Experiment-Theory Synergy: Connecting the Kinetics of the Molecular Catalysis of Electrochemical Reactions with Calculated Energy Landscapes

While energy profiles from quantum mechanical calculations suggest mechanisms for molecular catalysis of electrochemical reactions, they frequently lack experimental kinetic validation due to limited kinetic data or ambiguities linking calculated and experimental observables. Herein, we expand the "energetic span model", traditionally applied in homogeneous systems, to molecularly catalyzed electrochemical reactions focusing on EC1..C n E '-type mechanisms. We thus establish a framework for aligning theoretical turnover frequency estimates with practical cyclic voltammetry measurements in electrochemical systems, i.e., extracted rate constants accounting for diffusion-reaction layer complexities. The analysis also identifies specific kinetic zones, defining conditions under which different catalyst intermediates dominate the diffusion-reaction layer. This approach helps refine the energetic span model for electrochemical catalysis and may improve the alignment of experimental data with the theoretical calculation. It is applied to the experimentally well-studied electrochemical reduction of CO2 to CO using an iron tetraphenylporphyrin catalyst and phenol as proton donor. Previously explored theoretical pathways align partly with experimental data, but important discrepancies exist, especially regarding the reaction's dependence on CO2 binding and proton donor concentration. The findings highlight the challenges in predicting the catalyst behavior and underscore the significance of intermediate energetics in reaction modeling. Nonetheless, cross-talk between theoretical calculations and solid kinetic experimental studies should be a reasonable path toward reaching mechanistic consensus.