Incorporating Zr-metal organic frameworks in multi-walled carbon nanotubes: Effect on electrode properties of energy storage devices

A high surface-area Zr-metal organic framework (Zr-MOF) is synthesized via one-pot solvothermal method. Ex-situ nanocomposites of Zr-MOF and Multi-walled carbon nanotubes (MWCNTs) are prepared, with their properties analyzed at varying compositions. The optimized electrode (15 wt% Zr-MOF in MWCNTs) exhibits a capacitance of 687 F g −1 at 0.5 A g −1 , significantly outperforming pristine Zr-MOF (115 F g −1 ). Moreover, it retains 90.80 % of its initial capacitance after 5000 charge-discharge cycles, compared to 85.08 % for pristine Zr-MOF, demonstrating excellent electrochemical stability. An asymmetric solid-state supercapacitor , using the nanocomposite as the cathode and an MWCNTs electrode as the anode, achieves an energy density of 32.31 Wh kg −1 at a power density of 382.31 W kg −1 . A symmetric supercapacitor with the optimized electrode delivers 36.33 Wh kg −1 at 490.90 W kg −1 . Both devices retain ∼80 % of their initial capacitance after 10,000 charge-discharge cycles. Additionally, the nanocomposites are analyzed as a Zn-Br redox flow battery electrode, and displays well-defined 2Br - /Br 2 redox peaks. While MWCNT electrodes exhibit better catalytic activity and reversibility, Zr-MOF incorporation enhances the capacitive behaviour. The study provides insight into material adaptability for diverse energy storage applications. • MIP-206 (Zr-MOF, 884.67 m 2 /g) is synthesized by one-pot solvothermal method. • Zr-MOF/MWCNTs composites were prepared ex-situ, with varying component ratios. • Successive increment of MOF in the composite increases its capacitive behavior. • 15 wt% Zr-MOF in MWCNTs shows a specific capacitance of 687 F g −1 @ 0.5 A/g. • MWCNT demonstrated quasi reversibility as Zn-Br RFB electrode.