Sol‐Gel‐Derived TiO2 Film Semiconductor Electrode for Photocleavage of Water: Preparation and Effects of Postheating Treatment on the Photoelectrochemical Behavior

Abstract

The effects of postheating on the photoelectrochemical behavior of film electrodes prepared by the sol‐gel method have been investigated over a heating temperature range of 600–900°C. in the sol‐gel‐derived films were anatase on heating below 800°C and transformed into rutile. It was found that the photocurrent shows a maximum at a certain heating time for each of the heating temperatures at 900°C. At the same time, other properties such as the flatband potential shift and donor density also showed a maximum at the corresponding heating time. These results are explained as follows. An increase in the photocurrent of the as‐prepared film electrode with increasing heating time results from the improvement of crystallinity and the increasing Ti3+ concentration due to the reduction of Ti4+ by the undecomposed organic residue. Further heating, however, causes a decrease in the specific surface area and Ti3+ concentration due to the reoxidation of Ti3+ to Ti4+, resulting in the reduction of the photocurrent. (anatase) has only an indirect bandgap at 3.03 eV, while (rutile) has an indirect bandgap at 2.92 eV and a direct bandgap at 3.13 eV.