JP2003260356A - Method for manufacturing h-type layer perovskite photocatalyst and h-type layer perovskite photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method for manufacturing an H-type layer perovskite photocatalyst having various kinds of cations in the B site of the perovskite layer. <P>SOLUTION: The method is characterized in that the H-type layer perovskite compound is obtained by treating the Aurivillius phase expressed by general formula of Bi<SB>2</SB>A<SB>n-1</SB>B<SB>n</SB>O<SB>3n+3</SB>with an acid to selectively dissolve the bismuth oxide phase and to substitute with protons. In the general formula, A represents an atom positioned in the A site of the perovskite layer and is at least one kind of atom selected from Sr, Ca, La, Ba, Pb, Bi, Na, K and others. When two or more of A are present, the selected atoms may be same or different. B represents an atom positioned in the B site of the perovskite layer and is at least one kind of atom selected from Fe, Mn, Ti, Nb, Ta, W, Mo, Cr, Ga, Zr and others, and n is an integer from 1 to 8. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a novel H-type layered perovskite photocatalyst and an H-type layered perovskite photocatalyst obtained by this method.

[0002]

2. Description of the Related Art A photocatalyst that decomposes water into hydrogen and oxygen by light energy is a catalyst that can directly produce hydrogen, which is a promising energy source. Conventionally, research on photolysis of water has been conducted mainly on TiO ₂ , but in recent years, researches using a layered composite oxide having an ion exchange ability as a photocatalyst have been advanced mainly by the group of Domen et al. Domen et al. Have reported that in an Nb-based ion-exchange layered perovskite, the photocatalytic activity is improved by converting it into an H-type layered perovskite by acid treatment (Domen et al., Cat. Lett., Vol. 4, pp.339-314 (1990)).
Further, the Nb-based layered perovskite HCa ₂ Nb ₃ O ₁₀
It has been reported that the photocatalytic activity is improved by cross-linking the layers of silica with silica (Domen et al., Catal. Today., Vo.
l.16, pp.479-486 (1993); Ebina et al., Chem. Mater., Vo.
l.8, No.10, pp.2534-2538 (1996)). It is believed that these behaviors are due to the interlayer being used for photocatalytic reaction. Among the Nb-based layered perovskites, especially Rb
Pb ₂ Nb ₃ O ₁₀ has been found to exhibit photocatalytic activity under visible light irradiation (Yoshimura et al., J. Phys. Chem., Vo.
l.97, No.9, pp. 1970-1973 (1993).

[0003]

However, the cations at the B site of the above ion-exchangeable layered perovskite are limited to Ti, Nb and Ta, and the H-type layered perovskite having various cations other than these at the B site. Is difficult to obtain freely, and the degree of freedom is limited in designing an H-type layered perovskite photocatalyst. Therefore, the present invention provides a novel method for producing an H-type layered perovskite-based photocatalyst having various cations at the B site, and can increase the degree of freedom in designing the H-type layered perovskite-based photocatalyst. And a novel H-type layered perovskite photocatalyst obtained by this method.

[0004]

Means for Solving the Problems An ion-exchangeable layered perovskite M _x A _n , which is a type of layered perovskite
_{-1 B n O 3n + 1 (} M = Rb, K , etc.; A = Sr, C
a, La, etc .; B = Ti, Nb, Ta, etc .; n = number of layers;
x = 1, 2) has a structure in which perovskite layers and alkali metal cations are alternately laminated, and the alkali metal cations between the layers have an ion exchange ability and can be exchanged with other cations. is there. Particularly, by acid treatment, an H-type layered perovskite having protons between the layers can be obtained.

As a compound having a structure similar to this ion-exchangeable layered perovskite, Auribilius (Auri)
Villius) _phase, there are _{Bi 2 A n-1 B n} O 3n + 3,
A bismuth oxide layer [(Bi ₂ O ₂ ) ²⁺ ] is present in the interlayer portion. This Auribilius phase, Bi ₂ A _{n-1
B n O 3n + 3 (A} = Sr, Ca, La, Ba, Pb,
Bi, Na, K, etc.) is different from the ion-exchangeable perovskite, for example, Fe, Mn, Ti, Nb, Ta,
Various cations such as W, Mo, Cr, Ga, and Zr can be present at the B site of the perovskite layer, and those having various compositions can be prepared as compared with the ion-exchange layered perovskite.

