Performance comparison of several chlorine evolution electrodes

Chlorine evolution electrode materials mostly use DSA (Dimensionally Stable Anodes) type noble metal oxide electrodes, which have the characteristics of low chlorine evolution overpotential, high current efficiency and yield, and low energy consumption. In the electrolysis of low Cl-concentration water, the efficiency of producing active chlorine varies greatly with different electrode materials. 

Alexander Kraft et al. electrolyze water with different chlorine concentrations

Alexander Kraft et al. used Titanium Electrode (Ti/IrO₂), Ti/IrO₂-RuO₂, Pt, and Boron-Doped Diamond (Boron-Doped Diamond) as anode electrodes to electrolyze water with different Cl-concentrations. The current efficiency and active chlorine yield of DSA electrode Ti/IrO₂ and Ti/IrO₂-RuO₂ are significantly higher than Pt electrode and boron-doped diamond BDD electrode.

When the Cl- concentration is 180mg/L, the current efficiency of Ti/IrO₂ electrode is about 10%, while the current efficiency of Pt electrode and BDD electrode is less than 2%. Joonseon Jeong et al. studied the electrochemical characteristics of Ti/IrO₂, Ti/RuO₂, Ti/Pt-IrO₂, BDD, and Pt electrode materials in a low Cl^- concentration aqueous solution (1.7×10^-2 M NaCl) and found similar according to the conclusion, the order of the active chlorine yield of electrode materials is: Ti/IrO₂ ＞ Ti/RuO₂ ＞ Ti/Pt -IrO₂ ＞ BDD ＞ Pt, and the chlorine evolution activity of electrode materials (Ti/IrO₂ ＞ Ti/RuO₂ ＞ Ti/Pt -IrO₂> BDD> Pt) are consistent. 

When the electrode material is selected, the electrolysis process conditions such as the composition of the electrolyte solution, temperature, flow rate, pH value, current density, and conductivity are the main factors that affect the yield of electrolytic active products and current efficiency. In addition, in practical applications, it is also necessary to take into account economic costs. 

M. Stadelmann et al. studied the effects of various conditions on electrolytic active chlorine

M. Stadelmann et al. used Ti/IrO₂-Ta₂O₅ and Pt electrodes as anodes to study the effects of Cl^- concentration, temperature and current density on electrolytic active chlorine. The catalytic activity of Ti/IrO₂-Ta₂O₅ electrodes was significantly higher than that of Pt electrodes. For Ti/IrO₂-Ta₂O₅ electrode, the current efficiencies when the Cl^- concentration is 60mg/L and 1500mg/L are 4.6% and 41.5% respectively; the yield of active chlorine increases with the increase of temperature (10 ～ 60 ℃) , and is closely related to the concentration of Cl^-; when the concentration of Cl^- is 150mg/L, the best current density is 40mA · cm-2.