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 TiO 2 /H 3 PW 12 O 40 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 TiO 2 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.