Integration of Gold Nanoparticles into BiVO/WO Photoanodes via Electrochromic Activation of WO for Enhanced Photoelectrochemical Water Splitting.

The development of highly efficient photoanodes is crucial for enhancing the energy conversion efficiency in photoelectrochemical water splitting. Herein, we report an innovative approach to fabricating an Au/BiVO/WO ternary junction that leverages the unique benefits of WO for efficient electron transport, BiVO for broadband light absorption, and Au nanoparticles (NPs) for surface plasmon effects. The BiVO/WO binary junction was constructed by depositing a BiVO layer onto the surface of the WO nanobricks via consecutive drop casting. Au NPs were subsequently integrated into the BiVO/WO structure through electrochromic activation of WO. The optimal BiVO loading for the highest-performing BiVO/WO heterostructure and the light intensity dependence of the photocurrent efficiency were also determined. Flat-band potential measurements confirmed an appropriate band alignment that facilitates electron transfer from BiVO to WO, while work function measurements corroborated the formation of a Schottky barrier between the incorporated Au NPs and BiVO/WO, improving charge separation. The best-performing Au NP-sensitized BiVO/WO photoanode thin films exhibited a photocurrent density of 0.578 mA cm at 1.23 V vs RHE under AM 1.5G (1 sun) illumination and a maximum applied-bias photoconversion efficiency of 0.036% at 1.09 V vs RHE, representing an enhancement factor of 12 and 2.3 compared to those of pristine BiVO and WO photoanodes, respectively. This study presents a promising and scalable route for fabricating noble metal-sensitized, metal oxide-based nanocomposite photoanodes for solar water splitting.