Preparation method and application of perovskite-type tantalum-based oxynitride photocatalyst
Synthesis and high-temperature lanthanide tantalum-based oxide precursors are carried by molten salt method, and the transition metal cocatalyst is supported to construct a low-defect perovskite tantalum-based oxynitride, which solves the multiphase in lanthanide oxynitride synthesis Generation and low-price defect problems have achieved efficient photocatalytic activity and stability, broadening its application prospects in the field of photocatalytics.
Patent Information
- Application Number
- CN202111433581.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-11-29
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2041-11-29
AI Technical Summary
In the field of photocatalysis, there are low-priced metal defects in tantalum-based oxygen nitride materials, which hinder the effective separation and transfer of photogenerated charges, resulting in low photocatalytic efficiency, and the synthesis of lanthanide oxygen nitrides is easy to generate heterophases, limiting the Its application.
The lanthanide tantalum-based oxide precursor RTaO4 was synthesized by molten salt method, and nitrided at high temperature under ammonia atmosphere. By carrying a transition metal cocatalyst, a low-deficiency perovskite tantalum-based oxide nitride RTaON2 was constructed to suppress low-price Generation of metal defects.
It realizes the efficient photocatalytic activity of perovskite tantalum-based oxynitride, improves the efficiency of photocatalytic reaction, stable chemical properties of the material, and simple and easy to operate in the synthesis process, which is suitable for large-scale promotion.
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Abstract
Description
Technical Field
[0001] The invention relates to a preparation method of a perovskite structure tantalum-based oxynitride and application thereof in the field of photocatalysis, belonging to the technical field of catalytic materials. Background Art
[0002] The photocatalytic reaction using semiconductors can be divided into three main steps: 1) light absorption, where electrons in the valence band absorb photons with energy greater than the band gap, and jump from the valence band to the conduction band to form photogenerated electrons and holes; 2) charge separation and transfer, where photogenerated electrons and holes are transferred from the bulk phase to the surface; 3) surface catalytic reaction, where photogenerated electrons participate in reduction reactions on the surface, and photogenerated holes participate in oxidation reactions on the surface. In order to fully utilize the energy contained in sunlight, semiconductors with a wide spectrum response are first required to effectively absorb photons. Studies have found that tantalum-based nitrides or oxynitrides have a small band gap (BaTaO2N 1.8 eV; Ta3N52.1 eV; TaON 2.4 eV), which can effectively utilize the visible light part that occupies most of the sunlight spectrum. At the same time, surface catalytic reactions require a suitable band structure to meet the requirements of thermodynamics and kinetics. The conduction band of tantalum-based oxynitride compounds is near -0.3 V, and as a class of materials with ideal band structures, they have attracted widespread attention. Tantalum-based oxynitrides have been extensively studied in areas including photocatalytic water decomposition, carbon dioxide reduction, oxygen reduction to produce hydrogen peroxide, and degradation of organic pollutants.
[0003] The separation and transfer of charges is a core issue in photocatalysis. The separation and transfer time scale of photogenerated electrons and holes in photocatalytic reactions is in the nanosecond order, but the recombination of photogenerated electrons and holes occurs in the picosecond order, which makes it easy for a large number of carriers to recombine during the separation and transfer process, and the efficiency of photocatalysis cannot be effectively improved. The recombination of photogenerated electrons and holes often uses low-valent metals as recombination sites, so an effective way to improve the efficiency of photocatalysis is to construct low-defect photocatalytic materials.
[0004] ABO3-type perovskite materials are a class of materials with excellent physical and chemical properties, and have attracted attention in many scenarios. The excellent performance of tantalum-based oxynitride compounds with perovskite structure in photocatalysis has also received widespread attention, including CaTaO2N, SrTaO2N, BaTaO2N, LaTaON2, etc. However, low-valent tantalum defects are inevitably generated during the synthesis process, which hinders the effective separation of photogenerated charges and leads to low photocatalytic performance. How to construct low-perovskite-structured tantalum-based oxynitride compounds is a difficult problem.
