Evaluation of Hydrogen Crossover through Fuel Cell Membranes

Gas crossover is an unavoidable phenomenon in proton exchange fuel cell membranes. Nitrogen and oxygen from the cathode pass through the membrane to the anode, while hydrogen crosses from the anode to the cathode. The hydrogen crossover leads to a reduction in efficiency due to parasitic hydrogen consumption and mixed potentials on the cathode electrode. Furthermore it causes degradation effects and pinhole formation. Hence the hydrogen crossover represents a fundamental factor for the lifetime of a fuel cell and quantification of the crossover is a key factor for membrane qualification. In this article two in situ electrochemical techniques to evaluate the hydrogen crossover are described, cyclic voltammetry and potential step method. Both methods and the achieved results are compared to each other. Finally the potential step method is applied to evaluate the hydrogen crossover as a function of the anode pressure and the hydrogen permeability coefficients are determined.