阅读说明：本技术 一种Ag/g-C3N4/Bi2O2CO3异质结光催化剂及其制备方法和应用 (Ag/g-C3N4/Bi2O2CO3Heterojunction photocatalyst and preparation method and application thereof ) 是由 谈国强 王敏 张碧鑫 冯帅军 王勇 毕钰 杨迁 任慧君 夏傲 刘文龙 于 2021-09-29 设计创作，主要内容包括：本发明提供一种Ag/g-C-(3)N-(4)/Bi-(2)O-(2)CO-(3)异质结光催化剂及其制备方法和应用,其是Ag单质、类石墨相g-C-(3)N-(4)和Bi-(2)O-(2)CO-(3)三者的复合材料,其中,Ag单质归属于立方晶系,空间点群为Fm-3m(225)；Bi-(2)O-(2)CO-(3)归属于四方晶系,空间点群为I4/mmm(139)。所述Ag/g-C-(3)N-(4)/Bi-(2)O-(2)CO-(3)异质结光催化剂在200-800nm范围内表现出全吸收特性,在模拟太阳光和近红外光照射下均可降解四环素和环丙沙星等抗生素,且光催化性能有了显著提高。(The invention provides Ag/g-C 3 N 4 /Bi 2 O 2 CO 3 Heterojunction photocatalyst, preparation method and application thereof, wherein the heterojunction photocatalyst is Ag simple substance and graphite-like phase g-C 3 N 4 And Bi 2 O 2 CO 3 The composition of the three componentsThe material, wherein the Ag simple substance belongs to a cubic crystal system, and the space point group is Fm-3m (225); bi 2 O 2 CO 3 The space point group is I4/mmm (139) belonging to the tetragonal system. The Ag/g-C 3 N 4 /Bi 2 O 2 CO 3 The heterojunction photocatalyst shows full absorption characteristics in the range of 200-800nm, can degrade antibiotics such as tetracycline and ciprofloxacin under the irradiation of simulated sunlight and near infrared light, and has remarkably improved photocatalytic performance.)

1. Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst is characterized in that the heterojunction photocatalyst is Ag simple substance and graphite-like phase g-C₃N₄And Bi₂O₂CO₃The Ag simple substance belongs to a cubic crystal system, and the space point group is Fm-3m (225); bi₂O₂CO₃The space point group is I4/mmm (139) belonging to the tetragonal system.

2. Ag/g-C according to claim 1₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst, characterized in that Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst shows full absorption characteristics in the range of 200-800 nm.

3. Ag/g-C according to claim 1 or 2₃N₄/Bi₂O₂CO₃The preparation method of the heterojunction photocatalyst is characterized by comprising the following steps:

step 1, AgNO₃Dissolving in absolute ethyl alcohol to obtain a clear and transparent uniform solution;

step 2, mixing g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatmentObtaining uniformly dispersed suspension;

step 3, adding NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 4, carrying out solvothermal reaction on the obtained reaction precursor liquid, and after the reaction is finished, washing and drying the obtained precipitate to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

4. Ag/g-C according to claim 3₃N₄/Bi₂O₂CO₃The preparation method of the heterojunction photocatalyst is characterized in that the AgNO is₃、g-C₃N₄And NaBiO₃In a molar ratio of (0.03-0.12): (0.08-0.12): (0.04-0.06).

5. Ag/g-C according to claim 3₃N₄/Bi₂O₂CO₃The preparation method of the heterojunction photocatalyst is characterized in that AgNO is contained in reaction precursor liquid₃、g-C₃N₄And NaBiO₃The concentration of (b) is 0.03-0.12 mol. L^-1、0.08-0.12mol·L^-1、0.04-0.06mol·L^-1。

6. Ag/g-C according to claim 3₃N₄/Bi₂O₂CO₃The preparation method of the heterojunction photocatalyst is characterized in that the temperature of the solvothermal reaction is 120-160 ℃, and the reaction time is 12-16 h.

7. Ag/g-C according to claim 3₃N₄/Bi₂O₂CO₃A method for preparing a heterojunction photocatalyst, characterized in that said g-C₃N₄The powder is obtained by high-temperature heat treatment of urea.

