Ex situ and in situ characterization studies of spin-coated TiO2 film electrodes for the electrochemical ozone production process

An electrode composed of silicon/titanium oxide/platinum/titanium dioxide (Si/TiOX/Pt/TiO2) was fabricated by spin-coating TiO2 multilayers on a Si/TiOX/Pt substrate and was used in electrochemical ozone production (EOP). EOP was realized when the Si/TiOX/Pt substrate was completely covered with the TiO2 film and a current efficiency of 7% was achieved at a low current density of 26.7 mA cm−2 in 0.01 M HClO4 at 15 °C. The TiO2 film was found to be of an anatase-type TiO2 and that to comprise aperture structures from the X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations. Moreover, the fabricated TiO2 film was found to be an n-type semiconductor by photoelectrochemical measurements. The high efficiency at a low current density of EOP on the TiO2 n-type semiconductor was explained to result from the electron transfer through the TiO2/HClO4 interface as tunneling current. When the tunneling current passes through a depletion layer of TiO2, the electrode potential is necessarily high enough to facilitate EOP.