AgI/g-C3N4 nanocomposite as electrode material for supercapacitors: Comparative study for its efficiency in three different aqueous electrolytes

Abstract

Silver iodide/graphitic carbon nitride (AgI/g-C3N4) nanocomposite electrode is synthesized in a simple and fast method using sonication and co-precipitation techniques. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and fourier transform infrared (FT-IR) spectra techniques are used for morphology analysis, phase assessment and purification of synthesized composite electrodes. Specific capacity, cyclic stability, energy and power density, ion diffusion and faradic redox reaction for AgI/g-C3N4 composite electrode are studied in three different electrolytes i.e. H2SO4, KOH and Na2SO4 using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectrometry (EIS). Evaluation of GCD test of the AgI/g-C3N4 nanocomposite shows a specific capacity within a close range of 91, 98 and 99 C g–1 (219, 272 and 210 F g–1) for H2SO4, KOH and Na2SO4 electrolytes, respectively in current density of 1.5 A g–1. CV test on the proposed composite electrode illustrates the stable supercapacitor with perfect capacity retaining- H2SO4 (85%), KOH (84%) and Na2SO4 (87%) electrolytes - after 2000 cycles of charge and discharge in scan rate of 30 mV s–1. Besides that, energy density and power density of AgI/g-C3N4 composite electrode is assessed in the three electrolytes. The results depict higher energy and power densities in Na2SO4 (84 Wh.kg–1 and 1275 W.kg–1) than H2SO4 (69 Wh.kg–1 and 1137 W.kg–1) and the latter higher than that of KOH (65 Wh.kg–1 and 987 W.kg) electrolyte. The results for the hybrid nanocomposite electrode, is indicative of a promising electrochemical performance for the application of supercapacitors (SCs).