[0005] Lanthanide elements are elements with numbers 57-71 in the periodic table. They have similar atomic radii and exhibit similar chemical properties. Lanthanide atoms can be used as A-site framework atoms to construct the perovskite structure RTaON2. As the atomic number increases, the 4f orbital energy of lanthanide elements gradually decreases. At the same time, perovskite-type RTaON2 is challenging to synthesize. Oxynitrides are obtained by nitriding oxide precursors at high temperatures. General precursors can be obtained by direct solid phase method and polymer composite method. The direct solid phase method synthesizes lanthanide tantalum-based oxide precursors. Since tantalum oxide and lanthanide oxide are in solid-phase solid-phase contact, the limited contact area causes uneven mass transfer, and the pure phase of lanthanide tantalum-based oxide is often not obtained. There may be multiple phases coexisting (RTaO4, R3TaO7, Ta2O5, R2O3, etc.). The oxide precursor is obtained by using the polymer composite method, which requires the use of organic reagents including citric acid, ethylene glycol, methanol, etc., which is not conducive to environmental protection. On the other hand, the nitridation of lanthanide oxides will also generate multiphase oxynitrides, including perovskite structure RTaON2 and pyrochlore phase R2Ta2O5N2. These factors limit the synthesis of lanthanide oxynitrides and their application in the field of photocatalysis. Summary of the invention
[0006] In view of the difficulty in constructing perovskite-structured tantalum-based oxynitride and its application in photocatalysis, the present invention aims to develop a new strategy to utilize lanthanide atoms with lower 4f orbitals as A sites and utilize the energy-reduced 4f orbitals to protect Ta 5+ It is not reduced during the high-temperature nitridation process, which inhibits the generation of low-valent metal defects during the nitridation process. The specific technical solution is to use the molten salt method to synthesize RTaO4 (R is at least one of Sm, Eu, and Gd) as an oxide precursor, and perform high-temperature nitridation in an ammonia atmosphere to achieve the synthesis of perovskite-type oxynitride compounds RTaON2. By supporting transition metal co-catalysts, lanthanide tantalum-based oxynitrides can undergo catalytic reactions under light conditions, and their application in the photolysis of water to produce hydrogen half-reaction, oxygen production half-reaction, and carbon dioxide reduction half-reaction all achieves excellent photocatalytic activity. Multiphase photocatalytic experiments show that the perovskite-type tantalum-based oxynitrides involved in the present invention have good application prospects in the field of photocatalysis.
[0007] In order to achieve the above object, the technical solution of the present invention is as follows:
[0008] A first aspect of the present invention provides a method for preparing a perovskite-type tantalum-based oxynitride photocatalyst, the method comprising the following steps:
[0009] (1) R2O3, Ta2O5 and MCl are mixed and calcined;
[0010] R is at least one of Sm, Eu, and Gd, and M is at least one of Li, Na, K, Rb, and Cs;
[0011] (2) cooling the calcined product obtained in step (1), washing it with water to remove MCl, and then drying it to obtain RTaO4;
[0012] (3) nitriding the RTaO4 obtained in step (2) in a reactor with an ammonia gas flow to obtain a perovskite-type tantalum-based oxynitride compound RTaON2;
[0013] (4) Loading transition metal on the RTaON2 obtained in step (3) to obtain a perovskite-type tantalum-based oxynitride photocatalyst.
[0014] In the above technical solution, further, the molar ratio of R2O3, Ta2O5 and MCl is 1:1:(2~1000).
[0015] In the above technical solution, further, in the step (1), the calcination temperature is 10-1000° C. higher than the melting point of MCl, and the calcination time is 2-100 h.
[0016] In the above technical solution, further, in the step (3), the flow rate of the ammonia gas flow is 100-5000 ml / min; the nitriding temperature is 800-1200° C., and the nitriding time is 1-30 h.
