Investigating the Unrevealed Photocatalytic Activity and Stability of Nanostructured Brookite TiO₂ Film as an Environmental Photocatalyst

Abstract

Among three polymorphs of TiO, the brookite is the least known phase in many aspects of its properties and photoactivities (especially comparable to anatase and rutile) because it is the rarest phase to be synthesized in the standard environment among the TiO polymorphs. In this study, we address the unrevealed photocatalytic properties of pure brookite TiO film as an environmental photocatalyst. Highly crystalline brookite nanostructures were synthesized on titanium foil using a well-designed hydrothermal reaction, without harmful precursors and selective etching of anatase, to afford pure brookite. The photocatalytic degradation of rhodamine B, tetramethylammonium chloride, and 4-chlorophenol on UV-illuminated pure brookite were investigated and compared with those on anatase and rutile TiO. The present research explores the generation of OH radicals as main oxidants on brookite. In addition, tetramethylammonium, as a mobile OH radical indicator, was degraded over both pure anatase and brookite phases, but not rutile. The brookite phase showed much higher photoactivity among TiO polymorphs, despite its smaller surface area compared with anatase. This result can be ascribed to the following properties of the brookite TiO film: (i) the higher driving force with more negative flat-band potential, (ii) the efficient charge transfer kinetics with low resistance, and (iii) the generation of more hydroxyl radicals, including mobile OH radicals. The brookite-nanostructured TiO electrode facilitates photocatalyst collection and recycling with excellent stability, and readily controls photocatalytic degradation rates with facile input of additional potential.

Photocatalytic Degradation and Hydrogen Production of TiO2/Carbon Fiber Composite Using Bast as a Carbon Fiber Source

“…TiO 2 nanomaterials possess commendable performance in terms of its nontoxic, cost effectiveness, strong oxidizing activity, and long-term stability against photocorrosion, which have a very broad application prospect in many fields, such as air pollution, waste water treatment, hydrogen production, and sterilization [2][3][4][5][6][7]. The application of TiO 2 nanomaterials is greatly limited due to the poor visible light response and high charge recombination rate, originating from the wide band gap (3.2 eV for anatase and 3.0 eV for rutile) and the relatively high electrical resistance.…”

Structural‐Phase Catalytic Redox Reactions in Energy and Environmental Applications

“…It is highlighted that the difficulty in brookite‐based TiO 2 synthesis makes it the least investigated phase comparing with anatase and rutile. In a recent study, Choi et al had approached the unrevealed properties of brookite TiO 2 film as a photocatalyst for PC‐AOPs application, through the photocatalytic degradation of several organic compounds, such as rhodamine B and tetramethylammonium chloride. Comparing with anatase and rutile TiO 2 , the brookite phase exhibited much higher photoactivity, despite its smaller specific surface area compared with anatase.…”

Metal Oxide Compact Electron Transport Layer Modification for Efficient and Stable Perovskite Solar Cells

“…However, using brookite TiO 2 NPs instead of anatase TiO 2 in PSCs has numerous advantages. Compared with anatase TiO 2 , brookite TiO 2 has (i) a higher driving force with more favorable energy-level alignment with the perovskite layer, (ii) higher capacity for charge transfer, (iii) increased crystallinity, (iv) synthesis at relatively low temperature, (v) higher conductivity, (vi) higher electron mobility to facilitate photogenerated electron collection, and (vii) higher thermal stability [80][81][82]. The conduction band edge of brookite is slightly higher than those of anatase and rutile TiO 2 , which is expected to promote efficient electron transfer from the brookite to the anatase phase ( Figure 5b).…”