To enhance the efficiency of solar water splitting with the BiVO4/WO3 photoanode, this heterojunction was further integrated with additional materials, including co-catalysts, passivation layers, and plasmonic nanoparticles (NPs). For instance, Ma et al. have concluded that the oxygendeficient ZnO as a passivation layer can remarkably improve the surface water oxidation kinetics of BiVO4/WO3 heterostructure . Zhang et al. have reported that the decoration of cobalt phosphate (Co-Pi) co-catalyst on the conformally BiVO4 layered WO3 nanoplates promoted the water oxidation kinetics and photostability . In a study utilizing plasmonic nanoparticles, the large Au NPs at the bottom layer served as reflector and current collector, while the small Au NPs at the top layer functioned as antenna, thereby a strong electromagnetic field was induced due to the coupling interaction between the reflector and antenna, which facilitated the charge separation and enhanced the PEC activity of the BiVO4/WO3 thin film . Furthermore, decoration of Au NPs onto BiVO4 by citrate method resulted in strong metal/support interaction and the hybrid nanocomposite generated a photocurrent of 6.25 mA cm -2 at 1.23 V vs. RHE after FeOOH/NiOOH OER cocatalyst modification . The surface plasmon resonance (SPR) phenomenon is intrinsically related to the plasmonic NPs and is typically observed between 517 and 575 nm for Au NPs . In addition to the SPR advantage, a Schottky barrier naturally forms at the interface of the metal/semiconductor junction, increasing the charge separation rate and contributing to the photocurrent for water splitting.