Influence of the preparation method on the morphological and electrochemical properties of Ti/IrO2-coated electrodes

The IrO2 layer deposited on a Ti substrate for electrocatalysis of the oxygen evolution reaction (OER) in acidic media was obtained from one of three different deposition methods consisting of painting the substrate with the corresponding solutions followed by heat treatment at a temperature range 400-600 degrees C for 1 h. The coating solutions were prepared by dissolving IrCl3. 3H(2)O in 15% HCl (traditional method), by dissolving iridium acetylacetonate in isopropanol and acetic acid (inorganic sol-gel method) and by dissolving IrCl3. 3H(2)O in ethyleneglycol and citric acid (Pechini method). The redox processes occurring on these films were characterized by cyclic voltammetry at 20 mV s(-1) in 0.5 M aqueous H2SO4 at room temperature. The measured anodic voltammetric charge is related to the active area of the electrode; the electrode derived from traditional method had the highest value. The Tafel plots revealed that the electrocatalytic activities are not affected by the surface morphology, indicating that the preparation procedures produce electrocatalytic coatings with comparable activity. For an applied current density of 100 mA cm(-2) the combination of the conductivity and roughness effects caused the electrode derived from inorganic gel and heat-treated at 400 degrees C to exhibit the lowest overpotential for the OER. On the other hand, the accelerated life tests performed at 80 degrees C in 30% aqueous H2SO4 with an anodic current density of 750 mA cm(-2) showed that the stability of the coatings increases with the temperature of the heat-treatment and the Pechini-derived electrodes had a longer-life time under this condition in all the cases. The accelerated life test showed that the factor limiting the operational life of these electrodes is the dissolution of the active layer, (C) 2000 Elsevier Science Ltd. All rights reserved.