Promotion effect of residual K on the decomposition of N2O over cobalt–cerium mixed oxide catalyst

A series of cobalt–cerium mixed oxide catalysts (Co3O4–CeO2) with a Ce/Co molar ratio of 0.05 were prepared by co-precipitation (with K2CO3 and KOH as the respective precipitant), impregnation, citrate, and direct evaporation methods and then tested for the catalytic decomposition of N2O. XRD, BET, XPS, O2-TPD and H2-TPR methods were used to characterize the catalysts. Catalysts with a trace amount of residual K exhibited higher catalytic activities than those without. The presence of appropriate amount of K in Co3O4–CeO2 may improve the redox property of Co3O4, which is important for the decomposition of N2O. When the amount of K was constant, the surface area became the most important factor for the reaction. The co-precipitation-prepared catalyst with K2CO3 as precipitant exhibited the best catalytic performance because of the presence of ca. 2 mol% residual K and the high surface area. We also discussed the rate-determining step of the N2O decomposition reaction over these Co3O4–CeO2 catalysts.