Nano-composite photocatalytic material as well as preparation method and application thereof

Abstract

The invention discloses a nano-composite photocatalytic material and a preparation method and application thereof.The preparation method comprises the steps that porous carbon nitride is added into deionized water and stirred, then a silver nitrate solution is added and stirred continuously, then a potassium bromide solution is dropwise added and stirred for a period of time, and the nano-composite photocatalytic material is obtained through filtering, washing, roasting and grinding. The porous carbon nitride and silver bromide nanoparticle composite material is obtained; adding a composite material of porous carbon nitride and silver bromide nanoparticles into deionized water, stirring, then adding the rhenium disulfide quantum dot dispersion liquid, continuously stirring, and then freeze-drying and drying; in the prepared nano composite photocatalytic material, p-g-C3N4 provides stable substrate and basic catalytic activity, AgBr widens the spectral response range and strengthens pollutant adsorption and degradation, ReS2 QDs optimizes charge transfer and improves hydrogen evolution kinetic efficiency, and efficient conversion of solar energy-chemical energy and efficient degradation of organic pollutants are achieved through cooperation of p-g-C3N4, AgBr and ReS2 QDs.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, specifically to a nanocomposite photocatalytic material, its preparation method, and its application. Background Technology

[0002] Against the backdrop of "dual carbon" goals and the normalization of ecological and environmental protection, environmental pollution control and clean energy substitution have become core issues concerning human sustainable development. The organic pollutant pollution from industrial wastewater discharge, coupled with greenhouse gas emissions and resource depletion caused by the consumption of traditional fossil fuels, has created a vicious cycle of "pollution-energy consumption," necessitating the development of integrated technologies that combine pollution control and clean energy production capabilities. Photocatalysis, with its solar-powered green characteristics, can simultaneously achieve the degradation and mineralization of organic pollutants and the decomposition of water to produce hydrogen, requiring no additional energy consumption and producing no secondary pollution. This makes it an ideal solution to the aforementioned dilemma. Its core lies in developing photocatalytic materials that possess highly efficient bifunctional catalytic activity, broad spectral response, and long-term cycle stability.

[0003] Among the currently reported photocatalytic materials, graphitic carbon nitride (g-C3N4) is highly favored in the field of photocatalysis due to its suitable band structure (band gap of approximately 2.7 eV), good chemical stability, low cost, and ease of preparation. However, its pure-phase materials suffer from inherent defects such as high photogenerated electron-hole recombination rate, limited specific surface area, and insufficient visible light utilization, which severely restricts its comprehensive efficiency in pollution control and hydrogen production. Traditional modification strategies, such as single-element doping and simple composites, can improve performance to some extent, but they are difficult to simultaneously meet the high efficiency requirements of bifunctional catalysis.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a nanocomposite photocatalytic material, its preparation method, and its application. This invention constructs a porous carbon nitride (pg-C3N4)-based ternary heterostructure nanocomposite photocatalytic material with a (ReS2QDs-AgBr NPs)@PCN structure through processes such as thermal polycondensation, chemical precipitation, and quantum dot introduction. In this nanocomposite photocatalytic material, pg-C3N4 provides a stable substrate and basic catalytic activity, AgBr broadens the spectral response range and enhances pollutant adsorption and degradation, and ReS2QDs optimizes charge transport and improves hydrogen evolution kinetic efficiency. These three components synergistically achieve efficient conversion of solar energy to chemical energy and efficient degradation of organic pollutants.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0007] The first aspect of this invention provides a method for preparing a nanocomposite photocatalytic material, the method comprising the following steps:

[0008] (a) Melamine is ground, then cyanuric acid is added and ground again. Then, anhydrous ethanol is added and stirred and ultrasonically treated. After drying, a precursor is obtained. The precursor is ground into powder and heated to 450~550℃ for calcination, cooling, grinding into powder, and drying to obtain porous carbon nitride.

[0009] (b) Porous carbon nitride was added to deionized water and stirred. Silver nitrate solution was then added and stirred to obtain a dispersion. Potassium bromide solution was added dropwise to the dispersion and stirred for a period of time. After filtration, washing, calcination, and grinding, a composite material of porous carbon nitride and silver bromide nanoparticles was obtained.

[0010] (c) Grind rhenium disulfide powder and add N-methylpyrrolidone to mix well to obtain a mixture. The mixture is then subjected to ultrasonic crushing and centrifugation. The supernatant is collected to obtain a rhenium disulfide quantum dot dispersion.

[0011] (d) The composite material of porous carbon nitride and silver bromide nanoparticles is added to deionized water and stirred for a period of time. Then, rhenium disulfide quantum dot dispersion is added and stirred for a period of time. After freeze drying and baking, the nanocomposite photocatalytic material is obtained.

[0012] Preferably, in step (a), the mass ratio of melamine to cyanuric acid is (2~3):1.

[0013] Preferably, in step (a), the heating rate is 1.8~2.2℃ / min and the calcination time is 4~6h.

[0014] Preferably, in step (b), the calcination temperature is 120~140℃ and the time is 18~25h; the mass content of silver bromide nanoparticles in the composite material of porous carbon nitride and silver bromide nanoparticles is 5%~20%.

[0015] Preferably, in step (c), the ultrasonic power is 160~200W and the time is 8~12h; the centrifugation includes first centrifuging at 3500~4500rpm for 15~25min, collecting the supernatant, and then centrifuging at 12000~14000rpm for 15~25min.

[0016] Preferably, in step (d), the mass percentage of rhenium disulfide quantum dots in the nanocomposite photocatalytic material is 1% to 10%.

[0017] A second aspect of the present invention provides a nanocomposite photocatalytic material prepared by the above-described preparation method.

[0018] The third aspect of this invention provides an application of the nanocomposite photocatalytic material prepared by the above-described method in the photocatalytic degradation of organic matter.

[0019] The fourth aspect of this invention provides an application of the nanocomposite photocatalytic material prepared by the above-described method in wastewater treatment.

[0020] The fifth aspect of this invention provides an application of the nanocomposite photocatalytic material prepared by the above-described method in photocatalytic hydrogen production.