8. Ag/g-C according to claim 3₃N₄/Bi₂O₂CO₃The preparation method of the heterojunction photocatalyst is characterized in that in the step 4, washing is respectively carried out by using deionized water and absolute ethyl alcohol.

9. Ag/g-C according to claim 1 or 2₃N₄/Bi₂O₂CO₃The application of the heterojunction photocatalyst in catalyzing and degrading antibiotics under the irradiation of sunlight or near infrared rays.

10. The use of claim 9, wherein the antibiotic is tetracycline or ciprofloxacin.

Technical Field

The invention belongs to the field of functional materials, and particularly relates to Ag/g-C₃N₄/Bi₂O₂CO₃Heterojunction photocatalyst and preparation and application thereof.

Background

Antibiotics can be used for treating bacterial infection and have remarkable effect, so the antibiotics are regarded as one of important achievements in the microbial history and can be applied to the industries of breeding industry, animal husbandry and the like. However, antibiotics cannot be completely metabolized in organisms, and enter rivers, lakes and underground water through water circulation after being discharged to the outside of the bodies, so that the aquatic ecological balance is seriously damaged. Even the existence of antibiotics with lower concentration can also endanger the health of human bodies and improve the drug resistance of bacteria. Therefore, it is imperative to solve the problem of antibiotic contamination.

Physical chemical adsorption, chemical oxidation, biological oxidation and electrocatalysis can be used for removing antibiotics in water, but the energy consumption is high, the operation is difficult, the removal effect on low-concentration antibiotics is poor, and secondary pollution is possibly caused. Research shows that the photocatalysis technology can be used for removing antibiotics in water and directly decomposing the antibiotics into H₂O and CO₂No secondary pollution, andthe solar energy is an energy source, and is green, environment-friendly and renewable.

Conventional photocatalysts, e.g. TiO₂、ZnO、g-C₃N₄And the defects of low solar energy utilization rate, high photoproduction electron-hole pair recombination rate and the like are main reasons for limiting the photocatalytic degradation antibiotic reaction activity. Therefore, the preparation of a high-activity photocatalytic material with wide spectral response for treating antibiotic pollution is a great problem to be solved urgently. Bi₂O₂CO₃Is a novel photocatalytic material, and has a typical two-dimensional layered structure, interlayer [ Bi ]₂O₂]²⁺And CO₃ ^2-The alternating arrangement forms a built-in electric field, which is beneficial to photo-generated charge separation. But with TiO₂Similarly, Bi₂O₂CO₃The forbidden band width is large, the ultraviolet light only accounts for about 5% of the solar spectrum, and the utilization rate of the solar energy is low; and Bi₂O₂CO₃Is a typical oxidation type semiconductor, the position of a conduction band is low, and photoproduction electrons can not reduce O₂The molecule generates superoxide radical to participate in the photocatalytic reaction. And a reduced semiconductor g-C₃N₄Composite construction of Z-type heterojunction for improving Bi₂O₂CO₃The optical performance can also improve the oxidation-reduction capability of the whole material system.

Even so, g-C₃N₄/Bi₂O₂CO₃Most visible light and near infrared light, which accounts for about 50% of the solar spectrum, cannot be utilized.

Disclosure of Invention

The invention aims to provide Ag/g-C₃N₄/Bi₂O₂CO₃Heterojunction photocatalyst, preparation method and application thereof, and Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst shows full absorption characteristics in the range of 200-800nm, can degrade antibiotics such as tetracycline and ciprofloxacin under the irradiation of simulated sunlight and near infrared light, and has remarkably improved photocatalytic performance.

The invention is realized by the following technical scheme:

Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst which is Ag simple substance and graphite-like phase g-C₃N₄And Bi₂O₂CO₃The Ag simple substance belongs to a cubic crystal system, and the space point group is Fm-3m (225); bi₂O₂CO₃The space point group is I4/mmm (139) belonging to the tetragonal system.

Preferably, the Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst shows full absorption characteristics in the range of 200-800 nm.