The present inventors acid-treat the compounds of the aurivirius phase which can have such various compositions, so that only the bismuth oxide layer is selectively eluted, and H ⁺ is added between the layers for charge compensation. It is possible to synthesize various H-type layered perovskite compounds by the reaction to be introduced, and further obtain new knowledge that these obtained H-type layered perovskite compounds have photocatalytic activity. Has been completed.

That is, the method for producing a photocatalyst of the present invention is
An auribilis phase represented by the general formula, Bi ₂ A _n-1 B _n O _{3n +3} , that is, Bi ₂ A _n-1 B _n O.
A compound having an auribilius type structure represented by _{3n + 3} is treated with an acid to selectively elute the bismuth oxide layer and replace it with a proton to obtain an H-type layered perovskite compound. , A in the above general formula means an atom located at the A site of the perovskite layer, and Sr, Ca, La, B
at least one atom selected from a, Pb, Bi, Na, K and the like, and when A is 2 or more, the selected atoms may be the same or different, and B means an atom located at the B site of the perovskite layer, and Fe, Mn, Ti, Nb, Ta, W, M
at least 1 selected from o, Cr, Ga, Zr, etc.
It is an atom of one or more species, n is the number of layers, and is generally an integer of 1-8.

The above-mentioned "layered perovskite system" means not only a substance consisting of a single phase of a compound known as a layered perovskite, but also a substance containing a phase different from the layered perovskite in part, or a perovskite structure. Means a substance including a substance having a structure similar to that of "H-type" means a substance in which some or all of the ions existing between the layers of the perovskite layer are ion-exchanged with protons. Is.

Further, in the method for producing an H-type layered perovskite photocatalyst of the present invention, n is 2 or 3, a general formula,
It is characterized by including a step of selectively eluting the bismuth oxide layer and substituting it with a proton by acid-treating an auribilius phase represented by Bi ₂ AB ₂ O ₉ or BiA ₂ B ₃ O _12. , In the general formula, A means an atom located at the A site of the perovskite layer,
It is at least one atom selected from Sr, Ca, La, Ba, Pb, Bi, Na and K, and in particular, B
When there are two A's such as iA ₂ B ₃ O ₁₂ ,
The atoms selected are any combination that may be the same or different. Particularly, different combinations include a combination of a divalent or trivalent metal such as Sr, Ca, La, Ba, Pb and Bi and a monovalent metal such as Na and K. Of these, A is Bi ₂
In the case of AB ₂ O ₉ , Sr, Ca and the like are preferable, and BiA
_In the case of ₂ B ₃ O ₁₂ , the combination of the two A is:
Preferred are combinations of Sr and Na, Ca and Na, Sr and K, and Ca and K. On the other hand, B means an atom located at the B site of the perovskite layer, and Fe, Mn, T
At least one atom selected from i, Nb, Ta, W, Mo, Cr, Ga, Zr, etc., and particularly N
It is preferable to contain b or Ta.

Furthermore, the present invention is based on the above manufacturing method.
Including the H-type layered perovskite-based photocatalyst obtained by
In particular, as an Auribilius phase compound, Bi_TwoSrNa
Nb _ThreeO₁₂, Bi_TwoCaNaNb_ThreeO₁₂, Bi_TwoC
aTa_TwoO₉, Or Bi _TwoCaNaTa_ThreeO₁₂so
H-type layer obtained by acid treatment of the represented compound
It is characterized by being a perovskite type photocatalyst.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The H-type layered perovskite of the present invention
The method for producing a photocatalyst based on the general formula, Bi_TwoA_{n -1}B_nO
_{3n + 3}Auribilius phase represented by, that is, Bi
_TwoA_n-1B _nO_{3n + 3}Auribilius type represented by
By treating the compound having the structure of
Selective elution of the bismuth oxide layer in the Liberius phase
Both are characterized by substitution with protons for charge compensation
It is what

The Auribilius phase used in the present invention is
_{Formula, Bi 2 A n-1 B} n O 3n +3 ( or Bi
₂ O ₂ A _n-1 B _n O _{3n + 1} ), which is a kind of layered perovskite and has a layered structure in which a bismuth oxide sheet is grown between the perovskite layers.
The number of layers is represented by n, and n = 1 to 8 is known. In the formula, A means an atom located at the A site of the perovskite layer, and is a lanthanoid such as Sr, Ca or La, a divalent or trivalent metal such as Ba, Pb or Bi, or Na, At least one atom selected from monovalent metals such as K and Rb may be located at the A site. On the other hand, B means an atom located at the B site of the perovskite layer, and Fe, Mn, T
At least one atom selected from i, Nb, Ta, W, Mo, Cr, Ga, Zr and the like can be located at the B site. The atoms located at these A and B sites are determined by the charge balance. Examples of the lanthanoid include La, Sm,
Examples thereof include Pr.

