Z-type photocatalytic material based on carbon intermediate energy level as well as preparation method and application of Z-type photocatalytic material

Abstract

The invention belongs to the technical field of photocatalysts, and particularly discloses a Z-type photocatalytic material based on a carbon intermediate energy level and a preparation method and application thereof.The preparation method comprises the following steps that LCN is prepared, Chinese redbud tree dead leaf powder and urea are added into an agate mortar to be fully mixed, the mixture is transferred into a crucible and then placed in a muffle furnace to be calcined, and LCN is obtained; collecting a sample and grinding to obtain LCN; the preparation method comprises the following steps: preparing LCN / BiOI, adding ethylene glycol and LCN into a beaker, uniformly stirring, then adding bismuth nitrate, adding a bismuth oxyiodide solution, stirring, and drying to obtain the LCN / BiOI. According to the Z-type photocatalytic material based on the carbon intermediate energy level and the preparation method and application of the Z-type photocatalytic material based on the carbon intermediate energy level, an in-situ deposition method is adopted for compounding LCN and BiOI to prepare a Z-type photocatalyst LCN / BiOI, and it is proved that the carbon intermediate energy level effectively induces ordered transfer of electrons in a Z-type heterojunction, so that the removal efficiency of pollutants BPA is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of road snow removal equipment, in particular to a road and bridge snow removal device. Background Art

[0002] Bisphenol A (BPA), a prominent endocrine disruptor, mimics hormones in the human body, disrupting the normal functioning of the endocrine system. Long-term exposure can lead to a range of health problems, including reproductive system abnormalities, cardiovascular disease, obesity, diabetes, and certain types of cancer. Widely used in the production of polycarbonate plastics and epoxy resins, BPA is closely associated with daily life. While photocatalytic technology has attracted considerable attention for its environmental and secondary pollution-free advantages, its industrialization has been hampered by issues such as low separation and migration rates of photogenerated charge carriers and high recombination rates.

[0003] In the modification strategy of photocatalytic technology, the construction of Z-type heterojunction can ensure the electron (e - ) and holes (h + ) and promotes the directional migration of carriers in semiconductor materials, thereby improving the photocatalytic redox ability. However, due to the lack of intermediates between direct semiconductors, the internal carrier separation lacks sufficient driving force, which makes disordered transfer easy to occur. In previous studies by the current research group, it was found that by doping benzene ring molecules into the g-C3N4 skeleton, the built-in electric field causes the energy band to bend, thereby inducing orderly carrier transfer in the heterojunction; and after using carbon sources to dope into the g-C3N4 skeleton, impurity energy levels are formed near the conduction band of carbon nitride (LCN), which improves the photocatalytic activity by inducing electron transfer. Therefore, the doping of carbon elements is expected to control Z-type electron transfer and induce orderly charge transfer.

[0004] This invention enhances the photocatalytic performance of Z-type materials by preparing the catalyst in a step-by-step manner and systematically regulating the orderly transfer of charge carriers within the material. Using a thermal copolymerization method, dead leaves of Bauhinia chinensis were doped as a carbon source into the g-C3N4 framework to form intermediate energy levels. When applied to the degradation of the pollutant BPA, the enhanced activity was not significant. Subsequently, LCN and BiOI were composited using an in-situ deposition method to prepare the Z-type photocatalyst LCN / BiOI. Under visible light irradiation, BPA was completely degraded in just 60 minutes, demonstrating that the carbon intermediate energy levels effectively induce the orderly transfer of electrons within the Z-type heterojunction, thereby significantly improving the removal efficiency of the BPA pollutant. Summary of the Invention

[0005] The present invention aims to provide a Z-type photocatalytic material based on carbon intermediate energy levels, its preparation method, and application. By preparing the catalyst in a step-by-step manner, the orderly charge carrier transfer within the material is systematically controlled. The Z-type photocatalyst LCN / BiOI was prepared by combining LCN and BiOI using an in-situ deposition method. Under visible light irradiation, BPA was completely degraded in just 60 minutes, demonstrating that the carbon intermediate energy levels effectively induce orderly electron transfer within the Z-type heterojunction, significantly improving the removal efficiency of the pollutant BPA.