[0021] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0022] This invention utilizes processes such as thermal polycondensation, chemical precipitation, and quantum dot introduction to construct a porous carbon nitride (pg-C3N4)-based ternary heterostructure nanocomposite photocatalytic material (ReS2QDs-AgBr NPs)@PCN. In this nanocomposite photocatalytic material, pg-C3N4 provides a stable substrate and basic catalytic activity, AgBr broadens the spectral response range and enhances pollutant adsorption and degradation, and ReS2QDs optimizes charge transport and improves hydrogen evolution kinetic efficiency. These three elements synergistically achieve efficient conversion of solar energy to chemical energy and efficient degradation of organic pollutants. The multi-heterostructure ReS2QDs-AgBr NPs@PCN can simultaneously address both organic pollutant degradation and hydrogen production on the same structural platform, providing a valuable approach for the subsequent design of integrated photocatalytic materials that combine environmental governance and energy conversion functions. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0024] Figure 1 X-ray diffraction (XRD) patterns of pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for embodiments of the present invention.

[0025] Figure 2Scanning electron microscope (SEM) images of pg-C3N4, AgBrNPs@pg-C3N4, and (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for embodiments of the present invention, as well as transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images of ReS2 QDs and (AgBr NPs-ReS2 QDs)@pg-C3N4.

[0026] Figure 3 The X-ray photoelectron diffraction (XPS) pattern of (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for an embodiment of the present invention.

[0027] Figure 4 The N2 adsorption-desorption isotherms and pore size distribution diagrams of pg-C3N4, AgBr NPs@pg-C3N4 and (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for embodiments of the present invention are shown.

[0028] Figure 5 Photoluminescence (PL) spectra of pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for embodiments of the present invention.

[0029] Figure 6 Photocurrent response (a) and electrochemical impedance spectroscopy (b) of pg-C3N4, AgBr NPs@pg-C3N4 and (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for embodiments of the present invention.

[0030] Figure 7 Photocatalytic degradation curves (a) and pseudo-first-order kinetic fitting diagrams (b) of Rhodamine B (RhB) prepared by different materials in the embodiments of the present invention.

[0031] Figure 8 A schematic diagram of the photocatalytic reaction mechanism of (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared in an embodiment of the present invention.

[0032] Figure 9 The diagram shows the PCN-AgBr (binary) and PCN-AgBr-ReS2 (ternary) heterojunction structure models constructed in the theoretical calculations of this invention.

[0033] Figure 10 This is a model diagram of the adsorption of RhB molecules on the PCN-AgBr and PCN-AgBr-ReS2 surfaces in the theoretical calculations of this invention.

[0034] Figure 11This is a diagram showing the adsorption model of hydrogen atoms at different active sites (Ag site, S site) during the HER process in the theoretical calculation of this invention.

[0035] Figure 12 This is the density of electronic states (DOS) diagram of PCN-AgBr and PCN-AgBr-ReS2 in the theoretical calculations of this invention.

[0036] Figure 13 This is a charge density difference (Δρ) diagram of the PCN-AgBr-ReS2 heterojunction in the theoretical calculations of this invention.

[0037] Figure 14 This is a step diagram of the HER free energy of different active sites in the theoretical calculations of this invention.

[0038] Figure 15 The graph shows the hydrogen generation rate per unit mass of different materials prepared in the embodiments of the present invention in photocatalytic hydrogen production.

[0039] Figure 16 The bar chart shows the total hydrogen generation rate of different materials prepared in the embodiments of the present invention within 1 to 6 hours.

[0040] Figure 17 The hydrogen generation rate-time curve of (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared for embodiments of the present invention in multiple cycle experiments.

[0041] Figure 18 The apparent quantum efficiency (AQE) of (AgBr NPs-ReS2 QDs)@pg-C3N4 prepared in the embodiments of the present invention under different wavelengths of light. Detailed Implementation

[0042] The embodiments of the technical solution of the present invention will be described in detail below with reference to the examples. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0043] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0044] This invention provides a method for preparing a nanocomposite photocatalytic material, the method comprising the following steps:

[0045] (a) Melamine is ground, then cyanuric acid is added and ground again. Then, anhydrous ethanol is added and stirred and ultrasonically treated. After drying, a precursor is obtained. The precursor is ground into powder and heated to 450~550℃ for calcination, cooling, grinding into powder, and drying to obtain porous carbon nitride.

[0046] (b) Porous carbon nitride was added to deionized water and stirred. Silver nitrate solution was then added and stirred to obtain a dispersion. Potassium bromide solution was added dropwise to the dispersion and stirred for a period of time. After filtration, washing, calcination, and grinding, a composite material of porous carbon nitride and silver bromide nanoparticles was obtained.

[0047] (c) Grind rhenium disulfide powder and add N-methylpyrrolidone to mix well to obtain a mixture. The mixture is then subjected to ultrasonic crushing and centrifugation. The supernatant is collected to obtain a rhenium disulfide quantum dot dispersion.

[0048] (d) The composite material of porous carbon nitride and silver bromide nanoparticles is added to deionized water and stirred for a period of time. Then, rhenium disulfide quantum dot dispersion is added and stirred for a period of time. After freeze drying and baking, the nanocomposite photocatalytic material is obtained.

[0049] In this invention, silver bromide (AgBr), as a narrow bandgap semiconductor (bandgap of approximately 2.6 eV), possesses excellent visible light harvesting ability and unique electron transport characteristics. It is also non-toxic and environmentally friendly. When combined with pg-C3N4, it forms a heterojunction structure, significantly promoting the separation of photogenerated carriers and enhancing the material's adsorption and degradation activity for organic pollutants. Rhenium disulfide quantum dots (ReS2QDs), as a novel two-dimensional graphene-like material, possess quantum confinement effects and highly efficient charge separation capabilities. They not only further optimize charge transport pathways but also provide abundant catalytic active sites. When combined with pg-C3N4, they produce a synergistic effect, simultaneously improving pollution degradation efficiency and hydrogen production performance.

[0050] In one embodiment, in step (a), the mass ratio of melamine to cyanuric acid is (2~3):1.

[0051] In one embodiment, in step (a), the heating rate is 1.8~2.2℃ / min, and the calcination time is 4~6h.

[0052] In one embodiment, in step (b), the calcination temperature is 120~140℃ and the time is 18~25h; the mass content of silver bromide nanoparticles in the composite material of porous carbon nitride and silver bromide nanoparticles is 5%~20%.

