The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Shunichi Fukuzumi - One of the best experts on this subject based on the ideXlab platform.
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Robustness of Ru/SiO2 as a Hydrogen-EvolutIon Catalyst in a Photocatalytic System Using an Organic Photocatalyst
2016Co-Authors: Yusuke Yamada, Shinya Shikano, Shunichi FukuzumiAbstract:Effects of various metal oxide supports (SiO2, SiO2–Al2O3, TiO2, CeO2, and MgO) on the catalytic reactivity of ruthenium nanoparticles (RuNPs) used as a hydrogen-evolutIon catalyst have been evaluated in photocatalytic hydrogen evolutIon using 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) and dihydronicotinamide adenine dinucleotide (NADH) as a photocatalyst and an electron donor, respectively. The 3 wt % Ru/SiO2 catalyst freshly prepared by an impregnatIon method exhibited the highest catalytic reactivity among RuNPs supported on various metal oxides, which was nearly the same as that of commercially available Pt nanoparticles (PtNPs) with the same metal weight. However, the initial catalytic reactivity of 3 wt % Ru/SiO2 was lost after repetitive use, whereas the catalytic reactivity of PtNPs was maintained under the same experimental conditIons. The recyclability of the 3 wt % Ru/SiO2 was significantly improved by employing the CVD method for preparatIon. The initial catalytic reactivity of 0.97 wt % Ru/SiO2 prepared by the CVD method was higher than that of 2 wt % Ru/SiO2 prepared by the impregnatIon method despite the smaller Ru content. The total amount of evolved hydrogen normalized by the weight of Ru in 0.97 wt % Ru/SiO2 was 1.7 mol gRu–1, which is now close to that normalized by the weight of Pt in PtNPs (2.0 mol gPt–1). Not only the preparatIon method but also the morphology of SiO2 supports affected significantly the catalytic activity of Ru/SiO2. The Ru/SiO2 catalyst using nanosized SiO2 with undefined shape exhibited higher catalytic activity than Ru/SiO2 catalysts using mesoporous SiO2 or spherical SiO2. The kinetic study and TEM observatIon of the Ru/SiO2 catalysts suggest that the microenvironment of RuNPs on SiO2 surfaces plays an important role to exhibit the high catalytic performance in the photocatalytic hydrogen productIon
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photocatalytic h2 evolutIon from nadh with carbon quantum dots pt and 2 phenyl 4 1 naphthyl Quinolinium Ion
Journal of Photochemistry and Photobiology B-biology, 2015Co-Authors: Liying Zhan, Yusuke Yamada, Kei Ohkubo, Shunichi FukuzumiAbstract:Carbon quantum dots (CQDs) were simply blended with platinum salts (K2PtCl4 and K2PtCl6) and converted into a hydrogen-evolutIon co-catalyst in situ, wherein Pt salts were dispersed on the surface of CQDs under photoirradiatIon of an aqueous solutIon of NADH (an electron and proton source) and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+−NA) employed as an organic photocatalyst. The co-catalyst (CQDs/Pt) exhibits similar catalytic reactivity in H2 evolutIon as that of pure Pt nanoparticles (PtNPs) although the Pt amount of CQDs/Pt was only 1/200 that of PtNPs previously reported. CQDs were able to capture the Pt salt acting as Pt supports. Meanwhile, CQDs act as electron reservoir, playing an important role to enhance electron transfer from QuPh+−NA to the Pt salt, which was confirmed by kinetic studies, XPS and HRTEM.
