Recent advances in spectroelectrochemistry related to molecular catalytic processes

Continuing interest in renewable energy utilization, the depletion of nonrenewable petrochemical feedstocks and rising atmospheric concentrations of CO₂ from anthropogenic emissions have made molecular electrocatalytic processes involving CO₂, H₂, and O₂ important research foci. One of the touted advantages of molecular electrocatalytic processes, in comparison to heterogeneous systems, is the relative ease with which the active species can be characterized and the catalyst optimized using synthetic methodology. This requires, however, that species generated by the application of potential be spectroscopically studied, which can be difficult given that changes in reactivity can occur. Spectroelectrochemical methods offer a way to study speciation as a function of potential and time, such that catalytic and noncatalytic reactivity can be understood in the context of an overall mechanism. Paired with steadily advancing electrochemical techniques for quantifying the thermodynamic and kinetic parameters of molecular electrocatalysts, spectroelectrochemical data sets can be used to generate a rich understanding of molecular behavior. Recent reports on the use of spectroelectrochemistry to understand molecular electrocatalytic reactions using transition metal complexes are summarized herein.