Understanding the electro-catalytic oxidation mechanism of urea on nickel electrodes in alkaline medium

In this paper, the electrocatalytic behavior of urea oxidation on a nickel electrode in alkaline medium was investigated using various electrochemical techniques: cyclic voltammetry (CV), linear sweep voltammetry (LSV), and rotating disc electrode voltammetry (RDE). Possible mechanisms have been proposed on the basis of the cyclic voltammetry data. The urea oxidation current shows a strong dependence on the concentration of urea and potassium hydroxide that enables the experimental determination, by Tafel studies, of the kinetic reaction orders for the oxidation of urea. The Tafel studies show reaction orders of 0.3 and 2, with respect to urea and OH− concentrations, respectively. The diffusion coefficient of urea was found to be 0.85 × 10−5 cm2 s−1. The presence of a mixed-controlled process (diffusion and kinetics) was confirmed for the oxidation of urea.