Nitrogen Vacancy Induced Coordinative Reconstruction of Single-Atom Ni Catalyst for Efficient Electrochemical CO2 Reduction

Transition metal nitrogen carbon based single-atom catalysts (SACs) have exhibited superior activity and selectivity for CO2 electroreduction to CO. A favorable local nitrogen coordination environment is key to construct efficient metal-N moieties. Here, a facile plasma-assisted and nitrogen vacancy (NV) induced coordinative reconstruction strategy is reported for this purpose. Under continuous plasma striking, the preformed pentagon pyrrolic N-defects around Ni sites can be transformed to a stable pyridinic N dominant Ni-N-2 coordination structure with promoted kinetics toward the CO2-to-CO conversion. Both the CO selectivity and productivity increase markedly after the reconstruction, reaching a high CO Faradaic efficiency of 96% at mild overpotential of 590 mV and a large CO current density of 33 mA cm(-2) at 890 mV. X-ray adsorption spectroscopy and density functional theory (DFT) calculations reveal this defective local N environment decreases the restraint on central Ni atoms and provides enough space to facilitate the adsorption and activation of CO2 molecule, leading to a reduced energy barrier for CO2 reduction.

Automated summary

In this study, a new plasma-assisted and nitrogen vacancy induced coordinative reconstruction strategy was utilized to optimize the structure of transition metal nitrogen carbon based single-atom catalysts, leading to improved efficiency and selectivity in CO2 electroreduction to CO. The reconstruction process enhanced the kinetics of CO2-to-CO conversion, resulting in significantly increased CO selectivity and productivity with a high CO Faradaic efficiency and large CO current density. X-ray adsorption spectroscopy and density functional theory calculations show that the defective local nitrogen environment created by the reconstruction strategy reduces the constraint on central nickel atoms, facilitating the adsorption and activation of CO2 molecules and lowering the energy barrier for CO2 reduction.