As such an Aulibillius phase compound
Relates to compounds with a proper B-site stoichiometry
Is, for example, when n = 2 (two-layer structure), Bi_TwoC
aTa_TwoO₉, Bi_TwoSrTa_TwoO₉, Bi_TwoCaNb
_TwoO₉, Bi_TwoSrNb_TwoO ₉, Bi_TwoNa_0.5Bi
_0.5Nb_TwoO₉Etc., n = 3 (three-layer structure)
For example, Bi is_TwoSrNaNb
_ThreeO₁₂, Bi_TwoCaNaNb _ThreeO₁₂, Bi_TwoCaN
aTa_ThreeO₁₂And so on, Bi_TwoSr_TwoTiM_TwoO₁₂
(Where M = Ta, Nb), Bi_TwoLnSrTi_TwoMO
₁₂(Where M = Ta, Nb; Ln = La, Sm, etc.)
And so on, as will be understood from now on, B site
Two atoms located at the A site depending on the atom of
Combination of metals or combination of trivalent and monovalent metals
Can be configured by. In addition, n = 4 (4 layer structure)
In the case of manufacturing), for example, Bi_TwoBaBi_TwoTi_ThreeGa
O₁₅, Bi_TwoBi_ThreeTi_ThreeFeO₁₅, Bi_TwoBi_Three
Ti_ThreeMnO₁₅When n = 5 (5-layer structure)
Is, for example, Bi_TwoPr_TwoBi_TwoTi_ThreeFe_TwoO₁₈Na
There is a throat.

On the other hand, if the B site is basically made of Ti, Nb, Ta, W, etc., if the valence is one and the ionic radius is close, the B site can be easily replaced. It is possible to prepare a so-called solid solution. The charge balance at that time can be adjusted both at the A site and at the Bi site.
When it is regulated at the A site, for example, Bi ₂ Pb
_{x Bi 2-x Ti 3-} x Nb x O 12, Bi 2 Sr x B
There is an example of such _{i 2-x Ti 3-x} Ta x O 12, Bi
As for the case of adjusting at the site, for example, Bi _2-x P
_{b x SrNb 2- x W x O} 9, Bi 2-x Te x SrN
Examples of such b _{2-x Ti} x _{O 9} is shown. Incidentally, that adjust the charge Bi site is "Bi _2-x", strictly speaking there is different from the general formulas instead of "Bi _2" but the original even these solid solutions "Bi _2" Table The composition has the above-mentioned composition and can be used as the aurivirius phase of the present invention.

As described above, the Aurivillius phase compound is
Various metals can be individually introduced into both the A site and the B site, and a large variety of compounds can be prepared.

Such a compound can be prepared by a solid phase method in which raw materials are mixed in a stoichiometric ratio and fired. For example, in Bi ₂ SrTa ₂ O ₉ with n = 2, Bi is mixed. ₂ O _3, and SrCO _{3, Ta} 2 _{O 5} were mixed in a stoichiometric ratio, by firing at 900 to 1000 ° C., in the case of n = 3 of _Bi 2 CaNaNb ₃ O _12, and NaNbO ₃ BiCaNb ₂ O ₉ molar ratio 1: 1
It is possible to obtain it by mixing the above and baking at 1000 to 1100 ° C. Similarly, when n = 4 or more,
It can be obtained by mixing the aurivirius phase and the perovskite and firing.

Next, the obtained compound having an Aurivillius phase is treated with an acid, but it is preferable to grind the compound prior to the treatment. Examples of the acid used for the acid treatment include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, and hydrochloric acid is particularly preferable in that it can complete the reaction. The acid concentration is usually about 1 M to 6 M, and the treatment temperature and time are about room temperature to 60 ° C. and about 24 to 72 hours, respectively. Generally, the higher the acid concentration and the treatment temperature and the longer the treatment time, the more the elution amount of the bismuth oxide layer tends to increase, but no significant difference is observed. However, when Ti or the like is contained in the B site, these metals are likely to be eluted by an acid, and therefore it is preferable to carry out at a low acid concentration.

