Three-dimensional manganese dioxide-functionalized carbon nanotube electrodes for electrochemical supercapacitors
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Three-dimensional manganese dioxide (MnO2)-functionalized multiwalled carbon nanotube (MWCNT) electrodes have been produced by a simple and scalable thermal decomposition process. The electrodes are prepared by treating planar MWCNT sheets with manganese(II) nitrate (Mn(NO3)2) solution and annealing at low temperature (200–300 °C) and ambient pressure. The morphology, chemical composition, and structure of the resulting matrices have been investigated with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction. Supercapacitors assembled with three-dimensional electrodes exhibit a 14-fold increase in specific capacitance (C sp) in comparison to those containing pristine, two-dimensional MWCNT electrodes. C sp varies linearly with Mn(NO3)2 thermal decomposition temperature (from 100 to 61 F/g at 0.2 A/g), a trend that is discussed in the context of nitrate reaction chemistry and MWCNT structure. This efficient and promising approach allows for simultaneous enhancement of electrode–electrolyte contact area and incorporation of redox-based charge storage within electrochemical capacitors.
KeywordsElectrochemical capacitor Carbon nanotube Manganese dioxide Pseudocapacitance
This research was funded by the US Army Corps of Engineers, Engineer Research and Development Center, Section 219 Center Directed Research program. Dr. Sellers is supported by a postdoctoral fellowship administered by the Oak Ridge Institute for Science and Education (ORISE). Materials characterization was performed at the Center for Microanalysis of Materials at the Frederick Seitz Materials Research Laboratory, University of Illinois, which is partially supported by the US Department of Energy (DE-FG02-07ER46453 and DE-FG02-07ER46471) and by the National Science Foundation. We are grateful for the assistance of Dr. Rick Haasch, Niels Zussblatt, Dr. Julio Soares, and Robert Weber.
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