Porous bismuth pentaiodide semiconductor photocatalyst, method of preparation and use thereof

Abstract

This invention belongs to the field of photocatalyst preparation technology, and discloses a porous Bi5O7I semiconductor photocatalyst, its preparation method, and its application. The method involves dissolving a Bi-containing polymer in distilled water, adding an I-containing inorganic salt, stirring until homogeneous, and then transferring the solution to an autoclave for hydrothermal treatment. The hydrothermal reaction product is centrifuged and dried to obtain a powder, which is then ground and calcined at high temperature to obtain the porous Bi5O7I semiconductor photocatalyst. The semiconductor photocatalyst "porous Bi5O7I" prepared by this invention possesses a complete and stable Bi5O7I crystal structure. Electron-rich Bi atoms form on the surface of the Bi5O7I semiconductor photocatalyst obtained in this special manner. (3‑x)+ It is beneficial for CO2 activation, improves photocatalytic performance, and has excellent product selectivity; it exhibits good photocatalytic stability under long-term testing, promotes efficient and stable conversion of CO2 to CO, and is suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst preparation technology, and particularly relates to a porous bismuth diiodopentane (Bi5O7I) semiconductor photocatalyst, its preparation method and its application. Background Technology

[0002] Currently, due to the excessive use of fossil fuels in modern society, human demand for non-renewable energy is gradually increasing. However, over-exploitation and consumption have led to exacerbated energy shortages, causing serious damage to the Earth's ecological stability, and subsequently triggering numerous problems such as intensified global greenhouse effect, rising sea levels, and environmental degradation. Therefore, it is particularly important to develop and utilize environmentally friendly clean energy and efficiently manage environmental pollution.

[0003] Solar energy, as a representative of clean energy, is favored for its green, safe, and pollution-free characteristics. Inspired by the photosynthetic conversion of nutrients by green plants for growth, researchers have attempted to use semiconductor photocatalysis technology to achieve artificial photosynthesis, completing the conversion of solar energy into chemical energy while ensuring low cost, safety, and effectiveness. However, most semiconductor photocatalysts currently suffer from drawbacks such as insufficient photocatalytic stability and small specific surface area. Currently, significant progress has been made in many fields, including the degradation of waste gas and organic pollutants, photocatalytic water splitting for hydrogen production, and photocatalytic reduction of CO2 to produce high-performance hydrocarbons. This has not only alleviated the energy crisis but also addressed environmental pollution to some extent. In the field of photocatalytic CO2 reduction, the electrons generated by light can reduce carbon dioxide into valuable fuels such as CO, CH4, and CH3OH. The principle of photocatalytic CO2 reduction is roughly as follows: CO2 molecules have low-energy 2πα orbitals and high electron affinity. Because the electron cloud is concentrated on the oxygen atoms on both sides, the C atoms in CO2 exhibit strong electrophilicity and readily accept electrons. Therefore, in the reaction process, it can act as an oxidant, and appropriate electron input methods can activate the adsorbed CO2 to a certain state. Photocatalysts can absorb photons from sunlight and generate electron-hole pairs when the energy of sunlight is greater than its band gap energy. Photocatalytic CO2 reduction technology has attracted widespread attention in order to reduce atmospheric CO2 concentration.

[0004] Among semiconductor photocatalysts, bismuth-based semiconductors possess unique microstructures, band positions, and tunability, enabling them to utilize light energy for catalysis. Furthermore, their low manufacturing cost and simple synthesis techniques have led to their widespread application and research. Therefore, there is an urgent need to design a novel bismuth-containing semiconductor photocatalyst.

[0005] Based on the above analysis, the problems and defects of the existing technology are as follows: most semiconductor photocatalysts currently have shortcomings such as insufficient photocatalytic stability and small specific surface area.

[0006] A critical challenge in photocatalytic CO2 reduction technology is improving the selectivity of CO2 conversion to carbon-containing products. Furthermore, existing literature indicates that factors related to photocatalytic CO2 reduction include: light energy utilization, reaction pathway, charge separation, CO2 adsorption on the catalyst surface, and active sites on the catalyst surface. However, current research on high-energy catalyst surfaces remains incomplete, and the preparation methods are highly complex and resource-intensive. The selectivity of the prepared catalysts still requires further refinement. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a porous Bi5O7I semiconductor photocatalyst, its preparation method, and its application, particularly relating to a porous Bi5O7I semiconductor photocatalyst, its preparation method, and its application in CO2 photoreduction.

