Catalytic decomposition of N2O over Y-Co3O4 composite oxides prepared by one-step hydrothermal method

Abstract Y-Co 3 O 4 catalysts with Y/Co molar ratio of 0.03 were prepared by several methods, such as one-step hydrothermal, two-step hydrothermal, and impregnation methods, to catalyze the decomposition of N 2 O. Among these catalysts, the one prepared by one-step hydrothermal method exhibited the highest activity, and then the Y-Co 3 O 4 catalysts with various molar ratios of Y/Co were synthesized by one-step hydrothermal method. Subsequently, the optimized 0.03Y-Co 3 O 4 was impregnated by K 2 CO 3 solution to prepare K-modified catalyst and named as 0.02K/0.03Y-Co 3 O 4 . These catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption, hydrogen temperature-programmed reduction (H 2 -TPR), oxygen temperature-programmed desorption (O 2 -TPD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. The results show that both Co 3 O 4 and Y-Co 3 O 4 exhibit spinel structure, however Y-doped Co 3 O 4 catalysts are more active than bare Co 3 O 4 . After further modified by potassium, the 0.02K/0.03Y-Co 3 O 4 reveals higher activity due to the more active sites (Co 2+ ) and easier desorption of surface oxygen species than un-modified 0.03Y-Co 3 O 4 . In detail, the temperatures of N 2 O full conversion over 0.02K/0.03Y-Co 3 O 4 catalyst are 325, 350, 375°C, under the reaction atmospheres of 1%N 2 O+Ar, 1%N 2 O+2%O 2 +Ar, 1%N 2 O+2%O 2 +8.2%H 2 O+Ar, respectively. In addition, over 90% conversion of N 2 O can be maintained at 350°C after continuous reaction for 50 h in the co-presence of oxygen and steam on K-modified Y-Co 3 O 4 catalyst. There is a dynamic compensation effect between apparent activation energy ( E a ) and pre-exponential factor ( A ) in N 2 O decomposition over Y-Co 3 O 4 and K-modified catalysts.