Bismuth halide porous thin films, their preparation methods and applications

Abstract

This invention provides a porous bismuth halide film, its preparation method, and its applications. The preparation method includes: contacting a film growth solution containing bismuth and halogen with a trigger gas to perform a gas-liquid interfacial reaction, thereby growing the porous bismuth halide film on the surface of the film growth solution. This invention can improve the thickness uniformity and other properties of the porous bismuth halide film, and can be used to prepare large-area uniform porous bismuth halide films. It also has advantages such as simple preparation process, low cost, and controllable morphology and thickness.

Description

Technical Field

[0001] This invention relates to bismuth halide materials, specifically to a porous bismuth halide thin film, its preparation method, and its application. Background Technology

[0002] Bismuth oxyhalides are a widely used semiconductor material, especially bismuth oxyhalides thin films, which have gradually attracted widespread attention and research. Materials whose scale in one dimension is much smaller than the other two dimensions are called thin films. Compared to bulk materials, thin films have advantages such as light weight, less material usage, and ease of integration. Therefore, traditional dense single-crystal / polycrystalline / amorphous thin films play a crucial role in semiconductor fields such as microelectronics, solar cells, and OLED displays. However, with the continuous development of new energy and other scientific technologies, the demand for thin films is gradually shifting from traditional dense thin films to novel porous thin films. For example, the realization of low-cost, high-efficiency new energy technologies often relies on porous thin films. In electrocatalytic water splitting for hydrogen production, the high specific surface area of ​​porous thin films can provide sufficient reactive sites for carrier-driven solid / liquid interface reactions, thereby achieving efficient electrocatalytic hydrogen production. In photocatalytic degradation of nitrogen oxides, the application of porous thin films greatly increases the gas / solid contact area and enhances gas adsorption on the film surface, thus enabling the rapid degradation of harmful substances such as nitrogen oxides.

[0003] Currently, the main methods for preparing bismuth halides include hydrothermal methods, solvothermal methods, coprecipitation methods, spin coating methods, vapor deposition methods, and electrochemical deposition methods. Among these methods, bismuth halides prepared by hydrothermal methods, solvothermal methods, and coprecipitation methods exist in the form of nano / micron powders. In practical applications, powder materials have many shortcomings. For example, dust pollution occurs during transportation, loading, and discharge, which is not conducive to manual operation; they are prone to sludge accumulation and pipeline blockage during use; and they are not easy to separate from the solution, which can easily cause secondary pollution. These disadvantages seriously limit the application of bismuth halides. While spin coating, vapor deposition, and electrochemical deposition can prepare thin films, they generally suffer from drawbacks such as demanding conditions, cumbersome processes, uneven film thickness, and poor performance. For example, hydrothermal methods require harsh environments such as high temperature and high pressure, and the film area is limited by the volume of the hydrothermal reactor; spin coating is cumbersome and results in uneven film thickness distribution; and electrochemical deposition and chemical vapor deposition require high conductivity of the substrate and are difficult to produce large-area films with uniform thickness.

[0004] Therefore, developing a fabrication process for porous bismuth halide films, simplifying the process flow, and improving the thickness uniformity and other properties of porous bismuth halide films remain urgent technical problems to be solved. Summary of the Invention

[0005] This invention provides a porous bismuth halide film, its preparation method, and its application. It can improve the thickness uniformity and other properties of the porous bismuth halide film, and has the advantages of simple preparation process, effectively overcoming the defects of the prior art.

[0006] In one aspect, the present invention provides a method for preparing a porous bismuth halide film, comprising: contacting a film growth solution containing bismuth and halogen with a trigger gas to perform a gas-liquid interface reaction, and growing the porous bismuth halide film on the surface of the film growth solution.

[0007] Optionally, the trigger gas includes an alkaline gas or an acidic gas; preferably, the alkaline gas includes ammonia, and the acidic gas includes carbon dioxide.

[0008] Optionally, the contact between the thin film growth solution and the trigger gas includes at least one of the following methods 1 and 2: Method 1: placing the thin film growth solution and a non-gas phase trigger in the same container, and releasing the trigger gas through the non-gas phase trigger to contact the thin film growth solution with the trigger gas; Method 2: placing the thin film growth solution in a container and filling the container with the trigger gas to contact the thin film growth solution with the trigger gas.

[0009] Optionally, in Method 1, the non-gas phase trigger includes a solid phase trigger and / or a liquid phase trigger; preferably, the trigger gas includes ammonia, and the non-gas phase trigger includes an ammonia solution and / or an ammonium salt; preferably, the mass fraction of the ammonia solution is 0.01% to 40%, and the ammonium salt includes at least one of ammonium bicarbonate, ammonium carbonate, ammonium chloride, and ammonium nitrate.

[0010] Optionally, the molar concentration of the halogen in the thin film growth solution is 0.0001 mol / L to 10 mol / L; and / or, the molar concentration of the bismuth element in the thin film growth solution is 0.0001 mol / L to 1 mol / L.

[0011] Optionally, the thin film growth solution is prepared by mixing a bismuth-containing compound, a halogen-containing compound, and a solvent, or by mixing a bismuth-containing and halogen-containing compound with a solvent. The bismuth-containing compound includes at least one of bismuth nitrate, bismuth hydroxide, bismuth iodide, bismuth bromide, bismuth oxide, bismuth chloride, bismuth iodate, bismuth iodide oxybismuth, bismuth oxybromide, bismuth oxychloride, and bismuth trifluoromethanesulfonate. The halogen-containing compound includes at least one of metal halides and non-metal halides, and / or the halogen-containing compound includes a monohalogen compound containing one halogen and / or a polyhalogen compound containing at least two halogens. Preferably, the halogen-containing compound includes at least one of sodium iodide, sodium bromide, potassium iodide, potassium bromide, sodium chloride, potassium chloride, and halide hydrides. The bismuth- and halogen-containing compound includes at least one of bismuth iodide, bismuth bromide, bismuth chloride, bismuth iodate, bismuth iodide oxybismuth, bismuth oxybromide, and bismuth oxychloride.

[0012] Optionally, the gas-liquid interface reaction is carried out under acidic conditions; preferably, the pH of the thin film growth solution is 0-4; and / or, the gas-liquid interface reaction is carried out in a container with a pressure of 1×10⁻⁶. -6 ~1×10 8 Pa; and / or, the temperature of the thin film growth solution is 4~90℃.

