Earth-abundant metal oxide semiconductors are considered promising materials for solar water splitting due to their economic feasibility in device fabrication. In general, n-type metal oxide semiconductors such as Fe2O3 (2.1 eV) , BiVO4 (2.4 eV) , and WO3 (2.6 eV) have been extensively studied as photoanode candidates for solar water oxidation. These n-type semiconductors are well known for forming favorable upward band bending at the semiconductor/electrolyte interface, with a suitable valence band edge positioned below the water oxidation potential, facilitating efficient hole transfer. Despite significant improvements in photoelectrochemical (PEC) efficiency that have been achieved with n-type metal oxide semiconductors, challenges remain in achieving high photocurrent densities comparable to those observed in PEC hydrogen evolution using p-type photocathodes such as Sb2Se3, InP, and Si (>15 mA cm -2 ) . For example, the relatively large bandgap of n-type semiconductors limits the theoretical maximum photocurrent density (<8 mA cm -2 for BiVO4) , and the short minority carrier diffusion lengths (~100 nm for BiVO4 and ~4 nm for Fe2O3) and low carrier mobility restrict the photoelectrode thickness to less than 200 nm, thereby reducing light absorption . Furthermore, the synthesis of metal oxides on conductive glass substrate (e.g., fluorine-doped tin oxide and indium tin oxide) often requires low-temperature processing (<500 °C) due to their low thermal stability . This results in small grain sizes and low crystallinity of metal oxide semiconductors, which in turn promote rapid charge recombination and low carrier mobility .