Electrochemically Engineered Octahedral High-Entropy Alloy Nanocrystals for Enhanced Electrocatalysis

Abstract

Abstract High-entropy alloys (HEAs) have attracted increasing attention and shown considerable promise for diverse applications. However, the shape-controlled construction of HEAs with well-defined facets remains a significant challenge due to the large chemical and structural complexity. Herein, an electrochemical square-wave potential method was developed for shape-controlled construction of octahedral PdAuAgZnCu high-entropy alloy nanocrystals (HEA-NCs) in a choline chloride-urea (ChCl-U) based deep eutectic solvent (DES). The mechanism reveals that the formation of the octahedral HEA-NCs is critically dependent on the periodic synergy between a lower potential (EL) for reductive deposition and an upper potential (EU) for oxidative dissolution. Thanks to the high-entropy composition and multi-element synergistic effect, the as-synthesized octahedral PdAuAgZnCu HEA-NCs exhibits exceptional electrocatalytic performance for hydrazine oxidation reaction (HzOR). Compared to monometallic Pd, PdAuAg ternary alloy, PdAuAgZn and PdAuAgCu quaternary alloys, the PdAuAgZnCu HEA-NCs demonstrates superior HzOR activity in an alkaline electrolyte, achieving a high current density of 157 mA cm−2 at 1.2 V vs. RHE, with a low onset potential of 0.4 V vs. RHE at 20 mA cm−2 and a Tafel slope of 141 mV dec−1. Density functional theory (DFT) calculations reveals that the Pd−Cu bridge sites on the PdAuAgZnCu(111) HEA surface possess a low activation barrier of the initial dehydrogenation of hydrazine and exhibit high activity for HzOR with Sequential Mechanism.

The authors' abstract, as published at the source. ACS Applied Nano Materials, 2026 · DOI ↗