Abstract
The physical and electrochemical properties of ternary oxides Ti0.7Ru0.3−xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types.
Highlights
Transition metal oxides are used for many electrochemical applications, such as gas sensors and chlorine or oxygen evolving electrodes [1]
We have studied the kinetic properties of ternary oxide coatings containing the standard 70 mol% TiO2 fraction together with a mixture of ruthenium and cobalt oxides
When comparing the two curves, it can be seen that the oxidation of the solution doped with cobalt peaked at a slightly higher temperature than the oxidation of the undoped coating solution (Tc increased from 338 ◦C to 341 ◦C)
Summary
Transition metal oxides are used for many electrochemical applications, such as gas sensors and chlorine or oxygen evolving electrodes [1]. One of the most commonly used transition metal oxide in catalytic electrode materials is ruthenium dioxide (RuO2). Coatings of the standard DSA® composition (30 mol% RuO2 and 70 mol% TiO2) combine a high stability with a high activity and a high selectivity toward chlorine evolution [4,5], and have been used as the primary catalyst in chlorine and chlorate production for over 40 years. Ruthenium dioxide has been doped with for example Ce [6], Sn [7], Co [8,9,10,11,12] or Ni [13] to improve the catalytic activity, enhance the selectivity and/or increase the stability of the coating.
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