Pyrrolic N anchored atomic Ni-N3-C catalyst for highly effective electroreduction of CO2 into CO

Herein, atomically dispersed Ni-N3-C materials are facilely synthesized by the pyrolysis of Ni-doped ZIF-8. Each single Ni atom is proved to be bonded with three N atoms to form Ni-N3 sites by X-ray absorption spectroscopy. During the pyrolysis at high temperature, the increasing of relative contents and blue-shift binding energy of pyrrolic N can be observed, indicating the Ni might be bonded with pyrrolic N. Moreover, the formation energy (Ef) of NiN3-pyrrolic structure is smaller than that of NiN3-pyridinic calculated by density functional theory (DFT), thus confirming the dominated bonding structure of NiN3-pyrrolic further. The optimum material can achieve an ultra-high CO Faradaic efficiency of 99.37% at-0.75 V vs. RHE with a turnover frequency (TOF) of 3498 h-1 and a high CO partial current density of 80 mA cm-2 at-1.15 V vs. RHE, which is among the best Ni catalysts. Based on DFT results, the NiN3-pyrrolic sites can facilitate both the formation of COOH* intermediate and desorption of CO, which can also suppress the competitive hydrogen evolution reaction (HER) simulta-neously, thus resulting in high catalytic activity and selectivity from CO2 to CO.