Role of nanocrystalline domain size on the electrochemical double-layer capacitance of high edge density carbon nanostru
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esearch Letter
Role of nanocrystalline domain size on the electrochemical double-layer capacitance of high edge density carbon nanostructures Stephen M. Ubnoske, Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA Akshay S. Raut, Charles B. Parker, and Jeffrey T. Glass, Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA Brian R. Stoner, Research Triangle Institute (RTI) International, Durham, North Carolina 27709, USA Address all correspondence to Stephen M. Ubnoske at [email protected] (Received 18 December 2014; accepted 10 March 2015)
Abstract Nanostructured carbon materials, especially activated carbon, carbon nanotubes, and graphene, have been widely studied for supercapacitor applications. To maximize the efficacy of these materials for electrochemical energy storage, a detailed understanding of the relationship between the nanostructure of these materials and their performance as supercapacitors is required. A fundamental structural parameter obtained from the Raman spectra of these materials, the in-plane correlation length or nanocrystalline domain size, is found to correlate with the electrochemical capacitance, regardless of other morphological features. This correlation for a common nanostructural characteristic is believed to be the first result of its kind to span several distinct nanostructured carbon morphologies, including graphene–carbon nanotubes hybrid materials, and may allow more effective nanoscale engineering of supercapacitor electrode materials.
Introduction Nanostructured carbon materials have been widely studied for applications in electrochemical energy storage, including activated carbon,[1–3] carbon nanotubes (CNTs),[4–7] and graphene.[8–11] Applications of such devices include hybrid structures in automotive energy storage,[12] flexible electronics,[13–15] and neural stimulation electrodes.[16] In order to optimize the performance of such devices, a clear understanding of the relationship between the physical properties of nanostructured carbon materials and electrochemical capacitance is required. As a nondestructive process, determination of nanocrystalline domain size using the Raman ID/IG ratio,[17–20] referred to interchangeably as graphitic cluster size or in-plane correlation length,[21] provides a facile and inexpensive method to engineer carbon nanostructures for energy storage applications. In this study, we present a relationship between this nanocrystalline domain size and the specific capacitance of various carbon nanostructures grown by plasma-enhanced chemical vapor deposition (PECVD) and measured by Raman spectroscopy. Previous works[22–26] have suggested a relationship between graphitic edge planes and specific capacitance for graphite, glassy carbon, highly ordered pyrolytic graphite, carbon nanofibers, multi-walled carbon nanotubes, and doped graphene. This work is believed to be the first to quantify the relationship between structural defects, largely co
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