[0008] The present invention is achieved as follows: a method for preparing a porous Bi5O7I semiconductor photocatalyst includes: dissolving a Bi-containing polymer in distilled water, adding an I-containing inorganic salt and stirring, then transferring the solution to an autoclave for hydrothermal treatment; centrifuging and drying the hydrothermal reaction product to obtain a powder, grinding the powder and calcining it at high temperature to obtain the porous Bi5O7I semiconductor photocatalyst.

[0009] Furthermore, the preparation method of the porous Bi5O7I semiconductor photocatalyst includes the following steps:

[0010] Step 1: Dissolve the Bi-containing polymer in distilled water to form a colorless mixed liquid A;

[0011] Step 2: Add an inorganic salt containing I to the mixed liquid A, stir until homogeneous to obtain mixture B;

[0012] Step 3: Transfer mixture B to a 100mL polytetrafluoroethylene-lined autoclave, seal it completely, place it in a temperature-controlled oven, heat it, stir it, and perform hydrothermal treatment.

[0013] Step 4: After the hydrothermal reactor cools down naturally, the reacted solution is repeatedly centrifuged and dried to obtain powder C;

[0014] Step 5: After grinding powder C, heat and calcine it in air atmosphere to obtain porous Bi5O7I semiconductor photocatalyst.

[0015] Furthermore, the Bi-containing polymer in step one is a Bi-containing precursor, which is any one or a combination of bismuth nitrate pentahydrate, bismuth citrate, or ammonium bismuth citrate.

[0016] Furthermore, the iodine-containing inorganic salt in step two is any one or a combination of more than one of KI, I2O5 or I2O.

[0017] Furthermore, the molar ratio of mixture A to mixture B in step two is 1-5:1.

[0018] Furthermore, the temperature increase in step three is 120-200 °C, and the stirring time is 10-48 h.

[0019] Furthermore, the calcination temperature in step five is 500-600 °C, the heating rate is 0 < T < 10 °C / min, and the heat preservation time is 1-10 h.

[0020] Another object of the present invention is to provide a porous Bi5O7I semiconductor photocatalyst prepared by the preparation method of the porous Bi5O7I semiconductor photocatalyst described above.

[0021] Furthermore, the porous Bi5O7I semiconductor photocatalyst is composed of nanosheet-like BiOIO3, porous Bi5O7I nanosheets and ultrathin Bi5O7I nanosheets.

[0022] Another object of the present invention is to provide an application of the porous Bi5O7I semiconductor photocatalyst described above in CO2 photoreduction.

[0023] Combined with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0024] First, the semiconductor photocatalyst "porous Bi5O7I" prepared by the present invention has a complete and stable Bi5O7I crystal structure, and the electron-rich Bi formed on the surface of Bi5O7I obtained in this special way (3-x)+ is beneficial to CO2 activation and has excellent product selectivity, promoting the efficient and stable conversion of CO2 to CO.

[0025] In addition, the present invention provides a simple way to construct porous materials and further reveal their formation mechanism. The Bi5O7I prepared by the special method provided by the present invention reduces the recombination of electrons and holes and broadens the light absorption range. In addition, the surface constructed by the preparation method of the present invention is conducive to the activation of reaction molecules, thereby improving the photocatalytic performance and showing good photocatalytic stability under long-term testing. At the same time, the production cost of the method of the present invention is low, the operation is simple, and it is suitable for wide promotion and use.

[0026] Secondly, addressing the shortcomings of most current semiconductor photocatalysts, such as insufficient photocatalytic stability and small specific surface area, this invention provides a photocatalyst exhibiting excellent stability and selectivity in the photocatalytic reduction of carbon dioxide, along with its preparation method. This invention employs a simple preparation method to obtain a porous Bi5O7I semiconductor photocatalyst, which enhances both the activation ability of intermediate products and the light absorption and conversion capabilities.

[0027] Third, does the technical solution of this invention solve a technical problem that people have long desired to solve but have never been able to successfully solve?

