TiO2 Nanocrystals Research Articles

Boosting Li-storage properties of conversion-type anodes for lithium-ion batteries via steric effect of intercalation-type materials: A case of MnCO3†

The conversion-type anodes have been widely investigated in lithium-ion batteries (LIBs), due to their high theoretical specific capacity. However, their rate capability and cyclic stability were suffered from large volume expansion and pulverization. Herein, we report a method to improve the electrochemical performance of conversion-type anodes by using the steric effect of intercalation-type materials, as was done in conversion-type MnCO3. The role of the intercalation-type TiO2 nanocrystals in the structural evolution of composite anodes was verified. It was found that TiO2 nanocrystals could form a good electrical contact with as-pulverized MnCO3 anode, and maintain their structural stability. Furthermore, the electrochemical analysis shows that TiO2 nanocrystals can provide fast electron transfer channels for the composites matrix, which is conducive to improving the rate capability of MnCO3 anode. Moreover, TiO2 nanocrystals can effectively avoid the aggregation of metal Mn nanocrystals by their steric effect. As a result, the composite anode showed better electrochemical properties than its counterpart MnCO3 by delivering 378 mA h g−1 at a current density of 1 A g−1 after 200 cycles. Different from previously reported methods, our strategy is simple and easy to scale. Importantly, our research provides a new insight for solving issues involved volume expansion and pulverization of conversion-type anodes.

Site Sensitivity of Interfacial Charge Transfer and Photocatalytic Efficiency in Photocatalysis: Methanol Oxidation on Anatase TiO2 Nanocrystals.

Photocatalytic oxidation of methanol on various anatase TiO2 nanocrystals was studied by in situ and time-resolved characterizations and DFT calculations. Surface site and resulting surface adsorbates affect the surface band bending/bulk-to-surface charge migration processes and interfacial electronic structure/interfacial charge transfer processes. TiO2 nanocrystals predominantly enclosed by the {001} facets expose a high density of reactive fourfold-coordinated Ti sites (Ti4c ) at which CH3 OH molecules dissociate to form the CH3 O adsorbate (CH3 O(a)Ti4c ). CH3 O(a)Ti4c localized density of states are almost at the valence band maximum of TiO2 surface, facilitating the interfacial hole transfer process; CH3 O(a)Ti4c with a high coverage promotes upward surface band bending, facilitating bulk-to-surface hole migration. CH3 O(a)Ti4c exhibits the highest photocatalytic oxidation rate constant. TiO2 nanocrystals enclosed by the {001} facets are most active in photocatalytic methanol oxidation.

Site Sensitivity of Interfacial Charge Transfer and Photocatalytic Efficiency in Photocatalysis: Methanol Oxidation on Anatase TiO2 Nanocrystals

AbstractPhotocatalytic oxidation of methanol on various anatase TiO2 nanocrystals was studied by in situ and time‐resolved characterizations and DFT calculations. Surface site and resulting surface adsorbates affect the surface band bending/bulk‐to‐surface charge migration processes and interfacial electronic structure/interfacial charge transfer processes. TiO2 nanocrystals predominantly enclosed by the {001} facets expose a high density of reactive fourfold‐coordinated Ti sites (Ti4c) at which CH3OH molecules dissociate to form the CH3O adsorbate (CH3O(a)Ti4c). CH3O(a)Ti4c localized density of states are almost at the valence band maximum of TiO2 surface, facilitating the interfacial hole transfer process; CH3O(a)Ti4c with a high coverage promotes upward surface band bending, facilitating bulk‐to‐surface hole migration. CH3O(a)Ti4c exhibits the highest photocatalytic oxidation rate constant. TiO2 nanocrystals enclosed by the {001} facets are most active in photocatalytic methanol oxidation.

