Decomposition on the degradation mechanism of the cathode catalyst layer under 1000 h of on-road heavy-duty transportation

The lifespan of proton exchange membrane fuel cells in commercial vehicles is frequently constrained by the accelerated degradation of the cathode catalyst layer (CCL) under heavy-duty operational conditions. However, the determinant degradation mechanism of the CCL under on-road heavy-duty conditions remains uncertain. This study reveals the determinant degradation mechanism of the CCL under 1000 h of on-road heavy-duty transportation through multiple diagnostics and quantitative theoretical analysis. The results indicate that the ionomer migration is the fundamental drive of the fuel cell performance loss. The ionomer migration induces the detachment between the Pt catalyst and ionomer, reaching 37.3 % of the electrochemical surface area loss. The proton conduction process is primarily impeded by the discontinuous ionomer network within the CCL, resulting from ionomer migration. Furthermore, the migrating ionomer intrudes the primary pore region, thereby increasing the oxygen transport resistance to the Pt catalyst surface. Performance evolution indicates that the degraded CCL has the maximum power density loss of 42.5 % in comparison to the fresh CCL. The increase in activation and ohmic overpotentials contribute to 43.2 % and 36.5 % of the fuel cell performance loss, respectively. This study highlights the significance of inhibiting ionomer migration and provides a deeper insight into the degradation modes of CCL under on-road heavy-duty operations.