[0013] In another aspect, the present invention provides a porous bismuth halide film, which is prepared by the above-described method for preparing porous bismuth halide films.

[0014] In another aspect, the present invention provides an application of the bismuth oxyhalide porous film prepared by the above-described method for photocatalysis, electrocatalysis, photoelectrocatalysis, or photoelectric materials.

[0015] In another aspect, the present invention provides a method for preparing a bismuth vanadate photoanode, comprising: preparing a bismuth vanadate porous film according to the above-described method for preparing a bismuth vanadate porous film; and reacting the bismuth vanadate porous film with a vanadium source to prepare a bismuth vanadate photoanode.

[0016] In this invention, a thin film growth solution containing bismuth and halogens is contacted with a trigger gas to carry out a gas-liquid interface reaction, thereby growing a film on the surface of the thin film growth solution to form a porous bismuth halide film. This method has advantages such as simple preparation process, easy operation, and low cost. In particular, it can prepare large-area porous bismuth halide films and improve the thickness uniformity and other properties of porous bismuth halide films. At the same time, the obtained porous bismuth halide films also have good photoelectrocatalytic activity and other properties, and have a wide range of applications, such as photocatalysis, electrocatalysis, photoelectrocatalysis, as well as photoelectric sensors, solar cells, etc. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the sealed container and reaction process used to prepare porous bismuth halide films in an embodiment of the present invention;

[0018] Figure 2 This is a diagram of the first flat-bottomed vessel used in the embodiments of the present invention, and the porous bismuth halide film grown on the surface of the film growth solution;

[0019] Figure 3 This is a sample image of a porous bismuth halide film floating on the surface of the film growth solution after being transferred and removed in an embodiment of the present invention.

[0020] Figure 4 The XRD patterns of S1 to S4 in this embodiment of the invention and the corresponding standard PDF card patterns are shown (the horizontal axis is 2θ angle (°) and the vertical axis is peak intensity (Intensity)).

[0021] Figure 5 The above are the ultraviolet-visible absorption spectra of S1 to S4 in the embodiments of the present invention (the horizontal axis is wavelength).

[0022] Figure 6 These are SEM images of different shooting angles and magnifications in embodiment S3 of the present invention;

[0023] Figure 7 These are SEM images of the liquid phase surfaces S1 to S4 in this embodiment of the invention;

[0024] Figure 8 The TEM image and selected area electron diffraction pattern of S1 in this embodiment of the invention;

[0025] Figure 9 This is an IV curve diagram of the bismuth vanadate photoanode prepared after introducing vanadium source in S1-S4 of the present invention (horizontal axis is voltage (Petential), vertical axis is current density (Current Density)).

[0026] Figure 10 BiOBr is used in the embodiments of the present invention. y I 1-y The yields (Yield) of cyclohexanone and cyclohexanol during the photocatalytic oxidation of cyclohexane to KA oil in solid solution thin films increased with BiOBr. y I 1-y The graph showing the change of y in the graph. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The present invention provides a method for preparing a porous bismuth halide film, comprising: contacting a film growth solution containing bismuth and halogen with a trigger gas to perform a gas-liquid interface reaction, and growing the porous bismuth halide film on the surface of the film growth solution.

[0029] Based on the limiting effect of the gas / liquid interface on the diffusion process, this invention develops a novel process for preparing porous bismuth halide films using gas-liquid interfacial reactions. This process can produce large-area porous bismuth halide films with uniform thickness. The reason for this is that during the film formation process through gas-liquid interfacial reactions, the liquid-phase dissolution of gaseous reactants and the solution diffusion of liquid-phase reactant ions are relatively slow, resulting in porous films. At the same time, even when obtaining large-area porous films, the thickness of the porous films can still be maintained uniformly.

[0030] In the above preparation process, the thin film growth liquid comes into contact with the trigger gas to form a gas-liquid interface. At the same time, the trigger gas triggers the thin film growth liquid to carry out a gas-liquid interface reaction, thereby growing a film on the surface of the thin film growth liquid, thus obtaining a porous bismuth halide thin film.

[0031] Specifically, the trigger gas is used to contact the thin film growth liquid to form a gas-liquid interface and trigger a gas-liquid phase interface reaction in the thin film growth liquid. The trigger gas may include an alkaline gas or an acidic gas. The alkaline gas may include ammonia, and the acidic gas may include carbon dioxide. This is beneficial to improving the preparation efficiency of bismuth halogen oxide porous thin films, as well as the thickness uniformity and photoelectrocatalytic activity of the prepared bismuth halogen oxide porous thin films.

[0032] Specifically, the above-mentioned gas-liquid interfacial reaction is carried out in a container, which can be a closed container, even if the thin film growth solution comes into contact with the trigger gas and a gas-liquid interfacial reaction occurs in the container.

[0033] In some embodiments, such as Figure 1 As shown, the container includes a shell and a top cover that seals the shell. The shell and the top cover form a cavity for carrying out the above-mentioned gas-liquid interfacial reaction. A pressure gauge is provided on the top cover to detect and display the pressure inside the container (i.e., the cavity). The pressure gauge can be located on the side of the top cover away from the cavity.

[0034] In addition, such as Figure 1As shown, the top cover is also provided with a vent pipe that communicates with the cavity. One end of the vent pipe is an air inlet and the other end is an air outlet. The air inlet is used, for example, to fill the cavity with trigger gas, and the air outlet is used, for example, to perform vacuum treatment inside the container before the reaction.

[0035] In some specific embodiments, the pressure inside the container is 1×10⁻⁶. -6 ~1×10 8 Pa, for example 1×10 -6 Pa, 1×10 -5 Pa, 1×10 -4 Pa, 1×10 -3 Pa, 1×10 -2 Pa, 1×10 -1 Pa, 1 Pa, 10 Pa, 1×10 2 Pa, 1×10 3 Pa, 1×10 4 Pa, 1×10 5 Pa, 1×10 6 Pa, 1×10 7 Pa, 1×10 8 Pa or a range consisting of any two of them.

[0036] The gas in the aforementioned container can be almost entirely a trigger gas, or a mixture of trigger gas and other gases, such as air, inert gases (e.g., nitrogen).

[0037] Under normal circumstances, during the above-mentioned gas-liquid interface reaction process, as the reaction time increases, the humidity inside the container (or the deposition humidity of gas-liquid phase deposition) will gradually increase, but it is generally between 30% and 90%.