Superhydrophobic Sands for the Preservation and Purification of Water

Sand, a cheap and naturally abundant particulate material, was modified with photocatalytic and hydrophobic coatings to reduce evaporation loss and facilitate the purification of water. The first-level photocatalytic coatings (TiO2 or ZnO nanocrystals) rendered nanoscale roughness on the surface of the sand. The additional second-level hydrophobic coating of a self-assembled monolayer of octyltrimethoxysilane (OTS) made the sand particles superhydrophobic because of the nanoscale roughness imposed by the nanocrystals. The superhydrophobic sand particles, floating on the free surface of water due to their superhydrophobicity, significantly reduced the evaporation loss of water by 60%–90% in comparison to an uncovered water surface. When the outer hydrophobic coatings are weathered or disengaged, the inner photocatalytic coatings become exposed to water. Then, the sand particles act as photocatalysts to degrade the contaminants in water under solar radiation.

Application of TiO2 hollow spheres and ZnS/SiO2 double-passivaiting layers in the photoanode of the CdS/CdSe QDs sensitized solar cells for the efficiency enhancement

In this work quantum dot sensitized solar cells (QDSCs) with multilayer photoelectrodes were fabricated and investigated. The co-sensitization was carried out by CdS and CdSe quantum dots (QDs) layers and double passivation was performed by ZnS and SiO2 electron blocking films. Two kinds of TiO2 scaffolds in the forms of transparent TiO2 nanocrystals (NCs) and a double layer TiO2 NCs/TiO2 hollow spheres (HSs) were fabricated and utilized. The main CdSe sensitizing layer was deposited through a fast and effective chemical bath deposition (CBD) method in different conditions. Finally, a wide range of photoanodes were fabricated and applied in a conventional structure of the QDSCs. The results showed the maximized PCE of 3.65% for the QDSC with TiO2 NCs/CdS/CdSe (9 min)/ZnS/SiO2 photoelectrode. This efficiency was enhanced about 65% compared to the reference cell with CdSe and SiO2 free photoanode. For the double layer mesoporous TiO2 sublayer, it was shown that the QDSC with TiO2 NCs/HSs/CdS/CdSe (9 min)/ZnS/SiO2 multilayer photoanode demonstrated the maximum PCE of 6.1%. The mentioned efficiency was increased about 82%, 37% and 31% compared to the corresponding reference cells with TiO2 NCs/HSs/CdS/ZnS and TiO2 NCs/HSs/CdS/ZnS/SiO2 and TiO2 NCs/HSs/CdS/CdSe (9 min)/ZnS photoelectrodes, respectively.

Phonon confinement and size effect in Raman spectra of TiO2 nanocrystal towards Photocatalysis Application

Phonon confinement and size effect in Raman spectra of TiO2 nanocrystal towards Photocatalysis Application

Reductant-free synthesis of oxygen vacancies-mediated TiO2 nanocrystals with enhanced photocatalytic NO removal performance: An experimental and DFT study

Herein, we developed a reductant-free strategy to fabricate oxygen vacancies-mediated (OVs-mediated) TiO2 nanocrystals. Different from the conventional reduction process, OVs-mediated TiO2 were synthesized via a low-temperature calcination in nitrogen atmosphere assisted solvothermal process. Firstly, the pristine TiO2 was synthesized by solvothermal process using the tetra-n-butyl titanate as precursor and ethanol as solvent. Because of the organic precursor and solvent, the obtained pristine TiO2 was inevitably carbon-doped. Then, low-temperature calcination in nitrogen atmosphere instead of reducing gas atmosphere was carried out to introduce the OVs into the pristine TiO2. Experimental and theoretical results revealed that the intrinsic carbon-doping was conducive to the formation of OVs. Moreover, the obtained OVs-mediated TiO2 exhibited outstanding photocatalytic performance in comparison with the commercial P25, which was attributed to the crucial roles of OVs. This work not only provided a novel synthesis of OVs-mediated TiO2, but also contributed to understanding the crucial roles of OVs.

Microwave-assisted synthesis of titania-amorphous carbon nanotubes/amorphous nitrogen-doped carbon nanotubes nanohybrids for photocatalytic degradation of textile wastewater.

