Numerical and experimental investigation on the reactant gas crossover in a PEM fuel cell

Gas crossover through the membrane is one of the key factors for membrane degradation and performance loss of proton exchange membrane fuel cell (PEMFC). The permeation of hydrogen and oxygen through the membrane are consumed with the generation of heat and water but without the generating of useful work, leading to a fuel inefficiency. On the other hand, hydrogen peroxide (H2O2) is most probably formed by the reaction of crossover hydrogen and oxygen at both the anode and cathode side. In addition, the chemical reaction of gas crossover can produce peroxide (HO) and hydroperoxide (HOO) radicals, which could accelerate the membrane degradation. In this study, a numerical simulation model has been built using the partial differential equation solver FreeFem++. A steady-state, two-dimensional, single-phase and non-isothermal model of a single PEMFC has been considered to determine the water content distribution, temperature profile, and permeation of gaseous species within the membrane. An in-situ microprobe technique has been also applied to determine the properties of the oxygen crossover with a range of relevant fuel cell operating temperatures and reactant humidity. The numerical results are compared with experimental data of the diffusion coefficient of reactants gases in the membrane, in order to investigate the gaseous species transport characteristics in the membrane at very low current density.