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![Formation and characterization of the mesoporous TiO2 mesocrystals (FDU-19). (a) Schematic representation of the formation process of the olive-like mesoporous TiO2 mesocrystals through the evaporation-driven oriented assembly process. (b) SEM image of the mesoporous TiO2 mesocrystals FDU-19. (c) TEM images of the FDU-19 mesocrystals, recorded along the [010] axis. Inset (c) is the SAED pattern of an individual mesocrystal. (d) HRTEM image of an individual FDU-19 mesocrystal recorded along the [010] axis. Inset (d) is the structural model of the dislocation within mesocrystals FDU-19. (e) The electron paramagnetic resonance (EPR) spectra of the mesoporous mesocrystals FDU-19, recorded at room temperature (25 °C). (f) Ti2p XPS core-level spectra for FDU-19. (g) O1s XPS core-level spectra for FDU-19. (h) WXRD pattern of the mesoporous mesocrystals, compared to the standard anatase (space group I41/amd, JCPDS card No. 21-1272). (i) Nitrogen adsorption–desorption isotherms and pore size distributions (inset) of the olive-shaped mesoporous mesocrystals FDU-19. The pore size distributions are determined by the Barrett–Joyner–Halenda (BJH) model based on the respective absorption branches.](publication/283908349/figure/fig5/AS:342437609394177@1458654896146/Formation-and-characterization-of-the-mesoporous-TiO2-mesocrystals-FDU-19-a.png)
Formation and characterization of the mesoporous TiO2 mesocrystals (FDU-19). (a) Schematic representation of the formation process of the olive-like mesoporous TiO2 mesocrystals through the evaporation-driven oriented assembly process. (b) SEM image of the mesoporous TiO2 mesocrystals FDU-19. (c) TEM images of the FDU-19 mesocrystals, recorded along the [010] axis. Inset (c) is the SAED pattern of an individual mesocrystal. (d) HRTEM image of an individual FDU-19 mesocrystal recorded along the [010] axis. Inset (d) is the structural model of the dislocation within mesocrystals FDU-19. (e) The electron paramagnetic resonance (EPR) spectra of the mesoporous mesocrystals FDU-19, recorded at room temperature (25 °C). (f) Ti2p XPS core-level spectra for FDU-19. (g) O1s XPS core-level spectra for FDU-19. (h) WXRD pattern of the mesoporous mesocrystals, compared to the standard anatase (space group I41/amd, JCPDS card No. 21-1272). (i) Nitrogen adsorption–desorption isotherms and pore size distributions (inset) of the olive-shaped mesoporous mesocrystals FDU-19. The pore size distributions are determined by the Barrett–Joyner–Halenda (BJH) model based on the respective absorption branches.
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Unprecedented olive-shaped mesoporous TiO2 mesocrystals (FUD-19) self-organized by ultrathin flake-like anatase nanocrystals show remarkable crystallite-interface reactivity and high photoconversion efficiency.
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... During this process, by regulating the evaporation rate of the solvent, the packing manner of monomicelles at the liquid-liquid interface can be changed, resulting in the formation of uniform olive-shaped 3D mesoporous TiO 2 mesocrystal (FDU-19). 32 More ...
Low‐dimensional mesoporous nanomaterials (LDMNs), which possess complementary properties in the mesoscale and nanoscale, have realized more technological potentials in a wide range of applications, in particular, catalysis. Although still in its infancy, the proposed monomicelles‐induced assembly (MIA) has been proved to be an emerging and powerful toolbox for the direct synthesis of LDMNs with well‐controlled mesostructures and architectures. This review starts from the developmental history of the MIA strategy and then discuss general protocols to fabricate the monomicelles. After that, manipulation of the monomicelles' assembly by well‐designed interfaces and confined spaces for the controllable fabrication of LDMNs are reviewed in detail. Then, catalytic applications, including thermal, photo‐ and electrocatalysis, of LDMNs are discussed critically based on the structure‐performance relationship. This review ends with a brief summary and further directions of the MIA strategy, paving the way for the synthesis of sophisticated mesoporous assemblies to achieve advanced functionalities.
