Integration of gold nanoparticles into BiVO4/WO3 photoanodes via electrochromic activation of WO3 for enhanced photoelectrochemical water splitting

The development of highly efficient photoanodes plays a pivotal role in advancing energy conversion efficiency in photoelectrochemical (PEC) applications. Herein, we report a facile approach to fabricate Au/BiVO4/WO3 ternary junction, which stands out by harnessing the unique benefits of WO3 for efficient electron transport, BiVO4 for broadband light absorption, and Au NPs for surface plasmon effects. The BiVO4/WO3 binary junction was constructed by depositing the BiVO4 layer on the surface of WO3 nanobricks through consecutive drop-casting. Au NPs were subsequently integrated into BiVO4/WO3 via the electrochromic activation of WO3. The optimal loading amount of BiVO4 for the best-performing BiVO4/WO3 heterostructure and the light intensity dependency of the photocurrent efficiency were determined. Work function measurements suggest a Schottky barrier forms between the incorporated Au NPs and BiVO4/WO3, leading to an improved charge separation. The flat band measurements signify an appropriate band alignment with a viable electron transfer from BiVO4 to WO3. The best-performing Au NPs-sensitized BiVO4/WO3 photoanode thin films exhibited a photocurrent density of 0.578 mA cm–2 at 1.23 V vs. RHE under AM 1.5G (1 sun) illumination, and a maximum applied-bias photoconversion efficiency (ABPE) of 0.036% at 1.09 V vs. RHE, which is an enhancement by a factor of 12 and 2.3 with respect to pristine BiVO4 and WO3 photoanodes, respectively. The present study offers a promising and scalable route for fabricating a noble metal-sensitized metal oxide-based nanocomposite photoanode for solar water splitting.