[0053] In one embodiment, in step (c), the ultrasonic power is 160~200W and the time is 8~12h; the centrifugation includes first centrifuging at 3500~4500rpm for 15~25min, collecting the supernatant, and then centrifuging at 12000~14000rpm for 15~25min.

[0054] In one embodiment, in step (d), the mass percentage of rhenium disulfide quantum dots in the nanocomposite photocatalytic material is 1% to 10%.

[0055] Another embodiment of the present invention provides a nanocomposite photocatalytic material prepared by the above preparation method.

[0056] Another embodiment of the present invention provides an application of the nanocomposite photocatalytic material prepared by the above preparation method in the photocatalytic degradation of organic matter.

[0057] Another embodiment of the present invention provides an application of the nanocomposite photocatalytic material prepared by the above preparation method in wastewater treatment.

[0058] Another embodiment of the present invention provides an application of the nanocomposite photocatalytic material prepared by the above preparation method in photocatalytic hydrogen production.

[0059] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0060] Example

[0061] This embodiment describes a method for preparing a nanocomposite photocatalytic material, the method comprising the following steps:

[0062] (a) Weigh 5g of melamine, grind for 10min, then weigh 2g of cyanuric acid and add it to the mixture, grind again for 10min, transfer the ground material to a beaker, add 100ml of anhydrous ethanol, stir for 3h, sonicate for 2h, and place the treated material in a 90℃ water bath to evaporate to dryness, obtaining a white block precursor; then, grind the white precursor into powder, place it in a ceramic plate and transfer it to a tube furnace, and calcine it to 500℃ at a heating rate of 2℃ / min for 5h; after the temperature inside the tube has naturally cooled to room temperature, remove the material and grind it into powder, and finally dry it in a 60℃ drying oven to obtain porous carbon nitride (denoted as PCN or pg-C3N4);

[0063] (b) Take 0.5 g of PCN powder and place it in a beaker. Add 50 ml of deionized water and stir magnetically for 30 min. Then add 7 ml of 0.1 mol / L AgNO3 solution and stir again for 30 min to obtain a dispersion. At the same time, weigh 0.08 g of KBr crystals and place them in another beaker. Add 10 ml of deionized water and stir magnetically for 10 min until completely dissolved. Add the dissolved KBr solution dropwise to the dispersion using a dropping bottle and stir continuously at room temperature for 3 h to obtain a pale yellow flocculent precipitate. Filter and wash the precipitate with deionized water, calcine it in an oven at 130℃ for 20 h, cool it to room temperature, and grind it into powder to obtain a composite material of porous carbon nitride and silver bromide nanoparticles (denoted as AgBr NPs@PCN or AgBr NPs@pg-C3N4).

[0064] (c) Weigh 1g of ReS2 black powder and place it in a mortar and grind for 2 hours until the powder is completely uniform and fine. Transfer the material to a beaker and add 100ml of N-methylpyrrolidone (NMP) solvent to the ground ReS2 black powder. Use a magnetic stirrer to mix it thoroughly. Then, place the mixture in an ultrasonic homogenizer and sonicate it at 180W for 10 hours. Transfer the ultrasonic suspension to a refrigerated centrifuge and centrifuge at 4000rpm for 20 minutes. Collect the supernatant and centrifuge the collected supernatant at 13000rpm for 20 minutes. Finally, collect the supernatant to obtain a rhenium disulfide quantum dot (ReS2QDs) dispersion.

[0065] (d) Take 0.2 g of AgBr NPs@PCN material and add it to a beaker containing 20 ml of deionized water. Stir at room temperature for 30 min, add 1 ml of ReS2QDs dispersion, continue stirring for 30 min, then transfer to a freeze dryer to dry, and finally keep in an oven at 100℃ for 6 h to obtain nanocomposite photocatalytic material (denoted as (AgBr NPs-ReS2QDs)@pg-C3N4 or (ReS2QDs-AgBr NPs)@pg-C3N4).

[0066] Comparative Example 1

[0067] This comparative example illustrates a method for preparing silver bromide nanoparticles, the method comprising the following steps:

[0068] Add 50 ml of deionized water to a beaker, then add 7 ml of 0.1 mol / L AgNO3 solution, and stir again for 30 min to obtain a dispersion. At the same time, weigh 0.08 g of KBr crystals and put them into another beaker, add 10 ml of deionized water, and stir magnetically for 10 min until completely dissolved. Add the dissolved KBr solution dropwise to the dispersion using a dropping bottle, and stir continuously for 3 h under all conditions to obtain a pale yellow flocculent precipitate. Filter and wash the precipitate with deionized water, calcine it in an oven at 130℃ for 20 h, cool it to room temperature, and grind it into powder to obtain silver bromide nanoparticles (denoted as AgBr NPs).

[0069] Comparative Example 2

[0070] This comparative example illustrates a method for preparing a ReS2QDs@pg-C3N4 composite material, the method comprising the following steps:

[0071] (a) Weigh 5g of melamine, grind for 10min, then weigh 2g of cyanuric acid and add it to the mixture, grind again for 10min, transfer the ground material to a beaker, add 100ml of anhydrous ethanol, stir for 3h, sonicate for 2h, and place the treated material in a 90℃ water bath to evaporate to dryness, obtaining a white block precursor; then, grind the white precursor into powder, place it in a ceramic plate and transfer it to a tube furnace, and calcine it to 500℃ at a heating rate of 2℃ / min for 5h; after the temperature inside the tube has naturally cooled to room temperature, remove the material and grind it into powder, and finally dry it in a 60℃ drying oven to obtain porous carbon nitride (denoted as PCN or pg-C3N4);

[0072] (b) Weigh 1g of ReS2 black powder and place it in a mortar and grind for 2 hours until the powder is completely uniform and fine. Transfer the material to a beaker and add 100ml of N-methylpyrrolidone (NMP) solvent to the ground black ReS2 powder. Use a magnetic stirrer to mix it thoroughly. Then, place the mixture in an ultrasonic homogenizer and sonicate it at 180W for 10 hours. Transfer the ultrasonic suspension to a refrigerated centrifuge and centrifuge at 4000rpm for 20 minutes. Collect the supernatant and centrifuge the collected supernatant at 13000rpm for 20 minutes. Finally, collect the supernatant to obtain a rhenium disulfide quantum dot (ReS2QDs) dispersion.

