Study of electrolytic and electrodic materials for low temperature fuel cell applications

Fuel cells have the potential to become an important energy conversion technology. Research attempts directed towards the widespread commercialization of fuel cells have accelerated in light of ongoing efforts to develop a hydrogen-based energy economy, to reduce dependence on foreign oil and decrease pollution. The concept of polymer electrolyte membrane fuel cells (PEMFCs) has been well-established since early 1960s and mostly directed to niche applications, such as electrical power sources in space crafts and submarines. During the last decade, however, the use of PEMFCs as power sources in mass products, such as electrical vehicles and portable electrical devices, was also brought into focus. This puts new demands on the materials being used, and is in particular true for the separator membrane material, which traditionally is a hydrated perfluorosulfonic polymer. In spite of a great chemical stability, perfluorosulfonic membranes suffer some severe drawbacks, i.e. high cost, strict humidification requirements and, thus, limited operation temperature, water and methanol cross-over. These limitations have stimulated a variety of approaches in the research of alternative polymeric proton exchange membranes. Main topic of my PhD activity concerned with the development of novel polymer or polymer-blend composite matrices achieving fast proton conduction by the addition of an acidic component. Synthesis routes, electrochemical and physico-chemical properties of these materials are discussed in Chapter II. Even tough the aim of this thesis was far from the optimization of technological features, some initial attempts were also devoted to the preparation of electrodes, used to test applicability of the selected membranes in a working fuel cell prototype. This part of the work, together with the results of fuel cell tests, is presented in Chapter III. General aspects related to low temperature fuel cells are briefly described in Chapter I. To access information on the molecular level of the investigated materials, both Raman and infrared spectroscopy was widely used. Thus, an appendix is dedicated to basics and experimental issues of these techniques.