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 p-p interaction. The electrical conductivity of SAC-RGO was found to be $551 S m À1 . The capacitive performance of SAC-RGO was recorded using a three electrode set up with 1 (M) aqueous H 2 SO 4 as the electrolyte. The -SO 3 H 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 À1 at a current density of 1.2 A g À1 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 À1 at a power density of $980 W kg À1 . 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.

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

“…5,7,8 Carbonaceous materials like thermally reduced graphene oxide (GO), hydrothermally reduced GO, carbon nanotubes or activated carbon are well established negative electrode materials with perfect EDLC nature. 10 The advantage of using surface treated RGO as compared to the metal oxides is its high electrical conductivity. Graphene-based composite materials are the perfect choice that can provide the combination of faradaic and non-faradaic charge storage mechanisms during charge-discharge cycles.…”

“…1,9 Generally, materials with pseudo-nature are used as positive electrode materials. 1,2,7,[10][11][12][13] The surface modication also prevents the restacking of graphene layers and increases the effective surface area providing good ionic exchange with the electrolyte. 1,2,9 Furthermore, different covalent and non-covalent surface modications of reduced GO (RGO) can provide pseudocapacitance along with EDLC.…”

“…Graphene-based composite materials are the perfect choice that can provide the combination of faradaic and non-faradaic charge storage mechanisms during charge-discharge cycles. 10,13 Among the few materials with single atomic sheets, graphene is very useful for fundamental as well as application oriented research due to its remarkable mechanical, electrical and optical properties. 10 The advantage of using surface treated RGO as compared to the metal oxides is its high electrical conductivity.…”

“…10 The advantage of using surface treated RGO as compared to the metal oxides is its high electrical conductivity. 10,12,13 The presence of polar organic groups, including carboxylic acid, epoxy, phenol, and aldehyde functional groups, makes GO a poor conductor of electricity. 10,13 Among the few materials with single atomic sheets, graphene is very useful for fundamental as well as application oriented research due to its remarkable mechanical, electrical and optical properties.…”

“…14 Shao et al and Gilje et al have reported a two-step method: at rst, pre-applying GO dispersions directly onto the electrode followed by the reduction of GO in the presence of electrolytes. 10 The SAC-RGO was prepared by non-covalent functionalization of GO followed by reduction using hydrazine monohydrate. 18,19 Hilder and his co-workers have demonstrated simultaneous anodic electro-deposition and reduction of GO rather than the post-reduction of pre-coated electrodes.…”