Photothermal Catalysis Driven by Defect-Engineered Mn:V₂O₅ for Efficient Rhodamine B Degradation

Abstract

A series of Mn-modified V2O5 catalysts was synthesized via a facile sol-gel method, and their photothermal catalytic performance was systematically investigated for the degradation of Rhodamine B (RhB). The results demonstrate that the optimal sample, Mn0.03-V2O5, shows broadband light absorption performance and efficient separation of photogenerated charge carriers, achieving complete degradation of RhB within 40 min, with an apparent rate constant (k) of 0.12229 min-1. Band structure analysis indicated that the conduction band position of the sample Mn0.03-V2O5 is more positive than -0.33 eV vs. NHE, which is thermodynamically insufficient for the direct reduction of O2 to ·O2-. Furthermore, free radical trapping experiments verified that ·O2- serves as the primary active species responsible for RhB degradation. It is found that defect-induced localized states formed by low-valence V species and oxygen vacancies enable photogenerated electrons to overcome energy barriers and efficiently produce ·O2-, which acts as the dominant reactive species in RhB degradation. Meanwhile, the photothermal effect of Mn0.03-V2O5 promotes molecular diffusion and reduces the energy barrier of O2 to ·O2-. This study provides valuable insights for the design of efficient photothermal catalysts via defect-mediated band structure and photothermal effect in metal oxides.