N2O direct dissociation over MgxCeyCo1−x−yCo2O4 composite spinel metal oxide

Abstract

A series of Mg- and/or Ce-doped Co3O4 (MgxCo1−xCo2O4 CexCo1−xCo2O4, MgxCeyCo1−x−yCo2O4) composite spinel metal-oxide catalyst was prepared by a coprecipitation method and evaluated for N2O direct decomposition. The activity measurement results suggest that Mg0.025Ce0.05Co0.925Co2O4 with a Mg/Ce mole ratio of 0.5 exhibited the highest N2O conversion activity, achieving 100% N2O conversion at T = 250 °C (35 vol % N2O balanced by He, gas hourly space velocity (GHSV) = 30,000 h−1). Characterizations using X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), hydrogen temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) reveal that there were three main reasons for the excellent catalytic behavior of Mg0.025Ce0.05Co0.925Co2O4: (a) Mg and Ce co-doping could reduce the grain size of composite spinel metal oxide, which thereby significantly increased the BET specific surface area of Mg0.025Ce0.05Co0.925Co2O4 (111.2 g·m2 with respect to that of 32.5 g·m−2 for Co3O4); (b) Mg and Ce co-doping could improve the redox ability of Mg0.025Ce0.05Co0.925Co2O4, including reductions of Co3+ → Co2+ and Co2+ → Co0; and (c) Mg and Ce co-doping not only could improve the migration ability of surface atomic O, but also could increase the concentrations of surface atomic O.