Intergrowth And Coexistence Effect Of CeO₂-CuO

The intergrowth and coexistence powders of nCeO2·(1-n)CuO (n=0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0) were prepared by an improved amorphous citric precursor (IACP) method, and characterized by XRD, XPS, SEM and H2-TPR measurements. The catalytic activities of the catalysts were investigated by CO+O2 (T50?T90) and NO+CO model reaction in the continuous fixed bed microreactor.The XRD results indicate that the nCeO2·(1-n)CuO sample is consisted of monoclinic crystal CuO phase and cubic crystal CeO2 phase. Because the CeO2 phase and CuO phase closely contact, interact, modify their microstructure with each other, making that the cell volume of CuO phase increases with the increase of CeO2 content, however, the cell volume of CeO2 phase has relatively little change with CuO content. The XPS demonstrate that the component of CuO is consisted of Cu2+ and Cu+ species for nCeO2·(1-n)CuO samples, and corresponding oxygen vacancy is increased with the increase of CeO2 content, which results in the imperfect structure of [Cu2+1-xCu+x][O1-x/2?x/2](x=0-1)and the x value increases with the increase of CeO2. The increase of the cell volume of CuO phase and the production of Cu+ species and oxygen vacancy improve the catalytic activity of CuO. Meanwhile, CeO2 still remains a few Ce3+ and corresponding oxygen vacancy. The SEM patterns show that the nCeO2·(1-n)CuO samples were small particles dispersed uniformly, promoting the synergistic interaction. H2-TPR tests show that, the H2-TPR temperature of CuO is obviously lower than that of pure CuO for the nCeO2·(1-n)CuO samples and it shifts toward lower temperature with the increase of CeO2 content.Experiments of CO oxidation show that the main role of redox ability is the CuO phase for the nCeO2·(1-n)CuO samples and the intergrowth and coexistence effect were increased with the increase of CeO2 content. When it is 0.8CeO2·0.2CuO, the T50 and T90 of CO oxidation reach lowest 87? and 104?, respectively. Experimental results of catalytic reduction of NO display that, the amounts of Cu+ and oxygen vacancies were increased with the increase of CeO2 in the nCeO2·(1-n)CuO sample and promotes the catalytic reduction of NO by CO. When it is 0.5CeO2·0.5CuO, the conversion of NO and the selectivity of N2 have reached 100% at 220?.