Abstract
Carbide-derived Carbon (CDC) has been demonstrated to be an excellent electrode material for electrochemical devices including supercapacitors due to its chemical and electrochemical stability, large specific surface area and controllable pore size and morphology. Currently, CDC is prepared from metal carbides by chlorination in a chlorine gas atmosphere at temperatures of 350°C or higher. In this paper, conversion using electrochemical methods is reported, which can be achieved by oxidizing vanadium carbides (VC or V2C) in aqueous solutions at room temperature and a mild electrode potential to prepare CDC thin film as electrode materials for “on-chip” supercapacitiors. It was found that VC and V2C can both be oxidized at a potential of about 0.4 V vs. Ag/AgCl or higher in neutral, acidic, or basic solutions. After the oxidation, vanadium is readily detected in the electrolyte solutions by ICP-MS (Inductively Coupled Plasma – Mass Spectrometry). The so-produced CDC thin film electrode (ca. 2.0 - 2.6 μm thick) has a porous morphology and bears specific double layer capacitance values as high as 0.026 F.cm−2 (or 130 F.cm−3) with some dependence on the oxidation potential, time, and electrolyte solutions.
Highlights
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We report, for the first time, an electrochemical oxidation of textured binary monolithic vanadium (IV) carbide (VC) and vanadium (II) carbide (V2C) thin films on either electrically conducting or insulating substrates
The system is configured with a residual-gas analyzer (RGA) which allows a measurement of the ratio of Ar to C2H2 as well as ensuring that nitrogen, oxygen and water vapor contents are sufficiently low so that they do not cause a problem leading to the formation of metal oxides and nitrides during the deposition and that the background gases are at consistent levels
Summary
Let us know how access to this document benefits you share your thoughts on our feedback form. Gogotsi and coauthors reported the electrochemical etching of MAX-phase carbides to produce CDC at room temperature using HF, HCl, or NaCl electrolyte solutions at potentials higher than 0.5 V vs Ag/AgCl, in HF, or 2.0 V, in HCl.[10]. Vanadium metal was readily oxidized and removed from the carbide crystal and dissolved in the electrolyte solutions when the electrode potential was ramped to be 0.4 V vs Ag/AgCl or higher. This oxidation can occur when the VC or V2C thin films were deposited on either a conductive substrate, such as glassy carbon, or on an insulating substrate, such as sapphire. It has been reported that the specific capacitance of CDC thin-film devices exceeds that of their bulk counterparts by a factor of 2 or greater.[11]
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