Enhancing photocatalytic H2O2 production via dual optimization of charge separation and O2 adsorption in Au-decorated S-vacancy-rich CdIn2S4

Photocatalytic oxygen reduction reaction (ORR) offers a mild and cost-effective approach for hydrogen peroxide (H₂O₂) production. However, its practical application is significantly hindered by rapid charge carrier recombination and insufficient O₂ adsorption capacity in photocatalysts. To address these limitations, we developed a strategy involving the creation of S-vacancy-rich CdIn₂S₄ (S_v–CIS) to facilitate charge separation and subsequent deposition of Au nanoparticles on its surface (Au–S_v–CIS) to strengthen O₂ adsorption. The results suggest that the optimized Au–S_v–CIS achieves a significantly increased H₂O₂ production yield of 2542 μmol⁻¹ h g⁻¹ in 10 %-ethanol/water solution, which is about 12.8 and 1.7 times higher than that of pure CIS and S_v–CIS. Comprehensive characterizations including photoluminescence spectra, time-resolved photoluminescence spectra, transient photocurrent response, electrochemical impedance spectra, and femtosecond transient absorption spectroscopy confirm the improved charge dynamics of Au–S_v–CIS. In addition, temperature-programmed desorption of O₂ combined with density functional theory calculations conclusively demonstrates the superior O₂ adsorption capacity of Au–S_v–CIS. This work provides a design strategy for efficient solar–to–chemical energy conversion through cooperative photocatalyst engineering.