PEMFCs multiscale modeling: Determination of overpotential with description of electron transfer in cathodic EDL at different O2 concentrations

Abstract

The effect of the formation of the electrical double layer (EDL) as a function of O2 concentrations in Pt/H2O interface in a proton-exchange membrane fuel cell (PEMFC) is analyzed in this work. The overpotential associated with the existence of the EDL is calculated at typical fuel cell O2 concentrations by using molecular dynamics (MD). The calculated overpotentials are in the range of −8.865 × 10−6 – 0.0086V for oxygen molar fractions in the cathode between 0 and 0.1273. These overpotential values are included in the ORR kinetic equations of a multiscale model for PEMFCs developed in a previous work to estimate the global electroosmotic drag coefficient and compare it with experimental data from literature. It was found an improvement of the accuracy of the model, at air fed hydration levels of 50% and 70% in the cathode, if the overpotential calculation is carried out considering the electron transfer in the entire interface, not only in the outer Helmholtz plane (OHP) thus, modifying the Frumkin effect calculation.