Design and properties of dimensionally stable anodes on Ebonex® substrate

Abstract

Ceramic materials consisting of Magneli phases (titanium «suboxides» and having the general formula TinO2n-1, where n=4-10), commercially recognized under the Ebonex® trade name, were used as substrates for designing of dimensionally stable anodes. The non-continuous platinum transition layer (2 mg Pt per cm2) was formed before deposition of the resulting coating by electrochemical-pyrolytic method. The chemical and phase composition of the resulting layer and its physicochemical properties were investigated. According to the data obtained, the main phase of the commercial Ebonex® is Ti6O11. The system begins to collect oxygen during the thermal treatment due to oxidation of the suboxides with the air oxygen. Hollandite is one of the phases appeared already at 2300Ñ, it splits into two phases, Ti5O9 and TiO2, during the treatment. The transformation of the system continues with a subsequent increase in the temperature and a new phase of titanium oxide appears at 3100C instead of Ti5O9. This phase was identified for the first time. The amount of oxygen in the system increases at 4100C, which leads to the additional appearance of TiO2 in the form of rutile. It has been shown that the service life of dimensionally stable anodes is largely determined by the nature of the substrate and the temperature of the formation of a transition layer. The maximum lifetime of the anodes was observed for the substrates treated at 4100C. At the same time, the maximum service life of the anode at 500 mA cm-2 was 325 hours with an active coating of PbO2-TiO2, which exceeds the common PbO2 system by 16 times.