Review
Understanding supercapacitors based on nano-hybrid materials with interfacial conjugation

https://doi.org/10.1016/j.pnsc.2013.04.001Get rights and content
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Abstract

The recent fast development of supercapacitors, also known scientifically as electrochemical capacitors, has benefited significantly from synthesis, characterisations and electrochemistry of nanomaterials. Herein, the principle of supercapacitors is explained in terms of performance characteristics and charge storage mechanisms, i.e. double layer (or interfacial) capacitance and pseudo-capacitance. The semiconductor band model is applied to qualitatively account for the pseudo-capacitance in association with rectangular cyclic voltammograms (CVs) and linear galvanostatic charging and discharging plots (GCDs), aiming to differentiate supercapacitors from rechargeable batteries. The invalidity of using peak shaped CVs and non-linear GCDs for capacitance measurement is highlighted. A selective review is given to the nano-hybrid materials between carbon nanotubes and redox active materials such as electronically conducting polymers and transition metal oxides. A new concept, “interfacial conjugation”, is introduced to reflect the capacitance enhancement resulting from ππ stacking interactions at the interface between two materials with highly conjugated chemical bonds. The prospects of carbon nanotubes and graphenes for supercapacitor applications are briefly compared and discussed. Hopefully, this article can help readers to understand supercapacitors and nano-hybrid materials so that further developments in materials design and synthesis, and device engineering can be more efficient and objective.

Keywords

Supercapacitors
Carbon nanotubes
Graphenes
Electronically conducting polymers
Transition metal oxides
Interfacial conjugation

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George Zheng Chen (http://www.nottingham.ac.uk/~enzgzc), FRSC, FRSA, FIMMM, is professor of University of Nottingham. He obtained his Ph.D. degree from University of London (supervised by Prof. W. John Albery in Imperial College) in Physical Chemistry in 1992, and worked previously in Universities of Cambridge, Leeds and Oxford, and Wuhan and Jiangxi (now Nanchang) Universities. His research aims at electrochemical and liquid salts innovations for materials, energy and environment, producing 18 patents (including the Fray-Farthing-Chen Cambridge Process), 60 Ph.D. and M.Sc. theses, 154 articles in peer reviewed journals and books, and over 270 invited and contributed presentations at conferences and seminars.

Peer review under responsibility of Chinese Materials Research Society.

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