KR20150093527A - Steam-assisted Facile Low-temperature Crystallization and Interconnection of metal oxide - Google Patents

Abstract

The present invention relates to a method for preparing a structure in which crystal particles of mesopore metal oxide are interconnected, the method comprising: a step A of preparing a precursor solution containing a metal oxide source, a mesopore-directing agent, an acid catalyst, and a solvent; a step B of evaporating the solvent from the precursor solution, wherein the mesopore-directing agent and a hydrolyzed metal source are self-assembled to form a mesopore within the metal oxide by means of the mesopore-directing agent and to form a metal oxide structure in which the mesopore-directing agent is filled and cohered in the mesopore; a step C of carbonizing the mesopore-directing agent filled in the mesopore; a step D of maintaining the mesophore structure by treating the same with steam at a lower temperature than the carbonizing temperature of the step C to interconnect metal oxide nanoparticles into a polysrystalline form in which the metal oxide nanoparticles are fused; and a step E of removing the cabonized aggregates within the mesopore. According to the present invention, the method for low temperature crystallization and interconnection of metal oxide by a steam treatment is capable of forming a highly aligned crystalline metal oxide structure having great reproducibility, thereby expanding the production scale.

Description

Steam-assisted Facile Low-temperature Crystallization and Interconnection of Metal Oxide "

The present invention relates to a method for crystallizing and interconnection of metal oxides at low temperatures by steam treatment.

Since the discovery of mesoporous silica like MCM-41 by Mobil scientists in the early 1990s, the synthesis of many well-ordered mesoporous MCM family members with high surface area has been reported so far. These porous materials with homogeneous porosity and interconnected channels exhibit tremendous selectivity and thus have great potential for applications as catalysts, nanocomposites, chemical sensors, nano-reactors, sorbents and drug release modifiers have. By modulating channel connections and pore networks, a variety of porous materials have been synthesized and used in selective applications. For example, two-dimensional (2-D) hexagonal channel structure MCM-41 and SBA-3 prepared using a linear alkyl chain surfactant and Pluronic P123 SBA-15 was used for the preparation of nanoparticles, nanowires and nanofibers. Materials of three-dimensional (3-D) network structure, such as MCM-48, SBA-1 prepared using CTAB and SBA-6, SBA-16 or FDU based materials synthesized using block copolymers, Respectively. Many variations of the StOber method have been used to produce hierarchical porous structures suitable for controlled release of therapeutic molecules and efficient catalytic effects.

Porous metal oxides have also been used as electrode materials in the energy field. Generally, the electrode material should have both good electronic conductivity and ionic conductivity. In general electrode materials, ionic conductivity is lower than electron conductivity. However, in the case of a porous electrode material, it is possible to transfer ions to the interior of the particle, thereby substantially reducing the ion movement path. It is possible to achieve similar effects to the porous electrode material by using a nano material which exhibits the same effect. However, since the contact resistance between particles is high and it is difficult to manufacture the electrode, it is difficult to apply it.

The porous metal oxide can be mentioned a case example is applied as the electrode material that is typically between the _{MnO 2, LiCoO 2, LiNiO 2} , LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , such as applying a positive electrode material of a lithium secondary battery, and , RuO ₂ and NiO in electrochemical capacitors have been applied as pseudocapcitance materials. In addition, a porous metal oxide is also used as a TiO ₂ semiconductor electrode of a nickel oxide or cobalt oxide anode material and a dye-sensitized solar cell of a solid oxide fuel cell, a molten carbonate fuel cell, and a hydrogenated boron fuel cell.

As a method for producing such a porous metal oxide, a sintering method, a template method and the like are widely used.

The sintering method is the most commonly used method in the production of porous oxides. In most cases, it is difficult to produce powder in the form of a powder.

The template method is a method widely used for manufacturing a porous material having a mesopore of 50 nm or less, but generally has a disadvantage in that the process cost is high and mass production is difficult. For example, a porous oxide is produced by converting a template space into a pore by heat treatment using a surfactant having a long chain as a template.

