Bi2O2CO3 nano material as well as preparation method and application thereof

Abstract

The invention provides a Bi2O2CO3 nano material as well as a preparation method and application thereof, and belongs to the technical field of photocatalytic materials. The Bi2O2CO3 nano material provided by the invention is in a tetragonal crystal form, a (002) crystal face is taken as a high-exposure crystal face, the generation of singlet oxygen can be promoted, and the singlet oxygen has relatively high reaction activity and can be subjected to oxidation reaction with organic pollutants to promote degradation; under the illumination condition, Bi2O2CO3 can excite electron transition to generate electron-hole pairs, and singlet oxygen can promote effective separation and transfer of the electron-hole pairs, so that the photocatalytic performance is improved; and the (002) crystal face has a relatively high energy band gap and a good light absorption characteristic, so that visible light can be effectively absorbed, a large number of photo-induced electron-hole pairs can be generated, and visible light excitation is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and in particular relates to a Bi2O2CO3 nano material and a preparation method and application thereof. Background Art

[0002] Water is the source of life and an essential resource for biological survival. However, with the development of industry and the advancement of science and technology, water pollution is becoming increasingly serious, especially harmful organic pollutants, which are difficult to treat and highly toxic. In order to improve water pollution and protect life and health, a variety of technologies for removing organic pollutants from water bodies have been explored, such as chemical precipitation, membrane separation, biological treatment, adsorption, photocatalytic degradation, etc. Semiconductor photocatalytic technology uses solar energy to stimulate semiconductor reactions, generate active oxygen free radicals, and undergo redox reactions with organic matter to achieve the removal of organic pollutants in water bodies; due to its outstanding characteristics such as environmental protection, high efficiency, and economy, it has become a potential way to treat water pollution.

[0003] The core of semiconductor photocatalytic technology lies in semiconductor photocatalysts. Traditional photocatalysts such as TiO2 have disadvantages such as low visible light absorption, narrow light response range, and low quantum transmission efficiency, which limit their application in actual industrial production. 2+ Layers and CO3 2- Aurivillius-type bismuth oxycarbonate (Bi2O2CO3), composed of alternating layers, stands out among many materials because of its unique layered structure that forms a static internal electric field, accelerates the movement of active oxygen free radicals between layers, and improves the catalytic activity of redox reactions. In addition, Bi2O2CO3 also has the advantages of good safety and stability, low price, wide sources, and simple preparation process. It has shown great potential in water pollution control and has become the focus of many researchers.

[0004] However, the existing Bi2O2CO3 still has some problems in photocatalysis: the wide band gap of Bi2O2CO3 limits its activity under visible light, and it needs to be excited under ultraviolet light, which seriously limits its application in practical scenarios; in addition, the photogenerated electron-hole pairs of Bi2O2CO3 are easy to recombine, resulting in low photocatalytic activity. Summary of the invention

[0005] The object of the present invention is to provide a Bi2O2CO3 nano material and a preparation method and application thereof. The Bi2O2CO3 nano material provided by the present invention has high catalytic activity under visible light.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a Bi2O2CO3 nanomaterial, wherein the crystal type of the Bi2O2CO3 nanomaterial is a tetragonal crystal type, the microstructure of the Bi2O2CO3 nanomaterial is a flower-like shape assembled from nanosheets, and the (002) crystal plane accounts for the highest proportion among the exposed crystal planes of the nanosheets.

[0008] Preferably, the thickness of the nanosheet is 5 to 10 nm.

[0009] The present invention also provides a method for preparing the Bi2O2CO3 nanomaterial described in the above technical scheme, comprising: mixing urea, bismuth nitrate, sodium citrate and water and then conducting a hydrothermal reaction to obtain the Bi2O2CO3 nanomaterial; the volume ratio of the amount of urea, bismuth nitrate and sodium citrate to water is (2-6) mmol: (2-3) mmol: (0.5-1.5) mmol: 40 mL; the temperature of the hydrothermal reaction is 170-185° C., and the reaction time is 4-20 h.

[0010] Preferably, the volume ratio of the amount of urea to water is (3-4) mmol:40 mL.

[0011] Preferably, the volume ratio of the amount of sodium citrate to water is (0.8-1.1) mmol:40 mL.

