Electrochemical Behavior of p-nitroaniline at Silver/Chitosan/Graphite Electrodes Using Electrochemical Impedance Spectroscopy

Abstract

This study aims to study and compare the electrochemical properties of variously silver-based carbon paste electrodes towards the catalytic reduction of hazardous nitroaromatic compound p-nitroaniline (PNA). Silver-based carbon paste electrodes have been manufactured and electrochemically characterized by using Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to better define the electrochemical characteristics for their use as electrocatalytic sensors. The morphology and the distribution of silver on the electrode surface were evaluated by Scanning electron microscopy (SEM). The electro-active surface area of the as prepared electrodes was estimated to be 0.095, 0.06, 0.12 and 0.10 cm2 for electrode modified with silver via electrodeposition (CPE/Ag-Edp), impregnation (CPE/Ag-Imp), graphite electrode modified with silver nanoparticles (CPE/Ag-NPs) and graphite electrode modified graphite with silver adsorbed onto Chitosan (CS) (CPE/Ag-CS), respectively, using [Fe(CN)6]3−/4− as redox probe. EIS measurements of the silver-based graphite carbon electrodes were registered in 0.1 HCl solutions. The equivalent circuit might have been used to interpret the achieved impedance spectra which included one resistor in series with parallel circuit comprised of a capacitor and resistor (1R//C). The results show that the silver nanoparticles greatly reduced the electronic transfer resistance (Rct). The electrocatalytic activity of silver based electrodes for the reduction of PNA is discussed on the basis of the real electro-active surface area and particle size which results from varying modification modes.