Directed Structural Evolution of Nickel Nanoparticles into Atomically Dispersed Sites for Efficient CO 2 Electroreduction.

Abstract Electrochemical CO 2 reduction (CO 2 RR) to carbon monoxide (CO) offers a sustainable pathway for carbon utilization, yet challenges remain in terms of improving selectivity and activity. Herein, we report a Ni/NC catalyst synthesized via a milling ‐ pyrolysis method, in which Ni particles anchored on nitrogen‐doped carbon (NC) are electrochemically activated under an Ar atmosphere, leading to their structural evolution into single‐atom Ni sites. After activation in Ar atmosphere, the current density nearly doubles (from ≈30 to ≈60 mA cm −2 ), and concurrently, the Faradaic efficiency of CO stays at ∼90% with the potential set to ‐0.8 V vs. RHE. Comprehensive characterizations, including X‐ray photoelectron spectroscopy (XPS), aberration ‐ corrected scanning transmission electron microscopy (AC ‐ STEM), along with extended X ‐ ray absorption fine structure (EXAFS), confirm the change of Ni particles into atomically dispersed Ni‐N x moieties during activation. Notably, in situ Raman spectroscopy identifies * COOH as the key intermediate, while electrochemical analyses reveal accelerated charge transfer and favorable kinetics for Ar‐Ni/NC. Additionally, the catalyst shows great selectivity and stability over 24 hours of non ‐ stop operation. This study emphasizes the dynamic change of Ni active sites under working conditions, offering useful ideas for designing transition metal catalysts for large ‐ scale CO 2 to CO conversion.