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

The reaction of precursors containing both nitrogen and oxygen atoms with Ni-II under 500 degrees C can generate a N/O mixing coordinated Ni-N3O 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-N-3-V SAC at Ni site under 800 degrees C. For the reaction of Ni-II with the precursor simply containing nitrogen atoms, only a no-vacancy-defect Ni-N-4 SAC was obtained. Experimental and DFT calculations reveal that the presence of a vacancy-defect in Ni-N-3-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 1.35x10(5) h(-1), much higher than those of Ni-N-4 SAC, and being one of the best reported electrocatalysts for CO2-to-CO conversion to date.