Innovative electrocatalysts and nanocomposite membranes for low temperature proton exchange membrane fuel cells

For sustainable economic growth and environment protection, energies generated from renewable sources result indispensable. In this field, fuel cell technologies are considered as a key element in the future clean energy becoming a promising solution. Low Temperature Polymer Exchange Membrane Fuel Cells (PEMFCS), including Direct Methanol Fuel Cells (DMFCs), offer several advantages as compared to others systems in term of low emission of pollutants, high energy conversion and efficiency. However, these devices present two major drawbacks, high cost and low durability that must to be solved for a their large scale application and commercialization. Indeed, the Nafion membranes and Pt/C catalysts adopted respectively as electrolyte and electrode component in these devices, are two areas where the technology have issues of cost, durability and efficiency. This means that new materials are necessary. The aim of this PhD work has been the development of advanced materials to be used as both electrocatalysts and electrolyte additives in order to reduce cost, improve the performance and durability of low temperature fuel cells. In particular our interest was focused on non-stoichiometric Calcium Titanate Perovskites, i.e. CaTiO3-δ (CTO) and CaTi0.8Fe0.2O3-δ (CTFO), both used as co-catalyst for the oxygen reduction reaction (ORR) which is the main rate-decreasing step in low temperature fuel cell devices. The aim was to improve the stability and durability of Pt catalysts and support Pt catalytic activity in order to reduce its loading. The CaTiO3-δ perovskite was also used as additive in Nafion membrane in order to enhance the water retention, the mechanical properties of the membrane and reduce the gas/methanol crossover. Synthesis routes, electrochemical and powerful physical-chemical analysis of these materials were carried out, here reported and discussed.