By this acid treatment, the bismuth oxide layer in the aurivilius phase is selectively eluted without changing the structure of the perovskite layer, and instead, protons are introduced between the perovskite layers as charge compensation, resulting in the H-type layer structure. Converted to perovskite compounds.

The treated product after the acid treatment is then
Solid-liquid separation is performed by filtration, centrifugation, etc., thoroughly washed, and then dried. Drying is preferably carried out at room temperature to about 120 ° C.

As described above, the Aurivillius phase is treated with acid.
The product thus obtained has an H-type layered perovskite structure.
Although it has, perovskite during acid treatment
Bismuth oxide between slabs is selectively eluted.
Although it is replaced by a proton, it is usually
Bismuth is formed by replacing some of the smut with the metal ions at the A site
It may be an H-type layered perovskite containing
In many cases, such replacement may not occur. Elution
A part of the bismuth formed was replaced with the metal ion at the A site.
A so-called mutual substitution occurs, n = 2
Billius phase Bi _TwoAB_TwoO₉When treated with acid, H_p
[(Bi_qA_r) B_TwoO₇] Has a composition represented by
Also, the atom occupying two A sites at n = 3 is divalent gold.
In the case of the Auribilius phase, which is a genus A and a monovalent metal M
Is H_p[(Bi_qA_r) MB_ThreeO₁₀] Pairs
H-type layered perovskite compound having
It Where A is the size of a layered perovskite-like slab
Means an atom located in G, Sr, Ca, La, Ba,
At least one atom selected from Pb and Bi
Yes, M is on the A site of the layered perovskite slab
Means an atom to be placed, and is an atom selected from Na and K
Yes, B is on the B site of a layered perovskite-like slab
Means an atom to be placed, Fe, Mn, Ti, Nb, Ta,
At least selected from W, Mo, Cr, Ga, and Zr
It is one or more kinds of atoms, and the range of p, q, and r is within the range of acid treatment.
Generally, p is 1.7 to 1.9, q
Is 0.1 to 0.3, r is 0.7 to 0.9, and
H⁺The total amount of p and the amount of remaining bismuth q is
Equal to the amount of bismuth in the Auribilius phase
Of.

To give a concrete example of the composition, for example, n =
In case of 3, Bi_TwoSrNaNb_ThreeO ₁₂Acid-treated raw
The product is H_1.7[(Bi_0.3Sr_0.7) NaNb
_ThreeO ₁₀], And Bi_TwoCaNaNb_ThreeO₁₂Acid treatment
The processed product is H_1.8[(Bi_0.2Ca_0.8) N
aNb_ThreeO₁₀], And Bi_TwoCaNaTa_ThreeO_{1 Two}
The acid-treated product is H_1.9[(Bi_0.1Ca
_0.9) NaTa_ThreeO₁₀] And n = 2, B
i_TwoSrTa_TwoO₉The acid-treated product is H
_1.8[(Bi_0.2Sr_0.8) Ta_TwoO₇]
It had a composition. In addition, of the Auribilius phase
Depending on the type and the conditions of acid treatment, the total aurivirius phase
Are not H-type layered perovskites, and some are auri
It may remain as a illius phase, but this remains
The amount is usually less than 10%,
However, all are converted to H-type layered perovskite to convert the single phase
Similar to the one shown, it had photocatalytic activity.

When the above-mentioned mutual substitution between Bi and the metal at the A site does not occur, some or all of (Bi ₂ O ₂ ) ²⁺ existing between the perovskite layers is H ⁺ converted, and n = 2. In the case of Bi ₂ AB ₂ O ₉ , H _s [AB ₂
O ₇ ] (however, s is about 1.5-2) will be obtained.

The acid-treated product, which is the H-type layered perovskite-based compound, has photocatalytic activity, and generates hydrogen by irradiating the acid-treated product suspended in an aqueous alcohol solution with ultraviolet rays. You can The band gap of the acid-treated product is slightly larger than that of the parent aurivirius phase compound and is generally about 3.3 to 4.1 eV, but the aurivirius phase is present at the B site as compared to the ion-exchangeable layered perovskite. As a result of easy selection of cations, various layered perovskite proton bodies can be derived from the aurivirius phase, and photocatalysts having a desired band gap can be prepared.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples.

