Preparation method and application of high-crystallinity stannous niobate single crystal with controllable size

Abstract

The invention provides a preparation method and application of a size-controllable high-crystallinity stannous niobate single crystal. The preparation method comprises the following steps: mixing stannous chloride, niobium pentoxide and halogenated metal salt by adopting a molten salt method to obtain a mixed salt, carrying out molten salt reaction on the mixed salt in an inert gas atmosphere, and annealing to obtain the high-crystallinity stannous niobate single crystal from the nanometer level to the micron level. According to the technical scheme, the metal salt with the low melting point serves as a reaction medium and is evenly mixed with niobium oxide and stannous chloride to be subjected to the molten salt reaction, the high-crystallinity stannous niobate single crystal material with the controllable size can be prepared by adjusting the technological conditions and the proportion of the raw materials in the reaction process, single crystals with the uniform size are obtained, and the preparation method is simple and easy to implement. The effective migration distance of carriers can be effectively controlled, so that the carriers can be transmitted to the surface of the single crystal from the inside to react, and stannous niobate single crystal materials with different sizes can be obtained according to actual requirements.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, specifically to a method for preparing and applying highly crystalline tin niobate single crystals with controllable dimensions. Background Technology

[0002] Rapid economic and industrial development has led to a dramatic depletion of fossil fuel reserves, accompanied by serious environmental problems. Therefore, the development of renewable secondary clean energy is a crucial direction for future sustainable economic development. On the one hand, the sun can radiate 3.0 x 10⁻⁶ ppm of solar energy to Earth annually. 24 J's energy, but the Earth's annual energy consumption is 3*10 20 J is only one ten-thousandth of the energy of solar energy. Solar energy is a clean and renewable energy source, so its utilization can alleviate or even solve the energy crisis facing humanity. On the other hand, hydrogen is an energy source with high energy density. It can be directly burned to produce enormous energy and pollution-free water, or used as a raw material for hydrogen-oxygen fuel cells to convert chemical energy into electrical energy, or combined with low-value organic matter to form high-value organic matter. It is a highly efficient, renewable, and clean energy source.

[0003] Photocatalysis, or photoelectrocatalysis, is a potential method to reduce or oxidize water or organic matter by absorbing sunlight through semiconductors, thereby producing clean hydrogen or high-value organic compounds to fill future energy shortages. However, this method places high demands on semiconductors, requiring not only suitable band gaps and band positions, but also crystallinity, morphology, and surface characteristics, which are key factors affecting its performance. Crystals include single crystals and polycrystalline materials. Polycrystalline materials have grain boundaries, where electrons and holes often recombine. Therefore, single crystals also have better charge transport capabilities than polycrystalline materials. The degree of crystallinity determines the effective migration distance of charge carriers. If the effective migration distance of charge carriers is greater than the grain size, charges can be transported from the inside to the surface for reaction. Conversely, if the effective migration distance is less than the grain size, charge carriers will recombine inside the material, failing to achieve the purpose of reducing hydrogen or producing high-value organic compounds. Therefore, the regulation of crystallinity and morphology is also an effective means to optimize photoelectrocatalysis or photocatalysis.

[0004] Tin niobate has a suitable band gap and band position for photoelectrochemical hydrogen production, with the potential for full water splitting and a theoretical photocurrent of 7.7 mA. This makes tin niobate itself a highly promising material for photoelectrochemical water splitting. However, its photoelectrochemical performance is currently at a low level, and the photocurrent value of actual products is far lower than its theoretical photocurrent value.

[0005] Due to the instability of Sn(II), it is inevitably oxidized to tetravalent Sn(IV) during the traditional wet reaction process. This results in tetravalent Sn(IV) occupying Nb(V) positions in the prepared tin niobate SnNb₂O₆, leading to hole compensation and giving SnNb₂O₆ a p-type characteristic. Furthermore, tin niobate obtained at low temperatures tends to form an incomplete core-shell structure, resulting in poor crystallinity, high bulk resistivity, and internal defects that can form electron-hole recombination centers, reducing the photoelectrocatalytic activity of tin niobate.

