Preparation method and application of a ferroelectric total water-splitting photocatalyst

Abstract

The application discloses a preparation method and application of a ferroelectric full water-splitting photocatalyst. The preparation method comprises the following steps: S1: pretreating a ferroelectric material to obtain a pretreated ferroelectric material; S2: after atomic layer deposition of the pretreated ferroelectric material and a metal organic complex source material, non-active gas I is introduced to perform blowing I, water is introduced, non-active gas II is introduced again to perform blowing II, and the first deposition is completed; and S3: according to the thickness of the ferroelectric full water-splitting photocatalyst, the step S2 is circularly performed to obtain the ferroelectric full water-splitting photocatalyst. The ferroelectric material can efficiently photocatalyze full water splitting through accurate regulation and modification of the surface of the ferroelectric material by the atomic layer deposition technology. The method not only provides an experimental basis for researching the limiting factors of the ferroelectric material in a photocatalytic reaction, but also provides a new idea for constructing an efficient photocatalyst by using efficient charge separation and depolarization electric field of the ferroelectric material.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method and application of a ferroelectric full water splitting photocatalyst, and belongs to the field of ferroelectric photocatalytic materials. BACKGROUND

[0002] When the ferroelectric material is below the Curie temperature, the lattice is distorted due to the softening of a specific phonon mode, resulting in the breaking of symmetry and the formation of separate positive and negative charge centers in the lattice. Therefore, a spontaneous polarization phenomenon occurs in the macroscopic ferroelectric body. The spontaneous polarization of the ferroelectric material generates a spontaneous depolarization electric field in the ferroelectric domain, and the theoretical value can reach 10 5 kV / cm, providing a solution for effective charge separation of photocatalytic materials. However, the photocatalytic activity of the current ferroelectric material is very poor. The biggest problem of applying ferroelectric materials to the field of photocatalysis is the huge contrast between the extremely strong electric field and the almost impossible photocatalytic activity.

[0003] The surface interface of the ferroelectric material is very complex, and part of the complexity comes from the surface states formed by the material. These surface states are generated due to the lack of translational symmetry at the crystal boundary, and have a unique electronic band structure. In addition, the formation of spontaneous polarization at the ferroelectric surface interface generates bound charges, resulting in the formation of shielding charges on the inner and outer surfaces of the ferroelectric material. This complex surface structure has a great influence on the separation and utilization of photo-generated charges in the ferroelectric material. Therefore, it is very difficult but also very important to precisely adjust the surface of the ferroelectric photocatalytic material.

[0004] At present, the modification and regulation of the surface interface of the ferroelectric photocatalytic material are mainly based on the methods of hydrothermal growth of strontium titanate, bismuth ferrite and titanium oxide. These methods use similar components or lattice structures to adsorb and grow precursors on the surface of the ferroelectric crystal, thereby forming a better ferroelectric interface structure. For example, hydrothermal growth of strontium titanate on the surface of lead titanate can improve the photocatalytic water splitting activity of lead titanate. However, these methods have some defects and deficiencies. On the one hand, the growth of the material is limited by the lattice structure and material composition, so it has certain limitations. On the other hand, these methods cannot achieve very precise regulation because the minimum thickness of the growth is affected by the size of the precursor, so the growth can only be carried out in units of the size of the precursor as the thickness. Therefore, there are certain limiting factors in the research on the surface interface problem of the ferroelectric photocatalytic material. SUMMARY

[0005] To solve the above problems, we use the method of atomic layer deposition to take the single chemical adsorption of the precursor as the growth unit. The atomic layer thickness can be precisely controlled to regulate the ferroelectric surface. Through this method, the surface of the ferroelectric material is modified and regulated, and the photocatalytic water splitting activity of the ferroelectric lead titanate can be significantly improved.

[0006] The purpose of the present application is to construct an efficient ferroelectric photocatalytic material for full decomposition of water, and to provide an experimental basis for studying the utilization of ferroelectric materials in the field of photocatalysis. The precise regulation of the surface of the ferroelectric material by atomic layer deposition can greatly improve the efficiency of photocatalytic water decomposition.

