Asymmetrical Promotional Effect in the Disorder‐to‐Order Transition of Au‐Pt‐Cu Ternary Alloy Electrocatalysts

Abstract Binary alloys of platinum (Pt) are well‐studied to address the poor poisoning resistance of Pt. Among them, the ordered alloys, also known as intermetallics, tend to show exceptional advantages in activity and durability. In contrast, the medium and high‐entropy Pt alloy systems, with three or more elements, have been reported with better performance but not fully understood, due to the complex relationship of elemental miscibility. Herein a unique asymmetric synergistic effect in the ordering process of a series of ternary alloy Au x Pt 1‐x Cu 3 (x = 0‐1) is reported. The volcano plot of ordering degree (OD) in Au x Pt 1‐x Cu 3 (x = 0‐1) shows its peak in the Au‐rich samples but gradually shifts to Au/Pt equal molar ratio with the increasing temperature. Based on formation energy calculation and molecular dynamics analysis, the unique ordering trend of ternary alloys and the shift of OD peak position are rationalized. Among the studied samples, Au 0.4 Pt 0.6 Cu 3 ‐350 sample exhibits the highest mass activity in electrocatalytic ethanol oxidation (3.58 A·mg Au+Pt −1 ), 4.4 times higher than that of commercial Pt/C. This work not only explores the unique asymmetrical effect in the OD of ternary intermetallics, but also helps to understand the complex inter‐metallic relationship in the medium‐entropy and high‐entropy alloys.