Flame Synthesized Co-CeO₂ Catalysts for CO₂ Methanation

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Selective conversion of carbon dioxide (CO2) to valuable products like CO, CH4, or CH3OH is a significant challenge in catalysis.
• The metal-support interface critically influences catalytic activity and selectivity in CO2 hydrogenation.
• Optimizing metal particle size, location, and interaction with supports is key for catalyst design.

Purpose of the Study:

• To synthesize Co-CeO2 catalysts with controlled cobalt (Co) content using flame spray pyrolysis (FSP).
• To investigate the influence of cobalt location and structure on catalytic activity and selectivity in CO2 hydrogenation.
• To understand the synergy between cobalt species and the cerium oxide support.

Main Methods:

• Flame spray pyrolysis (FSP) for synthesizing Co-CeO2 catalysts with varying cobalt loadings.
• Characterization of catalyst structure, including cobalt particle size and oxidation state.
• Testing catalytic performance for CO2 hydrogenation at 200 °C.

Main Results:

• Catalysts with ≥5 mol % Co showed segregated CoO/Co3O4 particles, partially reduced to metallic Co nanoparticles (4-5 nm) in the 10 mol % Co-CeO2 sample.
• The 10 mol % Co-CeO2 catalyst exhibited the highest Co-weight-normalized activity for CH4 production (85% selectivity).
• The 2.5 mol % Co-CeO2 sample, with minimal Co reduction and small Co clusters, favored CO formation (79% selectivity) via Co2+-O-Ce sites and oxygen vacancies.

Conclusions:

• FSP is an effective method for tuning Co-CeO2 catalyst structures for selective CO2 hydrogenation.
• Small metallic cobalt nanoparticles predominantly yield methane, while Co2+-O-Ce sites and small clusters favor carbon monoxide.
• Catalyst design leveraging the interplay between metallic cobalt particles and the cerium oxide support enables control over CO2 hydrogenation pathways.