title: Photoelectrochemical and impedance spectroscopic investigation of water oxidation with "Co-Pi"-coated hematite electrodes.
abstract: Uniform thin films of hematite (α-Fe(2)O(3)) deposited by atomic layer deposition (ALD) coated with varying amounts of the cobalt phosphate catalyst, "Co-Pi," were investigated with steady-state and transient photoelectrochemical measurements and impedance spectroscopy. Systematic studies as a function of Co-Pi thickness were performed in order to clarify the mechanism by which Co-Pi enhances the water-splitting performance of hematite electrodes. It was found that under illumination, the Co-Pi catalyst can efficiently collect and store photogenerated holes from the hematite electrode. This charge separation reduces surface state recombination which results in increased water oxidation efficiency. It was also found that thicker Co-Pi films produced increased water oxidation efficiencies which is attributed to a combination of superior charge separation and increased surface area of the porous catalytic film. These combined results provide important new understanding of the enhancement and limitations of the Co-Pi catalyst coupled with semiconductor electrodes for water-splitting applications.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Klahr
authors.forename: Sixto
authors.initials: S
authors.lastname: Gimenez
authors.forename: Francisco
authors.initials: F
authors.lastname: Fabregat-Santiago
authors.forename: Juan
authors.initials: J
authors.lastname: Bisquert
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Hamann