A kind of Co(OH)(2)-modified CuO nanoparticles (Co(OH)(2)/CuO) was found to be a robust catalyst for the water oxidation reaction (WOR) in sacrificial oxidant conditions without any photosensitizers since this conjunction possessed both catalytic sites and visible light absorption centers. Under the synergetic effect between Co(OH)(2) and CuO clusters, Co(OH)(2)/CuO afforded an excellent high oxygen output ratio (1955 ymol.h(-1).g(-1)). According to electron spin resonance measurements and radical capture experiments, sulfate radicals were confirmed as the main active species. The results of DFT simulations demonstrated that Co(OH)(2)/CuO was a kind of metal-semiconductor complex, which was inclined to transfer charge carriers across the interface efficiently and unidirectionally. Based on the locations of the valence band and conduction band, the mechanism of the photocatalytic WOR was proposed. We hope that this contribution will offer useful guidance for developing efficient photoinduced charge-transfer water-oxidation catalysts without photosensitizers.