Defective Bi2WO6-Supported Cu Nanoparticles as Efficient and Stable Photoelectrocatalytic for Water Splitting in Near-Neutral Media

Defective Bi2WO6-supported Cu nanoparticles photoelectrocatalyst were successfully synthesized via an etching approach by using NaBH4 as reducing agent. The as-prepared Cu/Bi2WO6-1 was dominated by CuO and Cu and Cu/Bi2WO6-2 was dominated by metallic Cu, confirmed by XPS and TEM analyses. These etching pretreatments also induced the formation of defect sites such as oxygen vacancies and W5+. The presence of oxygen vacancies could significantly increase the photogenerated electrons capture abilities. Metallic Cu nanocrystals on the surface of Bi2WO6 photoanodes are beneficial for the photoresponse range as well as the separation and consumption of photogenerated carriers due to the surface plasmon resonance effect of Cu. Photoelectrochemical studies demonstrated that Cu/Bi2WO6-x exhibited a markedly improved PEC performance in water splitting reaction as compared to that of Bi2WO6 which mainly because of the light harvesting efficiency (eta(abs)) and the interfacial charge transfer efficiency. Importantly, Cu/Bi2WO6-2 exhibited the best PEC activity with a high current density and good stability under neutral conditions, which may be ascribed to the defective Bi2WO6 structure in combination with surface ligand engineering and the synergistic effect of oxygen vacancies and metallic Cu. In addition, the function mechanism of CuO, metallic Cu and oxygen vacancies were discussed in details.