CuO/CeO is a kind of promising catalysts for the water-gas shift (WGS) reaction. Efforts were put in to improve its performance through modification of CeO support. In this study, portions of CeO prepared by a co-precipitation method were separately annealed at 300 °C in air, under vacuum and with H , and were used as supports for the fabrication of CuO/CeO catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N -physisorption, inductively coupled plasma, Raman spectroscopy, CO temperature-programmed desorption, and H temperature-programmed reduction techniques. The relation between catalytic performances and physicochemical properties of the CuO/CeO catalysts were discussed. Among the three catalysts, the one with CuO supported on H -reduced CeO shows the highest catalytic activity, mainly due to strong CuO-CeO synergetic interaction and high concentration of Frenkel-type oxygen vacancies. The superior catalytic activities can also be attributed to the Cu crystals of small size and the oxygen vacancies in non-stoichiometric CeO .
Hydrotalcite-like compounds (HTlcs) are promising supports or catalyst precursors for heterogeneous catalysts. Herein, MgAl-HTlcs-supported Pd catalyst was fabricated, and two Pd catalysts supported on Mg(OH)2 and Al(OH)3 were prepared for comparison. The presence of hydroxyl groups (OH-) in the support is important for obtaining uniform Pd nanoparticles with small sizes. We found that Pdn+ species are more active than Pd0 in low temperature CO oxidation due to their lower barrier in CO activation. The Pd/MgAl-HT catalyst shows the most stable Pdn+ at a temperature lower than 90 °C, leading to the highest catalytic activity towards CO oxidation. Pdn+ in the Pd/Al(OH)3 catalyst is more stable than that in Pd/Mg(OH)2 at low temperature, which is ascribed to its smaller temperature hysteresis (Thysteresis) between the oxidation and re-reduction cycles. The effect of hydroxyl groups on stabilizing Pd species is related to the stability of Pd catalyst in CO oxidation reaction.
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