Several chemical and mechanical induced PEFC membrane degradation paths are reported in literature. Still the characteristics of membran degradation in cells of technical size under relevant operating conditions are not fully understood. Integral gas crossover measurements serve usually as membrane degradation indicator. The lack of local information makes interpretation of integral data often difficult. Therefore local in-situ tracer gas permeation measurement method by mass spectrometry has been developed. Diffusive and convective permeation measurements during OCV experiments allow for interpretation of the membrane integrity with local resolution over time. These measurements reveal, that local membrane defects trigger locally diffusive and convective permeation, what results in highly non uniform degradation characteristics even under OCV conditions. Chronological occurrence and location of the defects within the active area determine the rate of degradation. Based on the location and temporal characteristics of local defects, it is assumed that the influence of local membrane defects exceeds humidity and temperature induced influence of higher membrane crossover.
展开▼