[0028] This invention provides a novel and concise method for preparing porous bismuth-based photocatalysts Bi5O7I. Previous studies have shown that methods for preparing porous materials are complex and time-consuming, requiring extensive equipment. This invention offers a new approach to the preparation of porous catalysts, which exhibit excellent selectivity in photocatalytic CO2 reduction tests. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of the preparation method of the porous Bi5O7I semiconductor photocatalyst provided in the embodiments of the present invention;

[0031] Figure 2 This is the XRD pattern of the BiOIO3 photocatalyst provided in the embodiments of the present invention;

[0032] Figure 3 These are XRD images of the Bi5O7I photocatalyst provided in the embodiments of the present invention;

[0033] Figure 4 These are SEM images of the BiOIO3 photocatalyst provided in the embodiments of the present invention;

[0034] Figure 5 This is a SEM image of the Bi5O7I-500 photocatalyst provided in the embodiments of the present invention;

[0035] Figure 6 This is a SEM image of the Bi5O7I-600 photocatalyst provided in the embodiments of the present invention;

[0036] Figure 7 These are TEM images of the BiOIO3 photocatalyst provided in the embodiments of the present invention;

[0037] Figure 8 These are TEM images of the Bi5O7I-500 photocatalyst provided in the embodiments of the present invention;

[0038] Figure 9 These are TEM images of the Bi5O7I-600 photocatalyst provided in the embodiments of the present invention;

[0039] Figure 10 This is the photoluminescence spectrum of the photocatalyst prepared according to the embodiments of the present invention;

[0040] Figure 11 This is a UV spectrum of the photocatalyst prepared according to the embodiments of the present invention;

[0041] Figure 12 This is a comparison chart showing the performance of the photocatalyst prepared according to the embodiments of the present invention in reducing CO2 under visible light. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] To address the problems existing in the prior art, this invention provides a porous Bi5O7I semiconductor photocatalyst, its preparation method, and its application. The invention will be described in detail below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, the preparation method of the porous Bi5O7I semiconductor photocatalyst provided in this embodiment of the invention includes the following steps:

[0045] S101, after dissolving the Bi-containing polymer in distilled water, add the I-containing inorganic salt and stir until homogeneous;

[0046] S102, the mixture obtained in step S101 is transferred to an autoclave for hydrothermal treatment;

[0047] S103, The hydrothermal reaction product obtained in step S102 is repeatedly centrifuged and dried to obtain powder;

[0048] S104, the powder is ground and calcined at high temperature to obtain a porous Bi5O7I semiconductor photocatalyst.

[0049] As a preferred embodiment, the preparation method of the porous Bi5O7I semiconductor photocatalyst provided in this invention specifically includes the following steps:

[0050] S1. Dissolve the Bi-containing polymer in distilled water to form a colorless liquid to obtain mixture A;

[0051] S2. Add a certain proportion of iodine-containing inorganic salt to mixture A, and stir evenly to obtain mixture B;

[0052] S3. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined autoclave, ensure it is completely sealed, then place it in a temperature-controlled oven and heat it up for hydrothermal treatment for several hours;

[0053] S4. After the hydrothermal reaction kettle cools naturally, the reacted solution is centrifuged and dried repeatedly to obtain powder C;

[0054] S5. Grind mixture C carefully and calcine it at high temperature in an air atmosphere to obtain a porous Bi5O7I semiconductor photocatalyst.

[0055] As a preferred embodiment, in step S1 provided by the embodiment of the present invention, the Bi polymer is a Bi-containing precursor, specifically one or a combination of bismuth nitrate pentahydrate, bismuth citrate, and ammonium bismuth citrate.

[0056] As a preferred embodiment, in step S2 provided by the embodiment of the present invention, the iodine-containing inorganic salt includes: one or a mixture of KI, I2O5, and I2O.

[0057] As a preferred embodiment, in step S2 provided by the embodiment of the present invention, the molar ratio of mixture A to mixture B is (1 - 5):1.

[0058] As a preferred embodiment, in step S3 provided by the embodiment of the present invention, the elevated temperature is 120 - 200 °C, and the stirring time is 10 - 48 h.

[0059] As a preferred embodiment, in step S5 provided by the embodiment of the present invention, the calcination temperature is 500 - 600 °C, the heating rate is 0 < T < 10 °C / min, and the holding time is 1 - 10 h.

