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The influence of an IrO 2 interlayer between the Ti substrate and the SnO 2-Sb 2 O 5 coating on the electrode service life and on the efficiency of p-chlorophenol (p-CP) oxidation for wastewater treatment has been investigated. The results have shown that if the loading of the SnO 2-Sb 2 O 5 coating relative to the IrO 2 interlayer loading (c ratio defined by Equation 1) is high (c ¼ 20-30) the service life of the electrode can be increased without modification of the ability of this electrode to perform p-CP oxidation. This suggests that the oxidation of p-CP using a Ti/IrO 2 /SnO 2-Sb 2 O 5 electrode with high c ratio (c > 20) occurs only through the SnO 2-Sb 2 O 5 component of the electrode, with no interference of the IrO 2 interlayer. However, the electrode potential at a given current density is considerably lower in the case of the Ti/IrO 2 /SnO 2-Sb 2 O 5 electrode. In order to explain this decrease in electrode potential we speculate that water is firstly discharged on IrO 2 , which is present in small amounts on the surface, forming hydroxyl radicals at a relatively low potential. These active hydroxyl radicals then migrate (spill over) towards the SnO 2-Sb 2 O 5 coating, where they are physiosorbed and react with p-CP leading to complete combustion.

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