Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10275904 | Journal of Electroanalytical Chemistry | 2005 | 6 Pages |
Abstract
A homogenous and transparent IrO2 film was prepared on an ITO electrode by anodic electrodeposition under galvanostatic conditions from an aqueous solution containing 2 mM K2IrCl6 and 40 mM oxalic acid that is aged at 37 °C and pH 10 for ca. 10 days. The absorption spectral change of the solution suggested that an IrO2 colloid is formed in the solution during ca. 10 day-aging. The scanning electron microscopic (SEM) measurement displayed homogeneous deposition of IrO2 particles with 100-250 nm of a diameter on the surface of the film. The X-ray diffraction (XRD) measurement indicated that IrO2 in the film is amorphous. The cyclic voltammogram (CV) of the IrO2-coated ITO electrode dipped in a 0.1 M KNO3 aqueous solution exhibited a steep rise of an anodic current at 1.0 V vs SCE for catalytic water oxidation, as well as an anodic wave at 0.3 V and a corresponding cathodic wave at â0.1 V that are assigned as an IrIV/IrV redox. The anodic current at 1.3 V on the CV was 660 times higher than that for a blank bare ITO electrode. Ir electrodeposited on the ITO electrode was also shown to be electrocatalytically active for water oxidation. However, the anodic current at 1.3 V on the CV for the Ir-coated ITO electrode was 14 times lower than that for an IrO2-coated electrode in spite of the 34 times higher coverage of Ir. The potential static electrochemical water oxidation using the IrO2-coated ITO electrode produced a significant amount of O2 above 1.1 V vs Ag/AgCl, in contrast to no O2 detected even at 1.3 V using a bare ITO electrode. The maximum turnover frequency (TOF) of the IrO2 catalyst was provided as 16,400 ± 450 hâ1 at 1.3 V vs Ag/AgCl from the slope of the linear plots of the amount of O2 vs coverage of IrO2 in the range of â¼1.5 Ã 10â9 mol. The TOF was 450 times higher than that (36.4 ± 1.4 hâ1 at 1.3 V) for electrodeposited Ir showing the very high catalytic activity of the IrO2 film.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
Masayuki Yagi, Emi Tomita, Takayuki Kuwabara,