The Preparation And Performance Improvement Of IrO₂-Ta₂O₅/Ti Anode For Oxygen Evolution

The IrO₂-Ta₂O₅ coating titanium anode exhibits good performance in electrocatalytic activity and electrochemical stability. It was recognized as the ideal anode material for oxygen evolution in acidic environment, but the low life and high cost restricted its wide application in many areas such as electroplating, waste-water treatment, cathodic protection, electrochemical synthesis of organic and so on. The IrO₂ (70mol %)-Ta₂O₅ (30mol %) coating titanium anode was investigated as main object in this paper. TiN/IrO₂-Ta₂O-5 titanium anodes, SnO₂-IrO₂-Ta₂O₅ ternary electrodes and orthogonal analysis designed IrO₂-Ta₂O₅ coating electrodes were prepared by the thermal decomposition method. The effect of TiN films, SnO₂ doping and synthesis parameters on the electrochemical performance of the IrO₂-Ta₂O₅ coating titanium anodes were studied in detail.IrO₂-Ta₂O₅ coated titanium anodes were prepared for the firt time at different sintering temperatures by thermal decomposition method on the Ti/TiN films which were in-situ synthsized by heat treating of Ti plates in the high-purity N₂. Surface cracks with a non-continuous structure were observed accompanied by IrO₂ nanocrystals with diameter ranging from 80 to 200 nm. The result showed that the cyclic voltammetric charge, steady-state open-circuit potential, oxygen evolution current and double-layer capacitance were better than the normal Ti-based IrO₂-Ta₂O₅ electrodes. The TiN films had an obvious influence on the performance of the electrodes when the sintering temperature was low. The catalytic activity and electrode life had obvious increase when the preparation temperature was lower than 500℃. The cell voltage and charge-transfer resisitance keep stable for much more time in the failure process of titanium anodes.SnO₂-IrO₂-Ta₂O₅/Ti coating anodes with different amount of SnO₂ doping were prepared via thermal decomposition by adding SnCl₄ to the coating solution. The result showed that the crack quantity droped and crack width decreased after the SnO₂ doping. When the content of SnO₂ was less than or equal to 10 mol %, the crystal size decreased, oxygen evolution current density, voltammetric charge, double-layer capacitance and the electrocatalytic activity increased. There are three stages in the electrolytic process, namely activation, stable, failure. Our results also proved that the presence of SnO₂ can improve the acid corrosion resistance and the stability of the coating anodes.For the first time, we investigated the sintering temperature, sintering time, proportion of iridium and tantalum, content of iridium, as well as acid treatment on catalytic activity of IrO₂-Ta₂O₅/Ti anodes by.orthogonal analysis. The best preparation conditions were obtained as follows: (1) The sintering temperature is 400℃; (2) The amount of Ir is 20 g/cm²; (3) Relative content of Ta₂O₅ is 55 wt%; (4) Thermal oxidation time is 2 h; (5) Etching solution is mixed with 18 wt% hydrochloric acid and saturated oxalic acid.