Oxygen Evolution Reaction at Electrodes of Single Phase Ruthenium Oxides with Perovskite and Pyrochlore Structures

Single phase ruthenium oxides with perovskite (AT_1-xRu_xO₃ (A=Ca, Sr)) and pyrochlore structure (Bi₂Ru₂O₇, Pb₂Ru₂O_6.5) have been prepared reproducibly by solid state reaction methods and their electrocatalytic activities for oxygen evolution have been examined by Tafel plots. Tafel slopes vary from a low value of 42 mV/decade up to 222 mV/decade at room temperature. The high exchange current densities and high Tafel slopes compared with those obtained from the RuO₂ DSA electrode at the crystalline single phase metal oxide electrodes suggest that they are better electrocatalysts at low overpotentials. A favorable change in the Tafel slope for the oxygen evolution reaction occurs as the ruthenium content increases. Substitution of Ti for Ru in the perovskite solid solutions enhanced their chemical stability by losing marginal electrochemical activity.