On the other hand, the oxides studied so far are TiO ₂ , SnO ₂ , ZnO, Nb ₂ O _{5 and} so on. Among them, TiO ₂ (Titania) is the most efficient material. TiO ₂ is known to have four phases: a stable brookite phase, an anatase phase, a stable rutile phase at high temperature, and a TiO ₂ ( B). The ruta crystal structure has a disadvantage in that the activity of the photocatalyst is not superior to that of the anatase crystal structure because the reactivity of the reactant is low compared with the crystal structure of the anatase phase and the recombination rate of electrons and holes generated by light is slow .

As described above, anatase is one of the most important crystalline metal oxides and has been widely used in industry for various applications such as catalysts, catalyst supports, etc. With high phase purity and high surface area, highly ordered crystalline Its usefulness is best when it is manufactured in the thehighly ordered crystalline mesoporous form. Thus, there has been constant effort to develop methods for making such forms (Table 1, below).

[Table 1]

Although there have been some success stories over the past 15 years, the synthetic processes typically employed still lack reproducibility and scalability. Considering the importance of the material and the recent widespread demands for bulking the material, the two problems described above must be resolved as soon as possible.

The present invention provides a new concept approach to manufacturing metal oxide structures through reproducible processes that can increase production scale.

A first aspect of the present invention is a process for the preparation of a precursor solution comprising a metal oxide source, a mesopore-directing agent, an acid catalyst and a solvent; Wherein the mesoporous-inducing agent and the hydrolyzed metal source undergo self-assembly to form a mesopore in the metal oxide by the mesoporous-inducing agent, and wherein the mesoporous-inducer B) forming a filled and agglomerated metal oxide structure; A step C for carbonizing the mesopore-inducing agent filled in the mesopore; A step D for intermingling the metal oxide nanoparticles into a fused polycrystalline form while maintaining the mesopore structure by steam treatment at a temperature lower than the carbonization temperature of the C stage; And E step of removing the carbonized aggregates in the mesopore, wherein the mesoporous metal oxide crystal grains are interconnected.

At this time, the metal oxide may be TiO ₂ , and the mesoporous metal oxide crystal grains may be anatase.

Further, a second aspect of the present invention provides a structure in which mesoporous metal oxide crystal grains are interconnected by a method according to the second aspect of the present invention.

In a third aspect of the present invention, there is provided a method for manufacturing a metal oxide structure in which crystalline metal oxide particles are interconnection, comprising the steps of treating an amorphous metal oxide with steam to crystallize the metal oxide, And interconnection of the metal oxide structures.

Hereinafter, the present invention will be described in detail.

The following steps were performed to produce the conventionally highly ordered anthracite of the thehighly ordered crystalline mesoporous form.

The first step is to prepare a suitable precursor solution by mixing a titanium source, a suitable mesopore-directing agent (MPDA, see Table 1), an acid catalyst and alcohol as a solvent. The second step is to slowly evaporate the solvent from the precursor solution at a temperature of 25-40 < 0 > C for 24 hours. The second step has been referred to as evaporation-induced self-assembly (EISA). During the EISA step, the MPDA and the hydrolyzed Ti source undergo self-assembly to become the amorphous TiO ₂ of the mesoporous, and the MPDA filled in the mesoporous aggregates. The second stage is very reproducible and performs very well. The third stage is a carbonization (CBN) stage in which the MPDA aggregates filled in the mesophase become mechanically stiffer carbon agglomerates, the crystallization step of amorphous TiO ₂ into anatase nanoparticles of the crystal structure, and the mesoporous structure While the nanoparticles are intercon- nected into a fused polycrystalline form. Thus, the third step may be referred to as the carbonization / crystallization / interconnect step. The third step was carried out in an inert atmosphere with an applied temperature range of 600 to 700 ° C. The fourth step is the step of removing carbon aggregates (C-removal). The fourth step is usually carried out at 450 < 0 > C in the atmosphere. After the C-removal step, the mesoporous structure is frequently disintegrated into individual anatase nanocrystals or mesoporous anatase with very small domains. However, the present inventors have found that this collapse problem arises from the third step.

