An S-scheme SnS2/Bi(C2O4)OH heterojunction with oxygen vacancy synergy: One-Step hydrothermal fabrication and enhanced photocatalytic performance

First SnS 2 /Bi(C 2 O 4 )OH heterojunction via one-step hydrothermal method. • Sn–S–Bi bonds induce IEF for S-scheme charge transfer. • Oxygen vacancies and S-scheme synergy enhance redox ability and resist photocorrosion. • 94.3% TCH (15 mg/L) degraded in 30 min, 231-fold vs. SnS 2 . • 97.9% RhB (30 mg/L) degraded in 60 min, 17.2-fold vs. SnS 2 . This study reports the first construction of an S-scheme SnS 2 /Bi(C 2 O 4 )OH heterojunction via a one-step hydrothermal route. Combined X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses confirm strong interfacial coupling rather than physical mixing, while scanning electron microscopy (SEM) reveals a distinctive “snow-on-petals” morphology, with SnS 2 nanoparticles uniformly dispersed on Bi(C 2 O 4 )OH nanosheets. X-ray photoelectron spectroscopy (XPS) further confirms the presence of Sn–S–Bi interfacial bonds, accompanied by localized electron redistribution, laying the chemical foundation for S-scheme charge transfer. Electron paramagnetic resonance (EPR) analysis reveals a notable increase in oxygen vacancy content. This enrichment of oxygen vacancies, together with the chemical bonding at the S-scheme heterojunction interface, synergistically suppresses SnS 2 photocorrosion. Ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) shows substantially improved visible-light harvesting, and electrochemical impedance spectroscopy (EIS) and photocurrent measurements corroborate superior charge separation and transport efficiency. Interestingly, although the specific surface area of the composite (35.44 m 2 /g) is lower than that of pristine SnS 2 (103.24 m 2 /g), the composite exhibits markedly higher photocatalytic activity, indicating that the enhancement arises from interfacial charge transfer and electronic modulation rather than from surface area alone. Consequently, the 30%SnS 2 /Bi(C 2 O 4 )OH composite achieves 93.4% removal of tetracycline hydrochloride (15 mg L −1 ) within 30 min and 97.9% removal of rhodamine B (30 mg L −1 ) within 60 min, with apparent rate constants of 231 and 17.2 times those of pure SnS 2 . Radical scavenging tests identify ·O 2 − and h + as the dominant reactive species, while total organic carbon (TOC) analysis indicates a mineralization rate of 77.1% for TCH, confirming deep oxidation beyond mere decolorization. Coupled with liquid chromatography–mass spectrometry (LC–MS) elucidation of the degradation pathway, this work offers a new paradigm for the rational design of high-performance S-scheme heterojunctions through interfacial chemical bonding and defect engineering. Graphical : Photocatalytic Degradation Mechanism. Download: Download high-res image (243KB) Download: Download full-size image