Electron transferring with oxygen defects on Ni-promoted Pd/Al₂O₃ catalysts for low-temperature lean methane...

Methane (CH₄) is the second most consequential greenhouse gas after CO₂, with a substantial global warming potential. The CH₄ catalytic combustion offers an efficient method for the elimination of CH₄. However, improving the catalytic performance of Pd-based materials for low-temperature CH₄ combustion remains a big challenge. In this study, we synthesized an enhanced Pd/5NiAlO_x catalyst that demonstrated superior catalytic activity and improved water resistance compared to the Pd/Al₂O₃ catalyst. Specifically, the T₉₀ was decreased by over 100 °C under both dry and wet conditions. Introducing Ni resulted in an enormously enhanced number of oxygen defects on the obtained 5NiAlO_x support. This defect-rich support facilitates the anchoring of PdO through increased electron transfer, thereby inhibiting the production of high-valence Pd^(2+δ)+ and stimulating the generation of unsaturated Pd sites. Pd⁰ can effectively activate surface oxygen and PdO plays a significant role in activating CH₄, resulting in high activity for Pd/5NiAlO_x. On the other hand, the increased water resistance of Pd/5NiAlO_x was mainly due to the generation of *OOH species and the lower accumulation of surface -OH species during the reaction process.