Photocatalytic hydrogen evolution from Hexaniobate nanoscrolls and calcium niobate nanosheets sensitized by ruthenium(II) bipyridyl complexes

Kazuhiko Maeda, Miharu Eguchi, Seung Hyun Anna Lee, W. Justin Youngblood, Hideo Hata, Thomas E. Mallouk

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Abstract

Hexaniobate nanoscrolls (NS-H 4Nb 6O 17) and acid-restacked calcium niobate nanosheets (R-HCa 2Nb 3O 10) were compared as oxide semiconductors in photocatalytic assemblies for H 2 production using ethylenediaminetetraacetic acid (EDTA) as a sacrificial electron donor and platinum (Pt) nanoparticles as catalysts. Ru(bpy) 3 2+ and Ru(bpy) 2(4,4'- (PO 3H 2) 2bpy) 2+ (bpy = 2,2'-bipyridine) were employed as visible light sensitizers (abbreviated as Ru 2+ and RuP 2+, respectively). RuP 2+, which is anchored by a covalent linkage to the NS- H 4aNb 6O 17 surface, functions more efficiently than the electrostatically bound Ru 2+ complex, because of more efficient electron injection from the excited sensitizer to NS-H 4Nb 6O 17. RuP 2+-sensitized NS-H 4Nb 6O 17 and R-HCa 2Nb 3O 10 both produce H 2 photocatalytically using visible light (λ > 420 nm) with initial apparent quantum yields of 20-25%. At the optimum sensitizer concentration and Pt loading, the photochemical hydrogen evolution process is primarily limited by the efficiency of light absorption and charge injection from the photoexcited sensitizer into the oxide semiconductor particles. The dependence of the hydrogen evolution rate on Pt loading suggests that the scavenging of conduction band electrons by Pt is substantially faster than charge recombination or EDTA reduction of the oxidized sensitizer under optimized conditions.

Original languageEnglish (US)
Pages (from-to)7962-7969
Number of pages8
JournalJournal of Physical Chemistry C
Volume113
Issue number18
DOIs
StatePublished - May 7 2009

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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