The reduction of CO2 by H2 is an important step within the power-to-gas (P2G) concept , which is crucial for the chemical storage of renewable energy with an ultimate goal to compensate for the fluctuating production of wind and solar power . Ru based catalysts have attracted particular interest because of their high catalytic activity already at lower temperature (≤ 190 °C) . Among the different support materials, Al2O3 appeared to be less attractive because of the lower catalytic activity of Ru/Al2O3 catalysts compared to Ru catalysts supported on other materials such as CeO2, MgO, SiO2, and TiO2 . The interest in the Ru/Al2O3 catalyzed CO2 methanation reaction increased, however, recently, when Chen et al. demonstrated that the activity of this catalyst could be enhanced significantly by a strongly reductive treatment in the reaction gas mixture . The authors explained this by the formation of Lewis basic sites on the support, which could stabilize more active flat Ru nanoparticles (NPs), resulting in strong metal-support interactions (MSIs).