Branched WO3 nanosheet array with layered C3 N4 heterojunctions and CoOx nanoparticles as a flexible photoanode for efficient photoelectrochemical water oxidation.

A hybrid WO3 /C3 N4 /CoOx system exhibits excellent photoelectrochemical activity for water oxidation. The system comprises a novel three-dimensionally branched WO3 nanosheet array coated with a layer of C3 N4 heterojunctions that are further decorated with CoOx nanoparticles. The photoelectrochemical activity arises from the effective light harvesting due to the 3D structure and "window effect," the excellent charge separation and transport in the heterojunction, and the fast interfacial charge collection and surface reactions due to the large surface area.