[0060] In order to prove the creativity and technical value of the technical solution of the present invention, this part is an application embodiment of the technical solution of the claims on a specific product or related technology.

[0061] Example 1: Preparation of photocatalyst

[0062] 1. Preparation of BiOIO3 photocatalyst

[0063] BiOIO3 nanosheets were synthesized using a one-step hydrothermal synthesis method, with deionized water as the solvent and Bi(NO3)3·5H2O and I2O5 as raw materials. The synthesis process is as follows: 6 mmol of Bi(NO3)3·5H2O was weighed using an electronic balance and dissolved in 50 mL of deionized water. The solution was stirred continuously with a magnetic stirrer until completely dissolved. Then, 3 mmol of I2O5 was weighed and added to the above-mentioned bismuth nitrate pentahydrate solution in small amounts several times, while maintaining magnetic stirring at room temperature for 30 min. The resulting suspension was transferred to a 100 mL polytetrafluoroethylene-lined autoclave. After ensuring complete sealing, the autoclave was placed in a temperature-controlled oven and heated to 180 °C for hydrothermal treatment for 12 h. After the heated system cooled naturally to room temperature, the product was collected by filtration and washed three times with distilled water. Finally, BiOIO3 powder was obtained by drying at 60 °C for 6 h.

[0064] 2. Preparation of Bi5O7I photocatalyst

[0065] Bi5O7I was prepared by calcining BiOIO3 nanosheets as a precursor. The specific procedure is as follows: 1 g of the prepared and dried BiOIO3 powder was weighed and dispersed in a quartz crucible. The crucible was then heated to 500℃ using a muffle furnace and held at that temperature for 2 h, with a heating rate of 2℃ / min. The resulting pale yellow powder was Bi5O7I and named Bi5O7I-500. A Bi5O7I sample was obtained by using the same calcination method, but at a different temperature (600℃), and named Bi5O7I-600.

[0066] Example 2: Testing the CO2 reduction activity of the prepared catalyst

[0067] The photocatalytic CO2 reduction activity of the obtained samples was evaluated in a gas-solid phase reaction system with a closed quartz container. 10 mg of photocatalyst was dispersed in 3 mL of deionized water under ultrasonic treatment. This homogeneous solution was then dispersed on the surface of a microporous membrane with a radius of 2.0 cm. After drying the membrane to remove excess water, it was placed in the reaction chamber. The reaction chamber was sealed, the glass valve was opened, and a vacuum was created. High-purity CO2 (99.99%) was then introduced. This process was repeated at least three times. Then, 0.1 mL of water was injected into the reactor using a syringe, maintaining the pressure inside the reactor at approximately 90 kPa. The CO2 photoreduction reaction was conducted using a 300 W xenon lamp (light intensity, 500 mW cm⁻¹). -2 The photocatalytic gaseous products were analyzed hourly using a gas chromatograph (GC) (MC-SPB 10 system, Merry Change Technology CO., LTD) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0068] The embodiments of the present invention have achieved some positive results during the research and development or use process, and have indeed great advantages compared with the prior art. The following content describes them in conjunction with the data, charts and other information of the experimental process.

[0069] like Figure 2 As shown, all diffraction peaks can be assigned to the standard card (ICSD#262019) for BiOIO3, indicating that the BiOIO3 catalyst prepared in this invention is a pure phase. Figure 3 As shown, the typical diffraction peaks of the Bi5O7I compound (PDF#40-0548) at 28.1°, 31.1°, and 33.0° belong to the (312), (004), and (204) crystal planes, respectively, and no peaks of other impurity phases were observed. These results indicate that the sample prepared in this invention possesses high purity and good crystallinity. In other words, the BiOIO3 sample has been successfully transformed into a Bi5O7I catalyst after high-temperature calcination.

[0070] like Figures 4-9 The images show SEM and TEM images of BiOIO3 and Bi5O7I samples. The SEM images reveal that the obtained BiOIO3 sample consists of irregular nanosheets with a layer thickness of approximately 30 nm. Furthermore, Bi5O7I-500 is composed of small nanobulks, while Bi5O7I-600 is a more fragmented sheet. Compared to the BiOIO3 sample, the morphology of the Bi5O7I-500 catalyst remains largely unchanged, except for a slight reduction in the thickness of the Bi5O7I-600 nanosheets (approximately 10–20 nm). This morphological comparison suggests that the calcination temperature significantly affects the material structure; higher calcination temperatures resulted in thinner Bi5O7I nanosheets. TEM images clearly confirm that the BiOIO3 sample is a nanosheet structure with dimensions ranging from several hundred nanometers. More significantly, the Bi5O7I-500 sample exhibits numerous mesopores with diameters ranging from 20 nanometers to several hundred nanometers. Finally, the Bi5O7I-600 catalyst has a fragmented structure with irregular edges and a size smaller than BiOIO3 nanosheets.

