This work explores the opportunity to reduce the cost and increase the stability of RuO₂-based electrocatalyst for oxygen evolution reaction by coating ternary oxide RuO₂-Sb₂O₅-SnO₂ on chemically stable titanium support. An active and stable type of Ti/RuO₂-Sb₂O₅-SnO₂ dimensionally stable anodes (DSA) was studied with different mole ratios of ruthenium prepared by using thermal deposition method. The metal oxides coating layer was maintained around 15 g m^-2. In this ternary oxide coating, RuO₂ serves as the catalyst, SnO₂ as the dispersing agent, and Sb₂O₅ as the dopant. The morphology by SEM showed that the compact and uniform surface morphology that indicates a favorable dispersion of species of 10%, 20% and 30% ruthenium samples. Further increase of ruthenium content, surface...[ Read more ]

This work explores the opportunity to reduce the cost and increase the stability of RuO₂-based electrocatalyst for oxygen evolution reaction by coating ternary oxide RuO₂-Sb₂O₅-SnO₂ on chemically stable titanium support. An active and stable type of Ti/RuO₂-Sb₂O₅-SnO₂ dimensionally stable anodes (DSA) was studied with different mole ratios of ruthenium prepared by using thermal deposition method. The metal oxides coating layer was maintained around 15 g m^-2. In this ternary oxide coating, RuO₂ serves as the catalyst, SnO₂ as the dispersing agent, and Sb₂O₅ as the dopant. The morphology by SEM showed that the compact and uniform surface morphology that indicates a favorable dispersion of species of 10%, 20% and 30% ruthenium samples. Further increase of ruthenium content, surface structure with more agglomerated particles of RuO₂ and the coating surface becomes less compact. The microstructure by XRD indicates that 10%, 20% and 30% ruthenium samples well intermix with Sb₂O₅, when ruthenium content exceeded 50% in the active coating layer, new and noticeable peaks corresponding to ruthenium oxide appear.

Effects of ruthenium content on Ti/RuO₂-Sb₂O₅-SnO₂ anodes in terms of both catalyst activity and the catalyst corrosion for oxygen evolution reaction were investigated. The electrochemical characterization of these electrodes has been performed in acid medium, and the reversibility, electrochemical porosity (related to voltammetric charge), kinetic parameters (related to Tafel measurements) and electrochemical resistance (related to electrochemical impedance spectroscopy) have been established. The best activity performances were achieved by 75% nominal ruthenium content. The value of q_aq_c^-1 was approximately equal to 1, the porosity was 35.5%, the potential at 1 mA cm^-2 was 1.426 V, which shows better electroactivity than pure RuO₂. Moreover, the accelerated service lifetimes of the DSA could reach up to 429.3 hours in 3 M H₂SO₄ solution under a current density of 500 mA cm^-2 at 25℃, which is equivalent to more than 5.8 years for normal electroflotation at 25℃. The electrode service lifetime for high temperature condition test showed that this electrode with 30% ruthenium give an average accelerated service lifetime as high as 167.3 hours at 70℃, which is estimated to be over 2.3 years working at 70℃ under normal electroflotation conditions.

These results revealed overall good catalytic efficiency which could be explained by the fact that Ti/RuO₂-Sb₂O₅-SnO₂ electrode has a) better electronic transport inside the coating due to small crystallinity and particle size (electronic factor); b) higher electrode charge (morphological effects); c) low Tafel slope (SnO₂ as an assisting reagent can efficiently remove adsorbed hydroxyl species and increase the utilization ratio of the active element.); d) good conductivity (SnO₂ is a good semiconductor with high resistivity, and it can be further improved by incorporating antimony); and e) longer operational lifetime (Sb₂O₅ as a dopant can well intermixed with RuO₂ and effectively avoid RuO₄ which can be dissolved in electrolyte).