Synergistic sulfur vacancy and polydopamine engineering in Sv-CdS@PDA Z-scheme heterojunctions for photocatalytic H2O2 production with robust anticorrosion

Metal sulfides like CdS hold promise for solar-driven H 2 O 2 productions but suffer from rapid charge recombination and severe photocorrosion. This study introduces a dual-functional strategy synergizing sulfur vacancy (S v ) engineering and polydopamine (PDA) coating to overcome these limitations. S v -CdS nanorods were hydrothermally synthesized with tunable vacancy concentrations, followed by in-situ PDA deposition to construct a direct Z-scheme heterojunction. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveal that the introduction of S vacancies reduces the work function of CdS, facilitating energy level alignment with PDA and enabling efficient electron transfer from CdS to PDA. By tuning the concentration of S vacancies, the charge transfer efficiency can be maximized. As a result, the photocatalytic H 2 O 2 production rate reaches 2539.5 µmol g −1 h −1 under visible light, and further increases to 4395.5 µmol g −1 h −1 after PDA encapsulation —15.6 times higher than that of pristine CdS. Concurrently, PDA enhances O 2 adsorption and protects S v -CdS from photocorrosion. S v -CdS@PDA exhibited superior photostability compared to S v -CdS after three consecutive photocatalytic cycles. Mechanistic studies suggest that the Z-scheme heterojunction effectively separates electron-hole pairs: electrons in the conduction band of CdS reduce O 2 to ·O 2 − , which is subsequently converted to H 2 O 2 , while holes in the valence band of S v -CdS oxidize water to replenish O 2 . This work provides fundamental insights into engineering charge transfer and stability in sulfide-based photocatalysts.