Capacitance characteristics of carbon-based electrochemical capacitors exposed to heteropolytungstic acid electrolyte. (20th August 2018)

• Record Type: Journal Article
• Authors: Skunik-Nuckowska, Magdalena; Dyjak, Sławomir; Grzejszczyk, Katarzyna; Wisińska, Natalia H.; Béguin, François; Kulesza, Pawel J.
• Is Part Of: Electrochimica acta. Volume 282(2018)
• Page Start: 533
• Page End: 543
• Publication Date: 2018-08-20
• Subjects: Electrochemical capacitor -- Keggin-type heteropolytungstic acid -- Double-layer capacitance -- Aqueous electrolyte; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2018.06.070
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: A Keggin-type heteropolytungstic acid, H3 PW12 O40, is evaluated as new high ionic conductivity aqueous electrolyte of potential interest for electrochemical capacitors, with enhanced safety and low environmental concern. For the performance evaluation, two types of electrode materials have been selected, i.e. mesoporous multi-walled carbon nanotubes and microporous activated carbons. To address the influence of changes in the porous structure and surface properties on capacitors performance, the materials have been subjected to additional oxidation treatment under liquid or gas phase conditions. The electrochemical parameters of two-electrode cells were evaluated from a series of voltammetric, galvanostatic, constant power, and AC impedance measurements and compared with those obtained for conventional H2 SO4 electrolyte. It has been shown that due to the size of the heteropolytungstate anion (exceeding 1 nm), the selection of carbon electrode materials in terms of appropriate porous structure and wettability is a key factor in avoiding capacitance limitations. As a result, the specific capacitance, energy density as well as the rate capability of H3 PW12 O40 supported capacitors may approach the performance of conventional H2 SO4 -based systems. Furthermore, the potentiodynamic anodic polarization tests and post-mortem scanning electron microscopy analysis confirmed a higher corrosion resistance of 316 L type steel in the presence of H3 PW12 O40 solution, in comparison to the conventional H2 SO4 electrolyte. It enables stable capacitor performance upon utilization of low cost non-noble current collectors which was evaluated during galvanostatic cycling (13 000 cycles) and accelerated ageing by potentiostatic floating during 120 h. Highlights: Heteropolytungstic acid as promising electrolyte for aqueous supercapacitors. Porosity and wettability of carbon materials responsible for capacitance increase. Capacitance and rate capabilities approach the conventional H2 SO4 -type systems. Transpassivation of steel current collectors inhibited in presence of H3 PW12 O40 .