Fabrication of IrOx immobilized glassy carbon surface for attaining electrocatalytic ascorbic acid oxidation reactions

Abstract

The development of an efficient electrocatalyst for the direct oxidation of ascorbic acid (AA) has gained considerable interest since AA may be applied as an environment-friendly alternative renewable biofuel in fuel cells. In the present work, the electrocatalytic oxidation of AA was implemented at IrOx immobilized glassy carbon electrode (GC-IrOx) in an acidic medium. Prior to use, the physical properties of GC-IrOx surface were investigated by means of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The XPS analysis revealed that a film of IrOx formed on the GC surface while it was cycled between 0 and 1.0 V vs Ag/AgCl (sat. KCl) reference electrode in Ir2O3 colloidal solution. The voltammetric investigations of AA oxidation at the GC-IrOx electrode revealed 4-folds higher current compared to a pristine GC electrode suggesting an excellent electrocatalytic performance. The Ir(III)/Ir(IV) redox couple is assigned for catalyzing the reaction. It was found that AA oxidation followed first order kinetics on the GC-IrOx electrode surface. The heterogeneous electron transfer (ET) kinetic study unveiled that AA oxidation reaction followed stepwise mechanism at potentials below 0.38 V and concerted mechanism above this potential with respect to a Ag/AgCl (sat. KCl) reference electrode. In this study, the standard rate constant (ko) pertaining to AA oxidation was evaluated as 7.25 × 10−4 cm s − 1. The GC-IrOx electrode exhibited reasonably excellent stability, which mounts the probability of its application as an anode in the AA fuel cells.