A Defect-Engineered High-Entropy Alloy (Al–Cu–Fe–Ni–Ti) Unlocks Enhanced Hydrogen Evolution Performance

High-entropy alloys (HEAs), known for their inherent compositional flexibility, tunable electronic structure, and excellent structural stability, have emerged as promising alternatives to noble-metal electrocatalysts. Nevertheless, their catalytic performance toward the alkaline hydrogen evolution reaction (HER) is often limited by insufficient active site exposure and suboptimal electronic modulation. Herein, we introduce a defect-engineering strategy to unlock the intrinsic catalytic activity of a non-noble Al–Cu–Fe–Ni–Ti HEA. A systematic comparison between high-energy mechanically alloyed and induction-melted HEAs reveals that synthesis-driven structural characteristics critically influence the HER activity. The mechanically alloyed HEA (HEA-1) exhibits a defect-rich microstructure, an enlarged electrochemical surface area (∼9.1 cm2 compared to 8.36 cm2 for HEA-2), and accelerated charge-transfer kinetics, resulting in enhanced HER performance with an onset potential of 230 mV, an overpotential of 301 mV at 10 mA cm–2, a Tafel slope of 130 mV dec–1, and prolonged stability even at a current density of 19.5 mA cm–2, thereby outperforming the melted counterpart (HEA-2). Density functional theory (DFT) calculations further suggest that Ni/Cu-coordinated sites and local atomic clustering are responsible for optimizing hydrogen binding. Collectively, the findings highlight the prospect of mechanically alloyed Al–Cu–Fe–Ni–Ti HEAs as robust and effective catalysts for electrocatalytic hydrogen evolution reaction.