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a composite photocatalyst of an organic electron donor acceptor dyad and a pt catalyst supported on semiconductor nanosheets for efficient hydrogen evolutIon from oxalic acid
Catalysis Science & Technology, 2015Co-Authors: Yusuke Yamada, Akifumi Nomura, Hideyuki Tadokoro, Shunichi FukuzumiAbstract:A composite photocatalytic system for hydrogen evolutIon employing acidic oxalic acid as an electron donor has been successfully constructed by combining 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), platinum (Pt) and nanosheets prepared by the exfoliatIon of K4Nb6O17 (niobate-NS) as an organic photosensitiser, a hydrogen-evolutIon catalyst and a semiconductor photocatalyst for the oxidatIon of oxalic acid, respectively. The composite photocatalyst, QuPh+–NA/niobate-NS (Pt), was prepared by a two-step route to locate a Pt catalyst near QuPh+–NA on the surface of niobate-NS: (i) supporting QuPh+–NA on niobate-NS by a catIon exchange method and then (ii) supporting Pt on the QuPh+–NA/niobate-NS by a photodepositIon method using PtCl42− as a precursor, which interacts repulsively with the negatively charged surface of niobate-NS. The precursor of PtCl42− was reduced to metallic Pt by the photocatalysis of QuPh+–NA in the presence of oxalate. Photocatalytic hydrogen evolutIon with the composite catalyst proceeds via photoexcitatIon of both niobate-NS and QuPh+–NA to produce an electron and a hole in the semiconductor and the ET state (QuPh˙–NA˙+), respectively. The photogenerated hole of niobate-NS oxidises oxalic acid to produce CO2 and CO2˙– with two protons, whereas the photogenerated electron and CO2˙– reduce QuPh+–NA and the electron-transfer (ET) state to produce two equivalents of QuPh˙–NA, which inject electrons to the Pt catalyst to reduce protons to hydrogen. The utilisatIon of oxalic acid as an electron donor even under highly acidic conditIons, which are thermodynamically favourable for proton reductIon to evolve hydrogen but unfavourable for oxalate oxidatIon, has been made possible for the first time by combining QuPh+–NA, Pt and niobate-NS. Composite photocatalysts were also prepared by employing mesoporous silica-alumina and nanosheets prepared by the exfoliatIon of KTiNbO5 (titanoniobate-NS), which possesses a band structure different from niobate-NS, as supports to clarify the requirements for a building block to achieve an active composite photocatalyst.
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the long lived electron transfer state of the 2 phenyl 4 1 naphthyl Quinolinium Ion incorporated into nanosized mesoporous silica alumina acting as a robust photocatalyst in water
Chemical Communications, 2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Shunichi Fukuzumi, Kei Ohkubo, Tomoyoshi SuenobuAbstract:A simple electron donor–acceptor linked dyad, the 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), was incorporated into nanosized mesoporous silica–alumina to form a composite, which is highly dispersed in water and acts as an efficient and robust photocatalyst for the reductIon of O2 by oxalate to produce hydrogen peroxide with a quantum yield of 10%.
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Acetate Induced Enhancement of Photocatalytic Hydrogen Peroxide ProductIon from Oxalic Acid and Dioxygen
2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Kei Ohkubo, Takamitsu Miyahigashi, Shunichi FukuzumiAbstract:The additIon of acetate Ion to an O2-saturated mixed solutIon of acetonitrile and water containing oxalic acid as a reductant and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst dramatically enhanced the turnover number of hydrogen peroxide (H2O2) productIon. In this photocatalytic H2O2 productIon, a base is required to facilitate deprotonatIon of oxalic acid forming oxalate dianIon, which acts as an actual electron donor, whereas a Brønsted acid is also necessary to protonate O2•– for productIon of H2O2 by disproportIonatIon. The additIon of acetate Ion to a reactIon solutIon facilitates both the deprotonatIon of oxalic acid and the protonatIon of O2•– owing to a pH buffer effect. The quantum yield of the photocatalytic H2O2 productIon under photoirradiatIon (λ = 334 nm) of an O2-saturated acetonitrile–water mixed solutIon containing acetate Ion, oxalic acid and QuPh+–NA was determined to be as high as 0.34, which is more than double the quantum yield obtained by using oxalate salt as an electron donor without acetate Ion (0.14). In additIon, the turnover number of QuPh+–NA reached more than 340. The reactIon mechanism and the effect of solvent compositIon on the photocatalytic H2O2 productIon were scrutinized by using nanosecond laser flash photolysis
Yusuke Yamada - One of the best experts on this subject based on the ideXlab platform.
