Photothermal catalysis driven by defect-engineered Mn-doped V₂O₅ for efficient rhodamine B degradation

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, Mn_0.03-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 Mn_0.03-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 Mn_0.03-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.