Ionic Nickel Embedded in Ceria with High Specific CO₂ Methanation Activity.

Area of Science:

• Catalysis
• Materials Science
• Renewable Energy Storage

Background:

• Carbon dioxide (CO2) hydrogenation to methane is a key technology for storing intermittent renewable energy.
• Nickel (Ni) supported on ceria (CeO2) is an established catalyst for CO2 methanation.
• Optimizing catalyst performance and understanding reaction mechanisms are crucial for efficient energy storage.

Purpose of the Study:

• To investigate the catalytic performance of Ni-doped CeO2 nanoparticles for CO2 methanation.
• To elucidate the active sites and reaction mechanisms responsible for high activity and selectivity.
• To correlate experimental observations with theoretical calculations for a comprehensive understanding.

Main Methods:

• Synthesis and characterization of Ni-doped CeO2 nanoparticles.
• Operando and in situ spectroscopic studies under reaction conditions (H2, CO2:H2).
• Density Functional Theory (DFT) calculations to model active sites and reaction pathways.

Main Results:

• Ni-doped CeO2 nanoparticles exhibited extremely high Ni mass-specific activity and CH4 selectivity.
• Operando characterization identified ionic Ni and Ce3+ surface sites as crucial for catalysis, not metallic Ni.
• Theoretical calculations confirmed the stability of interstitial ionic Ni sites and identified key Lewis pair sites (Ce-O FLP, Ni-O CLP, Ni-Ce) for H2 and CO2 activation.

Conclusions:

• The exceptional performance of Ni-doped CeO2 in CO2 methanation is attributed to specific ionic Ni and Ce3+ surface sites.
• Theoretical and experimental evidence strongly supports the role of Lewis pair sites in activating reactants.
• This study provides fundamental insights into CO2 hydrogenation catalysis for efficient chemical fuel production and energy storage.