Mathematical modeling of a half-cell for PEM fuel cells

In this paper, a one-dimensional, steady state, spherical flooded agglomerate model was developed and used to describe the functioning and the mass transport limitations of the cathode in the proton exchange membrane fuel cell (PEMFC). Analytical, asymptotic and numerical solutions were obtained. The analytical solution, which expressed by functions rather than by sets of numbers, permitted the use of functional analyses to identify trends for particular cases. With the developed numerical solution, it was used to explore the effect that operating conditions, physical morphology, and kinetics have on the cell performance. The modeling domain consists of the cathode gas diffuse layer (GDL), membrane and catalyst layer. The model is then compared to the experimental results obtained on a half-cell in a PEM fuel cell. The following processes were considered: Tafel kinetics of the oxygen reduction reaction, proton migration, oxygen diffusion in the agglomerates, and diffusion of O2 in the pores of the active layer and of the gas diffusion layer. The role of a membrane's ion exchange capacity (IEC) at the membrane/gas diffusion electrode interface on the mass transport is analyzed by using the asymptotic solution. (author)