Photocatalytic Water Oxidation with Nonsensitized IrO2 Nanocrystals under Visible and UV Light

By Frame, F. Andrew; Townsend, Troy K.; Chamousis, Rachel L.; Sabio, Erwin M.; Dittrich, Th.; Browning, Nigel D. & Osterloh, Frank E.
Published in Journal of the American Chemical Society NULL 2011

Abstract

Rutile IrO2 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 IrO2 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(t2g) to the Ir-d(eg) band (1.5 -2.75 eV) and by ultraviolet excitations from the O-p band to the Ir-d(eg) (>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 IrO2 in dye- and semiconductor-sensitized water splitting systems.

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