[0073] (c) Take 0.2 g of PCN material and add it to a beaker containing 20 ml of deionized water. Stir at room temperature for 30 min, add 1 ml of ReS2QDs dispersion, continue stirring for 30 min, then transfer to a freeze dryer to dry, and finally keep in an oven at 100℃ for 6 h to obtain ReS2QDs@pg-C3N4 composite material.

[0074] Experimental Example 1

[0075] pg-C3N4, AgBr NPs (15% by mass)@pg-C3N4, and (AgBr NPs (15% by mass)-ReS2QDs (5% by mass))@pg-C3N4 were prepared according to the method described in the examples; the rhenium disulfide quantum dot dispersion was dried to obtain ReS2QDs;

[0076] 1. X-ray diffraction (XRD) analysis was performed on the above-mentioned pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4. The analysis results are as follows: Figure 1 As shown;

[0077] Depend on Figure 1 It can be seen that the diffraction peak of pg-C3N4 is at 27.875, corresponding to the crystal plane (110), which is consistent with the information in the standard card (PDF50-1512). The diffraction peak positions of AgBr NPs@pg-C3N4 are (26.725), (30.960), (44.346), (52.486), (55.042), (64.476), and (73.261), and their corresponding crystal planes are (111), (200), (220), (311), (222), (400), and (420), which also correspond to the standard PDF card (PDF 06-0438). In addition, two peaks appear at (14.586) and (29.425), corresponding to the (001) and (002) crystal planes of ReS2 (PDF 52-0818). XRD results of pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4 showed that these materials all had obvious peaks, which corresponded to their respective standard cards. The above information indicates that AgBr NPs@pg-C3N4 and (AgBr NPs-ReS2QDs)@pg-C3N4 composite materials were successfully prepared.

[0078] 2. Scanning electron microscopy was used to observe the above-mentioned pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4. The results are as follows: Figure 2 As shown; transmission electron microscopy (TEM) analysis of ReS2QDs and (AgBr NPs-ReS2QDs)@pg-C3N4 yielded the following results. Figure 2 As shown;

[0079] Figure 2 In the image, (a) is the SEM image of pg-C3N4; (b) is the SEM image of AgBr NPs@pg-C3N4; (c) is the SEM image of (AgBr NPs-ReS2QDs)@pg-C3N4; (d) is the TEM image of ReS2 QDs; (e) is the HRTEM image of ReS2 QDs; and (f) is the TEM image of (AgBr NPs-ReS2QDs)@pg-C3N4.

[0080] Depend on Figure 2As can be seen from SEM observation, AgBr nanoparticles are distributed on the surface of pg-C3N4, forming a compact heterostructure. TEM testing further reveals the size and shape of these nanoparticles, as well as their distribution on pg-C3N4. Figure (a) shows the morphology of porous carbon nitride. Compared with traditional graphitic carbon nitride, this material is porous, with larger pores and specific surface area, providing more photocatalytic sites and facilitating the transfer of photogenerated electrons. Figures (b) and (c) show the SEM images of AgBr@pg-C3N4 and (AgBr NPs -ReS2QDs)@pg-C3N4. AgBr NPs and ReS2QDs are dispersed on the surface of PCN, forming a surface heterostructure. This structure facilitates the transfer of photogenerated electrons between pg-C3N4, AgBr NPs, and ReS2QDs, improving the efficiency of photocatalytic pollutant degradation. Figures (d) and (e) are TEM and HRTEM images of ReS2QDs, respectively. ReS2QDs belong to the hexagonal crystal system with a lattice spacing of d = 0.273 nm. The black dots in Figure (d) represent quantum dots. From the lattice stripe pattern in Figure (e), it can be seen that the lattice spacing of the prepared ReS2QDs is 0.27 nm, corresponding to the (100) crystal plane, which is basically consistent with the information reported in the literature. Figure (f) is the TEM image of (AgBr NPs-ReS2QDs)@pg-C3N4. ReS2QDs and AgBr NPs are dispersed in a disordered state on the PCN surface. Combined with Figure (c), it can be found that PCN even encapsulates some of the ReS2QDs and AgBr NPs, realizing a surface heterostructure and forming a three-dimensional heterostructure. This structural feature enhances the interfacial contact and charge separation efficiency, which is beneficial to charge separation in photocatalysis and synergistically improves the photocatalytic performance.

[0081] 3. X-ray photoelectron diffraction (XPD) analysis was performed on the above (AgBr NPs-ReS2QDs)@pg-C3N4. The results are as follows: Figure 3 As shown;

[0082] Figure 3 In the image, (a) survey full spectrum, (b) N Is, (c) Br 3d, (d) Ag 3d, (e) S 2p, (f) Re 4f;

[0083] Depend on Figure 3As shown in Figure (a), the survey is a low-resolution full-band spectrum of the composite material, in which C, N, Ag, S, Br, and Re elements were found. Peak separation was performed on the spectra of each element, and the characteristic peaks of pg-C3N4 at 284.8 eV, 287.9 ​​eV (C Is) and 400.8 eV, 399.5 eV, 398.3 eV (N Is) (Figure (b)) were observed. Figure (c) shows the Br3d... 3 / 2 and Br 3d 5 / 2 The energy peaks are at 67.8 eV and 68.8 eV. As can be seen from Figure (d), Ag 3d consists of two characteristic energy peaks, namely Ag 3d... 3 / 2 Ag 3d 5 / 2 The energies are 377.4 eV and 367.3 eV. The main peaks in Figure (e) correspond to S2p binding energies of 168.2 eV and 166.8 eV, respectively. 2 / 1 and S2p 3 / 2 Figure (f) shows that Re 4f has Re 4f 5 / 2 Re 4f 7 / 2 Two characteristic energy peaks were observed, with peak energies of 44.8 eV and 41.1 eV. Therefore, XPS spectroscopy further confirms that ReS2QDs and AgBr NPs were successfully doped into pg-C3N4.

