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5. A Molecular Z‐Scheme Artificial Photosynthetic System Under the Bias‐Free Condition for CO2 Reduction Coupled with Two‐electron Water Oxidation: Photocatalytic Production of CO/HCOOH and H2O2

Author

Kuttassery, Fazalurahman, primary, Ohsaki, Yutaka, additional, Thomas, Arun, additional, Kamata, Ryutaro, additional, Ebato, Yosuke, additional, Kumagai, Hiromu, additional, Nakazato, Ryosuke, additional, Sebastian, Abin, additional, Mathew, Siby, additional, Tachibana, Hiroshi, additional, Ishitani, Osamu, additional, and Inoue, Haruo, additional

Published
2023
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6. A Molecular Z‐Scheme Artificial Photosynthetic System Under the Bias‐Free Condition for CO₂ Reduction Coupled with Water Oxidation: Photocatalytic Production of CO/HCOOH and H₂O₂

Author

Kuttassery, Fazalurahman, primary, Ohsaki, Yutaka, additional, Thomas, Arun, additional, Kamata, Ryutaro, additional, Ebato, Yosuke, additional, Kumagai, Hiromu, additional, Nakazato, Ryosuke, additional, Sebastian, Abin, additional, Mathew, Siby, additional, Tachibana, Hiroshi, additional, Ishitani, Osamu, additional, and Inoue, Haruo, additional

Published
2023
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7. A Molecular Z‐Scheme Artificial Photosynthetic System Under the Bias‐Free Condition for CO2 Reduction Coupled with Two‐electron Water Oxidation: Photocatalytic Production of CO/HCOOH and H2O2.

Author

Kuttassery, Fazalurahman, Ohsaki, Yutaka, Thomas, Arun, Kamata, Ryutaro, Ebato, Yosuke, Kumagai, Hiromu, Nakazato, Ryosuke, Sebastian, Abin, Mathew, Siby, Tachibana, Hiroshi, Ishitani, Osamu, and Inoue, Haruo

Subjects
OXIDATION of water, PHOTOCATALYTIC oxidation, OXIDATION-reduction reaction, ARTIFICIAL photosynthesis, TIN oxides
Abstract

Bio‐inspired molecular‐engineered systems have been extensively investigated for the half‐reactions of H2O oxidation or CO2 reduction with sacrificial electron donors/acceptors. However, there has yet to be reported a device for dye‐sensitized molecular photoanodes coupled with molecular photocathodes in an aqueous solution without the use of sacrificial reagents. Herein, we will report the integration of SnIV‐ or AlIII‐tetrapyridylporphyrin (SnTPyP or AlTPyP) decorated tin oxide particles (SnTPyP/SnO2 or AlTPyP/SnO2) photoanode with the dye‐sensitized molecular photocathode on nickel oxide particles containing [Ru(diimine)3]2+ as the light‐harvesting unit and [Ru(diimine)(CO)2Cl2] as the catalyst unit covalently connected and fixed within poly‐pyrrole layer (RuCAT‐RuC2‐PolyPyr‐PRu/NiO). The simultaneous irradiation of the two photoelectrodes with visible light resulted in H2O2 on the anode and CO, HCOOH, and H2 on the cathode with high Faradaic efficiencies in purely aqueous conditions without any applied bias is the first example of artificial photosynthesis with only two‐electron redox reactions. [ABSTRACT FROM AUTHOR]

Published
2023
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8. A Molecular Z‐Scheme Artificial Photosynthetic System Under the Bias‐Free Condition for CO2 Reduction Coupled with Two‐electron Water Oxidation: Photocatalytic Production of CO/HCOOH and H2O2.

Author

Kuttassery, Fazalurahman, Ohsaki, Yutaka, Thomas, Arun, Kamata, Ryutaro, Ebato, Yosuke, Kumagai, Hiromu, Nakazato, Ryosuke, Sebastian, Abin, Mathew, Siby, Tachibana, Hiroshi, Ishitani, Osamu, and Inoue, Haruo

Subjects
OXIDATION of water, PHOTOCATALYTIC oxidation, OXIDATION-reduction reaction, ARTIFICIAL photosynthesis, TIN oxides
Abstract

