High-entropy materials are mainly composed of high-entropy alloys (HEAs) and their derivates. Among them, HEAs account for a big part. As a new kind of alloy, they are now arousing great interests because of their high mechanical strength, extraordinary fracture toughness, and corrosion resistance compared with traditional alloys. These characteristics allow the use of HEAs in various fields, including mechanical manufacturing, heat-resistant, radiation-resistant, corrosion-resistant, and wear-resistant coatings, energy storage, heterocatalysis, etc. In order to promote the extensive application of HEAs, it is of significance to realize their rational design and preparation. In this paper, a systematic review focusing on the rational design and fabrication of nanosized HEAs is given. The design principles of how to match different elements in HEAs and the premise for the formation of single-phase solid solution HEAs are first illustrated. Computation methods for the prediction of formation conditions and properties of HEAs are also in discussion. Then, a detailed description and comparison of the synthesis methods of HEAs and their derivate, as well as their growing mechanism under various synthetic environments is provided. The commonly used characterization methods for the detection of HEAs, along with the typical cases of the application of HEAs in industrial materials, energy storage materials and catalytic materials are also included. Finally, the challenges and perspectives in the design and synthesis of HEAs would be proposed. We hope this review will give guidance for the future development of HEAs materials.

Nitrogen chemisorption is a prerequisite for efficient ammonia synthesis under ambient conditions, but promoting this process remains a significant challenge. Here, by loading yttrium clusters onto a single-atom support, an electronic promoting effect is triggered to successfully eliminate the nitrogen chemisorption barrier and achieve highly efficient ammonia synthesis. Density functional theory calculations reveal that yttrium clusters with abundant electron orbitals can provide considerable electrons and greatly promote electron backdonation to the N₂ antibonding orbitals, making the chemisorption process exothermic. Moreover, according to the “hot atom” mechanism, the energy released during exothermic N₂ chemisorption would benefit subsequent N₂ cleavage and hydrogenation, thereby dramatically reducing the energy barrier of the overall process. As expected, the proof-of-concept catalyst achieves a prominent NH₃ yield rate of 48.1 μg·h⁻¹·mg⁻¹ at −0.2 V versus the reversible hydrogen electrode, with a Faradaic efficiency of up to 69.7%. This strategy overcomes one of the most serious obstacles for electrochemical ammonia synthesis, and provides a promising method for the development of catalysts with high catalytic activity and selectivity.