Selective Transport Properties and Water Binding in Proton Exchange Membranes

摘要

In fuel cell applications, the hydration of the ion-conducting polymer membrane has been shown to have critical influence on its properties such as proton conductivity, methanol permeability, and electro-osmotic drag [1,2]. To better characterize the binding and dynamics of water within the ion-transport membrane, techniques such as differential scanning calorimetry, fluorescence spectroscopy, and Fourier transform infrared spectroscopy (FTIR) have been employed [3]. For Nafion, it was revealed that a portion of the absorbed water molecules in the membrane are hydrogen bonded to sulfonate groups, while others are not intimately bound to the polymer chain and behave in a similar fashion to bulk water. Elucidating the relationships between the binding of water within the membrane and the membrane's chemical and morphological structure and connecting these fundamental materials parameters to membrane transport properties will have important implications for future design and development of membranes for various applications such as direct methanol fuel cells (DMFCs) and desalination.