[0038] In addition, the temperature of the above-mentioned thin film growth solution can be 4~90℃, for example, 4℃, 10℃, 20℃, 25℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or any two of these ranges, but is not limited to this, as long as it can trigger the gas-liquid phase interface reaction.

[0039] In practice, the above preparation process can be carried out at room temperature (the temperature of the thin film growth solution is room temperature), which is conducive to obtaining large-area bismuth oxide porous thin films with uniform thickness and other properties. Compared with conventional thin film preparation technologies such as conventional vapor deposition and electrochemical deposition, it does not require heating, pressurization, electricity or the establishment of specific electrochemical systems, and also has the advantages of simple process, low energy consumption and low cost.

[0040] Furthermore, the contact between the thin film growth solution and the trigger gas can include at least one of the following methods 1 and 2: Method 1: The thin film growth solution and a non-gas phase trigger are placed in the same container, and the trigger gas is released through the non-gas phase trigger to bring the thin film growth solution into contact with the trigger gas (e.g., ...). Figure 1 Method 2: Place the thin film growth solution in a container and fill the container with trigger gas so that the thin film growth solution comes into contact with the trigger gas.

[0041] Specifically, such as Figure 1 As shown, in Method 1, the thin film growth solution and the non-gas phase trigger are placed in different containers. In practice, the container containing the thin film growth solution and the container containing the non-gas phase trigger (or reaction trigger) can be placed in the same container and then left to stand. During the standing process, the trigger gas is released through the non-gas phase trigger. The liquid phase reaction ions in the thin film growth solution come into contact with the trigger gas at the liquid surface of the thin film growth solution (i.e., the gas-liquid interface) and carry out the gas-liquid interface reaction to grow a porous bismuth halide film.

[0042] In practical implementation, the sealed container can be evacuated before the aforementioned gas-liquid interface reaction. For example, after placing a vessel containing the thin film growth solution into the container, the container is evacuated, and then a trigger gas is introduced to carry out the gas-liquid interface reaction. Alternatively, a vessel containing the thin film growth solution and a vessel containing a non-gas-phase trigger can be placed into the container, the container is evacuated, and then the gas-liquid interface reaction is carried out. By evacuating the container, the air in the container is removed, so that the container is almost entirely filled with the trigger gas.

[0043] Optionally, the containers for holding the thin film growth solution and the containers for holding non-gas phase triggers can be flat-bottomed containers.

[0044] Specifically, the non-gas phase trigger is a non-gas phase substance or system that can release the aforementioned trigger gas. It may include solid phase triggers and / or liquid phase triggers (such as solutions, slurries, etc.), as long as it can release the trigger gas to trigger the thin film growth liquid to carry out gas-liquid phase interface reaction.

[0045] In this case, when the non-gas phase triggering material contains both a solid phase triggering material and a liquid phase triggering material, the solid phase triggering material is placed in one container and the liquid phase triggering material is placed in another container, i.e., the two are placed in different containers. Then, they are placed in the same container as the thin film growth solution. The gas phase triggering material releases triggering gas, and at the same time, the solid phase triggering material also releases triggering gas. The thin film growth solution comes into contact with the triggering gases released by the two, and a gas-liquid interface reaction occurs.

[0046] In some preferred embodiments, in method 1, the trigger gas includes ammonia, and the non-gaseous trigger can be a liquid-phase system or a solid-phase system capable of releasing ammonia. Preferably, the non-gaseous trigger includes an aqueous ammonia solution and / or an ammonium salt. The ammonium salt includes at least one of ammonium bicarbonate, ammonium carbonate, ammonium halide, and ammonium nitrate, and the ammonium halide includes ammonium chloride, for example.

[0047] For example, when the non-gas phase trigger is an ammonia solution, ammonia can be released through the ammonia solution at room temperature; when the non-gas phase trigger is an ammonium salt, ammonia is released through the ammonium salt. In specific implementation, the ammonium salt can be appropriately heated to facilitate the release of ammonia. For example, if the non-gas phase trigger is ammonium bicarbonate, it can be heated to 58°C or above, causing the ammonium bicarbonate to decompose and release ammonia, which then comes into contact with the thin film growth solution and triggers the gas-liquid interface reaction of the thin film growth solution.

[0048] Preferably, the mass fraction of the ammonia solution can be from 0.01% to 40%, for example, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any combination thereof. Relatively speaking, controlling the concentration of the ammonia solution within the above range is more beneficial to the uniformity of the thickness and other properties of the prepared bismuth halide porous film. Studies show that as the mass fraction (concentration) of the ammonia solution decreases, the thickness of the obtained bismuth halide porous film gradually increases. In specific implementations, the concentration of the ammonia solution used can be adjusted as needed.

[0049] The aforementioned ammonia solution is an aqueous solution of ammonia, which can be commercially available or prepared in-house. Specifically, it can be prepared using conventional methods in the art, such as diluting concentrated ammonia with water. The mass fraction of the diluted ammonia solution is adjusted by the mixing ratio of concentrated ammonia to water. For example, water and concentrated ammonia are mixed and stirred until homogeneous, for example, by magnetic stirring, to obtain an ammonia solution (or diluted ammonia solution). This ammonia solution is used as the aforementioned non-gas phase trigger.

[0050] In some embodiments, the trigger gas includes an acidic gas. The process of contacting the thin film growth solution with the trigger gas (i.e., the process of triggering a gas-liquid interface reaction in the thin film growth solution) may include: placing the vessel containing the thin film growth solution in a container, filling it with carbon dioxide, for example, to the point that its dissolution in the thin film growth solution reaches saturation, and then releasing the acidic gas (i.e., releasing the acidic gas from the container). Generally, the release can be slow. During this process, the carbon dioxide pressure in the container decreases, its dissolution in the thin film growth solution decreases, and the carbon dioxide escapes from the thin film growth solution, causing the pH of the thin film growth solution to rise and triggering thin film growth.

[0051] In the aforementioned thin film growth solution, bismuth exists in ionic form, specifically as Bi0.05. 3+ Halogens can exist in the form of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), which also exist in ionic form.

[0052] Specifically, in the above-mentioned thin film growth solution, the molar concentration c1 of halogen can be from 0.0001 mol / L to 10 mol / L, for example, 0.0001 mol / L, 0.0005 mol / L, 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 7 mol / L, 10 mol / L, or any two of these ranges.

[0053] Studies show that in the aforementioned film growth solution, the thickness of the prepared bismuth halide porous film decreases with decreasing bismuth concentration, while the sheet packing density decreases with increasing bismuth concentration. In practice, the bismuth concentration in the film growth solution can be adjusted as needed to regulate parameters such as the thickness and sheet packing density of the bismuth halide porous film.

