Reaction mechanism insights into CH4 catalytic oxidation on Pt13 cluster: A DFT study

Catalytic combustion of methane is an efficient and environment-friendly combustion method that can effectively reduce air pollutant emissions. To uncover the reaction mechanism of methane catalytic oxidation, density functional theory (DFT) calculation was performed on Pt-13 cluster with the B3LYP method. Combining thermodynamic parameters with dynamics parameters, the optimal paths for CH4 activation and CO2 formation are CH4* -> CH3* -> CH2* -> CH* -> CHOH* -> COH* and CH* -> CHOH* -> CHO* -> CO* -> COOH* -> CO2*, respectively. In addition, the presence of H2O in the reactants changed the reaction path from CH4* -> CH3* -> CH2* -> CH*+O* -> CHO* -> CO*+O* -> CO2* to CH4* -> CH3* -> CH2* -> CH*+OH* -> CHOH* -> CHO* -> CO*+OH* -> COOH* -> CO2*, thus leading to the rate-determine step (RDS) changes from CO*+O* -> CO2* to CH3* -> CH2*. The energy barrier of the RDS with H2O is 1.19 eV, much lower than that of the RDS without H2O (1.31 eV), indicating that the presence of H2O in the reactants is beneficial to the catalytic oxidation of CH4.