The synthesis of TiO2 nanohybrids fabricated using amorphous carbon nanotubes (aCNTs) and amorphous nitrogen doped carbon nanotubes (aNCNTs) via a microwave-assisted hydrothermal method is reported. The photocatalytic removal of Reactive Red 120 (RR 120) and organics from industrial textile wastewater using these nanohybrids is discussed. The synthesis process was shown to promote the removal of nano graphitic flakes from the outer walls of the aNCNTs and aCNTs and subsequent incorporation of these carbonaceous materials into TiO2 nanocrystals as such enabling a stronger interaction between the TiO2 and the carbonaceous material. This enabled the production of a surface plasmon resonance on the TiO2 and NTiO2 nanocrystals. The carbon residue was confirmed to be aCNTs and aNCNTs by TGA and DTA analyses. XPS analysis for the TiO2–aNCNT nanohybrids confirmed the C and N doping of TiO2 due to the amorphous residues from the aNCNTs. In addition, XPS and FTIR spectroscopic analysis confirmed the presence of surface oxygen-based groups. TEM micrograph analysis showed that aCNTs and aNCNTs promote the formation of monodispersed and small TiO2 particles; all below 7.4 nm. The NTiO2–aNCNT nanohybrids have the lowest energy band gap at 2.97 eV and the lowest PL intensity. The TiO2–aNCNT nanohybrids had superior adsorptive (98.2%) and photocatalytic (99%) removal for 20 ppm RR 120 dye solution at k1app 3.44 × 10−2 min−1. Lastly, all the nanohybrids demonstrate the formation of visible-light absorbing intermediates from VAT-dyed textile wastewater. The work demonstrates the possibility of the use of these nanohybrids to derive new products through photocatalytic nanohybrids.

Mesoporous (101)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies for boosting photocatalytic hydrogenation of nitrobenzenes

Mesoporous (101)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies showed significantly enhanced activity for photocatalytic hydrogenation of nitrobenzenes to anilines in water medium under visible-light irradiation.

Mesoporous (001)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies for boosting photocatalytic selective conversion of aromatic alcohols

Mesoporous (001)-TiO2 nanocrystals with tailored Ti3+ and surface oxygen vacancies exhibited remarkably boosted photoactivity for selective conversion of aromatic alcohols to carbonyl compounds in water medium under visible-light irradiation.

Photocatalytic activity of undoped and Mn- and Co-doped TiO2 nanocrystals incorporated in enamel coatings on stainless steel

New catalysts composed of undoped and transition metal-doped TiO2 nanocrystals incorporated in enamels on stainless steel show potential applications for pollutant photodegradation.

Hydroxyl-enriched highly crystalline TiO2 suspensible photocatalyst: facile synthesis and superior H2-generation activity.

A hydroxyl-enriched highly crystalline TiO2 suspensible photocatalyst was synthesized via a facile ethanol-controlled hydrolysis and following an in situ crystallization method. In the absence of any cocatalysts, the resultant photocatalyst displayed a clearly higher H2-evolution rate (622 μmol h-1 g-1) than the well-known commercial P25 TiO2 (190 μmol h-1 g-1).

Crystal-plane effects of anatase TiO2 on the selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts

Supported Ir/TiO2 catalysts with the anatase TiO2 nanocrystals exposing {101}, {100} and {001} planes were tested for selective hydrogenation of crotonaldehyde. The Ir/TiO2-{101} catalyst dominantly exposing {101} plane gave a initial reaction rate of 166.1 μmol gIr-1 s−1 at 80 °C and a turnover frequency of crotyl alcohol formation of 0.022 s−1, which is 5 and 7 times respectively higher than those obtained on the Ir/TiO2-{001} catalyst dominantly exposing {001} plane even though they have similar Ir particle sizes (ca. 1.3 nm). The reaction behaviors were related to the surface oxygen vacancy, which served as surface acid sites and provide adsorption sites for CO bond in the CRAL molecule. Therefore, the higher concentration of oxygen vacancy in the Ir/TiO2-{101} accounted for the improved performance compared to the Ir/TiO2-{001}. However, strong adsorption of crotonaldehyde and/or products on the catalyst surface, as well as the CO poisoning via decarbonylation of crotonaldehyde, were the main reasons for the catalyst deactivation.

