Electrocatalytic Reduction of Carbon Dioxide to Carbon Monoxide by a Polymerized Film of an Alkynyl-Substituted Rhenium(I) Complex

The alkynyl-substituted ReI complex [Re(5,5´-bisphenylethynyl-2,2´-bipyridyl)(CO)3Cl] was immobilized by electropolymerization onto a Pt-plate electrode. The polymerized film exhibited electrocatalytic activity for the reduction of CO2 to CO. Cyclic voltammetry studies and bulk controlled-potential electrolysis experiments were performed by using a CO2-saturated acetonitrile solution. The CO2 reduction, determined by cyclic voltammetry, occurs at approximately -1150 mV versus the normal hydrogen electrode (NHE). Quantitative analysis by GC and IR spectroscopy was used to determine a Faradaic efficiency of approximately 33% for the formation of CO. Both values of the modified electrode were compared to the performance of the homogenous monomer [Re(5,5´-bisphenylethynyl-2,2´-bipyridyl)(CO)3Cl] in acetonitrile. The polymer formation and its properties were studied by using SEM, AFM, and attenuated total reflectance (ATR) FTIR and UV/Vis spectroscopy.