... The Raman spectrum of TiO 2 NT shows five peaks, corresponding to E g , E g , B 1g , A 1g , and E g vibration modes of anatase TiO 2 , which is consistent with the literature [28][29][30]. Additionally, the anatase crystal structure of the TiO 2 nanotube was further confirmed by XRD [31][32][33] and TEM [28,33,34] results ( Figure S4). The Raman spectra of TiO 2 NT@Au NP composite are similar to that of the pristine TiO 2 NT, because Au (as a metal material) does not show Raman vibration peak. ...
... The Raman spectrum of TiO2 NT shows five peaks, corresponding to Eg, Eg, B1g, A1g, and Eg vibration modes of anatase TiO2, which is consistent with the literature [28][29][30]. Additionally, the anatase crystal structure of the TiO2 nanotube was further confirmed by XRD [31][32][33] and TEM [28,33,34] results ( Figure S4). The Raman spectra of TiO2 NT@Au NP composite are similar to that of the pristine TiO2 NT, because Au (as a metal material) does not show Raman vibration peak. ...
As a multifunctional material, TiO2 shows excellent performance in catalytic degradation and lithium-ion storage. However, high electron-hole pair recombination, poor conductivity, and low theoretical capacity severely limit the practical application of TiO2. Herein, TiO2 nanotube (TiO2 NT) with a novel double-layer honeycomb structure were prepared by two-step electrochemical anodization. Honeycombed TiO2 NT arrays possess clean top surfaces and a long-range ordering, which greatly facilitates the preparation of high-performance binary and ternary materials. A binary TiO2 nanotube@Au nanoparticle (TiO2 NT@Au NP) composite accompanied by appropriately concentrated and uniformly distributed gold particles was prepared in this work. Interestingly, the TiO2 nanotube@Au nanoparticle (TiO2 NT@Au NP) composites not only showed the excellent catalytic degradation effect of methylene blue, but also demonstrated large lithium-ion storage capacity (310.6 μAh cm−2, 1.6 times of pristine TiO2 NT). Based on the realization of the controllable fabrication of binary TiO2 nanotube@MoS2 nanosheet (TiO2 NT@MoS2 NS) composite, ternary TiO2 nanotube@MoS2 nanosheet@Au nanoparticle (TiO2 NT@MoS2 NS@Au NP) composite with abundant defects and highly ordered structure was also innovatively designed and fabricated. As expected, the TiO2 NT@MoS2 NS@Au NP anode exhibits extremely high initial discharge specific capacity (487.4 μAh cm−2, 2.6 times of pristine TiO2 NT) and excellent capacity retention (81.0%).
... At the same time, the common Ti 3+ peaks, such as that around 457.0 eV for Ti2p 1/2 , are not distinct [36,37]. In comparison, only Ti 3+ is observed for TiO 2 -based photocatalysts under light irradiation [38,39]. This indicates that the electrons generated from the upconversion of r-GQDs can be directly transferred to TiO 2 . ...
Utilization of infrared light in photocatalytic water splitting is highly important yet challenging given its large proportion in sunlight. Although upconversion material may photogenerate electrons with sufficient energy, the electron transfer between upconversion material and semiconductor is inefficient limiting overall photocatalytic performance. In this work, a TiO 2 /graphene quantum dot (GQD) hybrid system has been designed with intimate interface, which enables highly efficient transfer of photogenerated electrons from GQDs to TiO 2 . The designed hybrid material with high photogenerated electron density displays photocatalytic activity under infrared light (20 mW cm ⁻² ) for overall water splitting (H 2 : 60.4 μ mol g cat. ⁻¹ h ⁻¹ and O 2 : 30.0 μ mol g cat. ⁻¹ h ⁻¹ ). With infrared light well harnessed, the system offers a solar-to-hydrogen (STH) efficiency of 0.80% in full solar spectrum. This work provides new insight into harnessing charge transfer between upconversion materials and semiconductor photocatalysts and opens a new avenue for designing photocatalysts toward working under infrared light.
