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 (NiSA-VC) through a nanofiber-medium thermodynamically driven atomic migration strategy. Exper-imental 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 CO2-to-CO electroreduction, NiSA-VC exhibits an industrial current density of -180 mA cm-2 at -1.0 V vs reversible hydrogen electrode and the highest Faradaic efficiency for CO production (FECO) of 96.8% at -0.4 V vs RHE in a flow cell. Significant electron transfers occurring in NiSA-VC structures contribute to the activation of CO2, 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.

Automated summary

Controlling atomic adjustment of single-atom catalysts (SACs) allows for direct changes in their local configuration and energy barrier regulation, optimizing reaction pathways. This study demonstrates the synthesis of Ni atoms stabilized on vanadium carbide (NiSA-VC) through a nanofiber-medium thermodynamically driven atomic migration strategy. The results uncover the tunable migration pathway of Ni atom from Ni nanoparticles to neighboring N-doped carbon (NC) and metal carbide, showing promising catalytic activity and selectivity for CO2 electroreduction.