The role of Gadolinia Doped Ceria support on the promotion of CO2 methanation over Ni and NiFe catalysts

In the present work, CO2 methanation was investigated over Ni, Fe, Ni3Fe1, Ni1Fe1 and Ni1Fe3 catalysts supported on Gadolinia Doped Ceria (GDC) in the temperature range 200-400 °C. Both CO2 and H2 conversion decreased in the order Ni/GDC > Ni3Fe1/GDC > Ni1Fe1/GDC > Ni1Fe3/GDC. No catalytic activity was displayed by Fe/GDC. Maximum CO2 conversion (>90%) was observed at 400 °C, with almost 100% selectivity to CH4. The catalysts were characterized by X Ray Diffraction (XRD), N2 adsorption/desorption, H2 - Temperature Programmed Reduction (H2-TPR), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and CO2 Temperature Programmed Desorption (CO2-TPD). The superior activity of monometallic Ni/GDC with respect to bimetallic NiFe/GDC catalysts was ascribed to the presence of surface oxygen vacancies induced by the GDC support, an enhanced basicity of the Ni-rich samples, as well as to the ability of the Ni-GDC to interact with CO2, as suggested by XPS data.