Supercapacitors based on carbide-derived carbons synthesised using HCl and Cl 2 as reactants

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ORIGINAL PAPER

Supercapacitors based on carbide-derived carbons synthesised using HCl and Cl2 as reactants I. Tallo & T. Thomberg & H. Kurig & A. Jänes & K. Kontturi & E. Lust

Received: 25 June 2012 / Accepted: 13 August 2012 / Published online: 1 September 2012 # Springer-Verlag 2012

Abstract Micro- and mesoporous carbide-derived carbons (CDCs) were synthesised from TiC powder via a gas-phase reaction using HCl and Cl2 within the temperature range of 700–1,100 °C. Analysis of X-ray diffraction results show that TiC-CDCs consist mainly of graphitic crystallites. The firstorder Raman spectra showed the graphite-like absorption peaks at ~1,577 cm−1 and the disorder-induced peaks at ~1,338 cm−1. The low-temperature N2 sorption experiments were performed, and specific surface areas up to 1,214 and 1,544 m2 g−1 were obtained for TiC-CDC (HCl) synthesised at T0800 °C and TiC-CDC (Cl2) synthesised at T0900 °C, respectively. For the TiC-CDC powders synthesised, a bimodal pore size distribution has been established with the first maximum in the region up to 1.5 nm and the second maximum from 2 to 4 nm. The energy-related properties of supercapacitors based on 1 M (C2H5)3CH3NBF4 in acetonitrile and TiC-CDC (Cl2) and TiC-CDC (HCl) as electrode materials were also investigated by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge and constant power methods. The specific energy, calculated at U03.0 V, are maximal for TiCCDC (Cl2 800 °C) and TiC-CDC (HCl 900 °C), which are 43.1 and 31.1 Whkg−1, respectively. The specific power, calculated at cell potential U03.0 V, are maximal for TiC-CDC (Cl2 1,000 °C) and TiC-CDC (HCl 1,000 °C), which are 805.2 and 847.5 kWkg−1, respectively. The Ragone plots for CDCs prepared by using Cl2 or HCl are quite similar, and at high I. Tallo : T. Thomberg : H. Kurig : A. Jänes (*) : E. Lust Institute of Chemistry, University of Tartu, 14a Ravila Str., 50411 Tartu, Estonia e-mail: [email protected] K. Kontturi Department of Chemistry, Aalto University, P.O. Box 16100, 00076 Aalto, Finland

power loads, the TiC-CDC material synthesised using Cl2 at 900 °C, i.e. the material with optimal pore structure, delivers the highest power at constant energy. Keywords Titanium carbide . Hydrogen chloride . Chlorine . Carbide-derived carbon . Supercapacitor

Introduction Selective etching of carbides is an attractive technique for controlled synthesis of various carbon nanostructures at the atomic level [1–5]. Metal atoms can be extracted from carbides in different ways, most commonly by hightemperature chlorination using molecular chlorine and other halogens as well as halogen-containing gases or by thermal decomposition in a vacuum [6]. Development of carbidederived carbon (CDC) with unique micro- and mesoporous structures, narrow pore size distribution and the possibility to fine-tune pore sizes, confirmed previously [1–3, 7–9], has noticeably forced the development of applications requiring the CDC materials [2, 3, 7–12]. Previously, it was found that the micropore formation is strongl

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