Evaluation of an ε-manganese (IV) oxide/manganese vanadium oxide composite catalyst enriched with oxygen vacancies for enhanced formaldehyde removal

Formaldehyde removal is vital to health, but the construction of high-performance non-precious metal catalysts still faces great challenges, in which increasing oxygen vacancies by dopant modification is an advanced strategy to enhance catalytic activity. In this work, a novel ε-MnO₂/Mn₂V₂O₇ composite catalyst with a synergistic effect was synthesized on the basis of a thermal decomposition strategy. Meanwhile, the precursor for the catalyst was synthesized from the reaction among CO₂-storage material, Mn²⁺, and vanadate without additional template agents and surfactants. Aided by the catalyst, the degradation rate of a 20 mg/L 10 mL formaldehyde (HCHO) solution can reach 72.0% and maintain above 67% after 5 cycles at 30 °C for 1 h. Subsequently, the as-obtained synergistic catalytic mechanism showed that the high-valent V⁵⁺ may partially replace Mn⁴⁺ in the MnO₂ framework, promoting the formation of enriched oxygen vacancies (V⁴⁺-□-Mn³⁺) on the surface of the composite catalyst via the redox coupling of Mn⁴⁺/Mn³⁺ and V⁵⁺/V⁴⁺. This leads to an increase in adsorbed oxygen, significantly improving the degradation performance of HCHO. This work provides a novel and advanced strategy for dopant modification to develop superior non-precious metal catalysts.