Replace Platinum for Hydrogen Evolution Reaction in the Cathode of Proton Exchange Membrane Water Electrolyzers

ABSTRACT The growing global energy demand and environmental concerns like greenhouse gas emissions call for clean energy solutions. Hydrogen energy, with high caloric value and low environmental impact, is a promising alternative, especially when produced via proton exchange membrane water electrolysis (PEMWE). This process relies on the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), both requiring efficient electrocatalysts. Platinum (Pt), the most effective HER catalyst, is limited by high cost and scarcity, prompting research into Pt alternatives like ruthenium‐based, transition metal derivatives, and metal‐free catalysts that balance cost, efficiency, and stability. This review explores HER mechanisms, Pt‐free catalyst innovations, and the impact of structural and interfacial electrode optimization on performance of HER in acidic media. It also examines electrochemical evaluation techniques, material characterization, and the role of machine learning in catalyst design. By providing a framework for Pt‐free HER catalyst development, this review supports advancements in efficient and sustainable hydrogen energy technologies.