[0006] Based on this, the present invention provides a method for preparing highly crystalline tin niobate single crystals with controllable size to obtain tin niobate materials with high crystallinity at the nanometer to micrometer level, and the size of the single crystal can be controlled according to actual needs. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing and applying highly crystalline tin niobate single crystals with controllable size. This method not only obtains highly crystalline tin niobate single crystals but also allows for the controllable preparation of various sizes from nanometers to micrometers by adjusting process conditions. Furthermore, the reaction conditions are mild and the process is simple.

[0008] To achieve the above objectives, the present invention provides a method for preparing highly crystalline stannous niobate single crystals with controllable size, comprising mixing stannous chloride, niobium pentoxide and a Group 7 halogenated potassium salt or a Group 1 chlorinated metal salt using a molten salt method, reacting the mixture under an inert gas atmosphere, and then annealing to obtain nano- to micron-sized stannous niobate single crystals.

[0009] Preferably, the halometal salt includes a Group 7 potassium halo or a Group 1 chloride metal salt.

[0010] Preferably, the mass of the halometal salt added is 0 to 90% of the sum of the masses of the halometal salt and stannous chloride.

[0011] Preferably, the niobium / tin atomic ratio is between 0.42 and 20:1.

[0012] Preferably, the particle size of the highly crystalline tin niobate single crystal is 300 nm to 30 μm.

[0013] Preferably, the conditions for the molten salt reaction include a reaction temperature of 300~600℃, a reaction time of 3~24h, and a heating rate of 1℃ / min~20℃ / min.

[0014] Preferably, the inert gas includes argon or nitrogen.

[0015] Preferably, the molten salt reaction is carried out in a flowing atmosphere; the flow rate of the flowing atmosphere is 10~600 mL / min.

[0016] Preferably, the annealing includes annealing in an inert gas atmosphere, with an annealing temperature of 700-900℃ / min and an annealing time of 2h-24h.

[0017] As one preferred embodiment, the preparation method includes the following specific steps: (1) After mixing stannous chloride, niobium pentoxide and halide metal salt, grind them in an inert atmosphere for 10 min to 2 h until they are completely mixed and homogeneous to obtain a mixture; (2) The mixture is transferred to a quartz boat and reacted at 300℃~600℃ for 3h~24h in an inert atmosphere to obtain the reaction product; (3) The reaction product is washed with acid solution until it is neutral, filtered and vacuum dried, and the powder is annealed at 700~900℃ for 2~24h to obtain the highly crystalline tin niobate single crystal.

[0018] The tin niobate single crystal material obtained by the preparation method of the size-controllable highly crystalline tin niobate single crystal based on the above technical solution can be used as a catalyst in photocatalysis and photoelectrocatalysis reactions, or as a semiconductor material in semiconductor-related fields.

[0019] The beneficial technical effects obtained by this invention are as follows: 1. The present invention employs a molten salt method, using a low-melting-point metal salt as the reaction medium. After uniform mixing with niobium oxide and stannous chloride, a molten salt reaction is carried out. By adjusting the process conditions and the proportion of raw materials during the reaction, the preparation of highly crystalline stannous niobate single crystal materials with controllable size can be achieved. This overcomes the influence of hydrothermal methods and solid-state methods on the size and morphology of single crystal materials during the reaction process in existing technologies, resulting in uniform-sized single crystals. It can effectively control the effective migration distance of charge carriers, enabling them to be transported from the interior to the surface of the single crystal for reaction. Furthermore, stannous niobate single crystal materials of different sizes can be obtained according to actual needs.

[0020] 2. The present invention provides a highly crystalline tin niobate single crystal material obtained by the molten salt method. On the one hand, the single crystal has no recombination centers caused by grain boundaries, and the controllable grain size can be used to screen out conditions below the effective charge transport distance to optimize its photoelectric performance. On the other hand, the single crystal has higher crystallinity than the prior art, which can reduce the material resistance and thus reduce recombination inside the material. Attached Figure Description

[0021] Figures 1a-1cThe images shown are electron microscope (EM) images of tin niobate single crystals prepared in Examples 1, 2, and 1 of this invention, respectively.

