In situ preparation of a SAC-RGO@Ni electrode by electrochemical functionalization of reduced graphene oxide using sulfanilic acid azocromotrop and its application in asymmetric supercapacitors

Abstract

In situ electro-deposition, reduction and functionalization of graphene oxide (GO) with sulfanilic acid azocromotrop (SAC) were carried out through a facile one-step electrochemical method. Nickel foam was used as the anode during the electro-deposition and the aqueous solution of SAC along with GO was used as the electrolyte. The SAC modified reduced GO (RGO) was deposited on the nickel foam (SAC-RGO@Ni) and was directly used as the electrode for capacitive property analysis. The reduction and functionalization of GO were examined by Fourier transform infrared (FT-IR), Raman and X-ray photoelectron spectroscopy (XPS) techniques. The SAC-RGO@Ni provides a very high specific capacitance of ∼1090 F g⁻¹ due to the synergistic effect of double layer capacitance of RGO and the pseudocapacitance of –SO₃H functionalities of SAC. An asymmetric supercapacitor (ASC) cell was designed with SAC-RGO@Ni and thermally reduced GO (TRGO) as positive and negative electrodes, respectively. The ASC device exhibits a high effective capacitance of ∼495 F g⁻¹ at a current density of 10 A g⁻¹ and ∼93% of its total discharging time lies in-between 1.5 and 0.75 V. The ASC cell remains stable up to 10 000 charge–discharge cycles. Furthermore, the SAC-RGO@Ni-based ASC device can provide a very high energy density of ∼88.9 W h kg⁻¹ and a large power density of 16 500 W kg⁻¹ ensuring its applicability in high power consumption devices.