Overcoming the Catalytic Bucket Effect in Pt‐based High‐Entropy Nanocages Through Interface Defect and Strain Engineering

ABSTRACT We demonstrate the fabrication of PtPdNiCuMnAu high‐entropy nanocages (HENCs) through a facile liquid‐phase reduction method followed by acid etching treatment. The multi‐component characteristic induces electron redistribution, which regulates the Pt d ‐band center with effect. The incorporation of Mn, endowed with distinct atomic size and coordination environment, introduces significant lattice distortion and atomic‐level defects. Trace Au plays a crucial role in elevating the vacancy formation energy, thus significantly suppressing elemental segregation under electrochemical bias. Additionally, the acid etching treatment further exposes abundant active sites as well as precisely tailors the adsorption kinetics of oxygen intermediates. Benefiting from these synergistic effects, PtPdNiCuMnAu HENCs exhibit a remarkable half‐wave potential ( E _1/2 ) of 0.925 V vs . RHE and a high mass activity (MA) of 1.70 A/mg _Pt . Furthermore, the catalyst displays exceptional electrochemical stability, with only a 4 mV negative shift in E _1/2 and a mere 5.6% loss in MA after 10, 000 accelerated durability test cycles. With this catalyst integrated, the membrane electrode assembly demonstrates a remarkable peak power density of 381.6 ± 3.10 mW/cm ² under H ₂ ‐O ₂ conditions, achieved at a back pressure of 2.0 bar and a cathode loading of 0.2 mg _Pt /cm ² .