Recently, high-entropy alloys (HEAs) have been extensively investigated due to their unique structural design, superior stability, excellent functional feature and superior mechanical performance. However, most of the reported HEAs focus on studying the compositional design and microstructure and mechanical properties of materials. There are relatively few studies on electrochemical performance and theoretical studies of HEAs. In addition, the potential applications of HEAs as energy storage materials for electrocatalysts have attracted widely attention in the development and application aspects of electrocatalysis. It can be attributed to their high conductivity, excellent structural stability and superior electrocatalytic activities with small overpotential and abundant active sites, which is comparable to the commercial noble metal catalysts. In this review, firstly, we briefly discuss the concept and structure characteristics of high entropy alloys. Then, the research progress of high-entropy alloys as electrocatalysis are also summarized, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), respectively. Finally, the future development trend of HEAs is also prospected for energy conversion fields.

The influence of minor Sc addition on the low-cycle fatigue (LCF) properties of hot-extruded Al-Zn-Mg-Cu-Zr alloy with T6 state was investigated through performing the LCF tests at room temperature and air environment. The results indicate that two alloys show cyclic stabilisation, cyclic hardening and cyclic softening during fatigue deformation. The addition of Sc can significantly enhance the cyclic stress amplitude of the alloy. Al-Zn-Mg-Cu-Zr-Sc alloy shows higher fatigue lives at lower strain amplitudes, while has lower fatigue lives at higher strain amplitudes. For the two alloys, the density and movability of dislocations are related to the change of cyclic stress amplitudes. The existence of Al3(Sc,Zr) phase can inhibit the appearance of cyclic softening phenomenon in the Al-Zn-Mg-Cu-Zr-Sc alloy.

The effects of minor Sc on microstructure and mechanical properties of Al7Zn2Mg1.5Cu0.1Zr alloy under different aging time were investigated by means of tensile test, scanning electron microscopy and transmission electron microscopy, respectively. The results show that the aging strengthening tendency of Al7Zn2Mg1.5Cu0.1Zr(0.2Sc) alloys exhibits the similar feature. After T6 treatment, the maximum values of ultimate tensile strength and yield strength are 700 MPa and 602 MPa, respectively. The tensile fracture of Al7Zn2Mg1.5Cu 0.1Zr(0.2Sc) alloys exhibits a mixed ductile-brittle fracture. The results of TEM observation show that large amounts of GP zones and ©A phase distribute homogeneously inside the grains, and some rod-like precipitates distribute along grain boundaries in two alloys. Besides, there also exist lots of Al 3 (Sc, Zr) phase in Al7Zn2Mg1.5Cu0.1Zr0.2Sc alloy with different treated states. The grain refinement strengthening and precipitation strengthening play the dominant role in the strength increase of the Al7Zn2Mg1.5Cu0.1Zr0.2Sc alloy.

The development of efficient, durable, and affordable electrocatalysts is critical for the advancement of a hydrogen economy, particularly in alkaline media. In this study, we propose CoCrFeNi and CoCrFeNiMo high entropy alloys (HEAs) powders as bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). While there is a performance gap compared to Pt/C, the prepared samples exhibit relatively good electro-catalytic activity with overpotentials of 156.7 mV and 160.5 mV for HER at 10 mA cm À 2 in a 1.0 M KOH solution, respectively. Notably, the CoCrFeNiMo catalyst demonstrates significantly higher OER activity than commercial RuO 2 with an overpotential of 390 mV at 50 mA cm À 2 , and delivers a cell voltage of 1.86 V at a current density of 10 mA cm À 2 for water splitting.