Liquid Nitrogen Sources Assisting Gram-Scale Production of Single-Atom Catalysts for Electrochemical Carbon Dioxide Reduction

Developing metal-nitrogen-carbon (M-N-C)-based single-atom electrocatalysts for carbon dioxide reduction reaction (CO₂RR) have captured widespread interest because of their outstanding activity and selectivity. Yet, the loss of nitrogen sources during the synthetic process hinders their further development. Herein, an effective strategy using 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]) as a liquid nitrogen source to construct a nickel single-atom electrocatalyst (Ni-SA) with well-defined Ni-N₄ sites on a carbon support (denoted as Ni-SA-BB/C) is reported. This is shown to deliver a carbon monoxide faradaic efficiency of >95% over a potential of −0.7 to −1.1 V (vs reversible hydrogen electrode) with excellent durability. Furthermore, the obtained Ni-SA-BB/C catalyst possesses higher nitrogen content than the Ni-SA catalyst prepared by conventional nitrogen sources. Importantly, only thimbleful Ni nanoparticles (Ni-NP) are contained in the large-scale-prepared Ni-SA-BB/C catalyst without acid leaching, and with only a slight decrease in the catalytic activity. Density functional theory calculations indicate a salient difference between Ni-SA and Ni-NP in the catalytic performance toward CO₂RR. This work introduces a simple and amenable manufacturing strategy to large-scale fabrication of nickel single-atom electrocatalysts for CO₂-to-CO conversion.