[0022] Figures 2a-2d The images shown are electron microscope (EM) images of the tin niobate single crystals prepared in Examples 3-6 of this invention.

[0023] Figure 3 This is an electron microscope image of the tin niobate single crystal prepared in Example 7 of the present invention.

[0024] Figure 4 This is an electron microscope image of the tin niobate single crystal prepared in Example 8 of the present invention.

[0025] Figure 5a , Figure 5b and Figure 5c Electron micrographs of stannous niobate single crystals provided in Examples 9, 10, and Comparative Example 2, respectively.

[0026] Figure 6 The image shown is the xrd plot of the tin niobate single crystal obtained in Example 11 of this invention.

[0027] Figure 7 The image shows the XRD pattern of the tin niobate single crystal obtained after annealing at 900℃ in Example 11 of this invention.

[0028] Figure 8 This is an electron microscope image of a tin niobate single crystal provided in Example 11 of the present invention.

[0029] Figure 9 This is an electron microscope image of the stannous niobate single crystal of Comparative Example 3 of the present invention.

[0030] Figure 10 The above are comparison graphs of photocurrent-voltage curves of tin niobate single crystals in Comparative Example 3 and Example 11 of this invention. Detailed Implementation

[0031] In view of the deficiencies of the prior art, this invention proposes a method for preparing and applying highly crystalline stannous niobate single crystals with controllable size. The specific technical solution of this invention is described in detail below through specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. For the sake of brevity, this specification cannot provide a detailed description of all features of the actual embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] It should be noted that, unless otherwise defined, the technical or scientific terms used in this specification should be known to those skilled in the art described in this application.

[0033] The present invention provides a method for preparing highly crystalline stannous niobate single crystals with controllable size, comprising mixing stannous chloride, niobium pentoxide and a Group 7 halogenated potassium salt or a Group 1 chlorinated metal salt using a molten salt method, reacting the mixture under an inert gas atmosphere, and then annealing to obtain nano- to micron-sized stannous niobate single crystals.

[0034] Preferably, the halometal salt includes a Group 7 potassium halo or a Group 1 chloride metal salt.

[0035] Preferably, the mass of the halometal salt added is 0 to 90% of the sum of the masses of the halometal salt and stannous chloride.

[0036] The technical solution of the present invention and its resulting technical effects will be explained in detail below through specific implementation regulations.

[0037] Example 1 This embodiment provides a method for preparing highly crystallinity stannous niobate single crystals with controllable size, the specific steps of which include: Weigh 0.2g of niobium pentoxide, 2.85g of stannous chloride and 1.67g of potassium chloride (37%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 300mL / min and heat it to 400℃ at a heating and cooling rate of 4℃ / min for 2h. Wash the resulting yellow powder with 3M hydrochloric acid and dilute it with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6h. Anneal the powder at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0038] See Figure 1a This is an electron microscope image of the stannous niobate single crystal prepared in this embodiment.

[0039] Example 2 This embodiment provides a method for preparing highly crystallinity stannous niobate single crystals with controllable size, the specific steps of which include: Weigh 0.2g of niobium pentoxide, 2.85g of stannous chloride and 3.48g of potassium chloride (55%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Argon gas is introduced at a flow rate of 300mL / min and the temperature is raised to 400℃ at a heating and cooling rate of 4℃ / min for 2h. The resulting yellow powder is washed with 3M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. The yellow powder is filtered and dried in a vacuum oven at 60℃ for 6h. The powder is then annealed at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0040] See Figure 1bThe image shown is a morphology diagram of the stannous niobate single crystal provided in this embodiment, and... Figure 1a In comparison, the single crystal in this embodiment has a significantly larger particle size.

