In recent years, the concept of entropy stabilization has led to increased research in “high-entropy materials”. These compounds incorporate multiple metals into a single crystalline phase, resulting in interactions between them that offer novel and unexpected properties. Here, we report on the surface evolution and entropy changes of the high-entropy spinel oxide (HEO) Zn(CrMnFeCoNi)₂O₄ upon its use as an electrocatalyst for the oxygen evolution reaction (OER). It was found that electrochemical cycling of this material results in surface reconstruction accompanied by induced leaching of surface Zn from the tetrahedral sites. The formation of a completely new metal (oxy)hydroxide Zn₂Cr_1.5Mn₂Fe₁Co₂Ni_1.5O_xH_y is observed at the surface, leading to an increase in surface entropy over the pristine spinel HEOs. The newly formed surface exhibits improved OER catalytic performance through the adsorbate evolution mechanism (AEM). Removing any one of the cations from this HEO results in a significant decrease in the OER performance. This shows that the electrochemical behavior of the high-entropy oxides depends on each of the metal ions present on the catalyst’s surface, thus providing the opportunity to tailor its electrochemical properties by simply changing the elemental composition.

中文翻译：

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用于水氧化的高熵尖晶石氧化物：表面熵演化和活性促进

近年来，熵稳定的概念导致了“高熵材料”的研究增多。这些化合物将多种金属结合到一个晶相中，导致它们之间的相互作用，从而提供新颖和意想不到的特性。在这里，我们报告了高熵尖晶石氧化物（HEO）Zn（CrMnFeCoNi） ₂ O ₄在用作析氧反应（OER）电催化剂时的表面演化和熵变。研究发现，这种材料的电化学循环会导致表面重构，并伴随着表面锌从四面体位点的诱导浸出。在表面观察到全新金属（氧）氢氧化物 Zn ₂ Cr _1.5 Mn ₂ Fe ₁ Co ₂ Ni _1.5 O _x H _y的形成，导致原始尖晶石 HEO 的表面熵增加。新形成的表面通过吸附质演化机制 (AEM) 表现出改进的 OER 催化性能。从该 HEO 中去除任何一种阳离子都会导致 OER 性能显着下降。这表明高熵氧化物的电化学行为取决于催化剂表面上存在的每种金属离子，从而提供了通过简单地改变元素组成来调整其电化学性能的机会。