Self-governed catalyst layer architecture as a key design strategy for low iridium proton exchange membrane water electrolyzers

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Reduction in iridium (Ir) loading is of utmost importance for sustainable expansion of proton exchange membrane water electrolyzers (PEMWEs). The design of the anode catalyst layer (ACL) is relevant to improve the performance and durability of PEMWEs. In this study, we integrate the strategy of Ir supported on a one-dimensional (1D) molybdenum oxide (Ir-MoO x -comp) based network to achieve in-operando formation of an Ir lattice in ACL. The support present in catalyst acts as a template, guiding the self-assembly of a well-structured ACL, improves Ir utilization and helps to form an ideal pore structure. The PEMWE utilizing this self governed ACL shows superior durability in a catalyst coated membrane (CCM) with no significant degradation after ∼2000 h of operation at 2 A cm −2 with a reduced Ir loading of 0.5 mg Ir cm −2 . Scanning electron microscopy (SEM) reveals morphological evolution of the ACL, indicating improved accessibility of active Ir sites and enhanced microporosity. Complementary atomic force microscopy (AFM) measurements highlight changes in ionomer distribution and an increase in electronically conductive regions. Together, these insights offer a novel and promising route to achieve low Ir loadings for next-generation PEMWE systems. The CCM with Ir-MoO x -comp (OXYGN-M™) catalyst is now commercially available at Cutting-Edge Nanomaterials UG (CENmat). • At 0.5 mg Ir cm −2 , the PEM single cell delivers 2.012 V at 2.0 A cm −2 (80 °C, N117), matching a 2.0 mg Ir cm −2 benchmark. • ∼2000 h continuous operation at 2.0 A cm −2 with ∼3.5 μV h −1 degradation demonstrates industry-level durability. • In-operando “self-governed” Ir/MoO x -comp anode catalyst layer restructures into a 3D, electronically percolating Ir network.

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