Effects of a Pd/Pt bimetal supported by a γ-Al₂O₃ surface on methane activation

The catalytic removal of methane (CH₄) in exhaust emissions of natural gas-fueled vehicles is still a major challenge for automotive manufacturers because of the high CH₃-H bond energy and high concentrations of water (H₂O). Density functional theory (DFT) calculations were employed to investigate the adsorption of CH₄ and H₂O, as well as the activation of CH₄, on the surface of a Pd-Pt bimetal supported by γ-Al₂O₃. These are significant factors for catalytic combustion. Pt addition weakened the bonding of the intermediates and increased the availability of electrons on the surface. Besides this, the γ-Al₂O₃ surface and Pt were both beneficial for preventing the aggregation of clusters. CH₄ and H₂O adsorption, as well as the detailed mechanism of CH₄ activation on the Pd-Pt/γ-Al₂O₃ surfaces were simulated. The results showed that a Pt/Pd ratio of three resulted in the best catalytic activity among the different ratios examined in the presence of H₂O.