Numerical modelling of CO poisoning induced sustained oscillations in the anode potential of a PEM fuel cell

GIUNTA PABLO; LEVITÁN DAVID; LABORDE MIGUEL ÁNGEL

Buenos Aires

Congreso; 20 th Topical Meeting of the International Society of Electrochemistry: Advances in Lithium and Hydrogen Electrochemical Systems for Energy Conversion and Storage; 2017

International Society of Electrochemistry

A dynamic 1-D model for the simulation of the oscillatory behaviour in the potential of the anode of a PEM fuel cell under constant current conditions and CO impurities in the H_2 inlet is proposed. The model is built upon the electrostatic, chemical/kinetic and thermodynamic principles underlying the operation of a fuel cell, without any empirical fitting variables introduced. The model is able to capture the fenomenon of the oscillatory behaviour while giving insight into the effect of the composition and interconnected kinetics between the HOR and CO-electrooxidation. Three electrochemical steps are used for the HOR: Tafel non-potential dependent adsorption of Hydrogen atoms, Heyrovsky potential dependent adsorption-oxidation and Volmer oxidation. A proposed by Zhang[1], three steps are also provided for CO-electrooxidation: CO adsorption, potential dependent H2O adsorption-oxidation and irreversible CO electrooxidation.Following the work of Franco et al.[2], two regions of the electrochemical double layer are modelled. In the ?diffuse layer? farther away from the electrode an explicit system of differential equations is derived for the electrostatic potential and protonic concentration:d(dØ/dx)^2 = -2F/e_cd ? ([H+]_ref ? exp[-F/RT?(Ø-Ø_ref)] ? [SO3-]_ref)?dØTo account for the presence of different species of dipole molecules on the surface of the electrode several modifications have been made from the model proposed by Franco et al. for the ?compact layer? of adsorbed molecules.In agreement with previous works by Zhang[1], Mota and Kadyk[3-4], two different time characteristics for the dynamics of the system are found.