Improvement of chlorine evolution stability and activity of a RuO2–TiO2/IrO2–Ta2O5 electrode with low iridium content through an alternate coating and thermal decomposition method

Abstract

The electrochemical chlorine evolution reaction (CER) is an important electrochemical reaction for industrial applications, but it has serious problems, such as the short service life and low electrolytic efficiency in the extremely dilute chlorine-containing solution. In this paper, a RuO₂–TiO₂/IrO₂–Ta₂O₅ (RuTi/IrTa) electrode was prepared via a thermal decomposition method involving alternate coating with precursor solutions with two active components, which significantly improved the service lifetime and CER selectivity of electrode materials with low Ir content. The experimental results indicate that the accelerated lifetime (AL) of the RuTi/HC–IrTa electrode with an Ir loading of 374 μg cm⁻² can reach 602 h. Although the Ir loading of the HC–IrTa electrode (680 μg cm⁻²) is about twice that of the RuTi/HC–IrTa electrode, the AL of the HC–IrTa electrode is only 245 h, and the AL of the RuTi electrode (Ru loading: 180 μg cm⁻²) is only 5 h. If the precursor solutions of HC–IrTa and RuTi electrodes are simply mixed, the AL of the obtained RuTi–HC–IrTa electrode is only 41 h. This suggests that the increase in AL does in fact originate from changing the coating method, rather than simply the use of multiple active components. In addition, the SEM results indicate that the increase of the AL of RuTi/HC–IrTa is due to the change of the corrosion mechanism from pitting corrosion to surface corrosion of active components. Moreover, the CER selectivity of the RuTi/IrTa electrode has also been improved. This may be due to the change in the electronic structure, which is demonstrated through XPS characterization. The RuTi/IrTa electrode has a high electrolysis efficiency in the electrolysis of low-chlorine-concentration solutions. In the preparation of electrochemical disinfection technologies (EDTs), such as acidic electrolyzed water (AEW), more available chlorine content (ACC) can be obtained.