Solvation Mediates the Mechanisms of Homogeneous Co-Electrocatalysis at Interfaces

Electrochemical reactions occur near electrode surfaces─this interfacial environment has long obscured the mechanistic insight required to improve selectivity and overall rates. While traditional linear spectroscopies can be used to probe bulk chemical changes, the interfacial response is buried within, limiting insight into solvation environments that modulate homogeneous electrochemical transformations. Here, we address these challenges by studying the protic catalytic mechanism of a Cr-based bipyridine catalyst capable of the selective reduction of carbon dioxide (CO2) to carbon monoxide (CO), at an applied potential using sum frequency generation (SFG) vibrational spectroscopy. Measurements on a series of increasingly complex samples allowed for the characterization of species and solvent environments in an electrochemical solution at a gold working electrode surface. SFG spectra show how applied potential affects the packing of molecules and their conformations at interfaces to allow catalytic species to approach and transfer electrons─emphasizing the divide between species in the bulk versus at the surface and underscoringthe need for further research in this area.