Electrooxidation of Ascorbic Acid on a Polyaniline-Deposited Nickel Electrode:  Surface Modification of a Non-Platinum Metal for an Electrooxidative Analysis

Abstract

The electrooxidation of ascorbic acid (H2A), which does not occur on a bare Ni electrode, has been shown to take place on a polyaniline (PANI)-coated Ni electrode in aqueous electrolytes of a wide pH range. The characteristic voltammetric peak of PANI in 0.1 M H2SO4 at 0.2 V vs SCE corresponding to the transformation of leucoemeraldine to emeraldine gradually diminishes with an increase in concentration of H2A as a result of adsorption. This peak disappears before the appearance of another peak corresponding to the oxidation of H2A at a concentration of 1 mM. The irreversible oxidation current of H2A exhibits a linear dependence on the concentration. The effect of adsorption of H2A on PANI has been shown to increase the voltammetric peak current. A study on the variation of the PANI thickness and its influence on the voltammetric oxidation of H2A has led to an optimum thickness of 1.6 microm. The oxidation currents on the porous PANI/Ni electrode have been found to be several times higher at lower potentials in comparison with the data of a Pt electrode. The reaction has also been studied by ac impedance spectroscopy. In alkaline electrolytes, the Nyquist impedance plot is characterized by two semicircles instead of a single semicircle in acidic electrolytes. Thus, Ni, which is a non-platinum metal, has been found to be useful, by surface modification with PANI, for electrooxidation of H2A. The data are reproducible in the electrolytes of a wide pH range, thus suggesting a good stability, reusability and a long life for the PANI/Ni electrodes.

Ascorbic Acid Oxidation at Nonmodified and Copper‐Modified Polyaniline and Poly‐ortho‐methoxyaniline Coated Electrodes

“…An optimal thickness of about 1 mm for both types of layers was found. This result is close to the reported optimal (in terms of overpotential) thickness of 1.6 mm found for PANI in the course of ascorbate oxidation in acid solution [11].…”

Electrocatalytic Properties of a Novel Poly‐1‐Naphthylamine‐Modified Electrode Using Ascorbic Acid as Molecule Probe

“…This fact clearly indicates that the catalytic oxidation of AA occurs in the bulk of the p-1-NAP film, rather than on the surface. Similar results were obtained with the electrooxidation of AA on the polyaniline and polyaniline-deposited nickel electrodes respectively [35,40].…”

“…The decrease in the currents observed at pH higher values may correspond to a decrease in the electrochemical activity of p-1-NAP [14]. The wide pH intervals where the electrode of p-1-NAP is active is a clear advantage respecting others that can be used only in neutral [32] or acidic conditions [35,36]. Thus, considering these results and that the second objective of this work is to study the p-1-NAP analytical application in food and pharmaceutical products, a pH 3 was used for the all experiments described below.…”

Electrocatalytic Activity and Electrochemical Impedance Spectroscopy of Poly(Aniline-Co-Ortho-Phenylenediamine) Modified Electrode on Ascorbic Acid

“…Voltametric studies of AA on bare electrode have not been very successful [3][4][5][6] . The main cause is the high over potential of AA besides the fouling effect of the oxidation products, poor reproducibility, low selectivity and poor sensitivity.…”