Structure and semiconductor properties of titanium suboxide-based composite electrocatalysts

Chem. Met. Alloys 14 (2021) 58-63

https://doi.org/10.30970/cma14.0418

Alexander VELICHENKO, Vasyl KORDAN, Olesia SHMYCHKOVA, Valentina KNYSH, Pavlo DEMCHENKO

Naked Ti/TiO₂ nanotubes contain a significant amount of X-ray amorphous compounds on the surface, which are most likely hydrated titanium oxides. The main crystalline phase is titanium dioxide in the allotropic form anatase. Metallic titanium is present on the surface in trace amounts. Thermal treatment of this material at a temperature of 500°C for 3 hours in an air atmosphere led to an increase in the proportion of the crystalline phase. The content of metallic titanium increased significantly, reaching about a third. A partial electrochemical reduction of the nanotubes allowed obtaining more electrically conductive titanium suboxides. After a cathodic reduction of the nanotubes for one hour, a galvanic coating with metallic platinum was uniformly deposited on the surface of the material. Thermally treated Ti/TiO₂ nanotubes are an n-type semiconductor with a flat-band potential equal to –0.589 V and a carrier concentration of 6×10²⁰ cm^-3. Such a high concentration of carriers is obviously due to the small thickness of the oxide film and its non-stoichiometry, as a result of which the surface is not very depleted in electrons, since titanium metal acts as a donor.

SEM-images of the following surfaces: reduced Ti/TiO₂-Pt nanotubes (left); thermally treated reduced Ti/TiO₂-Pt nanotubes (right).

Keywords

Platinized Ti/TiO₂ / Nanotubes / Thermal treatment / Charge carriers / Phase composition