In addition, through experiments of the present inventors, it has been confirmed that the carbonization process is sufficient at 350 ° C, and that 600 ° C to 700 ° C is unnecessarily high. Further, from the viewpoint of crystallizing the amorphous TiO ₂ into an anatase, the temperature of 600 to 700 ° C is too high, and the anatase starts to transfer phase to rutile at ~ 550 ° C, which is not preferable. On the other hand, in terms of the melting point of anatase (1,835 ° C for bulk), the temperature is too low to induce interconnected or sintered anatase nanocrystals to an integrated mesoporous anatase. Therefore, this requires a new concept approach to the carbonization / crystallization / interconnection step, since the temperature 600 to 700 ° C applied during the carbonization / crystallization / interconnection step is too high / too high / too low for each process.

Therefore, to solve the above problems, the present inventors have found that by performing the carbonization step independently at 350 ° C and concurrently performing the crystallization / interconnecting steps under the aid of steam at 150 ° C, a large scale (10-20 g ), And the present invention is based on this.

Usually this interconnecting step is difficult with annealing at 600-700 ° C. We have found that the low temperature carbonation induces the presence of residual acid in the carbonized mesoporous TiO ₂ and crystallization of the amorphous TiO ₂ into anatase by residual-acid catalytic activity in the presence of steam is associated with successful low temperature crystallization / interconnection Analogy.

Further, by carrying out the straightforward and mild steps according to the present invention, the present inventors could obtain a mesophase anatase having a high crystallinity on a 12 g scale without any problem (Example 1). We have also found that the process scale can be increased by a factor of 4 (~ 50 g scale). This shows that the method according to the present invention is reproducible and scalable. Fig. 2 schematically shows an example of a novel process according to the present invention.

In other words, the present invention relates to a method for manufacturing a metal oxide structure in which crystalline metal oxide particles are intercon- nected, steam-treating the amorphous metal oxide to crystallize the metal oxide and simultaneously intercon- nect the metal oxide crystal grains . Preferably, the steaming treatment is carried out under an acid catalyst.

A method of manufacturing a structure in which mesoporous metal oxide crystal grains are interconnected according to the present invention by applying the same

A preparation of a precursor solution containing a metal oxide source, a mesopore-directing agent, an acid catalyst and a solvent;

Wherein the mesoporous-inducing agent and the hydrolyzed metal source undergo self-assembly to form a mesopore in the metal oxide by the mesoporous-inducing agent, and wherein the mesoporous-inducer B) forming a filled and agglomerated metal oxide structure;

A step C for carbonizing the mesopore-inducing agent filled in the mesopore;

A step D for intermingling the metal oxide nanoparticles into a fused polycrystalline form while maintaining the mesopore structure by steam treatment at a temperature lower than the carbonization temperature of the C stage; And

And E step to remove carbonized agglomerates in the mesopore.

Among the metal oxides according to the present invention, the metals may be elements of Group II, Group III, and Group IV of the Periodic Table of the Elements. Non-limiting examples of the metal oxides include ruthenium oxide (RuO ₂ ), nickel oxide (NiO) (Fe ₂ O ₃ ), MnO ₂ , Co ₃ O ₄ , SnO ₂ , IrO ₂ , Al ₂ O ₃ , Copper oxide CuO), zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), lithium oxide (Li ₂ O), palladium oxide (PdO), silver oxide (Ag ₂ O), manganese oxide (MgO) ₃ ), titanium oxide (TiO ₂ ), platinum oxide (PtO ₂ ), or gold oxide (Au ₂ O ₃ ).

≪ Metal oxide source, Meso pupil - Induction agent ( mesopore - directing agent ), An acid catalyst, and a precursor solution containing a solvent,

The metal oxide source may be a metal precursor compound known in the art as a compound containing the metal. For example, a group consisting of Group V, Group III, Group IV metals, metal salts, metal oxides, metal chlorides, metal acetates, Group V and VI elements with or without a trimethylsilyl group attached, ≪ / RTI > Non-limiting examples include oxides, chlorides, acetates, fatty acid salts, phosphonates, thiolates of metals selected from one or more of titanium, zinc, cadmium, mercury, aluminum, gallium, indium, silicon, manganese, germanium and tin , And alkoxides, but is not limited thereto.

