Influence of calcination temperature of IrO2/Ti electrodes on oxygen reduction

IrO2-coated titanium plate electrocatalysts prepared by a dip-coating method (IrO2/Ti) with different calcination temperatures are characterized by scanning electron microscope, X-ray diffraction and Xray photoelectron spectroscopy. The electrocatalytic behavior of the oxygen reduction reaction (ORR) is evaluated by cyclic voltammetry and galvanostatic electrolysis in 1 mol dm(-3) KOH solution. The effects of calcination temperature on the oxygen reduction pathway are examined. Galvanostatic electrolysis results show that the reaction pathway on the IrO2/Ti electrode prepared at high calcination temperature is mainly a two-electron pathway producing H2O2. It is observed that higher calcination temperatures produce: a more uniform fault-free surface; reduced levels of Cl contamination (residual Cl presumably from incomplete IrCl3 decomposition during the coating process); higher levels of rutile character of the IrO2 layer: lower hydration levels. It is confirmed that ORR electrocatalytic behavior on highly hydrated IrO2 is better than on slightly hydrated IrO2. (C) 2008 Elsevier B.V. All rights reserved.