Novel Catalyst Layer Design with In Situ Constructed Cross‐Linked Porous Network Toward High‐Performance Proton Exchange Membrane Water Electrolysis

Engineering catalyst layer structure is of significant importance to improve the performance and durability of proton exchange membrane water electrolysis (PEMWE), yet rare efficient design strategies has been reported. This work develops an in situ pore‐making approach to construct cross‐linked porous catalyst layer, which significantly improves catalyst active site utilization compared to conventional catalyst layer (CCL). The electrochemical activity area of the porous catalyst layer membrane electrode assemblies (MEA) (52.22 cm 2 mg Ir −1 ) is 2.10 times higher than that of the CCL‐MEA (24.90 cm 2 mg Ir −1 ), which indicates that more active sites are exposed during pore‐making process, leading to the higher utilization efficiency of the electrocatalyst. As a result, the porous catalyst layer exhibits a high current density of 3.8 A cm −2 at 1.9 V, which is exceeding the U.S. Department of Energy 2025 target (3 A cm −2 @1.9 V), and shows superior durability with no significant degradation after 1600 h of operation at a constant load of 2 A cm −2 . Scanning electron microscope analysis confirms the structural integrity of the porous catalyst layer, while cracks formed in the CCL during testing. These results highlight the benefits of the porous structure in improving mass transport, stability, and overall performance in PEMWE applications.