[0025]

EXAMPLES Example 1 Starting material, Bi ₂ ANaNb ₃ O ₁₂ (A = S
r, Ca) is a two-layered aurivilius phase Bi ₂ AN
b ₂ O ₉ (A = Sr, Ca) and NaNbO ₃ having a perovskite structure were mixed at a molar ratio of 1: 1 and reacted by calcination in air for 3 hours at 1100 ° C. The reaction product was crushed.

Then, the obtained Bi ₂ ANaNb ₃ O
₁₂ (A = Sr, Ca) About 10g to 1000ml of 6M
-Acid treatment was carried out by stirring in HCl at room temperature for 72 hours.
After the completion of stirring, centrifugation was performed, the supernatant was removed, and the mixture was washed with pure water. Wash the sample in air (at room temperature or 1
It was dried at 20 ° C.) to obtain an acid-treated product. The resulting acid-treated product was evaluated and characterized as follows.

1. The cation ratio in the composition ratio sample is determined by the high frequency inductively coupled plasma (IC
P) emission analysis (Nippon Jarrel Ash, ICAP75MK II,
IRIS-AP). At this time, the cation ratio of Nb was fixed to 3 to determine the cation ratio. Sample dissolution is
Nitric acid (5 ml), hydrochloric acid (10 ml) and hydrofluoric acid (5 m
It was carried out by heating at 200 ° C. for 2 hours in the mixed acid of 1).

The amount of protons and the amount of hydration in the acid-treated product were determined by thermogravimetric analysis (TG) (manufactured by MacScience,
TG-DTA2000S), and calculated from the weight loss when the temperature was raised to 1000 ° C. (10 ° C./min) in dry air.

2. The structure of the structural sample was analyzed by powder X-ray diffraction (XRD) analysis (RINT-2500 manufactured by Rigaku Denki Co., Ltd.) using CuKα rays monochromated by a monochromator.

The sample morphology is a scanning electron microscope (SEM).
(Hitachi, S-2500) was used for observation.

3. Photocatalytic activity The photocatalytic activity of each sample was evaluated by a hydrogen production reaction from an aqueous ethanol solution in a closed circulation system. Put 1 g of catalyst and 700 ml of 20% ethanol aqueous solution into a glass reaction container (1000 ml), and diffuse the catalyst powder with a stirrer while keeping the liquid temperature at 20 ° C., and a 500 W ultra-high pressure mercury lamp (USHIO INC. UI-501C). ) Was used to irradiate ultraviolet rays from the side of the reaction vessel, and the generated hydrogen was quantified by a gas chromatograph (Shimadzu Corporation, GC-8A).

The band gap of the photocatalyst was calculated by measuring the UV-visible diffuse reflectance spectrum using UV-2500PC manufactured by Shimadzu Corporation.

Table 1 shows the composition analysis results by ICP emission analysis.
Shown in.

[0034]

[Table 1] According to the results of Table 1, the Bi content was significantly reduced in the sample after the acid treatment, and thus the bismuth oxide layer [(Bi
₂ O ₂ ) ²⁺ ] is eluted. Also,
The small amount of Bi remaining and the decrease of Sr or Ca in the acid-treated product are considered to be due to mutual substitution between the A site of the perovskite layer and the Bi site of the bismuth oxide layer. That is, when A = Sr, about 15% of Bi are mutually substituted with Sr, and when A = Ca, B
It can be seen that about 10% of i are mutually substituted with Ca.
Also, considering the charge of the perovskite layer, the amount of protons between layers is 1.7 when A = Sr and 1.8 when A = Ca, which values are in agreement with the results from TG analysis.

The results of TG analysis are shown in FIG. 1, and the amount of protons and the amount of hydration were calculated from these results. That is, the weight loss from room temperature to about 200 ° C. is due to elimination of hydration water, and the weight reduction from about 200 to 600 ° C. is due to elimination of protons.
= Sr = 1.7, A = Ca = 1.8, and it can be seen that this result almost agrees with the result of ICP analysis. The amounts of water of hydration were about 1.0 for Sr and Ca. In addition, FIG. 1A shows Bi ₂ SrNa.
Nb ₃ O ₁₂ acid-treated product, (b) is Bi ₂ CaN
4 shows TG analysis results of an acid-treated product of aNb ₃ O ₁₂ .

