A Working Model of Polymer Electrolyte Fuel Cells

Abstract

To describe the performance curves of a polymer electrolyte membrane fuel cell we present a Bernardi-Verbrugge-like model. The model contains an improved description of the cathode diffusion and reactive regions. This improvement was motivated by the need to correct the behavior of the Bernardi-Verbrugge model at high cell current densities, where concentration overpotentials and flooding phenomena start to appear. To achieve this goal, we derived a new expression for the overpotential of the cathode reactive region. The advantage of having such an expression is twofold: false(ifalse) elimination of strong nonlinearities in the solution scheme (with the result of having a fast and stable numerical code), and false(normaliifalse) clear inclusion of concentration and flooding phenomena. Extensive applications of the model are presented. The comparison between the results of our simulations and experimental data show astonishingly good agreements. © 2002 The Electrochemical Society. All rights reserved.

Parameter Estimates for a PEMFC Cathode

“…The assumption of a flooded CAL was found to overestimate the product of the diffusion coefficient and the concentration of O 2 in the liquid electrolyte, 1 whereas a steady-state polarization model including gas pores in the CAL was found to be more realistic. 3,5,8 The objective of this work was to use our previously submitted air cathode model 8 that includes gas pores in the CAL to estimate the values of the volume fraction of gas pores in the gas diffusion layer ͑GDL͒, the volume fraction of gas pores in the CAL, the exchange current density of the O 2 reduction reaction, the effective ionic conductivity of the electrolyte, and the ratio of the effective diffusion coefficient of O 2 in a flooded spherical agglomerate particle to the square of that particle radius from the experimental steady-state polarization curves of the cathode of a H 2 /air PEMFC by least-squares fitting. Because the air cathode is the most important source of voltage loss in a PEMFC and the voltage loss on the H 2 anode is negligible, the experimental polarization curves of a PEMFC air cathode can be obtained from those of a H 2 /air PEMFC after correcting for the voltage drop across the PEM.…”

A Steady-State Impedance Model for a PEMFC Cathode

“…4, while three different values, 0.01, 0.011, and 0.02, were used in Ref. 3. In this work, a value of 0.1 is assumed for this parameter.…”

“…In the steady-state polarization model of Jaouen et al, 4 the existence of gas pores in the cathode CAL was also considered. In contrast to the work of Pisani et al, 3 the solid phase of their cathode CAL was assumed to consist of many spherical agglomerate particles. The existence of a double Tafel slope on a steady-state polarization curve due to the transport limitation by either ionic conduction or liquid-phase diffusion of O 2 and the existence of a quadric Tafel slope due to a combined limitation by both processes were extensively investigated by Jaouen et al 4 Compared to the steady-state polarization experiment, the steady-state impedance experiment is more useful for the study of mass-transport limitations in a PEMFC.…”

Macroscopic Modeling of Polymer-Electrolyte Membranes

“…Verbrugge, especially for systems wherein the membrane is expected to be well hydrated (e.g., saturated gas feeds) [102][103][104][105][106][107][108][109].…”

“…where bulk signifies the concentration outside the film, the reference concentration is that in the membrane in equilibrium with the reference pressure, film δ and A are the thickness and specific external surface area of the film, respectively, and (66) In the third model [56,57,76,103,[194][195][196][197][198][199], denoted PEA, the porous-electrode equations are used and the reaction site is assumed to be a spherical agglomerate composed of supported catalyst, membrane, and possible gas micropores. For this model, the current balance for the ORR is given by…”