Retraction Note to: Site Specific Interaction Between TiO2 Nanoparticles and Phenanthrimidazole-A First Principles Quantum Mechanical Study.

Understanding the interaction between the nanomaterials and bioactive molecules are of current interest due to the potential application of nanomaterial in biomedical field. The structural, electronic and optical properties of newly synthesised fluorophore 2-(4-methoxynaphthalen-1-yl)-1-phenyl-1H-phenanthro[9.10-d]imidazole have been investigated in detail. The imidazole absorbs strongly on the surface of TiO2 nanocrystals probably because of the chemical affinity of azomethine nitrogen atom of the imidazole, resulting in lowering the HOMO and LUMO energy levels. The TEM, SEM and EDX spectra confirm the adsorption of imidazole on the surface of TiO2 nanocrystals. The growth behavior and stability of small stoichiometric (TiO2)n clusters have been analysed by using density functional theory which reveals that clusters prefers three-dimensional structures. In addition, the interaction between the ground state structure of the (TiO2)n cluster and a single imidazole molecule have been studied. The calculated binding energy (Eb) and the energy gap (Eg) indicate that the imidazole molecule preferably binds to the Ti atom of the (TiO2)n clusters through its azomethine nitrogen atom; the binding energy is in range 5.24–7.89 eV. In order to understand the binding interaction with DNA docking study has been carried out.

Intrinsic carbon-doping induced synthesis of oxygen vacancies-mediated TiO2 nanocrystals: Enhanced photocatalytic NO removal performance and mechanism

Herein, we developed a facile approach to fabricate oxygen vacancies-mediated TiO2 (OVs-TiO2) nanocrystals via an intrinsic carbon-doping induced strategy. The intrinsic carbon-doped TiO2 nanocrystals were firstly synthesized by water-controlled-releasing solvothermal (WCRS) process using ethanol, acetic acid and titanium tetraisopropoxide (TTIP) as precursors. The carbon-doped TiO2 was calcined at 325 °C under N2 atmosphere to introduce the OVs. The obtained OVs-TiO2 displayed outstanding photocatalytic NO removal performance under visible light irradiation (λ˃510 nm), in comparison with the commercial P25. With the aid of DFT calculations, we revealed that the intrinsic carbon-doping was beneficial for the formations of OVs in carbon-doped TiO2. Moreover, the OVs played crucial roles in improving light absorption, facilitating charge separation, and activating surface reactions to enhance the photocatalytic NO removal performance.

Tailoring the NIR range optical absorption, band-gap narrowing and ferromagnetic response in defect modulated TiO2 nanocrystals by varying the annealing conditions

In this investigation, we report the influence of oxygen vacancy and Ti3+ related defects in the visible and IR range absorption as well as on the bandgap and magnetism of TiO2 nanocrystals annealed in different atmospheres. The X-ray diffraction patterns and Raman spectra indicate anatase phase formation and TEM analysis confirm the highly crystalline nature of TiO2 nanocrystals with a particle size of around ~ 9–12 nm. Significant absorption in the visible and IR region along with much-reduced bandgap is observed in argon, hydrogen and vacuum annealed samples. These samples exhibit strong visible photoluminescence associated mostly with oxygen vacancies. The room temperature ferromagnetism observed in argon annealed TiO2 nanocrystals is explained by taking into consideration the concept of bound magnetic polarons. Hence, this study reports the formation of TiO2 nanocrystals with extended absorption in visible as well as in IR region and ferromagnetism at room temperature which could have potential applications for future technologies.

Transparent Coating with TiO2 Nanorods for High-performance Photocatalytic Self-cleaning and Environmental Remediation

High-performance self-cleaning coatings are highly desired by the industry and market. Herein, we synthesized two kinds of ultrafine TiO2 nanocrystals, one is anatase dots with a diameter of 5 nm, and the other is rutile rods with 1.5 nm in width and 7 nm in length. The prepared TiO2 nanocrystal is highly dispersed and stable in water over a month. The coating can be fabricated via a simple spraying method, displaying excellent optical properties and photocatalytic performance on self-cleaning and surrounding environment remediation. The transmittance of glass remains 80%–90% for visible and near-infrared light after 30 cycles of spray. RhB solution(50 mg/L) was applied to the coating surface and form a solid RhB layer was formed, which can be completely removed in 30 min’s light irradiation. RhB aqueous solution(100 mL, 5 mg/L) was purified after 180 min by a 10 cm×10 cm glass, on which the coating was sprayed 30 times. The concentrations of formaldehyde and PM 2.5 in surrounding air displayed a significant decrease along 50 min’s monitoring. This high-performance coating shows great potential for constructing functional coating on various substrates for industrial applications.

