Double perovskite oxides A2FeMoO6−δ (A=Ca, Sr and Ba) as catalysts for methane combustion

• Published in: Applied catalysis. B, Environmental Environmental, 2004-10, Vol.53 (1), p.37-45
• Main Authors: Falcón, H, Barbero, J.A, Araujo, G, Casais, M.T, Martı́nez-Lope, M.J, Alonso, J.A, Fierro, J.L.G
• Format: Article
• Language: English
• Subjects: A2FeMoO6−δ; Catalytic combustion; Perovskite; Vacancies
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2004.05.004

Double perovskites of composition A2FeMoO6−δ (A, alkali earths) have been prepared by soft-chemistry procedures, followed by annealing under reducing conditions (H2/N2 flow). These materials are half metallic ferromagnets, well known for their colossal magnetoresistance properties. The samples have been characterized by X-ray diffraction; temperature-programmed oxidation, specific surface measurements and XPS. The Sr compound, of tetragonal symmetry, exhibits a significant amount of oxygen vacancies, as assessed by TPO. The materials have been tested as catalysts for methane oxidation. At moderate temperatures, a significantly higher catalytic activity is observed for the Sr double perovskite, for which a 80% of conversion is reached at 800K; by contrast the Ca and Ba materials are found to display much poorer characteristics, hardly achieving 50% of conversion rate at 1000K. The much superior characteristics of Sr2FeMoO6−δ are believed to be related to the presence of oxygen vacancies in the crystal structure.