Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Atomistic Oxygen Reduction Reaction Model

Abstract

In this work is presented a kinetic model for the oxygen reduction reaction (ORR), which is studied considering a dissociative mechanism and using electronic structure calculations. This model was developed to include it in a multiscale model for a Proton Exchange Membrane Fuel Cell (PEMFC). As result of this work the energetic properties and electronic structure properties of the system made up by the principal intermediates (O, O2, OH, H2O) and the Pt surface are calculated, also it is obtained the energy barriers for each step and the energy difference between products and reactants, allowing to construct the potential energy surface diagram for the complete oxygen dissociation mechanism. These results point out that the dissociation of adsorbed O2 is the reaction limiting step, it is associated whit the high adsorption energy of this molecule which is explained using electronic structure features as the local density of states. Also the calculated activation energies for the ORR cause an improvement of the phenomenological description of a PEMFC when they are used in a multiscale model.