[0054] In some preferred embodiments, the molar concentration c2 of bismuth in the above-mentioned thin film growth solution can be from 0.0001 mol / L to 1 mol / L, for example, 0.0001 mol / L, 0.0005 mol / L, 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, or any two of these ranges. Relatively speaking, controlling the concentration of bismuth within the above range is more beneficial to the preparation efficiency and performance of porous bismuth halide films.

[0055] Generally, the above-mentioned thin film growth solution is a solution, and its solvent can be water (i.e., the thin film growth solution is an aqueous solution containing bismuth and halogen), or a mixture of water and organic solvent. The organic solvent used can be miscible with water, such as alcohol solvents, such as methanol, ethanol, propanol, etc., but is not limited to these, and can also be other organic solvents that are miscible with water.

[0056] The water used may include at least one of deionized water, reverse osmosis water, and ultrapure water.

[0057] In specific implementations, the aforementioned thin film growth solution can be prepared by mixing a bismuth-containing compound, a halogen-containing compound, and a solvent. For example, it can be prepared by mixing a solution of a bismuth-containing compound with a halogen-containing compound, or by mixing a solution of a bismuth-containing compound with a halogen-containing compound, or by mixing a mixture containing a bismuth-containing compound and a halogen-containing compound with a solvent. Exemplarily, the preparation process of the aforementioned bismuth-containing compound solution may include: mixing the bismuth-containing compound with water, stirring until partially dissolved, and then ultrasonically dispersing it uniformly to obtain an aqueous solution of the bismuth-containing compound.

[0058] Alternatively, the aforementioned thin film growth solution can be prepared by mixing a bismuth- and halogen-containing compound with a solvent, that is, by dissolving a bismuth- and halogen-containing compound in a solvent to prepare a thin film growth solution.

[0059] In practice, during the preparation of the thin film growth solution, after mixing the bismuth-containing compound solution with the halogen-containing compound solution, or after mixing the bismuth-containing compound solution with the halogen-containing compound solution, or after mixing the mixture containing the bismuth-containing compound and the halogen-containing compound with the solvent, or after mixing the bismuth-containing and halogen-containing compound with the solvent, the system can be uniformly dispersed by means of ultrasound and / or stirring.

[0060] Accordingly, the amount of bismuth-containing compound, halogen-containing compound, or compound containing both bismuth and halogen is such that the molar concentration of bismuth in the thin film growth solution is c2 and the molar concentration of halogen is c1. For example, the thin film growth solution is prepared by mixing an aqueous solution of a bismuth-containing compound with a halogen-containing compound. In the aqueous solution of the bismuth-containing compound, the molar concentration of bismuth is c2. Adding the halogen-containing compound does not substantially affect the molar concentration of bismuth, meaning the molar concentration of bismuth in the prepared thin film growth solution remains essentially c2. Simultaneously, the amount of halogen-containing compound added satisfies the molar concentration of halogen being c1.

[0061] Optionally, the above-mentioned bismuth- and halogen-containing compounds may include monohalogen compounds containing one halogen and / or polyhalogen compounds containing at least two halogens, specifically including at least one of bismuth halides and bismuth oxyhalides, such as at least one of bismuth iodide, bismuth bromide, bismuth chloride, bismuth iodate, bismuth oxyiodide, bismuth oxybromide, and bismuth oxychloride.

[0062] Optionally, the aforementioned bismuth-containing compounds may include at least one of the following: bismuth-containing salts, bismuth-containing hydroxides, bismuth-containing halides, bismuth-containing halide oxides, and bismuth-containing oxides, such as at least one of bismuth nitrate, bismuth hydroxide, bismuth iodide, bismuth bromide, bismuth oxide, bismuth chloride, bismuth iodate, bismuth iodide oxybismuth, bismuth oxybromide, bismuth oxychloride, and bismuth trihalomethanesulfonate (such as bismuth trifluoromethanesulfonate).

[0063] Optionally, the aforementioned halogen-containing compounds may include at least one of metal halides and non-metal halides, and the halogen-containing compounds may include monohalogen compounds containing one halogen and / or polyhalogen compounds containing at least two halogens. Non-metal halides may include halogen hydrides, and metal halides may include halogen-containing salts, such as water-soluble salts including potassium salts and / or sodium salts containing halogens, such as at least one of sodium iodide, sodium bromide, potassium iodide, potassium bromide, sodium chloride, and potassium chloride.

[0064] In some specific embodiments, the halogenated compound is sodium iodide. When the bismuth-containing compound, the halogenated compound and the solvent are mixed to prepare the thin film growth solution, the molar ratio of bismuth to iodine is 0.5~2.0:1.0~10.0, for example (0.5~2.0):2.

[0065] Specifically, the above-mentioned gas-liquid interface reaction can be carried out under acidic conditions, that is, the film growth solution is acidic. Acidic conditions can inhibit the hydrolysis of bismuth ions and further improve the uniformity and other properties of the prepared bismuth halide film.

[0066] In some preferred embodiments, the pH of the thin film growth solution can be 0 to 4, for example, a range of 0, 1, 2, 3, 4 or any two of these.

[0067] The pH of the system can be adjusted using inorganic acids and / or organic acids, such as at least one of nitric acid, sulfuric acid, hydroiodic acid, trifluoromethanesulfonic acid, hydrochloric acid, acetic acid, etc. Specifically, the pH of the system can be adjusted using an acidic solution containing inorganic acids and / or organic acids (such as an aqueous solution of inorganic acids and / or organic acids), such as concentrated nitric acid with a mass concentration of about 68%.

[0068] In practice, after mixing bismuth-containing compounds and halogen-containing compounds with solvents, or after mixing compounds containing both bismuth and halogens with solvents, the system can be mixed evenly by stirring, sonication, etc. Then, an acidic solution is added dropwise to the resulting mixture to adjust the mixture to acidity, for example, to a pH of 0-4, so that the bismuth-containing compounds and other raw materials can dissolve and form a thin film growth solution. The thin film growth solution is then brought into contact with a trigger gas to carry out a gas-liquid interface reaction.

