Ionic Nickel Embedded in Ceria with High Specific CO Methanation Activity.

CO hydrogenation to methane is gaining increasing interest as one of the most promising ways to store intermittent renewable energy in the form of chemical fuels. Ni particles supported on CeO represent a highly efficient, stable and inexpensive catalyst for this reaction. Herein, Ni-doped CeO nanoparticles were tested for CO methanation showing an extremely high Ni mass-specific activity and CH selectivity. Operando characterization reveals that this performance is tightly associated with ionic Νi and Ce surface sites, while formation of metallic Ni does not seem to considerably promote the reaction. Theoretical calculations confirmed the stability of interstitial ionic Ni sites on ceria surfaces and highlighted the role of Ce-O frustrated Lewis pair (FLP), Ni-O classical Lewis pair (CLP) and Ni-Ce pair sites to the activation of H and CO molecules. To a large extent, the theoretical predictions were validated by in situ spectroscopy under H and CO  : H gaseous environments.