Catalytic effect of two-phase intergrowth and coexistence CuO–CeO2

Abstract

Intergrowth CuO–CeO₂ oxides were synthesized using an improved amorphous citric precursor (IACP) method. In order to explore the relationship between structure modulation and catalytic performance, samples were characterized using XRD, XPS, SEM, EDX, HRTEM, O₂-TPD, TG-DSC, OSC, H₂-TPR, and in situ DRIFTS measurements. Catalytic activities were then investigated in CO + O₂ and NO + CO model reactions. Results indicate that the CuO–CeO₂ samples form an intergrowth system which is made up of imperfect monoclinic crystal CuO and cubic crystal CeO₂. Strong interactions between CuO and CeO₂ occurred in the intergrowth process, making the Cu species of CuO gradually form Cu⁺ and produce corresponding oxygen vacancies with the increase of CeO₂ content, which results in an imperfect [Cu_1−x²⁺Cu_x⁺][O_1−x/2□_x/2] structure and improvement of the redox ability of CuO. Meanwhile, the CeO₂ retains a few Ce³⁺ and corresponding oxygen vacancies. As a result, the OSC and the catalytic performance of the samples are greatly enhanced. These results are partly due to the intergrowth and coexistence effects of CuO–CeO₂.