Core–shell Pd–Pt nanocubes for the CO oxidation

• Pd–Pt core–shell nanocubes have been prepared and studied for the CO oxidation reaction.
• The maximal reactivity was found for an average value of 0.4 atomic layer of Pt.
• ETEM study during oxidation–reduction cycles shows the formation of high index facets in O2.

Pd–Pt core–shell nanocubes with increasing outer Pt layers have been studied for the CO oxidation reaction by gas phase chromatography. The maximal reactivity of the core–shell nanocubes was found for an average value of 0.4 atomic layer of Pt, with a preferential growth at the corners. High resolution electron microscopy (HRTEM) observations show a rough Pt layer, epitaxially crystallized on the Pd surfaces. In situ observations of the Pd and Pt@Pd nanocubes by Environmental Transmission Electron Microscopy (ETEM) during oxidation–reduction cycles show the formation of high index facets during the adsorption of O2.Similar behavior of the reactivity was reported in the literature for electrocatalytic reactions and interpreted in terms of decrease in the adsorption energy of the rate limiting species on the metal surface. This is explained by the compressive strain and the proximity of Pd atoms in the epitaxial Pt layer on Pd cubes, resulting in a change in the electronic structure of the Pt.

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