Multifunctional WO3/NiCo2O4 heterojunction with extensively exposed bimetallic Ni/Co redox reaction sites for efficient photoelectrochemical water splitting

Abstract The enhanced separation and injection efficiencies of photogenerated carriers is essential to improve the photoelectrochemical (PEC) performance of WO 3 photoanode. In this work, we firstly synthesized WO 3 /NiCo 2 O 4 heterojunction through simple hydrothermal‐annealing method as well as investigate the effect and mechanism of NiCo 2 O 4 on WO 3 for PEC performances. The measurements demonstrate that the nano‐needle NiCo 2 O 4 grown on the surface of WO 3 induces the bimetallic Ni/Co redox reaction sites extensively exposed to the electrolyte, which is beneficial to enhance the PEC performances of WO 3 photoanode, such as photocurrent density improved by four times (0.84 mA/cm 2 at 1.23 V vs. RHE) as well as more negative initial potential (∼280 mV) in contrast to bare WO 3 . Further investigation shows the remarkable enhancement of PEC performances is attributed to improved surface reaction kinetics, the enhanced injection efficiency and separation efficiency of photogenerated carriers due to the co‐catalyst effect of NiCo 2 O 4 and the formation of WO 3 /NiCo 2 O 4 heterojunction. This work provides reference for application of heterojunction with co‐catalyst function, which is beneficial to the development and application of similar structures.