CO2 hydrogenation with shape-controlled Pd nanoparticles embedded in mesoporous silica: Elucidating stability and selectivity issues

• Pd cubes and polyedra nanoparticles embedded in mesoporous SiO2 for CO2 hydrogenation
• Embedded Pd nanoparticles much more stable than impregnated counterpart
• Deactivation of the impregnated reference due to thermal sintering
• Selectivity highly affected by Pd site coordination number and particle morphology
• CH4 selectivity decreasing order: corners, edges, steps; (100) facets; (111) facets

Shape-controlled Pd nanocubes and nanopolyedra particles were embedded in mesoporous silica shells and their catalytic properties for the CO2 hydrogenation were compared to a reference Pd/SiO2 catalyst prepared by wetness impregnation. Whereas the Pd impregnated silica exhibits a strong deactivation, the activity of both embedded solids is remarkably stable. This difference is due to a significant Pd particles sintering in the reference catalyst while no increase of particle size is observed for the core@shell solids. CH4 selectivity is shown to be correlated to the mean coordination number of surface atoms which controls the adsorption strength of CO as intermediate species.

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