Design Principles for Non-Iridium-Based Oxygen Evolution Catalysts in Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolysis (PEMWE) is a leading technology for green hydrogen production, known for its high current density, compact design, and excellent compatibility with variable renewable energy sources. However, the sluggish kinetics and harsh operating conditions of the oxygen evolution reaction (OER) at the anode pose significant challenges, particularly for catalyst activity and durability. While iridium (Ir)-based catalysts remain the industry standard due to their stability in acidic environments, their scarcity and high cost limit large-scale deployment. This review focuses on the development of non-Ir OER catalysts capable of operating under industrially relevant current densities (>1 A cm –2 ) with long-term stability. We first examine ruthenium-based systems, which offer higher intrinsic activity than Ir but suffer from poor stability, and highlight recent strategies developed to enhance their durability. We then discuss earth-abundant, nonprecious metal catalysts (e.g., cobalt, manganese), emphasizing design principles that ensure both high activity and durability under realistic PEMWE conditions. Finally, we discuss emerging machine learning (ML)-driven approaches that accelerate catalyst discovery and optimization. By benchmarking recent progress against DOE targets, this review outlines the path forward for scalable, cost-effective green hydrogen production using non-Ir PEMWE catalysts.