[0006] To achieve the above objectives, the present invention provides a method for preparing a Z-type photocatalytic material based on carbon intermediate energy levels, comprising the following steps: Step 1, preparation of LCN, collecting dried redbud tree leaves and grinding them into powder, adding the redbud tree leaf powder and urea into an agate mortar and mixing thoroughly, transferring the mixture into a crucible and calcining it in a muffle furnace, after the calcination is completed and the furnace temperature drops to room temperature, collecting the sample and grinding it to obtain LCN; Step 2, preparation of LCN / BiOI, ethylene glycol and LCN are added to a beaker and stirred evenly, followed by the addition of bismuth nitrate, stirring evenly, and then adding bismuth oxyiodide solution and continuing to stir for 30 minutes. The solution is then transferred to a Teflon-lined container and placed in a stainless steel autoclave. The mixture is placed in a forced air drying oven at 160°C for 45 minutes and then cooled to room temperature. The product is washed with water and ethanol and dried to obtain LCN / BiOI.

[0007] Preferably, in step 1, the calcination conditions are as follows: heating from room temperature to 80°C and maintaining for 1 hour, then heating to 550°C and maintaining for 2 hours, and the heating rate during the calcination process is 5°C / min.

[0008] Preferably, in step 2, the amount of ethylene glycol added is 20 mL.

[0009] Preferably, in step 2, the amount of bismuth nitrate added is 17.4, 22.2, or 50 mg.

[0010] Preferably, in step 2, the molar mass of bismuth iodide is the same as that of bismuth nitrate.

[0011] The present invention also provides a Z-type photocatalytic material based on carbon intermediate energy levels, which is prepared according to a preparation method of the Z-type photocatalytic material based on carbon intermediate energy levels.

[0012] The present invention also provides the application of a Z-type photocatalytic material based on carbon intermediate energy levels, which is applied to removing bisphenol A.

[0013] The advantages and beneficial effects of the present invention using the above-mentioned Z-type photocatalytic material based on carbon intermediate energy level and its preparation method and application are: 1. This invention uses urea and dead leaves of Bauhinia chinensis as precursors to produce LCN through thermal copolymerization. LCN is then combined with BiOI through in-situ deposition to produce LCN / BiOI. This product, applied to the removal of the pollutant BPA, achieves a 100% degradation rate of 10 ppm BPA within 60 minutes.

[0014] 2. The carbon intermediate energy level acts as an inductive force to drive Z-type electron transport and guide the orderly transfer of electrons, further helping the photogenerated carriers to transport in an orderly manner along the Z-shape, promoting the migration and separation of carriers and reducing recombination, thereby enhancing the photocatalytic activity of the LCN / BiOI system.