[0041] Example 3 This embodiment provides a method for preparing highly crystallinity stannous niobate single crystals with controllable size, the specific steps of which include: Weigh 1.34g of niobium pentoxide, 2.85g of stannous chloride and 1.67g of potassium chloride (37%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Argon gas is introduced at a flow rate of 300mL / min and the temperature is raised to 400℃ at a heating and cooling rate of 4℃ / min for 2h. The resulting yellow powder is washed with 3M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. The yellow powder is filtered and dried in a vacuum oven at 60℃ for 6h. The powder is then annealed at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0042] Example 4 This embodiment provides a method for preparing highly crystallinity stannous niobate single crystals with controllable size, the specific steps of which include: Weigh 1.12g of niobium pentoxide, 2.85g of stannous chloride and 1.67g of potassium chloride (37%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Argon gas is introduced at a flow rate of 300mL / min and the temperature is raised to 400℃ at a heating and cooling rate of 4℃ / min for 2h. The resulting yellow powder is washed with 3M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. The yellow powder is filtered and dried in a vacuum oven at 60℃ for 6h. The powder is then annealed at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0043] Example 5 This embodiment provides a method for preparing highly crystallinity stannous niobate single crystals with controllable size, the specific steps of which include: Weigh 0.83g of niobium pentoxide, 2.85g of stannous chloride and 1.67g of potassium chloride (37%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 300mL / min and heat it to 400℃ at a heating / cooling rate of 4℃ / min for 2h. Wash the resulting yellow powder with 3M hydrochloric acid and dilute it with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6h. Anneal the powder at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0044] Example 6 This embodiment provides a method for preparing highly crystallinity stannous niobate single crystals with controllable size, the specific steps of which include: Weigh 0.34g of niobium pentoxide, 2.85g of stannous chloride, and 1.67g of potassium chloride (37%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 300mL / min and heat the mixture to 400℃ at a heating / cooling rate of 4℃ / min. React for 2h. The resulting yellow powder is washed with 3M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6h. Anneal the powder at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0045] See Figure 1a , Figures 2a-2d The images show electron microscope (EM) images of tin niobate single crystals prepared in Examples 1 and 3-6, respectively. As can be seen from the images, under the same conditions, the particle size of tin niobate single crystals increases with the increase of tin content.

[0046] Example 7 This embodiment provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: Weigh 0.2g of niobium pentoxide, 2.85g of stannous chloride and 1.11g of sodium chloride (28%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 300mL / min and heat it to 400℃ at a heating and cooling rate of 4℃ / min for 2h. Wash the resulting yellow powder with 3M hydrochloric acid and dilute it with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6h. Anneal the powder at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0047] See Figure 3 The image shown is a morphology diagram of the stannous niobate single crystal provided in this embodiment.

[0048] Example 8 This embodiment provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: Weigh 0.2g of niobium pentoxide, 2.85g of stannous chloride, and 1.67g of cesium chloride (37%) and grind them for 30min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 300mL / min and heat the mixture to 400℃ at a heating / cooling rate of 4℃ / min for 2h. Wash the resulting yellow powder with 3M hydrochloric acid and dilute it with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6h. Anneal the powder at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0049] See Figure 4 The image shows the morphology of the stannous niobate single crystal provided in this embodiment; combined with... Figure 1b , Figure 3 and Figure 4 This indicates that halogenated metal salts can all be used to prepare tin niobate single crystals.

[0050] Example 9 This embodiment provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: Weigh 0.2g of niobium pentoxide, 2.85g of stannous chloride and 1.67g of potassium chloride (37%) and grind them for 10min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Argon gas is introduced at a flow rate of 300mL / min and the temperature is raised to 400℃ at a heating and cooling rate of 4℃ / min for 2h. The resulting yellow powder is washed with 3M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. The yellow powder is filtered and dried in a vacuum oven at 60℃ for 6h. The powder is then annealed at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0051] Example 10 This embodiment provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: Weigh 0.2g of niobium pentoxide, 2.85g of stannous chloride and 1.67g of potassium chloride (37%) and grind them for 60min under an inert atmosphere until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 300mL / min and heat the mixture to 400℃ at a heating / cooling rate of 4℃ / min for 2h. Wash the resulting yellow powder with 3M hydrochloric acid and dilute it with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6h. Anneal the powder at 900℃ under an inert atmosphere for 6h to obtain stannous niobate single crystals.

