Size-and shape-dependent activity of metal nanoparticles as hydrogen-evolution catalysts: Mechanistic insights into photocatalytic hydrogen evolution

Hiroaki Kotani, Ryo Hanazaki, Kei Ohkubo, Yusuke Yamada, Shunichi Fukuzumi

Research output: Contribution to journalArticlepeer-review

93 Scopus citations

Abstract

The catalytic activity of Pt nanoparticles (PtNPs) with different sizes and shapes was investigated in a photocatalytic hydrogen-evolution system composed of the 9-mesityl-10-methylacridinium ion (Acr+-Mes: photocatalyst) and dihydronicotinamide adenine dinucleotide (NADH: electron donor), based on rates of hydrogen evolution and electron transfer from one-electron-reduced species of Acr+-Mes (Acr.-Mes) to PtNPs. Cubic PtNPs with a diameter of (6.3±0.6)nm exhibited the maximum catalytic activity. The observed hydrogen-evolution rate was virtually the same as the rate of electron transfer from Acr.-Mes to PtNPs. The rate constant of electron transfer (ket) increased linearly with increasing proton concentration. When H+ was replaced by D+, the inverse kinetic isotope effect was observed for the electron-transfer rate constant (ket(H)/ket(D)=0.47). The linear dependence of k et on proton concentration together with the observed inverse kinetic isotope effect suggests that proton-coupled electron transfer from Acr .-Mes to PtNPs to form the PtH bond is the rate-determining step for catalytic hydrogen evolution. When FeNPs were used instead of PtNPs, hydrogen evolution was also observed, although the hydrogen-evolution efficiency was significantly lower than that of PtNPs because of the much slower electron transfer from Acr.-Mes to FeNPs.

Original languageEnglish
Pages (from-to)2777-2785
Number of pages9
JournalChemistry - A European Journal
Volume17
Issue number9
DOIs
StatePublished - 25 Feb 2011

Keywords

  • electron transfer
  • hydrogen
  • isotope effects
  • metal nanoparticles
  • photocatalysts

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