Atomic Structure of Pd-, Pt-, and PdPt-Based Catalysts of Total Oxidation of Methane: In Situ EXAFS Study

In this study, 3%Pd/Al2O3, 3%Pt/Al2O3 and bimetallic (1%Pd + 2%Pt)/Al2O3 catalysts were examined in the total oxidation of methane in a temperature range of 150-400 degrees C. The evolution of the active component under the reaction conditions was studied by transmission electron microscopy and in situ extended X-ray absorption fine structure (EXAFS) spectroscopy. It was found that the platinum and bimetallic palladium-platinum catalysts are more stable against sintering than the palladium catalysts. For all the catalysts, the active component forms a core-shell structure in which the metallic core is covered by an oxide shell. The core-shell structure for the platinum and bimetallic palladium-platinum catalysts is stable in the temperature range of 150-400 degrees C. However, in the case of the palladium catalysts the metallic core undergoes the reversible oxidation at temperatures above 300 degrees C and reduced to the metallic state with the decrease in the reaction temperature. The scheme of the active component evolution during the oxidation of methane is proposed and discussed.

Automated summary

The study reveals that platinum and bimetallic palladium-platinum catalysts are more stable in the total oxidation of methane compared to palladium catalysts. All catalysts exhibit a core-shell structure, where the metallic core is covered by an oxide shell. The evolution of the active component during the methane oxidation process is proposed and discussed.