Metal–Support Interactions within a Dual-Site Pd/YMn2O5 Catalyst during CH4 Combustion

Catalytic combustion is a promising technology for removing unburnt CH4 from natural gas vehicle exhaust gas under lean-burn conditions. Supported Pd catalysts are widely applied and studied for use in CH4 oxidation at <500–550 °C, with their activities significantly affected by the interactions between Pd and the support, depending on the dispersion, Pd valence state, and properties of the support. However, whether metal–support interactions are favorable in catalytic CH4 oxidation is unclear. We therefore used YMn2O5 as a catalytically active support to prepare a dual-site catalyst, Pd/YMn2O5, which shows high CH4 catalytic activities in dry and wet atmospheres. Experimental and density functional theory studies reveal that the CH4 adsorption and lattice oxygen activity of the support are significantly enhanced due to the interactions between PdOx and YMn2O5. In situ X-ray photoelectron spectroscopy shows that Pdx+ (x = 2 and 4) and Mnx+ (x = 3 and 4) species undergo changes during CH4 oxidation. The PdOx sites are the main active sites, as the CH4 activation barrier is much lower than those at other sites. YMn2O5 and PdOx participate in CH4 activation and oxidation via active oxygen transfer.