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

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 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. 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. 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 the conventional Ni-N4 . 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.