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Robustness of Ru/SiO2 as a Hydrogen-EvolutIon Catalyst in a Photocatalytic System Using an Organic Photocatalyst
2016Co-Authors: Yusuke Yamada, Shinya Shikano, Shunichi FukuzumiAbstract:Effects of various metal oxide supports (SiO2, SiO2–Al2O3, TiO2, CeO2, and MgO) on the catalytic reactivity of ruthenium nanoparticles (RuNPs) used as a hydrogen-evolutIon catalyst have been evaluated in photocatalytic hydrogen evolutIon using 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) and dihydronicotinamide adenine dinucleotide (NADH) as a photocatalyst and an electron donor, respectively. The 3 wt % Ru/SiO2 catalyst freshly prepared by an impregnatIon method exhibited the highest catalytic reactivity among RuNPs supported on various metal oxides, which was nearly the same as that of commercially available Pt nanoparticles (PtNPs) with the same metal weight. However, the initial catalytic reactivity of 3 wt % Ru/SiO2 was lost after repetitive use, whereas the catalytic reactivity of PtNPs was maintained under the same experimental conditIons. The recyclability of the 3 wt % Ru/SiO2 was significantly improved by employing the CVD method for preparatIon. The initial catalytic reactivity of 0.97 wt % Ru/SiO2 prepared by the CVD method was higher than that of 2 wt % Ru/SiO2 prepared by the impregnatIon method despite the smaller Ru content. The total amount of evolved hydrogen normalized by the weight of Ru in 0.97 wt % Ru/SiO2 was 1.7 mol gRu–1, which is now close to that normalized by the weight of Pt in PtNPs (2.0 mol gPt–1). Not only the preparatIon method but also the morphology of SiO2 supports affected significantly the catalytic activity of Ru/SiO2. The Ru/SiO2 catalyst using nanosized SiO2 with undefined shape exhibited higher catalytic activity than Ru/SiO2 catalysts using mesoporous SiO2 or spherical SiO2. The kinetic study and TEM observatIon of the Ru/SiO2 catalysts suggest that the microenvironment of RuNPs on SiO2 surfaces plays an important role to exhibit the high catalytic performance in the photocatalytic hydrogen productIon
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photocatalytic h2 evolutIon from nadh with carbon quantum dots pt and 2 phenyl 4 1 naphthyl Quinolinium Ion
Journal of Photochemistry and Photobiology B-biology, 2015Co-Authors: Liying Zhan, Yusuke Yamada, Kei Ohkubo, Shunichi FukuzumiAbstract:Carbon quantum dots (CQDs) were simply blended with platinum salts (K2PtCl4 and K2PtCl6) and converted into a hydrogen-evolutIon co-catalyst in situ, wherein Pt salts were dispersed on the surface of CQDs under photoirradiatIon of an aqueous solutIon of NADH (an electron and proton source) and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+−NA) employed as an organic photocatalyst. The co-catalyst (CQDs/Pt) exhibits similar catalytic reactivity in H2 evolutIon as that of pure Pt nanoparticles (PtNPs) although the Pt amount of CQDs/Pt was only 1/200 that of PtNPs previously reported. CQDs were able to capture the Pt salt acting as Pt supports. Meanwhile, CQDs act as electron reservoir, playing an important role to enhance electron transfer from QuPh+−NA to the Pt salt, which was confirmed by kinetic studies, XPS and HRTEM.
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a composite photocatalyst of an organic electron donor acceptor dyad and a pt catalyst supported on semiconductor nanosheets for efficient hydrogen evolutIon from oxalic acid
Catalysis Science & Technology, 2015Co-Authors: Yusuke Yamada, Akifumi Nomura, Hideyuki Tadokoro, Shunichi FukuzumiAbstract:A composite photocatalytic system for hydrogen evolutIon employing acidic oxalic acid as an electron donor has been successfully constructed by combining 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), platinum (Pt) and nanosheets prepared by the exfoliatIon of K4Nb6O17 (niobate-NS) as an organic photosensitiser, a hydrogen-evolutIon catalyst and a semiconductor photocatalyst for the oxidatIon of oxalic acid, respectively. The composite photocatalyst, QuPh+–NA/niobate-NS (Pt), was prepared by a two-step route to locate a Pt catalyst near QuPh+–NA on the surface of niobate-NS: (i) supporting QuPh+–NA on niobate-NS by a catIon exchange method and then (ii) supporting Pt on the QuPh+–NA/niobate-NS by a photodepositIon method using PtCl42− as a precursor, which interacts repulsively with the negatively charged surface of niobate-NS. The precursor of PtCl42− was reduced to metallic Pt by the photocatalysis of QuPh+–NA in the presence of oxalate. Photocatalytic hydrogen evolutIon with the composite catalyst proceeds via photoexcitatIon of both niobate-NS and QuPh+–NA to produce an electron and a hole in the semiconductor and the ET state (QuPh˙–NA˙+), respectively. The photogenerated hole of niobate-NS oxidises oxalic acid to produce CO2 and CO2˙– with two protons, whereas the photogenerated electron and CO2˙– reduce QuPh+–NA and the electron-transfer (ET) state to produce two equivalents of QuPh˙–NA, which inject electrons to the Pt catalyst to reduce protons to hydrogen. The utilisatIon of oxalic acid as an electron donor even under highly acidic conditIons, which are thermodynamically favourable for proton reductIon to evolve hydrogen but unfavourable for oxalate oxidatIon, has been made possible for the first time by combining QuPh+–NA, Pt and niobate-NS. Composite photocatalysts were also prepared by employing mesoporous silica-alumina and nanosheets prepared by the exfoliatIon of KTiNbO5 (titanoniobate-NS), which possesses a band structure different from niobate-NS, as supports to clarify the requirements for a building block to achieve an active composite photocatalyst.
