Non-covalent functionalization of reduced graphene oxide using sulfanilic acid azocromotrop and its application as a supercapacitor electrode material

Abstract

Sulfanilic acid azocromotrop (SAC) modified reduced graphene oxide (SAC-RGO) was prepared by simple non-covalent functionalization of graphene oxide (GO) followed by post reduction using hydrazine monohydrate. Spectral analysis (Fourier transform infrared, Raman and X-ray photoelectron spectroscopy) revealed that successful modification had occurred of GO with SAC through π–π interaction. The electrical conductivity of SAC-RGO was found to be ∼551 S m⁻¹. The capacitive performance of SAC-RGO was recorded using a three electrode set up with 1 (M) aqueous H₂SO₄ as the electrolyte. The –SO₃H functionalities of SAC contributed pseudocapacitance as evidenced from the redox peaks (at ∼0.43 and 0.27 V) present in the cyclic voltammetric (CV) curves measured for SAC-RGO. The contribution of electrical double layer capacitance was evidenced from the near rectangular shaped CV curves and resulted in a high specific capacitance of 366 F g⁻¹ at a current density of 1.2 A g⁻¹ for SAC-RGO electrode. An asymmetric device (SAC-RGO//RGO) was designed with SAC-RGO as the positive electrode and RGO as the negative electrode. The device showed an energy density of ∼25.8 W h kg⁻¹ at a power density of ∼980 W kg⁻¹. The asymmetric device showed retention in specific capacitance of ∼72% after 5000 charge–discharge cycles. The Nyquist data of the device was fitted with Z-view and different components (solution resistance, charge-transfer resistance and Warburg elements) were calculated from the fitted curves.