Acid-Resistant High-Entropy Alloy Electrocatalysts: Unlocking Durable Oxygen Reduction Reaction and Oxygen Evolution Reaction Performance.

Increasing global energy demands, fossil fuel depletion and rising carbon dioxide (CO2) emissions have made it critical to look for sustainable energy sources. In this regard, proton exchange membrane water electrolysis (PEMWE) and fuel cells (PEMFCs) have gained importance. While PEM systems offer superior operational current density and load flexibility compared to alkaline electrolysis, their performance is limited by slow kinetics of oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR). Achieving high efficiency in acidic environments demands electrocatalysts, capable of sustaining structural integrity with high activity and low overpotentials despite harsh acidic conditions. Thus, high entropy alloys (HEAs) have emerged as compelling solutions; their compositional tunability, intrinsic structural stability and superior corrosion resistance enables them as best candidates to reduce alliance on precious metals while delivering outstanding performance for ORR and OER. This review summarizes recent progress in HEA catalysts, systematically classifying them by metal composition and discussing their stability mechanisms in acid. Finally, the key challenges and future perspectives for the rational design and deployment of acid-stable HEA catalysts in next-generation energy conversion systems are outlined.