[0012] Preferably, the reaction time of the hydrothermal reaction is 10 to 13 hours.

[0013] Preferably, the reaction temperature of the hydrothermal reaction is 175-180°C.

[0014] Preferably, the ratio of the amount of bismuth nitrate to the volume of water is (2-2.5) mmol:40 mL.

[0015] The present invention also provides the use of the Bi2O2CO3 nanomaterial described in the above technical solution in photocatalytic degradation of organic pollutants.

[0016] Preferably, the photocatalytic degradation is carried out under visible light, and the wavelength λ of the visible light is greater than 420 nm.

[0017] The present invention provides a Bi2O2CO3 nanomaterial, wherein the crystal type of the Bi2O2CO3 nanomaterial is a tetragonal crystal type, and the microstructure of the Bi2O2CO3 nanomaterial is a flower-like shape assembled by nanosheets, and the (002) crystal plane accounts for the highest proportion of the exposed crystal planes of the nanosheets. The Bi2O2CO3 nanomaterial provided by the present invention is a tetragonal crystal type, and the (002) crystal plane is a highly exposed crystal plane, which can promote the generation of singlet oxygen, and the singlet oxygen has a high reactivity, can react with organic pollutants to undergo oxidation, and promote degradation; under illumination conditions, Bi2O2CO3 can excite electron transitions to generate electron-hole pairs, and the singlet oxygen can promote the effective separation and transfer of electron-hole pairs, thereby improving the photocatalytic performance; and the (002) crystal plane has a high energy band gap and good light absorption characteristics, can effectively absorb visible light and generate a large number of photogenerated electron-hole pairs, and realize visible light excitation. The results of the examples show that the Bi2O2CO3 nanomaterial provided by the present invention is used for photocatalytic degradation of tetracycline hydrochloride and rhodamine B. Under visible light with a wavelength of λ>420nm, the degradation rate of rhodamine B in 30 minutes reaches 83%, and the degradation rate of tetracycline hydrochloride in 60 minutes reaches 93%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of the Bi2O2CO3 nanomaterial provided in Example 1 of the present invention;

[0019] Figure 2 An atomic force microscope image of the Bi2O2CO3 nanomaterial provided in Example 1 of the present invention;

[0020] Figure 3 XRD spectrum of the Bi2O2CO3 nanomaterial provided in Example 1 of the present invention;

[0021] Figure 4 This is a SEM image of the Bi2O2CO3 nanomaterial provided in Comparative Example 1 of the present invention;

[0022] Figure 5 XRD spectrum of the Bi2O2CO3 nanomaterial provided in Comparative Example 1 of the present invention;

[0023] Figure 6 This is a SEM image of the Bi2O2CO3 nanomaterial provided in Comparative Example 2 of the present invention;

[0024] Figure 7 XRD spectrum of the Bi2O2CO3 nanomaterial provided in Comparative Example 2 of the present invention;

[0025] Figure 8 The photocatalytic degradation curve of the Bi2O2CO3 nanomaterial provided in Example 1 of the present invention;

[0026] Fig. 9 The photocatalytic degradation curve of Bi2O2CO3 nanomaterial provided in Comparative Example 1 of the present invention;

[0027] Fig.10 This is the photocatalytic degradation curve of the Bi2O2CO3 nanomaterial provided in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0028] All raw materials of the present invention have no particular limitation on their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0029] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses high-purity raw materials or raw materials with a purity commonly used in the field of photocatalytic materials.

[0030] The present invention provides a Bi2O2CO3 nanomaterial, wherein the crystal type of the Bi2O2CO3 nanomaterial is a tetragonal crystal type, the microstructure of the Bi2O2CO3 nanomaterial is a flower-like shape assembled from nanosheets, and the (002) crystal plane accounts for the highest proportion among the exposed crystal planes of the nanosheets.

[0031] In the present invention, the thickness of the nanosheet is preferably 5 to 10 nm, more preferably 5 to 7 nm; as an embodiment of the present invention, the thickness of the nanosheet can be 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm or 9 nm. The thickness of the nanosheet within the above range is conducive to further increasing the specific surface area of ​​the Bi2O2CO3 nanomaterial, thereby improving the catalytic activity.

