No abstract

We propose a dynamic mechanistic model, based on nonequilibrium thermodynamics and electrodynamics, describing the transient response to current perturbations of an electrochemical double layer at the metal/electrolyte interface in the presence of electrochemical reactions. As an example of application, we have simulated the hydrogen oxidation reaction taking place in a polymer electrolyte fuel cell anode. The model is composed of ͑i͒ a 0-D inner layer submodel describing the composition of the metallic phase surface where water and reactant can be adsorbed, and the generated electric potential difference between the metal and the electrolyte phases; and ͑ii͒ a 1-D diffuse layer submodel in the electrolyte constituted by spatially moving ions and counterions, describing the ionic transport by migration-diffusion, based on the coupling of a Nernst-Planck's equation with a Poisson's equation. At the interface, the reaction kinetics depending on the potential difference is coupled with the inner-layer model through the charge conservation law. The numerical model allows dynamic simulation of the evolution of the local electric potentials ͑ionic and electronic͒ and concentrations inside the interface, and the influence of the working conditions on the impedance spectra characteristics.

Proton Exchange Membrane Fuel Cells (PEMFC) are energy efficient and environmentally friendly alternatives to conventional energy conversion systems in many yet emerging applications. In order to enable prediction of their performance and durability, it is crucial to gain a deeper understanding of the relevant operation phenomena, e.g., electrochemistry, transport phenomena, thermodynamics as well as the mechanisms leading to the degradation of cell components. Achieving the goal of providing predictive tools to model PEMFC performance, durability and degradation is a challenging task requiring the development of detailed and realistic models reaching from the atomic/molecular scale over the meso scale of structures and materials up to components, stack and system level. In addition an appropriate way of coupling the different scales is required. This review provides a comprehensive overview of the state of the art in modeling of PEMFC, covering all relevant scales from atomistic up to system level as well as the coupling between these scales. Furthermore, it focuses on the modeling of PEMFC degradation mechanisms and on the coupling between performance and degradation models.