Tuning selectivity of CO₂ hydrogenation over Co catalysts by surface decoration of Sn

Hydrogenation of CO2 to valuable chemicals is in great attention while modulating the selectivity of catalyst is still a challenging issue. Herein, the selectivity tuning from CH4 to CO was achieved over the Co-based catalysts through Sn decoration. The pristine Sn-doped Co3O4 was prepared by a hydrothermal method, and was found to convert as an exposed metal Co phase along with the segregation and accumulation of Sn on the surface after the reduction pretreatment. Through a combination of experimental and density functional theory calculations, the role of Sn was illustrated to modify the Co sites chemically instead of directly participating into catalysis, leading to a weaken dissociation activity of CO and H-2 occurring preferably on the pure Co sites. As a result, it promotes the desorption of intermediate CO from catalyst surface as a main product, thereby achieving high CO selectivity (similar to 100 %) over the Sn-Co catalyst, in sharply contrast to the predominant CH4 selectivity (>90 %) over the un-modified Co site. This work provides an understanding of chemical modulation of the metal sites through a bimetallic architecture, especially in tailoring catalytic selectivity of CO2 hydrogenation.