Chemical degradation: Correlations between electrolyzer and fuel cell findings

Membrane chemical degradation of polymer electrolyte membrane fuel cells (PEMFCs) is summarized in this paper. Effects of experimental parameters, such as external load, relative humidity, temperature, and reactant gas partial pressure, are reviewed. Other factors, including membrane thickness, catalyst type, and cation contamination, are summarized. Localized degradations, including anode versus cathode, ionomer inside the catalyst layer, degradation along the Pt precipitation line, gas inlets, and edges are discussed individually. Various characterization techniques employed for membrane chemical degradation, Fourier transform IR, Raman, energy-dispersive X-ray, NMR, and X-ray photoelectron spectroscopy are described and the characterization results are also briefly discussed. The detailed discussion on mechanisms of membrane degradation is divided into three categories: hydrocarbon, grafted polystyrene sulfonic acid, and perfluorinated sulfonic acid. Specific discussion on the radical generation pathway, and the relationship between Fenton's test and actual fuel cell testing is also presented. A comparison is made between PEMFCs and polymer electrolyte water electrolyzers, with the emphasis on fuel cells.