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Interaction between the Gas DiffusionLayer and the Gas Flow Channel of polymer electrolyte fuel cell

Final Report Summary - IGDL/GFC (Interaction between the gas diffusionLayer and the gas flow channel of polymer electrolyte fuel cell)

Fuel cells are electrochemical devices that directly convert the chemical energy of hydrogen and oxygen into electricity by producing pure water and discharging only some heat. Due to the use of an electrochemical reaction the conversion efficiency is very high if compared with the conventional generators based on thermal cycles. Inside the different classes of fuel cells, the polymer electrolyte fuel cell (PEFC) is the most promising for low power application and transportation due to their low temperature operation (less than 100 degrees Celsius), quick start up and high power density. Today this kind of fuel cells is close to large scale commercialisation. However, research efforts are still needed toward costs reduction, the increase of power density and the knowledge of physical and chemical processes influencing durability and operational stability of PEFC.

We placed our attention on the water transport inside the PEFC. In fact, due to the low temperature operation and to the production of water inside the cell, the cell system can be flooded if water is not correctly removed and on the other hand, a correct level of humidity inside the cell is fundamental for the polymer electrolyte that needs a good hydration.

Two fuel cell components and their mutual interaction play a key role in the water management: the gas diffusion layer (GDL), the support of the electrode, and the gas flow channel (GFC) ensuring gas distribution over the electrode active area, especially on the cathode side. The 'Interaction between the gas diffusion layer and the gas flow channel of polymer electrolyte fuel cell' (IDGL/GFC) project was focused on fundamental experiments to gain further insights into multi-phase flows (gas / liquid) in porous media (GDL) and flow field channels (GFC). A model cell was designed and built with the aim to study the water transport in GDL / GFC without being dependent on electrochemical reactions. The cell allows water flow visualisation studies of basic and innovative flow fields and GDL under thermally controlled conditions and a large variety of flow conditions. Most promising GDL / GFC arrangements, normally studied by modelling, can be tested in real like environment.

The design, manufacturing and set up of the experimental apparatus was really difficult due to unexpected problems raised up during the initial experimental stage. Though, once the experimental problems were solved and the experimental procedure defined, the obtained results are encouraging allowing a deeper analysis of the large variety of complex flooding phenomena that can occur in real fuel cell.

Water with the addition of a fluorescent dye is introduced in the down chamber of the cell with a flow rate simulating the water production in a real cell. The components to be studied are placed on the top of the water pool. The experiments are recorded by a digital video camera synchronised with other sensors for temperature and pressure.

This fellowship was an opportunity for the fellow to acquire competences on fuel cell electrochemistry and stack design in a leading European research centre on fuel cell involved in the Joint Initiative Technology 'Fuel cells and hydrogen' started in 2008. Moreover, the fellowship was the starting point of a new collaboration between Polytech'Nantes (France) and the Istituto di Tecnologie Avanzate per l'Energia 'Nicola Giordano' (ITAE) of Consiglio Nazionale delle Ricerche (Italy). The objectives are the design and manufacturing of a PEFC stack with high efficiency constraints. Actually this stack will be used in 2012-2013 in the power train of a fuel cell powered prototype car running the world energetic car race, the Shell Eco Marathon. In that sense, the IGDL/GFC project will contribute to Europe competitiveness in the PEFC research field.

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