Bimetallic Ni–Co-ZIF derived (Ni, Co)Se2/BiVO4 heterojunction photoelectrodes with oxygen vacancy for enhancing PEC performance

Bismuth vanadate (BiVO4) still limits its practical application due to its poor water oxidation kinetics and easy surface charge recombination. In this paper, bimetallic Ni–Co-zeolitic imidazolate frameworks (Ni–Co-ZIF) was successfully transformed into metal oxides and selenides modified on the surface of BiVO4 ((Ni, Co)Se2/BiVO4) by electrostatic adsorption and pyrolytic selenization methods to further improve the photoelectrochemistry (PEC) performance of BiVO4. In the presence of (Ni,Co)Se2 layer, the best photocurrents of (Ni, Co)Se2/BiVO4 heterojunction photoelectrodes reached to 3.30 mA/cm2, which is better than the pure BiVO4 with about 4.07 times. The reason for PEC performance enhancement of (Ni, Co)Se2/BiVO4 since that the bimetallic (Ni,Co)Se2 with more metal active sites and oxygen vacancy takes advantage of the strong conductivity of charges to improve the charge separation and transfer efficiency. Meanwhile, these (Ni, Co)Se2/BiVO4 photoelectrodes have shown more stability in alkaline electrolyte solutions.