[0015] 3. The photocatalytic material of the present invention provides a certain idea for constructing an efficient and stable Z-type composite photocatalyst with a strong driving force to promote orderly carrier transfer.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Spectra of samples CN and LCN of the present invention, wherein a is an X-ray diffraction spectrum, b is a Fourier transform infrared spectrum, c is an electron paramagnetic resonance spectrum, and d is a transient fluorescence spectrum; Figure 2 : The energy band structures of samples CN and LCN of the present invention are shown in FIG. a, wherein a is the ultraviolet-visible diffuse reflectance spectrum of CN and LCN, b is the relationship curve of CN and LCN after conversion using the Kubelka-Munk function and energy, c is the valence band spectrum of CN measured by an X-ray electron spectrometer, d is the valence band spectrum of LCN measured by an X-ray electron spectrometer, and e is the energy band structure of CN and LCN; Figure 3 The X-ray diffraction patterns and Fourier transform infrared spectra of the samples BiOI, CN / BiOI and LCN / BiOI of the present invention are shown in Figure 1, where a is the X-ray diffraction pattern and b is the Fourier transform infrared spectra. Figure 4 These are the full element spectrum and high-resolution spectrum of the LCN / BiOI sample of the present invention, where a is the full spectrum, b is the high-resolution Bi4f spectrum, c is the high-resolution I3d spectrum, d is the high-resolution O1s spectrum, e is the high-resolution N1s spectrum, and f is the high-resolution C1S spectrum; Figure 5 Spectra of the samples BiOI and LCN / BiOI of the present invention, wherein a is the SEM spectrum of the sample BiOI, b is the TEM spectrum of LCN / BiOI, and c is the EDS element distribution spectrum of LCN / BiOI; Figure 6Figure 1 is a test chart of the degradation of BPA by samples CN, LCN, CN / BiOI, and LCN / BiOI under visible light. Figure a shows the degradation of BPA by samples CN, LCN, CN / BiOI, and LCN / BiOI under visible light, and figure b shows the photocatalytic activity of LCN / BiOI under five cycles. Figure 7 Spectra of the samples BiOI, CN / BiOI, and LCN / BiOI of the present invention, wherein a is the UV-visible diffuse reflectance spectrum, b is the electron paramagnetic resonance spectrum, c is the transient fluorescence spectrum, d is the transient photocurrent spectrum IT, and e is the electrochemical impedance spectroscopy EIS; Figure 8 The spectrum of the sample LCN / BiOI of the present invention, wherein a is the superoxide radical EPR spectrum, b is the hydroxyl radical EPR spectrum, and c is the radical capture spectrum; Figure 9 Figure 3 is the energy band structure of the BiOI sample of the present invention and the mechanism diagram of photocatalytic degradation of the antibiotic BPA, where a is the relationship curve with energy after conversion using the Kubelka-Munk function, b is the valence band spectrum tested by the X-ray electron spectrometer, and c is the mechanism diagram of photocatalytic degradation of the antibiotic BPA. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0020] Unless otherwise defined, the reagents, equipment and other materials used in the present invention are all commercially available.

[0021] Example 1 The preparation method of the Z-type photocatalytic material based on the carbon intermediate energy level comprises the following steps: Step 1: Preparation of LCN.

[0022] Dried leaves from the redbud tree were collected and ground into a powder. An appropriate amount of leaf powder and urea were poured into an agate mortar and pestle, thoroughly mixed, and transferred to a crucible for calcination in a muffle furnace. The calcination conditions were as follows: first, the temperature was raised from room temperature to 80°C and held for 1 hour, then to 550°C and held for 2 hours, with a heating rate of 5°C / min. After calcination, the furnace temperature was allowed to cool to room temperature, and the samples were collected and ground. They were designated LCN-1, LCN-2, and LCN-3, respectively. For control purposes, pure g-C3N4 was prepared using the same procedure without the addition of redbud leaves and designated CN.

[0023] Step 2: Preparation of LCN / BiOI and CN / BiOI.

[0024] To a beaker, add 20 mL of ethylene glycol and an appropriate amount of LCN and stir until uniform. Then, add 17.4, 22.2, and 50 mg of bismuth nitrate, respectively. After stirring, add an equimolar mass of bismuth oxyiodide (BiOI) solution and continue stirring for 30 minutes. The solution is then transferred to a Teflon-lined container and placed in a stainless steel autoclave. The autoclave is then placed in a forced-air drying oven at 160°C for 45 minutes before cooling to room temperature. The products are washed with water and ethanol multiple times, dried, and collected and named LCN / BiOI-1, LCN / BiOI-2, and LCN / BiOI-3.

[0025] Using the same method and dosage as described above, CN was added in an amount equivalent to LCN to prepare composite catalysts named CN / BiOI-1, CN / BiOI-2, and CN / BiOI-3. The mass ratios of BiOI to g-C3N4 were 8%, 10%, and 20%, respectively. Furthermore, as a control, an orange BiOI was prepared using the same preparation process without the addition of CN or LCN.

