CO2 methanation (CO2 + 4H2 → CH4 + 2H2O) is a promising strategy for chemically storing renewable H2. For this reason, we have developed a highly active inverse ceria-based catalyst, CeO2/Co. In our previous studies, a clear oxidation and unit cell parameter expansion of ceria was seen in H2 atmosphere, indicative of Ce-hydride (Ce-H) formation. Our results suggest that this species might play an important role in the catalytic properties of this system. However, we have not yet been able to perform operando experiments on catalysts with and without Ce-H. Here, we propose to use XRD to determine the varying Ce-H content and transition metal (TM) oxidation state of catalysts and link it to the overall activity and selectivity of the catalyst for CH4 formation.