[0052] Example 11 This embodiment provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: Weigh 0.34g of niobium pentoxide, 2.85g of stannous chloride, and 1.67g of potassium chloride. Grind them under an inert atmosphere for 20 minutes to form a homogeneous mixture. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 600ml / min and heat it to 500℃ at a heating / cooling rate of 5℃ / min for 6 hours. Wash the resulting yellow powder with 3M hydrochloric acid and dilute it with a large amount of deionized water to neutralize it. Filter the powder and dry it in a vacuum oven at 60℃ for 6 hours. Anneal the powder at 900℃ for 10 hours under a nitrogen atmosphere.

[0053] See Figure 6 The image shown is the XRD pattern of the stannous niobate single crystal sample provided in this embodiment before annealing, revealing a distinct 600-plane orientation. (See also...) Figure 7 The image shows the XRD pattern of the tin niobate single crystal obtained in this embodiment after annealing. Annealing promotes the growth of other orientations, and the dominant orientation is not obvious. Figure 8 The image shows a SEM image of the tin niobate single crystal sample obtained in this embodiment. As can be seen from the image, the tin niobate single crystals are uniformly distributed and have uniform size.

[0054] Comparative Example 1 This comparative example provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: 1.5 g of niobium pentoxide and 3.2 g of stannous chloride were weighed and ground for 20 min under an inert atmosphere until a homogeneous mixture was formed. The mixture was then transferred to a quartz boat and further transferred to a tube furnace. An argon-hydrogen mixture was introduced at a flow rate of 300 mL / min, and the temperature was increased to 500 °C at a heating / cooling rate of 10 °C / min. The mixture was reacted for 10 h. The resulting yellow powder was washed with 3 M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. The yellow powder was filtered and dried in a vacuum oven at 60 °C for 6 h. The powder was then subjected to subsequent physical property and photoelectrochemical tests.

[0055] See Figure 1c The image shows the morphology of the stannous niobate single crystal provided in this comparative example. The grain size of the single crystal prepared in this comparative example is significantly smaller than that of Example 1 (see [reference]). Figure 1a ) and Example 2 (see Figure 1b ).

[0056] Comparative Example 2 This comparative example provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: 1.5 g of niobium pentoxide and 3.2 g of stannous chloride were weighed and mixed evenly under an inert atmosphere into a quartz boat, and then transferred to a tube furnace. An argon-hydrogen mixture was introduced at a flow rate of 300 mL / min, and the temperature was raised to 500 °C at a heating and cooling rate of 10 °C / min for 10 h. The resulting yellow powder was washed with 3 M hydrochloric acid, diluted with a large amount of deionized water to neutralize it, filtered, and dried in a vacuum oven at 60 °C for 6 h. The powder was then subjected to subsequent physical property and photoelectrochemical tests.

[0057] See Figure 1a , Figure 5a , Figure 5b and Figure 5c The figures show the morphology of stannous niobate single crystals provided in Examples 1, 9, 10 and Comparative Example 2, respectively. The only difference between the four is the grinding time, which is 30 min, 10 min, 60 min and 0 min, respectively. As can be seen from the figures, the particle size of stannous niobate becomes more and more uniform as the grinding time is extended.

