The Promotional Effect of Copper in Catalytic Oxidation by Cu-Doped α-MnO2 Nanorods

α-MnO2 has broad applications in catalytic oxidation. Its catalytic performance may be further improved by doping α-MnO2 with a metal ion, such as the Cu ion, but the reasons for the promoting effect are still not clear. Herein, we investigate the promotional effect of Cu in catalytic CO oxidation by doping isolated Cu ions into the framework of α-MnO2 nanorods. Relevant characterization results confirmed that the single Cu ions were doped in the framework of α-MnO2, concomitant with the generation of more Mn3+ ions and defect oxygen species on catalyst surface. These physicochemical changes may lead to higher catalytic activity in CO oxidation. At 50 °C, the doped Cu ions resulted in a ∼8-fold increase in the CO oxidation reaction rate. The electronic interactions between the doped Cu ions and the Mn ions account for the promotional effect, thus the oxidation–reduction cycle involving the oxidation of CO and the reduction of O2 was accelerated. This work may provide a reasonable strategy to investigate the improved performances of other metal mixed catalysts.