Dependence of TiO2 nanotube microstructural and electronic properties on water splitting

Freitas, Renato G.; Santanna, Maria Alice; Pereira, Ernesto C.

doi:10.1016/j.jpowsour.2013.11.067

Cited by 34 publications

(21 citation statements)

References 53 publications

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“…Compared to TiO 2 nanoparticles, TiO 2 nanotubes are widely used in water splitting due to their ordered tubular structure, strong ion-exchange ability, relatively longer lifetime of electron/hole pairs. [80][81][82][83] However, the power conversion efficiency from solar to hydrogen by TiO 2 nanotubes photo/photoelectrocatalytic water splitting is still low, mainly due to fast (in absolute terms) recombination of electron/hole pairs and inability to utilize visible light. Therefore, continuous efforts have been made to solve these problems, which will be discussed in section 4.…”

Section: Basic Mechanism Of Photo/photoelectro-catalytic Water Splittmentioning

confidence: 99%

One‐dimensional TiO₂ Nanotube Photocatalysts for Solar Water Splitting

et al. 2016

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Hydrogen production from water splitting by photo/photoelectron‐catalytic process is a promising route to solve both fossil fuel depletion and environmental pollution at the same time. Titanium dioxide (TiO2) nanotubes have attracted much interest due to their large specific surface area and highly ordered structure, which has led to promising potential applications in photocatalytic degradation, photoreduction of CO2, water splitting, supercapacitors, dye‐sensitized solar cells, lithium‐ion batteries and biomedical devices. Nanotubes can be fabricated via facile hydrothermal method, solvothermal method, template technique and electrochemical anodic oxidation. In this report, we provide a comprehensive review on recent progress of the synthesis and modification of TiO2 nanotubes to be used for photo/photoelectro‐catalytic water splitting. The future development of TiO2 nanotubes is also discussed.

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Section: Basic Mechanism Of Photo/photoelectro-catalytic Water Splittmentioning

confidence: 99%

One‐dimensional TiO₂ Nanotube Photocatalysts for Solar Water Splitting

et al. 2016

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“…Measurements were taken in θ-2θ configurations from 20° to 65°, with a step size of 0.2° min −1 . Additionally, microstructure analysis, percentage of anatase and rutile, and average crystallite sizes were realized with Rietveld refinement as already described by our research group elsewhere [22,23]. A UV-Vis spectrophotometer (Varian Cary 100) with an integrating sphere attachment DRA-CA-30I for diffuse reflectance measurements was used to establish the optical band gap.…”

Section: Materials Characterizationmentioning

confidence: 99%

Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route

Spada

Pereira

Montanhera

et al. 2017

J Mater Sci: Mater Electron

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some distinct properties of TiO 2 , among which high redox potential, high chemical stability, low cost, and no toxicity stand out. These properties depend on many factors, such as the crystal structure, crystallite size, particle shape, and specific surface area, which are also strongly dependent on the method of synthesis. In terms of its crystal structure, TiO 2 exists as three important polymorphs: rutile (tetragonal), anatase (tetragonal), and brookite (orthorhombic) [6]. Rutile is the only stable phase; anatase and brookite are metastable at all temperatures and can be converted to rutile after heat treatment at high temperatures. Dependent on structure and particle size, each crystalline phase exhibits different physical properties best suited to different applications. For example, the anatase phase has a band gap of 3.2 eV, which means that it can be activated by UV light illumination. This is one of the reasons why it is often preferred for applications in photocatalysis [7-9]. The photocatalytic activity of TiO 2 originates from the presence of photo-generated electrons (e −) in the conduction band and holes (h +) in the valence band under irradiation with UV light. These holes have high oxidation power, thus they can easily react with adsorbed hydroxide ions to produce hydroxyl radicals, the main oxidizing species that are responsible for the photo-oxidation of organic compounds. The photocatalytic performance of anatase is considered superior to the more stable rutile (3.0 eV); this is attributed to a higher density of localized states and slower charge carrier recombination [10]. On the other hand, it has been reported that the presence of a small fraction of the rutile phase in intimate contact with anatase TiO 2 can improve its photocatalytic performance [11-13]. Pure anatase phase can be synthesized by many methods, such as the hydrothermal method, the sol gel method, the chemical method, and electrodeposition [14-19]. While all these methods have their own important benefits, the