For example, non-limiting examples of the Ti source include titanium- (n) butoxide, titanium- (n) ethoxide, titanium- (n) isopropoxide, titanium- (n) propoxide, titanium tetraisopropoxide and the like side and TiCl _4. Non-limiting examples of the Si source include tetramethylorthosilicate, tetraethylorthosilicate, tetrapropylorthosilicate, tetrabutylorthosilicate, or mixtures thereof.

Structural directing agents act as templates for certain crystalline structures. Charge distribution, size and geometric shape of structure directing agents provide structure directing properties.

The mesoporous-inducer is a kind of structure directing agent, Neutral, anionic, cationic surfactant. For example, an alkylamine-based or ammonium alkyl halide-based surfactant can be used. For example, in the above alkylamine-based or ammoniumalkyl halide-based surfactants, the alkyl group may be a linear or branched alkyl group having 4 to 24 carbons. Specifically, a trialkylammonium alkyl halide such as tri (C1-6 alkyl) ammonium C10-30 alkyl bromide may be used as the ammonium alkyl halide surfactant. For example, CTAB (cetyltrimethylammonium bromide) But is not limited thereto.

In this example, HO (CH ₂ CH ₂ O) ₂₀ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₂₀ H (Pluronic P123) was used and Pluronic P123 was a kind of neutral surfactant .

The non-limiting concentration range of the mesoporous-inducing agent in the precursor solution is 0.01 mol to 1 mol, preferably 0.1 mol to 0.5 mol.

The acid catalyst may be an inorganic acid or an organic acid, and non-limiting examples of the inorganic acid include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, halogenated silane, and mixtures thereof. Non-limiting examples of the organic acid include acetic acid, chloroacetic acid, Such as dimethylmalonic acid, formic acid, propionic acid, glutaric acid, glycollic acid, maleic acid, malonic acid, toluenesulfonic acid, oxalic acid, and the like. The acid catalyst is preferably hydrochloric acid, sulfuric acid, phosphoric acid, or a mixture thereof.

The acid catalyst serves to control the rapid hydrolysis and condensation rate of the metal oxide precursor. Further, the dispersion and viscosity can be controlled by preventing the aggregation of the metal-containing particles due to the hydrogen ions (H ⁺ ) of the acid catalyst.

It is preferred that the solvent comprises water or a mixture of water and other liquids. Examples of such other liquids include hydrophilic organic solvents, and include lower aliphatic alcohols such as methanol, ethanol, isopropanol (IPA), n-butanol and isobutanol, ethylene glycol, ethylene glycol monobutyl ether, Ethylene glycol derivatives such as monoethyl ether, diethylene glycol, diethylene glycol derivatives such as diethylene glycol monobutyl ether, and diacetone alcohol. Further, one or more selected from the group consisting of these can be used. Further, one or more of toluene, quinilene, hexane, ethyl heptanoate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketoxime and the like may be used in combination with these hydrophilic organic solvents.

≪ Step B for evaporating the solvent from the precursor solution >

In step B where the solvent is evaporated from the precursor solution, the mesoporous-inducing agent and the hydrolyzed metal source undergo self-assembly to form mesopores in the metal oxide by the mesoporous-inducing agent, and mesoporous-induced Filled and agglomerated metal oxide structures are formed.

Step B is a fundamental step in forming a mesoporous metal oxide structure and is well known in the art and is highly reproducible and very well performed.

In the process of slowly hydrolyzing and polycondensation a metal oxide precursor at a low pH by a sol-gel synthesis method, for example, by varying the mesoporous-inducing agent amount and the reaction time and temperature, the degree of crosslinking of the mesoporous- By varying the surface structure of the particles, the pore size and the surface properties can be controlled. The inorganic material may be subjected to a maturing process, followed by heat treatment to remove the mesoporous-inducing agent and residues and improve the crystallinity.

The temperature of step B varies depending on the solvent used but can be carried out at a temperature of 25 to 40 ° C.

The reaction time can vary from 0.5 hour to 20 days. The reaction time is preferably 2 hours to 15 days, more preferably 40 to 50 hours.

When all the solvent has evaporated, the remaining solids can be dried.

