LAUSR

Abstract Evidence to what it is identified in the literature as “active chlorine” in indirect oxidation processes occurring on Ti/ZrO 2 -RuO 2 -Sb 2 O 3 anodes is provided in this study. To discriminate such behavior, different catalysts are prepared using the Pechini method varying ZrO 2 content, at different Zr/Ru molar ratios: 1, 0.5 and 0.3. The characterization of the materials using X-ray photoelectron spectroscopy (XPS) reveals that no solid solution (Ru-Zr) or any doping that affects the crystalline phase of Zr are obtained, while Sb 2 O 3 was surface-segregated from the bulk to the anode surface affecting the outmost 3–5 nm surface layers. There are enormous impacts on the catalytic activity and adsorption properties of the structures as ZrO 2 content is increased. The presence of ZrO 2 and Sb 2 O 3 shrink the number of favorable oxygen adsorption sites in Ti/ZrO 2 -RuO 2 -Sb 2 O 3 catalysts, whence the adsorption energies for oxygen-metal interactions became lower than for Ti/RuO 2 . Differential electrochemical mass spectroscopy (DEMS) and electrochemical experiments qualitatively indicate that a lower amount of ZrO 2 in the ternary electrode induce a better catalysis towards the oxygen evolution reaction (OER, O 2 production), while the ionic currents for C l O − and H C l O species drop. This behavior suggests that chloride oxidation needs to encompass the mitigation of the OER as the percentage of ZrO 2 is increased in the anode. Active chlorine could stem from H C l O a d s species since it was produced in larger amounts than C l O a d s − according to the pH of the electrolyte, and in adequate levels to generate the degradation of organic compounds.