Graphene oxide functionalized with phosphoramide as an effective and reliable electrode for supercapacitors with high-performance

Abstract Chlorine-doped graphene oxide (Cl-GO) was synthesized and then functionalized with phosphoramide bis (5-amino-1,3,4-thiadiazol-2-yl) phenylphosphonotrithioate (L). To functionalize Cl-GO with L (L-GO), the mixture of L in chloroform and triethylamine was introduced gradually to dispersed Cl-GO and refluxed. GO, Cl-GO, and L-GO were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and energy dispersive x-ray spectroscopy (EDX) characterization techniques. The cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) were used to identify the electrochemical characteristics of Cl-GO and L-GO in a 3.0 M KOH solution. The specific capacitance of L-GO (206.8 Fg ⁻¹) is more than that of Cl-GO (166.3 Fg ⁻¹) at a current density of 1 A g ⁻¹, according to the galvanostatic charge/discharge analysis. The L-GO with 1.5 mg cm⁻² mass loading presents an elevated capacitance of 225.1 mF cm ⁻² at 50 mA cm ⁻², retaining 72.6% of its capacitance from 1 to 50 mA cm⁻². The incorporation of massive L ligand into Cl-GO prevents graphene sheet aggregation and enhances electrolyte–electrode accessibility. Besides, incorporating ligand L into the graphene oxide structure increases the surface area that is accessible to ions and electron mobility ensuring impressive capacitive performance. Compared to Cl-GO, the L-GO electrode exhibits lower Rct amounts and less resistance to ion diffusion which effectively shows decreased internal resistance because of high electrical conductivity originating from π-donor groups of phosphoramide in L-GO, signifying a superior capacitive process.