title: Photocatalytic water oxidation with nonsensitized IrO2 nanocrystals under visible and UV light.
abstract: Rutile IrO(2) is known as being among the best electrocatalysts for water oxidation. Here we report on the unexpected photocatalytic water oxidation activity of 1.98 nm ± 0.11 nm succinic acid-stabilized IrO(2) nanocrystals. From aqueous persulfate and silver nitrate solution the nonsensitized particles evolve oxygen with initial rates up to 0.96 μmol min(-1), and with a quantum efficiency of at least 0.19% (measured at 530 nm). The catalytic process is driven by visible excitations from the Ir-d(t(2g)) to the Ir-d(e(g)) band (1.5-2.75 eV) and by ultraviolet excitations from the O-p band to the Ir-d(e(g)) (>3.0 eV) band. The formation of the photogenerated charge carriers can be directly observed with surface photovoltage spectroscopy. The results shed new light on the role of IrO(2) in dye- and semiconductor-sensitized water splitting systems.
authors.affiliation: Department of Chemistry, University of California, Davis, One Shields Ave, Davis, California 95616, USA.
authors.forename: F Andrew
authors.initials: FA
authors.lastname: Frame
authors.forename: Troy K
authors.initials: TK
authors.lastname: Townsend
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Chamousis
authors.forename: Erwin M
authors.initials: EM
authors.lastname: Sabio
authors.forename: Th
authors.initials: T
authors.lastname: Dittrich
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Browning
authors.forename: Frank E
authors.initials: FE
authors.lastname: Osterloh