Deconvoluting HER from CO₂RR on an FeN₄-Derived Catalyst Using Fourier-Transformed Alternating Current Voltammetry

Deciphering electrocatalytic processes with well-defined molecular catalysts is crucial for understanding complex reaction mechanisms. In this study, we investigated iron phthalocyanine (FePc) as a model catalyst for the CO₂ reduction reaction (CO₂RR). With direct current (dc) voltammetry, we described in detail the redox transitions of the catalyst and emphasized its importance for elucidating the formation of the activated catalytic site. The mechanism for CO₂RR and HER was studied with Tafel plot analysis (dc-based) and Fourier-transformed alternating current voltammetry (FTacV). We showed the potential of FTacV as a technique to study catalytic processes vs dc techniques as it allowed us to observe the underlying electron transfer during CO₂RR, revealing the formation of *CO₂^- and defining limiting steps in the reaction. These findings were compared against literature-based spectroscopic results on FePc to propose a possible mechanism. Overall, this work presents FTacV as a powerful tool for mechanistic studies in electrocatalysis, offering more profound insights into electron transfer dynamics during catalytic reactions.