Parallel oxygen and chlorine evolution on Ru1−xNixO2−y nanostructured electrodes

Nanocrystalline materials with chemical composition corresponding to formula Ru_1−xNi_xO_2−y (0.02 < x < 0.30) were prepared by sol-gel approach. Substitution of Ru by Ni has a minor effect on the structural characteristics extractable from X-ray diffraction patterns. The electrocatalytic behavior of Ru_1−xNi_xO_2−y with respect to parallel oxygen (oxygen evolution reaction, OER) and chlorine (chlorine evolution reaction, CER) evolution in acidic media was studied by voltammetry combined with differential electrochemical mass spectrometry (DEMS). The DEMS data indicate a significant decrease of the over-voltage for chlorine evolution with respect to that of pure RuO₂. The oxygen evolution is slightly hindered. The increasing Ni content affects the electrode material activity and selectivity. The overall material's activity increases with increasing Ni content. The activity of the Ru-Ni-O oxides towards Cl₂ evolution shows a distinguished maximum for material containing 10% of Ni. Further increase of Ni content results in suppression of Cl₂ evolution in favor of O₂ evolution. A model reflecting the cation-cation interactions resulting from Ni-doping is proposed to explain the observed trends in electrocatalytic behavior.