A Macroporous-Structured WO3/Mo-Doped BiVO4 Photoanode for Vapor-Fed Water Splitting under Visible Light Irradiation

Bismuth vanadate (BiVO4) is a promising material for visible-light-induced photoelectrochemical (PEC) water splitting. The strategies of cation doping and formation of heterojunctions with tungsten trioxide have improved the efficiency of BiVO4 photoanodes by suppressing the recombination of photogenerated electrons and holes. In this study, we present a simple dip-coating method to prepare WO3/BiVO4 heterojunctions on titanium microfiber felt. The gas diffusion structure of Ti felt is suitable for a vapor-fed photoelectrolysis of water using a proton exchange membrane (PEM). Molybdenum is utilized as a dopant to enhance the PEC performance of the BiVO4 layer. The combined effect of the WO3 underlayer and the Mo doping significantly improved the PEC performance of the macroporous-structured photoanode under visible light irradiation. The incident photon-to-current conversion efficiency (IPCE) of Ti/WO3/Mo-doped BiVO4 reached 10.7% under 454-nm blue light irradiation at 1.2 V versus the reversible hydrogen electrode. The coating of Nafion ionomer thin films significantly enhanced the photocurrent response of the macroporous photoanode in the vapor-fed condition. The measurement of the H2 and O2 evolution indicates that the ionomer-coated Ti/WO3/Mo-doped BiVO4 photoanode is beneficial for the vapor-fed water splitting in the PEM-PEC system.