Synthesis and characterisation of nanoporous carbide-derived carbon by chlorination of vanadium carbide Alar Ja ¨nes * , Thomas Thomberg, Enn Lust Institute of Physical Chemistry, University of Tartu, 2 Jakobi Street, 51014 Tartu, Estonia Received 21 August 2007; accepted 22 September 2007 Available online 29 September 2007 Abstract Nanoporous carbide-derived carbon (CDC) was synthesised from vanadium carbide (VC) powder via gas phase chlorination in the temperature range from 500 to 1100 °C. The XRD analysis of nanoporous carbon powder samples was carried out to investigate the structural changes (graphitisation) of nanoporous carbons synthesised. The first-order Raman spectra showed the absorption peak at 1582 cm 1 and the disorder-induced (D) peak at 1345 cm 1 . The low-temperature N 2 adsorption experiments were performed and a specific surface area up to 1305 m 2 g 1 and total pore volume up to 0.66 cm 3 g 1 were obtained. Ó 2007 Elsevier Ltd. All rights reserved. 1. Introduction Systematical analysis of results [1–12] shows that the parameters and nanoporous structure of the carbon mate- rial depend noticeably on the chlorination temperature and the starting metal carbide used. Previous studies show that the carbon structure produced depends especially on the origin and uniformity of the precursor carbide selected as a raw material [1–13]. The unique nanoporous structure of carbide-derived carbon (CDC) with the narrow pore size distribution and possibility to fine-tune the pore size, con- firmed recently [1,2], has noticeably forced the development of applications requiring the nanoporous carbon materials [3–8]. Previous studies were carried out with different pre- cursor carbides (a-SiC, TiC, Ti 3 SiC 2 ,B 4 C, NbC, ZrC, Mo 2 C and others) [1–3,9–16] and show that the half-width of prevailing nanopores increases in the order: C(a- SiC) < C(TiC) < C(B 4 C) < C(Mo 2 C). Systematical analysis of capacitance data in non-aqueous electrolytes and at the gas phase characteristics shows that the capacitance of pos- itively charged nanoporous carbon electrode (C + ) is usu- ally somewhat higher than that of negatively charged (C  ) electrode [4–6]. However, for the higher total capaci- tance (power and energy density) values of the electrical double-layer capacitors C + and C  should be equal, which is possible for materials having better adsorption capaci- tance values for negatively charged electrode. It was dem- onstrated that for CDC with half-pore width lower than 0.76 nm there are noticeable capacitive limitations in non- aqueous electrolyte caused by the mismatch of solvated ion radii and porous structure characteristics [4–6]. It should be noted that the normalised series capacitance val- ues (electrode capacitance divided by the specific surface area) increase strongly with the decrease of pore radius of the CDC, prepared from the binary TiC carbide at lower synthesis temperatures [14]. Different dependence of CDC electrochemical characteristics can be explained by the var- ious shape of sub-nanopores in the nano(meso)porous car- bons, synthesised at different temperatures. However, this problem needs future more detailed studies. Based on the crystallographic characteristics of binary metal carbides, VC seems to be a very interesting raw mate- rial for synthesis of C(VC) with medium pore diameter higher than 1 nm. This paper describes a parametric study 0008-6223/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2007.09.041 * Corresponding author. Fax: +372 737 5160. E-mail address: alar.janes@ut.ee (A. Ja ¨nes). www.elsevier.com/locate/carbon Available online at www.sciencedirect.com Carbon 45 (2007) 2717–2722