A tellurium / carbon nitride p-n heterojunction photocatalyst and a preparation method and application thereof
By preparing tellurium/carbon nitride pn heterojunction photocatalysts, the carrier recombination problem was solved, and efficient photocatalytic carbon dioxide reduction was achieved with high yield and good stability, making it suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI UNIV
- Filing Date
- 2024-03-13
- Publication Date
- 2026-06-23
AI Technical Summary
Existing photocatalysts, such as graphitic carbon nitride, suffer from carrier recombination problems, which limit photon utilization efficiency and make it difficult to efficiently photocatalyze carbon dioxide reduction.
Tellurium/carbon nitride pn heterojunction photocatalysts were prepared by a one-pot hydrothermal method and ammonia-assisted calcination, forming a built-in electric field to promote the separation of photogenerated electron-hole pairs and improve carrier separation and migration efficiency.
It achieves highly efficient photocatalytic reduction of carbon dioxide with a yield of up to 92 μmol/g/h and a product selectivity of nearly 100%. It also exhibits good cycle stability and economic benefits, making it suitable for industrial applications.
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Figure CN118122362B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photocatalytic carbon dioxide reduction technology, and in particular to a tellurium / carbon nitride pn heterojunction photocatalyst, its preparation method, and its application. Background Technology
[0002] The ever-increasing carbon dioxide emissions have triggered a series of environmental and social problems. Photocatalysis, as a green pathway for converting carbon dioxide using solar energy, has received widespread attention. In recent years, numerous high-performance photocatalysts have emerged, demonstrating excellent results in the photoreduction of carbon dioxide. Among them, graphitic carbon nitride, with its excellent chemical stability and cost-effectiveness, is considered one of the most promising photocatalysts for industrial-scale application. However, carbon nitride alone suffers from carrier recombination, which greatly limits its photon utilization efficiency.
[0003] Therefore, it is particularly important to explore effective strategies to improve the separation efficiency of photogenerated electron-hole pairs. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a tellurium / carbon nitride pn heterojunction photocatalyst, its preparation method and application. The tellurium / carbon nitride pn heterojunction composite photocatalyst is prepared by a one-pot hydrothermal method and ammonia-assisted calcination. The preparation method is simple, the raw materials are inexpensive and readily available, and it achieves efficient carbon dioxide photocatalytic reduction without the addition of any sacrificial agents, showing good application potential in the field of photocatalytic carbon dioxide to carbon monoxide conversion.
[0005] The objective of this invention can be achieved through the following technical solutions:
[0006] One of the technical solutions of the present invention is to provide a method for preparing a tellurium / carbon nitride pn heterojunction photocatalyst, characterized by comprising the following steps:
[0007] S1. Disperse telluride compounds and carbon and nitrogen compounds in deionized water, and mix thoroughly by ultrasonication to obtain a homogeneous precursor solution;
[0008] S2. The homogeneous precursor solution obtained in step S1 is subjected to a hydrothermal reaction, and after cooling, centrifugation, washing and drying, a supramolecular intermediate is obtained.
[0009] S3. The supramolecular intermediate obtained in step S2 is calcined with gas assistance and then ground to obtain tellurium / carbon nitride pn heterojunction composite photocatalyst powder.
[0010] Further, in step S1, the tellurium compound includes at least one of telluric acid, sodium tellurite, sodium tellurate, potassium ammonium tellurate, or ammonium trichloro[1,2-ethylene glycol-O,O]-tellurate; the carbon-nitrogen compound includes melamine, urea, dicyandiamine, or cyanuric acid.
[0011] Further, in step S1, the mass ratio of the tellurium compound to the carbon-nitrogen compound is (0.2-0.8):1.
[0012] Further, in step S1, the concentration of tellurium compounds in the homogeneous precursor solution is 4–16 mg / mL.
[0013] Furthermore, in step S1, the ultrasonic mixing time is 0.5 to 2 hours.
[0014] Furthermore, in step S2, the temperature of the hydrothermal reaction is 120–200°C, and the reaction time is 6–24 hours.
[0015] Furthermore, in step S2, the temperature reached by the cooling is room temperature.
[0016] Furthermore, in step S2, the centrifugation speed is 3000-8000 r / min, and the centrifugation time is 4-10 min.
[0017] Furthermore, in step S2, the solvent used for washing is deionized water.
[0018] Furthermore, in step S2, the drying temperature is 40–80°C, and the drying time is 8–24 hours.
