Enhanced toluene catalytic oxidation over Ag-Cu co-modified Mn2O3: the crucial roles of surface structure reconstruction process.

This study confirms that Ag-Cu bimetallic modification effectively reconstructs the surface microenvironment of Mn2O3 and significantly enhances its catalytic performance for toluene oxidation. Ag single modified and Ag-Cu bimetallic modified Mn2O3 catalysts were prepared via a hydrothermal-calcination method. It is demonstrated that the synergistic effect between Ag and Cu promotes the partial oxidation of surface Mn3+ to Mn4+, forming a trace MnO2 thin layer and constructing a heterogeneous valence distribution of "surface Mn4+/bulk Mn3+". Systematic characterizations reveal that the Ag-Cu synergy not only enriches bulk Mn3+ active species and generates abundant oxygen vacancies but also establishes dual acid sites comprising weak Lewis and strong Brønsted acids. Furthermore, the cooperation between the MnO2 thin layer and the Mn2O3 bulk phase facilitates the Mn3+/Mn4+ redox cycle, enhances lattice oxygen mobility, and accelerates the oxidation pathway. In-situ DRIFTS studies indicate that, driven by the Ag-Cu synergy and the MnO2-induced valence cycle, toluene oxidation over the 3Ag3Cu-Mn catalyst follows the conversion path of toluene → benzyl alcohol → benzaldehyde → benzoate → CO2/H2O, thereby eliminating the accumulation of refractory intermediates such as maleic anhydride.