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

Abstract

AbstractDeveloping single‐atomic catalysts with superior selectivity and outstanding stability for CO2 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‐N3) stabilized by pyridinic N‐rich interconnected carbon nanosheets. The confinement agent chitosan and its strong interaction with g‐C3N4 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 CO2 electroreduction to CO, exceeding most reported state‐of‐the‐art catalysts. Specifically, the CO Faradaic efficiency (FECO) 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 FECO 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‐N3. This work provides a new designing strategy for the construction of ultrastable and highly selective single‐atom catalysts for efficient CO2 conversion.