Provided with an a priori reaction mechanism, eq 13 allows identifying the RDS from the Tafel slope. For instance, a Tafel slope of ~118 mV/dec is usually taken as evidence for the first electron transfer as the RDS, a Tafel slope of ~59 mV/dec the second chemical step following an electrochemical step as the RDS, and a Tafel slope of ~39 mV/dec the second electron transfer step as the RDS. It is important to note that this designation assumes 𝛽 r = 0.5, which has no fundamental justification; furthermore, Marcus theory of electron transfer shows that 𝛽 r = (with 𝜂 being overpotential and 𝜆 being solvent reorganization energy), which changes with overpotential. Additionally, the above view relies on two assumptions. Firstly, it presupposes a slow step that controls the net rate of the reaction, and all other steps are in quasi-equilibrium. Secondly, the coverage of adsorbates on the catalyst surface is assumed to be negligible. In some cases, the second assumption is alleviated by determining adsorbate coverages under quasi-equilibrium conditions. However, quasi-equilibrium conditions implied in both assumptions contradict the fact that the reaction has a net rate and that all elementary steps proceed with the same rate. To overcome these problematic assumptions, the development of a microkinetic model, which considers the thermodynamics and kinetics of all elementary steps, becomes compelling. The presented hierarchical framework has been demonstrated to be capable of deciphering the potential-dependent Tafel slopes of the OER (Figure ), ORR (Figure ) and CO2RR (Figure ).