The Ag/g-C₃N₄/Bi₂O₂CO₃The preparation method of the heterojunction photocatalyst comprises the following steps:

step 1, AgNO₃Dissolving in absolute ethyl alcohol to obtain a clear and transparent uniform solution;

step 2, mixing g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment to obtain a uniformly dispersed suspension;

step 3, adding NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 4, carrying out solvothermal reaction on the obtained reaction precursor liquid, and after the reaction is finished, washing and drying the obtained precipitate to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Preferably, AgNO₃、g-C₃N₄And NaBiO₃In a molar ratio of (0.03-0.12): (0.08-0.12): (0.04-0.06).

Preferably, AgNO is added to the reaction precursor solution₃、g-C₃N₄And NaBiO₃The concentration of (b) is 0.03-0.12 mol. L^-1、0.08-0.12mol·L^-1、0.04-0.06mol·L^-1。

Preferably, the temperature of the solvothermal reaction is 120-160 ℃, and the reaction time is 12-16 h.

Preferably, said g-C₃N₄The powder is obtained by high-temperature heat treatment of urea.

Preferably, in step 4, washing is performed by using deionized water and absolute ethyl alcohol respectively.

The Ag/g-C₃N₄/Bi₂O₂CO₃The application of the heterojunction photocatalyst in catalyzing and degrading antibiotics under the irradiation of sunlight or near infrared rays.

Preferably, the antibiotic is tetracycline or ciprofloxacin.

Compared with the prior art, the invention has the following beneficial technical effects:

Ag/g-C of the invention₃N₄/Bi₂O₂CO₃In the heterojunction catalyst, g-C₃N₄And Bi₂O₂CO₃Between which a Z-type heterojunction is formed, g-C₃N₄Photo-generated holes and Bi of valence band₂O₂CO₃Photoproduction-electron recombination of conduction band, retention of g-C with strong redox ability₃N₄Photo-generated electrons of conduction band and Bi₂O₂CO₃The photogenerated holes of the valence band participate in the photocatalytic reaction. The noble metal Ag has obvious LSPR effect, and under the irradiation of near infrared light, Ag interacts with incident photon to produce high energy hot electron and hot hole, and the hot electron may relax to g-C₃N₄And Bi₂O₂CO₃The position of the conduction band of (A) participates in the photocatalytic reaction, g-C₃N₄And Bi₂O₂CO₃The conduction band provides an energy level platform for thermal electron relaxation of Ag, the separation efficiency of thermal electrons and hot holes is improved, and the hot holes reserved on Ag sites can directly participate in photocatalytic reaction. The Ag is coupled with the semiconductor to form a Schottky barrier at an interface, the Ag has an obvious near field enhancement effect, and the formation of the Schottky barrier and the near field enhancement effect can accelerate the generation and separation of photon-generated carriers and improve the separation efficiency of electron-hole pairs. Therefore, the invention introduces Ag, can obviously widen the photoresponse range of the catalyst, and simultaneously improves the photoproduction by utilizing the Schottky barrier of the metal and semiconductor interfaceCarrier separation efficiency. Thus, the Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst can degrade antibiotics such as tetracycline and ciprofloxacin under the irradiation of simulated sunlight and near infrared light, and has photocatalytic activity higher than g-C₃N₄、Bi₂O₂CO₃、Ag/g-C₃N₄And Ag/Bi₂O₂CO₃And can be used for photocatalytic treatment of antibiotic pollution.

The process of the invention uses g-C₃N₄、AgNO₃、NaBiO₃Preparing Ag/g-C by a solvothermal reaction process by using the raw material₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst is simple to operate.

Furthermore, the preparation method has short reaction time and mild reaction conditions.

Ag/g-C of the invention₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst can degrade antibiotics such as tetracycline and ciprofloxacin under the irradiation of simulated sunlight and near infrared light, and can be used for photocatalytic treatment of antibiotic pollution.

Drawings

FIG. 1 is an XRD pattern of a catalyst powder prepared according to the present invention.

FIG. 2 shows the UV-visible diffuse reflectance spectrum of the catalyst powder prepared according to the present invention.

