Electrochemical oxidation of salicylic acid on the nanostructured electrodes based on nickel with additionally precipitated platinum

Abstract

We studied the electrochemical process of salicylic acid oxidation in acidic solutions on the nanostructured anodes prepared on the basis of nickel with additionally precipitated platinum. The investigation was carried out by means of linear and cyclic voltammetry methods in combination with quantum chemical calculations. The results of voltammetry study showed that clearly expressed current maxima were observed in the range of 0.43 V to 1.15 V in the anode sections of the voltammograms, in contrast to the background electrolyte. The oxidation potentials of the depolarizer almost coincided with those typical of a smooth platinum electrode, but the current density was 1.8 times higher on the electrode under study. Based on the analysis of voltammetric curves, the effective rate constants of heterogeneous charge transfer, activation energy and diffusion coefficient were calculated. The calculation of the thermodynamic parameters of the intermediates of salicylic acid electrooxidation showed that the heat of formation of 2,3-dihydroxybenzoic acid is higher than that of 2,5-dihydroxybenzoic acid, which indicates a higher stability of the latter. Analysis of the calculated thermodynamic characteristics of each stage of salicylic acid electrochemical oxidation showed that the process is endothermic, occurs with an increase in entropy and the Gibbs energy decreases. The rate of the overall process is determined by the rate of the first stage.