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SUMMARYCost and durability are central issues in the commercialization of proton-exchange membrane fuel cells. This study used complex accelerated-degradation protocols to diagnose the degradation modes of low-cost polytetrafluoroethylene-Nafion membrane electrode assemblies (MEAs). Acceleration protocols included open-circuit voltage, relative humidity cycling, and load cycling. Failure modes included measurements of cyclic voltammetry, linear sweep voltammetry, polarization curve, and AC impedance. The four modes (stages) of degradation were determined to be (i) catalyst aging, (ii) creep deformation, (iii) pinhole formation, and (iv) membrane failure. During catalyst aging, the maximum power density decreased by 0.117 mW cm À2 cycle À1 . After the 280th cycle, creep deformation occurred, and the maximum power density decreased by 0.227 mW cm À2 cycle À1. Pinholes led to membrane failure and a final dramatic loss of performance (À0.453 mW cm À2 cycle À1 ). Therefore, membrane failure is the major factor in the failure of MEAs.

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SUMMARYThe durability of proton exchange membrane fuel cells is one of the key issues hindering their widespread commercialization. This study uses the complex accelerating degradation protocol to investigate the performance decay of a membrane electrode assembly. The complex accelerating protocol includes OCV, RH cycling and load cycling. Linear sweep voltammetry, cyclic voltammetry, AC impedance and polarization curves were used to measure key MEA characteristics. The experimental results in this work revealed that the Nafion s film underwent significant thinning after the 1040th cycle. Moreover, during accelerated degradation testing, the electrochemical surface area decreased and was therefore found to be the main factor affecting the performance decay of the MEA.