≪ On meso pupil Filled Meso pupil - Inducer  C carbonization step>

The present invention is characterized by performing the carbonization step independently of the crystallization / interconnection steps. Thus, a high heat treatment temperature is not required to interconnect the metal oxide particles and a heat treatment is possible at a temperature low enough to carbonize the mesoporous inducing agent. Further, due to the low-temperature carbonization, it is possible to induce the acid catalyst to remain.

The temperature of the heat treatment at the time of carbonization differs depending on the mesoporous-inducing agent used, and the temperature of carbonization as long as it can carbonize the mesoporous-derivative is not particularly limited.

<Carbonization of the C-level Than temperature  Step D to Steam at Low Temperature>

The present invention is another feature of steam treatment at temperatures below the carbonization temperature by separating the crystallization / interconnecting step from the carbonization step.

Steam treatment can interconnect the metal oxide nanoparticles into a fused polycrystalline form while maintaining the mesoporous structure even at a low temperature which is much lower than the annealing temperature of a typical metal oxide (Embodiment 1). By the acid catalytic activity in the presence of steam, the amorphous metal oxide can be crystallized even at low temperatures, and the metal oxide particles can be interconnected.

Since step D is a highly reproducible step, a desired metal oxide structure can be produced on a large scale scale.

The preferred steam treatment temperature is 40 to 400 占 폚, preferably 80 to 150 占 폚.

< Meso pupil  Step E to remove the carbonized agglomerates>

The reaction can be carried out usually in the air or in the presence of oxygen, and the reaction temperature is not particularly limited as long as it can remove the carbonized mesoporous-derivative.

In addition, not only the crystallinity of the metal oxide can be further improved, but also the metal oxide is calcined to cause rearrangement of the pore system in the step E where carbonized aggregates in the mesopores are removed by the heat treatment, resulting in a more stable structure .

The method of low temperature crystallization and mutual bonding of metal oxides by steam treatment according to the present invention can form a highly aligned crystalline metal oxide structure and is highly reproducible so that the production scale can be increased.

Figure 1, EISA after (ae), N ₂ and CBN since at 350 ℃ (fj), after firing at 300 ℃ during steam treatment after (ko), O ₂ flow to 5 hours at 150 ℃ for 5 hours meso SAX and WAX diffraction patterns for the pupil TiO ₂ and TEM images at various magnifications. The intensity of the scale bar of SAX is shown in (a) and the intensity of the scale bar of WAX is shown in (b).
Fig. 2 schematically shows an example of a novel process according to the present invention.
Figure 3 is, EISA since, N ₂ and for CBN since at 350 ℃, after steaming at 150 ℃ for 5 h, O ₂ flow and meso pores after firing at 300 ℃ for 5 hours, TiO _2, N ₂ Adsorption and desorption isotherms (left plots) and pore size distributions (today plots). The specific surface area was calculated by the BET method and the pore diameter distribution was analyzed by the BJH method. The pore volume was measured from N ₂ adsorption and desorption isotherms. All mesoporous TiO ₂ samples were of type 1V N ₂ Adsorption and desorption isotherms, which means that the mesoporous materials have a uniform pore structure.
Figure 4a shows the UV-vis spectrum, and Figure 4b shows the photolysis of visible light (385-740 nm) of methylene blue (MB). Here, (a) is MB alone, (b) is MB and anatase nanoparticles, and (c) is MB and mesoporous anatase.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited by these examples.

<Material>

Titanium isopropoxide [> 98%, Ti (OCH (CH ₃ ) ₂ ) _4, TIP] was purchased from Acros. Pluronic P123, methylene blue (MB) and anatase nanopowder (<25 nm) were purchased from Aldrich. Absolute ethanol and 37 wt% HCl were purchased from Samchun.

<Photocatalyst Experiment>

The photocatalytic decomposition of methylene blue was carried out using a 300 W xenon lamp (with a 385 nm cutoff filter) having a wavelength of 385 to 740 nm. Each catalyst (0.1 g) prepared in Examples and Comparative Examples was administered to 50 mL of methylene blue solution (10 mg / L). The crude solution was placed in a dark room for 1 hour with stirring, so that adsorption and desorption were equilibrated. The maximum absorption change of the methylene blue solution was monitored at 660 nm.

