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

The reaction of precursors containing both nitrogen and oxygen atoms with Ni under 500 °C can generate a N/O mixing coordinated Ni-N 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-N -V SAC at Ni site under 800 °C. For the reaction of Ni with the precursor simply containing nitrogen atoms, only a no-vacancy-defect Ni-N SAC was obtained. Experimental and DFT calculations reveal that the presence of a vacancy-defect in Ni-N -V SAC can dramatically boost the electrocatalytic activity for CO reduction, with extremely high CO reduction current density of 65 mA cm and high Faradaic efficiency over 90 % at -0.9 V vs. RHE, as well as a record high turnover frequency of 1.35×10  h , much higher than those of Ni-N SAC, and being one of the best reported electrocatalysts for CO -to-CO conversion to date.