CO₂ methanation on Ru-doped ceria

We study the methanation of CO₂ catalyzed by ceria doped with Ni, Co, Pd, or Ru. Ce₀.₉₆Ru₀.₀₄O₂ and Ce₀.₉₅Ru₀.₀₅O₂ perform best, converting 55% of CO₂ with a 99% selectivity for methane, at a temperature of 450°C. This is comparable to the best catalysts found previously for this reaction. Ce₀.₉₅Ru₀.₀₅O₂ was characterized by XRD, electron microscopy, BET, XPS, IR spectroscopy, and temperature-programmed reaction with Ar, H₂, CO, and CO₂+H₂. Steady-state methanation was studied at several temperatures between 100 and 500°C. We find that the methanation reaction takes place on the reduced Ce₀.₉₅Ru₀.₀₅O₂, and the role of the dopant is to make the reduction possible at lower temperature than on pure ceria. We discuss the potential for local and global effects of the dopant on catalytic chemistry.