Electrochemical energy conversion devices, based on polymer electrolytes have the potential for high system power densities, using relatively in-expensive components, at much higher efficiencies, than can be achieved with heat engines, at their relatively moderate temperature of operation. Proton exchange membrane (PEM) based devices are mostly being considered for hydrogen applications due to their realized very high power densities. Here the need is to develop PEMs that operate with less water and at elevated temperatures. Anion exchange membrane (AEM) based devices have the potential for use with multiple fuels as fuel cells, and to electrolyze not only water but also electrochemically reduce a range of substrates. AEMs can be operated with a large variety of anions depending on the application. Here the need is to use water efficiently for anion transport and as a reactant for hydrocarbons or for hydroxide conducting systems. Next generation ionomers must be designed for water management and utilization and gas permeation or transport without compromising the mechanical properties of the material through excessive swelling or softening.<br/>As we move away from water saturated, state of the art PEM materials such as the perfluorosulfonic acids the ions in the newer materials are typically less dissociated and the transport pathways more tourtuous depending on the properties of the material. The concequence of this is that ion transport shows higher activation energy bariiers, and becomes more coupled with the thermal properties of the polymer, through both side chain motion and backbone relaxation. In this talk we will provide examples of all of these defects to ion transport in a variety of AEM and PEM materials. We will relate morphology via SAXS and microscopy to transport from electrochemical impedance spectrsocpy and NMR diffusion measurements. Importantly we will discuss design rules for the fabrication of practical ion conducting polymers for modern applications.

Ion transport in polymer electrolyte membranes for state of the art energy conversion technologies

249th National Meeting (2015)

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