FIG. 3 is a degradation curve of the catalyst powder prepared by the present invention under simulated solar radiation to tetracycline.

FIG. 4 is an apparent rate constant for the decomposition of tetracycline by the catalyst powder prepared in accordance with the present invention under simulated solar irradiation.

FIG. 5 is a degradation curve of ciprofloxacin under simulated sunlight irradiation by the catalyst powder prepared by the invention.

FIG. 6 is an apparent rate constant of degradation of ciprofloxacin under simulated solar irradiation of the catalyst powder prepared by the invention.

FIG. 7 is a graph showing the degradation curve of the catalyst powder prepared by the present invention to tetracycline under near infrared light irradiation.

FIG. 8 is a degradation curve of ciprofloxacin under near infrared light irradiation of the catalyst powder prepared by the invention.

FIG. 9 shows Ag/g-C prepared in example₃N₄/Bi₂O₂CO₃The heterojunction can be used for simulating the cycle experiment result of the tetracycline degradation under the irradiation of sunlight.

FIG. 10 shows Ag/g-C prepared in example₃N₄/Bi₂O₂CO₃The heterojunction can be used for simulating the cycle experiment result of the tetracycline degradation under the irradiation of sunlight.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

Comparative example 1

30g of urea were placed in a quartz crucible with a lid and then in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, the reaction is finished after the temperature is preserved for 4 hours, and g-C is obtained after the reaction is cooled to the room temperature along with the furnace₃N₄A photocatalyst.

Comparative example 2

0.5g of NaBiO₃Dispersing into 30mL of absolute ethyl alcohol, stirring for 10min, adding 30 drops of concentrated nitric acid, and stirring for 10min to obtain a reaction precursor solution; transferring the reaction precursor solution into a 60mL hydrothermal reaction kettle with the filling ratio of about 60%, heating the reaction precursor solution from room temperature to 160 ℃ for 60min, and preserving the temperature for 16h to finish the reaction; naturally cooling to room temperature after the reaction is finished, washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol respectively, and drying for 24 hours at 70 ℃ to obtain Bi₂O₂CO₃A photocatalyst.

Comparative example 3

0.304g of AgNO₃Dispersing into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution; then 0.3g g-C was added to the above solution₃N₄Performing ultrasonic treatment on the powder for 30min to obtain reaction precursor liquid; transferring the reaction precursor solution into a 60mL hydrothermal reaction kettle, heating the reaction precursor solution from room temperature to 160 ℃ for 60min, and preserving the temperature for 16hCarrying out reaction; naturally cooling to room temperature after the reaction is finished, washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol respectively, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄A photocatalyst.

Comparative example 4

0.304g of AgNO₃Dispersing into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution; then 0.5g NaBiO was added to the above solution₃Performing ultrasonic treatment on the powder for 30min to obtain reaction precursor liquid; transferring the reaction precursor solution into a 60mL hydrothermal reaction kettle, heating the reaction precursor solution from room temperature to 160 ℃ for 60min, and preserving the temperature for 16h to finish the reaction; naturally cooling to room temperature after the reaction is finished, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/Bi₂O₂CO₃A photocatalyst.

Example 1

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.16g of AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, mixing 0.3g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.35g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 150 ℃ for 60min, and preserving the temperature for 12h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃Heterojunction lightA catalyst.

Example 2

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.305g AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, mixing 0.25g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.42g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 150 ℃ for 60min, and preserving the temperature for 12h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 3

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.6g of AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, 0.35g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.5g NaBiO into the suspension₃Powder, stirringUniformly obtaining reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 120 ℃ for 60min, and preserving heat for 16h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 4

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.6g of AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, mixing 0.25g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.42g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 150 ℃ for 60min, and preserving the temperature for 12h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 5

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate of the temperature rising device is increased from room temperature to 550 ℃, and the temperature is keptAfter warming for 4h, furnace cooling to room temperature to obtain g-C₃N₄Powder;

step 2, 0.305g AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, 0.35g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.42g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 150 ℃ for 60min, and preserving the temperature for 12h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 6

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.305g AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, mixing 0.25g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.5g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 150 ℃ for 60min, and preserving the temperature for 12h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 7