<Using the appliance>

Small-angle X-ray (SAX) and wide angle X-ray (WAX) diffraction patterns of samples were measured on a Rigaku D / MAX-2500 / pc diffraction system using Cu-K _a radiation (200 kV, 40 mA) . N ₂ adsorption isotherms were measured at 77 K on BELSORP-max. Prior to measurement, the samples were degassed under vacuum at 200 &lt; 0 &gt; C for 12 hours. Surface area was calculated using the Brunauer-Emmett-Teller (BET) method. The pore size distribution was calculated using the BJH method. TEM images were recorded on a JEOL 2011 microscope operating at 200 kV. Thermogravimetric (TG) analysis was performed at ^25-500 ° C in air using a TA instrument (Thermal Analysis 2050) at a heating rate of 5 ° C min ^-1 . The UV-vis absorption spectrum of the methylene blue solution was recorded on a Shimadzu UV-3101PC.

Example  One

As a typical synthesis method, Pluronic P123 (10 g) was dissolved in ethanol (300 g). DDW (3 mL), HCl (37 wt%, 0.1-30 g), and H ₂ SO ₄ (95 wt%, 0.1-20 mL) were added to the ethanol solution and stirred at 40 ° C for 3 hours. Titanium isopropoxide (36 g) was added and the mixture stirred vigorously for 10 hours. The solution was transferred to a petri dish, and the petri dish was placed in a chamber whose temperature and humidity were adjusted to 40 ° C and 40%. The solvent in the petri dish was evaporated over 24 hours. When all the solvent had evaporated, the remaining solids were dried at 100 &lt; 0 &gt; C for 12 hours. The polymer aggregates inside the TiO ₂ solids were carbonized at 350 ° C for 3 hours under N ₂ . Place them in auto Cleve (autoclave) with 0.5 mL water, and release the auto Cleve in an oven preheated to 150 ℃, it was steamed for meso-pore carbon having a TiO ₂ agglomerates meso pores. The mesoporous anatase containing carbon aggregates was sintered at 300 ° C under oxygen for 4 hours to prepare mesoporous anatase having a high crystal structure.

<Review>

In the present invention, titanium isopropoxide as a Ti source, P123 (Pluronic P123) as an MPDA, a mixture of hydrochloric acid and sulfuric acid as an inorganic acid source, and ethanol as a solvent were used. Based on the weight of the finally obtained mesoporous anatase, the scale used conventionally was 12 g. Evaporation-induced self-assembly (EISA) was performed at 40 ° C for 24 hours. Since EISA small angle X-ray (SAX) diffraction pattern (EISA-TiO ₂₎ of TiO ₂ was shown in the two diffraction peaks 2 θ = 0.70 and 0.95˚ (Lim, Fig. 1a, respectively 12.6 and d = 9.3 nm) , Which means the formation of a meadow dome. However, the wide angle X-ray (WAX) diffraction pattern does not have a peak (Fig. 1B), confirming that the TiO ₂ host is amorphous. Transmission electron microscopy (TEM) images of EISA-TiO ₂ (Fig. 1, ce) also confirmed mesoporous or amorphous.

At 350 ℃ for 3 hours, N ₂ (referred to TiO _2-CBN) since the meso pore TiO ₂ was carbonized under the flow was the SAX diffraction peak moves to higher angle (2 θ = 0.77˚, d = 11.0 nm, Fig. 1f ). However, the WAX diffraction still did not show a peak, indicating that the TiO ₂ host is still amorphous (FIG. 1k). The corresponding TEM image also confirmed that the TiO ₂ host is still amorphous (Fig. 1, hJ).

After steaming (at 150 ° C for 5 hours), the SAX diffraction peak shifted further at higher angles (2 ? = 0.84 占 d = 10.1 nm, Fig. 1k). Surprisingly, a characteristic peak of crystalline anatase appeared in the WAX diffraction pattern (FIG. 11). Through the TEM image (FIG. 1, mo), lattice fringes could be identified in the presence of highly aligned mesopores and at high magnification (FIG. 1, n, o). Thus, steam treatment at 150 ° C for a short time (5 h) not only induces deformation of amorphous TiO ₂ into pure crystalline anatase nanocrystals, but also induces their interconnection to form stable mesoporous anatase.