... Subsequently, many efforts have been made to prepare mesoporous semiconductors with more coherent frameworks, mainly by the hard-templating route. [13][14][15][16] Nonetheless, hard templates remain indispensable for creating regular pore structures, which significantly limits developing programmable coherent mesoporous frameworks with controllable anisotropy, as well as tailoring mesopore architectures and facets. 13,[17][18][19] Nowadays, nonclassical crystallization phenomena are attracting an increasing amount of interest because these processes are unprecedented in morphological and compositional freedom. ...
The understanding and control of the structural complexity of mesoporous semiconductors with single-crystal-like nature are both attractive and challenging. Here, we report a crystallization-driven epitaxial assembly from monomicelles to construct branched mesoporous TiO2 mesocrystals (m-TiO2 MCs) with coherent atomic domains. The star-shaped multipods are obtained by two-step evaporation with nanocrystal mediation, primarily consisting of arms along < 001 >, < 101 >, and < 111 > crystal directions. For each arm, ordered open mesochannels arrange in parallel along the growth direction. The m-TiO2 MC multipods have a surface area of ∼116 m²/g and single-crystal-like frameworks and are good hydrogen evolution photocatalysts. Under full-spectrum irradiation, the branched m-TiO2 MCs exhibit a hydrogen evolution rate of 8 mmol h⁻¹ g⁻¹, which is more than four times higher than that of commercial TiO2 P25. This crystallization-driven self-assembly approach may provide valuable insight into designing programmable mesoporous mesocrystals by controlling the oriented assembly of monomicelle building blocks.
... In this process, the crystallographic orientation of the nanocrystal building blocks can be controlled by the slow evaporation and confinement of the triblock copolymer hydrophilic boundary ( Fig. 4b and c). Later, by adjusting the evaporation temperature, ellipsoid hierarchically mesoporous TiO 2 mesocrystals could be obtained [84]. More recently, we have developed a coordination-mediated self-assembly method to precisely control the phase composition of the resultant hierarchically mesoporous TiO 2 spheres [85]. ...
Because of their low cost, natural abundance, environmental benignity, plentiful polymorphs, good chemical stability and excellent optical properties, TiO2 materials are of great importance in the areas of physics, chemistry and material science. Much effort has been devoted to the synthesis of TiO2 nanomaterials for various applications. Among them, mesoporous TiO2 materials, especially with hierarchically porous structures, show great potential owing to their extraordinarily high surface areas, large pore volumes, tunable pore structures and morphologies, and nanoscale effects. This review aims to provide an overview of the synthesis and applications of hierarchically mesoporous TiO2 materials. In the first section, the general synthetic strategies for hierarchically mesoporous TiO2 materials are reviewed. After that, we summarize the architectures of hierarchically mesoporous TiO2 materials, including nanofibers, nanosheets, microparticles, films, spheres, core-shell and multi-level structures. At the same time, the corresponding mechanisms and the key factors for the controllable synthesis are highlighted. Following this, the applications of hierarchically mesoporous TiO2 materials in terms of energy storage and environmental protection, including photocatalytic degradation of pollutants, photocatalytic fuel generation, photoelectrochemical water splitting, catalyst support, lithium-ion batteries and sodium-ion batteries, are discussed. Finally, we outline the challenges and future directions of research and development in this area.
