All-solid-state Z-scheme system of NiO/CDs/BiVO4 for visible light-driven efficient overall water splitting

Abstract

Solar light driven photocatalytic water splitting to produce hydrogen (H2) and oxygen (O2) on large scale is a promising solution to acquire the clean and sustainable energy sources. Enlightened by mimicking natural Z-scheme photosynthesis, the artificial visible light-driven water splitting photocatalyst of NiO/carbon dots/BiVO4 (NiO/CDs/BiVO4) composite was constructed. The designed NiO/CDs/BiVO4 as all-solid-state Z-scheme photocatalyst exhibits efficient photocatalyatic activity for overall water splitting without any cocatalysts or scavengers. In the Z-scheme system, the NiO and BiVO4 can respectively act as H2 evolution and O2 evolution photocatalysts, while the CDs can serve as solid electron mediator. The optimal NiO/CDs/BiVO4 photocatalyst shows the H2 and O2 production rates of 1.21 and 0.60 μmol·h−1, respectively, with the CDs concentration in the composite of 5 wt% and the mass ratio of NiO to BiVO4 of 3. The incorporation of CDs employed as the solid-state electron mediator boosts the effective electron transfer and charges separation, resulting in the improved photocatalytic activity of the designed Z-scheme system.