Effect of Pd deposition procedure on activity of Pd/Ce0.5Sn0.5O2 catalysts for low-temperature CO oxidation

• Pd/Ce0.5Sn0.5O2 catalysts for low temperature CO oxidation were prepared.
• Solution combustion of all precursors leads to bulk Pd2 + ions distribution.
• Impregnation of Ce0.5Sn0.5O2 by Pd leads to surface localized Pd2 + ions.
• Impregnation method allows obtaining high activity of catalyst at low Pd content.

Two methods for the preparation of Pd/Ce0.5Sn0.5O2 catalysts have been used: solution combustion (SC) of Pd, Ce and Sn precursor mixtures, and incipient wetness impregnation by [Pd(NO3)2(H2O)2] solution of Ce0.5Sn0.5O2 – δ support, obtained by the SC technique (SC + IWI). The formation of metallic palladium was observed in addition to ionic palladium in a Pdx(Ce0.5Sn0.5)1 – xO2 – x – δ solid solution due to high-temperature Pd precursor decomposition during the SC process. IWI of Ce0.5Sn0.5O2 – δ support has been demonstrated to lead to a uniform solid solution of Pd2 + ions in the Ce0.5Sn0.5O2 – δ matrix at 1% Pd content that resulted in high catalyst activity towards CO oxidation. The increase of Pd content to 5% showed no influence on catalytic activity. This observation is explained by the formation of low active PdO species when Pd content is more than 1%. The proposed SC + IWI method allows obtaining highly active Pd/Ce0.5Sn0.5O2 catalysts with low palladium content.

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