Nanoparticle-Assisted Ni–Co Binary Single-Atom Catalysts Supported on Carbon Nanotubes for Efficient Electroreduction of CO<sub>2</sub> to Syngas with Controllable CO/H<sub>2</sub> Ratios
Xinyao Zou, Chao Ma, Ang Li, Zhan Gao, Zulipiya Shadike, Kun Jiang, Junliang Zhang, Zhen Huang, Lei Zhu
Abstract
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.