Effect of precipitants on Ni-CeO2 catalysts prepared by a co-precipitation method for the reverse water-gas shift reaction

A series of Ni-CeO2 catalysts were prepared by co-precipitation method with Na2CO3, NaOH, and mixed precipitant (Na2CO3:NaOH; 1:1 ratio) as precipitant, respectively. The effect of the precipitants on the catalytic performance, physical and chemical properties of Ni-CeO2 catalysts was investigated with the aid of X-ray diffraction (XRD), Brumauer-Emmett-Teller method (BET), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetry (TG), and H2-TPR characterizations. The Ni-CeO2 catalysts were examined with respect to their catalytic performance for the reverse water-gas shift reaction, and their catalytic activities were ranked as: Ni-CeO2-CP (Na2CO3:NaOH=1:1)>Ni-CeO2-CP(Na2CO3)>Ni-CeO2-CP(NaOH). Correlating to the characteristic results, it was found that the catalyst prepared by co-precipitation with mixed precipitant (Na2CO3:NaOH; 1:1 ratio) as precipitant had the most amount of oxygen vacancies accompanied with highly dispersed Ni particles, which made the corresponding Ni-CeO2-CP(Na2CO3:NaOH=1:1) catalyst exhibit the highest catalytic activity. While the precipitant of Na2CO3 or NaOH resulted in less or no oxygen vacancies in Ni-CeO2 catalysts. As a result, Ni-CeO2-CP(Na2CO3) and Ni-CeO2-CP(NaOH) catalysts presented poor catalytic performance.