All-Solution-Processed WO₃/BiVO₄ Core–Shell Nanorod Arrays for Highly Stable Photoanodes

Tungsten oxide (WO₃) and bismuth vanadate (BiVO₄) are one of the most attractive combinations to construct an efficient heterojunction for photoelectrochemical (PEC) applications. Here, we report an all-solution-processed WO₃/BiVO₄ heteronanostructure photoanode with highly enhanced photoactivity and stability for sustainable energy production. The vertically aligned WO₃ nanorods were synthesized on a fluorine-doped tin oxide/glass substrate by the hydrothermal method without a seed layer and BiVO₄ was deposited by pulsed electrodeposition for conformal coating. Owing to the long diffusion lengths of charge carriers in the WO₃ nanorods, the ability to absorb the wider range of wavelengths, and appropriate band-edge positions of the WO₃/BiVO₄ heterojunction for spontaneous PEC reaction, the optimum WO₃/BiVO₄ photoanode has a photocurrent density of 4.15 mA/cm² at 1.23 V versus RHE and an incident-photon-to-current efficiency of 75.9% at 430 nm under front illumination, which are a double and quadruple those of pristine WO₃ nanorod arrays, respectively. Our work suggests an environment-friendly and low-cost all-solution process route to synthesize high-quality photoelectrodes.