Diagnosis of ionomers degradation in proton-exchange membrane fuel cell

The ionomer, a key component in the proton exchange membrane fuel cell (PEMFC), plays a determining role in ions/oxygen transport in the catalytic layer, which dominates the performance of PEMFC. However, the degradation of ionomers within the catalyst layer, including decay behavior and diagnostic states, has rarely been reported, as its decay is usually accompanied by the decay of other components of the catalyst layer, such as the catalyst or interface. Herein, we identified critical parameters of degraded ionomers and established their correlation with PEMFC performance by using an isolated H₂O₂ chemical accelerated stability test (C-AST). The performance of the PEMFC strongly depends on the dry proton accessibility, the electrochemical active surface area, and the oxygen transfer resistance, all of which are greatly affected by the decay of the ionomer during C-AST, especially by the decay of the main chain of ionomer with the breaking of C-F bond. A first-order elementary decay model was constructed by correlating the PEMFC key parameters with the ionomer aging time. This investigation provides a robust basis for understanding the ionomer decay mechanism and informs modifications of ionomer properties to enhance PEMFC durability.