Numerical investigation of gas cross-over and hydrogen peroxide formation in hydrocarbon-based fuel cell membranes

Although hydrocarbon-based proton exchange membranes have gained popularity, their durability needs further evaluation. In this study, a dynamic model is developed for a membrane electrode assembly (MEA) working with sulfonated poly (ether ether ketone) (SPEEK) membrane to predict the concentration profiles of reactants inside the MEA, their cross-over in the membrane, and hydrogen peroxide formation via chemical and electrochemical modes as a function of voltage and membrane thickness. Results show that reactants cross-over, especially oxygen is accelerated under high voltages, promoting the chemical mode of H2O2 formation, whereas the voltage driving force and oxygen concentration simultaneously control the electrochemical mode. Moreover, a 50% reduction in SPEEK membrane thickness yields about 90%, 200%, and up to 50% rise in reactant cross-over, chemical, and electrochemical H2O2 formation modes, respectively. The figures for the chemical mode of H2O2 formation are five orders of magnitude greater than their electrochemical counterparts. This numerical study shows that the most attention should be paid to the anode/membrane interface to mitigate the chemical degradation of hydrocarbon-based proton exchange membranes.