Electrocatalytic CO 2 Reduction and H 2 Evolution by a Copper (II) Complex with Redox-Active Ligand.

The process of electrocatalytic CO₂ reduction and H₂ evolution from water, regarding renewable energy, has become one of the global solutions to problems related to energy consumption and environmental degradation. In order to promote the electrocatalytic reactivity, the study of the role of ligands in catalysis has attracted more and more attention. Herein, we have developed a copper (II) complex with redox-active ligand [Cu(L¹)₂NO₃]NO₃ (1, L¹ = 2-(6-methoxypyridin-2-yl)-6-nitro-1h-benzo [D] imidazole). X-ray crystallography reveals that the Cu ion in cation of complex 1 is coordinated by two redox ligands L¹ and one labile nitrate ligand, which could assist the metal center for catalysis. The longer Cu-O bond between the metal center and the labile nitrate ligand would break to provide an open coordination site for the binding of the substrate during the catalytic process. The electrocatalytic investigation combined with DFT calculations demonstrate that the copper (II) complex could homogeneously catalyze CO₂ reduction towards CO and H₂ evolution, and this could occur with great performance due to the cooperative effect between the central Cu (II) ion and the redox- active ligand L¹. Further, we discovered that the added proton source H₂O and TsOH·H₂O (p-Toluenesulfonic acid) could greatly enhance its electrocatalytic activity for CO₂ reduction and H₂ evolution, respectively. [ABSTRACT FROM AUTHOR]