Visible Light Driven Photoelectrochemical Water Oxidation by Zn- and Ti-Doped Hematite Nanostructures

Abstract

The electrodeposition method was used for modification of a nanostructured hematite photoanode with Ti and Zn to improve the photoelectrocatalytic performance of hematite in the water splitting reaction. The photoelectrocatalytic activity of the hematite electrodes modified with Ti 4+ and Zn 2+ was optimized through the controlled variation of the dopant ion concentration in the electrodeposition solution. Under optimized conditions, for standard illumination of AM 1.5G (100 mW cm –2 ), the photocurrent density at the Ti/Zn-modified hematite anode reached 1.5 mA cm –2 at 1.23 V vs RHE that was 2.5-times higher than that observed with the pristine hematite electrode, the photoelectrocatalysis onset potential being 63 mV reduced. Effects of Ti and Zn doping on the photoelectrochemical activity of pristine hematite were studied by scanning electron microscopy, UV–vis spectroscopy, elemental analysis, and electrochemical impedance spectroscopy. On the basis of the obtained results, the improved performance of the Ti/Zn-modified hematite stemmed from the combination of the enhanced electrical conductivity along with the facilitated charge transport in the bulk phase and at the surface of hematite. The effect of Zn-doping decreasing the overpotential of the reaction by 218 mV (solely Zn-doped compared to that of the pristine hematite) was correlated with the Zn contribution to the interfacial catalysis of water oxidation.