Investigation of the oxygen evolution reaction on Ti/IrO2 electrodes using isotope labelling and on-line mass spectrometryle

Oxygen evolution on Ti/IrO2 anodes has been studied in 1M HClO4 electrolyte using O-18 labelling together with differential electrochemical mass spectrometry (DEMS) measurements. It has been shown that during successive cyclic voltammetric measurements in H-2 O-18 containing electrolyte the amount of O-16(2) (m/z= 32) decreases, with a concomitant increase of (OO)-O-18-O-16 (m/z = 34) after each cycle before reaching a steady state after four cycles. The obtained higher O-16(2) concentration in the evolved oxygen during the first scans is because O-16 from the IrO2 film contribute in the oxygen evolution reaction. Analysis of the experimental data has shown that the amount of lattice oxygen, which is involved in the oxygen exchange reaction, is in the order of 1% of the total IrO2 loading. This is an indication that only the outer surface of the oxide electrode participates in the oxygen evolution reaction. In a second series of experiments it has been demonstrated that oxygen evolution on (IrO2)-O-16 in (H2O)-O-18 containing electrolyte result in the formation of (IrO2)-O-18. Consequently, we can conclude that the IrO2 layers participate in the oxygen evolution reaction in acid media at least to a several monolayer extend. (c) 2007 Elsevier B.V. All rights reserved.