[0017] In the above technical solution, further, in the step (4), the transition metal includes at least one of Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt, and Au; and the loading amount of the transition metal is 0.01 to 5 wt%.
[0018] In the above technical solution, further, the loading method in step (4) is:
[0019] (1) Immerse the RTaON2 powder in the transition metal precursor solution, disperse it ultrasonically and evaporate it in a water bath;
[0020] (2) Reduction at 100-500°C for 0.1-5h under a hydrogen flow; or treatment at 200-800°C for 0.1-5h under an ammonia flow, followed by calcination at 100-500°C for 0.1-5h under an air atmosphere; or calcination at 100-500°C for 0.1-5h under a nitrogen or argon inert atmosphere.
[0021] The second aspect of the present invention provides a perovskite-type tantalum-based oxynitride photocatalyst prepared by the above-mentioned preparation method, wherein the tantalum-based oxynitride compound has Ta 5+ The molar ratio of Ta / Ta is greater than 80%.
[0022] The third aspect of the present invention provides a use of the above-mentioned perovskite-type tantalum-based oxynitride photocatalyst in photocatalytic degradation of organic matter.
[0023] The fourth aspect of the present invention provides an application of the above-mentioned perovskite-type tantalum-based oxynitride photocatalyst in a photocatalytic hydrogen production reaction, wherein one or more of sodium sulfide, sodium sulfite, ascorbic acid, formic acid, methanol, and triethanolamine are used as hole sacrificial reagents and dispersed in H2O together with catalyst powder, and H2O is decomposed by light to produce hydrogen.
[0024] The fifth aspect of the present invention provides an application of the above-mentioned perovskite-type tantalum-based oxynitride photocatalyst in the photocatalytic water decomposition oxygen production reaction, wherein Ag + , Fe 3+ , IO 3- ,Fe(SCN)6 3- One or more of them are used as hole sacrificial reagents and dispersed in H2O together with catalyst powder, and H2O is decomposed by light to produce oxygen.
[0025] The beneficial effects of the present invention are:
[0026] ①The synthesis process is simple and easy to operate, and easy to promote and apply on a large scale.
[0027] ② The catalyst yield is high and the obtained functional materials have stable chemical properties.
[0028] ③The synthesized catalyst has low defect density and wide spectrum absorption, and has potential application value in multiple photocatalytic reactions. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 Characterization diagram of the sample of Example 1, including (a) XRD spectra of GdTaON2 and GdTaO4 powders; (b) schematic diagram of the perovskite structure GdTaON2 unit cell; (c) scanning electron microscope image of GdTaON2;
[0030] Figure 2 Characterization diagram of the sample of Example 4, including (a) XRD spectra of SmTaON2 and SmTaO4 powders; (b) schematic diagram of the perovskite structure SmTaON2 unit cell; (c) scanning electron microscope image of SmTaON2;
[0031] Figure 3 The UV-visible absorption spectra of the samples of the present invention are shown in Figures 1 and 2, including (a) the UV-visible absorption spectra of the GdTaO4 and GdTaON2 samples prepared in Example 1; (b) the UV-visible absorption spectra of the SmTaO4 and SmTaON2 samples prepared in Example 4; (c) the Ta 4f XPS peak spectrum of the GdTaON2 sample prepared in Example 1; (d) the Ta 4f XPS peak spectrum of the SmTaON2 sample prepared in Example 4;
[0032] Figure 4The activity diagrams of the photocatalyst prepared in the present invention in different photocatalytic reactions, wherein (a) is the activity diagram of the photocatalytic water decomposition and hydrogen production of GdTaON2 loaded with 1 wt% platinum in Application Example 1; (b) is the activity diagram of the photocatalytic water decomposition and oxygen production of GdTaON2 loaded with 2 wt% cobalt in Application Example 2. DETAILED DESCRIPTION
[0033] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.