[0007] According to one aspect of the present application, a preparation method of a ferroelectric full-decomposition water photocatalyst is provided, the preparation method comprising the following steps:

[0008] Step S1: pretreating a ferroelectric material to obtain a pretreated ferroelectric material;

[0009] Step S2: after atomic layer deposition of the pretreated ferroelectric material and a metal organic complex source material, introducing a non-active gas I for blowing I, introducing water, and introducing a non-active gas II for blowing II again, the first deposition is completed;

[0010] Step S3: according to the thickness of the ferroelectric full-decomposition water photocatalyst, the step S2 is cycled to obtain the ferroelectric full-decomposition water photocatalyst.

[0011] Optionally, in the step S1, the ferroelectric material is selected from at least one of ferroelectric lead titanate, barium titanate, bismuth ferrite, lead zirconate titanate, and lithium niobate.

[0012] Optionally, in the step S2, the metal organic complex source material is selected from at least one of an aluminum oxide precursor, a titanium oxide precursor, a silicon oxide precursor, an iron oxide precursor, and a tin oxide precursor.

[0013] Optionally, the aluminum oxide precursor is selected from at least one of trimethylaluminum, aluminum trichloride, triethylaluminum, and dimethylaluminum chloride.

[0014] Optionally, the titanium oxide precursor is selected from at least one of tetrakis(dimethylamido)titanium, pentamethylcyclopentadienyltitanium trichloride, tetraisopropyl titanate, and tetrakis(ethylamido)titanium.

[0015] Optionally, the silicon oxide precursor is selected from at least one of silicon tetrachloride, silicon tetrafluoride, triethylsilylamine, and 1,1,1-tris(dimethylamino)silane.

[0016] Optionally, the iron oxide precursor is selected from at least one of ferrocene, bis(isopropylcyclopentadienyl)iron, tert-butyl ferrocene, and iron tert-butoxide.

[0017] Optionally, the tin oxide precursor is selected from at least one of tetrakis(dimethylamino)tin, tetrapropyltin, bis(acetylacetonato) dibutyltin, and bis(N,N'-diisopropylacetamidinato)tin.

[0018] Optionally, the time of the atomic layer deposition in the step S2 is independently selected from 5s, 10s, 20s, 30s, 50s, 60s, 80s, 90s, 100s, 120s or a range between any two of the above values.

[0019] Optionally, the time of the atomic layer deposition in the step S2 is independently selected from 5s, 10s, 20s, 30s, 50s, 60s, 80s, 90s, 100s, 120s or a range between any two of the above values.

[0020] Optionally, the temperature of the atomic layer deposition comprises a reaction source temperature and a reaction cavity temperature.

[0021] Optionally, the reaction source temperature is 25-120℃.

[0022] Optionally, the reaction cavity temperature is 40-200℃.

[0023] Optionally, the flow rate of the non-reactive gas I and the non-reactive gas II in the step S2 is independently selected from 0-100sccm.

[0024] Optionally, the non-reactive gas I and the non-reactive gas II are independently selected from at least one of nitrogen, argon and helium.

[0025] Optionally, the time of the water introduction is 1s-1min.

[0026] Optionally, the time of the purging I and the purging II is independently selected from 5-60s.

[0027] Optionally, the pre-treatment in the step S1 is selected from at least one of grinding, annealing, degassing and cleaning.

[0028] Optionally, the time of the grinding is 5-30min.

[0029] Optionally, the number of cycles in the step S3 is 1-100.

[0030] According to another aspect of the present application, there is provided a ferroelectric overall water-splitting photocatalyst prepared by the preparation method of the ferroelectric overall water-splitting photocatalyst described above.

[0031] According to still another aspect of the present application, there is provided an application of the ferroelectric overall water-splitting photocatalyst described above in photocatalytic overall water splitting.

[0032] As an optional embodiment, the present application is implemented by the following technical solutions:

[0033] The method for preparing a ferroelectric high-efficiency full water-splitting photocatalyst comprises the following steps: firstly, grinding and dispersing the ferroelectric powder sample for pretreatment; then installing an atomic layer deposition source tank; then starting the powder atomic layer deposition system and setting the deposition temperature; placing the sample with deposited powder dispersed in the reaction tank; setting the deposition parameters of each step; depositing the sample surface for different numbers of cycles; and finally performing full water-splitting activity testing.