[0084] 4. BET surface area and pore size analyses were performed on the above-mentioned pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4. The results are as follows: Figure 4 As shown, Figure 4 In the middle, the top left figure shows the pore size distribution curves of each material;

[0085] Depend on Figure 4It can be seen that the adsorption-desorption curves of AgBr NPs-ReS2QDs@pg-C3N4, AgBr NPs@pg-C3N4, and pg-C3N4 are relatively smooth at low pressure and steep at high pressure. The N2 adsorption-desorption isotherms of pg-C3N4, AgBr NPs@pg-C3N4, and (AgBrNPs-ReS2QDs)@pg-C3N4 are Type III adsorption-desorption curves. In the low-pressure region, the adsorption amount is low and the curve is flat, indicating that the interaction force between the adsorbent and the adsorbate is weak, and monolayer physical adsorption dominates. In the medium and high pressure regions, the adsorption amount increases slowly, the slope of the curve shows an upward trend, and multilayer adsorption gradually forms. The adsorption amount gradually increases significantly with increasing pressure, and the curve continues to rise and become steeper, indicating that the pores begin to be filled by the adsorbate, and mesoporous and macroporous filling phenomena occur. The specific surface areas of pure pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4 nanocomposites were 20.48, 24.32, and 35.28 m² / g, respectively. These results indicate that the prepared (AgBrNPs-ReS2QDs)@pg-C3N4 composite photocatalyst exhibits a large specific surface area and a porous structure, which is beneficial for the sufficient contact and reaction between (AgBr NPs-ReS2QDs)@pg-C3N4 and the pollutant RhB, thereby improving the adsorption and degradation of the pollutant and enhancing its photocatalytic efficiency.

[0086] 5. Photoluminescence spectroscopy analysis was performed on the above-mentioned pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4. The structures are shown in the figure below. Figure 5 As shown;

[0087] Depend on Figure 5It is known that the original pg-C3N4 exhibits a significant photocatalytic flux (PL) peak at approximately 450 nm, with an intensity as high as about 6200 au. This indicates a relatively high recombination rate of photogenerated electron-hole pairs and poor carrier separation efficiency, which limits the photocatalytic activity. Introducing approximately 15% AgBr significantly reduces the PL intensity of the AgBr NPs@pg-C3N4 composite material to about 2000 au. This is attributed to the heterojunction formed by AgBr and pg-C3N4 accelerating charge separation and extending the carrier lifetime. Further incorporating 5% ReS2 quantum dots, the resulting (AgBr NPs-ReS2QDs)@pg-C3N4 composite material exhibits the lowest PL intensity, approximately 620 au. The quantum confinement effect of ReS2 and its synergistic effect with AgBr further optimize the charge separation process, creating a multi-interface charge separation mechanism that greatly reduces the recombination probability. The spectral characteristics of the materials show that the high photocatalytic intensity (PL) of pg-C3N4 indicates that its photocatalytic performance is limited by electron-hole recombination. However, with the introduction of AgBr NPs and ReS2QDs, the photocatalytic efficiency is significantly improved by promoting charge separation. The (AgBr NPs-ReS2QDs)@pg-C3N4 composite material exhibits excellent photocatalytic performance, demonstrating the strongest charge separation capability. Based on the above analysis, by constructing heterojunctions and introducing quantum dots to gradually reduce the PL intensity, the carrier separation efficiency can be effectively improved, thus enhancing the photocatalytic performance of the material.

[0088] Experiment Example 2

[0089] pg-C3N4, AgBr NPs, AgBr NPs (5%)@pg-C3N4, AgBr NPs (10%)@pg-C3N4, AgBr NPs (15%)@pg-C3N4, AgBr NPs (20%)@pg-C3N4, and (AgBr NPs (15%)-ReS2QDs (5%))@pg-C3N4 were obtained according to the preparation methods of Examples and Comparative Example 1.

[0090] 1. The photoelectrochemical behavior of the above-mentioned pg-C3N4, AgBr NPs (15%)@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4 was analyzed, and the results are as follows: Figure 6 As shown, Figure 6 In the figure, (a) is the cutoff photocurrent response of each material every 50 seconds of light switching on / off; (b) is the electrochemical impedance spectrum of each material under visible light irradiation.

[0091] Depend on Figure 6 As can be seen, (a) presents the it curves of pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4 heterostructures under visible light irradiation. Under illumination, pg-C3N4 exhibits a relatively low photocurrent density, indicating its relatively weak basic photocatalytic activity. However, once AgBr NPs are introduced to construct the AgBr NPs@pg-C3N4 composite material, its photocurrent density shows a significant increase, indicating that the introduction of AgBr NPs significantly enhances the material's absorption and electron transfer capabilities. Furthermore, when ReS2QDs are introduced on top of AgBr NPs to form the (AgBrNPs-ReS2QDs)@pg-C3N4 composite material, its photocurrent density reaches its peak and exhibits a more stable response under illumination switching conditions. This demonstrates a synergistic effect between ReS2QDs and AgBr NPs, jointly enhancing the photoelectrochemical properties of the material and thus promoting the degradation of Rhodamine B. Figure (b) shows the EIS of pg-C3N4, AgBr NPs@pg-C3N4, and (AgBr NPs-ReS2QDs)@pg-C3N4. The charge transfer impedance of the samples is significantly correlated with the photogenerated carrier separation efficiency: a smaller arc radius reflects lower interfacial charge transfer resistance, indicating that photoexcited electron-hole pairs can achieve higher separation efficiency on the catalyst surface. According to the semiconductor photocatalysis mechanism, the change in carrier recombination probability directly allows more effective electrons to participate in the redox reaction, and the size of the arc radius of the impedance spectrum can serve as an important characterization basis for evaluating the improvement of the material's photocatalytic activity. As can be seen from the figure, pg-C3N4 has the largest arc radius, resulting in a higher impedance during charge transfer, which limits the improvement of its photocatalytic performance. The relatively low impedance of AgBr NPs@pg-C3N4 indicates that the introduction of AgBr NPs reduces the charge transfer impedance of the material. When ReS2QDs are further added to construct the (AgBr NPs-ReS2QDs)@pg-C3N4 composite material, the radius of curvature is minimized and the impedance is reduced to the lowest level, indicating that the charge transfer efficiency in this material reaches its maximum value.