[0032] The Bi2O2CO3 nanomaterial provided by the present invention is a tetragonal crystal with the (002) crystal plane as a highly exposed crystal plane, which can promote the generation of singlet oxygen. Singlet oxygen has high reactivity and can undergo oxidation reactions with organic pollutants to promote degradation. Under light conditions, Bi2O2CO3 can stimulate electron transitions to generate electron-hole pairs, and singlet oxygen can promote the effective separation and transfer of electron-hole pairs, thereby improving photocatalytic performance. Moreover, the (002) crystal plane has a high energy band gap and good light absorption characteristics, can effectively absorb visible light and generate a large number of photogenerated electron-hole pairs, thereby achieving visible light excitation.

[0033] The present invention also provides a method for preparing the Bi2O2CO3 nanomaterial described in the above technical scheme, comprising: mixing urea, bismuth nitrate, sodium citrate and water and then conducting a hydrothermal reaction to obtain the Bi2O2CO3 nanomaterial; the volume ratio of the amount of urea, bismuth nitrate and sodium citrate to water is (2-6) mmol: (2-3) mmol: (0.5-1.5) mmol: 40 mL; the temperature of the hydrothermal reaction is 170-185° C., and the reaction time is 4-20 h.

[0034] The present invention mixes urea, bismuth nitrate, sodium citrate and water and then performs a hydrothermal reaction to obtain a Bi2O2CO3 nano material.

[0035] The present invention has no particular limitation on the raw material forms of the urea, bismuth nitrate and sodium citrate, and any raw material forms conventional in the art may be used. In an embodiment of the present invention, the raw material of the bismuth nitrate is bismuth nitrate pentahydrate, the raw material of the sodium citrate is sodium citrate dihydrate, and the water is deionized water.

[0036] In the present invention, the volume ratio of the amount of urea to water is (2-6) mmol:40 mL, preferably (3-4) mmol:40 mL; as an embodiment of the present invention, the volume ratio of the amount of urea to water can be 2 mmol:40 mL, 3 mmol:40 mL, 4 mmol:40 mL, 5 mmol:40 mL or 2 mmol:40 mL. The amount of urea used within the above range is conducive to further improving the catalytic activity of the Bi2O2CO3 nanomaterial.

[0037] In the present invention, the volume ratio of the amount of bismuth nitrate to water is (2-3) mmol:40 mL, preferably (2-2.5) mmol:40 mL; as an embodiment of the present invention, the volume ratio of the amount of bismuth nitrate to water can be 2 mmol:40 mL, 2.2 mmol:40 mL, 2.4 mmol:40 mL, 2.6 mmol:40 mL or 2.8 mmol:40 mL. The amount of bismuth nitrate used within the above range is conducive to further improving the catalytic activity of the Bi2O2CO3 nanomaterial.

[0038] In the present invention, the volume ratio of the amount of sodium citrate to water is (0.5-1.5) mmol:40 mL, preferably (0.8-1.1) mmol:40 mL; as an embodiment of the present invention, the volume ratio of the amount of sodium citrate to water can be 0.6 mmol:40 mL, 0.7 mmol:40 mL, 0.9 mmol:40 mL, 1 mmol:40 mL or 1.2 mmol:40 mL. Sodium citrate, as a structure directing agent, can induce the lattice structure of the crystal and promote the exposure of the (002) crystal plane; the amount of sodium citrate used within the above range is conducive to further improving the catalytic activity of the Bi2O2CO3 nanomaterial.

[0039] The present invention has no particular limitation on the specific mixing method, and a conventional mixing method in the art can be used. As an embodiment of the present invention, urea can be first added to water, and sodium citrate can be added after dissolution, and bismuth nitrate can be added after dissolution; as an embodiment of the present invention, the dissolution can be accelerated by stirring and ultrasound; the present invention has no particular requirements on the specific parameters of the stirring and ultrasound, as long as the raw materials can be dissolved.

[0040] In the present invention, the temperature of the hydrothermal reaction is 170-185° C., preferably 175-180° C.; as an embodiment of the present invention, the temperature of the hydrothermal reaction can be 172° C., 176° C., 177° C., 178° C., 179° C. or 181° C. The temperature of the hydrothermal reaction is within the above range, which is conducive to further improving the catalytic activity of the Bi2O2CO3 nanomaterial.

