Development of low-cost, high-efficiency PEM Fuel Cells

It is generally accepted that the global demand for energy will dramatically rise in the future. Fuel cells are promising as efficient, non-polluting power sources that produces little noise and have no moving parts. The main problem is the high cost of manufacturing the devices, which has largely limited them to a handful of exotic applications. The objective of the present project is the development and construction of Advanced Polymeric Fuel Cells, which will be able to operate under H2 and/or methanol fuels. High thermodynamic efficiencies and power densities of the order of 0.5 W/cm2 as well as significantly reduced manufacturing cost of the membrane electrode assembly are the main aims of this project. The accomplishment of the above is feasible either by the optimization of both the electrocatalytic performance of the electrode/electrolyte interface or the development of advanced high temperature (150°C200°C) polymer electrolytes with high ionic conductivity. Challenges The ideal fuel for the efficient operation of fuel cells is H2, which exists, in high quantities in nature as the main constituent of water and organic substances. Conventional Polymer Electrolyte Membrane Fuel Cells (PEMFC) using Pt as a catalyst suffer irreversible damage of the electrocatalytic activity if CO (even at 100ppm) is introduced with the fuel gas. Therefore, the fuel processor should be able to supply the fuel cell with CO free H2 and so high complexity and instability characterize the system. In addition, overpotential losses in low temperature fuel cells are due to the activation overpotential developed on the electrode/ electrolyte interface. These losses are essentially related to the electrocatalytic activity of the electrodes (both anode and cathode), which either oxidize H2 or methanol or reduce O2. This is a severe limitation for the achievement of high thermodynamic efficiency, which for the current state of the art fuel cells lies around 35%. Thus there is great room for improvement of the polarization properties of the anode and mainly the cathode materials. In order to overcome the aforementioned constraints: (i) new more active and cost effective electrode materials which can be tolerant to CO poisoning even at CO concentrations 0.5-1% with applications in low temperature fuel cells (7080°C preferably for mobile applications) and (ii) the use of new generation high temperature cheap polymeric electrolyte membranes which will permit the cell operation at temperatures above 150°C will be investigated. This latter medium temperature fuel cell is proposed for stationary applications. However due to the high operating temperature (above 150°C) it is quite tolerant to CO poisoning. Apart from the improved electrocatalytic activity of the new electrode materials, they are more cost effective compared to the existing expensive Pt based electrodes because of both the cheap constituents of the active electrocatalytic phase and their ultra stable properties and long lifetime. This results in greater durability and higher electrocatalytic activity of the fuel cell. Besides the expected significant improvement of the PEM fuel cell performance we expect that the cost of the membrane assembly will be significantly reduced since the new membrane is a factor of 10 less expensive than state of the ar t NAFION®. Fur thermore, such medium temperature fuel cells are expected to be more cost ef ficient than their proposed mobile counterparts due to their higher temperature operation and the anticipated zero water drag coefficient for the membranes which result in more simplified controls.