[0092] Analysis of the photocurrent and impedance characteristics of these three materials revealed that the (AgBr NPs-ReS2QDs)@pg-C3N4 composite material exhibited the best photoelectrochemical performance, with its photocatalytic performance also being the most outstanding. This is mainly due to the synergistic effect of ReS2QDs and AgBr NPs, which significantly enhances the composite material's light absorption, electron transfer, and charge transfer. Therefore, the photocatalytic degradation of pollutants such as Rhodamine B using (AgBr NPs-ReS2QDs)@pg-C3N4 is feasible.

[0093] 2. Photocatalytic degradation analysis was performed on the above materials, with Rhodamine B as the target pollutant; a 20 mg·L⁻¹ solution was prepared. -1 20 mg of each material was added to 100 mL of RhB aqueous solution to form a suspension. The suspension was stirred in the dark for 30 min to reach adsorption-desorption equilibrium. Then, the degradation experiment was carried out under simulated sunlight irradiation by a 300 W xenon lamp. Samples were taken at regular intervals during the reaction. The solution was filtered through a 0.20 μm filter membrane and the intensity of the characteristic absorption peak of RhB was measured by UV-Vis. The degradation rate was calculated according to C / C0×100%, and the rate constant was fitted using the pseudo-first-order kinetic model In(C0 / C)=kt.

[0094] The results are as follows Figure 7 As shown, Figure 7 In the diagram, (a) shows the photocatalytic degradation, and (b) shows the reaction kinetics corresponding to (a).

[0095] Depend on Figure 7It can be seen that using a 300 W xenon lamp to simulate sunlight, and pg-C3N4, AgBr NPs, AgBr NPs(5 wt%, 10 wt%, 15 wt%, 20 wt%)@pg-C3N4, and (ReS2QDs(5%)-AgBr NPs(15%))@pg-C3N4 as catalysts, photocatalytic degradation of RhB was carried out. The reaction kinetics of pg-C3N4, AgBr NPs, AgBr NPs(5 wt%, 10 wt%, 15 wt%, 20 wt%)@pg-C3N4, and (ReS2QDs(5%)-AgBr NPs(15%))@pg-C3N4 nanomaterials were studied respectively. Figure (a) shows that compared with the parent material pg-C3N4 and the second doped material AgBr NPs alone, AgBr NPs@pg-C3N4 exhibits superior photocatalytic performance, and AgBr NPs(15%)@pg-C3N4 with a doping content of 15 wt% shows higher photocatalytic activity. Under the same illumination conditions, after 35 min of xenon lamp irradiation, the degradation rates of RhB by pure pg-C3N4 and AgBr NPs were 88.4% and 87%, respectively, while the degradation rate of AgBr NPs(5%)@pg-C3N4 was 90.35%. Compared with traditional graphitic carbon nitride materials, porous graphitic carbon nitride has more photocatalytic sites and exhibits better photocatalytic efficiency. After 35 min of irradiation, the degradation rate of AgBr NPs(10%)@pg-C3N4 was 91%, and that of AgBr NPs(15%)@pg-C3N4 was 93%. The degradation rate of AgBr NPs(20%)@pg-C3N4 was 89.8%, indicating that the binary composite material exhibited better performance when 15% AgBr NPs were added. However, the degradation rate of Rhodamine B by (ReS2QDs(5%)-AgBr NPs(15%))@pg-C3N4 reached 97.8% at 25 min and 98.6% at 30 min. Therefore, (ReS2QDs(5%)-AgBr NPs(15%))@pg-C3N4 showed the highest photocatalytic degradation performance for Rhodamine B. The experimental results indicate that the addition of an appropriate photocatalyst provides more active sites for porous graphitic carbon nitride materials, thereby improving their photocatalytic efficiency.Furthermore, the kinetic fitting curves in Figure (b) show that the reactions of pg-C3N4, AgBr NPs and (ReS2QDs-AgBr NPs)@pg-C3N4 are first-order reactions. The figure shows that (ReS2QDs(5%)-AgBr NPs(15%))@pg-C3N4 (0.1319 min). -1 Compared to pg-C3N4 (0.0630 min) -1 AgBrNPs (0.0598 min) -1 ), AgBr NPs(5%)@pg-C3N4(0.0775 min -1 ), AgBr NPs(10%)@pg-C3N4(0.0793 min -1 ), AgBr NPs (15%)@pg-C3N4(0.0881min -1 ), AgBr NPs(20%)@pg-C3N4(0.0781 min -1 The reaction showed the largest rate constant, indicating that (ReS2QDs(5%)-AgBr NPs(15%))@p-gC3N4(0.1319 min) -1 The pg-C3N4 catalyst exhibited the highest photocatalytic performance in degrading Rhodamine B. Furthermore, pg-C3N4 and AgBr NPs showed lower reaction rate constants and lower degradation rates of Rhodamine B, indicating that the degradation of Rhodamine B by pure pg-C3N4 and AgBr NPs was primarily physisorption. This study systematically tested the photocatalytic degradation efficiency of different catalysts for Rhodamine B under simulated sunlight using a 300 W xenon lamp. pg-C3N4, with its porous structure providing abundant active sites, achieved a degradation rate of 88.4% at 35 minutes, which was better than that of traditional g-C3N4. Using AgBr NPs to construct a binary composite material, 15 wt% AgBr NPs@pg-C3N4 showed the best performance; excessive loading up to 20 wt% resulted in a decrease in activity due to aggregation. Further addition of ReS2QDs to construct a ternary composite material (ReS2QDs (5%)-AgBr NPs (15%))@pg-C3N4 significantly enhanced the catalytic activity, achieving a degradation rate of 97.8% and a reaction rate constant of 0.1319 min after 25 minutes. -1 This value, and that of pure pg-C3N4 (0.0630 min) -1 ), AgBr NPs (0.0598 min) -1Compared to the previous method, the efficiency was improved by approximately 2.1 times. Kinetic analysis verified that all systems conformed to first-order reaction laws, and that physical adsorption dominated the adsorption of pure component materials. The results show that optimizing the semiconductor heterojunction design can effectively promote the separation of photogenerated carriers and synergistically enhance photocatalytic capabilities. The ternary composite strategy significantly improves catalytic efficiency through the synergistic cooperation of multiple active sites.

