Hydrothermal modification of electrocatalytic and corrosion properties in nanosize particles of ruthenium dioxide hydrate

Abstract

Preformed hydrosols comprising 38 nm diameter particles of amorphous ruthenium dioxide hydrate are subject to hydrothermal modification at temperatures between 100 and 225 °C. Hydrothermally induced changes in sol composition have been characterised by transmission electron microscopy (TEM), UV–VIS spectrophotometry, thermogravimetric (TG) analysis and X-ray powder diffraction (XRD). Hydrothermally modified sols 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 both evolved oxygen and ruthenium tetraoxide produced by oxidative corrosion of the catalyst. Sols hydrothermally modified at 200 °C show a 20-fold decrease in corrosion and a >5-fold decrease in electrocatalytic rate, these changes are attributed to increased oxygen bridging between surface Ru atoms resulting from hydrothermally induced condensation reactions between surface hydroxy groups.