... However,this has rarely been reported. [55][56][57][58] Herein, we report on the first synthesis of oxygen-deficient dumbbell-shaped anatase TiO 2Àx mesocrystals with nearly 100 %e xposed {101} facets (DTMCs) by mesoscale transformation in TiCl 3 /acetic acid (HAc) mixed solution ands ubsequent calcination under vacuum.T hese unique DTMCs displayed much higherp hotocatalytic activity towardr emoval of the model pollutants methyl orange (MO) and Cr VI than the corresponding truncated tetragonal bipyramidala natase nanocrystals enclosed by eight {101} facets and two {001}f acets (TNCs), anatasem esocrystals built from truncated tetragonal bipyramidal anatasen anocrystals (TTMCs), and anatasem esocrystals constructed by anatase nanocrystals with nearly 100 %e xposed {101} facets (TMCs). This suggests that the photoredox ability of anatase TiO 2 was noticeably enhanced upon fabricating an oxygen-deficient mesocrystalline architecture with nearly 100 %e xposed {101} facets. ...
... The aforementioned atomics tructures, illustrated by the HRTEM images, are in good agreement with the projected structure model of an ideal anatase crystal with exposed {101} facets along the [010] direction ( Figure 1i). On the basis of all the above observations, it can be reasonably concluded that unique dumbbell-shapeda natase TiO 2 mesocrystals with nearly 100 %e xposed {101} facets were successfully fabricated in the current reactions ystem.I ts hould be pointed out that althoughw ith the efforts of al arge number of research groups, anatase TiO 2 mesocrystals with platelet-like, [34,38,62] spindleshaped, [35,54,56,57] bipyramidal-shaped, [63] truncated-bipyramidalshaped, [55] spherical-shaped, [64,65] cubic-like, [45,66] and hollowstructured [44] morphologies have already been synthesized,t he realization of anataseT iO 2 mesocrystals with other specific morphologies still remains ag reat challenge. Herein, the successfuls ynthesis of dumbbell-shaped anataseT iO 2 mesocrystals with % 100 %e xposed {101} facets can shed light on the construction of hierarchical TiO 2 superstructures with desired morphologies and architectures, which can pave the way to furtheri mprovet he performance of TiO 2 materials in certain applications. ...
The development of hierarchical TiO2 superstructures with new morphologies and intriguing photoelectric properties for utilizing solar energy is known to be an effective approach to alleviate the serious problems of environmental pollution. Herein, unique oxygen‐deficient dumbbell‐shaped anatase TiO2−x mesocrystals (DTMCs) enclosed by nearly 100 % {101} facets were readily synthesized by mesoscale transformation in TiCl3/acetic acid (HAc) mixed solution, followed by calcination under vacuum. These mesocrystals exhibited much higher photoreactivity toward removing the model pollutants methyl orange and CrVI than truncated tetragonal bipyramidal anatase nanocrystals (TNCs), anatase mesocrystals built from truncated tetragonal bipyramidal anatase nanocrystals (TTMCs), and anatase mesocrystals constructed by anatase nanocrystals with nearly 100 % exposed {101} facets (TMCs), revealing that both the oxidation and reduction abilities of anatase TiO2 were simultaneously enhanced upon fabricating an oxygen‐deficient mesocrystalline architecture with about 100 % exposed {101} facets. Further characterization illustrated that such an enhancement of photoreactivity was mainly due to the strengthened light absorption, boosted charge carrier separation, and nearly 100 % exposed {101} facets of the oxygen‐deficient dumbbell‐shaped anatase mesocrystals. This work will be useful for guiding the synthesis of oxygen‐deficient ordered superstructures of metal oxides with desired morphologies and exposed facets for promising applications in environmental remediation.
... Radially oriented mesoporous anatase TiO 2 microspheres with single-crystal-like pore walls were produced after removal of the triblock copolymer templates finally (step 4). It is noteworthy that by simply adjusting the reaction parameters, mesoporous, single-crystal-like, olive-shaped, anatase TiO 2 mesocrystals constructed by ultrathin nanosheet subunits could also be synthesized [65]. In 2011, Tartaj's group developed a method based on inverse microemulsions to produce sub-100 nm sphere-like mesocrystalline nanostructures, which involved a two-stage temperature program [132]. ...
