Nature of the Pt-Cobalt-Oxide surface interaction and its role in the CO2 Methanation

Based on our previous investigations, it turned out that the Co3O4 material is a promising catalyst in the ambient pressure CO2 methanation. This work aims at understanding the Pt-Cobalt-Oxide surface interaction and its effect on the catalytic performance. The incorporation of Pt nanoparticles into the mesoporous Co3O4 (Pt/m-Co3O4) and commercial Co3O4 (Pt/c-Co3O4) improves the catalytic activity of both catalysts by a factor of ∼ 1.4 and ∼ 1.9 respectively at 673 K. The same tendency towards the increased basicity was also observed. Morphology-induced surface basicity was previously shown to play a key role in determining the catalytic activity of free-standing supports. From HR-TEM (-EDX), EXAFS, CO2-TPD, and CO chemisorption measurements it was established that during the pre-treatment, Co-Pt alloy particles partially covered by the CoxOy layer are formed. It has been postulated that this structure transformation generates new basic centres, the amount of which per unit surface area is significantly larger for Pt/c-Co3O4 and this in turn is responsible for the higher enhancement effect of the Pt/c-Co3O4 catalyst in the CO2 methanation. This study emphasizes the importance of the surface structure exploration for the dynamic catalytic systems in order to reach maximum activity and selectivity in the CO2 methanation.