A recently synthesized organometallic iron porphyrin complex referred to as Py2XPFe containing a pyrdine-based hanging group has been shown previously to facilitate the electrochemical reduction of CO2 in acetonitrile. The hanging group promotes proton shuttling to the iron active site and acts to increase the rate of the CO2 reduction reaction compared to its unsubstituted analog TMPFe. With the catalytic capabilities of the molecular catalyst in solution in mind, electrochemical covalent attachment techniques were conducted to graft the Py2XPFe to an electrode surface in order to improve the electron transfer kinetics of the reaction and incorporate practical utility of the Py2XPFe as an electrode-bound catalyst. The modified electrode surface furthermore acts to promote surface enhanced Raman spectroscopy (SERs) and surface enhanced resonance Raman (SERRs) via the surface-enhanced effect and the resoance Rmana effect, which is used to observe the grafted catalyst on the electrode surface with drastic signal enhancement. Spectroelectrochemical SERs and SERRs was conducted to identify intermediates or thermodynamic products within the catalytic cycle of the CO2 reduction reaction as well as the intertwined hydrogen evolution reaction facilitated by the Py2XPFe complex. The Py2XPFe has distinct marker bands in the Raman spectrum which give insight into the coordination environment and spin state of the surface-bound Py2XPFe during catalysis, allowing for a mechanistic investigation into the reduction reactions. Utilizing spectroelectrohchemical SERs and SERRS, investigative methods shed light into the nuances in substrate coordination, site-specific changes and hanging group interactions helping to promote catalysis.

In operando structural and mechanistic investigations of an electrode-grafted iron porphyrin based catalyst for the electrochemical reduction of H+ and CO2 through Raman spectroelectrochemistry

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