In this work, BiVO₄ is selected as effective light-harvesting material to replace conventional unstable dye-sensitized photosensitizer ([Ru(bpy)₃]²⁺) that easily occurs photodecomposition during artificial photosynthetic system. The addition of an eleven iron-containing polyoxometalate (Fe₁₁POM) as efficient cocatalyst illustrates a dramatically improved photocatalytic water oxidation performance compared with that of pure BiVO₄. Through careful characterization and analysis of selected-area, highly selective in-situ photo-deposition of Fe₁₁POM into ultrathin nanofilm on the decisive 110 facet of BiVO₄ under ultrapure water is clearly observed, and an intimate connection between nanofilm and hole-rich 110 facet is obtained in favor of enhancing surface catalytic efficiency. The exquisite decoration of ultrathin nanofilm can be further clarified as FeO_x decomposed from Fe₁₁POM, which could effectively capture the photogenerated holes and suppress the recombination of electron–hole pairs for promoting water oxidation performance through fast interfacial hole transfer process.