Competitive Trapping of Single Atoms onto a Metal Carbide Surface.

Controlling atomic adjustment of single-atom catalysts (SACs) can directly change its local configuration, regulate the energy barrier of intermediates, and further optimize reaction pathways. Herein, we report an atom manipulating process to synthesize Ni atoms stabilized on vanadium carbide (Ni-VC) through a nanofiber-medium thermodynamically driven atomic migration strategy. Experimental and theoretical results systematically reveal the tunable migration pathway of Ni atom from Ni nanoparticles to neighboring N-doped carbon (NC) and finally to metal carbide that was obtained by regulating the competitive adsorption energies between VC and NC for capturing Ni atoms. For CO-to-CO electroreduction, Ni-VC exhibits an industrial current density of -180 mA cm at -1.0 V vs reversible hydrogen electrode and the highest Faradaic efficiency for CO production (FE) of 96.8% at -0.4 V vs RHE in a flow cell. Significant electron transfers occurring in Ni-VC structures contribute to the activation of CO, facilitate the reaction free energy, regulate *CO desorption as the rate-determining step, and promote the activity and selectivity. This study provides an understanding on how to design powerful SACs for electrocatalysis.