[0026] 1. Confirm that the carbon source is doped into the g-C3N4 framework.

[0027] In order to confirm that the carbon source was successfully doped into the g-C3N4 skeleton, the materials LCN and CN were subjected to characterization tests such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), electron paramagnetic resonance spectroscopy (EPR), and fluorescence spectroscopy (PL). Figure 1 Figure a is an XRD spectrum, showing the diffraction peak of samples CN and LCN at 27.6°. This characteristic peak is related to the inter-plane stacking of the (002) crystal planes of the aromatic sheets in the g-C3N4 layered structure. This shows that the orderly stacking of the aromatic layers in the structure of the sample LCN is well preserved, and the structure of carbon nitride is not destroyed after carbon source doping. FT-IR spectrum ( Figure 1 b) All samples were observed to have a peak at 808 cm -1 1230 to 1630 cm -1 and 3230cm -1 There are strong absorption peaks at 808cm -1 The peak at 1230 to 1630 cm-1 belongs to the breathing vibration of the heptazine unit in g-C3N4. -1 The peak in the range corresponds to the aromatic -CN heterocycle, located at 3230 cm -1 The broad peak corresponds to the NH / NH2 stretching caused by partial condensation.

[0028] The EPR method was used to detect the changes in the unpaired electron content of the catalyst before and after doping with carbon source. Figure 1 As shown in c, a single Lorentzian line centered at g = 2.0034 can be observed for all samples, which corresponds to the sp 2 The EPR signal of the unpaired electrons on the carbon atoms in sample LCN is significantly higher than that in sample CN. This is because the incorporation of the carbon source effectively promotes more significant electron delocalization on the conjugated rings of the heptazine, increasing the carrier density. Under visible light irradiation, the EPR signal intensity of all samples increases, but the stronger EPR signal of LCN indicates that LCN is more easily excited by light and generates photogenerated carriers. Figure 1 Figure d is the PL spectrum obtained when the excitation wavelength is 325 nm. At 475 nm, it can be observed that both CN and LCN emit fluorescence emission peaks, but the emission peak of LCN is significantly weaker than that of CN, indicating that after modification, it exhibits a lower carrier recombination rate. This is attributed to the fact that carbon doping can greatly accelerate the charge migration within the conjugated skeleton of LCN.

[0029] In order to further explore the photocatalytic performance of the g-C3N4 skeleton after carbon source doping, the band structures of CN and LCN were measured using various characterization methods. Figure 2 Figure a shows UV-visible diffuse reflectance spectroscopy (DRS) testing of CN and LCN. The results reveal that LCN exhibits a blue shift in its light absorption edge relative to CN, demonstrating increased utilization of visible light. Furthermore, LCN exhibits stronger light absorption than CN. The Kubelka-Munk calculation method based on UV-vis DRS spectroscopy confirms the photocatalyst band gap, and the band structure of the catalyst is then calculated using Equation (1).

[0030] (1); in E g is the band gap potential, E VB is the valence band potential E CB The conduction band potential is calculated. The intermediate band gaps of CN and LCN are 2.84eV and 2.68eV respectively, and LCN has an intermediate band gap of 1.84eV ( Figure 2 (b) The energy band positions of CN and LCN were determined by combining VB-XPS valence band structure analysis. Figure 2 Middle C and Figure 2 The valence band positions of CN and LCN shown in (d) are 2.38eV and 2.17eV respectively. According to the formula, the conduction band positions of CN and LCN are -0.46eV and -0.51eV respectively. Figure 2Figure e shows the energy band structure diagram of CN and LCN, which proves that after doping with dead leaves of Bauhinia chinensis, the carbon source enters the g-C3N4 skeleton to form an intermediate band gap and induce an intermediate energy level. The photogenerated carriers are orderly separated and transferred under the induction of the carbon intermediate energy level, thereby significantly reducing their recombination rate.

