Entropy‐Increase Assisted Anti‐Sintering for Synthesis of High‐Loaded Pt Intermetallic Compounds as Electrocatalysts in PEMFCs

Abstract High‐loaded Pt intermetallic compounds (IMCs) present the practical application potential in low‐Pt PEM fuel cells while ordering transformation under high temperature inevitably leads to severe sintering of high‐density IMC nanoparticles (NPs), thus the decayed oxygen reduction reaction (ORR) performance. Herein, an entropy‐increase assisted anti‐sintering concept is proposed to fundamentally reduce the surface energy of NPs by increasing the mixing entropy, thus hindering the migration and coalescence of NPs. Ex/in situ electron microscopy and density functional theory (DFT) corroborate that the higher the entropy of pristine NPs, the lower the surface energy, the smaller the average size, and the more uniform distribution after annealing. The prepared Pt high‐entropy IMC (Pt‐HEI@Pt/C) demonstrates high metal loading (40.53 wt.%) and small particle size (≈3.15 nm), which endow it with an excellent ORR activity with mass activity (MA@0.9V, 0.65 A mg ⁻¹ _Pt ) and durability over 20k potential‐cycling. Membrane electrode assembly integrated with this catalyst delivers a peak power density of 0.96 W cm ⁻² and an exceptional stability (12.5% decline in MA) under H2‐air condition at 0.1 mg _Pt cm ⁻² . DFT reveals the reinforced strain regulation effect of the HEI core on the Pt shell, which optimizes the *OOH adsorption and elevates the energy barrier of Pt dissolution, thus simultaneously enhancing the intrinsic ORR activity and durability.