Structure and Hydrogen Sensing Properties of Plasma Electrochemically Oxidized Titanium Foils

Abstract

Abstract Plasma electrochemical oxidation (PEO) of titanium foils is the key step in the production of platinum/TiO2/Ti sandwich structures that can be used as hydrogen sensors. If a voltage is applied between the platinum contact and the supporting Ti foil, the structures indicate current–voltage curves that depend on the H2 concentration in air. The sensing mechanism, based on catalytic oxidation of H2 and hydrogen doping of TiO2, is fast and reversible in a broad temperature regime. Particularly the devices can operate at room-temperature and hence do not require an additional heating. A suitable porosity enables a high surface area combined with a good accessibility of the reacting H2 and O2. Thermal stability is mandatory because catalytic heat is released during sensor operation at higher concentrations of hydrogen. Another important feature of the sandwich structures concerns the mechanical and electrical stability of the oxide film since the operation voltages are typically in a range of ± 10 V. Our structural study serves as an important contribution towards an understanding of the interplay between process parameters and sensor properties.