[0031] 2. LCN / BiOI structure, morphology and composition.

[0032] In order to explore the structure and chemical composition of the composite material LCN / BiOI, XRD, FT-IR, scanning electron microscopy (SEM) and other characterizations were performed to study its morphology, structural form and composition. Figure 3 In the figure a, it can be observed that both CN / BiOI and LCN / BiOI have diffraction peaks at 27.6°, which corresponds to the (002) crystal plane formed by the stacking of aromatic sheets in g-C3N4. The characteristic diffraction peaks of BiOI appear at 32.5° and 46.7°, corresponding to the crystal planes (200) and (110), indicating that while LCN and BiOI are successfully composited, the structures of the two materials are not destroyed. In addition, it can be observed that the diffraction peaks corresponding to the (012) crystal plane of CN / BiOI and LCN / BiOI at 25.7° disappear, which may be due to etching during the thermal polymerization process. Infrared spectrum ( Figure 3 Middle b) shows that the composite material completely retains the absorption peak of g-C3N4, indicating that the BiOI composite does not destroy the complete skeleton of g-C3N4. The peak is at 808cm -1 and 1230-1630cm -1 In the range of 3230cm, they represent the stretching vibration characteristics of the triazine structural unit and -CN heterocyclic ring in g-C3N4. -1 The characteristic peaks nearby reflect the presence of -OH groups adsorbed by water molecules and some unattached amino groups (-NHx) on the g-C3N4 surface. XRD and FT-IR results indicate that the composite material does not change the crystal structure or destroy the g-C3N4 skeleton.

[0033] XPS was used to investigate the surface chemical properties and composition of the LCN / BiOI samples. Figure 4 The distribution of a in the figure is the full spectrum of elements of the composite material, and it can be observed that the sample is composed of Bi, I, O, N and C elements. Figure 4 The Bi4f spectrum of the sample is shown in b. Two diffraction peaks can be observed at 163.93eV and 158.63eV, corresponding to Bi4f 5 / 2 and Bi4f 7 / 2 .exist Figure 4 In c, two diffraction peaks are observed at 618.23eV and 629.78eV, corresponding to I3d 5 / 2 and I3d 3 / 2. Figure 4 There are three obvious diffraction peaks in the O1s spectrum of d, located at 529.28eV, 531.23eV and 532.73eV, corresponding to the Bi-O bonds in the layer, the IO bonds in BiOI and the -OH or H2O molecules adsorbed on the surface of the LCN / BiOI composite material. Figure 4 e is the N1s spectrum of the sample, and three fitting peaks appear at 400.58eV, 399.97eV and 397.98eV, corresponding to the sp involved in C-NHx, N-(C)3 and C=NC bonds, respectively. 2 Hybridized nitrogen. Figure 4 As shown in Figure (f), two obvious diffraction peaks can be observed in the high-resolution C1s spectrum, located at 288.03eV and 284.8eV, corresponding to C-NH2 and NC=N, respectively. This XPS result proves that the material was successfully prepared.

[0034] In order to further explore the morphology and structure of the prepared composite material, scanning electron microscopy (SEM) was used for characterization. Figure 5 The pure BiOI shown in (a) is a flower-like microsphere, which is assembled layer by layer from nanosheets with a sheet-like structure. Figure 5 In the LCN / BiOI in middle b, it can be observed that the sheet-like g-C3N4 is covered with these sheet-like nano-BiOI. Figure 5 Figure c shows the EDS elemental distribution of the LCN / BiOI sample. Characterization results indicate that the BiOI sample is uniformly distributed on the LCN surface and tightly bonded. Combined XRD, FR-IT, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) characterization results indicate that the composite material is not a simple physical mixture of two separate catalysts, but rather is chemically tightly bonded together while retaining the properties of the individual materials. Furthermore, the absence of CoCl2 in the electron microscopy image is due to its low content, but XPS characterization confirms its presence on the CdS sample. Therefore, these characterization results confirm the successful preparation of the composite material.

