Electrosynthesized TiO2 films: dependence of the brookite–anatase ratio on the applied potential

Abstract

TiO 2 films were produced on ITO using a two-step method: (i) potentiostatic electrosynthesis of an amorphous titanium oxyhydroxide gel and (ii) subsequent crystallization by a thermal treatment (TT). The influence of applied potential on the morphology and on the crystalline structure of the resulting films was studied for three different TT temperatures, using SEM, XRD, and Raman spectroscopy. The films were porous and their morphology was more affected by the potential than by the temperature. The obtained TiO 2 presented a high degree of crystallinity. The brookite-anatase coexistence was observed for all synthesis conditions. Nevertheless, the brookite content decreased for samples synthesized at more negative potentials, irrespective of the TT temperature. A relative estimate of brookite content variation among the prepared samples was obtained from an analysis of Raman spectra, and it was shown to be related with the pH variation during electrosynthesis. This correlation is in accordance with reported dependence of brookite-anatase ratio in sol-gel synthesis, which decreases with an increase in pH.

Photoelectrochemical characterization of ITO/TiO2 electrodes obtained by cathodic electrodeposition from aqueous solution

“…One can mention distinct methods to obtain a TiO 2 film, such as sol-gel [21], Pechini [22] and hydrothermal [23]; however, these methods are wet routes, favoring the metastable polymorphs formation (i.e., anatase, brookite), in a ratio that depends on the synthesis variables. In this way, the electrosynthesis (ES) of TiO 2 is an interesting alternative to traditional methods cited above, once such method permits fine-tuning of the synthesis variables, such as current and applied potential [24,25]. Karuppuchamy et al [26] prepared crystalline TiO 2 films on several steel substrates by a one-step electrochemical method at low temperature in basic media.…”