Effect of Pd deposition procedure on activity of Pd/Ce_0.5Sn_0.5O₂ catalysts for low-temperature CO oxidation

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 palladiumwas 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.