Surface electrochemical properties of Ti/(RuO2+ZrO2) electrodes

Mixtures of RuO2 + ZrO2 on a Ti support have been studied electrochemically by cyclic voltammetry in acidic solution. The most appropriate combination of precursors has been selected from RuCl3, Ru(NO3)(3), ZrCl4, ZrOCl2 and ZrO(NO3)(2). At 50 mol% RuO2, the coupling of the nitrates has produced the highest voltammetric charge. The effect of the calcination temperature has successively been studied. The voltammetric charge has turned out to be maximum around 350 degrees C. In order to be on the safe side as far as completion of thermal decomposition is concerned, the calcination temperature of 400 degrees C has been further adopted. A study of the effect of oxide loading has shown that for more than 8 mg cm(-2) of active oxide layer the surface charge does not increase any more. As the RuO2 content is varied over all the composition range, the surface charge shows a maximum at exactly 50 mol% RuO2, probably related to the smallest particle size. Finally, the surface response to cathodic treatments has shown that these electrodes are stable under hydrogen evolution from a chemical point of view, although marginal morphological changes of the active oxide layer are possible.