Developing a Mechanistic Understanding of Molecular Electrocatalysts for CO2 Reduction using Infrared Spectroelectrochemistry

The use of infrared spectroelectrochemistry (IR-SEC) as a characterization method for molecular electrocatalysts allows researchers to identify key intermediates and products during the course of an electrochemical reaction. Since such reactions are driven by the application of potential, properly designed cells allow for the examination of the stepwise formation of active species and their subsequent reactivity with substrate. These results can be compared to and independently verified by the concomitant generation of similar species by chemical means. Recently we have used such an approach to characterize the catalytically relevant species and products for the reduction of CO2 by 2,2′-bipyridyl-based ReI and MnI fac-tricarbonyl electrocatalysts. This tutorial review summarizes the requirements of IR-SEC cells and details some examples of mechanistic questions addressed in our laboratory using these methods. IR-SEC is presented as a general method that could be adapted by other laboratories to answer questions of interest in the spectroscopic characterization of the full complement of redox states of organometallic complexes and their reactivities.