[0035] 3. Removal performance of LCN / BiOI on bisphenol A (BPA).

[0036] The prepared photocatalyst LCN / BiOI was used to test its performance in removing the pollutant bisphenol A (BPA). The photocatalytic degradation activity of BPA was tested at room temperature using a PCX-50CDiscover multi-channel photocatalytic reaction system (Purple, Beijing). Under 90% LED light intensity, 50 mg of the photocatalyst was added to 50 mL of a 10 ppm BPA solution and the degradation reaction was carried out. The results are shown in Figure 2. Figure 6As shown in Figure (a), carbon-doped LCN exhibits enhanced degradation activity compared to pure g-C₃N₄. This is attributed to the formation of carbon intermediate energy levels, which induces ordered electron transfer within the catalytic material and reduces carrier recombination. Test results show that the BiOI sample degraded less than 20% of BPA within 180 minutes. However, when combined with BiOI, the performance was significantly improved. LCN / BiOI-2, with a BiOI to LCN mass ratio of 10%, achieved 100% BPA degradation in just 60 minutes. This markedly improved degradation performance compared to the monolithic material. The activity also increased significantly compared to the undoped carbon sample CB / BiOI. Furthermore, the CN / BiOI sample exhibited a modest improvement in BPA removal activity compared to the CN sample, demonstrating that the Z-type heterojunction formation induces ordered electron transfer, thereby enhancing photocatalytic performance. The further improvement in LCN / BiOI indicates that the introduction of carbon intermediate energy levels further suppresses the disordered transport in the Z-type material, which is often caused by insufficient driving force. This significantly enhances the photocatalytic performance of the catalyst. The stability and recyclability of photocatalysts are important indicators for evaluating their practical applications. Figure 6 Figure b shows the results of five active degradation cycles under the same conditions, demonstrating that the photocatalyst maintained its high BPA degradation activity even in the fifth cycle, demonstrating good stability and reusability. This ensures the photocatalyst's high performance over the long term, helping to reduce costs and improve environmental sustainability.

[0037] 4. Investigation of the photocatalytic mechanism of LCN / BiOI.

[0038] In order to explore the photocatalytic mechanism of the composite material LCN / BiOI on BPA, DRS, EPR, PL, electrochemical impedance spectroscopy (EIS), IT and other tests were carried out. The band gaps of LCN and BiOI were calculated based on DRS, and then their band positions were determined by VB-XPS (X-ray photoelectron spectroscopy) characterization, and a mechanism diagram was drawn to explore the mechanism. Figure 7 Figure a uses UV-visible diffuse reflectance DRS to investigate the light absorption properties and response range of the composite material. It can be clearly observed that BiOI has the narrowest light response range and requires infrared light near 700nm to be activated. Sample CN ( Figure 2 (a) A steep absorption edge appears at 450nm, corresponding to intrinsic bandgap absorption. The CN / BiOI heterojunction material exhibits a blueshift in the absorption edge compared to pure BiOI. The LCN / BiOI material also exhibits a significantly enhanced absorption capacity while broadening the absorption range. This demonstrates that the introduction of carbon intermediate energy levels significantly enhances the catalytic material's ability to utilize light energy. Figure 7Figure b is an EPR spectrum that tests the electron delocalization ability of BiOI, CN, LCN, and the composite material under light irradiation. The results show that LCN / BiOI exhibits a higher unpaired electron signal, indicating that the introduction of carbon intermediate energy levels significantly increases the abundance of unpaired electrons. These electrons may form effective free radical ions that participate in photocatalytic redox reactions under light irradiation. The effective separation of photogenerated charges plays a vital role in the photocatalytic reaction process. Figure 7 c is the fluorescence emission peak at room temperature with an excitation wavelength of 325 nm. Figure 1 (d) and the BiOI sample, as well as the composite CN / BiOI sample, all exhibit high recombination rates for photogenerated carriers, while LCN and LCN / BiOI exhibit extremely low recombination rates. This demonstrates that the carbon intermediate energy level and heterojunction construction significantly reduce recombination with holes during the induced orderly electron transfer process. To test the charge transfer performance, the BiOI, CN / BiOI, and LCN / BiOI samples were characterized by photoelectrochemical methods. Figure 7 Figure d is the transient photocurrent (IT) spectra of BiOI, CN / BiOI and LCN-BiOI during 5 switching cycles. The results show that LCN / BiOI exhibits a higher photocurrent density. Figure 7 The EIS Nyquist results of the middle e show that the radius of the LCN / BiOI resistance arc is significantly reduced, indicating that the electron migration path of the sample LCN-BiOI is significantly smaller than that of the samples BiOI and CN / BiOI, the carrier migration rate becomes faster, and it has better charge migration ability.

