Insights into CeO₂ Particle Size Dependent Selectivity Control for CO₂ Hydrogenation Using Co/CeO₂ Catalysts

The particle size of CeO2 was controlled to study the selectivity toward CO production in CO2 hydrogenation over Co/CeO2 catalysts using ambient-pressure conditions. CeO2 was selected as a typical catalyst support, and it was pretreated by calcination at 450, 750, 900, and 1000 degrees C, which increases the CeO2 particle size prior to impregnation to prepare a series of 5 wt % Co/CeO2. As a result of catalytic testing, it was found that the CO selectivity can be promoted from 24 +/- 2% to 49 +/- 1% when the CeO2 is calcined at 1000 degrees C. We propose that the CeO2 calcination at high temperatures improved its reducibility, strengthened CO adsorption, and weakened H adsorption over the surface of the impregnated Co nanoparticles. Our proposed explanation toward the increased CO selectivity was supported using in situ techniques, i.e., in situ CO DRIFTS and in situ XPS and TEM characterization. This work provides distinctive insight into the relationship between metal-support interaction and the controlled product selectivity in CO2 hydrogenation.