Tungsten trioxide (WO3) is a widely used photoanode material in PEC water splitting, recognized for its exceptional properties. With a band gap of approximately 2.6 eV, WO3 efficiently absorbs visible light, making it suitable for solar energy applications. Its high chemical stability ensures long-term operation, while its excellent electron mobility promotes efficient charge transport. Additionally, the strong oxidizing power of WO3, attributed to its optimal valence band position, significantly enhances its performance in PEC processes . Moreover, WO3 can be combined with various semiconductors to further enhance its PEC performance. Commonly used semiconductors include iron oxide (Fe2O3) , polymeric carbon nitride (PCN) , copper oxide (Cu2O) , and bismuth vanadate (BiVO4) . Among these semiconductors, BiVO4 stands out as a promising candidate for use as a photosensitizer because it has a narrower band gap (~2.4 eV) than WO3 for extended light absorption and suitable band alignment with WO3 for effective charge separation. In our previous paper , BiVO4 NPs electrodeposited 3D hierarchal ZnO nanodendrites demonstrated an improved PEC response due to the significantly extended light absorption towards visible region of the solar spectrum. The synergistic effect of WO3 and BiVO4 leads to a higher photocurrent compared to using either material alone, driven by enhanced charge separation and improved utilization of the solar spectrum. Grigioni et al. have optimized the BiVO4 layer thickness on WO3, identifying a 75 nm thick BiVO4 layer as the best-performing photoelectrode . Furthermore, BiVO4 was applied on 1-dimensional (1D) WO3 nanorods, the resulting BiVO4/WO3 with optimal thickness produced a photocurrent up to 3.8 mA cm -2 at 1.23 V vs. RHE under simulated solar light . On the basis of the versatility in structural design, Liu et al. have shown that the PEC performance of WO3 strongly depends on its different crystal facets owing to different surface energies and electronic structures . In their research, it was underlined that WO3 with (002) facets generated the highest faradaic efficiency on PEC water splitting when preferentially exposed to the (020) BiVO4 facet due to better hole injection efficiency at the interface between the two materials.