Graphical abstract
Highlights-Graphene-supported Ni and Ni-CeO 2 catalysts have been studied.-Metal dispersion depends on the presence of ceria and on the precipitating agent, NaOH or urea.-The graphene support strongly interacts with the ceria promoter.-The presence of sodium increases the catalytic activity, mainly in the presence of ceria.
AbstractThe low temperature water-gas shift (WGS) reaction has been studied over NiCeO 2 /Graphene and Ni/Graphene. The catalysts were prepared with 5 wt% Ni and 20 wt% CeO 2 loadings, by deposition-precipitation employing sodium hydroxide and urea as precipitating agents. The materials were characterized by TEM, powder X-ray diffraction, Raman spectroscopy, H 2 -temperature-programmed reduction and X-ray photoelectron spectroscopy (XPS). The characterization and the reaction results indicated that the interaction between the active species and the support is higher than with activated carbon, and this hinders the reducibility of ceria and thus the catalytic performance. On the other hand, the presence of residual sodium in samples prepared by precipitation with NaOH facilitated the reduction of ceria. The catalytic activity was highly improved in the presence of sodium, what can be explained on the basis of an associative reaction mechanism which is favored over Ni-O-Na entities.