The CuO/Ce0.75Zr0.25O2-? and Ce0.75Zr0.25O? catalysts were prepared by the sol-gel method, and Cu0.07Ce0.75Zr0.25O2-? was obtained by treating CuO/Ce0.75Zr0.25O2-? with nitric acid to remove the well-dispersed CuO on the surface. Various characterizations were used to reveal the different active sites, such as surface-dispersed CuO and Cu-Ce-Zr-O? solid solutions in CuO/Ce0.75Zr0.25O2-?, Cu-Ce-Zr-O? solid solutions in Cu0.07Ce0.75Zr0.25O2-? and Ce-Zr-O? solid solutions in Ce0.75Zr0.25O?. The Raman and O2-TPD results showed that the concentration of oxygen vacancies in Cu-Ce-Zr-O? solid solutions was higher than that in Ce-Zr-O? solid solutions. CO oxidation testing suggested that the catalytic activity decreases in the order of CuO/Ce0.75Zr0.25O2-? > Cu0.07Ce0.75Zr0.25O2-? > Ce0.75Zr0.25O?. Combined with the in situ diffuse-reflectance Fourier transform (in situ DRIFT) results, the reaction sensitivity followed the order of CO linear chemisorption onto dispersed CuOx species (M-K mechanism) > carbonate species onto a Cu-Ce-Zr-O? solid solution (L-H mechanism) > carbonate species onto a Ce-Zr-O? solid solution (L-H mechanism). Kinetic studies suggested that the power-law rate expressions and apparent activation energies were r?=?6.02?×?10-7×PCO0.68PO20.03 (53?±?3?kJ/mol) for CuO/Ce0.75Zr0.25O2-?, r?=?5.86?×?10-7×PCO0.8PO20.07 (105?±?5?kJ/mol) for Cu0.07Ce0.75Zr0.25O2-? and r?=?5.7?×?10-7×PCO0.75PO20.12 (115?±?6?kJ/mol) for Ce0.75Zr0.25O?. The M-K mechanism should be the crucial reaction pathway over CuO/Ce0.75Zr0.25O2-? in CO interfacial reactions, although the L-H mechanism cannot be ignored, and the L-H mechanism mainly occurred over the Cu0.07Ce0.75Zr0.25O2-? and Ce0.75Zr0.25O? catalysts, where the contribution from the M-K mechanism was negligible due to the absence of surface CuOx species.

» Author: Running Kang, Xiaolin Wei, Feng Bin, Zibing Wang, Qinglan Hao, Baojuan Dou

» Reference: 10.1016/j.apcata.2018.07.026

» Publication Date: 23/07/2018

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