Unveiling lifespan bottlenecks in high-power fuel cell stacks: Flow maldistribution, end-cell degradation, and GDL/CL interactions under accelerated degradation testing

To address the durability challenges in commercial vehicle fuel cell stacks, this study systematically investigated degradation mechanisms in an 80 kW stack via accelerated testing. A variable-spacing flow distribution zone with dynamic resistance adjustment capability was introduced to balance flow resistance, reducing the stoichiometric ratio range from 2.88/1.83 to 2.23/1.88 and significantly improving gas distribution uniformity. After 2000-h testing at 1.8 A cm⁻², the voltage decay rate stabilized at 9.07 mV/h. Critically, the gas distribution end cell(GDE) emerged as the primary lifespan bottleneck, exhibiting a 43.2 % voltage loss (vs. 7.8 % in central cells) due to severe anode flooding (accumulating 80 % of inlet liquid water), which accelerated carbon corrosion and concentration polarization. Long-term operation degraded the gas diffusion layer by reducing porosity and small-pore proportions (<10⁵ nm), impairing water management and increasing concentration polarization. Regional disparities in membrane electrode assembly degradation were observed, with outlet regions and middle channels degrading faster due to flow field-induced uneven gas distribution. Notably, catalyst layer thickness attenuation strongly correlated with Pt particle growth driven by carbon corrosion. These findings provide a universal framework for targeted flow field optimization and PEMFC durability enhancement through integrated water/gas management strategies.