Regulating electronic density and interfacial electric field of high-entropy metallenes to enhance oxygen reduction reaction activity

High-entropy metallenes (HEMs), combining high-entropy alloys and ultrathin nanosheets, exhibit lattice strain, geometric effects, and electronic modulation, enhancing oxygen reduction reaction (ORR) activity. We propose a strategy to manipulate the interfacial electric field and electronic density of states in HEMs by adjusting atomic radius and electronegativity differences. Integrating smaller atomic radius elements (Fe/Co/Ni) with larger ones (Pt/Pd/Mo) increases nanosheet curvature, altering the local electric field. Low-electronegativity Fe/Co/Ni/Mo elements lower the d-band center of Pd, and Pt further decreases it, reducing oxygen intermediate adsorption energy. PtPdFeCoNiMo HEMs, with sub-nanometer thickness, high curvature, microstrain, and optimized electronic structure, achieve ORR mass activity of 1.40 A·mg_Pt⁻¹ at 0.9 V (vs. reversible hydrogen electrode [RHE]) in 0.1 M KOH, 21 times higher than Pt/C. They retain excellent performance after 20,000 cycles, with reduced energy barriers for the rate-determining ORR step.