A comparison of NiO–CuO–CeO2 composite catalysts prepared via different methods for CO oxidation

Abstract

Several NiO–CuO–CeO2 catalysts were prepared via different methods and characterized by different techniques. Structure-activity relationships of the catalysts were demonstrated, and the effect of preparation methods on CO oxidation behaviors was illustrated. Catalytic results evidenced that the NiCuCe-CP and NiCuCe-SG catalysts prepared by co-precipitation and sol-gel methods exhibited better CO oxidation activities and kinetic performance, as evidenced by their lower T50 values (102 ​°C and 100 ​°C) and apparent activation energies (48.80 and 59.28 ​kJ/mol) as well as higher reaction rates (3.84 and 3.45 ​μmol/g/s). The XRD and HRTEM results suggested that the active species showed uniform dispersion with minimum crystallite size in the desired catalysts. The XRD, XPS, H2-TPR and Raman analysis suggested the formation of Ce1-xCuxO2-δ and Ce1-xNixO2-δ solid solutions, indicating that the co-precipitation and sol-gel methods reinforced the interactions amongst the ternary metal oxides. This would afford the catalysts more oxygen vacancies for boosted CO oxidation activity. The mechanism was then proposed with the dual synergetic effects in solid solutions for facilitated oxygen mobility and the amorphous active metal oxides for promoted CO chemisorption. The desired NiCuCe-CP and NiCuCe-SG catalysts show potential application for CO abatement in closed-loop air revitalization.