The structural change before and after the acid treatment was examined by XRD. The XRD measurement results are shown in Fig. 2 as Bi ₂ SrN.
In the case of aNb ₃ O ₁₂ , (a) starting material (Bi
₂ SrNaNb ₃ O ₁₂ ), (b) acid-treated sample dried in air, and (c) acid-treated sample at 120 ° C.
The XRD pattern was shown for each of those dried in. From FIG. 2, the layer spacing is represented by acid treatment (002)
It can be seen that the peak of (110) shifts to the higher angle side, while the peak of (110) does not change. The peak of the sample after the acid treatment coincided with the peak position of the H-type layered perovskite. All of these peaks can be assigned as tetragonal crystals, and the change in lattice constant can be represented by Bi ₂ Ca.
It is shown in Table 2 together with the case of NaNb ₃ O ₁₂ .

[0037]

[Table 2] From the above results, the obtained acid-treated products, respectively,
_{H 1.7 [(Bi 0. 3 Sr} 0.7) NaNb
₃ O ₁₀ ] and H _1.8 [(Bi _0.2 Ca _0.8 ).
It can be seen that it is an H-type layered perovskite having a composition of NaNb ₃ O ₁₀ ].

SEM of the samples before and after the acid treatment
As a result of observation, particles having a diameter of several μm were observed in all cases, and no change in particle morphology such as a decrease in particle diameter due to acid treatment was observed.

Next, the photocatalytic activity of the obtained sample was examined. First, in order to determine the bandgap, which is one of the factors that affect the photocatalytic activity, the ultraviolet-visible diffuse reflectance spectra of the starting material and its acid-treated product were measured, and the bandgap calculated from the absorption edge wavelength is shown in Table 3. It was shown to. The measured spectrum is shown in Fig. 3.
The case of Bi ₂ SrNaNb ₃ O ₁₂ is illustrated.
In the figure, (a), (b) and (c) show the case of a starting material (Bi ₂ SrNaNb ₃ O ₁₂ ), an acid-treated product (air-dried) and an acid-treated product (120 ° C.), respectively. There is.

[0040]

[Table 3] As can be seen from Table 3, it is found that the absorption edge is blue-shifted, that is, the band gap is increased by making the H-type by acid treatment. It is presumed that this is due to a change in crystal system, that is, a change in strain of the perovskite layer.

Next, the results of the photocatalytic activity using the generation of hydrogen from the aqueous ethanol solution as an index are shown in FIG. In the figure, (a) and (c) are the starting materials Bi ₂
SrNaNb ₃ O ₁₂ and Bi ₂ CaNaNb ₃ O
₁₂ and (b) and (d) show changes with time in the amount of hydrogen generated when the respective acid-treated products were used.

According to FIG. 4, the starting material, auribilius phase Bi ₂ ANaNb ₃ O ₁₂ (A = Sr, Ca).
, Showed no activity for hydrogen production from an aqueous ethanol solution, but the acid-treated products obtained by acid-treating them showed increased photocatalytic activity as the amount of hydrogen increased over time, and acid-treated Auribilius phase. It was found that a photocatalyst can be obtained by converting into a layered perovskite-type substance.

Example 2 Starting material, Bi ₂ ATa ₂ O ₉ (A = Sr, C
a) to Bi ₂ O ₃ , CaCO ₃ (or SrC)
O ₃ ) and Ta ₂ O ₅ are mixed at a molar ratio of 1: 1: 1,
Calcination in air at 700 ° C for 12 hours, crushing, then 10
After calcination and crushing at 00 ℃ for 12 hours, 1000 more
The reaction product was synthesized by calcination at 24 ° C. for 24 hours, and the obtained reaction product was pulverized.

Then, the obtained Bi ₂ ATa ₂ O ₉ (A
= Sr, Ca) was treated with hydrochloric acid in the same manner as in Example 1 to obtain an acid-treated product. The composition of the acid-treated product obtained together with the conditions of the acid treatment is shown in Table 4, and also Bi ₂
The XRD measurement result for the case of CaTa ₂ O ₉ is shown in FIG.
It was shown to.

[0045]

[Table 4] From Table 4, in the acid-treated product in the case of Bi ₂ SrTa ₂ O ₉ , protons were introduced together with elution of the bismuth oxide layer, and Bi and Sr were mutually substituted, H _1.8 [(Bi
It is understood that the H-type layered perovskite is represented by _0.2 Sr _0.8 ) Ta ₂ O ₇ ]. On the other hand, Bi ₂ CaT
In the case of a ₂ O ₉ , as can be seen from the XRD shown in FIG. 5, the peak of the starting material Bi ₂ CaTa ₂ O ₉ remains,
About 10% of the matrix remained, and a single phase of H-type layered perovskite could not be obtained. Also, considering that the amount of Ca is hardly changed by the acid treatment,
It is estimated that there is almost no mutual substitution of Bi and Ca at the A site. The composition of this acid-treated product is apparently represented as H _1.8 Bi _0.2 CaTaO _7.2 .