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.6g of AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, mixing 0.3g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.42g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 150 ℃ for 60min, and preserving heat for 16h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 8

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.16g of AgNO₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, mixing 0.3g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.6g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 140 ℃ for 60min, and preserving the temperature for 14h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Example 9

Step 1, 30g of urea was placed in a quartz crucible with a lid and placed in a muffle furnace at 15 ℃ min^-1The temperature rising rate is increased from room temperature to 550 ℃, and after heat preservation is carried out for 4 hours, the temperature is cooled to room temperature along with the furnace, thus obtaining g-C₃N₄Powder;

step 2, 0.304g AgNO is added₃Dissolving into 30mL of absolute ethyl alcohol, and stirring for 10min to obtain a clear and transparent uniform solution;

step 3, 0.35g g-C₃N₄Dispersing the powder into the uniform solution, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed suspension;

step 4, adding 0.6g NaBiO into the suspension₃Uniformly stirring the powder to obtain reaction precursor liquid;

step 5, transferring the obtained reaction precursor liquid into a hydrothermal reaction kettle with polytetrafluoroethylene as a lining, wherein the filling ratio is about 60%, heating the reaction kettle from room temperature to 120 ℃ for 60min, and preserving heat for 16h to finish the reaction;

step 6, after the reaction is finished, cooling the hydrothermal kettle to room temperature along with the furnace, respectively washing the obtained precipitate for 3 times by using deionized water and absolute ethyl alcohol, and drying for 24 hours at 70 ℃ to obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

The above conclusions and mechanisms are specifically explained below.

FIG. 1 is an XRD pattern of the catalyst powder prepared in the present invention, in which a, c, d correspond to the XRD patterns of the powders prepared in comparative example 1, comparative example 3, comparative example 4, respectively, and e-g correspond to the XRD patterns of the powders prepared in examples 1 to 3, respectively. Ag, graphite-like phase g-C can be observed₃N₄And Bi₂O₂CO₃Wherein the Ag simple substance belongs to a cubic system, and the space point group is Fm-3m (225); bi₂O₂CO₃The space point group is I4/mmm (139) belonging to the tetragonal system. Proves that the Ag/g-C is successfully prepared by the method₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst.

Ag/g-C₃N₄/Bi₂O₂CO₃The mechanism of heterojunction formation is as follows: first, AgNO₃Is dissolved in CH₃CH₂In OH, dissociation to form Ag⁺And NO₃ ^-Ion (reaction formula (1)). Preparation of g-C by calcining urea₃N₄Contains a certain concentration of nitrogen vacancy, and local electrons are bound near the nitrogen vacancy, so that the nitrogen vacancy is led to be in CH₃CH₂OH presents a negative surface potential. Introducing g-C into the solution₃N₄Then, Ag of positive electricity⁺The ions are adsorbed on g-C by electrostatic attraction₃N₄Near the nitrogen vacancy of (2) to form g-C₃N₄·Ag⁺A structural unit (reaction formula (2)). Adding NaBiO into the reaction system₃And (6) finally. CH (CH)₃CH₂OH and NaBiO₃By esterification to CH₃CH₂OBiO₂(reaction formula (3)). g-C due to incomplete polycondensation of urea₃N₄C atom site of (A) has adsorbed thereto a large amount of-NH₂A group. During magnetic stirring, g-C₃N₄surface-NH₂The groups are detached to expose the active site. CH produced by esterification₃CH₂OBiO₂Adsorbing on Ag⁺·g-C₃N₄Surface of the catalyst is formed by-NH₂Shedding of the exposed active sites to form Ag⁺·g-C₃N₄·CH₃CH₂OBiO₃(reaction formula (4)).

