Advanced Hydroxyl Ion-Conducting Membranes and Ionomers for Alkaline Fuel Cells

Alkaline fuel cell (AFC)-based power systems offer advantages over proton-exchange membrane fuel cells (PEMFCs). Superior electrochemical reaction thermodynamics for both oxygen reduction and fuel oxidation under alkaline environments make alkaline fuel cell technology a better candidate for sensors, portable and dismounted soldier applications. In addition, AFCs can utilize low-cost, non-precious metal catalysts rather than expensive Pt catalysts used for PEMFCs. Despite their advantages, current AFCs require liquid electrolytes which result in safety and CO2 poisoning concerns that have limited their use. The Phase I project will produce solid polymeric hydroxyl ion-conducting membranes and ionomers based on grafting electrochemically stable, anion receptors on the backbone of alkaline stable polymers. The chemical, thermal, and electrochemical characterization of both hydroxyl ion-conducting solid membranes and alkaline ionomers will be investigated during the Phase I period. The ionomers will improve power densities by reducing ionic resistance within the electrode and membrane interface. The membranes will be tested both in single cells and 5W AFC stack with ammonia borane and sodium borohydride. The development of AFCs using solid hydroxyl ion conductors will allow operation without liquid electrolytes and open up new avenues for variety of fuels such as ammonia borane, sodium borohydride, and hydrogen.