Elucidation of the Active Phase in Pd‐Based Catalysts Supporting on Octahedral CeO2 for Low‐Temperature Methane Oxidation

Abstract

AbstractPd catalysts supported on CeO2 (Pd/CeO2) are highly active towards lean methane combustion, and the catalytic behavior is substantially affected by the chemical property of surface palladium species. In this work, various Pd catalysts supported on octahedral‐CeO2 (Pd/O‐CeO2) were successfully prepared by redox interation‐engaged strategy. The oxidation state of palladium species was controlled by varying the calcination condition. X‐ray absorption characterization coupled with light‐off curves confirmed that the catalytic activity of relevant catalysts was closely related with the proportion of the metallic Pd and PdO species. Within limits, increasing Pd0/PdO ratio can bring superior catalytic behavior and the approximately equal ratio of interfacial hybrid Pd0/PdO phase exhibits the optimal catalytic activity. Importantly, in situ DRIFTS results demonstrated that the hybrid Pd0/PdO phase was recognized as the active site pair for lean methane oxidation, which is attributed to the fact that the metallic Pd0 species can adsorb and dissociate methane molecules and then the resulting intermediate species further react with the active O* of PdO, which thereby promotes CH4 activation.