[0019] Furthermore, in step S3, the gases used for auxiliary calcination include ammonia (NH3) and ammonia-nitrogen mixture (NH3 / N2).
[0020] Furthermore, the gas used for auxiliary calcination is NH3 / N2 gas containing 1% to 10%, preferably NH3 / N2 gas containing 5%.
[0021] Furthermore, in step S3, the calcination heating rate is 2-5℃ / min, the stable temperature is 400-650℃, and the holding time is 3-6h.
[0022] The second technical solution of the present invention is to provide a tellurium / carbon nitride pn heterojunction photocatalyst, which is prepared by the above-mentioned preparation method.
[0023] The third technical solution of the present invention is to provide an application of a tellurium / carbon nitride pn heterojunction photocatalyst in the field of photocatalytic carbon dioxide reduction.
[0024] Further, the tellurium / carbon nitride pn heterojunction photocatalyst is dispersed in deionized water, ultrasonicated to obtain a homogeneous solution, uniformly coated onto a carrier, dried, and then placed into a photocatalytic reaction cell. Deionized water is added to the bottom of the cell, and under room temperature and sealed conditions, nitrogen gas is introduced to purge the air from the photocatalytic reaction cell, followed by carbon dioxide. The light source is then turned on to carry out the reaction, reducing carbon dioxide to carbon monoxide.
[0025] Furthermore, the concentration of the homogenized solution is 0.6–2 mg / mL.
[0026] Furthermore, the carrier is a circular glass plate with a diameter of 3 to 10 cm.
[0027] Furthermore, the drying temperature is 40–80°C, and the time is 2–12 hours.
[0028] Furthermore, the amount of deionized water added to the bottom of the pool is 1 to 10 mL.
[0029] Furthermore, the nitrogen gas is introduced for 10 to 30 minutes, and the carbon dioxide gas is introduced for 10 to 30 minutes.
[0030] Furthermore, the temperature is controlled by circulating cooling water outside the photocatalytic reaction tank to keep it at room temperature, with the temperature of the circulating cooling water set at 10–30°C.
[0031] Furthermore, the type of light source is a 300W deuterium lamp.
[0032] Heterogeneous structure construction has become an effective strategy for improving photocatalytic performance. This method promotes charge separation in catalysts by establishing suitable band structures and regulating electron transport pathways. Guided by this concept, researchers have combined suitable semiconductor catalysts with carbon nitride to form a promising heterojunction photocatalyst. Tellurium, as a typical metalloid element, possesses excellent metallic conductivity and the ability to be tuned without metal elements. Furthermore, tellurium exhibits strong carbon dioxide adsorption and high carrier mobility. Benefiting from these properties, tellurium displays p-type semiconductor characteristics and can be combined with n-type semiconductor carbon nitride to form pn heterojunctions. Compared to conventional type II heterojunctions, the built-in electric field formed by the pn heterojunction can further accelerate the migration of photogenerated electron-hole pairs, improving carrier separation efficiency. In pn heterojunction research, tellurium / carbon nitride pn heterojunction photocatalysts show great potential for efficient photocatalytic carbon dioxide reduction. It is worth noting that there are currently no reports on the efficient photocatalytic carbon dioxide reduction of tellurium / carbon nitride pn heterojunction photocatalysts. This provides new ideas and directions for research in related fields.
[0033] Compared with the prior art, the present invention has the following advantages:
[0034] (1) The present invention prepares a tellurium / carbon nitride pn heterojunction photocatalyst. The raw materials for its preparation are readily available, the process is simple, low-cost, high-efficiency and easy to control, no organic solvent is required, it is suitable for large-scale production and is expected to move towards industrial application.
[0035] (2) This invention provides a method for preparing a tellurium / carbon nitride pn heterojunction photocatalyst. Ammonia decomposes into hydrogen and nitrogen during calcination, which makes the catalyst surface present a rich pore structure, enhances its adsorption capacity for carbon dioxide, and is beneficial to the reduction of carbon dioxide.
[0036] (3) Thanks to the built-in electric field of the pn junction, the tellurium / carbon nitride pn heterojunction photocatalyst prepared in this invention achieves accelerated migration of photogenerated electrons from the tellurium conduction band to the carbon nitride conduction band, and accelerated migration of photogenerated holes from the carbon nitride valence band to the tellurium valence band, which suppresses carrier recombination, improves charge separation and migration efficiency, and thus enhances photocatalytic activity.
