Unique Oxygen-Bridged Nickel Atomic Pairs Efficiently Boost Electrochemical Reduction of Carbon Dioxide

Benefiting from the synergism between adjacent bimetallic atoms, in comparison with single atom catalysts, the dual atom catalysts have displayed great potential in electrocatalytic CO₂ reduction reaction (CO₂RR). However, the further modulation of the electronic structure of dual atom sites to enhance CO₂RR performance still remains a challenge. Herein, an atomically dispersed oxygen-bridged Ni₂N₆O/NC catalyst with unique Ni-O-Ni sites is successfully synthesized through the microwave pyrolysis of the supported mixture containing the dinuclear nickel phthalocyanine and glucose on N-doped carbon nanosheets. Experiments and density functional theory calculation reveal that the Ni-O-Ni sites can adsorb H⁺ from the KHCO₃ electrolyte to in situ-form the unique Ni-OH-Ni sites without Ni─Ni bonding interaction, which effectively lowers the energy barrier towards the formation of *COOH from CO₂. As a result, the Ni₂N₆OH/NC catalyst exhibits a 99.4% of CO Faradaic efficiency with a 32.4 mA·cm^-2 of CO partial current density at -0.7 V versus RHE in H-cell, much superior to the Ni₂N₆/NC with a Ni-Ni bonding interaction prepared by a similar procedure to that for Ni₂N₆O/NC but replacing microwave pyrolysis by a traditional heating process.