On the development of new electrolytes for fuel cell applications:
Max-Planck-Institut für Festkörperforschung, DE
Keywords: PEM Fuel cell
A critical part of any fuel cell is the separator material, an electrolyte conducting preferentially one kind of ion but impervious to electrons (and holes). The different types of fuel cells are even named according to the different electrolytes used as separator materials, i.e. SOFC for "solid oxide fuel cell", MCFC for "molten carbonate fuel cell", AFC for "alkaline fuel cell", PAFC for "phosphoric acid fuel cell" and PEMFC for "polymer electrolyte membrane fuel cell". During the last decade, there has been tremendous progress with respect to achieving both performance and long-term stability. While this success was essentially the result of sophisticated engineering efforts making use of available materials, the inherent properties of the materials employed to date seem to inhibit further progress of this promising technology. This presentation emphasizes the potential of various simulation techniques in the development of new electrolyte materials.
Ab initio and quantum molecular dynamics-, Monte Carlo- and phenomenological simulations combined with appropriate experimental techniques may be used as complementary tools. This will be demonstrated for the development of:
(i) highly proton conducting oxides by optimization of the crystallographic and electronic structure of acceptor-doped BaZrO3-based materials [1-4]. Such electrolytes allow the operation of solid oxide fuel cells (SOFC) at reduced temperature (500-800°C), where materials compatibility problems are significantly reduced. (ii) Solvated proton conducting polymers and composite membranes with low Onsager cross-coefficients for the coupled transport of protons and water or methanol by micro structural control. These materials are relevant for direct methanol fuel cells (DMFC), for which the so-called methanol and water "cross-over" is still the key problem to be solved . (iii) Novel side-chain polymers with heterocycles (e.g. imidazole) as proton solvating moieties and high proton mobility at medium temperatures (150-250°C), where poisoning effects of available electro catalysts (e.g. Pt/Ru) are drastically reduced. As opposed to conventional membranes, the high proton mobility in these materials does not rely on the presence of water (high relative humidity) [6-9].
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NSTI Nanotech 2003 Conference Technical Program Abstract