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 X-ray 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.