A Planar, Conjugated N<sub>4</sub>‐Macrocyclic Cobalt Complex for Heterogeneous Electrocatalytic CO<sub>2</sub> Reduction with High Activity
Libo Sun, Zhen‐Feng Huang, Vikas Reddu, Tan Su, Adrian C. Fisher, Xin Wang
Abstract
Abstract Metal complexes have been widely investigated as promising electrocatalysts for CO 2 reduction. Most of the current research efforts focus mainly on ligands based on pyrrole subunits, and the reported activities are still far from satisfactory. A novel planar and conjugated N 4 ‐macrocyclic cobalt complex (Co(II)CPY) derived from phenanthroline subunits is prepared herein, and it delivers high activity for heterogeneous CO 2 electrocatalysis to CO in aqueous media, and outperforms most of the metal complexes reported so far. At a molar loading of 5.93×10 −8 mol cm −2 , it exhibits a Faradaic efficiency of 96 % and a turnover frequency of 9.59 s −1 towards CO at −0.70 V vs. RHE. The unraveling of electronic structural features suggests that a synergistic effect between the ligand and cobalt in Co(II)CPY plays a critical role in boosting its activity. As a result, the free energy difference for the formation of *COOH is lower than that with cobalt porphyrin, thus leading to enhanced CO production.