Surface Structure and Phase Composition of TiO2 P25 Particles After Thermal Treatments and HF Etching

Abstract

The anatase to rutile phase transformation via thermal and chemical (HF etching) routes of TiO 2 P25 has been investigated. The treatment parameters and properties of the resulting anatase and rutile nanoparticles are analyzed and discussed. Since the nature of TiO 2 surfaces plays a significant role in determining the physical and chemical properties of the TiO 2 nanoparticles, it is important to investigate the surface properties, including the morphology, the main exposed faces, the defectiveness, to be correlated with their peculiar properties, and then reactivity. Herein, we report an infrared spectroscopy investigation, employing the adsorption of CO probe molecule at low temperature, including 12 CO and 12 CO-13 CO isotopic mixtures, at the surface sites of TiO 2 P25, previously heated from room temperature to 1,023 K under vacuum conditions. The same FTIR experiments were adopted on HF-etched TiO 2 . X-ray diffraction and transmission electron microscopy analyses were adopted to elucidate the role played by the thermal and the HF-etching treatments in modifying not only the distribution of exposed surfaces, but even the phase composition of the pristine TiO 2 P25 samples, which are initially dominated by the most thermodynamically stable (101) facets of the anatase phase. The present study helps in the crystal and exposed facet engineering for the development of highly efficient photocatalysts.

Photocatalytic Activity of Silver-Based Biomimetics Composites

“…The XRD patterns of pristine catalysts and catalysts with 10 wt.% Ag are shown in Figure 3 . Figure 3 A, corresponding to TiO 2 NWs (pristine or with 10 wt.% Ag), shows intense peaks at 27° (110), 36° (101), and 55° (211), which have been unambiguously ascribed to the rutile phase (JCPDS 88-1175) [ 28 ]. The 10% Ag @ TiO 2 NW diffractogram, as well as the rest of the catalysts with other percentages of silver, showed a small shift towards lower angles compared to the pure TiO 2 NWs.…”

“…The characteristic peaks of anatase (JCPDS 21-1272) can be found at ca. 25° (101), 38° (004), 48° (220), 54° (105), and 55° (211) [ 28 ], while the rutile crystalline phase has its characteristic peaks at ca. 27° (110), 36° (101), 41° (111), and 54° (211) (JCPDS 34-180) [ 28 ].…”

“…25° (101), 38° (004), 48° (220), 54° (105), and 55° (211) [ 28 ], while the rutile crystalline phase has its characteristic peaks at ca. 27° (110), 36° (101), 41° (111), and 54° (211) (JCPDS 34-180) [ 28 ]. All the peaks corresponding to both anatase and rutile are present in the diffraction pattern of Figure 3 B–D.…”

Synthesis and Characterization of Titanium Dioxide Hollow Nanofiber for Photocatalytic Degradation of Methylene Blue Dye

“…Degussa P25, a commercially available TiO 2 , is one of the most efficient photocatalysts in terms of cost and photocatalytic ability, with a number of works published elsewhere [ 7 , 8 , 9 , 10 , 11 ]. Despite that, these studies reported some issues with this particular photocatalyst, and one of them is the high bandgap energy (~3.2 eV) The high bandgap value limits the light utilization efficiency and reduces the number of electrons that could participate in the redox reaction, which consequently deteriorates the photocatalytic activity.…”

Self-Cleaning Polyester Fabric Prepared with TiOF2 and Hexadecyltrimethoxysilane

“…The crystallinity and structural properties of the synthesized TiOF 2 were characterized using an X-ray diffractometer (XRD, Rikagu, D/Max-2500, Austin, TX, USA) equipped with Cu-Kα radiation at 40 kV and 200 mA. Quantitative analyses of TiOF 2 and anatase TiO 2 were carried out using Spurr and Myers relationship (A (wt.%) = 1/(1 + 1.265 × (I O /I F )) × 100, where I O is the integrated intensity of anatase TiO 2 (101) at 25.3° and I F is the integrated intensity of TiOF 2 (100) at 23.4°) to calculate the phase compositions of the synthesized photocatalyst [ 37 , 38 ]. The average crystal sizes were also calculated using the Scherrer equation (L = 0.90λ/(β − βi) cos θ, where β is the observed FWHM (fulll width at half maximum) and is the calculated instrumental broadening) [ 37 , 38 ].…”