The ORR activity of the catalyst is estimated with the adsorption characteristics of the ORR oxygenated intermediates, i.e., OOH*, OH* + O*, O*, and OH*, using the CHE model. Indeed, the adsorption strength of the intermediates has a great impact on the catalytic. Ideally, the reaction free energies of each elementary step should equal to zero at equilibrium potential 1.23 V (vs SHE). However, if a high degree of oxophilicity is introduced in the catalyst, it may result in an overstabilization of O* and OH* species with respect to the ideal values. The too exergonic adsorption free energies will then translate into endergonic (uphill) reaction steps (Eq. 19, 20 and 21) and an overpotential greater than 1.23 V. The step with the highest positive reaction free energy will also define the rate-determining step (RDS). Often, either O* formation or OH* hydrogenation is found to be the RDS. This will depend on the relative adsorption free energies of O* and OH*, which is very system-specific. Thus, the ORR performance will be dictated by either the O* or OH* adsorption strength.