Interfacial synergy in setaria viridi-like Mn2O3@MnO2 heterojunctions with switchable nanotube/nanosheet morphologies for HCHO catalytic oxidation

A series of setaria viridis-like Mn 2 O 3 @MnO 2 - T ( T = 3, 6, 9, 12 and 15 h) heterojunctions with switchable nanotube/nanosheet morphologies were synthesized via a controllable redox process. This involved precisely regulating the duration of acidic KMnO 4 treatment to induce in situ MnO 2 growth on rod-like Mn 2 O 3 substrates. Among these, Mn 2 O 3 @MnO 2 -12 exhibited the highest catalytic activity and outstanding stability, achieving 100 % conversion of 150 ppm HCHO at 50 °C under conditions of 30 % relative humidity and 36,000 mL g cat −1 h −1 . The strong electronic coupling at the interface between the Mn 2 O 3 (211) and MnO 2 (110) planes lowered the energy barrier for HCHO oxidation. Lattice mismatch at this interface likely induced oxygen vacancies, critical for activating O 2 into reactive oxygen species. Correspondingly, abundant surface active oxygen was observed in Mn 2 O 3 @MnO 2 -12, which contributed to the formation of dioxymethylene and formate intermediates, as monitored by in situ DRIFTS. Furthermore, greater charge enrichment on Mn combined with a lower work function ( W f ) indicated enhanced electron transfer to reactants and intermediates, establishing a favorable catalytic environment. This study provides a viable strategy for designing cost-effective, highly efficient transition metal oxide catalysts suitable for low-temperature HCHO oxidation.