SrSnO3:Ni Perovskites: Synthesis, Structure and Catalytic Properties for NO Reduction with CO in the Presence of O2

Catalytic systems by which nitrogen oxides (NOx) in automotive emissions may be reduced to nitrogen are highly efficient when used with rich-burn engines, but are far less effective when excess oxygen is present in the exhaust gases produced, for example, by energy-efficient lean-burn engines. Herein, we describe the synthesis of Sr1-xNixSnO3 (x = 0 to 0.2) perovskite-type by a modified Pechini method and their capacities to catalyze the reduction of nitric oxide (NO) with carbon monoxide (CO) in the presence carbon dioxide, water vapor and excess oxygen. The materials showed a selectivity of NO reduction rather CO. The highest conversions of NO into nitrogen were observed at temperatures within the range 450–500 °C, with a maximum conversion of 40% attained for the 10% of nickel containing sample. Spectroscopic analyses of the perovskites prior to and following the reduction process revealed changes in the local SnO6 symmetry of the structure followed the formation of strontium carbonate during catalysis. The results also indicate that AO12 and SnO6 sites are both active in the catalytic process, besides being favored by the presence of oxygen vacancies, which adsorbs and activates NO molecules and increase the mobility of lattice oxygen.