Bio‐inspired molecular‐engineered systems have been extensively investigated for the half‐reactions of H2O oxidation or CO2 reduction with sacrificial electron donors/acceptors. However, there has yet to be reported a device for dye‐sensitized molecular photoanodes coupled with molecular photocathodes in an aqueous solution without the use of sacrificial reagents. Herein, we will report the integration of SnIV‐ or AlIII‐tetrapyridylporphyrin (SnTPyP or AlTPyP) decorated tin oxide particles (SnTPyP/SnO2 or AlTPyP/SnO2) photoanode with the dye‐sensitized molecular photocathode on nickel oxide particles containing [Ru(diimine)3]2+ as the light‐harvesting unit and [Ru(diimine)(CO)2Cl2] as the catalyst unit covalently connected and fixed within poly‐pyrrole layer (RuCAT‐RuC2‐PolyPyr‐PRu/NiO). The simultaneous irradiation of the two photoelectrodes with visible light resulted in H2O2 on the anode and CO, HCOOH, and H2 on the cathode with high Faradaic efficiencies in purely aqueous conditions without any applied bias is the first example of artificial photosynthesis with only two‐electron redox reactions. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Hybrid photocatalyst constructed using polymerized metal complexes and semiconductor powders for photocatalytic carbon dioxide reduction

Author

Yamazaki, Yasuomi, Maruyama, Riku, Kumagai, Hiromu, Maeda, Kazuhiko, and Tsubomura, Taro

Abstract

Hybrid photocatalysts prepared by the adsorption of metal complexes on semiconductors via anchoring groups are among notable photocatalysts for selective CO2reduction using abundant electron donors. However, their photocatalytic activities are limited by their low adsorption amounts and strength. In this study, we demonstrate the reductive polymerization of vinyl groups in metal complexes triggered by excited electrons on semiconductors as a new immobilization method. This approach significantly enhanced the adsorption amount and durability, thus increasing the photocatalytic performance.Hybrid photocatalysts constructed with metal complexes and semiconductors are notable photocatalysts for selective CO2reduction using abundant electron donors. We herein report a new hybridization method using reductive polymerization of vinyl groups in metal complexes triggered by excited electrons on semiconductors. This approach significantly enhanced the adsorption amount and durability of metal complexes, thus increasing the photocatalytic performance.

Published
2024
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21. Photocatalytic Systems for CO2Reduction: Metal-Complex Photocatalysts and Their Hybrids with Photofunctional Solid Materials

Author

Kumagai, Hiromu, Tamaki, Yusuke, and Ishitani, Osamu

Abstract

Photocatalytic CO2reduction is a critical objective in the field of artificial photosynthesis because it can potentially make a total solution for global warming and shortage of energy and carbon resources. We have successfully developed various highly efficient, stable, and selective photocatalytic systems for CO2reduction using transition metal complexes as both photosensitizers and catalysts. The molecular architectures for constructing selective and efficient photocatalytic systems for CO2reduction are discussed herein. As a typical example, a mixed system of a ring-shaped Re(I) trinuclear complex as a photosensitizer and fac-[Re(bpy)(CO)3{OC2H4N(C2H4OH)2}] as a catalyst selectively photocatalyzed CO2reduction to CO with the highest quantum yield of 82% and a turnover number (TON) of over 600. Not only rare and noble metals but also earth abundant ones, such as Mn(I), Cu(I), and Fe(II) can be used as central metal cations. In the case using a Cu(I) dinuclear complex as a photosensitizer and fac-Mn(bpy)(CO)3Br as a catalyst, the total formation quantum yield of CO and HCOOH from CO2was 57% and TONCO+HCOOHexceeded 1300.

Published
2022
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26. Solar Water Oxidation by a Visible-Light-Responsive Tantalum/Nitrogen-Codoped Rutile Titania Anode for Photoelectrochemical Water Splitting and Carbon Dioxide Fixation

Author

Nakada, Akinobu, primary, Uchiyama, Tomoki, additional, Kawakami, Nozomi, additional, Sahara, Go, additional, Nishioka, Shunta, additional, Kamata, Ryutaro, additional, Kumagai, Hiromu, additional, Ishitani, Osamu, additional, Uchimoto, Yoshiharu, additional, and Maeda, Kazuhiko, additional

Published
2018
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27. Front Cover: Solar Water Oxidation by a Visible-Light-Responsive Tantalum/Nitrogen-Codoped Rutile Titania Anode for Photoelectrochemical Water Splitting and Carbon Dioxide Fixation (ChemPhotoChem 1/2019)

Author

Nakada, Akinobu, primary, Uchiyama, Tomoki, additional, Kawakami, Nozomi, additional, Sahara, Go, additional, Nishioka, Shunta, additional, Kamata, Ryutaro, additional, Kumagai, Hiromu, additional, Ishitani, Osamu, additional, Uchimoto, Yoshiharu, additional, and Maeda, Kazuhiko, additional

Published
2018
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28. Durable photoelectrochemical CO2 reduction with water oxidation using a visible-light driven molecular photocathode.

