査読国際誌

Jonghun Lim, Hyejin Kim, Jihee Park, Gun-hee Moon, Junie Jhon, M. Vequizo, Akira Yamakata, Jinwoo Lee, Wonyong Choi

Environmental Science & Technology 54 ( 1 ) 497 - 506 2020年1月

Enhancement of UV-responsive photocatalysts aided by visible-light responsive photocatalysts: Role of WO<inf>3</inf> for H<inf>2</inf> evolution on CuCl 査読

Takagi, M., Kawaguchi, M., Yamakata, A.

Applied Catalysis B: Environmental 263 118333 - 118333 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier {BV}

WO3 is one of the most popular materials for visible-light photocatalysts. However, its conduction band minimum is too low for water reduction. Here, we found that WO3 can assist water reduction by using visible light in a CuCl2 aqueous solution. Photoirradiation of WO3 in CuCl2 reduces Cu2+ to form indissoluble Cud adducts, and as-produced CuCl/WO3 was active for H-2 evolution under UV-light. This composite has very low reactivity under visible light ( > 400 nm), but visible-light assisted H-2 evolution was observed with simultaneous irradiation with UV light: the activity was increased similar to 1.7 fold. Transient absorption measurements revealed that Z-schematic recombination initially takes place between photogenerated electrons in WO3 and holes in CuCl. As a result, the lifetime of electrons in Cud was increased, enhancing H2 evolution. These results demonstrate that inactive narrow-band gap materials can be used to enhance the activity of wide-band gap materials under sunlight illumination.

DOI： 10.1016/j.apcatb.2019.118333

Web of Science

Scopus

researchmap

Cobalt Aluminate Spinel as a Cocatalyst for Photocatalytic Oxidation of Water: Significant Hole-Trapping Effect 査読

Kanazawa, T., Kato, K., Yamaguchi, R., Uchiyama, T., Lu, D., Nozawa, S., Yamakata, A., Uchimoto, Y., Maeda, K.

ACS Catalysis 10 ( 9 ) 4960 - 4966 2020年

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）出版者・発行元：American Chemical Society ({ACS})

Here we show that nanoparticulate CoAl2O4 spinel serves as an efficient cocatalyst for photocatalytic oxidation of water. The O-2 evolution activity of CoAl2O4/g-C3N4 from an aqueous solution of AgNO3 under visible light irradiation was similar to 10 times that of unmodified g-C3N4 and also exceeded that of an analogue modified with a well-known Co3O4 cocatalyst for each optimal preparation condition. Transient absorption spectroscopy indicated that the CoAl2O4 cocatalyst with Co2+ as the main cobalt species at the A site of the spinel possessed better hole-capturing properties than the Co3O4 cocatalyst, which was the main reason for the improved water-oxidation performance.

DOI： 10.1021/acscatal.0c00944

Web of Science

Scopus

researchmap

Defect-Induced Acceleration and Deceleration of Photocarrier Recombination in SrTiO<inf>3</inf>Powders 査読

Kato, K., Yamakata, A., Yamakata, A.

Journal of Physical Chemistry C 124 ( 20 ) 11057 - 11063 2020年

Synthesis of three-component C<inf>3</inf>N<inf>4</inf>/rGO/C-TiO<inf>2</inf> photocatalyst with enhanced visible-light responsive photocatalytic deNO<inf>x</inf> activity 査読

Noda, C., Asakura, Y., Shiraki, K., Yamakata, A., Yin, S.

Chemical Engineering Journal 390 124616 - 124616 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier {BV}

In order to realize high efficiency photocatalysis deNO(x) effect, a homogeneous three-component photocatalyst, C3N4/rGO/C-TiO2 was successfully synthesized by an in situ synthesis method. First, C3N4/rGO composite was prepared to increase the contact surface between them. Then, C-TiO2 was crystallized on the surface of the C3N4/rGO to obtain relatively dispersed C-TiO2 nanoparticles on the C3N4/rGO. The as-prepared photocatalyst was evaluated by NO removal ratio under weak visible and UV LED light irradiation. C3N4/rGO/C-TiO2 was compared with sample prepared by simple mixing of C3N4, rGO and C-TiO2 within a solution. As a result, sample prepared by in situ synthesis exhibited the highest photocatalytic activity, together with high apparent quantum efficiency. The transient absorption measurement clarified that the composite photocatalyst possessed longer carrier lifetime if compared to that of each component material, resulted to its higher photocatalytic activity. The three-component photocatalyst is thought to have shown enhancement in photocatalytic activity by Z-scheme mechanism with rGO as an electron mediator to improve the performance of Z-scheme.

DOI： 10.1016/j.cej.2020.124616

Web of Science

Scopus

researchmap

Nano vs. bulk rutile TiO2:N,F in Z-scheme overall water splitting under visible light 査読

Akinobu Miyoshi, Kosaku Kato, Toshiyuki Yokoi, Jan J. Wiesfeld, Kiyotaka Nakajima, Akira Yamakata, Kazuhiko Maeda

Journal of Materials Chemistry A 8 ( 24 ) 11996 - 12002 2020年

Enhancement of photoelectrochemical activity of TiO<inf>2</inf> electrode by particulate/dense double-layer formation 招待査読

Hayashi, N., Kato, K., Yamakata, A.

The Journal of chemical physics 152 ( 24 ) 241101 - 241101 2020年

Fe/Ru Oxide as Versatile and Effective Cocatalyst for Boosting Z-Scheme Water Splitting: Suppressing Undesirable Backward Electron Transfer 査読

Akinobu Nakada, Hajime Suzuki, Junie Jhon, M. Vequizo, Kanta Ogawa, Masanobu Higashi, Akinori Saeki, Akira Yamakata, Hiroshi Kageyama, Ryu Abe

ACS Applied Materials & Interfaces 11 ( 49 ) 45606 - 45611 2019年11月

Crucial impact of reduction on the photocarriers dynamics on SrTiO3 powders studied by transient absorption spectroscopy 査読

Junie Jhon, M. Vequizo, Shunta Nishioka, Junji Hyodo, Yoshihiro Yamazaki, Kazuhiko Maeda, Akira Yamakata

J. Mater. Chem. A 7 ( 45 ) 26139 - 26146 2019年10月

　前のページ - 次のページ　

<山方 啓>

論文 - 山方 啓

<山方　啓>

論文 - 山方　啓