During the solvothermal reaction, the adsorption of the compound in g-C is carried out as the reaction temperature increases₃N₄Surface Ag⁺The ions are reduced to Ag simple substance in situ to form Ag/g-C₃N₄；CH₃CH₂OBiO₂Is thermally reduced and decomposed into BiO⁺And CO₃ ^2-The ions are dissociated into the solution (reaction formula (5)). BiO⁺And CO₃ ^2-Reaction to produce Bi₂O₂CO₃Crystal nucleus is adsorbed on Ag/g-C₃N₄Surface formation of Ag/g-C₃N₄·Bi₂O₂CO₃(reaction formula (6)). Ag and BiO with prolonged reaction time⁺And CO₃ ^2-Ions are continuously generated, Ag is deposited on g-C through a dissolution-recrystallization process₃N₄Surface, BiO⁺And CO₃ ^2-Ion direction of Bi₂O₂CO₃Crystal nucleus migration and Bi induction₂O₂CO₃And (5) growing crystals. Finally obtain Ag/g-C₃N₄/Bi₂O₂CO₃A heterojunction photocatalyst (reaction formula (7)).

AgNO₃→Ag⁺+NO₃ ^-(1)

Ag⁺+gC₃N₄→Ag⁺·gC₃N₄(2)

CH₃CH₂OH+NaBiO₃+H⁺→CH₃CH₂OBiO₂+H₂O+Na⁺(3)

Ag⁺·gC₃N₄+CH₃CH₂OBiO₂→Ag⁺·gC₃N₄·CH₃CH₂OBiO₂(4)

Ag⁺·gC₃N₄·CH₃CH₂OBiO₂+O₂→Ag/gC₃N₄+BiO⁺+CO₃ ^2-(5)

Ag/gC₃N₄+2BiO⁺+CO₃ ^2-→Ag/gC₃N₄·Bi₂O₂CO₃(6)

Ag/gC₃N₄·Bi₂O₂CO₃+Ag+BiO⁺+CO₃ ^2-→Ag/gC₃N₄/Bi₂O₂CO₃(7)

Fig. 2 is an ultraviolet-visible diffuse reflectance spectrum of the catalyst powder prepared in the present invention, in which a-d are ultraviolet-visible diffuse reflectance spectra of the powders prepared in comparative examples 1 to 4, respectively, and e-g are ultraviolet-visible diffuse reflectance spectra of the powders prepared in examples 1 to 3, respectively. g-C₃N₄And Bi₂O₂CO₃Only shows strong absorption in the visible range, with light absorption edges around 440 and 420nm, respectively. Bi₂O₂CO₃The presence of mesooxygen vacancies makes the light absorption in the range of 420-800nm slightly higher than that of g-C₃N₄. Ag/g-C due to the LSPR effect of noble metal Ag₃N₄And Ag/Bi₂O₂CO₃The light absorption of the light is obviously stronger than that of g-C₃N₄And Bi₂O₂CO₃。Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst retains Ag/g-C₃N₄The wide spectral absorption in the range of 200-800nm is realized.

FIG. 3 shows the concentration of the catalyst powder prepared by the present invention under simulated solar radiation is 20 mg.L^-1The degradation curve of the tetracycline is shown in FIG. 4, the corresponding apparent rate constant is shown in FIG. 4, a 500W xenon lamp is a simulated sunlight source, in the graph, a-d are the degradation curve and the apparent rate constant of the powder prepared in comparative examples 1-4 to the tetracycline, respectively, and e-g are the degradation curve and the apparent rate constant of the powder prepared in examples 1-3 to the tetracycline, respectively. As can be seen from the figure, Ag/g-C₃N₄/Bi₂O₂CO₃Heterojunction in the simulation of sunThe degradation activity of the tetracycline under the light irradiation is obviously higher than that of g-C₃N₄、Bi₂O₂CO₃、Ag/g-C₃N₄And Ag/Bi₂O₂CO₃. Ag/g-C prepared in example 2 after 120min of simulated solar irradiation₃N₄/Bi₂O₂CO₃The degradation efficiency of the heterojunction on the tetracycline can reach 90.54%, and the corresponding apparent rate constant is 0.0193min^-1。

