Assessing the Role of Oxygen Vacancies on N2O Catalytic Decomposition over CaMn1-xFexO3-δ Perovskites

Catalytic decomposition of N2O using redox perovskites can efficiently mitigate industrial emissions of this molecule. Here, we have selected the CaMn1-xFexO3-δ (CMF) oxides as catalysts to explore the role of oxygen vacancies on N2O decomposition, because for these materials the thermodynamics of oxygen non-stoichiometry is known in detail Perovskites with two levels of Fe-doping, CMF73 (30 % at.) and CMF91 (10 % at.), were prepared and extensively characterized. Higher conversion is obtained over CMF73, which also presents good stability. In the presence of N2O, variation of temperature prompts this perovskite to quickly adjust the value of δ by reversible release/uptake of O2. In parallel, surface vacancies can participate in the breaking of the N-O bond, as a part of a regenerative catalytic cycle yielding N2 and O2. A simple kinetic model shows good correlation between the number of oxygen vacancies, estimated by δ, and the catalytic activity, explaining the better performance of CMF73.