Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst

Jing Gu; Yong Yan; James L Young; K Xerxes Steirer; Nathan R Neale; John A Turner

doi:10.1038/nmat4511

Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst

Nat Mater. 2016 Apr;15(4):456-60. doi: 10.1038/nmat4511. Epub 2015 Dec 21.

Authors

Jing Gu¹, Yong Yan¹, James L Young^{1

2}, K Xerxes Steirer¹, Nathan R Neale¹, John A Turner¹

Affiliations

¹ National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, Colorado 80401, USA.
² Material Science and Engineering Program, University of Colorado, Boulder, Colorado 80309, USA.

PMID: 26689139
DOI: 10.1038/nmat4511

Abstract

Producing hydrogen through solar water splitting requires the coverage of large land areas. Abundant metal-based molecular catalysts offer scalability, but only if they match noble metal activities. We report on a highly active p-GaInP2 photocathode protected through a 35-nm TiO2 layer functionalized by a cobaloxime molecular catalyst (GaInP2-TiO2-cobaloxime). This photoelectrode mediates H2 production with a current density of ∼9 mA cm(-2) at a potential of 0 V versus RHE under 1-sun illumination at pH 13. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9 s(-1). Bare GaInP2 shows a rapid current decay, whereas the GaInP2-TiO2-cobaloxime electrode shows ≤5% loss over 20 min, comparable to a GaInP2-TiO2-Pt catalyst particle-modified interface. The activity and corrosion resistance of the GaInP2-TiO2-cobaloxime photocathode in basic solution is made possible by an atomic layer-deposited TiO2 and an attached cobaloxime catalyst.