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the long lived electron transfer state of the 2 phenyl 4 1 naphthyl Quinolinium Ion incorporated into nanosized mesoporous silica alumina acting as a robust photocatalyst in water
Chemical Communications, 2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Shunichi Fukuzumi, Kei Ohkubo, Tomoyoshi SuenobuAbstract:A simple electron donor–acceptor linked dyad, the 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), was incorporated into nanosized mesoporous silica–alumina to form a composite, which is highly dispersed in water and acts as an efficient and robust photocatalyst for the reductIon of O2 by oxalate to produce hydrogen peroxide with a quantum yield of 10%.
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Acetate Induced Enhancement of Photocatalytic Hydrogen Peroxide ProductIon from Oxalic Acid and Dioxygen
2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Kei Ohkubo, Takamitsu Miyahigashi, Shunichi FukuzumiAbstract:The additIon of acetate Ion to an O2-saturated mixed solutIon of acetonitrile and water containing oxalic acid as a reductant and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst dramatically enhanced the turnover number of hydrogen peroxide (H2O2) productIon. In this photocatalytic H2O2 productIon, a base is required to facilitate deprotonatIon of oxalic acid forming oxalate dianIon, which acts as an actual electron donor, whereas a Brønsted acid is also necessary to protonate O2•– for productIon of H2O2 by disproportIonatIon. The additIon of acetate Ion to a reactIon solutIon facilitates both the deprotonatIon of oxalic acid and the protonatIon of O2•– owing to a pH buffer effect. The quantum yield of the photocatalytic H2O2 productIon under photoirradiatIon (λ = 334 nm) of an O2-saturated acetonitrile–water mixed solutIon containing acetate Ion, oxalic acid and QuPh+–NA was determined to be as high as 0.34, which is more than double the quantum yield obtained by using oxalate salt as an electron donor without acetate Ion (0.14). In additIon, the turnover number of QuPh+–NA reached more than 340. The reactIon mechanism and the effect of solvent compositIon on the photocatalytic H2O2 productIon were scrutinized by using nanosecond laser flash photolysis
Kei Ohkubo - One of the best experts on this subject based on the ideXlab platform.
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photocatalytic h2 evolutIon from nadh with carbon quantum dots pt and 2 phenyl 4 1 naphthyl Quinolinium Ion
Journal of Photochemistry and Photobiology B-biology, 2015Co-Authors: Liying Zhan, Yusuke Yamada, Kei Ohkubo, Shunichi FukuzumiAbstract:Carbon quantum dots (CQDs) were simply blended with platinum salts (K2PtCl4 and K2PtCl6) and converted into a hydrogen-evolutIon co-catalyst in situ, wherein Pt salts were dispersed on the surface of CQDs under photoirradiatIon of an aqueous solutIon of NADH (an electron and proton source) and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+−NA) employed as an organic photocatalyst. The co-catalyst (CQDs/Pt) exhibits similar catalytic reactivity in H2 evolutIon as that of pure Pt nanoparticles (PtNPs) although the Pt amount of CQDs/Pt was only 1/200 that of PtNPs previously reported. CQDs were able to capture the Pt salt acting as Pt supports. Meanwhile, CQDs act as electron reservoir, playing an important role to enhance electron transfer from QuPh+−NA to the Pt salt, which was confirmed by kinetic studies, XPS and HRTEM.
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the long lived electron transfer state of the 2 phenyl 4 1 naphthyl Quinolinium Ion incorporated into nanosized mesoporous silica alumina acting as a robust photocatalyst in water
Chemical Communications, 2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Shunichi Fukuzumi, Kei Ohkubo, Tomoyoshi SuenobuAbstract:A simple electron donor–acceptor linked dyad, the 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), was incorporated into nanosized mesoporous silica–alumina to form a composite, which is highly dispersed in water and acts as an efficient and robust photocatalyst for the reductIon of O2 by oxalate to produce hydrogen peroxide with a quantum yield of 10%.
