Non-covalent interactions and supercapacitance of pseudo-capacitive composite electrode materials (MWCNTCOOH/MnO2/PANI)

• Pseudo-capacitive component in the composite greatly enhance the overall capacitance.
• The contribution of pseudo-capacitance is much higher than double layer capacitance.
• The formation of good interface is critical for good composite electrode material.

We present the in situ oxidative synthesis and electrochemistry of novel pseudo-capacitive nanostructured composite electrode material based on multi-walled carbon nanotube (MWCNT), manganese dioxide (MnO2) and polyaniline (PANI), namely, MWCNTCOOH/MnO2/PANI (PCNAM) for high performance supercapacitor applications. The composite shows about six-fold improvement of electrochemical response compared to MWCNT. The maximum specific capacitance, energy density, and power density of PCNAM were 517.13 ± 15.25 F/g, 71.88 ± 2.12 W h/kg and 10.08 ± 0.26 kW/kg, respectively. The high capacitance of the composite is due to the combination of the electrical double layer capacitance of MWCNT (in MWCNTCOOH) and the gradual introduction of pseudo-capacitance through the redox processes of PANI, COOH (in MWCNTCOOH) and MnO2. We have also demonstrated the charge transfer phenomena through non-covalent supramolecular interactions (i.e., π–π, n–π, and metal–π) between the components of PANI, MWCNTCOOH, and MnO2 due to the presence of double bonds, availability of lone pair electrons, free charges on nitrogen/oxygen atoms, and vacant metal d orbitals. The existence of such non-covalent interaction was supported by data from Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis.

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