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“…It is worth mentioning that estimated values for anatase samples are slightly lower than 3.2 eV which is typically reported for anatase phase in bulk [35]. Since the optical properties of the TiO 2 NTs depend on the geometric features of tubular structure [33], the difference most likely results from the specific morphology of the calcined sample. unmodified ones.…”

Section: Resultsmentioning

confidence: 80%

“…It can be seen that the values for reference as-anodized samples are decreasing with the prolonged anodization process and thus with the increasing length of the nanotubes (compare TiO 2 -15 and TiO 2 -60). This can be attributed to the more pronounced aggregation of the vacancies, which can act as trap states alongside the tubes and finally lead to the lowering of the band-to-band transition energy [33]. The same trend is preserved for reference crystalline TiO 2 NTs and the bandgap values do not change significantly in comparison to the as-anodized material.…”

Section: Resultsmentioning

confidence: 83%

“…Jung et al [42] have shown that vacuum annealing leads to a generation of n-donors in the form of oxygen vacancies, which results in increased emission at green wavelengths. In turn, the red PL from the recombination of electrons trapped on Ti 3+ ions with valence band or shallow-trapped holes extends into the red emission with a maximum between 600 and 650 nm [18,33]. The most accurate deconvolution was performed using parameters shown in Table 3.…”

Section: Resultsmentioning

confidence: 99%

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The In-Depth Studies of Pulsed UV Laser-Modified TiO2 Nanotubes: The Influence of Geometry, Crystallinity, and Processing Parameters

et al. 2020

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The laser processing of the titania nanotubes has been investigated in terms of morphology, structure, and optical properties of the obtained material. The length of the nanotubes and crystallinity, as well as the atmosphere of the laser treatment, were taken into account. The degree of changes of the initial geometry of nanotubes were checked by means of scanning electron microscopy, which visualizes both the surface and the cross-section. The phase conversion from the amorphous to anatase has been achieved for laser-treated amorphous material, whereas modification of calcined one led to distortion within the crystal structure. This result is confirmed both by Raman and grazing incident XRD measurements. The latter studies provided an in-depth analysis of the crystalline arrangement and allowed also for determining the propagation of laser modification. The narrowing of the optical bandgap for laser-treated samples has been observed. Laser treatment of TiO2 nanotubes can lead to the preparation of the material of desired structural and optical parameters. The usage of the motorized table during processing enables induction of changes in the precisely selected area of the sample within a very short time.

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Dependence of TiO2 nanotube microstructural and electronic properties on water splitting

Cited by 34 publications

References 53 publications

One‐dimensional TiO₂ Nanotube Photocatalysts for Solar Water Splitting

One‐dimensional TiO₂ Nanotube Photocatalysts for Solar Water Splitting

Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route

The In-Depth Studies of Pulsed UV Laser-Modified TiO2 Nanotubes: The Influence of Geometry, Crystallinity, and Processing Parameters

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Dependence of TiO2 nanotube microstructural and electronic properties on water splitting

Cited by 34 publications

References 53 publications

One‐dimensional TiO2 Nanotube Photocatalysts for Solar Water Splitting

One‐dimensional TiO2 Nanotube Photocatalysts for Solar Water Splitting

Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route

The In-Depth Studies of Pulsed UV Laser-Modified TiO2 Nanotubes: The Influence of Geometry, Crystallinity, and Processing Parameters

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One‐dimensional TiO₂ Nanotube Photocatalysts for Solar Water Splitting

One‐dimensional TiO₂ Nanotube Photocatalysts for Solar Water Splitting