Metallic-Ir-based anode catalysts in PEM water electrolyzers: Achievements, challenges, and perspectives

Water electrolysis for clean hydrogen generation is the most promising solution to boost the development of a sustainable and clean hydrogen economy. However, its energy efficiency is significantly limited by the sluggish oxygen evolution reaction (OER) at the anode, especially for the highly desirable proton exchange membrane (PEM) water electrolyzers. Among others, expensive and scarce Ir-based catalysts are the only candidate because of their promising catalytic activity and stability for the OER in challenging acidic media. Here, we highlighted recent achievements in developing advanced Ir catalysts with reduced loading and improved performance, along with the grand challenges and possible innovative strategies for addressing these issues.