Nanoparticle-Assisted Ni–Co Binary Single-Atom Catalysts Supported on Carbon Nanotubes for Efficient Electroreduction of CO₂ to Syngas with Controllable CO/H₂ Ratios

Electrochemical conversion of CO2 to the syngas hybrid with the Fischer–Tropsch (FT) process is a promising way to produce synthetic fuels from renewable energy sources. The product distribution in liquid hydrocarbons produced by FT synthesis has strong dependence on the CO/H2 ratio of the syngas feedstock. Herein, we demonstrated the feasibility of tuning the CO/H2 ratio at a wide range by developing nanoparticle-assisted Ni–Co binary single-atom catalysts for electrocatalytic production of syngas. By controlling the elemental proportion of Ni–Co in the composite catalysts, electrochemical reduction of CO2 to syngas with a tunable CO/H2 ratio from 0.3 to 27.6 was achieved. For the binary catalysts with a Ni–Co ratio of 1:1, the CO/H2 ratio maintains at 1.3–1.5 in a broad potential range from −0.59 to −0.83 V versus reversible hydrogen electrode (RHE) and the total current density reaches ∼32.2 mA/cm2 at −1.0 V versus RHE. The promotion effect of nanoparticles on Ni–Co single-atom catalysts was validated by partial removal of nanoparticles and further density functional theory (DFT) calculations. As revealed by DFT calculations, nanoparticles incorporated in single-atom sites take essential roles in facilitating the adsorption of CO2 and the formation of *COOH. The origin of CO2RR and hydrogen evolution reaction reactivities can be identified as Ni–N4 and Co–N4 single-atom sites, respectively. The dual active sites allow the facile control of the CO/H2 ratio of electrochemical converted syngas, and it will be beneficial to downstream production of diverse chemicals.