Reduction of CO2to Value-Added Products on a Cu(II)-Salen Complex Coated Graphite Electrocatalyst

This work synthesizes a four-coordinate Cu(II) complex {[Cu-II(L-2(NH))];1} of the tetradentate H(2)L(2)(NH)ligand. The synthesized complex acted as an electrocatalyst for the CO(2)conversion towards C1 and C2 products by activating the stable C-O bond. The catalyst ink (complex1+DMF+Nafion; catalyst concentration similar to 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 KHCO(3)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 -NH(2)anchoring-group in the ligand backbone. The fact was confirmed by electrocatalytic CO(2)conversion experiments in the presence of complex2{[Cu-II(L)];2} as the electrocatalyst, which did not contain the anchoring group in the salen ligand structure.