Surface Engineered Doping of Hematite Nanorod Arrays for Improved Photoelectrochemical Water Splitting

Given the narrow band gap enabling excellent optical absorption, increased charge carrier density and accelerated surface oxidation reaction kinetics become the key points for improved photoelectrochemical performances for water splitting over hematite (alpha-Fe2O3) photoanodes. In this study, a facile and inexpensive method was demonstrated to develop core/shell structured alpha-Fe2O3 nanorod arrays. A thin, Ag-doped overlayer of similar to 2-3 nm thickness was formed along alpha-Fe2O3 nanorods via ultrasonication treatment of solution-based beta-FeOOH nanorods in Ag precursor solution followed by high temperature annealing. The obtained alpha-Fe2O3/AgxFe(2-x)O(3) core/shell nanorod films demonstrated much higher photoelectrochemical performances as photoanodes than the pristine alpha-Fe2O3 nanorod film, especially in the visible light region; the incident photon-to-current efficiency (IPCE) at 400 nmwas increased from 2.2% to 8.4% at 1.23 V vs. RHE (Reversible hydrogen electrode). Mott-Schottky analysis and X-ray absorption spectra revealed that the Ag-doped overlayer not only increased the carrier density in the near-surface region but also accelerated the surface oxidation reaction kinetics, synergistically contributing to the improved photoelectrochemical performances. These findings provide guidance for the design and optimization of nanostructured photoelectrodes for efficient solar water splitting.