[0037] (4) The tellurium / carbon nitride pn heterojunction composite material prepared in this invention, as a photocatalytic carbon dioxide reduction catalyst, exhibits excellent catalytic activity and selectivity without the addition of any sacrificial agent. The carbon monoxide yield is as high as 92 μmol / g / h, the product selectivity is close to 100%, and it has good cycling stability, showing broad prospects for practical applications. In this invention, the only solvent used in the sample synthesis process is deionized water, eliminating the need for commonly used organic solvents such as ethanol, acetonitrile, DMF, acetone, and toluene. The photocatalytic performance is tested using a gas-solid phase method, which eliminates the need for sacrificial agents. Triethanolamine, a commonly used sacrificial agent in photocatalytic performance testing, consumes holes to promote electron reduction reactions. The gas-solid phase method does not require sacrificial agents, resulting in performance results that are closer to the actual performance of the sample. This invention eliminates the need for organic solvents and sacrificial agents, making the sample synthesis and performance testing processes more environmentally friendly and economical. Attached Figure Description
[0038] Figure 1 The image shown is a transmission electron microscope (TEM) image of the tellurium / carbon nitride pn heterojunction photocatalyst shown in Example 1. The inset is a particle size distribution diagram.
[0039] Figure 2 X-ray diffraction pattern of the tellurium / carbon nitride pn heterojunction photocatalyst shown in Example 1 compared with the Te standard card;
[0040] Figure 3 The X-ray photoelectron spectrum of the tellurium / carbon nitride pn heterojunction photocatalyst shown in Example 1 is shown below.
[0041] Figure 4 The following are the Mott Schottky curves for each material, where (a) is CN-NH3 in Comparative Example 2 and Te in Comparative Example 4, and (b) is Te / CN-NH3 in Example 1;
[0042] Figure 5 The accompanying diagram shows the carbon dioxide temperature-programmed decarbonylation of Te / CN-NH3, Te / CN-N2, CN-NH3, and CN-N2 as shown in Example 1 and Comparative Examples 1-3;
[0043] Figure 6 The graph shows the yield of carbon dioxide photocatalytic reduction using the tellurium / carbon nitride pn heterojunction photocatalyst shown in Example 1.
[0044] Figure 7 The graphs show the photocatalytic reduction yields and selectivity of carbon dioxide for Te / CN-NH3, Te / CN-N2, CN-NH3, and CN-N2 as shown in Examples 1 and Comparative Examples 1-3.
[0045] Figure 8 The diagram shows the cycle stability of the photocatalytic reduction of carbon dioxide by the tellurium / carbon nitride pn heterojunction as shown in Example 1. Detailed Implementation
[0046] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.
[0047] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.
[0048] In the following embodiments, the light source is a 300W deuterium lamp with a 420nm cutoff filter, model Perfectlight, PLS-SXE300.
[0049] Example 1
[0050] 300 mg of telluric acid and 1000 mg of melamine were weighed and dispersed in 50 mL of deionized water, and ultrasonically mixed for 1 h to obtain a homogeneous precursor solution. The mixed solution was subjected to hydrothermal reaction at 180 °C for 6 h. After the reaction was completed, the solution was transferred to a 50 mL centrifuge tube and centrifuged at 5000 r / min for 5 min. The supernatant was then discarded, and deionized water was added. The bottom material was ultrasonically dispersed for 1 min, and centrifuged under the same conditions twice. The solid obtained by centrifugation was dried at 60 °C for 12 h to obtain a supramolecular intermediate.
[0051] The supramolecular intermediate was transferred to a covered crucible and placed in a tube furnace. A gas containing 5% NH3 / N2 was introduced, and the heating rate was set at 5℃ / min. The stabilization temperature was 480℃, and the holding time was 5 hours. After calcination and natural cooling to room temperature, the crucible was removed, and the material was thoroughly ground to obtain a tellurium / carbon nitride pn heterojunction photocatalyst, named Te / CN-NH3.
[0052] Weigh 5 mg of tellurium / carbon nitride pn heterojunction photocatalyst and disperse it in 5 mL of deionized water. Sonicate for 10 min to obtain a homogeneous solution. Evenly drop-coat the homogeneous solution onto a 5 cm diameter circular glass slide and dry it in a vacuum oven at 60 °C for 6 h. Place the catalyst-coated glass slide into a photocatalytic reaction cell, add 10 mL of deionized water to the bottom, and seal. Purge the reaction cell with nitrogen gas for 20 min to remove air, then purge with carbon dioxide gas for 20 min. Circulate cooling water outside the reaction cell to maintain a constant temperature of 25 °C. Turn on the light source to initiate the reaction. Connect a gas chromatograph to the gas outlet of the reaction cell to detect gaseous products. Samples are taken from the cell every 1 h for analysis. The product formation rate is calculated by measuring the concentration of gaseous products at different time points.
