Al-doped ZnO inverse opal networks as efficient electron collectors in BiVO4 photoanodes for solar water oxidation

Abstract

The short diffusion length of photogenerated charge carriers limits the performance of photoelectrodes for solar water splitting. To reduce the distance between where the charges are generated and the location they are scavenged, a conductive Al-doped ZnO inverse opal network is introduced into a BiVO₄ photoanode. The conductive inverse opal network serves as an electron collector for the BiVO₄ film, which suffers from poor electron transport. The combined heterostructure provides a photocurrent of 1.5 mA cm⁻² at 1.23 V vs. RHE, which is threefold higher than a BiVO₄ photoanode without any conducting inverse opal network. The significantly enhanced photocurrent produced without intentional doping or oxygen-evolving catalysts, indicates the importance of charge transport and collection in photoelectrodes. Our design has the potential to be applied to other photoelectrochemical systems to improve charge collection and solar energy conversion efficiency.