Facile Synthesis of Nanocrystalline High-Entropy Diboride Powders by a Simple Sol-Gel Method and Their Performance in Supercapacitor

A sol-gel method was employed for the synthesis of new High-entropy boride (HEB) powders, (Hf0.2Nb0.2Cr0.2Ta0.2Mo0.2)B2, with nanoscale. The as-synthesized powders were obtained at a relatively low temperature of 1650 degrees C, and had small average particle size of 62.09 nm. X-ray diffraction confirmed that the (Hf0.2Nb0.2Cr0.2Ta0.2Mo0.2)B2 powders were hexagonal single-phase without any oxide impurities. In particular, electrochemical performance of the (Hf0.2Nb0.2Cr0.2Ta0.2Mo0.2)B2 powders with multiphase and high-entropy single phase were investigated using a three-electrode system. The improved electrochemical performance of the HEB powders is realized, with 27% higher in specific capacitance compared to the powders with multiphase. The HEB powders electrode exhibits a high capacitance retention of 97.03% after 5000 cycles.