Understanding the Origin of Selective Reduction of CO₂ to CO on Single-Atom Nickel Catalyst

Electrochemical reduction of CO₂ to CO offers a promising strategy for regulating the global carbon cycle and providing feedstock for the chemical industry. Understanding the origin that determines the faradaic efficiency (FE) of reduction of CO₂ to CO is critical for developing a highly efficient electrocatalyst. Here, by constructing a single-atom Ni catalyst on nitrogen-doped winged carbon nanofiber (NiSA-NWC), we find that the single-atom Ni catalyst possesses the maximum CO FE of over 95% at -1.6 V vs Ag/AgCl, which is about 30% higher than the standard Ni nanoparticles on the same support. The Tafel analysis reveals that the single-atom Ni catalyst has a preferred reduction of CO₂ to CO and a slower rate for the hydrogen evolution reaction. We propose that the domination of singular Ni¹⁺ electronic states and limited hydrogen atom adsorption sites on the single-atom Ni catalyst lead to the observed high FE for CO₂ reduction to CO.