Interfacial Stability Engineering of Proton Exchange Membrane Water Electrolyzer Anodes

Proton exchange membrane water electrolysis (PEMWE) is central to renewable hydrogen production, yet anode durability remains difficult to predict from half‐cell catalyst metrics alone. In membrane electrode assemblies (MEAs), acidic oxygen evolution reaction (OER) catalysts must remain active while staying coupled to electron, proton, water and oxygen transport networks. This Review frames PEMWE anode degradation as a multilevel interfacial stability problem. It first defines the near‐surface stability window of Ir/Ru active sites through valence evolution, hydroxylation, lattice‐oxygen participation, reconstruction and metal dissolution. It then shows how this window is reshaped in MEAs by catalyst‐layer percolation, ionomer distribution, pore architecture, porous transport layer (PTL)/catalyst‐layer contact, membrane contamination, metal migration and dynamic operating stresses. Layered diagnostic strategies are summarized to trace macroscopic performance decay back to specific interfacial instability pathways. Future directions are discussed in terms of standardized evaluation, realistic operating environments and data‐driven materials‐interface‐device optimization. This interfacial framework provides a basis for designing durable, non‐noble‐metal PEMWE anodes for practical renewable hydrogen production.