The PEC performance tests of BiVO4, WO3, BiVO4/WO3, and Au/BiVO4/WO3 photoanodes were conducted in a PEC cell (spectro-EC, Redox.me) using a three-electrode configuration. In this setup, the samples served as working electrodes, Pt wire acted as the counter electrode, and Ag/AgCl (saturated with NaCl) was used as the reference electrode. Illumination was provided by a Pico TM solar simulator (G2V Optics) with a standard AM 1.5G filter, delivering a light intensity of 87.5 mW cm -2 . All measurements were performed on frontside illuminated electrodes with a constant area of ~1.0 cm 2 . The aqueous solution of 0.5 M Na2SO4 with pH 7 was used as an electrolyte. The electrolyte was purged by nitrogen for 10 min prior to the measurements.