Effects of sodium hydroxide on the yield and electrochemical performance of sulfonated poly(ether-ether-ketone) functionalized graphene

Tapas Kuila; Partha Khanra; Nam Hoon Kim; Jae Kyoo Lim; Joong Hee Lee

doi:10.1039/C3TA11014A

Effects of sodium hydroxide on the yield and electrochemical performance of sulfonated poly(ether-ether-ketone) functionalized graphene†

Tapas Kuila,^ab Partha Khanra,^a Nam Hoon Kim,^c Jae Kyoo Lim^d and Joong Hee Lee*^ac

* Corresponding authors

^a WCU Program, Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk, Republic of Korea
E-mail: jhl@jbnu.ac.kr
Fax: +82 63 270 2341
Tel: +82 63 270 2342

^b Surface Engineering & Tribology Division, CSIR-Central Mechanical Engineering Research Institute, Council of Scientific & Industrial Research (CSIR), Mahatma Gandhi Avenue, Durgapur-713209, India
Fax: +91-343-2548204
Tel: +919474729574

^c Department of Hydrogen and Fuel Cell Engineering, Chonbuk National University, Jeonju, Jeonbuk, Republic of Korea
Fax: +82 63 270 2341
Tel: +82 63 270 2342

^d Department of mechanical Design Engineering, Chonbuk National University, Jeonju, Jeonbuk, Republic of Korea
Fax: +82 63 270 2321
Tel: +82 63 270 2321

Abstract

An environmentally friendly method for the one-step electrochemical synthesis of water dispersible graphene directly from graphite is reported. Sulfonated poly(ether-ether-ketone) (SPEEK) dissolved in deionised water was used as an electrolyte and a surface modifying agent for graphene. The effects of sodium hydroxide (NaOH) on the production yield and electrochemical performance of graphene were investigated in detail. The production yield of few-layer graphene increased to above 40%, as compared to the 6% in the absence of NaOH. Fourier transform infrared and X-ray photoelectron spectroscopy (XPS) analyses suggested that the oxygen functionalities (hydroxyl and carboxyl) generated during the electrochemical exfoliation of graphite in the absence of NaOH were decreased significantly during the electrolysis experiment in an alkaline solution of SPEEK. This is attributed to the NaOH induced reduction of oxygen functionalities present on the surface of graphene sheets. XPS elemental analysis also confirmed the removal of oxygen functionalities in an alkaline medium during the graphite exfoliation experiment. Transmission electron microscopy and atomic force microscopy analyses confirmed the formation of single layer functionalized graphene. A charge–discharge experiment showed that the specific capacitance of the as-prepared graphene in the absence of NaOH was 18 F g⁻¹ at a current density of 2.2 A g⁻¹. In contrast, the specific capacitance was increased to 244 F g⁻¹ for graphene prepared under alkaline condition indicating its suitability as an energy storage electrode material. The high electrochemical performance may be due to the large surface area of graphene (433 m² g⁻¹) prepared under alkaline condition as observed by the Brunauer–Emmett–Teller surface area analysis.

Journal of Materials Chemistry A

Effects of sodium hydroxide on the yield and electrochemical performance of sulfonated poly(ether-ether-ketone) functionalized graphene†

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Effects of sodium hydroxide on the yield and electrochemical performance of sulfonated poly(ether-ether-ketone) functionalized graphene

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