Oxygen Rich Titania: A Dopant Free, High Temperature Stable, and Visible‐Light Active Anatase Photocatalyst

Abstract

The simultaneous existence of visible light photocatalytic activity and high temperature anatase phase stability up to 900 °C in undoped TiO2 is reported for the first time. These properties are achieved by the in‐situ generation of oxygen through the thermal decomposition of peroxo‐titania complex (formed by the precursor modification with H2O2). Titania containing the highest amount of oxygen (16 H2O2‐TiO2) retains 100% anatase phase even at 900 °C, where as the control sample exists as 100% rutile at this temperature. The same composition exhibits a six‐fold and two‐fold increase in visible light photocatalytic activities in comparison to the control sample and the standard photocatalyst Degussa P‐25 respectively. Among the various para­meters affecting the photocatalytic action, such as band gap narrowing, textural properties, crystallite size, and anatase phase stability, band gap narrowing was identified as the major factor responsible for the visible light photocatalytic activity. Increased Ti–O–Ti bond strength and upward shifting of the valence band (VB) maximum, which is responsible for the high temperature stability and visible light activity respectively, are identified from FT–IR, XPS, and photoluminescence (PL) spectroscopic studies. It is therefore proposed that the oxygen excess defects present in these titania samples are responsible for the high temperature stability and enhanced visible light photocatalytic activities.

Antibacterial properties of F-doped ZnO visible light photocatalyst

“…Photocatalysts such as TiO 2 or ZnO activated by UV or/and visible light (Fig. 9) [37][38][39][40][41][42][43][44] as a result of the transfer of an electron from the valance band (VB) to the conduction band (CB). The ROS produced as a result of the photocatalytic reaction will be capable of damaging the cell wall and can decompose the cellular materials (Fig.…”

“…Fluorine also plays an important role as it can reduce the band gap of the photocatalyst and increase its photocatalytic performance in the visible light region [38][39][40][41]. It is also evident from the studies that oxygen defects play an important role in obtaining optimum properties [40]. Therefore the antibacterial property observed for F-doped ZnO is most likely a combination of the toxic effects of Zn ions, oxygen excess defects, and the addition of F into the ZnO lattice.…”

“…Due to small size and high surface-to-volume ratio, the obtained nanopowders have enhanced antimicrobial activity since the aforementioned factor allows for better interaction with bacteria. It could be possible to develop semiconductor materials with superior antibacterial action by modifying the oxygen defects [40]. An aqueous peroxotitania route for the synthesis oxygen rich TiO 2 photocatalysts has been reported [40].…”

“…It could be possible to develop semiconductor materials with superior antibacterial action by modifying the oxygen defects [40]. An aqueous peroxotitania route for the synthesis oxygen rich TiO 2 photocatalysts has been reported [40]. In situ generation of oxygen during the decomposition of the peroxotitania complex resulted in the formation of oxygen defects in anatase titanium dioxide.…”

“…These defective oxygen excess photocatalysts were characterized using valence band (VB) XPS, XRD, Raman and photo-luminescence (PL) spectroscopy. Excess oxygen present in the photocatalyst can perform as an electron trap and therefore the overall photocatalytic activity can be improved [40]. A similar peroxo-precursor method could potentially be employed to improve the oxygen defects in ZnO and thereby the photocatalytic properties.…”