Infrared Spectroscopy As a Probe of Water Structure and Content in Fuel Cell Membrane Materials

Vibrational spectroscopy techniques are being applied to gain insights at the molecular level into processes that control charge transfer and energy conversion efficiency in fuel cells and related electrochemical technologies (i.e., batteries and charge storage systems).  In one direction under investigation, the structure of water confined to nanoscale pore and channel regions of ion conducting polymer membranes is being investigated.  The high internal surface area of materials, such as Nafion 112, enables water interacting with interfaces inside membrane pores and channels to be detected with the use of simple infrared sampling methods.  The structure of interfacial water in Nafion membrane determined through measurements on H₂O/D₂O mixtures in combination with electronic structure simulations will be discussed.  Additionally, infrared spectroscopy is being investigated as a straightforward method for determining membrane water content.  A combination band associated with vibrations of -CF groups is used as an internal standard.  Application of the approach to compare differences in water uptake by fluorinated ionomer materials prepared with and without inorganic filler materials will be presented.