Effect of alkaline earth metal doping on the catalytic performance of cobalt-based spinel composite metal oxides in N₂O decomposition

A series of cobalt-based spinel composite metal oxides doped with alkaline earth metals, viz., M_xCo_3-xO₄ (M=Mg, Ca, Sr and Ba; x=0, 0.1, 0.3, 0.5, 0.7 and 0.9), were prepared by the coprecipitation method and characterized by XRD, SEM, nitrogen sorption, H₂-TPR, O₂-TPD-MS and XPS; the effect of alkaline earth metal doping on the catalytic performance of M_xCo_3-xO₄ composites in N₂O decomposition was investigated in a fixed bed micro-reactor. The results showed that after doping with the alkaline earth metals, the particle size of M_xCo_3-xO₄ catalysts is decreased, accompanying with an increase in the specific surface area and the amount of surface adsorbed oxygen and Co²⁺ species. Meanwhile, the redox performance and catalytic activity of M_xCo_3-xO₄ in N₂O decomposition are also greatly enhanced. Under the conditions of 0.68% N₂O, 3% O₂ and Ar as balance gas, the Sr_0.7Co_2.3O₄ catalyst doped with Sr (x=0.7) exhibits highest activity in N₂O decomposition; the reaction temperatures where the N₂O conversion reaches 10% and 95% are as low as 312 and 451℃, respectively.