Example 3 The starting material, Bi ₂ CaNaTa ₃ O _12, was converted into Bi
1 and ₂ CaTa ₂ O ₉ and NaTaO ₃ molar ratio were mixed in 1, 1000 ° C. in air, and pulverized after calcination for 12 hours, further 1000 ° C., was synthesized by reacting by baking 12 hours, The reaction product obtained was ground.

Then, the obtained Bi ₂ CaNaTa ₃ O
₁₂ was acid-treated with hydrochloric acid in the same manner as in Example 1 to obtain an acid-treated product. The composition of the acid-treated product obtained together with the conditions of the acid treatment is shown in Table 5.

[0048]

[Table 5] From Table 5, in the acid-treated product in the case of Bi ₂ CaNaTa ₃ O ₁₂ , protons were introduced together with elution of the bismuth oxide layer, and about 5% of Bi was replaced with Ca by H _1.9.
It can be seen that the H-type layered perovskite is represented by [(Bi _0.1 Ca _0.9 ) NaTa ₃ O ₁₀ ].

Next, the band gaps of the acid-treated products obtained in Examples 2 and 3 are shown in Table 6, and the results when the photolysis reaction of the aqueous ethanol solution was carried out are shown in FIG.

[0050]

[Table 6] According to Table 6, the compounds of the Auribilius phase are acid treated.
It can be seen that the band gap is widening.
Light In addition, according to FIG. 6, the starting material, auribili
Us phase Bi_TwoCaTa_TwoO₉(N = 2) and Bi_TwoC
aNaTa_ThreeO ₁₂(N = 3) are both ethanol water
It showed no activity in producing hydrogen from solution,
The acid-treated product that has been acid-treated will generate water over time.
It can be seen that the elementary content increases and photocatalytic activity is exhibited. Also,
The number of perovskite layers, that is, the number of layers on the photocatalytic activity
Looking at the effect, it can be seen that the higher the number of layers, the higher the activity.
It In addition, when comparing the types of atoms at the A site,
However, the photocatalytic activity was higher than that of Sr.

[0051]

EFFECTS OF THE INVENTION According to the method for producing an H-type layered perovskite photocatalyst of the present invention, compared with the ion-exchangeable layered perovskite, it has an aurivilius phase in which the number of kinds of cation species that can exist in the B site is large, that is, an auribilius type structure Since it is prepared by treating the compound with an acid, various H-type layered perovskite photocatalysts having various cation species at the B site can be produced.

[Brief description of drawings]

FIG. 1 is a diagram showing TG analysis results of an H-type layered perovskite photocatalyst obtained in the present invention, in which (a) is an acid treatment product of Bi ₂ SrNaNb ₃ O ₁₂ and (b) is 4 shows the TG analysis results of the acid-treated product of Bi ₂ CaNaNb ₃ O ₁₂ .

FIG. 2 is a diagram showing the XRD measurement results of the H-type layered perovskite photocatalyst obtained in the present invention, wherein (a) in the figure.
Is a starting material (Bi ₂ SrNaNb ₃ O ₁₂ ), (b) is an air-dried sample of the acid treatment, and (c) is an XRD pattern of the acid-treated sample dried at 120 ° C.

FIG. 3 is an H-type layered perovskite-based light obtained by the present invention.
FIG. 3 is a diagram showing the results of UV-visible diffuse reflectance spectrum of a catalyst.
In the figure, (a) is the starting material (Bi_TwoSrNaNb_ThreeO
₁₂) And (b) are air-dried acid-treated products, (c) is 12
The result of the acid treatment product dried at 0 ° C is shown.

FIG. 4 is a graph showing the photocatalytic activity of the H-type layered perovskite-based photocatalyst obtained by the present invention, using the amount of hydrogen generated as an index, wherein (a) and (c) are the starting materials Bi ₂ SrNaNb. ₃ O ₁₂ and Bi ₂ CaNaNb
₃ O _12, shows the case of (b) the acid treated product of _{Bi 2 SrNaNb 3 O 12, (} d) is _{Bi 2} CaNaNb ₃ O ₁ 2 acid-treated product.

