Dataset of "Mechanistic aspects of the selectivity of RuO2 and Ru-Mn-O catalysts in parallel Chlorine and Oxygen Evolutions Reactions"

Mechanistic differences between oxygen evolution and chlorine evolution on Ru based oxide electrodes in acid media were assessed by operando soft X-ray absorption spectroscopy. O K edge spectra recorded under cyclic polarization in 0.1 M HClO4 containing variable concentrations of chlorides in energy dispersion mode were used to follow a potential dependence of the key intermediates of the oxygen evolution process as a function of the electrode potential and chloride concentration. In the absence of chlorides, the OER process is characterized by a formation of surface confined OOH at potentials preceding the onset of the bulk oxygen evolution. In the presence of chlorides, the spectral behavior reflects a change of the electrode selectivity towards chlorine evolution as shows a suppression of the absorption of the gaseous oxygen as well as intermediates of OER process. The observed behavior is compliant with the mechanism assuming the chlorine binding via surface confined oxygen atoms. The Ru-Mn-O phases which are selective for oxygen evolution even in the presence of chlorides show a different behavior. The sites involved in the OER retain their selectivity to OER even in the presence of chlorides. The actual mechanism of the OER changes slightly in the presence of chlorides. In the absence of chlorides, one observes accumulation of surface OOH groups only at potentials positive to the onset of the bulk oxygen evolution. In contrast to that, the presence of chlorides enables the formation of surface confined OOH at potentials negative to the OER onset. The onset of the actual oxygen evolution, on the other hand, leads to removal of the surface confined OOH suggesting the OER is controlled by the third electron transfer in the presence of chlorides.