ELECTROCHEMICAL-BEHAVIOR OF RUTI

The electrochemical properties of RuTi alloy in acidic solution have been investigated by means of steady-state polarization measurements and cyclic voltammetry. The resolved current-potential profiles for the formation/reduction of surface oxides and the deposition/dissolution of H at a RuTi electrode are basically similar to those at an elemental-Ru electrode. However, whereas the oxygen-evolution and Ru-corrosion reactions occur at nearly the same potential on elemental Ru, these reactions are well resolved on RuTi alloy; the Ru-corrosion reaction is shifted anodically by about 400 mV. RuTi alloy does not catalyze the methanol-oxidation reaction; it forms a hydride on cycling negative of the normal hydrogen potential. Although hydride formation appears to suppress the hydrogen evolution reaction, nevertheless the hydrogen-evolution activity remains relatively high. Interpretation of this behavior has been made with a model that involves a two-step oxidation of the alloy surface; the second step involves the migration of metal atoms as cation species to form a gelatinous layer of octahedrally coordinated cations and the inhibition of RuO4 formation by more basic Ru-O-M bridges.