Innovation synthesis of NiS quantum dots modified CdS/WO3 heterostructures as high-efficiency bifunctional photocatalysts for construction of visible light driven Z-scheme water-splitting and Cr (VI) degradation

Solar-driven water splitting and pollution treatment have aroused the researchers' considerable attention for further developing and applying clean energies. Herein, to be inspired by artificial photosynthesis, we designed and constructed direct Z-Scheme system by using multi-dimensional catalysts. CdS (1D nanorod)/WO3 (2D nanosheet) direct Z-Scheme heterostructures were prepared by the chemical in-situ growth combining with physical electrostatic adsorption method, meanwhile, NiS (0D quantum dots) were loaded on CdS surface acting as cocatalyst. It was found that the NiS-CdS/WO3 (NCW) Z-scheme photocatalyst could efficiently utilize solar spectrum, furthermore, photogenerated carriers separated and transferred quickly under the effect of built-in electric field in the space charge region. Accordingly, NCW10 showed an outstanding photocatalytic activity on H-2 production rate of 70.73 mmol.h(-1).g(cat)(-1) and Cr(VI) degradation rate of 33.3 mu mol.h(-1).g(cat)(-1), which is about 7 times and 4.2 times higher than those of reference CdS, respectively. Thereby, this noble-metal-free Z-scheme heterostructures exhibit a high apparent quantum yield (AQY) of 24.83% at 420 nm and long-term stability. This modified synthesized method optimizes the structure and property of photocatalyst, in addition, the further interpretation for carrier charge transfer mechanism of direct Z-Scheme catalyst would provide reference and guidance for the selection and development of solar-conversion system.