• • The 4H-Au@4H-IrPtNiFeCo NW electrocatalyst reaches 3000 mA cm−2 at 1.90 V in a PEMWE device, a current density that exceeds typical Ir-based OER catalysts by a factor of 3–5, enabling significant reduction in precious metal loading and stack cost for industrial hydrogen production.
• • Stable operation for over 1200 h at 1000 and 2000 mA cm−2 demonstrates a degradation rate below 100 μV h−1, addressing the critical durability bottleneck that has limited HEA catalysts to laboratory-scale half-cell studies and preventing their deployment in commercial PEMWE systems.
• • The 4H-phase HEA core–shell nanowires exhibit enhanced thermal stability, preserving the unconventional atomic stacking and multielement synergy that resist phase transformation under acidic OER conditions (pH < 1, T = 60–80 °C), a failure mode that degrades conventional face-centered cubic HEA catalysts within hundreds of hours.
• • By using Au NWs as a crystallographic template, the synthesis stabilizes HEA phases that are difficult to obtain via conventional routes, providing a scalable strategy to decouple phase control from composition, thereby enabling data-driven discovery of next-generation HEA electrocatalysts for energy conversion.