S-scheme CdS/Ag/V2O5 heterostructure for efficient visible-light-driven hydrogen production

Abstract

To address the limited activity and stability of V₂O₅ (VO) in photocatalytic H₂ evolution, an S-scheme heterojunction photocatalyst, denoted as CS/Ag/VO, was developed by loading CdS (CS) onto Ag-decorated VO (Ag/VO) through a two-step hydrothermal–solvothermal route. The structural and optical properties of the as-prepared catalysts were systematically characterized, and their photocatalytic H₂ evolution performance was evaluated using TEOA as a sacrificial electron donor and in situ-generated Pt⁰ as a cocatalyst. The results show that Ag is present as highly dispersed nanoparticles and that CS is uniformly immobilized on the Ag/VO surface, which establishes intimate interfacial contact among the three components. Remarkably, the optimal CS/Ag/VO composite delivered a superior H₂ yield of 9634 μmol·g⁻¹ under visible light—5.29, 3.82, and 1.82 times greater than that of individual VO, CS, and Ag/VO, respectively—while maintaining 86.3% of its initial activity over six cycles, exhibiting robust stability. X-ray photoelectron spectroscopy (XPS), Mott-Schottky (M-S), and electron spin resonance (ESR) analyses reveal that a built-in electric field (IEF) directed from CS to VO is formed at their interface. This IEF, along with band bending, facilitates the S-scheme charge migration pathway. In this mechanism, low-activity photogenerated electron–hole pairs (PEHP) recombine in the interfacial region, while the strongly reducing electrons (enriched in the conduction band (CB) of CS) and the strongly oxidizing holes (enriched in the valence band (VB) of VO) are preserved. These retained charges effectively drive proton reduction and sacrificial-agent oxidation, respectively, synergistically enhancing the photocatalytic H₂ evolution performance. Furthermore, the material maintained high H₂ evolution activity even in common water bodies such as tap water and river water under TEOA-assisted and Pt-cocatalyzed conditions, demonstrating its tolerance to real-water matrices and its potential for practical application in a sacrificial-agent-assisted system. This study provides a solid experimental basis and a valuable theoretical reference for designing high-efficiency, stable S-scheme heterojunction photocatalysts.