Effect of residual electrolyte on dispersion stability of graphene in aqueous solution
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ORIGINAL PAPER
Effect of residual electrolyte on dispersion stability of graphene in aqueous solution Hemraj Mahipati Yadav 1 & Sae Youn Lee 1 & Chan Hee Lee 1 & Jongdeok Park 1 & Jae-Joon Lee 1 Received: 17 June 2020 / Revised: 1 October 2020 / Accepted: 1 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The stability of graphene dispersions in water is of both scientific and technological significance. We studied the dispersion stability of electrochemically exfoliated graphene in an aqueous medium to minimize the strong aggregation tendency, within a short period, of graphene prepared in various electrolytes. This study focused on increasing the dispersion stability of graphene and finding the reason for its poor dispersion stability. The residual electrolyte trapped in the graphene layers was difficult to be removed from electrochemically exfoliated graphite and caused a significant aggregation. The stability and dispersion concentration can be improved by removing the trace amount of aqueous electrolyte. The aggregation mechanism of graphene in aqueous media is proposed and discussed in detail. Keywords Graphene dispersion . Electrolyte effect . Surface interface . Dispersion in water . Electrochemical exfoliation
Introduction Due to its outstanding electrical, mechanical, thermal, and optical properties, graphene has become a very popular candidate in a wide range of applications, such as chemical sensors, fieldeffect transistors, optoelectronics, and energy generation and energy storage devices [1–5]. Graphene, which is highly dispersible and highly stable and has good electrical conductivity properties, is required for many of these applications. Graphene prepared by Hummers’ method [6] shows very low electrical conductivity or insulating behavior owing to its existing oxygen-containing moieties, including epoxide, hydroxyl, carboxylic groups, carbonyl, phenol, lactone, and quinone [7–9]. Therefore, post-reduction is essential for enhancing the electrical conductivity of graphene oxide (GO). Heat treatment or Hemraj Mahipati Yadav and Sae Youn Lee contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10008-020-04835-4) contains supplementary material, which is available to authorized users. * Jae-Joon Lee [email protected] 1
Department of Energy and Materials Engineering, Research Center for Photoenergy Harvesting & Conversion Technology (phct), Dongguk University, Seoul 04620, Republic of Korea
other chemical reduction reactions have typically been performed to produce reduced GO (RGO) [10]. Prepared RGO displays significantly lower dispersion concentration and stability in organic solvent than GO. The aggregation of RGO in solvent is a main obstacle for the uniform coating of graphene by different methods, such as spray, dip, drop, spin, and Langmuir–Blodgett (LB). Therefore, it causes severe problems for the utilization of graphene in a wide range of applications [11, 12]. In addition, RGO di
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