Metal (Ni2+/Co2+) sulfides modified BiVO4 for effective improvement in photoelectrochemical water splitting.

The performance of BiVO4 for photoelectrocatalytic (PEC) water decomposition is commonly limited by reaction kinetics. In this work, NiS and CoS nanospheres were respectively loaded on BiVO4 thin films (NiS/BiVO4 and CoS/BiVO4 composites) to improve its reaction kinetics for PEC water decomposition. Both physical and chemical properties of these composites were characterized by XRD, SEM, TEM, PL and UV-DRS. The photoelectric properties of the samples were verified by testing LSV, i-t, EIS and IPCE. The formation of the composites can effectively prevent the recombination of carriers and consequently accelerate the separation of electrons and holes. NiS/BiVO4 and CoS/BiVO4 can reach photocurrent of 2.1 mA cm-2 and 2.7 mA cm-2 under light respectively, at 1.23 V vs. RHE, which are 1.75 times and 2.25 times that of BiVO4 (1.2 mA cm-2). The hydrogen production of the NiS/BiVO4 and CoS/BiVO4 photoanodes was 4.7 and 7.3 times higher than that of BiVO4 photoanode, respectively.