Sources of Oxygen Produced in the Chlorate Process Utilizing Dimensionally Stable Anode (DSA) Electrodes Doped by Sn and Sb

Identifying the sources of oxygen in the chlorate process is challenging due to the complex set of chemical and electrochemical reactions involved. Here, two types of electrodes have been investigatedTi_0.7Ru_0.3O_x, and electrodes with aimed composition Ti_0.34Ru_0.3Sn_0.3Sb_0.06O_x, both compared with platinum anodes. The cell oxygen off-gas was analyzed employing mass spectrometry together with ex situ UV–vis spectroscopy to quantify the kinetic rate constants. Noteworthy is that the respective rates of oxygen formation from anodic and chemical reactions in the presence of hypochlorite are of the same magnitude. The addition of Sn and Sb doubled the surface area of the electrodes and decreased oxygen production when electrodes were used for the first time. However, rate constants for total oxygen production with reused electrodes follow the trend: homogeneous hypochlorite decomposition < TiRu < TiRuSnSb to the highest value obtained by Pt. The same trend is noticed for rate constants concerning the hypochlorite decomposition.