A Study on the Photothermal Catalytic Performance of Pt@MnO₂ for O-Xylene Oxidation

Photothermal catalysis has emerged as a promising approach for the efficient and cost-effective removal of volatile organic compounds (VOCs). Pt@MnO₂ catalysts have demonstrated excellent performance in the photothermal catalytic oxidation of VOCs. However, current research has predominantly focused on the interaction between Pt and MnO₂, while often overlooking the influence of the MnO₂ crystal phase. Therefore, in this study, we synthesized Pt supported on four crystal phases (α, β, γ, and δ) of MnO₂ and established the structure-activity relationships through performance evaluation and characterization. Among the prepared catalysts, Pt@Mn[δ] exhibited excellent performance and possessed outstanding stability. Crystal structure characterization revealed that the larger specific surface area and lower crystallinity of Pt@Mn[δ] exposed more active sites. XPS analysis indicated the transformation of Mn⁴⁺ to Mn³⁺ on Pt@Mn[δ], leading to the formation of oxygen vacancies. O₂-TPD and H₂-TPR further confirmed the activation of lattice oxygen and the promoted redox cycle of Pt@Mn[δ]. UV-Vis DRS and electrochemical measurements demonstrated that Pt@Mn[δ] exhibited the most pronounced visible-light absorption, the highest photocurrent density, the lowest charge transfer resistance and superior charge carrier mobility. TD-GC-MS analysis indicated that o-xylene underwent alkylation and isomerization, with subsequent oxidation following the Mars-van Krevelen (MvK) mechanism.