High‐Entropy Rare‐Earth‐Doped Pt Alloy Concave Nanocubes with High‐Index Facets for Hydrazine Oxidation Electrocatalysis

High-entropy doping of multicomponent alloy nanocrystals enclosed by high-index facets (HIFs) is a great challenge due to the high surface energy from HIFs and their distinct standard reduction potential and atom sizes between different metals. Herein, a novel non-aqueous system, choline chloride-urea-based deep eutectic solvent, is proposed as a versatile medium to design a high-entropy rare-earth-doped Pt alloy PtYLaNdSmEuGdTbDyHoEr (HERED-Pt) concave nanocube with HIFs by the electrochemical method. Thanks to the high-index faceted characteristics and the high-entropy rare-earth-doped elemental synergy, the as-synthesized HERED-Pt concave nanocubes exhibit remarkable electrocatalytic performance for hydrazine oxidation reaction (HzOR) with high current density (170.58 mA cm^-2) and low on-set potential of 369.2 mV, which is superior than the quinary rare-earth-doped Pt alloy PtNdSmGdTbDy (QRED-Pt), single rare-earth-doped Pt alloys (PtY, PtLa, PtNd, PtSm, PtEu, PtGd, PtTb, PtDy, PtHo, PtEr), monometallic Pt concave nanocubes and commercial Pt/C catalyst, representing a state-of-the-art electrocatalyst for HzOR. Density functional theory (DFT) calculations reveal that the HERED-Pt(510) stepped plane can effectively reduce the energy barrier and exhibits higher electrocatalytic performance than that of QRED-Pt(510), single rare-earth-doped PtTb(510), and monometallic Pt(510) stepped planes for HzOR. This study provides a feasible high-entropy doping strategy to effectively achieve a highly efficient electrocatalyst for HzOR.