An original laboratory X-ray diffraction method for in situ investigations on the water dynamics in a fuel cell proton exchange membrane

A key issue of the polymer membrane-based fuel cells is the water management, since the polymeric electrolyte acts as a good protonic conductor only if sufficiently hydrated. Although models and theoretical studies are widely reported in the literature, experimental investigations are much less available, due to inherent difficulties to sample the membrane in situ. Among the techniques utilized for this purpose, the synchrotron radiation X-ray diffraction has been demonstrated to be a suitable tool to observe the real-time water dynamics in the polymeric membranes. To export this method in laboratories would represent a big advantage because of the limited access to synchrotron facilities. Clearly, the main problem in performing such studies by using conventional X-ray tubes consists of their much lower photon flux, particularly relevant when non-crystalline samples, as polymers, are to be investigated and when extreme collimations of the X-ray beams are required, as in the case of thin membranes. In the present work, we propose a X-ray method, based on the energy dispersive X-ray diffraction, capable to overcome these drawbacks.