... Radially oriented mesoporous anatase TiO2 microspheres with single-crystal-like pore walls were produced after removal of the triblock copolymer templates finally (step 4). It is noteworthy that by simply adjusting the reaction parameters, mesoporous, single-crystal-like, olive-shaped, anatase TiO2 mesocrystals constructed by ultrathin nanosheet subunits could also be synthesized [65]. ...
... At the same time, this kind of doping also improves the electroconductivity of TiO 2 , thereby facilitating charge transportation within TiO 2 particles [162,164,167]. In this regard, great efforts have been made toward preparing oxygen-deficient/Ti 3+ self-doped TiO 2 mesocrystals [65,136,150,168]. A good example in this area is that Zhao's group reported a facile evaporation-driven oriented assembly route combined with post thermal treatment in N 2 atmosphere to fabricate ultrathin-nanosheet-assembled olive-shaped mesoporous anatase TiO 2 mesocrystals ( Figure 13) [65]. ...
Hierarchical TiO2 superstructures with desired architectures and intriguing physico-chemical properties are considered to be one of the most promising candidates for solving the serious issues related to global energy exhaustion as well as environmental deterioration via the well-known photocatalytic process. In particular, TiO2 mesocrystals, which are built from TiO2 nanocrystal building blocks in the same crystallographical orientation, have attracted intensive research interest in the area of photocatalysis owing to their distinctive structural properties such as high crystallinity, high specific surface area, and single-crystal-like nature. The deeper understanding of TiO2 mesocrystals-based photocatalysis is beneficial for developing new types of photocatalytic materials with multiple functionalities. In this paper, a comprehensive review of the recent advances toward fabricating and modifying TiO2 mesocrystals is provided, with special focus on the underlying mesocrystallization mechanism and controlling rules. The potential applications of as-synthesized TiO2 mesocrystals in photocatalysis are then discussed to shed light on the structure–performance relationships, thus guiding the development of highly efficient TiO2 mesocrystal-based photocatalysts for certain applications. Finally, the prospects of future research on TiO2 mesocrystals in photocatalysis are briefly highlighted.
... In addition, the PL intensity decreases andt hen increases at ac ritical temperature of 500 8C, due to reconstruction of the crystal microstructure of TMCs at high annealing temperatures.T he decrease in the PL intensity with annealing temperature can be attributed to the decrease in dislocation levels and increase in grain size;t his could indicate the highest photocatalytic activity for TMC-500. [23] The decrease in the PL intensity of TMCs with annealing temperature can also be attributed to the decrease in dislocation levelsa nd increase in grain size, which can be confirmed by HRTEM (see Figure 6, below). Defect sites can also act as the active sites for reactant molecules;t hus more defects can lead to ah igher photocatalytic activity.T herefore, the combined effect of the recombination of photoinduced carriers and the amount of defects is essential to the photocatalytic activity.D efect engineering, through regulation of the defect distribution,a mount, and species,c an achieve the optimum photocatalytic performance. ...
... [22][23][24][25][26][27][28][29] As other examples, the performances of photoelectrochemical reactions 30 or photovoltaic devices 31 can be improved by tuning the shape of TiO 2 nanostructures. However, designing and fabricating TiO 2 nanostructures with complex configurations remains rare, [32][33][34][35] which is mainly attributed to the rapid hydrolysis rate of Ti-containing precursors and the lack of understanding of wet-chemistry-synthesized oxide nanostructures. Thus, reliable approaches for constructing TiO 2 nanostructures with well-defined structural complexity and tunable configurability remain highly desirable. ...
... The sharp peak at 530.8 eV and broad peak at 532.7 eV are assigned to O-Ti bonds and O-H bonds, respectively, demonstrating massive Ti-OH groups on the surface of the mesoporous TiO 2 microspheres. 35 The Ti2p XPS spectrum ( Figure 3C) shows two peaks at 465.5 (Ti2p1/2) and 459.5 eV (Ti2p3/2), assigned to Ti 4+ oxidation states. In the thermogravimetry (TG) analysis ( Figure 3D), a weight loss of only 1.5% after 900 C is observed, which is attributed to the absorbed water and hydroxyl groups on the TiO 2 surface. ...
