Crystal-Phase Engineering of 4H-Phase High-Entropy Alloy Core–Shell Nanowires for Durable Acidic Water Electrolysis
The development of high-entropy alloy (HEA) electrocatalysts for proton exchange membrane water electrolysis (PEMWE) is constrained by the thermodynamic instability of unconventional crystal phases and the trade-off between activity and durability under acidic oxygen evolution reaction (OER) conditions. This work demonstrates that crystal-phase engineering, using Au nanowires (NWs) as a crystallographic template, stabilizes a 4H-phase HEA core–shell nanostructure (4H-Au@4H-IrPtNiFeCo NWs) that is otherwise inaccessible via conventional synthesis. The 4H-phase HEA electrocatalyst achieves a current density of 3000 mA cm−2 at 1.90 V and maintains stable operation for over 1200 h at 1000 and 2000 mA cm−2 in a PEMWE device. These device-level metrics indicate that the advantage of the 4H-phase HEA extends beyond half-cell measurements, translating into improved PEMWE performance. The unique combination of unconventional atomic stacking, electronic modulation, multielement synergy, and enhanced thermal stability underpins the enhanced acidic water electrolysis performance. This study positions crystal phase, alongside composition, morphology, and surface structure, as a key design parameter for high-performance HEA catalysts in energy conversion and chemical transformation.