[0069] Studies show that controlling the pH of the thin film growth solution to 0-4 is more conducive to the gas-liquid interface reaction between the growth solution and the trigger gas, resulting in a uniformly thick bismuth halide film. The reason is speculated to be that the trigger gas can modulate the pH value of the growth solution surface, thereby triggering film growth. Taking a growth solution pH of 1 as an example, when the trigger gas is alkaline, the alkaline gas contacts the growth solution, raising the pH value of the growth solution surface, for example, potentially raising it to approximately 1.5-2.5 to trigger film growth. When the trigger gas is acidic, the acidic gas is first introduced into the container, dissolves in the growth solution, and then is released. During the release of the acidic gas, it escapes from the growth solution, thereby raising the pH value of the growth solution surface, for example, potentially raising it to approximately 1.5-2.5 to trigger film growth.

[0070] Unless otherwise specified, all raw materials and reagents used in this invention can be commercially available products or prepared by conventional methods in the field. They can be purchased or made in-house, and there are no special restrictions on their use.

[0071] In addition, the reaction time of the gas-liquid interface can generally be 10 min to 90 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min or any combination thereof.

[0072] In practice, after the film growth is completed (i.e., after the gas-liquid interface reaction is completed), the film floating on the surface of the film growth liquid can be transferred and removed from the film growth liquid. For example, a solid substrate can be inserted into the film growth liquid from the edge of the container containing the film growth liquid, and the solid substrate can be tilted and rotated so that it is pulled out of the film growth liquid at an angle slightly parallel to the liquid surface of the film growth liquid, thereby transferring the film floating on the surface of the film growth liquid to the solid substrate and removing it from the film growth liquid.

[0073] In addition, after the film is removed from the film growth solution, it can be dried, for example at room temperature, to obtain a porous bismuth halide film.

[0074] In the above preparation process, the film area is basically limited only by the surface area of ​​the film growth solution. In practice, a larger container can be used to hold the film growth solution to increase its surface area, thereby obtaining a large-area (e.g., a diameter of 9-15 cm, 10-15 cm, or more than 15 cm) porous bismuth halide film. The obtained porous bismuth halide film has a uniform thickness, and even after increasing the area of ​​the obtained porous bismuth halide film, it can still maintain good thickness uniformity and other properties. Its thickness is generally in the nanometer to micrometer range, specifically in the range of 100 nm to 100 nm. With a diameter in the µm range, this porous bismuth oxide halide film can be transferred to the surface of most materials (such as metals, glass, and polymers) and exhibits excellent photoelectric activity and other properties. It has a wide range of applications, including photocatalysis (such as photocatalytic degradation of organic pollutants, photocatalytic synthesis of high-value-added chemical products (such as KA oil (cyclohexanone, cyclohexanol), NH3, etc.), electrocatalysis (such as electrocatalytic degradation of organic pollutants, electrocatalytic synthesis of high-value-added chemical products, electrocatalytic water splitting for hydrogen production), photoelectrocatalysis (such as photoelectrocatalytic degradation of organic pollutants, photocatalytic synthesis of high-value-added chemical products, photoelectrocatalytic hydrogen production / generation electrodes), as well as photoelectric sensors, solar cells, and the introduction of vanadium sources to create bismuth vanadate photoanodes.

[0075] The present invention also provides a porous bismuth halide film, which is prepared by the above-described method for preparing porous bismuth halide films and has the advantages described above.

[0076] Specifically, the porous bismuth halide film is formed from bismuth halide, the molecular formula of which is BiOX, where X is a halogen, which can be one or more of F, Cl, Br, and I. That is, bismuth halide can contain only one halogen or contain at least two halogens. When the bismuth halide in the porous bismuth halide film contains at least two halogens, it is generally a solid solution film.

[0077] For example, bismuth oxyhalides contain two halogens, and their molecular formula can be represented as BiOX. 1 y X 2 1-y (i.e., X is made up of X) 1 and X 2 Composition), 0 < y < 1, where y is, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. For example, X 1 For Br, X 2 For I, i.e., BiOX 1 y X 2 1-y For BiOBr y I 1-y .

[0078] In the preparation of bismuth oxyhalides, one can choose a compound containing one halogen to form a porous bismuth oxyhalide film containing one halogen, or choose a compound containing different halogens, or a combination of multiple compounds, to form a bismuth oxyhalide containing at least two different halogens (such as BiOX). 1 y X 2 1-y ) porous film.

[0079] Studies show that the aforementioned bismuth halide has a PbFCl-type crystal structure, consisting of a layered structure with [X-Bi-O-Bi-X] as the basic unit, stacked along the

[001] direction by weak van der Waals forces between halogen atoms, with a positively charged bismuth oxide layer [Bi2O2]. 2+ and the negatively charged halide ion layer (X - The internal electric field induced in the

[001] direction can effectively promote the separation of photogenerated carriers, endowing bismuth oxyhalide with excellent catalytic activity, making it a novel optoelectronic material with visible light responsiveness, which can be widely used in photocatalysis, electrocatalysis, photoelectrocatalysis, as well as optoelectronic sensors, solar cells and other fields.

[0080] In addition, the porous bismuth halide film has a uniform thickness, typically ranging from nanometers to micrometers, for example, from one hundred nanometers to tens of micrometers.

[0081] Furthermore, the porous bismuth halide film exhibits a porous structure. Studies show that the vapor phase surface of the porous bismuth halide film (which is also the side closer to the trigger gas when it floats in the film growth liquid) is usually more dense, forming smaller pores, while its liquid phase surface (which is also the side closer to the film growth liquid when it floats in the film growth liquid) is loose and porous. That is, the vapor phase surface and the liquid phase surface of the porous bismuth halide film are opposite sides of the bismuth halide film, and the density of the vapor phase surface is greater than that of the liquid phase surface, and the pore size of the vapor phase surface is smaller than that of the liquid phase surface.

[0082] Specifically, in the direction perpendicular to the thickness of the bismuth oxyhalide porous film, the bismuth oxyhalide porous film has a layered structure arranged in sequence, that is, it presents a relatively neatly arranged sheet-like structure. The pores (or intermediate pores) between these layered structures are connected from top to bottom (that is, they penetrate the porous film along the thickness direction of the porous film), forming smaller pores on the gas phase surface of the film and larger pores on the liquid phase surface of the film.

[0083] In addition, the above-mentioned porous bismuth halide films also have the characteristics of high crystallinity. They are generally composed of stacked two-dimensional bismuth halide sheets with grain boundaries between the sheets and different crystal orientations, so the whole structure is polycrystalline. However, each single sheet usually has a long-range ordered periodic atomic arrangement structure, exhibiting single-crystal characteristics.

