To minimize the voltage losses of the flow batteries, materials with facile electron transfer kinetics should be utilized. A temporary coupling between the electrode and the electrolyte occurs during the electrochemical redox reactions. These reactions take place at the electrode-electrolyte interface where the electrode provides a source or sink of electrons, and the electrolyte carries redox-active species. The interaction at the interface is determined by the nature of the used materials. For battery to perform well, the charge transfer between the electrode and the redox electrolyte must be fast. Generally, the efficiency of an electrochemical reaction is evaluated by the ET rate constant (k 0 ET ). With this, it is possible to determine how fast electron transfers between the electroactive species and the electrode surfaces. Having a high k 0 ET indicates fast system relaxation in response to ET and permits large current densities with low overpotentials. For this reason, it is important to determine the ET rate constant of the employed redox-active pairs when designing more efficient systems. While experimental techniques are well-established to examine electron transfer kinetic, two factors slow down the development of new redox systems. First, if one wishes to discover new redox active species, their syntheses are complex processes that require substantial resources. Second, though, the basic principles of ET reactions are clear, we are not fully aware of the underlying processes at the microscopic level due to their high complexity. To help solve these problems, quantum mechanical modeling can be used both to identify molecular properties and to rationalize kinetic differences. Recent studies by Martínez-González et al. have combined experiments with calculations to study the reduction reactions of a handful of organic molecules on the glassy carbon electrodes in different circumstances.