Reactive Sputtering of Bismuth Vanadate Photoanodes for Solar Water Splitting

Abstract

Bismuth vanadate (BiVO4) has attracted increasing attention as a photoanode for photoelectrochemical (PEC) water splitting. It has a band gap in the visible light range (2.4–2.5 eV) and a valence band position suitable for driving water oxidation under illumination. While a number of methods have been used to make BiVO4 photoanodes, scalable thin film deposition has remained relatively underexplored. Here, we report the synthesis of BiVO4 thin films by reactive sputtering. The use of separate Bi and V sputtering targets allows control of the Bi/V ratio in the film. Under optimized, slightly V-rich conditions, monoclinic phase BiVO4 with photoactivity for water oxidation is obtained. The highest photocurrents, ca. 1 mA cm–2 at the reversible O2/H2O potential with simulated AM 1.5G illumination, are obtained with bilayer WO3/BiVO4, where the WO3 serves as a hole-blocking layer.