Copper vacancy activated plasmonic Cu3−xSnS4 for highly efficient photocatalytic hydrogen generation: Broad solar absorption, efficient charge separation and decreased HER overpotential

Broad absorption spectra with efficient generation and separation of available charge carriers are indispensable requirements for promising semiconductor-based photocatalysts to achieve the ultimate goal of solar-to-fuel conversion. Here, Cu3−xSnS4 (x = 0−0.8) with copper vacancies have been prepared and fabricated via solvothermal process. The obtained copper vacancy materials have extended light absorption from ultraviolet to near-infrared-II region for its significant plasmonic effects. Time-resolved photoluminescence shows that the vacancies can simultaneously optimize charge carrier dynamics to boost the generation of long-lived active electrons for photocatalytic reduction. Density functional theory calculations and electrochemical characterizations further revealed that copper vacancies in Cu3−xSnS4 tend to enhance hydrogen’s adsorption energy with an obvious decrease in its H2 evolution reaction (HER) overpotential. Furthermore, without any loadings, the H2 production rate was measured to be 9.5 mmol·h−1·g−1. The apparent quantum yield was measured to be 27% for wavelength λ > 380 nm. The solar energy conversion efficiency was measured to be 6.5% under visible-near infrared (vis-NIR) (λ > 420 nm).