THERMALLY PREPARED TI RHOX ELECTRODES .1. STRUCTURAL, ELECTRONIC AND SURFACE-PROPERTIES/

Layers of Rh oxide on Ti and quartz supports have been prepared by the rmal decomposition of RhCl3 in aqueous HCl solutions in the temperatur e range 400-800-degrees-C (600-degrees-C on Ti). Structure and composi tion have been studied by X-ray diffraction, SEM, TEM, UVS, XPS and ir spectroscopy. Both amorphous and crystalline phases, whose proportion s vary with the calcination temperature, have been detected in the coa tings. Results show that decomposition from the dissolved precursor re sults in different products with respect to the solid precursor. In pa rticular, a variety of Rh oxyhydroxychloride complexes are formed at l ow temperatures while alpha-Rh2O3 prevails at high temperatures. In th e case of Ti, the support also takes part in the decomposition process owing to its tendency to be oxidized. Partial hydrolysis of the precu rsor in solution and during the early stages of calcination is respons ible for the specific properties of the coatings.