Experimental characterization and diagonosis tools for proton exchange membrane fuel cells

Tesis presentada por Mauricio Primucci a través del programa de doctorado "Automatización Avanzada y Robótica" y realizada en el Institut de Robòtica i Informàtica Industrial, CSIC-UPC.-- License Creative Commons.A fuel cell is a device that gives electric power directly from electrochemical reduction and oxidation reactions. PEM fuel cells present some properties that make them appropriate for portable and transport applications: high efficiency, no emissions, solid electrolyte, low operating temperatures and high power density. However, some technical problems can be improved, durability of the materials and the appropriate control of the operating conditions. One important aspect of the operating … [+]conditions is the water management. The right water content is needed in the electrolyte and catalyst layers to maximize the efficiency of the PEMFC by minimizing the voltage losses. Water content in the fuel cell is given basically by the generation of the water in the cathode due to the reaction, the humidity of the inlet gases and the transport trough the membrane. This thesis studies, proposes and compares different experimental characterisation methods aimed to provide performance indicators of the PEMFC water state. A systematic use of Electrochemical Impedance Spectroscopy technique is presented and its results are studied in order to analyse the influence of different operating conditions over the PEMFC response. The variables under analysis include: load current, pressure temperature and gas relative humidity. All these variables are considered with inlet gases feeding: H2/O2 and H2/Air. A set of relevant characteristics from the EIS response has been considered. Several equivalent circuits has been analysed and those that have the best fitting with the experimental EIS data are selected. When air is used as oxidant, a simple equivalent circuit with a resistance and a Warburg element is proposed. When Oxygen is used as oxidant, a more complex equivalent circuit is needed. A detailed sensitive analysis is performed indicating those parameters that best capture the influence of the operating conditions. A new experimental characterisation technique, based on the inlet gases humidification interruption is proposed. This dynamic technique combines the information extracted from EIS and the temporal response in order to study the water transport and storage effects in the PEMFC.Al Institut de Robòtica i Informàtica Industrial (IRII), donde he realizado la tesis doctoral, por el gran soporte tanto personal como ecónomico. También agradecer a la Agència de Gestió d’Ajuts Universitaris i Recerca (AGAUR) por la beca pre-doctoral que me han concedido para poder llevar a cabo esta tesis. También al Consejo Superior de Investigaciones Científicas (CSIC) y a la Universitat Politècnica de Catalunya (UPC) por los contratos que me permitieron seguir vinculado al IRII.Peer Reviewe