FIG. 5 shows the concentration of the catalyst powder prepared by the present invention under simulated solar radiation is 10 mg.L^-1The degradation curve of ciprofloxacin is shown in figure 6, a 500W xenon lamp is a simulated sunlight source, a-d in the graph are respectively the degradation curve and the apparent rate constant of the powder prepared in comparative examples 1-4 to ciprofloxacin, and e-g are respectively the degradation curve and the apparent rate constant of the powder prepared in examples 1-3 to ciprofloxacin. As can be seen from the figure, Ag/g-C₃N₄/Bi₂O₂CO₃The degradation activity of the heterojunction to tetracycline under the simulated sunlight irradiation is obviously higher than that of g-C₃N₄、Bi₂O₂CO₃、Ag/g-C₃N₄And Ag/Bi₂O₂CO₃. Ag/g-C prepared in example 2 after 40min of simulated sunlight irradiation₃N₄/Bi₂O₂CO₃The degradation efficiency of the heterojunction on the tetracycline can reach 93.73%, and the corresponding apparent rate constant is 0.0646min^-1。

FIGS. 7 and 8 are graphs showing the degradation curves of the catalyst powder prepared according to the present invention under near infrared light irradiation, the near infrared light is realized by a 500W xenon lamp and an 800nm optical filter, a-d are graphs showing the degradation curves of the powder prepared according to comparative examples 1 to 4, and e-g are graphs showing the degradation curves of the powder prepared according to examples 1 to 3. As can be seen from the figure, Ag/g-C₃N₄/Bi₂O₂CO₃The degradation activity of the heterojunction to tetracycline and ciprofloxacin under near infrared light irradiation is obviously higher than that of g-C₃N₄、Bi₂O₂CO₃、Ag/g-C₃N₄And Ag/Bi₂O₂CO₃. Ag/g-C prepared in example 2 after 360min of near-infrared irradiation₃N₄/Bi₂O₂CO₃The degradation efficiency of the heterojunction on the tetracycline is 84.87%; Ag/g-C prepared in example 2 after 180min of near-infrared irradiation₃N₄/Bi₂O₂CO₃The degradation efficiency of the heterojunction on the ciprofloxacin is 86.33%.

FIGS. 9 and 10 are Ag/g-C prepared in example 2, respectively₃N₄/Bi₂O₂CO₃The heterojunction degrades the cycle experiment result of tetracycline and ciprofloxacin under the simulated sunlight irradiation. Ag/g-C prepared in example 2 after 120min of simulated solar irradiation during the first to fifth cycles₃N₄/Bi₂O₂CO₃The degradation efficiency of the heterojunction on tetracycline is 90.54%, 89.20%, 86.01%, 87.58% and 86.61% respectively; Ag/g-C prepared in example 2 after 40min of simulated solar irradiation during the first to fifth cycles₃N₄/Bi₂O₂CO₃The degradation efficiency of the heterojunction on the ciprofloxacin is 93.73%, 91.20%, 89.67%, 88.45% and 87.34% respectively. Experimental results prove that the Ag/g-C prepared by the invention₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst has good cycle stability.

The invention is based on the discovery that g-C₃N₄And Bi₂O₂CO₃The Z-type heterojunction is formed by compounding to improve the oxidation reduction capability of photo-generated electrons and holes, and the generation and separation of photo-generated carriers are accelerated while the full solar spectrum absorption is realized by the LSPR effect of noble metal Ag, the formation of an interface Schottky barrier and the near field enhancement effect, so that the photo-generated charge separation efficiency is improved. The method has simple process and simple operation, realizes full solar spectrum absorption by LSPR effect of noble metal Ag, improves the utilization rate of solar energy, and prepares Ag/g-C₃N₄/Bi₂O₂CO₃The heterojunction photocatalyst can degrade antibiotics such as tetracycline and ciprofloxacin under the irradiation of simulated sunlight and near infrared light, and has photocatalytic performance similar to that of g-C₃N₄、Bi₂O₂CO₂、Ag/Bi₂O₂CO₃And Ag/g-C₃N₄Compared with the prior art, the method is remarkably improved, and can be used for environmental purification with full-spectrum response.

The above description is only one embodiment of the present invention, and not all or only one embodiment, and any equivalent alterations to the technical solutions of the present invention, which are made by those skilled in the art through reading the present specification, are covered by the claims of the present invention.