Absorption/desorption of NOx process on perovskites: Nature and stability of the species formed on BaSnO3

The formation of various species during the adsorption of NOx, issuing from a synthetic, Lean–Burn exhaust gas upon BaSnO3 was studied using FTIR and TGA. An exposure to CO2 does not lead to the formation of carbonates yet contact with NO2 does produce nitrates, which accounts for the high NOx capacity of such solids. N-bounded nitrate and bulk nitrate species were identified. These nitrates decompose upon heating with no loss of the perovskite structure. The process of absorption/desorption is reversible, repeatable and can be explained by the following equations: Absorption phase: BaSnO3+3NO2↔Ba(NO3)2+SnO2+NO, Desorption phase: Ba(NO3)2+SnO2↔BaSnO3+2NO2+12O2.