Estudo das propriedades superficiais e eletrocatalíticas dos eletrodos de óxidos de Ru + Ti + Ce + Nb

Abstract

In this work, oxide electrodes with nominal composition Ti/[Ru(o,3)Ti(o,6)Ce(o,1-X)]02Nb205(X) were prepared by thermal decomposition of chloride precursor mixture Solutions. The composition effects on the superficial and electrocatalytic properties were investigated. The oxides were characterized: ex situ by XRD and in situ by determining the open circuit potential (Eoc), the voltammetric curve and the voltammetric charge, the double-layer capacitance and the roughness factor. Except the Eoc, all parameters varied with the electrode composition. The presence of CeCh increases the electrochemically active area, but makes the coatings less stable when submitted to continuous potential cycles, due to cathodic dissolution of this oxide. This instability was eliminated by adding Nb2Os. Activity, stability and kinetic aspects of the oxygen and chlorine evolution reactions (OER and C1ER respectively), used as model reactions, were investigated by determining Tafel plots, reaction orders with respect to H+ (OER) and Cf and H+ (C1ER). The OER was shown to be dependent on composition and applied overpotential, contrary to the C1ER, which showed to be independent on these parameters. The maximum of activity, for both OER and C1ER, was observed at the same composition and it was attributed to both morfological and electronical effects. The corrosion results showed that the deactivation time has a strong dependence on the NH^Os content in the film. CeO2 creates a more fragile and porous structure; nevertheless Nb2Ü5 stabilized the film. Therefore the deactivation of these electrodes materiais is due mainly to passivation of the titanium support, increasing the TÍO2 interlayer.