rGO decorated semiconductor heterojunction of BiVO4/NiO to enhance PEC water splitting efficiency

Monoclinic phase of BiVO4 is a promising photoanode material for photoelectrochemical (PEC) water splitting, but its sluggish water oxidation kinetics and frequent bulk charge recombination greatly reduce its efficiency of PEC water splitting. A novel BiVO4/NiO/rGO photoanode was very simply prepared by electrodeposition, solution immersion and spin coating methods, in particular, the solution immersion method to loading NiO has never been reported in PEC research. Compared with BiVO4, the photocurrent density of the ternary photoanode reaches 1.52 mA/cm2 at 1.23 V vs RHE, which is 2.41 and 1.39 times higher than that of pure BiVO4 and binary BiVO4/NiO photoanode, respectively. The onset potential of the ternary photoanode shows a significant cathodic shift of 130 mV compared with the BiVO4 photoanode. Moreover, the measured incident photon-to-current efficiency (IPCE) value reaches 50.52% at λ = 420 nm. The improvement is attributed to the type-II heterojunction formation that enhances the separation efficiency of electron/hole and the rGO decoration that accelerates the electron transfer and provides more active sites for gas adsorption.