[0041] In the present invention, the reaction time of the hydrothermal reaction is 4 to 20 hours, preferably 10 to 13 hours; as an embodiment of the present invention, the reaction time of the hydrothermal reaction can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours or 14 hours. The reaction time of the hydrothermal reaction within the above range is conducive to further improving the catalytic activity of the Bi2O2CO3 nanomaterial.

[0042] The present invention has no particular limitation on the hydrothermal reaction device, and a conventional hydrothermal reaction device in the art can be used. As an embodiment of the present invention, the hydrothermal reaction device can be a reactor, and the inner lining of the reactor can be polytetrafluoroethylene.

[0043] After the hydrothermal reaction is completed, the present invention preferably washes and dries the product; the present invention has no special requirements for the specific parameters of the washing and drying, and the conventional washing and drying parameters in the art can be used. The present invention can remove impurities on the surface of the Bi2O2CO3 nanomaterial by washing the product, and can remove moisture on the surface of the Bi2O2CO3 nanomaterial by drying.

[0044] The present invention uses bismuth nitrate and urea as raw materials to prepare Bi2O2CO3 nanomaterials, and by adding sodium citrate as a structure-directing agent, the proportion of (002) crystal planes in the exposed crystal planes of the Bi2O2CO3 nanomaterials is made the highest; the catalytic activity of the Bi2O2CO3 nanomaterials can be further improved by limiting the concentration of the raw materials and the parameters of the hydrothermal reaction.

[0045] The present invention also provides the use of the Bi2O2CO3 nanomaterial described in the above technical solution in photocatalytic degradation of organic pollutants.

[0046] In the present invention, the photocatalytic degradation is preferably carried out under visible light, and the wavelength λ of the visible light is preferably > 420 nm. The Bi2O2CO3 nanomaterial provided by the present invention is photocatalytically degraded under visible light, which reduces the difficulty and cost of application and is conducive to expanding the scope of application.

[0047] The present invention has no particular limitation on other parameters of the application, and conventional application parameters in the art may be used. As an embodiment of the present invention, 0.025 g of Bi2O2CO3 nanomaterial can be added to 50 mL of a 20 mg / L organic pollutant solution, stirred in the dark for 30 min, and then irradiated under visible light for catalytic degradation.

[0048] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] A Bi2O2CO3 nanomaterial, the preparation method is as follows:

[0051] 0.24 g of urea was dissolved in 40 mL of deionized water, stirred and ultrasonically dissolved; then 0.2941 g of sodium citrate dihydrate was added to the urea solution, stirred and ultrasonically dissolved; then 0.97 g of bismuth nitrate pentahydrate was added to the above solution, stirred and ultrasonically dissolved for 10 minutes; finally, the mixed solution was transferred to a 50 mL reactor lined with polytetrafluoroethylene for hydrothermal reaction at 180 ° C for 12 hours. After the reaction was completed, the Bi2O2CO3 nanomaterial was obtained by washing and drying, and named BOC-N.

[0052] BOC-N was observed using a scanning electron microscope, and the SEM image was obtained as follows Figure 1 As shown, from Figure 1It can be seen that BOC-N is a flower-like structure formed by the spiral assembly of nanosheets with nanometer-scale thickness.

[0053] The thickness of the nanosheets was tested using an atomic force microscope, and the following images were obtained: Figure 2 As shown, the line segments in the figure indicate the locations where the thickness is measured. Figure 2 It can be seen that the thickness of the BOC-N nanosheets is 5.4 nm.

[0054] BOC-N was analyzed using an X-ray diffractometer, and the XRD pattern was obtained as follows: Figure 3 As shown, from Figure 3 It can be seen that the (002) peak of BOC-N is significantly larger than the standard value (JCPDS#84-1752). The calculated intensity ratio of the (002) peak to the strongest (161) peak is 1.19, which is 3.4 times higher than the standard value of 0.35, indicating that the (002) crystal plane has the largest exposure ratio.

[0055] Example 2

[0056] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the hydrothermal reaction time is 4 hours.

