A structural analysis of the Ru—RuOx/TiO2 catalyst has been carried out. This catalyst is active for CO2 methanation at low temperatures. The preparation conditions are critical in generating the selective dispersion of the metallic particles on rutile crystallites in TiO2-P25. This distribution is limited to the most active samples (CH4 rate = 70 µl/h). On reducing the catalyst at 500°C, in 1 : 1 Ar + H2 for 1 h, Ru metal particles of not, vert, similar 5 nm have been obtained. These particles have a perfect bulk Ru hexagonal packing and clean surfaces.