[0034] Optionally, the method comprises the following steps:

[0035] (1) The ferroelectric lead titanate powder is used as the modified and controlled object, and has poor photocatalytic water-splitting activity;

[0036] (2) The atomic layer deposition source is used for modifying the surface of the ferroelectric material to improve its activity;

[0037] (3) The powder atomic layer deposition system is used for precisely controlling the atomic layer deposition growth process;

[0038] (4) The photocatalytic testing system is used for testing the activity of the sample before and after modification.

[0039] Specifically, the method comprises the following steps:

[0040] (1) The single-domain ferroelectric lead titanate powder synthesized in advance is ground in a agate mortar for 30 minutes to fully disperse the agglomerated powder for standby;

[0041] (2) The appropriate source material is selected according to the desired deposited modification layer, and the source tank containing the source material is connected to the atomic layer deposition reaction system;

[0042] (3) The atomic layer deposition system is started, and the temperature of the source tank, pipeline, cavity and tail pipe is set according to the physical and chemical properties of the source material and the reaction conditions;

[0043] (4) The reaction tank containing the lead titanate powder is placed in the reaction cavity, and the cavity is in a vacuum state;

[0044] (5) The parameters of each step of atomic layer deposition and the number of deposition cycles are set, and then the deposition of a film with a specific thickness is started;

[0045] (6) After the atomic layer deposition is completed, the sample is tested for photocatalytic water-splitting.

[0046] In this application, atomic layer deposition can be precisely grown on the surface of a ferroelectric material. The principle is that the reaction source material is first chemically adsorbed on the surface of the ferroelectric material, and then forms pure oxides through hydrolysis or oxidation reaction. Under low vapor pressure, single adsorption is mainly single-layer adsorption and has small coverage, so growth can be performed at the single-cell level.

[0047] The growth reaction is based on the hydrolysis or oxidation of the reaction raw materials chemisorbed on the surface of the ferroelectric material. By selecting appropriate source ligands, theoretically, any substance can be grown on the ferroelectric powder material for modification. The present application modifies the ferroelectric powder material by atomic layer deposition, which can greatly improve the photocatalytic overall water splitting activity thereof.

[0048] In addition, according to the final activity test results, it can be confirmed that the activity is greatly improved, and the activity is affected by factors such as the type of growth material and the thickness of the growth material. Therefore, the ferroelectric photocatalytic material can be precisely controlled by this method, thereby effectively improving the activity thereof.

[0049] The beneficial effects that can be produced by the present application include:

[0050] (1) The present application precisely controls and modifies the surface of the ferroelectric material by atomic layer deposition technology, so that the ferroelectric material can efficiently photocatalyze overall water splitting. This method not only provides an experimental basis for studying the limiting factors of ferroelectric materials in photocatalytic reactions, but also provides a new idea for constructing efficient photocatalysts using the efficient charge separation and depolarization electric field of ferroelectric materials.

[0051] (2) The present application is based on the atomic layer deposition method, which can realize precise control of atomic layers through layer-by-layer growth.

[0052] (3) Based on the chemical adsorption principle of atomic layer deposition, the present application can select appropriate precursors, and theoretically almost any desired atomic layer can be grown.

[0053] (4) The atomic layer deposition method provided by the present application has a simple growth modification process and can effectively improve the activity. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 Figure is the overall water splitting activity graph of the ferroelectric material after atomic layer deposition of aluminum oxide in test example 1 of the present application;

[0055] Figure 2 Figure is the overall water splitting activity graph of the ferroelectric material after atomic layer deposition of titanium oxide in test example 1 of the present application;

[0056] Figure 3 Figure is the overall water splitting activity graph of the ferroelectric material after atomic layer deposition of silicon oxide in test example 1 of the present application. DETAILED DESCRIPTION

[0057] The present application will be described in detail below in conjunction with the examples, but the present application is not limited to these examples.

[0058] Unless otherwise specified, the raw materials in the examples of the present application are purchased through commercial channels.

