PEM fuel cell cathode catalyst layer durability: An electrochemical spectroscopic investigation

Abstract

Durability and cost form the key technical challenges for PEM Fuel Cells towards true commercialisation. In his regard, cathode catalyst layer degradation assumes significant importance due to severity of the degradation, complex and interrelated phenomena involved and intricacies associated with assessing it in-situ. In the present work, a protocol based on electrochemical impedance spectroscopy is employed and its potential in assessing characteristics of the cathode catalyst layer at various stages of its life is studied over 10,000 long cycles through cyclic voltammetry. Two fuel cells of similar construction cycled to different potential level were subjected to the study and the difference in their degradation behaviour has been captured. The method proves to be very useful in deconvoluting phenomena such as variation in conductivity levels in catalyst layer and the changes in the differential capacitance due to electrolyte-catalyst interfaces, which form the basic reaction zone. With this input, newer insights on the fundamental degradation mechanisms during such prolonged cycling test is also derived. Since it is often not possible to gauge the extent of degradation within the catalyst layer based on the overall performance of an operating fuel cell alone, due to various coupling phenomena, the method can be found to be a convenient tool to diagnose degradation in cathode catalyst layer which is of importance towards fuel cell performance. Moreover, the method is fully non-destructive in nature and has the potential to be used as a diagnostic tool in the field.