[0057] Example 3

[0058] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the hydrothermal reaction time is 8 hours.

[0059] Example 4

[0060] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the hydrothermal reaction time is 16 hours.

[0061] Example 5

[0062] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the hydrothermal reaction time is 20 hours.

[0063] Example 6

[0064] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the amount of urea used is 0.12 g (2 mmol).

[0065] Example 7

[0066] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the amount of urea used is 0.36 g (6 mmol).

[0067] Example 8

[0068] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the amount of sodium citrate dihydrate used is 0.1471 g (0.5 mmol).

[0069] Example 9

[0070] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the amount of sodium citrate dihydrate used is 0.4412 g (1.5 mmol).

[0071] Comparative Example 1

[0072] A Bi2O2CO3 nanomaterial, denoted as BOC-G; the preparation method is the same as that of Example 1, except that sodium citrate dihydrate is replaced by mannitol of the same amount (1 mmol).

[0073] BOC-G was observed using a scanning electron microscope, and the SEM image was obtained as follows Figure 4 As shown, from Figure 4 It can be seen that BOC-G is in the form of relatively uniform and highly dispersed blocks with a lateral size of 100 to 300 nm.

[0074] BOC-G was analyzed using an X-ray diffractometer, and the XRD pattern was obtained as follows: Figure 5 As shown, from Figure 5 It can be seen that BOC-G is very close to the standard PDF card (JCPDS#84-1752), indicating that the (161) crystal plane has the largest exposure ratio.

[0075] Comparative Example 2

[0076] A Bi2O2CO3 nanomaterial, denoted as BOC; the preparation method is the same as that of Example 1, except that sodium citrate dihydrate is omitted.

[0077] BOC was observed using a scanning electron microscope, and the SEM image was obtained as follows Figure 6 As shown, from Figure 6 It can be seen that BOC is a micron-sized block structure.

[0078] BOC was analyzed using an X-ray diffractometer, and the XRD pattern was obtained as follows: Figure 7 As shown, from Figure 7 It can be seen that the intensity ratio of the (040) peak of BOC to the strongest (161) peak is 1.27, which is about 4.7 times higher than the standard value (JCPDS#84-1752) of 0.27, indicating that the (040) crystal plane has the largest exposure ratio.

[0079] Comparative Example 3

[0080] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the amount of bismuth nitrate pentahydrate used is 0.485 g (1 mmol).

[0081] Comparative Example 4

[0082] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the amount of bismuth nitrate pentahydrate used is 1.94 g (4 mmol).

[0083] Comparative Example 5

[0084] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the temperature of the hydrothermal reaction is 160°C.

[0085] Comparative Example 6

[0086] A Bi2O2CO3 nanomaterial, the preparation method is the same as that of Example 1, except that the temperature of the hydrothermal reaction is 200°C.

[0087] Test Example 1

[0088] Photocatalytic degradation was performed on BOC-N provided in Example 1, BOC-G provided in Comparative Example 1, and BOC provided in Comparative Example 2, respectively: 0.025 g of Bi2O2CO3 nanomaterial was placed in 50 mL of tetracycline hydrochloride and rhodamine B solution with a concentration of 20 mg / L, respectively, and stirred for 30 min in a dark environment. After adsorption-desorption equilibrium was reached, it was placed under visible light (λ>420 nm) for irradiation. The solution was taken every several minutes to measure its UV-visible absorption spectrum, and the degradation curve was obtained as shown in FIG. Figures 8 to 10 As shown. Figure 8 It can be seen that the degradation rate of rhodamine B by BOC-N provided in Example 1 reached 93% in 30 minutes and the degradation rate of tetracycline hydrochloride reached 83% in 60 minutes. Fig. 9 It can be seen that the degradation rate of rhodamine B by BOC-D provided in Comparative Example 1 is only 8% in 30 min, and the degradation rate of tetracycline hydrochloride in 60 min is only 22%; Fig.10 It can be seen that the degradation rate of rhodamine B by BOC provided in Comparative Example 1 is only 5% in 30 min, and the degradation rate of tetracycline hydrochloride is only 3% in 60 min. This indicates that the exposure of the (002) crystal plane improves the visible light catalytic activity of Bi2O2CO3 nanomaterials.