[0084] For example, the bismuth halide in the above-mentioned porous bismuth halide film is bismuth iodide, which has a polycrystalline structure and the monolayers therein exhibit monocrystalline characteristics.

[0085] The present invention also provides an application of the above-mentioned bismuth oxide porous thin film in photocatalysis, electrocatalysis, photoelectrocatalysis or photoelectric materials.

[0086] As described above, the porous bismuth halogen oxide film prepared by the present invention has good photoelectric activity and catalytic activity, and can be applied to photocatalysis, electrocatalysis or photoelectrocatalysis, for example, for photocatalytic degradation, electrocatalytic degradation, photoelectrocatalytic degradation of organic pollutants, as well as photocatalytic synthesis, electrocatalytic synthesis, photoelectrocatalytic synthesis of high value-added chemical products, electrocatalytic water splitting to produce hydrogen, photoelectrocatalytic hydrogen production / generation electrode, and the preparation of bismuth vanadate photoanodes after introducing vanadium sources.

[0087] For example, the aforementioned porous bismuth halide film can be used for photocatalytic oxidation of cyclohexane to generate KA oil, specifically, the cyclohexane oxidation can be catalytically performed under visible light. In some specific embodiments, the process of catalytically oxidizing cyclohexane to generate KA oil may include: immersing the bismuth halide film in a solution containing cyclohexane, and then reacting it under visible light for 4-6 hours, such as 5 hours. During the reaction, the system temperature can be maintained at 5-10°C (e.g., 7°C) to avoid the volatilization of generated alcohols, ketones, and other products, while maintaining a high reaction efficiency. The solution containing cyclohexane may include, for example, a mixed solution of cyclohexane and carbon tetrachloride, with a volume ratio of cyclohexane to carbon tetrachloride of, for example, 10:(12-18) (e.g., 10:15), but is not limited to this.

[0088] For example, a bismuth vanadate photoanode made of the aforementioned porous bismuth halide film was used as the working electrode in a three-electrode (working electrode, counter electrode, reference electrode) system. Under visible light / sunlight illumination, the voltage-current relationship curve was measured. The results showed that a high photocurrent could be achieved at a relatively low voltage (e.g., a photocurrent of 4.2 mA / cm² at 1.23 V (V vs. RHE)). 2 It exhibits excellent photoelectric properties.

[0089] In one specific embodiment of the present invention, a method for preparing a bismuth vanadate photoanode is provided, comprising: preparing a bismuth vanadate porous film according to the above-described method for preparing a bismuth vanadate porous film; reacting the bismuth vanadate porous film with a vanadium source to obtain a bismuth vanadate (BiVO4) photoanode.

[0090] Specifically, a vanadium source is used to provide vanadium. Vanadium is introduced into the bismuth halide porous film by reacting the vanadium source with the bismuth halide porous film, thus forming a BiVO4 photoanode. Exemplarily, the vanadium source may include vanadium acetylacetonate (VO(acac)2), but is not limited thereto.

[0091] Specifically, the porous bismuth halide film can be contacted with a vanadium source solution containing a vanadium source, for example, by drop casting the vanadium source solution onto the porous bismuth halide film to allow the porous bismuth halide film to react with the vanadium source. The vanadium source solvent can be formed by mixing the vanadium source with a solvent, that is, by dissolving the vanadium source in a solvent to form a vanadium source solution. The solvent used can specifically include organic solvents, and further can include polar solvents, such as dimethyl sulfoxide (DMSO).

[0092] For example, the concentration of the vanadium source solution can be 0.1~0.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc., but is not limited to this.

[0093] In addition, the reaction temperature of the bismuth halide porous film with the vanadium source can be 400~500℃, such as 400℃, 420℃, 450℃, 480℃, 500℃, etc.

[0094] In some specific embodiments, the reaction process of the bismuth halide porous film reacting with the vanadium source may include: placing the vanadium source solution on the bismuth halide porous film, transferring the porous film to a heating device preheated to a preset temperature, and then heating it to the reaction temperature (400~500℃) at a heating rate of 1-5℃ / min, and holding the reaction at the reaction temperature for a time of, for example, 1.5~3h, such as 2h.

[0095] The preheating temperature can be 100-150℃, such as 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc.; the heating rate can be, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, etc.; and the heating equipment used can be, for example, a muffle furnace, etc.

[0096] After the reaction is complete, the crude product can be treated with an alkaline solution. For example, the crude product can be immersed in an alkaline solution and stirred for 10-50 minutes (e.g., about 30 minutes) to remove excess V2O5 and other substances from its surface. Then, it can be washed with water and alcohol solvents and dried, for example, in the air, to obtain the BiVO4 photoanode.

[0097] The alkaline solution used may include an aqueous solution of an alkali metal hydroxide, such as sodium hydroxide (NaOH) solution, and the alcohol solvent used may include ethanol.

[0098] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all 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.

[0099] Example 1

[0100] (1) Add water to bismuth nitrate, and disperse bismuth nitrate evenly in water by stirring and sonication to obtain an aqueous solution of bismuth nitrate with a concentration of 0.1 mol / L; add sodium iodide to the aqueous solution of bismuth nitrate, and stir continuously for 20 min to obtain a mixed solution. The amount of sodium iodide added satisfies that the molar concentration of sodium iodide in the mixed solution is 0.4 mol / L.

[0101] (2) While maintaining stirring, add concentrated nitric acid with a mass concentration of 68% dropwise to the second mixed solution to adjust the pH value to 4.0, and obtain the film growth solution; place the film growth solution in the first flat-bottomed container;

[0102] (3) Under magnetic stirring, add deionized water to the concentrated ammonia solution to dilute it and prepare an ammonia solution with a mass fraction of 25%. Place the ammonia solution in a second flat-bottomed container.

[0103] (4) Place the first flat-bottomed vessel containing the thin film growth solution and the second flat-bottomed vessel containing the ammonia solution into a 20L sealed drying container. After standing for 30 minutes, open the drying container to obtain a fully grown thin film (the thin film covers the surface of the thin film growth solution). The deposition humidity of the gas-liquid phase deposition is 30-90%.

