Redox-driven surface generation of highly active Pd/PdO interface boosting low-temperature methane combustion

The supported Pd catalyst has been a benchmark for methane elimination. However, the active structures have been long under debate. Here, by the aberration-corrected high angle annular dark field scanning transmission electron microscopy, operando X-ray absorption spectroscopy and quasi in situ X-ray photoelectron spectroscopy, we revealed the two-dimensional metallic Pd bumps on the PdO surface (litchi-like structure) generated by the redox atmosphere under the lean condition as a highly active structure of the Pd/Al₂O₃ catalyst. The substantially increased Pd/PdO interfaces boost the methane combustion activity higher than the similar catalysts reported previously, and remarkably enhance the reaction rate by 15.5 and 10.7 times that of pure PdO or metallic Pd counterpart under lean condition at 300 °C, respectively. Density-functional theory calculations confirm the synergistic C–C bond activation of methane on the Pd/PdO interfaces. Our work provides new insight into the traditional understanding of the chemical state and particle size effects of the industrial Pd catalysts for methane oxidation.