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

Abstract

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 H2 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 (∼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.