Markedly Enhanced Surface Hydroxyl Groups of TiO2 Nanoparticles with Superior Water-Dispersibility for Photocatalysis

Abstract

The benefits of increasing the number of surface hydroxyls on TiO2 nanoparticles (NPs) are known for environmental and energy applications; however, the roles of the hydroxyl groups have not been characterized and distinguished. Herein, TiO2 NPs with abundant surface hydroxyl groups were prepared using commercial titanium dioxide (ST-01) powder pretreated with alkaline hydrogen peroxide. Through this simple treatment, the pure anatase phase was retained with an average crystallite size of 5 nm and the surface hydroxyl group density was enhanced to 12.0 OH/nm2, estimated by thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Especially, this treatment increased the amounts of terminal hydroxyls five- to six-fold, which could raise the isoelectric point and the positive charges on the TiO2 surface in water. The photocatalytic efficiency of the obtained TiO2 NPs was investigated by the photodegradation of sulforhodamine B under visible light irradiation as a function of TiO2 content, pH of solution, and initial dye concentration. The high surface hydroxyl group density of TiO2 NPs can not only enhance water-dispersibility but also promote dye sensitization by generating more hydroxyl radicals.

Morphological Control of Mesoporosity and Nanoparticles within Co3O4–CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance

“…72 This is because surface hydroxyl groups are creating more • OH radicals for the photocatalytic application. 73 Presently, from the XPS study of O 1s core-level spectrum (Figure 7), the presence of the surface hydroxyl groups in the mesoporous composite Co 3 O 4 −CuO NFs is proved. The generated • OH radicals from the surface hydroxyl groups enhanced the phenolic compounds degradation.…”

Band Gap Implications on Nano-TiO2 Surface Modification with Ascorbic Acid for Visible Light-Active Polypropylene Coated Photocatalyst

“…Figure 4 a (bottom) shows strong binding energy peaks at 458.4 and 464 eV that are ascribed to the 2p 3/2 and 2p 1/2 core levels of Ti 4+ and assigned to the chemical interaction between TiO 2 and AA molecules [ 34 , 35 , 36 , 37 ]. The O 1s spectrum of commercial Anatase showed in Figure 4 b (top) present two binding energy peaks at 528.6 and 532.1 eV that are attributed to Ti–O bond of lattice oxygen of TiO 2 and non-lattice oxygen respectively as the Ti–OH terminal groups [ 40 , 41 ]. The pure [TiO 2 ] A sample is shown in Figure 4 (b, in the middle) in which two binding energy peaks at 531.2 and 533.6 eV are visible due to the presence of the OH group with oxygen at the bridging oxygen site (Ti-OH b ) [ 42 ] and to the physiosorbed H 2 O which is present as a consequence of the influence of water molecules on the sample surface due to the paste preparation [ 41 , 42 ].…”

“…The O 1s spectrum of commercial Anatase showed in Figure 4 b (top) present two binding energy peaks at 528.6 and 532.1 eV that are attributed to Ti–O bond of lattice oxygen of TiO 2 and non-lattice oxygen respectively as the Ti–OH terminal groups [ 40 , 41 ]. The pure [TiO 2 ] A sample is shown in Figure 4 (b, in the middle) in which two binding energy peaks at 531.2 and 533.6 eV are visible due to the presence of the OH group with oxygen at the bridging oxygen site (Ti-OH b ) [ 42 ] and to the physiosorbed H 2 O which is present as a consequence of the influence of water molecules on the sample surface due to the paste preparation [ 41 , 42 ]. Figure 4 b (bottom) for the modified [AA-TiO 2 ] A sample shows strong binding energy peaks at 529.8 and 532.4 eV that are assigned to the Ti–O surface bulk oxide lattice of TiO 2 and OH as a terminal group with oxygen attached to the five-coordinated Ti 4+ with an O–Ti 4+ covalent bond [ 42 ] or C–OH due to the interaction of TiO 2 with the AA [ 43 ].…”

Recyclable SERS-Based Immunoassay Guided by Photocatalytic Performance of Fe3O4@TiO2@Au Nanocomposites

“…This barrier inhibits the combination of photogenerated electron holes to a certain extent, thus giving them longer time intervals to diffuse to the surface and effectively promoting the possible redox reaction, as shown in Figure 5a [22,38,39]. In addition, since the effective adsorption of 4MBA molecules is a prerequisite for the catalysis, the photocatalytic efficiency has a certain relationship with the strength of the adsorption capacity [40][41][42]. Meanwhile, the increased surface with exposed Au provides more effective areas for absorbing 4MBA molecules.…”