Mesoporous TiO2 nanomaterials have been investigated for decades; however, most endeavors have been focused on the exploration of their potentials in various applications, and the fundamental research for preparing mesoporous TiO2 in a highly controllable manner remains unfruitful. Herein, we report a facile pressure-driven oriented assembly approach to synthesize an unprecedented type of dehiscent mesoporous TiO2 microspheres with radial mesopore channels and oriented rutile crystallites. By varying the concentrated HCl amount, we have been able to produce TiO2 microspheres with well-controlled rutile/anatase phase ratio. By further manipulating the reaction conditions including solvent evaporation time and hydrothermal temperature, the oriented growth with tunable crevices can also be well manipulated. Such dehiscent mesoporous TiO2 microspheres have exhibited great permeability and excellent photocatalytic properties for H2 generation. We believe that the high structural complexity and predictability of this method offers great opportunities in enhancing the performance of TiO2-based materials. The development of porous materials and their applications has been in great demand recently. However, the progress in rational synthesis of porous semiconductors remains unproductive. Here, we have demonstrated a hydrothermal method to synthesize a novel type of mesoporous TiO2 microsphere with highly controllable structure. By regulating the synthetic conditions, the mesoporous TiO2 can be well controlled with oriented mesopores and lattices, tunable crystalline phase, and tailored open crevices. The resulting mesoporous TiO2 microspheres exhibit excellent penetration properties and photocatalytic activities, which is attributed to their unique mesostructures associated with accessible high surface area and particular architectures. Such a simple method, which is able to fabricate mesoporous TiO2 with controlled architectures and crystallites, is expected to be applied to produce numerous delicate nanostructures at moderate conditions for potential applications, such as catalysts, energy storage, and biosensors. We have demonstrated a facile hydrothermal approach to synthesize a novel type of mesoporous TiO2 material with highly controllable structure. By regulating the synthetic conditions, the mesoporous TiO2 can be well controlled with desired crystallites and architectures. The resulting mesoporous TiO2 exhibits excellent penetration properties and photocatalytic performance. These unique mesoporous TiO2 microspheres produced at moderate conditions could afford great opportunities in achieving high performance in various practical applications.
... High crystallinity and high porosity anatase TiO 2 samples were obtained after thermal treatment in air at 460°C for 30 min. Specifically, during annealing in air, the adjacent nanocrystal building blocks can be crosslinked by removing surfactant molecules and the increasing oriented attractive forces can further lead to in situ threedimensional crystallographic fusion to minimize the total system energy through reducing the high surface energy and eliminating the crystal defects, yielding mesoporous TiO 2 spherical nanobundles [20]. ...
Highly photocatalytically active anatase TiO 2 were synthesized by a solvothermal method using tetrabutyl titanate (TBT), citric acid, and ethanol as row material. The morphology and photocatalytic activity of titanium oxide have changed significantly with the presence of surfactants, such as cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and diethanolamine (DEA). Scanning electron microscope and X-ray powder diffraction results show that the synthesized products are anatase TiO 2 spherical particles with a micronanostructure. The crystal type of TiO 2 has no obvious change with the addition of different surfactants, but the morphology, size, and dispersion of the TiO 2 particles have changed to some extent. Among the three surfactants, CTAB is beneficial to reduce TiO 2 particle size and improve TiO 2 dispersion and agglomeration. DEA is favor to self-assembly the nanocrystals into spherical particles. Degradation of methyl orange photocatalyzed by TiO 2 prepared with CTAB as surfactant reaches 95.4% under ultraviolet light for 100 min. After five recycles, the catalyst did not exhibit significant loss of photocatalytic activity, confirming that the photocatalyst is essentially stable. This work indicates that the surfactant-assisted solvothermal method is an effective approach to improve the structure, morphology, and photocatalytic performance of TiO 2 . Moreover, the surfactants with various types can interact with the precursors of TiO 2 in different ways.
