Numerical modelling of charge transfer using the finite element method within the whole active layer of proton exchange membrane fuel cell (PEMFC) electrodes is proposed in order to study the electrocatalyst utilization as characterized by the effectiveness factor. In this way, two modified approaches based on the thin film and agglomerate models are developed for studying ionic ohmic drop effects in the active layer at both the electrolyte layer and electrocatalyst particles scales. The catalyst phase is considered to be a network of spherical nanoparticles instead of the classical representation as a uniform distribution over a surface (thin film model) or in a volume (agglomerate model). Simulations point out unexpected effects at the local level due to the discrete distribution of the catalyst phase as nanoparticles. Finally, the results are applied to the practical case of oxygen reduction and hydrogen oxidation.