Electrosynthesis of perchlorate using neodymium-doped PbO 2 electrode: application of experimental design methodology for optimization of the effective parameters

Abstract

In recent decades, extensive research has been done on substrates (i.e., titanium and carbon) with lead dioxide coating to design a cheap anode in electrochemical systems instead of a platinized (Pt) electrode. Various factors can affect the structure and catalytic activity of lead dioxide coating. The most important of them are the type of substrate, how to prepare the substrate for the coating process and the types of lead dioxide additives. In this work, the effective factors in the preparation of the substrate were first investigated. Subsequently, the effect of neodymium as an additive on the catalytic activity of the electrode was studied. We prepared these electrodes and they were first evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectrometer, voltammetry and electrochemical impedance spectrometer (EIS). The results showed that the potential of water oxidation on the modified electrodes by neodymium was 2 V. Here, we used an electrochemical method to prepare perchlorate. Since the anode potential for perchlorate oxidation is near that for water oxidation, conventional electrodes can’t be used in the perchlorate electrosynthesis. To achieve high production yield in the preparation of perchlorate from chlorate, various parameters including pH, time, and current density were optimized by the Box-Behnken design of the experiment method. The optimal values for this process were obtained at pH = 11, temperature 40 °C and current density of 0.5 mA cm−2. The results at the optimal condition showed that the perchlorate production yield by modified electrodes was 80% in the 300 min. This value was only 60% for the unmodified electrode.