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Acetate Induced Enhancement of Photocatalytic Hydrogen Peroxide ProductIon from Oxalic Acid and Dioxygen
2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Kei Ohkubo, Takamitsu Miyahigashi, Shunichi FukuzumiAbstract:The additIon of acetate Ion to an O2-saturated mixed solutIon of acetonitrile and water containing oxalic acid as a reductant and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst dramatically enhanced the turnover number of hydrogen peroxide (H2O2) productIon. In this photocatalytic H2O2 productIon, a base is required to facilitate deprotonatIon of oxalic acid forming oxalate dianIon, which acts as an actual electron donor, whereas a Brønsted acid is also necessary to protonate O2•– for productIon of H2O2 by disproportIonatIon. The additIon of acetate Ion to a reactIon solutIon facilitates both the deprotonatIon of oxalic acid and the protonatIon of O2•– owing to a pH buffer effect. The quantum yield of the photocatalytic H2O2 productIon under photoirradiatIon (λ = 334 nm) of an O2-saturated acetonitrile–water mixed solutIon containing acetate Ion, oxalic acid and QuPh+–NA was determined to be as high as 0.34, which is more than double the quantum yield obtained by using oxalate salt as an electron donor without acetate Ion (0.14). In additIon, the turnover number of QuPh+–NA reached more than 340. The reactIon mechanism and the effect of solvent compositIon on the photocatalytic H2O2 productIon were scrutinized by using nanosecond laser flash photolysis
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photocatalytic hydrogen evolutIon from carbon neutral oxalate with 2 phenyl 4 1 naphthyl Quinolinium Ion and metal nanoparticles
Physical Chemistry Chemical Physics, 2012Co-Authors: Yusuke Yamada, Shunichi Fukuzumi, Kei Ohkubo, Takamitsu MiyahigashiAbstract:Photocatalytic hydrogen evolutIon has been made possible by using oxalate as a carbon-neutral electron source, metal nanoparticles as hydrogen-evolutIon catalysts and the 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), which forms the long-lived electron-transfer state upon photoexcitatIon, as a photocatalyst. The hydrogen evolutIon was conducted in a deaerated mixed solutIon of an aqueous buffer and acetonitrile (MeCN) [1 : 1 (v/v)] by photoirradiatIon (λ > 340 nm). The gas evolved during the photocatalytic reactIon contained H2 and CO2 in a molar ratio of 1 : 2, indicating that oxalate acts as a two-electron donor. The hydrogen yield based on the amount of oxalate reached more than 80% under pH conditIons higher than 6. Ni and Ru nanoparticles as well as Pt nanoparticles act as efficient hydrogen-evolutIon catalysts in the photocatalytic hydrogen evolutIon. The photocatalyst for hydrogen evolutIon can be used several times without significant deactivatIon of the catalytic activity. Nanosecond laser flash photolysis measurements have revealed that electron transfer from oxalate to the photogenerated QuPh˙–NA˙+, which forms a π-dimer radical catIon with QuPh+−NA [(QuPh˙–NA˙+)(QuPh+–NA)], occurs followed by subsequent electron transfer from QuPh˙–NA to the hydrogen-evolutIon catalyst in the photocatalytic hydrogen evolutIon. Oxalate acts as an efficient electron source under a wide range of reactIon conditIons.
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photocatalytic hydrogen evolutIon with ni nanoparticles by using 2 phenyl 4 1 naphthyl Quinolinium Ion as a photocatalyst
Energy and Environmental Science, 2012Co-Authors: Yusuke Yamada, Shunichi Fukuzumi, Hiroaki Kotani, Kei Ohkubo, Takamitsu MiyahigashiAbstract:Photocatalytic hydrogen evolutIon with 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst and dihydronicotinamide adenine dinucleotide (NADH) as a sacrificial electron donor has been made possible for the first time by using nickel nanoparticles (NiNPs) as a non-precious metal catalyst. The hydrogen evolutIon rate with the most active Ni nanoparticles (hexagonal close-packed (hcp) structure, 6.6 nm) examined here was 40% of that with commercially available Pt nanoparticles (2 nm) using the same catalyst weight. The catalytic activity of NiNPs depends not only on their sizes but also on their crystal phases. The hydrogen-evolutIon rate normalized by the catalyst weight increased as the size of NiNPs becomes smaller, with regard to the crystal phase, the hydrogen-evolutIon rate of the NiNPs with hcp structure is more than 4 times higher than the rate of the NiNPs with face-centred cubic (fcc) structure of similar size. NiNPs act as the hydrogen-evolutIon catalyst under the pH conditIons between 4.5 and 8.0, although the hydrogen-evolutIon rate at pH > 7.0 was much lower as compared with the hydrogen-evolutIon rate at pH 4.5. A kinetic study revealed that the rate of electron transfer from photogenerated QuPh˙–NA to NiNPs was much higher than the rate of hydrogen evolutIon, indicating that the rate-determining step may be proton reductIon or desorptIon of hydrogen.