[0059] The performance test is performed by using two Perfectlight Sci&Tech photocatalytic devices.

[0060] Example 1

[0061] Atomic layer deposition modification implementation of aluminum oxide:

[0062] (1) Put 300 mg of ferroelectric lead titanate powder into a marquis mortar and grind it for 30 minutes until the powder is fully dispersed;

[0063] (2) Carefully transfer the ground powder and evenly spread it into the atomic layer deposition reaction tank, and cover the reaction tank with a metal mesh with holes;

[0064] (3) Put the reaction tank with the powder into the atomic layer deposition reaction cavity;

[0065] (4) Connect the source tank containing 20 g of trimethylaluminum (aluminum oxide precursor) to the atomic layer deposition system, and connect the heating device;

[0066] (5) Turn on the atomic layer deposition system, and set the required temperatures of the reaction cavity, line and outlet to 100°C, 80°C and 80°C respectively, and wait for the temperature to stabilize to the preset value;

[0067] (6) According to the growth process, set each step as follows: in the first step, open the aluminum source valve for 3 s, and after passing through, keep it in the cavity for 40 s, pass it once, and close the reaction cavity to vacuum state; in the second step, pass nitrogen, the nitrogen flow is 100 sccm, the passing time is 60 s, after passing, keep it in the cavity for 1 s, the passing frequency is 3 times, and keep the reaction cavity in vacuum state; in the third step, pass water, the water valve is opened for 60 s, after passing, keep it in the cavity for 1 s, pass it once, and keep the reaction cavity in vacuum state; in the fourth step, pass nitrogen, the nitrogen flow is 100 sccm, the passing time is 60 s, after passing, keep it in the cavity for 1 s, the passing frequency is 3 times, and keep the reaction cavity in vacuum state; before each step, the cavity is evacuated to 0.24 Torr;

[0068] (7) Repeat the above steps 1-9 times according to the required number of cycles;

[0069] (8) After deposition, the atomic layer deposition modified ferroelectric material catalyst is obtained.

[0070] Example 2

[0071] Atomic layer deposition modification implementation of titanium oxide:

[0072] (1) Put 300 mg of ferroelectric lead titanate powder into a marquis mortar and grind it for 30 minutes until the powder is fully dispersed;

[0073] (2) Carefully transfer the ground powder and evenly spread it into an atomic layer deposition reaction tank, and cover the tank with a metal mesh with holes;

[0074] (3) Put the reaction tank with the powder into an atomic layer deposition reaction cavity;

[0075] (4) Connect a source tank containing 15 g of titanium tetrakis(dimethylamino) (titanium oxide precursor) to the atomic layer deposition system, and connect the heating device;

[0076] (5) Turn on the atomic layer deposition system, and set the required temperatures of the source tank, reaction cavity, line, and outlet to 80°C, 120°C, 150°C, and 80°C, respectively, and wait for the temperature to stabilize to the preset value;

[0077] (6) Set each step according to the growth process, open the titanium source valve for 12 s in the first step, keep the cavity for 60 s after the gas is turned off, and turn on the nitrogen gas for 60 s in the second step, keep the cavity for 1 s after the gas is turned off, and repeat the process 3 times while keeping the reaction cavity in a vacuum state; turn on the water valve for 60 s in the third step, keep the cavity for 1 s after the gas is turned off, and repeat the process 1 time while keeping the reaction cavity in a vacuum state; turn on the nitrogen gas for 60 s in the fourth step, keep the cavity for 1 s after the gas is turned off, and repeat the process 3 times while keeping the reaction cavity in a vacuum state; before each step, the cavity is evacuated to 0.24 Torr;

[0078] (7) Repeat steps 1-6 above according to the required number of cycles;

[0079] (8) After deposition, a titanium oxide atomic layer deposition modified ferroelectric material catalyst is obtained.

