Abstract
The anatase to rutile phase transformation via thermal and chemical (HF etching) routes of TiO2 P25 have been investigated. The treatment parameters and properties of the resulting anatase and rutile nanoparticles are analyzed and discussed. Since the nature of TiO2 surfaces plays a significant role in determining the physical and chemical properties of the TiO2 nanoparticles, it is important to investigate the surface structure 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, by means of the adsorption of CO probe molecule at low temperature, including 12CO and 12CO-13CO isotopic mixtures, at the surface sites of TiO2 P25, previously heated from room temperature to 1023 K under vacuum conditions. The same FTIR experiments were adopted on HF-etched TiO2. 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 TiO2 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.
Highlights
Titanium dioxide (TiO2) is a multifunctional material that is a matter of interest in a wide range of applications, ranging from the photocatalysis to energy fields (Qadir et al, 2016; Jaksik et al, 2017; Cravanzola et al, 2018; Humayun et al, 2018; Tamgadge and Shukla, 2018; Hussain et al, 2019)
We report a Fouriertransform infrared (FTIR) spectroscopic study of the surface sites present on TiO2 P25 treated at different temperatures (RT, 473, 673, 773, 873, 973, and 1,023 K) or etched with HF solutions at different level of concentrations
A multi-technique characterization approach, based on FTIR, transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses for the investigation of thermally/HF-chemically modified TiO2 P25 powders has been shown in this contribution
Summary
Titanium dioxide (TiO2) is a multifunctional material that is a matter of interest in a wide range of applications, ranging from the photocatalysis to energy fields (Qadir et al, 2016; Jaksik et al, 2017; Cravanzola et al, 2018; Humayun et al, 2018; Tamgadge and Shukla, 2018; Hussain et al, 2019). TiO2 nanoparticles can be obtained by different preparation methods, including sol-gel methods, hydrothermal treatments, and flame spray pyrolysis. Along this line, TiO2 crystals prepared by flame hydrolysis of TiCl4 reveal a nearly perfect crystalline habit and can be substantially different from samples prepared by wet-chemistry pathways. Crystallinity, sizes of TiO2 nanoparticles, obtained by other synthetic procedures, can differ remarkably (Djaoued et al, 2002; Uddin et al, 2007; Daoud and Xin, 2008; Liu et al, 2018) and the crystal habits can significantly differ with preparation techniques (Diebold et al, 2003). The strategies include the particle-size and morphology control (Yang et al, 2008; Liu et al, 2011), the self-assembly (Cesano et al, 2008; Likodimos, 2018), the combination with other phases or structures (Cesano et al, 2012, 2015; Jain et al, 2014; Grissom et al, 2018), the TiO2 doping with metal/non-metal elements (Cravanzola et al, 2017; Humayun et al, 2018), as well as the embedding of quantum dots, heteroatoms, or heterostructures (Chen and Mao, 2007; Uddin et al, 2014; Jia et al, 2019) for tuning the optical and electronic properties
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