[0104] (5) Insert the solid substrate into the film growth solution from the edge of the flat-bottomed vessel containing the film growth solution. Tilt the solid substrate and remove it from the solution at an angle slightly parallel to the liquid surface. Transfer the film floating on the surface of the film growth solution to the solid substrate and remove it. After drying, rinse it several times with deionized water. After drying the rinsed sample, a bismuth halide porous film (red in color) is obtained and named S1; where, as Figure 2 and Figure 3 As shown, the first flat-bottomed vessel containing the film growth solution is circular with a diameter of 102.99 mm, and the diameter of the resulting bismuth halide porous film S1 is 90.30 mm.

[0105] Example 2: The difference from Example 1 is that in step (1), the concentration of the bismuth nitrate aqueous solution is 0.2 mol / L, and the other conditions are the same as in Example 1. The bismuth oxyhalide porous film is named S2.

[0106] Example 3: The difference from Example 1 is that in step (1), the concentration of the bismuth nitrate aqueous solution is 0.3 mol / L, and the other conditions are the same as in Example 1. The bismuth oxyhalide porous film is named S3.

[0107] Example 4: The difference from Example 1 is that in step (1), the concentration of the bismuth nitrate aqueous solution is 0.4 mol / L, and the other conditions are the same as in Example 1. The bismuth oxyhalide porous film is named S4.

[0108] Test example

[0109] 1. X-ray diffraction (XRD) analysis was performed on S1~S4 respectively, and the results are shown in the figure. Figure 4 (Among them, Bi) 3+ :I - The spectrum corresponding to =0.5:2.0 is the spectrum of S1; Bi 3+ :I - The spectrum corresponding to =1.0:2.0 is the spectrum of S2; Bi 3+ :I - The spectrum corresponding to =1.5:2.0 is the spectrum of S3, Bi 3+ :I - =2.0:2.0 corresponds to the spectrum of S4; PDF#10-0445 BiOI is the standard PDF card of bismuth oxyiodide (BiOI), that is, its corresponding spectrum is the standard spectrum of BiOI. It can be seen that S1~S4 are pure phase bismuth oxyiodide. Changing the concentration of bismuth ions in the film growth solution does not shift the position of the diffraction peak.

[0110] 2. The UV-Vis absorption spectra of S1~S4 were measured respectively, and the results are shown in the figure. Figure 5 (Among them, Bi) 3+ :I - The curve corresponding to =0.5:2.0 is the spectrum of S1, Bi 3+ :I - The curve corresponding to =1.0:2.0 is the spectrum of S2; Bi 3+ :I - The curve corresponding to =1.5:2.0 is the spectrum of S3, Bi 3+ :I - =2.0:2.0 corresponds to the spectrum of S4. It can be seen that as the concentration of bismuth ions in the film growth solution increases, the light absorption intensity of the prepared sample (i.e., bismuth halide porous film) gradually increases. This trend is observed in both the ultraviolet and visible light ranges. At the same time, as the concentration of bismuth ions in the film growth solution increases, the absorption edge of the sample gradually shifts from short wavelength to long wavelength.

[0111] 3. Scanning electron microscopy (SEM) analysis was performed on S1 to S4 respectively. The SEM image of S3 is shown below. Figure 6 (The measurement results of S1, S2, and S4 are similar to those of S3), among which, Figure 6 a) is a microscopic morphology diagram of the gas phase surface of S3. Figure 6 b) is a microscopic morphology diagram of the S3 liquid phase surface. Figure 6 c) and d) are cross-sectional views of S3 at different magnifications. It can be seen that the gas phase surface of S3 is dense with small pores, while its liquid phase surface is loose and porous. At the same time, the cross-sectional views show that S3 exhibits a neat and orderly layered structure with the central pores running from top to bottom.

[0112] SEM images of the liquidus surfaces of S1 to S4 are shown below. Figure 7 Among them, Bi 3+ :I - The graph corresponding to 0.5:2.0 is the SEM image of the liquidus surface of S1; Bi 3+ :I - The graph corresponding to =1.0:2.0 is the SEM image of the liquidus surface of S2; Bi 3+ :I - The graph corresponding to 1.5:2.0 is the SEM image of the liquidus surface of S3; Bi 3+ :I - =2.0:2.0 The corresponding figure is the SEM image of the liquid phase surface of S4. It can be seen that as the concentration of bismuth ions in the thin film growth solution increases, the sheet packing density of the thin film sample decreases.

[0113] In addition, the thickness of S1~S4 is uniform. The thickness of S1~S4 was tested by a profilometer, and the results are shown in Table 1 (six different positions of the film were randomly tested to obtain six test values; and the average value of the six test values ​​was calculated). It can be seen that as the concentration of bismuth ions in the film growth solution increases, the thickness of the prepared bismuth iodide porous film gradually increases. It is evident that the increase in reactant concentration leads to the generation of more reaction products.

[0114] Table 1. Thickness Measurement Results of S1~S4

[0115] 4. Transmission electron microscopy (TEM) analysis was performed on S1 to S4 respectively. The TEM image and selected area electron diffraction pattern of S1 are shown below. Figure 8 (The measurement results of S2, S3, and S4 are similar to those of S1); it can be seen that the high-resolution TEM image of the porous bismuth oxyiodide film prepared through the above examples ( Figure 8 a) reveals the high crystallinity of the nanosheets, with clear lattice fringes of 0.282 nm interplanar spacing corresponding to the (110) atomic plane. Figure 8 The selected area electron diffraction (SAED) pattern of b) shows that the monolayer of S1 has single-crystal characteristics, and the angle marked in the SAED pattern is 45°, which is consistent with the theoretical value of the angle between the (110) and (200) crystal planes of bismuth oxyiodide, further indicating that the prepared thin film S1 is highly crystalline bismuth oxyiodide.

[0116] 5. After introducing S1-S4 (BiOI porous thin films) into the vanadium source, bismuth vanadate photoanodes are fabricated. The specific operation steps are as follows:

[0117] Vanadium oxyacetylacetonate (VO(acac)2) was dissolved in DMSO to prepare a vanadium source solution with a concentration of 0.2 mol / L.

[0118] 70 μL of vanadium source solution was drop-cast onto a BiOI porous film, and then the BiOI porous film was transferred to a muffle furnace preheated to 120 °C. The temperature of the muffle furnace was increased to 450 °C at a heating rate of 2 °C / min, and then held at that temperature for 2 h.

[0119] Subsequently, after the muffle furnace was naturally cooled to room temperature, the obtained BiVO4 sample was immersed in a 1 mol / L NaOH solution and gently stirred for 30 min to remove excess V2O5 from the surface of BiVO4.

[0120] Finally, the BiVO4 sample was washed with deionized water and ethanol and dried in air to obtain the BiVO4 photoanode.

