Recently, a new family of low-temperature FCs has been proposed, mounting OH--conducting polymer electrolyte membranes. These systems are known as anion-exchange membrane fuel cells (AEMFCs), and show great promise to address successfully crucial issues affecting conventional low-temperature FCs including proton-conducting electrolytes. In particular, the anion-exchange membranes (AEMs) of AEMFCs generate a strongly alkaline environment at the electrodes. Consequently, the efficient operation of AEMFCs does not require electrocatalysts including platinum-group metals (PGMs), which have a very low abundance in Earth’s crust and are prone to supply bottlenecks. Furthermore, in AEMFCs the OH- charge carriers migrate from the cathode to the anode, thus inhibiting fuel crossover. The implementation of efficient AEMFCs requires the development of AEMs: (a) capable of a facile and selective transport of OH- anions; (b) characterized by good mechanical properties; and (c) showing an acceptable chemical and electrochemical stability. To achieve these objectives it is necessary to obtain a detailed understanding of the complex interplay between the structure and the relaxations of AEMs. The latter membranes are extensively studied by broadband electrical spectroscopy (BES) and thermomechanical methodologies including high-resolution thermogravimetry (HR-TG), modulated differential scanning calorimetry (MDSC) and dynamic mechanical analysis (DMA). The unique synergy of these advanced characterization techniques yields an exhaustive understanding of the various relaxation phenomena taking place in the AEMs. The relaxations play a major role in the mechanism of charge migration, which is elucidated together with its interplay with the chemical features and the hydration degree of the AEMs. The resulting information provides fundamental insights, allowing to improve the synthesis of the materials and to optimize the fabrication process of the AEMs.

Interplay between relaxations and structure in anion-exchange membranes (AEMs)

249th National Meeting (2015)

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