The framework comprises two essential submodels, as illustrated in Figure . The first one is a microkinetic model that integrates the thermodynamics and kinetics of all elementary steps. The second one processes the LRE, encompassing microscopic EDL effects and mass transport in solution. The two submodels are coupled via boundary conditions at the most probable reaction plane (RP) that is located in close proximity to the surface of the electrocatalyst. Typically, the outer Helmholtz plane is chosen as the RP for the convenience of applying Frumkin corrections. However, it has also been proposed that the position of the RP should be considered as a function of the overpotential. The microkinetic model requires a priori knowledge of the reaction mechanism that is usually inferred by combining key intermediates identified from spectroscopic experiments and first principles-based calculations. A specific reaction mechanism is expressed as a series of elementary steps,