Takamitsu Miyahigashi - One of the best experts on this subject based on the ideXlab platform.
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Acetate Induced Enhancement of Photocatalytic Hydrogen Peroxide ProductIon from Oxalic Acid and Dioxygen
2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Kei Ohkubo, Takamitsu Miyahigashi, Shunichi FukuzumiAbstract:The additIon of acetate Ion to an O2-saturated mixed solutIon of acetonitrile and water containing oxalic acid as a reductant and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst dramatically enhanced the turnover number of hydrogen peroxide (H2O2) productIon. In this photocatalytic H2O2 productIon, a base is required to facilitate deprotonatIon of oxalic acid forming oxalate dianIon, which acts as an actual electron donor, whereas a Brønsted acid is also necessary to protonate O2•– for productIon of H2O2 by disproportIonatIon. The additIon of acetate Ion to a reactIon solutIon facilitates both the deprotonatIon of oxalic acid and the protonatIon of O2•– owing to a pH buffer effect. The quantum yield of the photocatalytic H2O2 productIon under photoirradiatIon (λ = 334 nm) of an O2-saturated acetonitrile–water mixed solutIon containing acetate Ion, oxalic acid and QuPh+–NA was determined to be as high as 0.34, which is more than double the quantum yield obtained by using oxalate salt as an electron donor without acetate Ion (0.14). In additIon, the turnover number of QuPh+–NA reached more than 340. The reactIon mechanism and the effect of solvent compositIon on the photocatalytic H2O2 productIon were scrutinized by using nanosecond laser flash photolysis
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photocatalytic productIon of hydrogen peroxide by two electron reductIon of dioxygen with carbon neutral oxalate using a 2 phenyl 4 1 naphthyl Quinolinium Ion as a robust photocatalyst
Chemical Communications, 2012Co-Authors: Yusuke Yamada, Akifumi Nomura, Shunichi Fukuzumi, Takamitsu MiyahigashiAbstract:Efficient photocatalytic productIon of hydrogen peroxide (H2O2) from O2 and oxalate has been made possible by using a 2-phenyl-4-(1-naphthyl)Quinolinium Ion as a robust photocatalyst in an oxygen-saturated mixed solutIon of a buffer and acetonitrile with a high quantum yield of 14% (maximum 50% for the two-electron process) at λ = 334 nm and a high H2O2 yield of 93% at λ > 340 nm.
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photocatalytic hydrogen evolutIon from carbon neutral oxalate with 2 phenyl 4 1 naphthyl Quinolinium Ion and metal nanoparticles
Physical Chemistry Chemical Physics, 2012Co-Authors: Yusuke Yamada, Shunichi Fukuzumi, Kei Ohkubo, Takamitsu MiyahigashiAbstract:Photocatalytic hydrogen evolutIon has been made possible by using oxalate as a carbon-neutral electron source, metal nanoparticles as hydrogen-evolutIon catalysts and the 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), which forms the long-lived electron-transfer state upon photoexcitatIon, as a photocatalyst. The hydrogen evolutIon was conducted in a deaerated mixed solutIon of an aqueous buffer and acetonitrile (MeCN) [1 : 1 (v/v)] by photoirradiatIon (λ > 340 nm). The gas evolved during the photocatalytic reactIon contained H2 and CO2 in a molar ratio of 1 : 2, indicating that oxalate acts as a two-electron donor. The hydrogen yield based on the amount of oxalate reached more than 80% under pH conditIons higher than 6. Ni and Ru nanoparticles as well as Pt nanoparticles act as efficient hydrogen-evolutIon catalysts in the photocatalytic hydrogen evolutIon. The photocatalyst for hydrogen evolutIon can be used several times without significant deactivatIon of the catalytic activity. Nanosecond laser flash photolysis measurements have revealed that electron transfer from oxalate to the photogenerated QuPh˙–NA˙+, which forms a π-dimer radical catIon with QuPh+−NA [(QuPh˙–NA˙+)(QuPh+–NA)], occurs followed by subsequent electron transfer from QuPh˙–NA to the hydrogen-evolutIon catalyst in the photocatalytic hydrogen evolutIon. Oxalate acts as an efficient electron source under a wide range of reactIon conditIons.
