Controlled Synthesis of a Vacancy-Defect Single-Atom Catalyst for Boosting CO2 Electroreduction

Abstract

The reaction of precursors containing both nitrogen and oxygen atoms with Ni^II under 500 °C can generate a N/O mixing coordinated Ni-N₃ O single-atom catalyst (SAC) in which the oxygen atom can be gradually removed under high temperature due to the weaker Ni-O interaction, resulting in a vacancy-defect Ni-N₃ -V SAC at Ni site under 800 °C. For the reaction of Ni^II with the precursor simply containing nitrogen atoms, only a no-vacancy-defect Ni-N₄ SAC was obtained. Experimental and DFT calculations reveal that the presence of a vacancy-defect in Ni-N₃ -V SAC can dramatically boost the electrocatalytic activity for CO₂ reduction, with extremely high CO₂ reduction current density of 65 mA cm^-2 and high Faradaic efficiency over 90 % at -0.9 V vs. RHE, as well as a record high turnover frequency of 1.35×10⁵ h^-1 , much higher than those of Ni-N₄ SAC, and being one of the best reported electrocatalysts for CO₂ -to-CO conversion to date.

Keywords: CO2 reduction; electrocatalysis; nickel; single atom catalysts; vacancy defects.