Electrochemical Oxide Formation on Titanium and Titanium Hydride (Deuteride) Thin-Film Surfaces

The electrochemical formation of oxides on the surfaces of titanium and titanium hydride (deuteride) thin films has been studied. The thin films were prepared in an ultrahigh vacuum environment and transferred in this environment into a cell where they are exposed to atmospheric pressure high purity argon and then to the aqueous electrolyte. Control experiments were conducted with Auger electron spectroscopy (AES) and quartz-crystal microgravimetry (QCM) to quantitate the oxide that would form on these surfaces prior to immersion in the electrolyte. The onset potential for further oxide formation was displaced from the formal potential for the Ti³⁺/Ti⁰ redox couple by ca. +0.5 V. The current/voltage curves showed that the rate of oxide formation was linear with applied potential (39–45 Å/V), consistent with a constant field growth mechanism which has been postulated for the gas-phase oxidation of this type of active metal. The onset potential for oxidation in the current/voltage curves is as close to the formal potential for active dissolution of the metal as is possible to obtain with the present apparatus, without resorting to continuous mechanical abrasion of the metal surface.