Precise Analysis of Surface Adsorption Process on TiO ₂ /H ₃ PW ₁₂ O ₄₀ during Photocatalytic Degradation through UV–Vis/SERS Technique

While porous catalysts enhance photocatalytic efficiency through improved pollutant adsorption, conventional spectroscopic methods often conflate adsorption equilibria with degradation kinetics. This study pioneers the application of surface-enhanced Raman spectroscopy (SERS) in precisely tracking interfacial molecular transformations during malachite green (MG) degradation on sol-gel solvothermally synthesized TiO₂/H₃PW₁₂O₄₀ composite catalysts. Dual UV-Vis/SERS analysis revealed critical discrepancies between solution-phase and interfacial processes, enabling a redefinition of the true degradation rate─determined as 60.70% under visible light and 72.56% under UV irradiation. The composite exhibited remarkable performance enhancements: 10× and 5× greater degradation rates than pristine TiO₂ under visible (420-800 nm) and UV (λ < 420 nm) irradiation, respectively. The maximum total removal rate of MG was 92.51%. This improvement is attributed to enhanced charge carrier separation efficiency and synergistic Brønsted-Lewis acidity. This work underscores the combined use of UV-Vis and SERS as an indispensable approach for elucidating interfacial mechanisms in advanced photocatalysis.