[0034] Example 1
[0035] (1) To synthesize the oxide precursor GdTaO4, Gd2O3, Ta2O5 and RbCl were added in a molar ratio of 1:1:30, mixed evenly in a container, and then transferred to an alumina crucible. The temperature was raised to 1000 °C at a rate of 5 °C / min, maintained for 20 h, and then naturally cooled. The obtained solid was washed with double distilled water to remove the molten salt RbCl. The remaining powder was placed at 120 °C for 24 h to dry to obtain the oxide gadolinium tantalate GdTaO4;
[0036] (2) Nitriding pipeline connection: GdTaO4 powder is placed in an alumina magnetic boat, and the magnetic boat is placed in the center of the quartz tube. The gas inlet of the quartz tube is connected to the gas path containing ammonia, and the gas outlet is connected to the tail gas absorption device;
[0037] (3) Nitriding to obtain GdTaON2, ammonia gas was introduced into the pipeline at a flow rate of 500 ml / min, and the air was purged at room temperature for 1 h. Then the temperature was raised from room temperature to 1000 °C at a rate of 5 °C / min, and the temperature was kept at 1000 °C for 20 h for nitridation. The temperature was naturally cooled to room temperature to obtain a perovskite structure tantalum-based oxynitride compound powder GdTaON2;
[0038] (4) Loading the co-catalyst: 1 g of GdTaON2 powder was immersed in a chloroplatinic acid solution with a platinum content of 1 wt%, dispersed by ultrasonication, evaporated in a water bath, and reduced at 200 °C for 3 h under a hydrogen flow.
[0039] Example 2
[0040] (1) To synthesize the oxide precursor GdTaO4, Gd2O3, Ta2O5 and NaCl were added in a molar ratio of 1:1:50, mixed evenly in a container, and then transferred to an alumina crucible. The temperature was raised to 1000°C at a rate of 5°C / min, maintained for 20 h, and then naturally cooled. The obtained solid was washed with double distilled water to remove the molten salt NaCl, and the remaining powder was placed at 120°C for 24 h to dry to obtain the oxide gadolinium tantalate GdTaO4.
[0041] (2) Nitriding pipeline connection: GdTaO4 powder is placed in an alumina magnetic boat, and the magnetic boat is placed in the center of the quartz tube. The gas inlet of the quartz tube is connected to the gas path containing ammonia, and the gas outlet is connected to the tail gas absorption device;
[0042] (3) Nitriding to obtain GdTaON2, ammonia gas was introduced into the pipeline at a flow rate of 500 ml / min, and the air was purged at room temperature for 1 h. Then the temperature was raised from room temperature to 1000 °C at a rate of 5 °C / min, and the temperature was kept at 1000 °C for 20 h for nitridation. The temperature was naturally cooled to room temperature to obtain a perovskite structure tantalum-based oxynitride compound powder GdTaON2;
[0043] (4) Supporting promoter: 1 g of GdTaON2 powder was immersed in a cobalt nitrate solution with a cobalt content of 2 wt%, dispersed by ultrasonic and then evaporated in a water bath, treated at 650 °C for 2 h under ammonia flow, and then calcined at 200 °C for 1 h in an air atmosphere.
[0044] Example 3
[0045] (1) Synthesize the oxide precursor GdTaO4, add Gd2O3, Ta2O5, NaCl, and KCl in a molar ratio of 1:1:25:25, mix them evenly in a container, transfer them to an alumina crucible, heat them to 1000°C at 5°C / min, keep them for 20 h, then cool them naturally, wash the obtained solid with double distilled water to remove the molten salts NaCl and KCl, and dry the remaining powder at 120°C for 24 h to obtain the oxide gadolinium tantalate GdTaO4;
[0046] (2) Nitriding pipeline connection: GdTaO4 powder is placed in an alumina magnetic boat, and the magnetic boat is placed in the center of the quartz tube. The gas inlet of the quartz tube is connected to the gas path containing ammonia, and the gas outlet is connected to the tail gas absorption device;
[0047] (3) Nitridation to obtain GdTaON2. Ammonia gas was introduced into the pipeline at a flow rate of 500 ml / min, and the air was purged at room temperature for 1 h to exclude air. The temperature was then raised from room temperature to 1000 °C at a rate of 5 °C / min, and the temperature was kept at 1000 °C for 20 h for nitridation. The temperature was naturally cooled to room temperature to obtain a perovskite structure tantalum-based oxynitride compound powder GdTaON2.