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photocatalytic hydrogen evolutIon with ni nanoparticles by using 2 phenyl 4 1 naphthyl Quinolinium Ion as a photocatalyst
Energy and Environmental Science, 2012Co-Authors: Yusuke Yamada, Shunichi Fukuzumi, Hiroaki Kotani, Kei Ohkubo, Takamitsu MiyahigashiAbstract:Photocatalytic hydrogen evolutIon with 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst and dihydronicotinamide adenine dinucleotide (NADH) as a sacrificial electron donor has been made possible for the first time by using nickel nanoparticles (NiNPs) as a non-precious metal catalyst. The hydrogen evolutIon rate with the most active Ni nanoparticles (hexagonal close-packed (hcp) structure, 6.6 nm) examined here was 40% of that with commercially available Pt nanoparticles (2 nm) using the same catalyst weight. The catalytic activity of NiNPs depends not only on their sizes but also on their crystal phases. The hydrogen-evolutIon rate normalized by the catalyst weight increased as the size of NiNPs becomes smaller, with regard to the crystal phase, the hydrogen-evolutIon rate of the NiNPs with hcp structure is more than 4 times higher than the rate of the NiNPs with face-centred cubic (fcc) structure of similar size. NiNPs act as the hydrogen-evolutIon catalyst under the pH conditIons between 4.5 and 8.0, although the hydrogen-evolutIon rate at pH > 7.0 was much lower as compared with the hydrogen-evolutIon rate at pH 4.5. A kinetic study revealed that the rate of electron transfer from photogenerated QuPh˙–NA to NiNPs was much higher than the rate of hydrogen evolutIon, indicating that the rate-determining step may be proton reductIon or desorptIon of hydrogen.
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photocatalytic hydrogen evolutIon under highly basic conditIons by using ru nanoparticles and 2 phenyl 4 1 naphthyl Quinolinium Ion
Journal of the American Chemical Society, 2011Co-Authors: Yusuke Yamada, Hiroaki Kotani, Kei Ohkubo, Takamitsu Miyahigashi, Shunichi FukuzumiAbstract:Photocatalytic hydrogen evolutIon with a ruthenium metal catalyst under basic conditIons (pH 10) has been made possible for the first time by using 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), dihydronicotinamide adenine dinucleotide (NADH), and Ru nanoparticles (RuNPs) as the photocatalyst, electron donor, and hydrogen-evolutIon catalyst, respectively. The catalytic reactivity of RuNPs was virtually the same as that of commercially available PtNPs. Nanosecond laser flash photolysis measurements were performed to examine the photodynamics of QuPh+–NA in the presence of NADH. Upon photoexcitatIon of QuPh+–NA, the electron-transfer state of QuPh+–NA (QuPh•–NA•+) is produced, followed by formatIon of the π-dimer radical catIon with QuPh+–NA, [(QuPh•–NA•+)(QuPh+–NA)]. Electron transfer from NADH to the π-dimer radical catIon leads to the productIon of 2 equiv of QuPh•–NA via deprotonatIon of NADH•+ and subsequent electron transfer from NAD• to QuPh+–NA. Electron transfer from the photogenerated QuPh•–NA...
Akifumi Nomura - One of the best experts on this subject based on the ideXlab platform.
