Water-gas shift reaction over CuO/CeO2 catalysts: Effect of CeO2 supports previously prepared by precipitation with different precipitants

A series of CeO2 supports were firstly prepared by precipitation method with NH3⋅H2O (NH), (NH4)2CO3 (NC) and K2CO3 (KC) as precipitant, respectively, and then CuO/CeO2 catalysts were fabricated by depositing CuO on the as-obtained CeO2 supports by deposition-precipitation method. The effect of CeO2 supports prepared from different precipitants on the catalytic performance, physical and chemical properties of CuO/CeO2 catalysts was investigated with the aid of XRD, N2-physisorption, N2O chemisorption, FT-IR, TG, H2-TPR, CO2-TPD and cyclic voltammetry (CV) characterizations. The CuO/CeO2 catalysts were examined with respect to their catalytic performance for the water-gas shift reaction, and their catalytic activities and stabilities are ranked as: CuO/CeO2–NH > CuO/CeO2–NC > CuO/CeO2–KC. Correlating to the characteristic results, it is found that the CeO2 support prepared by precipitation with NH3⋅H2O as precipitant (i.e., CeO2–NH-300) has the best thermal stability and least surface “carbonate-like” species, which make the corresponding CuO/CeO2–NH catalyst presents the highest Cu-dispersion, the highest microstrain (i.e., the highest surface energy) of CuO, the strongest reducibility and the weakest basicity. While, the precipitants that contain CO32- (e.g. (NH4)2CO3 and K2CO3) result in more surface “carbonate-like” species of CeO2 supports and CuO/CeO2 catalysts. As a result, CuO/CeO2–NC and CuO/CeO2–KC catalysts present poor catalytic performance.