Insight into the Crystal Structures and Surface Property of Manganese Oxide on CO Catalytic Oxidation Performance.

α-MnO2 nanorods and flower-like γ-MnO2 microspheres were synthesized by facile and mild methods to illustrate the effect of crystal structures and surface features on catalytic performance with the help of carbon monoxide (CO) oxidation. It is revealed that the flower-like γ-MnO2 microspheres possess better catalytic oxidation performance (CO complete conversion temperature at 120 °C and long-time stability for 50 h) than α-MnO2 nanorods, which can be attributed to the obvious differences in the chemical bonds and linking modes of [MnO6] octahedra due to the different crystal structures. γ-MnO2 possesses lower Mn-O bond strength that enables γ-MnO2 to present a large amount of surface lattice oxygen and superior oxygen mobility. The disordered random intergrowth tunnel structure can adsorb effectively CO molecules, resulting in excellent catalytic performance for CO catalytic oxidation. In addition, the MnO2 catalyst probably occurred via a Mars-van Krevelen mechanism for CO oxidation. This work provides an insight into the effect of crystal structures and surface property of manganese oxide on catalytic oxidation performance, which presents help for the future design of promising catalysts with excellent catalytic performance.