Oxidation Mechanism of Oxalic Acid on Platinum, Glassy Carbon and Boron Doped Diamond Electrodes in Nitric Acid Medium

Abstract

In order to understand the electrochemical oxidation mechanism of oxalic acid on platinum, glassy carbon and boron doped diamond(BDD) electrodes in nitric acid medium, cyclic voltammetry and linear sweep voltammetry were used to carry out electrochemical tests. The effects of electrode potential, current density and nitric acid concentration on oxalic acid oxidation were studied, and the influence of nitric acid mainly comes from H+. On the Pt electrode, it is speculated that oxalic acid is not only electrooxidized, but also adsorbed ·OH reacts with adsorbed oxalic acid to produce CO2 and H2O. On the boron doped diamond electrode, indirect oxidation of ·OH is the main role of oxalic acid oxidation. The increase of nitric acid concentration reduces the amount of ·OH production, which leads to the decrease of oxalic acid oxidation rate. On the glassy carbon electrode, the diffusion coefficient of oxalic acid is 1.4×10-5 cm2/s measured by rotating disc electrode, the exchange current density of oxalic acid electrochemical oxidation obtained by Tafel extrapolation at 1.34-1.42 V is 5.8×10-6 A/cm2.

Keywords

• oxalic acid
• nitric acid
• boron doped diamond electrode
• cyclic voltammetry
• rotating disc electrode