[0058] Comparative Example 3 This embodiment provides a method for preparing highly crystalline tin niobate single crystals with controllable size, the specific steps of which include: Weigh 0.34g of niobium pentoxide, 2.85g of stannous chloride, and 1.67g of potassium chloride. Grind them under an inert atmosphere for 20 minutes until a homogeneous mixture is formed. Transfer the mixture to a quartz boat and then to a tube furnace. Introduce argon gas at a flow rate of 600ml / min and heat the mixture to 500℃ at a heating / cooling rate of 5℃ / min. React for 6 hours. The resulting yellow powder is washed with 3M hydrochloric acid and then diluted with a large amount of deionized water to neutralize it. Filter the mixture and dry it in a vacuum oven at 60℃ for 6 hours to obtain stannous niobate powder.

[0059] See Figure 9 The image shows the morphology of the single crystal prepared in this comparative example.

[0060] See Figure 10 The figure shows a comparison of the photocurrent-voltage curves of the comparative example and Example 11. Clearly, the photocurrent response of the unannealed stannous niobate material is significantly lower than that of the annealed stannous niobate single crystal material. Annealing also improves crystallinity, increasing the effective charge transport distance and thus enhancing the photoelectrochemical performance of the stannous niobate single crystal. Another factor contributing to the performance improvement may be the misalignment between the dominant orientation direction and the charge transport direction, which hinders charge transport. This allows the stannous niobate single crystal to still exhibit improved photoelectrochemical performance even when the dominant orientation is not obvious after annealing.

[0061] In addition, the inventors of this case also conducted corresponding experiments using other raw materials and process conditions listed above as alternatives to the various raw materials and corresponding process conditions of the embodiments. The obtained stannous niobate material has high crystallinity and strong photocatalytic activity, and is basically similar to the stannous niobate product prepared in the embodiments.

[0062] The above are merely preferred embodiments of the present invention and do not limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention, achieved through conventional substitutions or by achieving the same function without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.

Claims

1. A method for preparing highly crystalline stannous niobate single crystals with controllable size, comprising mixing stannous chloride, niobium pentoxide and a halide metal salt using a molten salt method, subjecting the resulting mixed salt to a molten salt reaction in an inert gas atmosphere, and annealing to obtain highly crystalline stannous niobate single crystals in the nanometer to micrometer scale.

2. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to claim 1, characterized in that, The halometal salts include Group 7 potassium halogen salts or Group 1 chloride metal salts.

3. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to claim 1, characterized in that, The mass of the added halide metal salt is 0 to 90% of the sum of the masses of the halide metal salt and stannous chloride.

4. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to claim 1, characterized in that, The atomic ratio of tin to niobium is between 0.42 and 20:

1.

5. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to claim 1, characterized in that, The particle size of the highly crystalline tin niobate single crystal is 300 nm to 30 μm.

6. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to claim 1, characterized in that, The conditions for the molten salt reaction include a reaction temperature of 300~600℃, a reaction time of 3~24h, and a heating rate of 1℃ / min~20℃ / min. The inert gas includes argon or nitrogen; The molten salt reaction is carried out in a flowing atmosphere; the flow rate of the flowing atmosphere is 10~600 mL / min.

7. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to claim 1, characterized in that, The annealing includes annealing in an inert gas atmosphere, with an annealing temperature of 700-900℃ / min and an annealing time of 2h-24h.

8. The method for preparing size-controllable highly crystalline stannous niobate single crystals according to any one of claims 1-7, characterized in that, The specific steps include the following: (1) After mixing stannous chloride, niobium pentoxide and halide metal salt, grind them in an inert atmosphere for 10 min to 2 h until they are completely mixed and homogeneous to obtain a mixture; (2) The mixture is transferred to a quartz boat and reacted at 300℃~600℃ for 3h~24h in an inert atmosphere to obtain the reaction product; (3) The reaction product is washed with acid solution until it is neutral, filtered and vacuum dried, and the powder is annealed at 700~900℃ for 2~24h to obtain the highly crystalline tin niobate single crystal.

9. The tin niobate single crystal material prepared by the method for preparing size-controllable highly crystalline tin niobate single crystals according to any one of claims 1-8.

10. The application of the stannous niobate single crystal material according to claim 9 in the fields of photocatalysis and photoelectrocatalysis.

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