[0048] (4) Loading the co-catalyst: 1 g of GdTaON2 powder was immersed in 1 wt% gold in chloroauric acid solution, 1 wt% palladium in sodium chloropalladate solution, 1 wt% platinum in chloroplatinic acid solution, and 1 wt% copper in copper nitrate solution, respectively. After ultrasonic dispersion, the mixture was evaporated in a water bath and reduced at 200 °C for 3 h in a hydrogen atmosphere.
[0049] Example 4
[0050] (1) To synthesize the oxide precursor SmTaO4, Sm2O3, Ta2O5, and RbCl were added in a molar ratio of 1:1:50, mixed evenly in a container, and then transferred to an alumina crucible. The temperature was raised to 1000 °C at 5 °C / min, maintained for 20 h, and then cooled naturally. The obtained solid was washed with double distilled water to remove the molten salt RbCl. The remaining powder was placed at 120 °C for 24 h to dry to obtain the oxide samarium tantalate SmTaO4;
[0051] (2) Nitriding pipeline connection: SmTaO4 powder is placed in an alumina magnetic boat, and the magnetic boat is placed in the center of the quartz tube. The gas inlet of the quartz tube is connected to the gas path containing ammonia, and the gas outlet is connected to the tail gas absorption device;
[0052] (3) Nitriding to obtain SmTaON2, ammonia gas was introduced into the pipeline at a flow rate of 500 ml / min, and the air was purged at room temperature for 1 h. Then the temperature was raised from room temperature to 1000 °C at a rate of 2 °C / min, and the temperature was kept at 1000 °C for 20 h for nitridation. The temperature was naturally cooled to room temperature to obtain a perovskite structure tantalum-based oxynitride compound powder SmTaON2;
[0053] (4) Supporting the co-catalyst: 1 g of SmTaON2 powder was immersed in a chloroplatinic acid solution with a platinum content of 1 wt%, dispersed by ultrasonication, evaporated in a water bath, and reduced at 200 °C for 3 h under a hydrogen flow.
[0054] Example 5
[0055] (1) To synthesize the oxide precursor SmTaO4, Sm2O3, Ta2O5 and NaCl were added in a molar ratio of 1:1:50, mixed evenly in a container, and then transferred to an alumina crucible. The temperature was raised to 1000°C at a rate of 5°C / min, maintained for 20 h, and then naturally cooled. The obtained solid was washed with double distilled water to remove the molten salt NaCl. The remaining powder was placed at 120°C for 24 h and dried to obtain the oxide samarium tantalate SmTaO4;
[0056] (2) Nitriding pipeline connection: SmTaO4 powder is placed in an alumina magnetic boat, and the magnetic boat is placed in the center of the quartz tube. The gas inlet of the quartz tube is connected to the gas path containing ammonia, and the gas outlet is connected to the tail gas absorption device;
[0057] (3) Nitriding to obtain SmTaON2. Ammonia gas was introduced into the pipeline at a flow rate of 500 ml / min, and the air was purged at room temperature for 1 h to exclude air. The temperature was then raised from room temperature to 1000 °C at a rate of 2 °C / min, and the temperature was kept at 1000 °C for 20 h for nitriding. The temperature was then naturally cooled to room temperature to obtain a perovskite structure tantalum-based oxynitride compound powder SmTaON2.
[0058] (4) Supporting promoter: 1 g SmTaON2 powder was immersed in a cobalt nitrate solution with a cobalt content of 2 wt%, dispersed by ultrasonic and then evaporated in a water bath, reduced at 650 °C for 2 h under ammonia flow, and then calcined at 200 °C for 1 h in an air atmosphere.
