Mechanical integrity of a polymer electrolyte membrane fuel cell (PEMFC) catalyst layer is critical to the fuel cell's performance and long-term durability due to its direct correlation with the increment of contact resistance and the disconnection of charge transporting paths. However, mechanical failures of the catalyst layer during the operation have been inevitable because of the catalyst layer’s fragile nature. In this work, dramatic enhancement of the catalyst layer's robustness is demonstrated beyond the conventional knowledge of the catalyst layer's brittleness. Through thermal reconfiguration of the ionomer binding, the mechanical properties such as tensile strength and the elongation of the catalyst layer are improved more than 10 times compared with the previously reported intrinsic properties. Thermal reconfiguration above the ionomer transition temperature induces melt flow of the ionomer, this structural reconfiguration enhances the continuity of the load-carrying ionomer in the nanostructure, contributing to relieving load concentration. We also reveal nanostructural origin of the charge conducting paths reconstructed by thermal reconfiguration of the electrode catalyst layer. The thermomechanical behavior of the ionomer by thermal reconfiguration can maximize the continuity of ionic and electronic phases, and the nano-networking itself is highly enhanced as the reconfiguration temperature increases. Above the second transition temperature, initially disconnected ionomer-bound carbon agglomerates are connected due to thermal behavior. The catalyst layer demonstrates electronic singularity as the ionomer penetrates into the interstitial space between the carbon particles and creates electron path insulation. Ionic and electronic resistances are enhanced by approximately 40 % compared to the pristine electrode due to the higher nano-networking of the conductors. In conclusion, long-term durability and cell performance improvement can be expected without cracking and delamination under the hygro-thermal buckling loads through thermal reconfiguration of the PEMFC catalyst layer.

Acknowledgements

This work was supported by the BK21 FOUR Program of the National Research Foundation Korea (NRF) grant funded by the Ministry of Education (MOE), the Technology Development Program to Solve Climate Changes through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020M1A2A2080859), the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2022R1A2C3009087), the Wearable Platform Materials Technology Center (WMC) funded by the National Research Foundation of Korea (NRF) Grant by the Korean Government (MSIT) (No. 2022R1A5A6000846).