Abstract
A redox cycle between Ce4+ and Ce3+ is an elementary step in water gas shift (WGS) mechanism. By facilitating the redox cycle between +4 and +3 of cerium, a formation of oxygen vacancy can be enhanced. It is considered to be a dominating factor in developing the WGS performance and the stability of ceria in this work. We have facilitated the redox cycle in CeO2 to enrich the WGS activity. The WGS reaction was carried out on Ni catalyst supported by Gd-doped ceria (GDC) from Daiichi. Ni and Re were added onto GDC by impregnation method to examine the role of Re addition on surface, structural and reducibility, which affected upon their catalytic activities. Rhenium has an influence on increasing the water gas shift performance of Ni/GDC catalysts because it facilitates the redox process at the surface of ceria, disperses Ni particles and enhances oxygen vacancy formation. The results indicate that the water gas shift activity of 1%Re4%Ni/GDC is higher than that of 5%Ni/GDC. The dispersion of active site on the surface of catalyst results in an increase of CO molecule adsorption and acceleration of the redox cycle between Ce4+ and Ce3+ of ceria support via oxygen vacancy generation. Therefore, using a combination of these two effects can enhance the WGS performance.