Regulation of surface oxygen species to boost charge steering for solar water oxidation

Surface oxygen species, as products of defect-engineered nanomaterials, are vital to regulating the properties of electrode materials. Most studies have focused so far on the positive role of surface oxygen species, while ignoring their possible negative effects. Here, we developed a model photoanode for solar water oxidation by treating ZnO nanorod arrays with solvated electrons, which induced rich oxygen vacancies and oxygen containing moieties. The results show that oxygen vacancies lower the interfacial charge transfer resistance and lift the energy band edges of the photoanode surface, which drives the photo-generated holes toward the surface for water oxidation. However, the other oxygen groups tend to confine the migration of charge carriers resulting in a trapping of charges, thus hindering the overall solar conversion process. This work may shed new light on improving the photoelectrochemical water splitting system by clarifying the effects of different surface oxygen species.