FIG. 5 is a graph showing the XRD measurement results of the H-type layered perovskite photocatalyst obtained in the present invention.
i ₂ CaTa ₂ O ₉ ) and the XRD pattern of the acid-treated product when acid-treated under various conditions.

FIG. 6 is a graph showing the photocatalytic activity of the H-type layered perovskite-based photocatalyst obtained by the present invention, using the amount of hydrogen generated as an index, wherein (a) and (c) are starting materials Bi ₂ CaNaTa. ₃ O ₁₂ and Bi ₂ CaTa ₂ O
₉ shows the case of (b) the acid treated product of _{Bi 2 CaNaTa 3 O 12, (} d) the acid-treated product of _{Bi 2} CaTa 2 O _9.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G048 AA04 AA05 AB02 AC08 AD06                       AD08 AE05                 4G069 AA02 AA08 BB06A BB06B                       BC02A BC02B BC03A BC09A                       BC09B BC12A BC12B BC13A                       BC17A BC21A BC25A BC25B                       BC50A BC51A BC55A BC55B                       BC56A BC56B BC58A BC59A                       BC60A BC62A BC66A BD01A                       CC33 EC23 FA01 FB49 FC08

Claims (10)

[Claims] 1. A general formula, Bi ₂ A _n-1 B _n O _{3n + 3.}
A method for producing an H-type layered perovskite-based photocatalyst, which comprises a step of selectively eluting the bismuth oxide layer and substituting it with protons by acid-treating the auribilius phase represented by. However, in the formula, A means an atom located at the A site of the perovskite layer, and Sr, Ca, L
at least one atom selected from a, Ba, Pb, Bi, Na and K, and when A is 2 or more, the selected atoms may be the same or different, and , B mean atoms located at the B site of the perovskite layer, and Fe, Mn, Ti, Nb, Ta, W, M
It is at least one atom selected from o, Cr, Ga, and Zr, and n represents the number of layers and is an integer of 1 to 8. 2. An H-type layered perovskite system including a step of selectively eluting the bismuth oxide layer and substituting it with protons by acid-treating an aurivirius phase represented by the general formula, Bi ₂ AB ₂ O _9. Photocatalyst manufacturing method. However, in the formula, A means an atom located at the A site of the perovskite layer, and Sr, Ca, La, Ba, P
b, Bi, Na, at least one atom selected from K, B means an atom located at the B site of the perovskite layer, Fe, Mn, Ti, Nb, Ta,
It is at least one atom selected from W, Mo, Cr, Ga, and Zr. 3. An H-type layered layer including a step of selectively eluting the bismuth oxide layer and substituting it with a proton by acid-treating an auribilius phase represented by the general formula, Bi ₂ A ₂ B ₃ O _12. Manufacturing method of perovskite photocatalyst. However, in the formula, A means an atom located at the A site of the perovskite layer, and Sr, Ca, La, Ba,
At least one atom selected from Pb, Bi, Na, and K, and the two selected atoms A may be the same or different, and B is B of the perovskite layer. Means an atom located on the site, F
e, Mn, Ti, Nb, Ta, W, Mo, Cr, Ga,
It is at least one atom selected from Zr. 4. A is Sr and Ca, B is Nb and T
The method for producing an H-type layered perovskite photocatalyst according to claim 2, which is a. 5. The production of an H-type layered perovskite photocatalyst according to claim 3, wherein the two atoms of A are Sr and Na, Ca and Na, Sr and K, Ca and K, and B is Nb and Ta. Method. 6. An H-type layered perovskite photocatalyst obtained by the method according to claim 1. 7. An H-type layered perovskite-based photocatalyst in which a bismuth oxide layer is selectively eluted and replaced with protons by acid treatment of an aurivirius phase represented by Bi ₂ SrNaNb ₃ O ₁₂ . 8. An H-type layered perovskite-based photocatalyst in which a bismuth oxide layer is selectively eluted and replaced with protons by acid treatment of an aurivilius phase represented by Bi ₂ CaNaNb ₃ O ₁₂ . 9. An H-type layered perovskite-based photocatalyst in which a bismuth oxide layer is selectively eluted and replaced with protons by acid treatment of an auribilius phase represented by Bi ₂ CaTa ₂ O ₉ . 10. An H-type layered perovskite-based photocatalyst in which a bismuth oxide layer is selectively eluted and replaced with protons by acid treatment of an aurivilius phase represented by Bi ₂ CaNaTa ₃ O ₁₂ .