Aspects of Fe-Incorporation into CaTiO₃-SrTiO₃ Perovskites and Their Catalytic Application for Ammonia SCO/SCR

Perovskite materials in the CaTiO₃-SrTiO₃ system doped with different amounts of iron (1, 2 and 5 mol.%) and various Ca/Sr ratios were prepared by the modified citrate method. Additionally, the materials with 0.05 deficiency in strontium/calcium sublattice and 5 mol.% of Fe were also synthesised. The materials were subjected to structural (XRD, XANES) and microstructural (SEM) characterisation, as well as the analysis of susceptibility to reduction/oxidation processes. The structural analysis indicates a lack of iron-containing phases; thus, an incorporation of Fe into the perovskite structure was postulated. Additionally, the oxidation state of iron in the perovskite structure changes with the dopant amount. The temperature-programmed reduction measurements showed partial reversibility of the reduction processes. For the materials with the highest iron amount, the catalytic tests in NH₃-SCO and NH₃-SCR reactions were carried out. The materials showed high catalytic activity and high selectivity to N₂ in the NH₃-SCR process; however, they were inactive in NH₃-SCO.