Efeito da substituição de titânio por estanho no comportamento eletroquímico do sistema Ti/RuxN1-xO2, com N igual a Ti ou Sn.

Abstract

In order to investigate the influence of the titanium substitution for tin on the electrochemical properties of the electrodes, Ti/RuxNi.x02, with N equal to titanium or tin and 0 < x < 0,3, the same ones had been electrochemically characterized from the ex-situ (metalographics images) and in-situ techniques (cyclical voltametry) and its electrocatalitic properties from Tafel curves. The method for preparation of the electrodes was thermal decomposition and, isopropanol or HCI 1:1 (v/v) was used as solvent. The general objective was the preparation, characterization and electrocatalitic studies of new conducting oxide materials which will be applied in the separation process of oil/water through the electrochemical technology. It was also carried out, a study of the size of the generated chlorine gas bubbles in the surface of the electrodes, where the same ones had been analyzed in function of the applied potential and the composition of the electrodic material. The produced bubbles had been grouped in two sets of size in accordance with the results, 0,20mm, 0,25 and 0,40mm. The micrography presented adobe characteristic "cracked mud" for all the electrodes. The electrodes with 100% Ru02, presented smaller grains for the electrode synthecized from RuCl3 in isopropanol than with HCI 1:1 (v/v)). The cyclical voltamograms (NaCI 1.0 mol dm'3 pH 2) had presented characteristic bands of the Ru 7Ru pair. The electrodes had revealed steady, reversible and "banana" format with high load density, characteristics of this material. The great influence of solvent can be observed, as well as the use of tin it in the composition of the electrode. The Ti/RuxSni-x02 electrodes present an increase in the current value with the reduction in % mol of Ru02 and in the case of the electrodes with Ti/RuxTii_x02, or Ti/RuojTiojO? are what they present higher current, at equal constant potential of 1524 mV (RHE). The values of the ohmic drop are between 0,2 - 1,3 Q. The values of the Tafel coefficient are related with the composition of investigated oxides presenting an only Tafel coefficient, near 40mVdec"1 for the electrode of nominal composition Ti/RuxTii.x02 and 30mVdec"1 to Ti/RuxSni-x02. In study of the bubbles'size, it can be verified that: (1) the increase of the potential does not provoke change in the adsorption force of the bubbles. (2) oxide electrodes which contains titanium present greater adsorption of the bubbles making possible the coalescence occurrence and consequently its growth.