Effect of precursor baking on the electrochemical properties of IrO₂-Ta₂O₅/Ti anodes

IrO₂-Ta₂O₅/Ti anodes were thermally pretreated by means of baking and continuous heating, and then thermal decomposition at 450 °C for 30 min. To prepare an IrO₂-Ta₂O₅/Ti anode, a Ti substrate was dipped in the precursor, baked at 80 or 90 °C for different periods, and then thermally decomposed at 450 °C for 30 min in the air furnace. The electrochemical properties of prepared IrO₂-Ta₂O₅/Ti anodes were evaluated through their voltammetric charges measured in the 1 M H₂SO₄ solution and their performance lives tested with 2 Acm⁻² in the 1 M H₂SO₄ + 0.5 M Na₂SO₄ solution. Microstructures of prepared IrO₂-Ta₂O₅/Ti anodes were characterized with x-ray diffractometer. The chemical compositions and surface morphologies of prepared IrO₂-Ta₂O₅/Ti anodes were analyzed with scanning electron microscope equipped with energy-dispersive x-ray spectrometer. Based on the results of x-ray diffraction, only IrO₂-diffracted peaks were detected from prepared IrO₂-Ta₂O₅/Ti anodes. A mud-crack surface structure was seen from prepared IrO₂-Ta₂O₅ coatings. The crack density and the crack width of an IrO₂-Ta₂O₅ coating were obviously affected by different thermal pretreatments of baking methods and heating rates. The crack width of IrO₂-Ta₂O₅ coating increased with an increasing the baking time. A relatively high voltammetric charge can be found from the IrO₂-Ta₂O₅/Ti anode with wide cracks and high crack density. On the other hand, long lifetime values were detected from the IrO₂-Ta₂O₅/Ti anode with a crack width more than 2 μm. The highest voltammetric charge was detected from the IrO₂-Ta₂O₅/Ti anode prepared through baking at 90 °C for 180 s. On the other hand, the longest lifetime was found from the IrO₂-Ta₂O₅/Ti anode pretreated with continuous heating at a rate of 7 °C/min.