A first-principles study of electro-catalytic reduction of CO₂ on transition metal-doped stanene

Employing first-principles calculations based on density functional theory, this work examines the activity of 3d transition metal-doped stanene for electro-catalytic CO₂ reduction through the first two electron transfer steps to CO. Our results related to CO₂ activation, the first and a crucial step of the reduction process revealed that, among the entire 3d transition metal row studied, only Ti- and Fe-doped stanene can bind and significantly activate the CO₂ molecule, while the rest of the TM single atoms are inert in activating the molecule. The activation of the CO₂ molecule on Ti- and Fe-doped stanene has been observed in the presence of water as well. In addition, the formation of OCHO has been observed to be energetically preferred over COOH formation as a reaction intermediate, indicating the preference for the formate path of the reduction reaction. Furthermore, despite the strong adsorption of H₂O on the catalyst surface, the presence of water seems to enhance CO₂ adsorption on the catalysts, contrary to what has been observed recently in graphene-based catalysts. Finally, our difference charge density and the Bader charge calculations reveal that the ability of Ti- and Fe-doped stanene in activating the CO₂ molecule and their potential catalytic activity for CO₂ reduction is to be attributed to the charge transfer between the catalyst and the molecule, providing new insights into the rational design of 2D catalysts beyond graphene.