X-RAY-DIFFRACTION CHARACTERIZATION OF IRIDIUM DIOXIDE ELECTROCATALYSTS

An X-ray diffraction (XRD) line-broadening analysis of coatings of pyrolytic iridium dioxide supported on amorphous silica microbeads is reported. The influence of the temperature of pyrolysis and of the annealing treatments on the average crystallite sizes of the IrO2 and Ir phases have been studied in detail. The values obtained for IrO2 are lower than those obtained from an analgous RuO2 system. However, the analysis suggests that in both cases the crystalline phase grows within an amorphous microcrystalline environment where impurities are mostly segregated in the amorphous phase and then released to the atmosphere. The lattice parameters are also calculated. Compared with the reference values, slightly greater values are obtained both for IrO2 and for Ir.