[0053] Example 2
[0054] The steps are mostly the same as in Example 1, except that the amount of telluric acid added is adjusted to 200 mg.
[0055] Example 3
[0056] The steps are mostly the same as in Example 1, except that the amount of telluric acid added is adjusted to 400 mg.
[0057] Example 4
[0058] The steps are mostly the same as in Example 1, except that the amount of telluric acid added is adjusted to 600 mg.
[0059] Example 5
[0060] The steps are mostly the same as in Example 1, except that the amount of telluric acid added is adjusted to 800 mg.
[0061] Example 6
[0062] The steps are mostly the same as in Example 1, except that the telluric acid is replaced with sodium tellurite.
[0063] Example 7
[0064] The steps are mostly the same as in Example 1, except that the melamine is replaced with urea.
[0065] Example 8
[0066] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 400°C.
[0067] Example 9
[0068] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 450°C.
[0069] Example 10
[0070] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 500°C.
[0071] Example 11
[0072] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 520°C.
[0073] Example 12
[0074] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 550°C.
[0075] Example 13
[0076] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 580°C.
[0077] Example 14
[0078] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 600°C.
[0079] Example 15
[0080] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 630°C.
[0081] Example 16
[0082] The steps are mostly the same as in Example 1, except that the calcination stabilization temperature is adjusted to 650°C.
[0083] Example 17
[0084] The steps are mostly the same as in Example 1, except that the temperature of the hydrothermal reaction is adjusted to 160°C.
[0085] Example 18
[0086] The steps are mostly the same as in Example 1, except that the temperature of the hydrothermal reaction is adjusted to 140°C.
[0087] Example 19
[0088] The steps are mostly the same as in Example 1, except that the temperature of the hydrothermal reaction is adjusted to 120°C.
[0089] Example 20
[0090] The steps are mostly the same as in Example 1, except that the temperature of the hydrothermal reaction is adjusted to 200°C.
[0091] Example 21
[0092] The steps are mostly the same as in Example 1, except that the tellurium / carbon nitride pn heterojunction photocatalyst used is adjusted to 5 mg.
[0093] Example 22
[0094] The steps are mostly the same as in Example 1, except that the tellurium / carbon nitride pn heterojunction photocatalyst used is adjusted to 10 mg.
[0095] Comparative Example 1
[0096] 300 mg of telluric acid and 1000 mg of melamine were weighed and dispersed in 50 mL of deionized water, and ultrasonically mixed for 1 h to obtain a homogeneous precursor solution. The mixture was reacted at 180 °C for 6 h. After the reaction was completed, the solution was transferred to a 50 mL centrifuge tube and centrifuged at 5000 rpm for 5 min. The supernatant was then discarded, and deionized water was added. The bottom material was ultrasonically dispersed for 1 min, and the mixture was centrifuged under the same conditions twice. The solid obtained from centrifugation was dried at 60 °C for 12 h to obtain a supramolecular intermediate.
[0097] The supramolecular intermediate was transferred to a covered crucible, placed in a tube furnace, and N2 gas was introduced. The heating rate was set to 5℃ / min, the stabilization temperature to 480℃, and the isothermal time to 5h. After calcination was completed and the material was allowed to cool naturally to room temperature, the crucible was removed, and the calcined material was thoroughly ground to obtain a tellurium / carbon nitride pn heterojunction photocatalyst, named Te / CN-N2.
[0098] Comparative Example 2
[0099] 1000 mg of melamine was weighed and dispersed in 50 mL of deionized water, and ultrasonically mixed for 10 min to obtain a homogeneous precursor solution. The mixture was reacted at 180 °C for 6 h. After the reaction was completed, the solution was allowed to cool to room temperature and then transferred to a 50 mL centrifuge tube. The centrifuge was set to 5000 rpm and centrifuged for 5 min. The supernatant was then discarded, and deionized water was added. The bottom material was ultrasonically dispersed for 1 min, and the mixture was centrifuged again under the same conditions, repeating the process twice. The solid obtained by centrifugation was dried at 60 °C for 12 h to obtain a supramolecular intermediate.