[0089] Test Example 2

[0090] The degradation rate of Rhodamine B by the Bi2O2CO3 nanomaterials provided in Examples 1 to 9 and Comparative Examples 1 to 6 was tested for 30 minutes according to the method of Test Example 1. The results are shown in Table 1.

[0091] Table 1 Photocatalytic degradation test results of Bi2O2CO3 nanomaterials provided in Examples and Comparative Examples

[0092] 30min Rhodamine B degradation rate (%) Example 1 93 Example 2 40 Example 3 88 Example 4 85 Example 5 50 Example 6 41 Example 7 74 Example 8 36 Example 9 44 Comparative Example 1 8 Comparative Example 2 5 Comparative Example 3 24 Comparative Example 4 32 Comparative Example 5 10 Comparative Example 6 15

[0093] By analyzing the experimental results of Examples 1 to 5 in Table 1, it can be seen that the time of the hydrothermal reaction is 4 to 20 hours, and the prepared Bi2O2CO3 nanomaterial has good photocatalytic activity.

[0094] It can be seen from the experimental results of Examples 1, 6 and 7 that when the volume ratio of the amount of urea to water is in the range of (2-6) mmol:40 mL, the prepared Bi2O2CO3 nanomaterial has good photocatalytic activity.

[0095] The experimental results of Examples 1, 8 and 9 show that when the volume ratio of the amount of sodium citrate to water is in the range of (0.5-1.5) mmol:40 mL, the prepared Bi2O2CO3 nanomaterial has good photocatalytic activity.

[0096] It can be seen from the experimental results of Example 1 and Comparative Examples 3 and 4 that when the volume ratio of the amount of bismuth nitrate to water is not within the range of (2-3) mmol:40 mL, the photocatalytic activity of the prepared Bi2O2CO3 nanomaterial is poor.

[0097] It can be seen from the experimental results of Example 1 and Comparative Examples 5 and 6 that when the temperature of the hydrothermal reaction is not within the range of 170-185°C, the photocatalytic activity of the prepared Bi2O2CO3 nanomaterial is relatively poor.

[0098] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A Bi2O2CO3 nanomaterial, wherein the crystal type of the Bi2O2CO3 nanomaterial is a tetragonal crystal, and the microstructure of the Bi2O2CO3 nanomaterial is a flower-like shape assembled by nanosheets, and the (002) crystal plane accounts for the highest proportion among the exposed crystal planes of the nanosheets.

2. The Bi2O2CO3 nanomaterial according to claim 1, characterized in that: The thickness of the nanosheet is 5-10 nm.

3. The method for preparing the Bi2O2CO3 nanomaterial according to claim 1 or 2, comprising: Urea, bismuth nitrate, sodium citrate and water are mixed and then subjected to hydrothermal reaction to obtain Bi2O2CO3 nanomaterials; the volume ratio of the amount of urea, bismuth nitrate and sodium citrate to water is (2-6) mmol: (2-3) mmol: (0.5-1.5) mmol: 40 mL; the temperature of the hydrothermal reaction is 170-185° C., and the reaction time is 4-20 h.

4. The preparation method according to claim 3, characterized in that: The volume ratio of the amount of urea to water is (3-4) mmol:40 mL.

5. The preparation method according to claim 3, characterized in that: The volume ratio of the amount of sodium citrate to water is (0.8-1.1) mmol:40 mL.

6. The preparation method according to claim 3, characterized in that: The reaction time of the hydrothermal reaction is 10 to 13 hours.

7. The preparation method according to claim 3 or 6, characterized in that: The reaction temperature of the hydrothermal reaction is 175-180°C.

8. The preparation method according to claim 3, characterized in that: The ratio of the amount of bismuth nitrate to the volume of water is (2-2.5) mmol:40 mL.

9. Use of the Bi2O2CO3 nanomaterial according to claim 1 or 2 or the Bi2O2CO3 nanomaterial prepared by the preparation method according to any one of claims 3 to 8 in photocatalytic degradation of organic pollutants.

10. The use according to claim 9, characterized in that: The photocatalytic degradation is carried out under visible light, and the wavelength λ of the visible light is greater than 420 nm.

Images