(363c) The Electrocapacitive Properties of Organometallic Polymer/Multiwalled Carbon Nanotube Hybrids

Xianwen Mao, Demetra S. Achilleos, Fritz Simeon, Gregory C. Rutledge and T. Alan Hatton*

There is growing interest in adapting redox-active materials for supercapacitor applications, owing to expected synergistic effects when the capacitive charging of the electrochemical double layer can be combined with a redox (pseudocapacitive) reaction. When both charge storage mechanisms work in parallel, the overall capacitance of the composite electrode becomes the sum of the electrochemical double layer capacitance and the redox capacity. Various redox polymer electrodes have been developed for this application, but they generally suffer from limited chemical reversibility and lack long-term cycling stability in aqueous electrolyte solutions.

The redox responsiveness of hybrids comprised of organometallic polymers and multiwalled carbon nanotubes (MWCNT) makes it possible to develop supercapacitors with the desired redox capacity.  We have optimized the composition of the polymer/MWCNT hybrids to achieve enhanced performance and stability as electrochemical capacitors. In this paper, we report on the morphology and structure of the hybrids as investigated by transmission electron microscopy, scanning electron microscopy and nitrogen adsorption/desorption isotherms, and study the capacitive performance, rate capability and long-term cycling stability of the hybrids using cyclic voltammetry and galvanostatic charge/discharge techniques.  The charge-storage mechanism is examined based on the results of electrochemical impedance spectroscopy.