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A comprehensive density functional theory calculation was employed to investigate the possible reaction pathways and mechanisms of methane complete oxidation (CH4 + 2O2 → CO2 + 2H2O) on different manganese oxides including α-MnO2(100) and β-MnO2(111) surfaces.According to a coupling of the Mars-van Krevelen and Langmuir-Hinshelwood mechanism,the activation energy barrier and the reaction energy of each elementary surface reaction were determined.Our calculated results show that the detailed processes for methane oxidation on two surfaces are different due to the differences in the surface structure.The breaking of the last C-H bond of CH4 molecule is the rate-determining step with an activation barrier of 0.85 eV for α-MnO2(100) surface.By contrast,the overall reaction rate on β-MnO2(111) surface is limited by the dissociation of the second O2 molecule adsorbed on the vacancy site,and re-oxidation of the reduced β-MnO2(111) surface by the gaseous oxygen requires a much higher energy barrier of 1.44 eV.As a result,the α-MnO2(100) exhibits superior activity and durability in the methane oxidation reaction than β-MnO2(111) surface.The present study provides insight into understanding the structure-catalytic activity relationship of the catalysts based on manganese oxides towards the methane oxidation reaction.