Author

Kamata, Ryutaro, Kumagai, Hiromu, Yamazaki, Yasuomi, Higashi, Masanobu, Abe, Ryu, and Ishitani, Osamu

Abstract

Photocatalytic reduction of CO2 using water as a reductant and visible light as the energy source is an important target in artificial photosynthesis. In this study, we report a highly stable photoelectrochemical CO2 reduction involving a new molecular photocathode comprising a NiO electrode and polymerized complexes of the Ru(II) photosensitizer and Ru(II) catalyst (NiO/PRu-poly-Ru-RuCAT1). CO and HCOOH were stably and selectively produced for over 100 h under visible light irradiation and a low bias. The turnover number of CO2 reduction products exceeded 1200, which represents the highest durability reported for photoelectrochemical reactions using molecular photocathodes. Moreover, a connected system of the NiO/PRu-poly-Ru-RuCAT1 molecular photocathode and a CoOx/BiVO4 photoanode suitable for water oxidation facilitated stable CO2 reduction with water as an electron donor and visible light as the energy source, with no bias for over 24 h. An energy conversion efficiency of 1.7 × 10−2% was obtained, which is the highest value reported for visible light driven systems utilizing a molecular photocatalyst for CO2 reduction with water as the reductant. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Inorganic assembly catalysts for artificial photosynthesis : general discussion

Author

Kumagai, Hiromu, Hammarstrom, Leif, Whang, Dong Ryeol, Shinohara, Yuki, Martinez, Jose, Karlsson, Joshua, Summers, Peter, Windle, Christopher D., Kodera, Masanori, Cogdell, Richard, Tolod, Kristine Rodulfo, Apaydin, Dogukan Hazar, Fujita, Etsuko, Kibler, Alexander, Fan, Fengtao, Gibson, Elizabeth A., Usami, Hisanao, Iwase, Akihide, Inoue, Haruo, Kudo, Akihiko, Gust, Devens, Domen, Kazunari, Cassiola, Flavia, Takagi, Katsuhiko, Kang, Sang Ook, Yamakata, Akira, Li, Can, Sun, Licheng, Park, Hyunwoong, Kang, Young Soo, Li, Rengui, Di Fonzo, Fabio, Setoyama, Tohru, Ishitani, Osamu, Kumagai, Hiromu, Hammarstrom, Leif, Whang, Dong Ryeol, Shinohara, Yuki, Martinez, Jose, Karlsson, Joshua, Summers, Peter, Windle, Christopher D., Kodera, Masanori, Cogdell, Richard, Tolod, Kristine Rodulfo, Apaydin, Dogukan Hazar, Fujita, Etsuko, Kibler, Alexander, Fan, Fengtao, Gibson, Elizabeth A., Usami, Hisanao, Iwase, Akihide, Inoue, Haruo, Kudo, Akihiko, Gust, Devens, Domen, Kazunari, Cassiola, Flavia, Takagi, Katsuhiko, Kang, Sang Ook, Yamakata, Akira, Li, Can, Sun, Licheng, Park, Hyunwoong, Kang, Young Soo, Li, Rengui, Di Fonzo, Fabio, Setoyama, Tohru, and Ishitani, Osamu

Abstract

QC 20170630

Published
2017
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34. Inorganic assembly catalysts for artificial photosynthesis: general discussion

