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 formati on mechanism of IrO2/ZrO2 film electrodes. The coating mixtures with c ompositions 20% Ir+80% Zr and 50% Ir+50% Zr prepared on titanium suppo rts from alcoholic solutions of IrCl3.3H(2)O and ZrOCl2.8H(2)O precurs ors were heated to specified temperatures and analysed by SIMS. The pr ocess of the electrode film evolution was followed via concentration d epth profiles of O-, Cl-, IrO2-, ZrO2- and TiO2- selected species. It was found that at lower temperatures and lower noble metal contents, t he governing mechanism of oxide formation is hydrolysis, while at high er temperatures and higher noble metal concentrations the oxidative me chanism of film formation prevails. The surface accumulation of IrO2, observed by SIMS at 500 degrees C for films with less than 50% IrO2 co ntent, and of ZrO2, observed for films with over 50% IrO2, was confirm ed by emission Fourier transform infrared measurements. No reaction be tween film components or between coatings and support was identified i n the systems investigated. The results are in harmony with, and compl ementary to, those of former measurements by RES and WAXS.