Construction of BiVO4/NiCo2O4 nanosheet Z-scheme heterojunction for highly boost solar water oxidation

A Z-scheme BiVO4/NiCo2O4 (BVO/NCO) heterojunction structure was constructed by modifying optimal ultrathin nickel–cobalt (NiCo2O4) spinel nanosheets on BiVO4 as an efficient photocatalyst toward water oxidation, which deliver an excellent photocatalytic O2 evolution performance of 1640.9 μmol∙g−1∙h−1 by reducing the energy barriers and enhancing the separation and transfer of photogenerated carriers. [Display omitted] The sluggish water oxidation process is a severe obstacle for solar-driven water splitting. Therefore, it is imperative to develop a suitable photocatalyst with reduced energy barrier for strong oxidation. In this study, a Z-scheme BiVO4/NiCo2O4 (BVO/NCO) heterojunction system was designed by decorating ultrathin nickel–cobalt (NiCo2O4) spinel nanosheets on BiVO4 as an efficient photocatalyst for water oxidation. The unique structure of the system significantly reduced the energy barrier and improved the oxidation ability of BiVO4 to efficiently enhance the separation and transfer of the photogenerated carriers. Thus, the photocatalyst delivered an excellent O2 evolution performance of 1640.9 μmol∙g−1∙h−1 and showed 124% improved efficiency as compared to pristine BiVO4 and a quantum efficiency of 5.39% at 400 nm for O2 evolution. Additionally, the theoretical calculations revealed that the formation of *OOH was the rate-determining step for water oxidation. The decoration with NiCo2O4 significantly reduced the energy barrier between *O and *OOH, which eventually improved the photocatalytic performance of BVO/NCO. The results hold great promise for the potential application of spinel-based materials in efficient photocatalytic O2 evolution and offer fundamental insights into the design of efficient water oxidation heterojunctions.