62926 2025 eng 1 10 13 64 article Wiley-VCH Weinheim 1 -- -- -- Unsaturated Ni single-atom catalysts (SACs), Ni-Nx (x=1,2,3), have been investigated to break the conventional Ni-N4 structural limitation and provide more unoccupied 3d orbitals for CO2 reduction reaction (CO2RR) 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-N3 atomic sites for efficient CO2 electroreduction to CO at industrial-level current. Density Functional Theory (DFT) calculations revealed that the incorporation of Ni nanocluster effectively stabilizes the unsaturated Ni-N3 atomic sites and modulates their electronic structure to enhance the adsorption of the key intermediate *COOH during CO2RR. Guided by these insights, we prepared an optimal composite catalyst, Ni6@Ni-N3, which features a Ni6N6 nanocluster surrounded by six Ni-N3 single atoms sites, through low-temperature pyrolysis. The morphology and coordinative structure of Ni6@Ni-N3 were confirmed by an aberration-corrected transmission electron microscope (AC-TEM) and X-ray absorption spectroscopy (XAS). As a result, Ni6@Ni-N3 demonstrated a remarkably high CO Faradaic efficiency (FECO) of 99.7 % and a turnover frequency (TOF) of 83984.2 h−1 at 500 mA cm−2 under −1.15 VRHE, much better than those of Ni-N4 with a lower FECO of 86 % at 100 mA cm−2 and a TOF of 39309.9 h−1under identical potential. XAS analyses of Ni6@Ni-N3 before and after long-term CO2RR 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 CO2RR. Angewandte Chemie - International Edition 10.1002/anie.202424552 1521-3773 publish 10.04.2024 Wuyi Zhang Asad Mehmood Ghulam Ali Hui Liu Liyuan Chai Jun Wu Min Liu eng uncontrolled Electrochemical CO2 conversion eng uncontrolled Single atom catalysts eng uncontrolled CO2 electrolysis Angewandte Physik 3 Gefahrgutumschließungen; Energiespeicher Energie Elektrische Energiespeicher und -umwandlung Verlagsliteratur Datei im Netzwerk der BAM verfügbar ("Closed Access") 3.6 Elektrochemische Energiematerialien