Methane synthesis from H2 and CO2, also referred to as CO2 methanation, is a well-established process on Earth . The main reaction is depicted in eq. (RE1). However, unwanted side reactions may lead to the formation of CO (RE2), while CO can also be hydrogenated to methane (RE3). Depending on the operating conditions, in particular temperature, pressure and gas composition, and the choice of catalyst, the by-product formation can be reduced.