Molten salt assisted synthesis of Single-Atom nickel catalysts for electroreduction of CO2 with nearly 100% CO selectivity

The synthesis of single-atom catalysts (SACs) with target architecture owning ultrathin layered morphology, high surface area and exposed metal active sites is still a great challenge. Herein, we chose 2D bimetallic ZIF-L as precursor combined with molten salt assisted method realizing the aimed synthesis of single-atom Ni imbedded in porous and ultrathin N-doped carbon nanosheets for efficient electrocatalytic CO2 reduction. Molten salt assisted method avoids the collapse, agglomeration, and shrinkage of precursor nanosheets in synthetic process, and benefits the formation of porous structure of nitrogen-doped carbon nanosheets with exposed single-atom Ni active sites. The as-synthesized MS-L-Ni-NC exhibits remarkable electrocatalytic CO2-to-CO performance with the faradaic efficiency over 95.9% in a wide potential range from −0.7 to −1.0 V vs. RHE in H-type cell. An optimal FECO of 98.7% at −0.8 V vs. RHE and a large current density of 20.6 mA·cm−2 at −1.0 V are observed for the MS-L-Ni-NC, which are much higher than those of D-L-Ni-NC without molten-salt assistance and MS-Ni-NC with 3D bimetallic ZIF as precursor. DFT calculations reveal that the coordinated unsaturated pyridine Ni-N sites are the active centers for ECO2RR.