Enhanced photocatalytic performance of Ag/CdS by L-cysteine functionalization: Combination of introduced co-catalytic groups and optimized injection of hot electrons

Surface plasmonic resonance effect of Ag nanoparticles (NPs) can enhance the photocatalytic performance of CdS by the injection rate of hot electrons, but their low injection rate and serious carrier recombination of CdS need special attention. In this article, CdS nanosheets are pre-functionalized by L-cysteine (L-Cys) to graft –COO- and –NH2 groups, followed by the photo-deposition of Ag NPs, and strong chemical bonds are formed between CdS and Ag NPs with L-Cys as bridging ligands. Their optimal hydrogen evolution rate of 29.71 mmol/g/h is 4.13 and 2.30 times that of CdS and CdS-Ag without L-Cys, respectively, and its monochromatic apparent quantum efficiency at 450 nm reaches 27.87%. According to the enhancement factors of L-Cys functionalization, L-Cys acts as bridging ligands to enhance the interfacial injection rate of hot electrons. Meanwhile, the dangling –COO- and –NH2 groups on CdS can act as efficient co-catalytic centers.