HYDROTHERMAL MODIFICATION OF ELECTROCATALYTIC AND CORROSION PROPERTIES IN NANOSIZE PARTICLES OF RUTHENIUM DIOXIDE HYDRATE

Preformed hydrosols comprising 38 nm diameter particles of amorphous r uthenium dioxide hydrate are subject to hydrothermal modification at t emperatures between 100 and 225-degrees-C. Hydrothermally induced chan ges in sol composition have been characterised by transmission electro n microscopy (TEM), UV-VIS spectrophotometry, thermogravimetric (TG) a nalysis and X-ray powder diffraction (XRD). Hydrothermally modified so ls show substantial reductions in oxide hydration but show no evidence of increased crystallinity, Ostwald ripening, particle aggregation or agglomeration. Hydrothermally induced changes in electrocatalytic and corrosion behaviour have been characterized by using sols to catalyse the oxidation of water to oxygen by cerium(IV) ions, and measuring bo th evolved oxygen and ruthenium tetraoxide produced by oxidative corro sion of the catalyst. Sols hydrothermally modified at greater-than-or- equal-to 200-degrees-C show a 20-fold decrease in corrosion and a > 5- fold decrease in electrocatalytic rate; these changes are attributed t o increased oxygen bridging between surface Ru atoms resulting from hy drothermally induced condensation reactions between surface hydroxy gr oups.