[0096] 3. A schematic diagram of the reaction mechanism of (ReS2QDs (5%)-AgBr NPs (15%))@pg-C3N4 is shown below. Figure 8 As shown;

[0097] pg-C3N4, a non-metallic polymer semiconductor, has a narrow band gap of 2.7 eV, enabling it to absorb visible light energy. AgBr, with a band gap of 2.6 eV, can further enhance the light absorption capability of this composite material. The conduction band of pg-C3N4 is higher than that of the corresponding AgBr, meaning the charge-weighted average (CB) value of pg-C3N4 is lower than that of AgBr. In the AgBr NPs@pg-C3N4 system, the charge transfer and recombination mechanism may be as follows: Under illumination, pg-C3N4 absorbs photons, generating electron-hole pairs. The excited electrons jump from the valence band to the conduction band, leaving holes in the valence band. The electrons rapidly transfer from the conduction band of pg-C3N4 to the AgBr conduction band. After migrating to the surface of the photocatalyst, the electrons react with dissolved oxygen in the water to generate superoxide radicals (•O2). ﹣ The holes migrate from the valence band of AgBr to the valence band of pg-C3N4, achieving effective charge separation. When the holes reach the catalyst surface, they react with hydroxide ions (OH-) in the water. ﹣ The ionic reaction generates hydroxyl radicals (•OH), which are strong oxidizing agents capable of oxidizing and degrading the pollutant Rhodamine B, producing H₂O and CO₂. After the introduction of ReS₂QDs, they can also absorb photons and generate photogenerated electron-hole pairs. These photogenerated charge carriers rapidly separate within the ReS₂QDs, with electrons migrating to the conduction band of AgBr and holes remaining in the valence band. Due to their quantum confinement effect, ReS₂ quantum dots further promote charge separation and migration. Furthermore, the synergistic effect of ReS₂QDs and AgBr NPs enhances the light absorption, charge separation, and migration capabilities of the composite material, thereby improving its photocatalytic activity.

[0098] Experimental Example 3

[0099] This experimental example is a study of theoretical calculations and hydrogen production mechanisms:

[0100] 1. Calculation Task and Overall Approach

[0101] To theoretically support the performance of the (ReS2QDs (5%) - AgBr NPs (15%))@pg-C3N4 photocatalytic system in the degradation and hydrogen production of Rhodamine B, first-principles calculations were performed focusing on the following four typical physical quantities:

[0102] (1) The density of electronic states (DOS) of the two heterostructures;

[0103] (2) Adsorption energy of RhB on the surfaces of the two heterostructures;

[0104] (3) Charge density difference of ReS2-AgBr-PCN heterostructure;

[0105] (4) HER free energy steps under three different hydrogen absorption configurations.

[0106] These computational objects strictly correspond to the material systems in the experimental section:

[0107] DOS and structural models, corresponding to two interface configurations: AgBr NPs (15%) @pg-C3N4 and (ReS2QDs (5%) - AgBr NPs (15%)) @pg-C3N4;

[0108] Adsorption energy corresponds to the adsorption behavior of RhB at the two interfaces mentioned above.

[0109] Charge density difference is used to observe the interfacial electronic rearrangement after the introduction of ReS2.

[0110] HER step refers to the key intermediate state in the hydrogen evolution process of the same system.

[0111] 2. Calculation method

[0112] All calculations were performed within the Vienna Ab initio Simulation Package (VASP) framework, employing the projected order plus plane wave (PAW) method to describe the interaction between valence electrons and ionic cores. The exchange-correlation potential was determined using the Perdew-Burke-Ernzerhof (PBE) functional from the generalized gradient approximation (GGA), and long-range van der Waals interactions were corrected using Grimme's DFT-D3 method to ensure a reasonable description of weak interactions in layered and adsorbed systems.

[0113] The calculation parameters are set as follows:

[0114] The plane wave cutoff energy is set to 480 eV;

[0115] The energy convergence criterion for the self-consistent iteration of the Kohn-Sham equation is 10.-5 eV;

[0116] During the geometry optimization process, the residual forces on each atom converged to 0.05 eV·Å. -1 the following;

[0117] A 20 Å vacuum layer is set in the direction perpendicular to the heterojunction layer to eliminate spurious interactions between adjacent layers under periodic boundary conditions;

[0118] Visualization and analysis of electronic structure and charge distribution were performed using programs such as VASPKIT and VESTA.

[0119] The adsorption energy E_ads of RhB on different surfaces is defined as follows:

[0120] E ads =EA / B-EA-EB, where EA / B is the total energy of the A / B system formed by RhB adsorbed on substrate A, and EA and EB are the energies of the substrate and the isolated RhB molecule, respectively.

[0121] The charge density difference Δρ is defined as:

[0122] △ρ=ρA / B-ρA-ρB;

[0123] This is used to characterize the redistribution of interfacial charges after the formation of the heterojunction and after RhB adsorption, where ρA / B, ρA, and ρB are the charge densities of the heterostructure, the substrate, and the adsorbed molecules, respectively.

[0124] The Gibbs free energy change AG of the hydrogen evolution reaction (HER) intermediate is obtained through:

[0125] The energy difference is estimated by ΔG = ΔEDFT + ΔEZPE - TΔS, where ΔEDFT is the energy difference calculated by DFT, ΔEZPE and TΔS are the zero-point energy difference and entropy term, respectively, and the temperature is taken as 298.15 K.

[0126] 3. Structural Model and Geometric Configuration:

[0127] 3.1 Heterojunction Ontological Model

[0128] AgBr NPs (15%) @pg-C3N4 (abbreviated as PCN-AgBr): A binary heterostructure of AgBr nanoclusters loaded on the surface of PCN sheets (e.g. Figure 9 (as shown)

[0129] (ReS2QDs (5%) - AgBr NPs (15%))@pg-C3N4 (abbreviated as PCN-AgBr-ReS2): ReS2 quantum dots are introduced into AgBr NPs (15%)@pg-C3N4 to form a ternary heterojunction (e.g., Figure 9 (As shown). In the figure, spheres of different colors represent N, C, Re, S, Ag, Br, O, and H atoms, respectively. PCN provides the two-dimensional framework of the matrix, AgBr nanoclusters are anchored on the PCN surface, and ReS2 quantum dots together with AgBr and PCN form a multi-interface contact region.

