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Penta-Coordinated Al3+ Stabilized Active Pd Structures on Al2O3 Coated Palladium Catalysts for Methane Combustion.

Supported Pd catalysts are active in catalyzing the highly exothermic methane combustion reaction but tend to deactivate due to local hyperthermal environments. Herein we report an effective approach to stabilize Pd/SiO2 catalysts with porous Al2O3 overlayers coated by atomic layer deposition (ALD) method. 27Al magic angle spinning NMR characterization results show that Al2O3 overlayers on Pd particles coated by ALD method have rich penta-coordinated Al3+ sites capable of strongly interacting with adjacent surface PdOx phases on supported Pd particles. Consequently Al2O3-decorated Pd/SiO2 catalysts exhibit active and stable PdOx and Pd-PdOx structures to efficiently catalyze methane combustion between 200 and 850 °C. These results reveal the unique structural characteristic of Al2O3 overlayers on metal surfaces coated by ALD method and provide a practical strategy to explore stable and efficient supported Pd catalysts for methane combustion.