[0039] In order to confirm the active species of the composite LCN-BiOI photocatalytic degradation of BPA, Figure 8 A and Figure 8 b is BMPO and DMPO as •O 2- Electron paramagnetic resonance (EPR) was performed with •OH spin trapping reagents. In the absence of light, the catalyst showed no obvious •O 2- and •OH free radical signals, which appear respectively when irradiated with visible light for 2 min. 2- The four characteristic peaks of free radicals and the characteristic peak of •OH free radical 1∶2∶1 prove that the catalyst produces •O participating in the photocatalytic reaction under light conditions. 2- and •OH radicals, the improvement of photocatalytic performance is due to •O 2- and the production of •OH radicals. Figure 8 In the figure c, free radical capture experiments were conducted on the photocatalyst. 10ppm BPA was degraded under visible light irradiation, and holes h were added respectively. + Capture agent EDTA-2Na, •O 2-The free radical scavenger p-benzoquinone BQ and the •OH scavenger isopropyl alcohol IPA. After adding IPA and BQ, the degradation rate was greatly reduced, indicating that the main active substances in photocatalytic degradation are •O 2- , •OH and h + , which is consistent with the EPR test results.

[0040] Based on the analysis of the above characterization results, the composite material LCN / BiOI induces electrons to migrate along a Z-type path under the introduction of carbon intermediate energy levels, thereby improving the photocatalytic activity. Figure 2 The LCN band position has been determined in the e. Figure 9 The band gap width of BiOI is 2.27eV calculated by Kubelka-Munk based on DRS characterization results. Figure 9 The VB-XPS spectrum in middle b estimated that the valence band of BiOI is at 1.03 eV, thus determining the energy band position of BiOI. Figure 9 Figure c shows the mechanism of photocatalytic degradation of antibiotic BPA by LCN / BiOI. Driven by the carbon intermediate energy level, PSⅡ (LCN) converts the e in the conduction band (CB) to - and h in the valence band (VB) of PSⅠ(BiOI) + Compound, thereby enhancing the h + Oxidation and PSⅠ(BiOI)CB - The reducibility of •O 2- ,•OH free radicals act as the main active species to degrade the antibiotic BPA into carbon dioxide and water.