[0100] The supramolecular intermediate was transferred to a covered crucible and placed in a tube furnace. A gas containing 5% NH3 / N2 was introduced, and the heating rate was set at 5℃ / min, the stabilization temperature at 480℃, and the holding time at that temperature was 5h. After calcination was completed and the material was allowed to cool naturally to room temperature, the crucible was removed, and the calcined material was thoroughly ground to obtain a carbon nitride photocatalyst, named CN-NH3.
[0101] Comparative Example 3
[0102] 1000 mg of melamine was weighed and dispersed in 50 mL of deionized water, and ultrasonically mixed for 10 min to obtain a homogeneous precursor solution. The mixture was reacted at 180 °C for 6 h. After the reaction was completed, the solution was allowed to cool to room temperature and then transferred to a 50 mL centrifuge tube. The centrifuge was set to 5000 rpm and centrifuged for 5 min. The supernatant was then discarded, and deionized water was added. The bottom material was ultrasonically dispersed for 1 min, and the mixture was centrifuged again under the same conditions, repeating the process twice. The solid obtained by centrifugation was dried at 60 °C for 12 h to obtain a supramolecular intermediate.
[0103] The supramolecular intermediate was transferred to a covered crucible, placed in a tube furnace, and N2 gas was introduced. The heating rate was set to 5℃ / min, the stabilization temperature to 480℃, and the holding time to 5h. After calcination was completed and the material was allowed to cool naturally to room temperature, the crucible was removed, and the calcined material was thoroughly ground to obtain carbon nitride photocatalyst, named CN-N2.
[0104] Comparative Example 4
[0105] 1000 mg of tellurium powder was weighed and placed in a crucible, which was then placed in a tube furnace and purged with 5% NH3 / N2 gas. The heating rate was set to 5 °C / min, the stable temperature to 480 °C, and the holding time to 5 h. After calcination was completed and the material was allowed to cool naturally to room temperature, the crucible was removed, and the calcined material was thoroughly ground to obtain Te nanoparticles.
[0106] The performance of Te / CN-NH3, Te / CN-N2, CN-NH3, CN-N2 and Te obtained in Example 1 and Comparative Examples 1 to 4 was tested and analyzed.
[0107] Transmission electron microscopy analysis was performed on the tellurium / carbon nitride pn heterojunction photocatalyst Te / CN-NH3 obtained in Example 1, as follows: Figure 1 As shown, the morphological characteristics of the composite material are clearly visible: tellurium nanoparticles are loaded onto carbon nitride nanosheets. These carbon nitride nanosheets have numerous pores on their surface, which are formed during the high-temperature calcination process when ammonia decomposes into nitrogen and hydrogen. The inset shows that the average particle size of the tellurium nanoparticles is 18 nm. Figure 2 X-ray diffraction analysis of Te / CN-NH3 in Example 1 is presented, and the results show that the peak positions of this tellurium / carbon nitride pn heterojunction photocatalyst are in perfect agreement with the standard card for tellurium. Figure 3 The X-ray photoelectron spectrum of Te / CN-NH3 obtained in Example 1 reveals the presence of C, N, O, and Te elements in the material. The C and N elements originate from the precursor melamine, the Te element from the precursor telluric acid, and the O element from the introduction of oxygen from water or air during the preparation process. Figure 1 , Figure 2 and Figure 3 This demonstrates the successful synthesis of tellurium / carbon nitride pn heterojunction photocatalysts.
[0108] The Te / CN-NH3 nanoparticles of Example 1, CN-NH3 of Comparative Example 2, and Te nanoparticles of Comparative Example 4 were subjected to Mott-Schottky tests, and their Mott-Schottky curves are shown below. Figure 4 As shown, Figure 4 As shown in (a), the slope of the Mott-Schottky curve for CN-NH3 is positive, indicating that carbon nitride is an n-type semiconductor. In contrast, the slope of the Mott-Schottky curve for Te nanoparticles is negative, indicating that tellurium nanoparticles are p-type semiconductors. Furthermore, as... Figure 4 As shown in (b), the Mott-Schottky curve of Te / CN-NH3 exhibits an inverted "V" shape, a significant characteristic of pn junction formation. Therefore, Figure 4 This strongly demonstrates the successful construction of pn heterojunctions in tellurium / carbon nitride composites.
