Stabilization of a Carbon Support by Surface Oxygen with Respect to Nitrogen Dioxide in the Pd/HOPG Model System

In this work, X-ray photoelectron spectroscopy (XPS) was used to study the effect of preliminary oxidative treatment of a carbon support surface on the results of NO 2 interaction with model systems prepared by palladium deposition onto highly oriented pyrolytic graphite (HOPG). It was found that, in Pd/HOPG samples with the atomic ratios [O]/[C] ≤ 0.0035, the carbon support was oxidized with the destruction of its structure to a depth of 10–15 graphene layers. In this case, the palladium particles remained in a metallic state, and they penetrated into the near-surface layer of the support due to the deep oxidation of adjacent carbon atoms. At the atomic ratio [O]/[C] ≈ 0.01–0.02, the result of the interaction changed dramatically. In this case, the support remained stable, and the palladium particles were oxidized to form an oxide. This finding explained the high stability of supported palladium catalysts prepared on Sibunit carbon supports in oxidative catalysis reactions.