Nickel Nanocluster‐Stabilized Unsaturated Ni–N3 Atomic Sites for Efficient CO2‐to‐CO Electrolysis at Industrial‐Level Current

Abstract Unsaturated Ni single‐atom catalysts (SACs), Ni‐N x ( x =1,2,3), have been investigated to break the conventional Ni‐N 4 structural limitation and provide more unoccupied 3d orbitals for CO 2 reduction reaction (CO 2 RR) intermediates adsorption, but their intrinsically low structural stability has seriously hindered their applications. Here, we developed a strategy by integrating Ni nanoclusters to stabilize unsaturated Ni‐N 3 atomic sites for efficient CO 2 electroreduction to CO at industrial‐level current. Density Functional Theory (DFT) calculations revealed that the incorporation of Ni nanocluster effectively stabilizes the unsaturated Ni‐N 3 atomic sites and modulates their electronic structure to enhance the adsorption of the key intermediate *COOH during CO 2 RR. Guided by these insights, we prepared an optimal composite catalyst, Ni 6 @Ni‐N 3 , which features a Ni 6 N 6 nanocluster surrounded by six Ni‐N 3 single atoms sites, through low‐temperature pyrolysis. The morphology and coordinative structure of Ni 6 @Ni‐N 3 were confirmed by an aberration‐corrected transmission electron microscope (AC‐TEM) and X‐ray absorption spectroscopy (XAS). As a result, Ni 6 @Ni‐N 3 demonstrated a remarkably high CO Faradaic efficiency (FE CO ) of 99.7 % and a turnover frequency (TOF) of 83984.2 h −1 at 500 mA cm −2 under −1.15 V RHE , much better than those of Ni‐N 4 with a lower FE CO of 86 % at 100 mA cm −2 and a TOF of 39309.9 h −1 under identical potential. XAS analyses of Ni 6 @Ni‐N 3 before and after long‐term CO 2 RR testing confirmed the excellent stability of its coordinative environment. This work highlights a generalizable approach for stabilizing unsaturated single‐atom catalysts, paving the way for their application in high‐performance CO 2 RR.