[0059] Example 6
[0060] To synthesize the oxide precursor SmTaO4, Sm2O3, Ta2O5, NaCl and KCl were added in a molar ratio of 1:1:25:25, mixed evenly in a container, transferred to an alumina crucible, heated to 1000°C at 5°C / min, maintained for 20 h and then cooled naturally, the obtained solid was washed with double distilled water to remove the molten salts NaCl and KCl, and the remaining powder was placed at 120°C for 24 h to dry to obtain the oxide samarium tantalate SmTaO4;
[0061] (2) Nitriding pipeline connection: SmTaO4 powder is placed in an alumina magnetic boat, and the magnetic boat is placed in the center of the quartz tube. The gas inlet of the quartz tube is connected to the gas path containing ammonia, and the gas outlet is connected to the tail gas absorption device;
[0062] (3) Nitriding to obtain SmTaON2, ammonia gas was introduced into the pipeline at a flow rate of 500 ml / min, and the air was purged at room temperature for 1 h. Then the temperature was raised from room temperature to 1000 °C at a rate of 2 °C / min, and the temperature was kept at 1000 °C for 20 h for nitridation. The temperature was naturally cooled to room temperature to obtain a perovskite structure tantalum-based oxynitride compound powder SmTaON2;
[0063] (4) Supporting promoter: 1 g SmTaON2 powder was immersed in a ruthenium nitrate solution with a 1 wt% ruthenium content, ultrasonically dispersed, evaporated in a water bath, and calcined at 350 °C for 2 h in a nitrogen atmosphere.
[0064] Figure 1 (a) is the powder XRD spectrum of samples GdTaO4 and GdTaON2 of Example 1, proving that the perovskite structured GdTaON2 was synthesized by nitriding the single-phase oxide precursor GdTaO4; Figure 1 (b) is a schematic diagram of the crystal structure of the perovskite-structured GdTaON2 of Example 1, obtained by refining the XRD data of GdTaON2, showing the coordination bonding relationship of each atom in GdTaON2; Figure 1 (c) is a scanning electron microscope image of the GdTaON2 sample of Example 1, showing the microscopic morphology, which is an accumulation of particles of hundreds of nanometers in size.
[0065] Figure 2(a) is the powder XRD spectrum of the samples SmTaO4 and SmTaON2 of Example 4, proving that the perovskite-structured SmTaON2 was synthesized by nitriding the single-phase oxide precursor SmTaO4; Figure 2 (b) is a schematic diagram of the crystal structure of the perovskite-structured SmTaON2 of Example 4, obtained by refining the SmTaON2 XRD data, showing the coordination bonding relationship of each atom in SmTaON2; Figure 2 (c) is a scanning electron microscope image of the sample SmTaON2 of Example 4, showing the microscopic morphology, which is an accumulation of particles of hundreds of nanometers in size.
[0066] Figure 3 The following are UV-visible absorption spectra, (a) is the UV-visible absorption of samples GdTaO4 and GdTaON2 prepared in Example 1, and (b) is the UV-visible absorption of samples SmTaO4 and SmTaON2 prepared in Example 4, indicating that the light absorption range of the material is broadened by nitridation. The low tail band absorption of GdTaON2 and SmTaON2 in the UV-visible absorption spectrum also indicates their low-defect properties, proving the effectiveness of designing and synthesizing low-defect tantalum-based oxynitride compounds by reducing the 4f orbital.
[0067] Figure 3 (c) Ta 4f XPS peak spectrum of the GdTaON2 sample prepared in Example 1; Figure 3 (d) Ta 4f XPS peak spectrum of the SmTaON2 sample prepared in Example 4; the Ta 4f peak results show that high-valent tantalum occupies the main part, and low-valent tantalum accounts for a very small proportion, which directly illustrates the effectiveness of using the reduced 4f orbital to suppress the formation of low-valent tantalum.
