Fig. 2

Theoretical calculations of CO₂ activation over Ni. a Schematic including all possible reaction pathways for the carbon dioxide hydrogenation in pink, all intermediates are represented as gray dots. Gray lines indicate plausible links between the primary pathways. b Schematic representation of available sites (T₁, T_f1, B₁, …) on a Ni(211) surface. c Chemisorption energies of CO₂ on different available sites of Ni(111), Ni(100), Ni(110), and Ni(211) crystal facets (T: top, B: bridge). d, e Recombination energies of the carbide, formate and carboxyl pathways on a terrace Ni(111), and a stepped Ni(110) crystal facet. The left panel in each respective figure shows the C, H, and O adatoms from which each intermediate is recombined, as well as reaction intermediates OH and H₂O. The most stable adsorption site is set at zero-energy. f–h Potential energy diagrams for (f) the carbide pathway (g) the formate pathway, and (h) the carboxyl pathway on terrace facets Ni(111) and Ni(100), and stepped facets Ni(110) and Ni(211) of CO₂ hydrogenation as calculated by nudged elastic band (NEB).