[0121] In the three-electrode system, Ag / AgCl was used as the reference electrode, a Pt sheet as the counter electrode, bismuth vanadate photoanode as the working electrode, a mixed solution of K₂HPO₄, KH₂PO₄, and Na₂SO₃ as the electrolyte, and an AM 1.5G solar simulator as the light source. The current-voltage relationship curve (IV curve) of the bismuth vanadate photoanode was detected, and the results are shown in [Figure number missing]. Figure 9 As can be seen, bismuth vanadate photoanodes fabricated by introducing S1-S4 into the vanadium source can achieve high current densities even at lower voltages. In particular, bismuth vanadate photoanodes fabricated using S2 and S3 can achieve even better current densities; for example, at 1.23 V (V vs. RHE), the photocurrent can reach 4.2 mA / cm². 2 The left and right sides exhibit good photoelectric properties.

[0122] 6. Photocatalysis test

[0123] Referring to the preparation process of S1 in Example 1, sodium bromide was used to replace sodium iodide to prepare a porous bismuth oxybromine film S5;

[0124] Referring to the preparation process of S1 in Example 1, different BiOBr were prepared by replacing sodium iodide with mixed halide salts of sodium bromide and sodium iodide in different proportions. y I 1-y Porous thin films (solid solution thin films), these BiOBr y I 1-y The y values ​​in the solid solution films were 0, 0.2, 0.4, 0.6, 0.8, and 1.0 (y=0, no halide salt was added); bismuth oxyiodide porous films S1 and S5, as well as BiOBr with the above different x values, were used respectively. y I 1-y Solid solution thin films were subjected to the following photocatalytic experiments:

[0125] Take a 3cm x 3cm BiOBr y I 1-y A solid solution film was fixed on a support and placed in a reactor; a mixed solution of 10 mL cyclohexane and 15 mL carbon tetrachloride was injected into the test reactor as a reaction solution, and BiOBr... y I 1-y The solid solution film is completely immersed in the reaction solution; the reactor is sealed, evacuated and then oxygen is injected to the ambient pressure; a 300 W xenon lamp is used as the light source, and a 420 nm filter is used to obtain the illumination conditions in the visible light region. The reaction is carried out under these illumination conditions for 5 hours. During the reaction, the temperature of the reaction system is maintained at about 7°C by circulating water to avoid the volatilization of the generated alcohol and ketone products.

[0126] After the reaction was completed, the obtained KA oil product was quantitatively analyzed. The results showed that using S1, S5, and BiOBr with different y values... y I 1-y Solid solution films can yield high yields of cyclohexanone and cyclohexanol, with BiOBr being particularly effective. y I 1-y When solid solution thin films are used, such as Figure 10 As shown, the yield of cyclohexanol increases with the increase of y, while the yield of cyclohexanone shows a trend of first increasing and then decreasing. When x=0.8, the yield of cyclohexanone reaches the maximum, producing 5.5 µmol of cyclohexanol and 22.9 µmol of cyclohexanone. The yield of KA oil is 5.5 times that of S1 and 2.5 times that of S5, indicating that the bismuth oxide halide solid solution has a stronger photocatalytic cyclohexane oxidation ability.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a porous bismuth halide thin film, characterized in that, include: A thin film growth solution containing bismuth and halogens is contacted with a trigger gas to perform a gas-liquid interface reaction, thereby growing the bismuth oxide porous thin film on the surface of the thin film growth solution. The thin film growth solution is prepared by mixing a bismuth-containing compound, a halogen-containing compound, and a solvent. The bismuth-containing compound includes at least one of bismuth nitrate, bismuth hydroxide, bismuth iodide, bismuth bromide, bismuth oxide, bismuth chloride, bismuth iodate, and bismuth trifluoromethanesulfonate. The trigger gas includes an alkaline gas or an acidic gas; the alkaline gas includes ammonia, and the acidic gas includes carbon dioxide. The gas-liquid interface reaction is carried out under acidic conditions, and the pH of the thin film growth solution is 0~4; The contact between the thin film growth solution and the trigger gas includes at least one of the following methods 1 and 2: Method 1: Place the vessel containing the thin film growth solution and the vessel containing the non-gas phase trigger in a sealed container. After evacuating the sealed container, release the trigger gas through the non-gas phase trigger so that the thin film growth solution comes into contact with the trigger gas. Method 2: Place the thin film growth solution in a container and fill the container with the trigger gas so that the thin film growth solution comes into contact with the trigger gas.

2. The method for preparing porous bismuth halide films according to claim 1, characterized in that, In Method 1, the non-gas phase trigger includes a solid phase trigger and / or a liquid phase trigger; The non-gas phase trigger includes aqueous ammonia solution and / or ammonium salt; The ammonia solution has a mass fraction of 0.01% to 40%, and the ammonium salt includes at least one of ammonium bicarbonate, ammonium carbonate, ammonium chloride, and ammonium nitrate.

3. The method for preparing porous bismuth halide films according to claim 1, characterized in that, In the thin film growth solution, the molar concentration of the halogen is 0.0001 mol / L to 10 mol / L; and / or, in the thin film growth solution, the molar concentration of the bismuth element is 0.0001 mol / L to 1 mol / L.

4. The method for preparing porous bismuth halide films according to claim 1, characterized in that, The halogen-containing compound includes at least one of metal halides and non-metal halides, and / or, the halogen-containing compound includes a monohalogen compound containing one halogen and / or a polyhalogen compound containing at least two halogens; the halogen-containing compound includes at least one of sodium iodide, sodium bromide, potassium iodide, potassium bromide, sodium chloride, potassium chloride, and halogen hydrides.

5. The method for preparing porous bismuth halide films according to claim 1, characterized in that, The gas-liquid interfacial reaction takes place in a container at a pressure of 1 × 10⁻⁶. -6 ~1×10 8 Pa; And / or, the temperature of the thin film growth solution is 4~90℃.

6. A porous bismuth halide thin film, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The application of the porous bismuth halide thin film prepared by the preparation method according to any one of claims 1-5 in photocatalysis, electrocatalysis, photoelectrocatalysis or photoelectric materials.

8. A method for preparing a bismuth vanadate photoanode, characterized in that, include: According to the method for preparing a porous bismuth halide film according to any one of claims 1-5, a porous bismuth halide film is prepared; the porous bismuth halide film is reacted with a vanadium source to prepare a bismuth vanadate photoanode.

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