[0068] Application Example 1
[0069] The photocatalytic decomposition of water to produce hydrogen was carried out in a top-illuminated Pyrex glass reactor with a constant temperature water bath at 15°C. Example 1 prepared a composite photocatalyst, 50 mg of which was ultrasonically dispersed in 100 mL of a solution (containing 20 vol% CH3OH as a sacrificial reagent). The air in the reactor was removed by vacuuming, a xenon lamp was used as a light source, and photons in the ultraviolet part were filtered through a filter (λ≥420 nm). The hydrogen production activity of the catalyst under visible light was tested.
[0070] Application Example 2
[0071] The photocatalytic decomposition of water to produce hydrogen was carried out in a top-illuminated Pyrex glass reactor with a constant temperature water bath at 15°C. Example 2 prepared a composite photocatalyst, 50 mg of which was ultrasonically dispersed in 100 mL of a solution (containing 0.01 M AgNO3 as a sacrificial reagent). The air in the reactor was removed by vacuuming, a xenon lamp was used as a light source, and the ultraviolet light was filtered through a filter (λ≥420 nm). The oxygen production activity of the catalyst under visible light was tested.
[0072] Figure 4 The photocatalytic activity diagram of Application Examples 1-2 illustrates that this type of catalyst can be applied to multiple reactions in photocatalysis.
Claims
1. A method for preparing a perovskite-type tantalum-based oxynitride photocatalyst, characterized in that: The method comprises the following steps: (1) R2O3, Ta2O5 and MCl are mixed and then calcined, the molar ratio of R2O3, Ta2O5 and MCl is 1:1:(2~1000), the calcination temperature is 10~1000℃ higher than the melting point of MCl, and the calcination time is 2~100h; R is at least one of Sm, Eu, and Gd, and M is at least one of Li, Na, K, Rb, and Cs; (2) cooling the calcined product obtained in step (1), washing it with water to remove MCl, and then drying it to obtain RTaO4; (3) nitriding the RTaO4 obtained in step (2) in a reactor with an ammonia gas flow, wherein the flow rate of the ammonia gas flow is 100-5000 ml / min, the nitriding temperature is 800-1200° C., and the nitriding time is 1-30 h, to obtain a perovskite-type tantalum-based oxynitride compound RTaON2; (4) Loading the RTaON2 obtained in step (3) with a transition metal in an amount of 0.01 to 5 wt % to obtain a perovskite-type tantalum-based oxynitride photocatalyst.
2. The preparation method according to claim 1, characterized in that: In the step (4), the transition metal is selected from at least one of Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt and Au.
3. The preparation method according to claim 1, characterized in that: The loading method in step (4) is: (1) Immerse the RTaON2 powder in the transition metal precursor solution, disperse it ultrasonically and evaporate it in a water bath; (2) Reduction at 100-500°C for 0.1-5h under hydrogen flow; Or treat at 200~800℃ for 0.1~5h under ammonia gas flow, and then calcine at 100~500℃ for 0.1~5h under air atmosphere; Or calcine at 100~500℃ for 0.1~5h in an inert atmosphere of nitrogen or argon.
4. A perovskite-type tantalum-based oxynitride photocatalyst prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The tantalum-based oxynitride compound contains Ta 5+ The molar ratio of Ta / Ta is greater than 80%.
5. Use of the perovskite-type tantalum-based oxynitride photocatalyst according to claim 4 in a photocatalytic hydrogen production reaction, characterized in that: One or more of sodium sulfide, sodium sulfite, ascorbic acid, formic acid, methanol, and triethanolamine are used as hole sacrificial reagents and dispersed in H2O together with catalyst powder, and H2O is decomposed by light to generate hydrogen.
6. Use of the perovskite-type tantalum-based oxynitride photocatalyst according to claim 4 in a photocatalytic water decomposition oxygen production reaction, characterized in that: Ag + , Fe 3+ , IO 3- ,Fe(SCN)6 3- One or more of them are used as hole sacrificial reagents and dispersed in H2O together with catalyst powder, and H2O is decomposed by light to produce oxygen.