[0071] like Figure 10 As shown, the photocurrent intensity (PL) of Bi5O7I-500 is significantly lower than that of BiOIO3. The lowest PL intensity of Bi5O7I-500 indicates excellent carrier separation efficiency. Furthermore, the high PL intensity and lowest photocurrent response of Bi5O7I-600 indicate severe recombination of photogenerated carriers, making it difficult for them to participate in the catalytic reaction. Figure 11The image shows the light absorption properties of the samples. The absorption band edges of BiOIO3 and Bi5O7I-500 are located near 350 nm and 355 nm, respectively, indicating that light absorption is mainly in the ultraviolet region. However, the absorption band edge of Bi5O7I-600 exhibits a red shift, appearing around 425 nm, with a significantly expanded light absorption range, indicating good visible light response. Further analysis was conducted to determine the electron-hole separation capability within the material.

[0072] Depend on Figure 12 It is evident that the Bi5O7I-500 prepared in this invention exhibits the highest photocatalytic CO2 reduction performance and selectivity. In contrast, both BiOIO3 nanosheets and Bi5O7I-600 show lower photocatalytic CO formation rates. The CO product yield on Bi5O7I-500 is 10.67 μmol / g, with no H2 production, approximately twice that of BiOIO3. The enhanced photocatalytic activity is mainly attributed to effective charge separation and suppression of electron-hole recombination.

[0073] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. The application of a porous Bi5O7I semiconductor photocatalyst in CO2 photoreduction, characterized in that, The preparation method of the porous Bi5O7I semiconductor photocatalyst includes: dissolving a Bi-containing precursor in distilled water, adding an inorganic salt containing I and stirring evenly, and then transferring it to an autoclave for hydrothermal treatment; centrifuging and drying the hydrothermal reaction product to obtain a powder, grinding the powder and calcining it at a high temperature to obtain the porous Bi5O7I semiconductor photocatalyst; The preparation method of the porous Bi5O7I semiconductor photocatalyst includes the following steps: Step 1, dissolving a Bi-containing precursor in distilled water to form a colorless mixed liquid A; Step 2, adding an inorganic salt containing I or I2O5 or I2O to the mixed liquid A, and stirring evenly to obtain a mixture B; Step 3, transferring the mixture B to a 100 mL polytetrafluoroethylene-lined autoclave, completely sealing it and putting it into a temperature-controlled oven to raise the temperature, stirring and performing hydrothermal treatment; Step 4, after the hydrothermal reaction kettle cools naturally, centrifuging and drying the reaction solution repeatedly to obtain a powder C; Step 5, after grinding the powder C, heating and holding it for calcination in an air atmosphere to obtain the porous Bi5O7I semiconductor photocatalyst; The Bi-containing precursor in Step 1 is any one or a combination of bismuth nitrate pentahydrate, bismuth citrate or ammonium bismuth citrate.

2. The application of the porous Bi5O7I semiconductor photocatalyst as described in claim 1 in CO2 photoreduction, characterized in that, The inorganic salt containing I in Step 2 is KI.

3. The application of the porous Bi5O7I semiconductor photocatalyst as described in claim 1 in CO2 photoreduction, characterized in that, The molar ratio of the mixture A and the mixture B in Step 2 is 1~5:

1.

4. The application of the porous Bi5O7I semiconductor photocatalyst as described in claim 1 in CO2 photoreduction, characterized in that, The temperature increase in Step 3 is 120~200 °C, and the stirring time is 10~48 h.

5. The application of the porous Bi5O7I semiconductor photocatalyst as described in claim 1 in CO2 photoreduction, characterized in that, The calcination temperature in Step 5 is 500~600 °C, the heating rate is 0<T<10 °C / min, and the holding time is 1~10 h.

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