Reduction of CO2 to Value‐Added Products on a Cu(II)‐Salen Complex Coated Graphite Electrocatalyst

Abstract

AbstractThis work synthesizes a four‐coordinate Cu(II) complex {[CuII(LNH2)]; 1} of the tetradentate H2LNH2 ligand. The synthesized complex acted as an electrocatalyst for the CO2 conversion towards C1 and C2 products by activating the stable C−O bond. The catalyst ink (complex 1+DMF+Nafion; catalyst concentration ∼2 mg cm−2) was surface‐coated over the graphite plate to carry out the reduction reaction in a three‐electrode electrochemical system. An H‐type electrolyzer was employed in 0.5 M KHCO3 electrolyte solution at neutral pH in the carbonated system. A maximum amount of 36 % FE was achieved at −1.80 V vs. Ag/AgCl for 60 min of reaction. The total TON and TOF of the catalyst were calculated to be 9230 and 2.6 s−1, respectively. The CO2‐reduced products were obtained as HCOOH>CH3COOH>CH3OH>C2H5OH, which were formed through multiple–electrons transfer (2 e− to 12 e−) proton‐insertion reactions. The catalytic activity of the Cu(II) complex was enhanced by the presence of the terminal ‐NH2 anchoring‐group in the ligand backbone. The fact was confirmed by electrocatalytic CO2 conversion experiments in the presence of complex 2 {[CuII(L)]; 2} as the electrocatalyst, which did not contain the anchoring group in the salen ligand structure.