[0109] In the carbon dioxide temperature-programmed desorption (CO2-TPD) test, the adsorption capacity of carbon dioxide by Te / CN-NH3, Te / CN-N2, CN-NH3, and CN-N2 obtained in Example 1 and Comparative Examples 1-3 was analyzed in detail, and the results are as follows: Figure 5As shown, compared to carbon nitride, the tellurium / carbon nitride pn heterojunction photocatalyst exhibits a stronger CO2-TPD signal, indicating that the introduction of tellurium significantly enhances the material's adsorption performance for carbon dioxide. Notably, the CO2-TPD signal of Te / CN-NH3 is stronger than that of Te / CN-N2, suggesting that calcination in an ammonia atmosphere generates more abundant alkaline sites on the catalyst surface, leading to more efficient carbon dioxide adsorption. Therefore, the superior chemisorption performance of Te / CN-NH3 significantly enhances the photocatalytic carbon dioxide reduction activity.
[0110] Figure 6 The graph shows the rate of carbon dioxide reduction by the tellurium / carbon nitride pn heterojunction photocatalyst (Te / CN-NH3) as shown in Example 1. As can be seen from the graph, the amount of carbon monoxide generated increases rapidly with time, while the amount of methane generated increases very slowly. Figure 7 Example 1, and Comparative Examples 1-3, show the photocatalytic reduction yields and selectivity of carbon dioxide for Te / CN-NH3, Te / CN-N2, CN-NH3, and CN-N2. Under conditions without any sacrificial agents, the carbon monoxide yield of Te / CN-NH3 reached as high as 92 μmol / g / h, with a product selectivity approaching 100%. This result indicates that the performance of the tellurium / carbon nitride pn heterojunction photocatalyst is superior to that of pure carbon nitride, further confirming that the construction of a pn heterojunction is beneficial for improving photocatalytic activity. Thanks to the built-in electric field in the pn junction, photogenerated electrons on the conduction band of tellurium nanoparticles migrate more rapidly to the conduction band of carbon nitride, while photogenerated holes on the valence band of carbon nitride migrate more rapidly to the valence band of tellurium. This phenomenon suppresses carrier recombination, improves charge separation and migration efficiency, thereby enhancing photocatalytic activity. Compared to Te / CN-N2, Te / CN-NH3 exhibits superior performance due to its abundant porosity and excellent carbon dioxide chemisorption properties, which expose more active sites and effectively capture and convert carbon dioxide.
[0111] Figure 8 The excellent photocatalytic reduction of carbon dioxide by the tellurium / carbon nitride pn heterojunction photocatalyst (Te / CN-NH3) shown in Example 1 was demonstrated in four consecutive reaction cycles. Figure 8 It can be seen that even after four cycles, Te / CN-NH3 still maintains highly efficient photocatalytic performance, which fully demonstrates the excellent stability of the tellurium / carbon nitride pn heterojunction. Combined with Figure 6 , Figure 7 and Figure 8 We can conclude that the tellurium / carbon nitride pn heterojunction proposed in this invention, as a novel visible light catalyst, possesses good stability, high selectivity, and high catalytic efficiency, demonstrating broad potential for practical applications.
[0112] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. The application of a tellurium / carbon nitride pn heterojunction photocatalyst in photocatalytic carbon dioxide reduction, characterized in that, The preparation method of the photocatalyst includes the following steps: S1. Disperse telluride compounds and carbon and nitrogen compounds in deionized water, and mix thoroughly by ultrasonication to obtain a homogeneous precursor solution; S2. The homogeneous precursor solution obtained in step S1 is subjected to a hydrothermal reaction, and after cooling, centrifugation, washing and drying, a supramolecular intermediate is obtained. S3. The supramolecular intermediate obtained in step S2 is calcined with gas assistance and then ground to obtain tellurium / carbon nitride pn heterojunction composite photocatalyst powder; the gas used for calcination assistance includes ammonia or ammonia-nitrogen mixture.
2. The application according to claim 1, characterized in that, In step S1, the tellurium compound includes at least one of telluric acid, sodium tellurite, sodium tellurate, potassium tellurite, or ammonium tellurate. The carbon and nitrogen compounds mentioned include melamine, urea, dicyandiamine, or cyanuric acid.
3. The application according to claim 1, characterized in that, In step S1, the mass ratio of the tellurium compound to the carbon and nitrogen compound is (0.2~0.8):
1.
4. The application according to claim 1, characterized in that, In step S1, the concentration of tellurium compounds in the homogeneous precursor solution is 4~16 mg / mL.
5. The application according to claim 1, characterized in that, In step S2, the temperature of the hydrothermal reaction is 120~200℃, and the reaction time is 6~24h.
6. The application according to claim 1, characterized in that, In step S3, the calcination heating rate is 2~5℃ / min, the stable temperature is 400~650℃, and the holding time is 3~6h.