Preparation and characterization of components for Direct Methanol Fuel Cells

Direct Methanol Fuel Cells (DMFCs) are becoming an important area of research, due to their potentialities for a wide application in the next future as electrical power generators because of their low environmental impact. The fields in which these devices may find application involve transportation, portable power sources and distributed generation of clean energy. Yet, the commercial application of these devices is limited by the presence of two main drawbacks that have hindered the achievement of high performances: (i) the slow methanol oxidation kinetics and (ii) the methanol cross-over through the perfluorosulfonic membranes commonly used as electrolyte in these systems. Thus, the topics of this PhD thesis, and, consequently, of my research activity, are concerning with: a) analysis of high temperature methanol electro-oxidation at different Platinum-based catalysts, i. e. unsupported Pt-Ru alloys of various compositions in terms of metal atomic ratio, supported Pt-Ru catalysts varying by different concentrations of metallic phase on carbon support, Pt-decorated Ru catalysts; b) composite Nafion membranes containing different hygroscopic ceramic oxides for high temperature DMFC operation (130-150°C). The recent developments in both fundamental and technological aspects of Direct Methanol Fuel Cells are also described and included in Chapter I of this thesis. The research activity concerning with the development of catalysts for the methanol electro-oxidation reaction and their physico-chemical and electrochemical characterization is reported in Chapter II. The preparation and characterization of composite perfluorosulfonic membranes based on recast Nafion containing finely dispersed inorganic oxides is reported in Chapter III, together with an analysis of the mechanisms governing the conductivity/water retention properties relationship.