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a composite photocatalyst of an organic electron donor acceptor dyad and a pt catalyst supported on semiconductor nanosheets for efficient hydrogen evolutIon from oxalic acid
Catalysis Science & Technology, 2015Co-Authors: Yusuke Yamada, Akifumi Nomura, Hideyuki Tadokoro, Shunichi FukuzumiAbstract:A composite photocatalytic system for hydrogen evolutIon employing acidic oxalic acid as an electron donor has been successfully constructed by combining 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), platinum (Pt) and nanosheets prepared by the exfoliatIon of K4Nb6O17 (niobate-NS) as an organic photosensitiser, a hydrogen-evolutIon catalyst and a semiconductor photocatalyst for the oxidatIon of oxalic acid, respectively. The composite photocatalyst, QuPh+–NA/niobate-NS (Pt), was prepared by a two-step route to locate a Pt catalyst near QuPh+–NA on the surface of niobate-NS: (i) supporting QuPh+–NA on niobate-NS by a catIon exchange method and then (ii) supporting Pt on the QuPh+–NA/niobate-NS by a photodepositIon method using PtCl42− as a precursor, which interacts repulsively with the negatively charged surface of niobate-NS. The precursor of PtCl42− was reduced to metallic Pt by the photocatalysis of QuPh+–NA in the presence of oxalate. Photocatalytic hydrogen evolutIon with the composite catalyst proceeds via photoexcitatIon of both niobate-NS and QuPh+–NA to produce an electron and a hole in the semiconductor and the ET state (QuPh˙–NA˙+), respectively. The photogenerated hole of niobate-NS oxidises oxalic acid to produce CO2 and CO2˙– with two protons, whereas the photogenerated electron and CO2˙– reduce QuPh+–NA and the electron-transfer (ET) state to produce two equivalents of QuPh˙–NA, which inject electrons to the Pt catalyst to reduce protons to hydrogen. The utilisatIon of oxalic acid as an electron donor even under highly acidic conditIons, which are thermodynamically favourable for proton reductIon to evolve hydrogen but unfavourable for oxalate oxidatIon, has been made possible for the first time by combining QuPh+–NA, Pt and niobate-NS. Composite photocatalysts were also prepared by employing mesoporous silica-alumina and nanosheets prepared by the exfoliatIon of KTiNbO5 (titanoniobate-NS), which possesses a band structure different from niobate-NS, as supports to clarify the requirements for a building block to achieve an active composite photocatalyst.
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the long lived electron transfer state of the 2 phenyl 4 1 naphthyl Quinolinium Ion incorporated into nanosized mesoporous silica alumina acting as a robust photocatalyst in water
Chemical Communications, 2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Shunichi Fukuzumi, Kei Ohkubo, Tomoyoshi SuenobuAbstract:A simple electron donor–acceptor linked dyad, the 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA), was incorporated into nanosized mesoporous silica–alumina to form a composite, which is highly dispersed in water and acts as an efficient and robust photocatalyst for the reductIon of O2 by oxalate to produce hydrogen peroxide with a quantum yield of 10%.
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Acetate Induced Enhancement of Photocatalytic Hydrogen Peroxide ProductIon from Oxalic Acid and Dioxygen
2013Co-Authors: Yusuke Yamada, Akifumi Nomura, Kei Ohkubo, Takamitsu Miyahigashi, Shunichi FukuzumiAbstract:The additIon of acetate Ion to an O2-saturated mixed solutIon of acetonitrile and water containing oxalic acid as a reductant and 2-phenyl-4-(1-naphthyl)Quinolinium Ion (QuPh+–NA) as a photocatalyst dramatically enhanced the turnover number of hydrogen peroxide (H2O2) productIon. In this photocatalytic H2O2 productIon, a base is required to facilitate deprotonatIon of oxalic acid forming oxalate dianIon, which acts as an actual electron donor, whereas a Brønsted acid is also necessary to protonate O2•– for productIon of H2O2 by disproportIonatIon. The additIon of acetate Ion to a reactIon solutIon facilitates both the deprotonatIon of oxalic acid and the protonatIon of O2•– owing to a pH buffer effect. The quantum yield of the photocatalytic H2O2 productIon under photoirradiatIon (λ = 334 nm) of an O2-saturated acetonitrile–water mixed solutIon containing acetate Ion, oxalic acid and QuPh+–NA was determined to be as high as 0.34, which is more than double the quantum yield obtained by using oxalate salt as an electron donor without acetate Ion (0.14). In additIon, the turnover number of QuPh+–NA reached more than 340. The reactIon mechanism and the effect of solvent compositIon on the photocatalytic H2O2 productIon were scrutinized by using nanosecond laser flash photolysis
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photocatalytic productIon of hydrogen peroxide by two electron reductIon of dioxygen with carbon neutral oxalate using a 2 phenyl 4 1 naphthyl Quinolinium Ion as a robust photocatalyst
Chemical Communications, 2012Co-Authors: Yusuke Yamada, Akifumi Nomura, Shunichi Fukuzumi, Takamitsu MiyahigashiAbstract:Efficient photocatalytic productIon of hydrogen peroxide (H2O2) from O2 and oxalate has been made possible by using a 2-phenyl-4-(1-naphthyl)Quinolinium Ion as a robust photocatalyst in an oxygen-saturated mixed solutIon of a buffer and acetonitrile with a high quantum yield of 14% (maximum 50% for the two-electron process) at λ = 334 nm and a high H2O2 yield of 93% at λ > 340 nm.
