The effect of ruthenium content on the stability and activity of Ti/RuO₂-Sb₂O₅-SnO₂ for oxygen evolution

The effects of ruthenium content on Ti/RuO₂-Sb₂O₅-SnO₂ anodes are investigated in terms of catalytic activity and stability for oxygen evolution. The best electrochemical stability appears at nominal Ru content around 30%, giving average accelerated lives of 419 and 165 h at 25 and 70 °C, respectively, under the current density of 500 mA cm⁻² in 3 M H₂SO₄ solution. These values are respectively ~8 and >22 times longer than any types of RuO₂-based electrodes reported previously. The electrocatalytic activity of Ti/RuO₂-Sb₂O₅-SnO₂ anodes is found to increase with nominal Ru content approaching 75%. The physicochemical and electrochemical analyses reveal that the homogeneous intermixture of RuO₂, SnO₂ and Sb₂O₅ with a smooth and compact surface decreases the dissolution rate of RuO₂, leading to a significant improvement on the electrode service life. Despite the numerous pores and cracks found in the coating, Ti/RuO₂-Sb₂O₅-SnO₂ anode with a nominal Ru content of 75% exhibits better electrocatalytic performance for O₂ evolution, which is attributed to more active RuO₂ sites exposed to electrolyte. Therefore, the existence of the optimal Ru content for Ti/RuO₂-Sb₂O₅-SnO₂ is the balanced effect between electrochemical stability and activity for O₂ evolution, as well as cost for specific applications.