2D borophene: An emerging material for supercapacitor applications.

The progress of high-performance supercapacitor electrodes based on emerging 2D materials has garnered tremendous attention due to their high power density (>10 kW kg) and long charge-discharge cycle life (>10 cycles). Having been discovered in 2015, 2D borophene has emerged as a unique material among the Xenes due to its excellent electron mobility, metallic behaviour, thermal conductivity, Dirac nature, strength, and flexibility, compared to graphene. Theoretical studies show that borophene possesses a high electron density near the Fermi level which contributes to enhanced charge storage capability and quantum capacitance. This review article aims to provide recent developments in supercapacitor applications of pristine 2D borophene and their hybrid nanostructures with other emerging suitable materials. Initially, the synthesis methods with structural aspects of borophene are introduced and then the progress of borophene in supercapacitors is thoroughly discussed. Finally, current challenges associated with borophene synthesis, energy storage performance, and device fabrication are highlighted. Furthermore, the possible solutions and future perspectives are summarized.