Structure Sensitivity of CO₂ Conversion over Nickel Metal Nanoparticles Explained by Micro-Kinetics Simulations

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Nickel metal nanoparticles are key catalysts for CO2 methanation in power-to-methane applications.
• The Sabatier reaction's efficiency is known to be structure-sensitive, with optimal performance linked to specific nanoparticle sizes.
• Understanding elementary reaction steps on different nickel facets is crucial for designing improved catalysts.

Purpose of the Study:

• To elucidate the structure sensitivity of CO2 methanation over various nickel metal facets.
• To identify the critical elementary reaction steps and kinetic routes governing nickel-based methanation.
• To explain the observed activity-versus-nanoparticle size trends in the Sabatier reaction.

Main Methods:

• Density functional theory (DFT) calculations were employed to study reaction mechanisms.
• Micro-kinetics modeling (MKM) simulations were used to assess catalytic activity.
• Wulff-constructed nickel nanoparticles were analyzed to correlate facet exposure with activity.

Main Results:

• Ni(111), Ni(100), and Ni(211) facets showed minimal activity for CO2 methanation.
• The stepped Ni(110) facet exhibited the highest catalytic activity.
• A combination of carbide and formate pathways dominated, with H2CO* dissociation identified as the rate-limiting step on Ni(110).

Conclusions:

• The Ni(110) facet is the most effective for CO2 methanation.
• The study provides a mechanistic explanation for the structure sensitivity of the Sabatier reaction.
• Findings guide the rational design of efficient nickel-based methanation catalysts for CO2 conversion.