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RISS 인기검색어
- 검색키워드
- 저자 : Miyahigashi, Takamitsu (검색결과 3 건)
- 무료
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Yamada, Yusuke,Miyahigashi, Takamitsu,Kotani, Hiroaki,Ohkubo, Kei,Fukuzumi, Shunichi The Royal Society of Chemistry 2012 ENERGY AND ENVIRONMENTAL SCIENCE Vol.5 No.3
<P>Photocatalytic hydrogen evolution with 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh<SUP>+</SUP>–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 (<I>hcp</I>) 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 <I>hcp</I> structure is more than 4 times higher than the rate of the NiNPs with face-centred cubic (<I>fcc</I>) 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&z.rad;–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.</P> <P>Graphic Abstract</P><P>Photocatalytic hydrogen evolution with Ni nanoparticles was achieved for the first time. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee03106j'> </P>
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Yamada, Yusuke,Miyahigashi, Takamitsu,Ohkubo, Kei,Fukuzumi, Shunichi The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.30
<P>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<SUP>+</SUP>–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 (<I>λ</I> > 340 nm). The gas evolved during the photocatalytic reaction contained H<SUB>2</SUB> and CO<SUB>2</SUB> 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&z.rad;–NA&z.rad;<SUP>+</SUP>, which forms a π-dimer radical cation with QuPh<SUP>+</SUP>−NA [(QuPh&z.rad;–NA&z.rad;<SUP>+</SUP>)(QuPh<SUP>+</SUP>–NA)], occurs followed by subsequent electron transfer from QuPh&z.rad;–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.</P> <P>Graphic Abstract</P><P>Photocatalytic hydrogen evolution using a carbon-neutral electron donor with metal nanoparticles. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp41906h'> </P>
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Yamada, Yusuke,Nomura, Akifumi,Miyahigashi, Takamitsu,Ohkubo, Kei,Fukuzumi, Shunichi American Chemical Society 2013 The journal of physical chemistry. A, Molecules, s Vol.117 No.18
<P>The addition of acetate ion to an O<SUB>2</SUB>-saturated mixed solution of acetonitrile and water containing oxalic acid as a reductant and 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh<SUP>+</SUP>–NA) as a photocatalyst dramatically enhanced the turnover number of hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) production. In this photocatalytic H<SUB>2</SUB>O<SUB>2</SUB> 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 O<SUB>2</SUB><SUP>•–</SUP> for production of H<SUB>2</SUB>O<SUB>2</SUB> by disproportionation. The addition of acetate ion to a reaction solution facilitates both the deprotonation of oxalic acid and the protonation of O<SUB>2</SUB><SUP>•–</SUP> owing to a pH buffer effect. The quantum yield of the photocatalytic H<SUB>2</SUB>O<SUB>2</SUB> production under photoirradiation (λ = 334 nm) of an O<SUB>2</SUB>-saturated acetonitrile–water mixed solution containing acetate ion, oxalic acid and QuPh<SUP>+</SUP>–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<SUP>+</SUP>–NA reached more than 340. The reaction mechanism and the effect of solvent composition on the photocatalytic H<SUB>2</SUB>O<SUB>2</SUB> production were scrutinized by using nanosecond laser flash photolysis.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2013/jpcafh.2013.117.issue-18/jp312795f/production/images/medium/jp-2012-12795f_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp312795f'>ACS Electronic Supporting Info</A></P>
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