[0041] The present invention uses urea and dead leaves of Bauhinia as precursors and adopts a thermal copolymerization method to prepare LCN. Characterizations such as DRS, PL, XRD, and FT-IR prove that the dead leaves are doped into the g-C3N4 skeleton as a carbon source to induce an intermediate band gap. The formed carbon intermediate energy level effectively suppresses carrier recombination. Then, LCN is compounded with BiOI using an in-situ deposition method to prepare LCN / BiOI. Application to the removal of the pollutant BPA found that LCN / BiOI-2 achieved a degradation rate of 100% for 10 ppm of BPA in just 60 minutes. The degradation rate is more than twice that of pure CN, LCN, and BiOI, and 1.64 times that of the composite material CN / BiOI without carbon doping. Based on DRS calculations of the band gap width of LCN, it was found that there is an intermediate energy level Es of 1.84 eV, proving that carbon has been successfully doped into the g-C3N4 skeleton, inducing an intermediate band gap and forming an intermediate energy level. Characterization tests such as DRS, PL, IT, and EIS demonstrate that BiOI and g-C3N4 form a Z-type heterojunction. The carbon intermediate energy level acts as an inductive force to drive Z-type electron transport and guide the orderly transfer of electrons, further helping photogenerated carriers to transport along the Z-shaped pattern, promoting carrier migration and separation and reducing recombination, thereby enhancing the photocatalytic activity of the LCN / BiOI system. Furthermore, EPR, ESR, and free radical capture experiments demonstrate that the active species involved in the photocatalytic redox reaction is primarily •O 2- and •OH radicals. Furthermore, the LCN / BiOI-2 sample maintained good stability and photocatalytic activity after five cycles under the same conditions, indicating that this composite material has considerable application potential. This research provides insights into the construction of efficient and stable Z-scheme composite photocatalysts with a strong driving force that promotes orderly carrier transfer.

[0042] Therefore, the present invention utilizes the aforementioned Z-type photocatalytic material based on carbon intermediate energy levels, its preparation method, and its application. Through step-by-step catalyst preparation, the orderly charge carrier transfer within the material is systematically controlled. LCN and BiOI are composited using an in-situ deposition method to prepare the Z-type photocatalyst LCN / BiOI. Under visible light irradiation, BPA is completely degraded in just 60 minutes, demonstrating that the carbon intermediate energy levels effectively induce orderly electron transfer within the Z-type heterojunction, significantly improving the removal efficiency of the BPA pollutant.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a Z-type photocatalytic material based on carbon intermediate energy levels, characterized in that: The steps include: Step 1, preparation of LCN: collecting dried leaves of the redbud tree and grinding them into powder, adding the redbud tree leaf powder and urea into an agate mortar and mixing thoroughly, transferring the mixture into a crucible and calcining it in a muffle furnace. After the calcination is completed, after the temperature in the furnace drops to room temperature, collecting the sample and grinding it to obtain LCN; Step 2, preparation of LCN / BiOI: Ethylene glycol and LCN were added to a beaker and stirred evenly, followed by the addition of bismuth nitrate. After stirring evenly, bismuth oxyiodide solution was added and continued to stir for 30 minutes. The solution was then transferred to a Teflon-lined container and placed in a stainless steel autoclave. The autoclave was placed in a forced air drying oven at 160°C for 45 minutes and then cooled to room temperature. The product was washed with water and ethanol and dried to obtain LCN / BiOI.

2. The method for preparing a Z-type photocatalytic material based on carbon intermediate energy levels according to claim 1, characterized in that: In step 1, the calcination conditions are as follows: heating from room temperature to 80°C and maintaining for 1 hour, then heating to 550°C and maintaining for 2 hours, with a heating rate of 5°C / min during the calcination process.

3. The method for preparing a Z-type photocatalytic material based on carbon intermediate energy levels according to claim 1, characterized in that: In step 2, the amount of ethylene glycol added is 20 mL.

4. The method for preparing a Z-type photocatalytic material based on carbon intermediate energy levels according to claim 1, characterized in that: In step 2, the added amount of bismuth nitrate is 17.4 mg, 22.2 mg, or 50 mg.

5. The method for preparing a Z-type photocatalytic material based on carbon intermediate energy levels according to claim 1, characterized in that: In step 2, the molar mass of bismuth iodide is the same as that of bismuth nitrate.

6. Z-type photocatalytic materials based on carbon intermediate energy levels, characterized by: It is prepared according to the preparation method according to any one of claims 1 to 5.

7. The use of the Z-type photocatalytic material based on carbon intermediate energy levels according to claim 6, characterized in that: Used to remove bisphenol A.

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