Untersuchung des Einflusses von Material- und Konstruktionsparametern auf den Wasserhaushalt in Polymerelektrolytmembran-Brennstoffzellen
FacultiesFakultät für Ingenieurwissenschaften und Informatik
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Polymer electrolyte membrane fuel cells feature a successful development history within the past. Their performance and lifetime are affected by the water content, in particular inside the membrane. The present work deals with the examination of specific design and material parameters of the water-bearing components flow field and gas diffusion layer, among others, by X-ray radiography. Two different types of radiation (neutron and synchrotron radiation) are used for water analysis at the macroscopic and microscopic scale. With radiographic studies perpendicular to the active area of 100 cm² transport and accumulation of water can be visualized in different channel geometries using neutron radiation. At various gas humidifications and current densities, an increase of utilization of anode and cathode gas is carried out to evaluate water accumulation inside the channels. The condensate removal capability is quantified by the combination of radiography results with further experimentally measured variables. For the investigated meandering channels, reliable water removal is found to require a minimum pressure drop regarding specific channel-length of at least 14 mbar/m on the anode side and 35 mbar/m on the cathode side. By radiographic images along the active area by means of synchrotron radiation, water thicknesses inside the gas diffusion layers are determined, separately for the anode and the cathode side. The aim is to analyze the influence of the coating with a microporous layer within the gas diffusion layer without adding a hydrophobic impregnation to the fibres. At high gas inlet humidification, the investigated strongly hydrophobic coating provides a comparatively high performance. A partially hydrophilic binder inside the coating leads to a uniform voltage when abrupt changes between semi-humid and humid gases occur. Performance studies are complemented by ex-situ investigations (contact angle, surface energy, hydrostatic head, water vapour sorption).
Subject HeadingsHydrophobieren [GND]
Proton exchange membrane fuel cells [LCSH]
Synchrotron radiation [LCSH]