[0080] Example 3

[0081] Atomic layer deposition modification of silicon oxide:

[0082] (1) Take 300 mg of ferroelectric lead titanate powder and place it in a marquis mortar, and grind it for 30 minutes until the powder is fully dispersed;

[0083] (2) Carefully transfer the ground powder and evenly spread it into an atomic layer deposition reaction tank, and cover the tank with a metal mesh with holes;

[0084] (3) Put the reaction tank with the powder into an atomic layer deposition reaction cavity;

[0085] (4) Connect a source tank containing 10 g of silicon tetrachloride (silicon oxide precursor) to the atomic layer deposition system, and connect the heating device;

[0086] (5) Turn on the atomic layer deposition system, and set the reaction cavity, line and outlet at 40℃, 40℃ and 80℃, and wait for the temperature to stabilize to the preset value;

[0087] (6) According to the growth process, each step is set respectively, the first step, the pyridine valve is opened for 3s, and after the gas is passed, the cavity is kept for 60s, and the gas is passed once, and the reaction cavity is closed and vacuumized; the second step, the silicon source valve is opened for 2s, and after the gas is passed, the cavity is kept for 60s, and the gas is passed once, and the reaction cavity is closed and vacuumized; the third step, nitrogen gas is passed, the nitrogen gas flow is 100sccm, the passing time is 60s, the cavity is kept for 1s after the gas is passed, the passing frequency is 5 times, and the reaction cavity is kept vacuumized; the fourth step, the pyridine valve is opened for 3s, and after the gas is passed, the cavity is kept for 60s, and the gas is passed once, and the reaction cavity is closed and vacuumized; the fifth step, water is passed, the water valve is opened for 4s, and after the gas is passed, the cavity is kept for 1s, the gas is passed once, and the reaction cavity is kept vacuumized; the sixth step, nitrogen gas is passed, the nitrogen gas flow is 100sccm, the passing time is 60s, the cavity is kept for 1s after the gas is passed, the passing frequency is 5, and the reaction cavity is kept vacuumized; before each step is carried out, the cavity is vacuumized to 0.24Torr;

[0088] (7) According to the required number of cycles, the above steps are repeated 1-10 times;

[0089] (8) After the deposition is completed, the silicon oxide atomic layer deposition modified ferroelectric material catalyst is obtained.

[0090] Test Example 1

[0091] The aluminum oxide, titanium oxide and silicon oxide atomic layer deposition modified ferroelectric material catalysts prepared in Examples 1-3 are used as raw materials, 100mg is dispersed in a reactor containing 100mL of secondary deionized water, and the reactor is placed in a 15℃ constant temperature reaction water bath; 50μL of Rh solution with a concentration of 2mg / mL RhCl3·3H2O is added, stirred for 5min, and then irradiated under a 300W xenon lamp for 10min; 100μL of Cr solution with a concentration of 2mg / mL K2CrO4 is added, stirred for 5min, and then irradiated under a 300W xenon lamp for 5min; 25μL of Co solution with a concentration of 2mg / mL Co(NO3)2 is added, stirred for 5min, and then irradiated under a 300W xenon lamp for 5min; then the reactor is vacuumized for 30min to remove the air in the reactor; then the reaction is carried out under irradiation for 30min-1h, and the generated hydrogen and oxygen are detected by Agilent's 7890A gas chromatograph.

[0092] As shown in Figure 1 , from Figure 1As can be seen, before atomic layer deposition modification of lead titanate, the photocatalytic water splitting rates for H2 and O2 generation were 3.22 μmol / h and 1.37 μmol / h, respectively. After 3 cycles of alumina growth, the photocatalytic water splitting rates for H2 and O2 generation increased to 103.69 μmol / h and 70.00 μmol / h, respectively. After 5 cycles of alumina growth, the photocatalytic water splitting rates for H2 and O2 generation further increased to 160.08 μmol / h and 82.52 μmol / h, respectively. After 10 cycles of alumina growth, the photocatalytic water splitting rates for H2 and O2 generation decreased to 38.59 μmol / h and 12.26 μmol / h, respectively.

[0093] like Figure 2 As shown, from Figure 2 As can be seen, before atomic layer deposition modification of lead titanate, the photocatalytic water splitting rates for H2 and O2 generation were 3.22 μmol / h and 1.37 μmol / h, respectively. After 3 cycles of titanium dioxide growth, the photocatalytic water splitting rates for H2 and O2 generation increased to 103.84 μmol / h and 63.48 μmol / h, respectively. After 5 cycles of titanium dioxide growth, the photocatalytic water splitting rates for H2 and O2 generation further increased to 283.71 μmol / h and 136.28 μmol / h, respectively. After 7 cycles of titanium dioxide growth, the photocatalytic water splitting rates for H2 and O2 generation decreased to 66.48 μmol / h and 40.94 μmol / h, respectively.

