Redox-Active Tetramino-Benzoquinone π-π Stacking and H-Bonding onto Multiwalled Carbon Nanotubes toward a High-Performance Asymmetric Supercapacitor

The energy density of supercapacitors with carbon-based electrode materials is generally restricted by their limited electric double-layer capacitance (EDLC). The introduction of electroactive molecules to acquire abundant pseudocapacitance represents an efficient way to achieve a high-performance capacitor system. Herein, this work anchors redox-active tetraminobenzoquinone (TABQ) with multiwalled carbon nanotubes (MWCNTs) to form a composite (denoted as TABQMWCNTs). Due to the strong pi-pi stacking and H-bonding interaction between TABQ molecules and the MWCNT host, the TABQMWCNTs acquire enhanced structural stability and shortened pathway for electrons/charges, which facilitate their energy storage capability. Specifically, by adjusting the mass ratio of TA(B)Qto MWCNTs, the composite can attain a high specific capacitance of 463 F g(-1) at 1 A g(-1) compared to that of bare MWCNTs (17 F g(-1)). Theoretical calculations show that TABQMWCNTs own a lower adsorption energy toward H+, suggesting its better EDLC capability through charge accumulation. Moreover, in situ Fourier transform infrared spectroscopy (FTIR) and Raman tests reveal that the TABQmolecules hosted on MWCNTs undergo a reversible evolution of the quinone-to-phenol structure during the discharging/charging process, further verifying its promising pseudocapacitance through faradic reactions. In addition to the high capacitance, the TABQMWCNT composite also exhibits good cydability in a threeelectrode system, i.e., 76.8% of the initial capacitance is obtained after cyding for 6000 times at 10 A g(-1). An asymmetric supercapacitor (ASC) of TABQMWCNTs//activated carbon achieves a high energy density of 15.6 Wh kg(-1) at a power density of 700 W kg(-1). Moreover, it also shows a long-term cydability of 91.5% after 10,000 cycles at 5 A g(-)(1).

Automated summary

This study demonstrates the preparation of a composite material TABQMWCNTs by anchoring redox-active tetraminobenzoquinone (TABQ) with multiwalled carbon nanotubes (MWCNTs). The composite material exhibits enhanced structural stability and improved charge transfer capability, resulting in high energy storage capacity and electric double-layer capacitance. Moreover, the TABQMWCNTs also show good cyclic stability and energy density.