Efficient photo-catalytic hydrogen production performance and stability of a three-dimensional porous CdS NPs-graphene hydrogel

Abstract

We designed a novel CdS nanoparticles composite graphene hydrogel. Under sunlight, the CdS nanoparticles (NPs) -reduced graphene oxide hydrogel (rGH) had the highest hydrogen production rate of 6.44 mmol/g, which is 1.3 times that of CdS nanoparticles (5.12 mmol/g) and 1.4 times that of CdS (4.6 mmol/g). The enhanced photo-catalytic activity can be attributed to several positive factors such as the formation of composite hydrogels and the quantum size effect of the CdS nanoparticles nanomaterials. The formation of the composite hydrogel improves the specific surface area of the catalyst and increases the active site on the catalyst surface. The quantum size effects of the CdS nanoparticles effectively reduce the recombination probability of electrons and holes. The close contact between the CdS nanoparticles and the graphene gel can effectively separate photo-generated electrons and holes via the unique large π-bond structure of graphene. These positive factors effectively improve the photocatalytic activity of composite materials for water decomposition. In addition, recovery experiments show a composite catalyst recovery rate of up to 95%. The results show that the composite photo-catalyst can effectively avoid secondary pollution during photo-catalytic hydrogen production. This eliminates powder recovery problems. The hydrogen production efficiency of the catalyst remains unchanged after 5 cycles indicating that the formation of the gel system stabilizes the catalyst and inhibits light corrosion of CdS nanoparticles.