Author

Kumagai, Hiromu, primary, Hammarström, Leif, additional, Whang, Dong Ryeol, additional, Shinohara, Yuki, additional, Martinez, Jose, additional, Karlsson, Joshua, additional, Summers, Peter, additional, Windle, Christopher D., additional, Kodera, Masanori, additional, Cogdell, Richard, additional, Tolod, Kristine Rodulfo, additional, Apaydin, Dogukan Hazar, additional, Fujita, Etsuko, additional, Kibler, Alexander, additional, Fan, Fengtao, additional, Gibson, Elizabeth A., additional, Usami, Hisanao, additional, Iwase, Akihide, additional, Inoue, Haruo, additional, Kudo, Akihiko, additional, Gust, Devens, additional, Domen, Kazunari, additional, Cassiola, Flavia, additional, Takagi, Katsuhiko, additional, Kang, Sang Ook, additional, Yamakata, Akira, additional, Li, Can, additional, Sun, Licheng, additional, Park, Hyunwoong, additional, Kang, Young Soo, additional, Li, Rengui, additional, Di Fonzo, Fabio, additional, Setoyama, Tohru, additional, and Ishitani, Osamu, additional

Published
2017
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36. Solar-driven Z-scheme water splitting using tantalum/nitrogen co-doped rutile titania nanorod as an oxygen evolution photocatalyst

Author

Nakada, Akinobu, primary, Nishioka, Shunta, additional, Vequizo, Junie Jhon M., additional, Muraoka, Kanemichi, additional, Kanazawa, Tomoki, additional, Yamakata, Akira, additional, Nozawa, Shunsuke, additional, Kumagai, Hiromu, additional, Adachi, Shin-ichi, additional, Ishitani, Osamu, additional, and Maeda, Kazuhiko, additional

Published
2017
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38. A Photoelectrochemical Solar Cell Consisting of a Cadmium Sulfide Photoanode and a Ruthenium–2, 2′‐Bipyridine Redox Shuttle in a Non‐aqueous Electrolyte

Author

Kageshima, Yosuke, Kumagai, Hiromu, Minegishi, Tsutomu, Kubota, Jun, and Domen, Kazunari

Subjects
Auxiliary electrode, Electrolysis of water, Inorganic chemistry, chemistry.chemical_element, General Medicine, General Chemistry, Electrolyte, Photochemistry, Redox, Catalysis, 2,2'-Bipyridine, Ruthenium, chemistry.chemical_compound, Bipyridine, chemistry, Water splitting
Abstract

A photoelectrochemical (PEC) cell consisting of an n-type CdS single-crystal electrode and a Pt counter electrode with the ruthenium-2,2'-bipyridine complex [Ru(bpy)3](2+/3+) as the redox shuttle in a non-aqueous electrolyte was studied to obtain a higher open-circuit voltage (V(OC)) than the onset voltage for water splitting. A V(OC) of 1.48 V and a short-circuit current (I(SC)) of 3.88 mA cm(-2) were obtained under irradiation by a 300 W Xe lamp with 420-800 nm visible light. This relatively high voltage was presumably due to the difference between the Fermi level of photo-irradiated n-type CdS and the redox potential of the Ru complex at the Pt electrode. The smooth redox reaction of the Ru complex with one-electron transfer was thought to have contributed to the high V(OC) and I(SC). The obtained V(OC) was more than the onset voltage of water electrolysis for hydrogen and oxygen generation, suggesting prospects for application in water electrolysis.

Published
2015

39. Photoelectrochemical Properties of Particulate CuGaSe2and CuIn0.7Ga0.3Se2Photocathodes in Nonaqueous Electrolyte

Author

Kageshima, Yosuke, Shiga, Sota, Kumagai, Hiromu, Teshima, Katsuya, Domen, Kazunari, and Nishikiori, Hiromasa

Abstract

The photoelectrochemical (PEC) properties of particulate CuGaSe2(CGSe) and CuIn0.7Ga0.3Se2(CIGS) photocathodes were evaluated in an acetonitrile electrolyte containing iron(III) acetylacetonate (Fe(acac)3) under simulated sunlight illumination, and compared to that in a typical aqueous electrolyte. The particulate CGSe and CIGS photocathodes can generate higher photovoltages, which is a more positive onset potential than the hydrogen evolution in an aqueous electrolyte possibly due to the facile one-electron reduction of Fe(acac)3, while the cathodic photocurrent decreased due to light shielding by the colored nonaqueous electrolyte. Indeed, the incident-photon-to-current conversion efficiencies (IPCEs) of the photocathode evidently decreased in the wavelength region of 400–600 nm, where the Fe(acac)3acetonitrile electrolyte shows an intense light absorption. The CIGS photocathode generates a higher cathodic photocurrent than the CGSe during hydrogen evolution from the aqueous electrolyte, while the CGSe exhibits superior PEC performances to CIGS in the nonaqueous electrolyte, which can be explained by the energy level of the conduction band minimum (CBM) of CGSe and CIGS compared to the reduction potential for Fe(acac)3. Finally, the two-electrode PEC-voltaic (PECV) cell consisting of the CGSe photocathode and Pt anode demonstrated a stable generated photovoltage by a one-step photoexcitation process.The photoelectrochemical (PEC) performances of particulate CuGaSe2(CGSe) and CuIn0.7Ga0.3Se2(CIGS) photocathodes were evaluated in an acetonitrile electrolyte containing iron(III) acetylacetonate, as well as an aqueous buffered electrolyte under simulated sunlight. The two-electrode PEC-voltaic (PECV) cell consisting of the CGSe photocathode and Pt anode was demonstrated to stably generate a photovoltage by a one-step photoexcitation process.

