Chlorine Evolution and Reduction Processes at Oriented Single‐Crystal RuO2 Electrodes

RuO 2 single‐crystal electrodes have been used to study the mechanism of the chlorine evolution/reduction reactions. RuO 2 (110) and (101) surfaces show the same anodic Tafel slopes equal to 40 mV/decade. Significant differences in the electrocatalytic behavior of these two surfaces were found for the chlorine reduction reactions. Two cathodic voltammetric peaks at E = 780 and E = 220 mV vs. SCE reference were observed for the RuO 2 (110) electrodes. The peak at E = 780 mV is completely suppressed in case of the RuO 2 (101) electrodes. It is suggested that the natural oxygen sites that are available only on the ideal (110) surfaces provide active centers for the formation of surface O . Cl + groups that are intermediates in the Krishtalik mechanisms. The cathodic LSV peak at E = 780 mV observed only for the RuO 2 (110) surfaces indicates, then, the reaction path with chloronium intermediates. The influence of the surface ruthenium oxide rearrangement processes on catalytic activity of the electrode and possible changes in the reaction mechanism are discussed in detail.