Secondary ion mass spectrometric studies on the formation mechanism of IrO2/ZrO2 based electrocatalytic thin films

Secondary ion mass spectrometry (SIMS) was used to analyse the formation mechanism of IrO/ZrO film electrodes. The coating mixtures with compositions 20% Ir+80% Zr and 50% Ir+50% Zr prepared on titanium supports from alcoholic solutions of IrCl.HO and ZrOCl.8HO precursors were heated to specified temperatures and analysed by SIMS. The process of the electrode film evolution was followed via concentration depth profiles of O , Cl, IrO/, ZrO/ and TiO/ selected species. It was found that at lower temperatures and lower noble metal contents, the governing mechanism of oxide formation is hydrolysis, while at higher temperatures and higher noble metal concentrations the oxidative mechanism of film formation prevails. The surface accumulation of IrO, observed by SIMS at 500 °C for films with less than 50% IrO content, and of ZrO, observed for films with over 50% IrO, was confirmed by emission Fourier transform infrared measurements. No reaction between film components or between coatings and support was identified in the systems investigated. The results are in harmony with, and complementary to, those of former measurements by RBS and WAXS.