Published
2020
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42. Solar Water Oxidation by a Visible‐Light‐Responsive Tantalum/Nitrogen‐Codoped Rutile Titania Anode for Photoelectrochemical Water Splitting and Carbon Dioxide Fixation.

Author

Nakada, Akinobu, Uchiyama, Tomoki, Kawakami, Nozomi, Sahara, Go, Nishioka, Shunta, Kamata, Ryutaro, Kumagai, Hiromu, Ishitani, Osamu, Uchimoto, Yoshiharu, and Maeda, Kazuhiko

Subjects
OXIDATION of water, TITANIUM dioxide, PHOTOELECTROCHEMISTRY, WATER electrolysis, CARBON dioxide fixation
Abstract

Non‐oxide materials such as oxynitrides are good candidates as photoanodes for visible‐light‐driven water oxidation, but most of them suffer from oxidative degradation by photogenerated holes, resulting in low stability. Herein we developed a photoanode using a visible‐light‐responsive TiO2 powder doped with tantalum and nitrogen (TiO2:Ta/N) for water oxidation. The Ta/N codoping enabled a stable anodic photocurrent response attributable to water oxidation under visible‐light irradiation. Surface modification of the TiO2:Ta/N anode with RuOx species further facilitated water oxidation catalysis, achieving stable O2 evolution over 5 h of operation with no sign of deactivation. Operando XAFS measurements revealed an important function of the RuOx species as a collector of photogenerated holes in TiO2:Ta/N, facilitating the photoelectrochemical water oxidation. Visible‐light‐driven H2 evolution and solar‐driven CO2 reduction into CO were both achieved by using water as an electron donor in photoelectrochemical cells with the TiO2:Ta/N photoanode coupled to a Pt cathode and a Ru(II)–Re(I) binuclear complex photocathode, respectively. Jack of all trades: A photoanode composed of TiO2 doped with tantalum and nitrogen worked for stable photoelectrochemical water oxidation coupled to hydrogen evolution and carbon dioxide reduction under visible and solar light. Operando XAFS measurements revealed a key function of RuOx species as a collector of photogenerated holes in TiO2:Ta/N, facilitating the photoelectrochemical water oxidation. [ABSTRACT FROM AUTHOR]

Published
2019
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50. Photoelectrochemical CO2Reduction Using a Ru(II)–Re(I) Supramolecular Photocatalyst Connected to a Vinyl Polymer on a NiO Electrode

Author

Kamata, Ryutaro, Kumagai, Hiromu, Yamazaki, Yasuomi, Sahara, Go, and Ishitani, Osamu

Abstract

A Ru(II)–Re(I) supramolecular photocatalyst and a Ru(II) redox photosensitizer were both deposited successfully on a NiO electrode by using methyl phosphonic acid anchoring groups and the electrochemical polymerization of the ligand vinyl groups of the complexes. This new molecular photocathode, poly-RuRe/NiO, adsorbed a larger amount of the metal complexes compared to one using only methyl phosphonic acid anchor groups, and the stability of the complexes on the NiO electrode were much improved. The poly-RuRe/NiO acted as a photocathode for the photocatalytic reduction of CO2at E= −0.7 V vs Ag/AgCl under visible-light irradiation in an aqueous solution. The poly-RuRe/NiO produced approximately 2.5 times more CO, and its total Faradaic efficiency of the reduction products improved from 57 to 85%.

Published
2019
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