Chemical Vapor Deposition of Photocatalytically Active Pure Brookite TiO₂ Thin Films

Abstract

Brookite is the least investigated phase of TiO2 due to the synthetic difficulty of obtaining the pure phase. Here, we present the first ever chemical vapour deposition synthesis of pure brookite TiO2 thin films. The films were highly crystalline and phase pure as determined by X-ray diffraction and Raman spectroscopy studies. Scanning electron microscopy studies showed the films to have a structured morphology consisting of pyramidal features. The photocatalytic properties of the brookite film, tested using stearic acid under UVA (365 nm) irradiation, were superior to both an anatase film grown under similar conditions and NSG Activ TM glass. Transient absorption spectroscopy showed that the innate electron-hole recombination dynamics are similar in brookite and anatase, akin to previous reports. The superior activity of the brookite film is hence attributed to the higher surface area compared to anatase.

Influence of Lithium and Lanthanum Treatment on TiO2 Nanofibers and Their Application in n‐i‐p Solar Cells

“…Interestingly, while the XRD pattern of the control and La−TiO 2 NFs matched the anatase phase, the XRD pattern for Li−TiO 2 NFs shows additional peaks which matched the rutile phase of TiO 2 . Since all NFs were sintered at 500 °C, it is evident that the addition of Li salts to the precursor solution facilitated the formation of the rutile phase that normally occurs between 600–800 °C . This is consistent with previous reports where Li treated TiO 2 NPs which were produced via the sol‐gel route, show a mixture of anatase and rutile phases .…”

“…For instance, due to a wide band gap it is only active in the UV region of the solar spectrum which is a significant disadvantage for photocatalysis considering that only 4 % of this high energy light reaches the earth's surface. TiO 2 is commonly found in three different crystal forms, namely metastable anatase (tetragonal), stable rutile (tetragonal) and brookite (orthorhombic) phase . These phases possess different characteristics, where the most suitable one for solar cell applications is the anatase phase due to its superior charge transport ability …”

The Sonophotocatalytic Degradation of Pharmaceuticals in Water by MnOx-TiO2 Systems with Tuned Band-Gaps

“…Therefore, anatase and brookite have longer electron-hole pair lives than rutile, which makes them more suitable to carry charges for longer times. Longer electron-hole pair lifetimes in anatase compared to rutile are preferable for charge carriers to participate in surface reactions [54]. On the other hand, there are many other surface properties that affect molecular adsorption and the photocatalytic activity.…”

The effect of titanium dioxide synthesis technique and its photocatalytic degradation of organic dye pollutants

“…Nonetheless, critical issues that often limit the photocatalytic activity of TiO 2 materials are the wide band gap energy (3–3.2 eV), low mass transport rates and low quantum yield. To succumb these critical challenges, a plethora of scientific strategies have been adopted by researchers, such as reducing grain size of TiO 2 and increasing its specific surface area and also by employing different synthesis techniques such as solvothermal method [19] , precipitation method [20] , sol-gel method [21] , thermal decomposition of alkoxide [22] , chemical vapor deposition [23] . Among these techniques, sol–gel technique, is a simple, economical, convenient and accomplished technique for producing nanoparticles which have different morphologies such as sheets, tubes, quantum dots, wires, rods and aerogels.…”