Confinement Effect and 3D Design Endow Unsaturated Single Ni Atoms with Ultrahigh Stability and Selectivity toward CO2 Electroreduction

Abstract Developing single‐atomic catalysts with superior selectivity and outstanding stability for CO 2 electroreduction is desperately required but still challenging. Herein, confinement strategy and three‐dimensional (3D) nanoporous structure design strategy are combined to construct unsaturated single Ni sites (Ni‐N 3 ) stabilized by pyridinic N‐rich interconnected carbon nanosheets. The confinement agent chitosan and its strong interaction with g‐C 3 N 4 nanosheet are effective for dispersing Ni and restraining their agglomeration during pyrolysis, resulting in ultrastable Ni single‐atom catalyst. Due to the confinement effect and structure advantage, such designed catalyst exhibits a nearly 100% selectivity and remarkable stability for CO 2 electroreduction to CO, exceeding most reported state‐of‐the‐art catalysts. Specifically, the CO Faradaic efficiency (FE CO ) maintains above 90% over a broad potential range (‐0.55 to ‐0.95 V vs . RHE) and reaches a maximum value of 99.6% at a relatively low potential of ‐0.67 V. More importantly, the FE CO is kept above 95% within a long‐term 100 h electrolyzing. Density functional theory (DFT) calculations explain the high selectivity for CO generation is due to the high energy barrier required for hydrogen evolution on the unsaturated Ni‐N 3 . This work provides a new designing strategy for the construction of ultrastable and highly selective single‐atom catalysts for efficient CO 2 conversion.