After calcining the carbon-encapsulated crystalline mesoporous TiO ₂ at 300 ° C under oxygen flow for 5 hours to remove the encapsulated carbon agglomerates, the SAX diffraction pattern showed two peaks d = 11.5 and 9.5 nm (Fig. 1 p ), The WAX diffraction peak intensity was further increased (Fig. 1 (q)), indicating that the crystallinity of the anatase was further improved. In the corresponding TEM images (Fig. 1, rt), more vivid anatase lattice fringes appeared.

The N ₂ adsorption and desorption isotherms of the mesoporous TiO ₂ also showed a Type IV isotherm, which confirmed the mesopore properties of the TiO ₂ species (FIG. 3A). The pore size distribution of the mesoporous TiO ₂ species (FIG. 3b) also showed an average pore size of 5 to 6 nm. Interestingly, however, EISA-TiO ₂ and CBN-TiO ₂ have two pore sizes (EISA-TiO ₂ and CBN-TiO ₂ are in two forms and steamed TiO ₂ in three forms) , The pore size of the steamed TiO ₂ was unimodal, meaning that ink-type pores of uniform shape and size were formed by steam treatment. However, after the C-removal step, the mesoporous system is of three types, meaning that calcinations have resulted in rearrangement of the pore system, resulting in more stable structures. The surface areas of EISA-TiO ₂ , CBN-TiO ₂ , steamed TiO ₂ , and fired TiO ₂ were as high as 291, 216, 163, and 151 m ² g ^-1 , respectively. The corresponding pore sizes were 5.1, 5.4, 5.9, and 6.5 nm, respectively, and the pore volumes were 0.37, 0.29, 0.25, and 0.23 cm ³ g ^-1 , respectively.

The UV-vis spectra of the calcined mesoporous anatase were compared to anatase nanoparticles (25 nm) and rutile microparticles (Fig. 4A). 4A, meso-pore anatase has a tail absorption extending to 430 nm, while anatase nanoparticles only extend up to 400 nm.

As a result of methylene blue (MB) decomposition test by photocatalyst, MB decomposition by mesoporous anatase photocatalyst was much faster than by anatase nanoparticle photocatalyst (FIG. 4B).

Since the process according to the invention requires only spicy simple, low temperature steps, the production of mesoporous anatase is highly reproducible and the physical properties of the produced mesoporous anatase are the same regardless of the batch. In addition, the same final yield (~ 100%) was obtained even when the size was doubled to 24g scale, and the physical properties of the mesopores produced were the same as those of the 12g scale arrangement. Thus, the method according to the present invention is a method which can raise scale.

Claims (9)

A preparation of a precursor solution containing a metal oxide source, a mesopore-directing agent, an acid catalyst and a solvent;
Wherein the mesoporous-inducing agent and the hydrolyzed metal source undergo self-assembly to form a mesopore in the metal oxide by the mesoporous-inducing agent, and wherein the mesoporous-inducer B) forming a filled and agglomerated metal oxide structure;
A step C for carbonizing the mesopore-inducing agent filled in the mesopore;
A step D for intermingling the metal oxide nanoparticles into a fused polycrystalline form while maintaining the mesopore structure by steam treatment at a temperature lower than the carbonization temperature of the C stage; And
And E step of removing carbonated aggregates in the mesoporous pores. The method according to claim 1, wherein the metal oxide is TiO ₂ and the mesoporous metal oxide crystal grains are anatase. The process according to claim 1, wherein the concentration range of the mesoporous-inducing agent in the precursor solution is from 0.01 mol to 1 mol. The method according to claim 1, wherein the mesoporous-inducing agent is a surfactant. A structure produced by the method according to any one of claims 1 to 4, wherein the mesoporous metal oxide crystal grains are interconnected. A method for producing a metal oxide structure in which crystalline metal oxide particles are interconnection,
Treating the amorphous metal oxide with steam to crystallize the metal oxide and at the same time interconnection the metal oxide crystal grains. 7. The process of claim 6, wherein the steaming treatment is carried out under an acid catalyst. The method according to claim 6, wherein the steam treatment temperature is 40 to 400 ° C. 7. The method of claim 6, wherein the metal oxide structure is a mesopore.

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