[0094] like Figure 3 As shown, from Figure 3 As can be seen, before atomic layer deposition modification of lead titanate, the photocatalytic water splitting rates for H2 and O2 generation were 3.22 μmol / h and 1.37 μmol / h, respectively; after 5 cycles of silicon dioxide growth, the photocatalytic water splitting rates for H2 and O2 generation increased to 135.28 μmol / h and 61.05 μmol / h, respectively.

[0095] In summary, the activity results show that the modification significantly enhances the activity of lead ferroelectric titanate, and this activity is influenced by the number of alumina cycles. Furthermore, changing the growth material also improves the total water splitting activity to varying degrees, indicating that this method can precisely control the activity of ferroelectric materials and enhance their performance.

[0096] This application describes a method for preparing a highly efficient ferroelectric photocatalyst for complete water splitting, employing a standardized powder atomic layer deposition system. This method grows materials with varying atomic layer thicknesses on the surface of ferroelectric materials, and by modifying the surface layers, highly efficient water splitting activity can be achieved.

[0097] The above merely describes several embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with the preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the disclosed technical contents without departing from the scope of the technical solutions of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within the scope of the technical solutions.

Claims

1. A method for preparing a ferroelectric water-splitting photocatalyst, characterized in that, The preparation method includes the following steps: Step S1: Pre-treat the ferroelectric material to obtain pre-treated ferroelectric material; Step S2: After atomic layer deposition of the pretreated ferroelectric material and the metal-organic complex source material, inactive gas I is introduced for purging I, water is introduced, and inactive gas II is introduced again for purging II. Step S3: Based on the thickness of the ferroelectric water-splitting photocatalyst, repeat step S2 to obtain the ferroelectric water-splitting photocatalyst. In step S1, the ferroelectric material is selected from lead ferroelectric titanate; In step S2, the source material of the metal-organic complex is selected from at least one of alumina precursor, silicon oxide precursor, iron oxide precursor, and tin oxide precursor.

2. The preparation method according to claim 1, characterized in that, The alumina precursor is selected from at least one of trimethylaluminum, triethylaluminum, and dimethylaluminum chloride; The silica precursor is selected from at least one of triethylsilylamine and 1,1,1-tris(dimethylamino)ethylsilane; The iron oxide precursor is selected from at least one of ferrocene, bis(isopropylcyclopentadienyl)ferrocene, tert-butylferrocene, and tert-butoxide iron. The tin oxide precursor is selected from at least one of tetra(dimethylamino)tin, tetrapropyltin, diacetylacetonyl dibutyltin, and bis(N,N'-diisopropylethamidinyl)tin.

3. The preparation method according to claim 1, characterized in that, In step S2, the atomic layer deposition time is 5~120 s; The temperature of the atomic layer deposition includes the reaction source temperature and the reaction chamber temperature; The reaction source temperature is 25~120℃; The temperature of the reaction chamber is 40~200℃.

4. The preparation method according to claim 1, characterized in that, In step S2, the flow rates of the inactive gas I and the inactive gas II are independently selected from 0 to 100 sccm; The inactive gas I and inactive gas II are independently selected from at least one of nitrogen, argon, and helium.

5. The preparation method according to claim 1, characterized in that, The water introduction time is 1 s to 1 min; The durations of purge I and purge II are independently selected from 5 to 60 seconds.

6. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment method is selected from at least one of grinding, annealing, degassing, and cleaning; The grinding time is 5 to 30 minutes.

7. The preparation method according to claim 1, characterized in that, In step S3, the number of cycles is 1 to 100.

8. The ferroelectric water-splitting photocatalyst prepared by the method according to any one of claims 1 to 7.

9. The application of the ferroelectric water-splitting photocatalyst according to claim 8 in photocatalytic water splitting.

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