Nd3+ doped TiO2 nanocrystals as self-referenced optical nanothermometer operating within the biological windows

In this work, we report a potential optical nanothermometer (NTh) based on Nd3+ doped TiO2 nanocrystals, operating within the biological windows. The Nd3+ emissions at around 900, 1060, and 1340 nm were used upon excitation at 808 nm. The fluorescence intensity ratio (FIR) corresponding to the emissions at 1060 nm and 1340 nm (FIR = I1060 nm/I1340 nm) was investigated as a function of the temperature in the range of 300−343 K. In addition, the effect of the Nd3+ ions concentration and influence of the crystalline phase on the luminescence and the relative thermal sensitivity were presented. As a result, it was found that TiO2 nanocrystals doped with 10 wt% of Nd3+ ions and associated with the brookite phase has the highest luminescence emission and relative thermal sensitivity compared to other samples investigated here and in previous literature. The maximum value obtained to the relative thermal sensitivity was 0.86 % K−1, which is high comparatively with other ones of Nd3+ doped systems, and minimum thermal resolution of ∼1 K. This information together with the biocompatibility of TiO2 nanocrystals, and excitation and emissions wavelengths lying within the biological windows, favor potential applications in fluorescence and thermal imaging of biological systems.

Free-standing hybrid films comprising of ultra-dispersed titania nanocrystals and hierarchical conductive network for excellent high rate performance of lithium storage

The construction of advanced electrode materials is key to the field of energy storage. Herein, a free-standing anatase titania (TiO2) nanocrystal/carbon nanotube (CNT) film is reported using a simple and scalable sol-gel method, followed by calcination. This unique free-standing film comprises ultra-small TiO2 nanocrystals (∼ 5.9 nm) and super-aligned CNTs, with ultra-dispersed TiO2 nanocrystals on the surfaces of the CNTs. On the one hand, these TiO2 nanocrystals can significantly decrease the diffusion distance of the charges and on the other hand, the cross-linked CNTs can act as a three-dimensional (3D) conductive network, allowing the fast transport of electrons. In addition, the film is free-standing, without requiring electrode fabrication and additional conductive agents and binders. Owing to these above synergistic effects, the film is directly used as an anode in Li-ion batteries, and delivers a high discharge capacity of ∼ 105 mAh·g−1 at high rate of 60 C (1 C = 170 mA·g−1) and excellent cycling performance over 2,500 cycles at 30 C. These results indicate that the free-standing anatase TiO2 nanocrystal/CNT film affords a superior performance among the various TiO2 materials and can be a promising anode material for fast-charging Li-ion batteries. Moreover, the TiO2/CNT film exhibits an areal capacity of up to 2.4 mAh·cm−2, confirming the possibility of its practical use.

Spray‐Dried TiO2(B)‐Containing Photocatalytic Glass‐Ceramic Nanobeads

AbstractGlass‐ceramic nanospheres of molar composition 0.83 SiO2 · 0.17 TiO2 are produced by the sol‐gel spray‐drying method followed by controlled heat treatments up to 1200 °C. TiO2(B) and anatase nanocrystals are precipitated in the glassy matrix: the latter phase gradually predominates with increasing ceramization temperature and time, in parallel to an overall increase in crystal sizes. The nanospheres exhibit evident photocatalytic activity under UV‐A irradiation, especially at annealing stages involving a comparatively higher amount of TiO2(B) and smaller crystals. The occurrence of TiO2(B) in this simplified binary glass‐ceramic material underlines the key role of this phase in the dynamics of crystallizing TiO2‐bearing silicate melts.