Membrane and Performance Study in Polymer Electrolyte Membrane Fuel Cells and Hydrogen Bromine Redox Flow Batteries

This dissertation represents the consideration of the problems of polymer electrolyte membrane fuel cells (PEMFC) and hydrogen-bromine redox flow batteries (RFB). Due to the importance of water management in PEMFCs, all the experiments were strictly controlled at different water hydration conditions. Water uptake and densities were measured for Nafion^® and a series of 3M ionomer membranes. The thermodynamics of water and polymer was analyzed based on water uptake experiment and calorimetry. Furthermore, partial molar volumes (PMV) of water/membrane system was defined for the first time and used to analyze the interaction between water and polymers. Three states of water were identified.

The performance of hydrogen bromine redox flow batteries was investigated. The experimental conditions were varied and optimized with respects of cell temperature, electrolyte concentration, membrane types and electrode layers. In addition, more detailed study of battery kinetics and transport limit issues was implemented by inserting a dynamic hydrogen reference electrode (DHE). Electrochemical Impedance Spectroscopy (EIS) method was utilized to further separate the losses occurred during battery charging and discharging process. It is believed that the bromine/bromide existence in the membrane, carbon paper electrode and Pt catalyst could harm the cell performance. The effective control of bromine and bromide ions is the key to improve the cell performance.