The impact of air contaminants on humidifier membrane performance

Membrane humidifiers are often used to increase the performance and lifetime of polymer electrolyte membrane fuel cells (PEMFC). In order to avoid possible problems and consequential costs in later fuel cell applications due to the degradation of humidifier membranes, in this work five industrial humidifier membranes (hollow fiber and flat sheet membranes in various material combinations) are tested against five pollutant gases from the environment (NO, NO2, NH3, SO2, O3). Herefor the water transfer capabilities before and after exposure to the pollutant gases is quantified. The results show that polyimides and fluoropolymers are degraded by ozone so that mechanical stability drastically decreases, so that they disintegrate. When polysulfone membranes are tested with pollutants a clear decline in water transfer can be seen over time. The decline of water transfer does not always seem to be due to the presence of harmful gases but could also reflect physical degradation of the polymer. Perfluorinated sulfonic acid-based (PFSA) membranes are particularly sensitive to ammonia.