Controlled morphological synthesis of carbon nanotube-enhanced bismuth metal-organic frameworks: A promising electrode material for supercapacitors

Abstract

Among various MOFs, Bismuth MOFs (Bi-MOFs) hold promising potential for the electrode of the supercapcitor because of their large number of active sites and stability. However, Bi-MOFs suffer from low electrical conductivity, which makes them less suitable as supercapacitor electrode materials. The incorporation of a suitable conductive material into Bi-MOFs is an effective way to enhance their specific capacitance. Herein, we incorporated carbon nanotubes (CNTs) into Bi-MOF to form CNTs/Bi-MOF hierarchical nano-micro plate composites to increase specific capacitance of Bi-MOF. Bismuth-MOF (Bi-MOF) was synergistically combined with carbon nanotubes (CNTs) in varying weight ratios relative to Bi-MOF to form CNTs/Bi-MOF composites with ratios of 1:1, 2:1, and 3:1. As a result, the 2:1 CNTs/Bi-MOF composite exhibited an exceptional specific capacitance of 1746 F g⁻¹ at a current density of 1 A g⁻¹. Furthermore, it demonstrated a capacitance retention of 86.41 % after 3000 charge–discharge cycles at 10 A g⁻¹, outperforming both the pristine Bi-MOF and the other composite samples. The 2:1 CNTs/Bi-MOF symmetric supercapacitor device delivered an impressive power density of 403 W kg⁻¹ and an energy density of 17 Wh kg⁻¹. These findings highlight the significance of the 2:1 CNTs/Bi-MOF composite in advancing energy storage technologies.