Electrochemical CO2 Reduction at Glassy Carbon Electrodes Functionalized by Mn(I) and Re(I) Organometallic Complexes

The catalytic activities towards electrochemical CO2 reduction of two new rhenium and manganese complexes, namely fac-Mn(apbpy)(CO)3Br (1) and fac-Re(apbpy)(CO)3Cl (2) (apbpy=4-(4-aminophenyl)-2,2’-bipyridine), in both homogeneous and heterogeneous phases are compared. A glassy carbon electrode (GCE) surface has been functionalized with complexes 1 and 2 by two approaches: a) direct electrochemical oxidation of the amino group with formation of CN bonds, and b) electrochemical reduction of the corresponding diazonium salts with formation of CC bonds. The chemically modified GCEs show efficient conversion of CO2 into CO, with turnover numbers (TONs) about 60 times higher than those of the corresponding catalysts in homogeneous solutions, and in a much shorter time.