[0130] 3.2 RhB adsorption model as follows Figure 10 As shown;

[0131] PCN-AgBr-Rhodamine-B: RhB molecules are adsorbed onto the surface of PCN-AgBr;

[0132] PCN-AgBr-ReS2-Rhodamine-B: RhB molecules are adsorbed on the surface of the ReS2-AgBr-PCN ternary structure;

[0133] Rhodamine-B single-molecule model: used to calculate the energy of isolated molecules.

[0134] These two adsorption models directly correspond to the RhB degradation system in the experimental section. They simply abstract the dye-catalyst interaction in the solution into an adsorption configuration at the solid-liquid interface, thus enabling a quantitative comparison of the effect of "presence or absence of ReS2 introduction" on the RhB adsorption strength.

[0135] 3.3 HER hydrogen absorption intermediate model as follows Figure 11 As shown;

[0136] PCN-AgBr-Ag-H: Hydrogen atoms are adsorbed at the Ag sites in the PCN-AgBr system;

[0137] PCN-AgBr-ReS2-Ag-H: In the ternary structure, hydrogen is adsorbed at the Ag site;

[0138] PCN-AgBr-ReS2-SH: Hydrogen is adsorbed at the S site of ReS2.

[0139] These three configurations are used to compare the thermodynamic advantages of different active sites (S on Ag or ReS2) in HER. All models fully relax under the aforementioned DFT parameters, and the final geometric configurations are stable without significant structural collapse, indicating that these heterostructures are theoretically feasible.

[0140] 4. The electronic structure and electronic density of states of PCN-AgBr and PCN-AgBr-ReS2 were analyzed, and the results are as follows: Figure 12 As shown;

[0141] Depend on Figure 12 As can be seen, for the PCN-AgBr model, the system exhibits typical narrow bandgap semiconductor characteristics, with relatively limited density of states in the valence and conduction bands near the Fermi level. This is consistent with the typical observations of single g-C3N4 or g-C3N4 / AgBr systems. For the PCN-AgBr-ReS2 model, the introduction of ReS2 significantly enhances the density of states (DOS) near the Fermi level, indicating that the system has more electronic states that can participate in conduction and interfacial reactions. Theoretically, this is more conducive to the transport of photogenerated electrons at the interface and their participation in reduction reactions. In short, from the perspective of DOS, the introduction of ReS2 is equivalent to "superimposing" another layer of electronic channels that can participate in conduction and reactions on the PCN-AgBr structure, enabling the system to transition from a relatively "sparse" semiconductor density of states to a state with a higher density of electronic states near the Fermi level. This is consistent with the higher hydrogen production rate observed later.

[0142] 5. The adsorption energy of PCN-AgBr and PCN-AgBr-ReS2 on RhB and the interfacial interaction were studied, and the results are shown in Table 1.

[0143] Table 1

[0144] configuration Total Energy / ev Base energy / ev Intramolecular energy / ev Adsorption energy / ev PCN-AgBr-Rhodamine-B -913.759 -508.530 -403.796 -1.433 <![CDATA[PCN-AgBr-ReS2-Rhodamine-B]]> -1051,446 -645.522 -403.796 -2.128

[0145] Table 1 shows that the adsorption energy difference between the two is approximately 0.695 eV, and the adsorption energy of RhB in the ternary structure is more negative. This indicates that the ternary structure has a stronger "grabbing ability" for RhB. Thermodynamically, a more negative adsorption energy means that RhB has higher stability on the PCN-AgBr-ReS2 surface, and the molecules are more easily adsorbed onto the catalyst surface, increasing the probability of contact with active sites. This is beneficial for subsequent electron transfer and bond activation. The stronger interaction between RhB and the substrate surface usually means that its π system or charged functional groups are tightly coupled with the surface, which provides a better electron transport channel and geometric environment for subsequent photogenerated electrons / holes to attack CN, C=C, and other bonds in the RhB molecule. This is consistent with the higher RhB degradation rate observed in the experiment. The experimental results have shown that PCN-AgBr-ReS2 has the highest degradation efficiency and apparent rate constant for RhB, while the theoretical adsorption energy results provide a reasonable explanation at the fundamental level: the same RhB Molecules "stick together more firmly" in ternary structures than in binary structures, making them more likely to undergo continuous photocatalytic oxidation processes. Therefore, the specific data of "-1.433 eV vs -2.128 eV" is the core quantitative basis for connecting the link of "structural design RhB adsorption → experimental degradation activity".

[0146] 6. Charge density difference of PCN-AgBr-ReS2: interfacial electron rearrangement, such as Figure 13 As shown, by Figure 13 It is evident that significant electron transfer occurs at the interface. Regardless of which atoms the enriched / depleted regions are located around, the pairing of green and yellow regions near the heterojunction interface indicates a clear charge redistribution among ReS2, AgBr, and PCN. Electron density increases in some regions and decreases in others. This is a typical characteristic of heterojunction formation.

[0147] Providing conditions for the separation of built-in electric fields and space charges, when electron enrichment and depletion occur on both sides of the interface, a localized built-in electric field with a certain direction can be formed. This electric field is conducive to the spatial separation of photogenerated electrons and holes; electrons are "pulled" towards the enriched side, while holes are more likely to remain on the opposite side. Combining this with the changes in DOS mentioned earlier, it is reasonable to assume that the introduction of ReS2 not only changes the density of states distribution but also reconstructs the charge distribution at the interface scale, which helps to achieve more efficient carrier separation under external illumination conditions.

[0148] These observations corroborate the experimental findings of PL quenching, photocurrent enhancement, and EIS semicircle radius reduction; the experiment "sees" changes in macroscopic charge behavior, while the DFT charge density difference provides direct evidence at the microscopic level.

[0149] 7. The HER free energy steps and active sites of PCN-AgBr and PCN-AgBr-ReS2 were analyzed, and the results are as follows: Figure 14 As shown,

[0150] Depend on Figure 14 It can be seen that the three curves correspond to "Ag sites in the pure PCN-AgBr system", "Ag sites in the ternary structure", and "S sites of ReS2 in the ternary structure", respectively.

[0151] Compared with 1-PCN-AgBr-Ag-H, the two curves starting with "2-" have lower overall free energy changes, indicating that after the introduction of ReS2, the intermediate steps of HER are thermodynamically more favorable regardless of whether hydrogen is adsorbed at the Ag or S site.

[0152] One of the curves shows a particularly small change in free energy during the key step of "hydrogen adsorption-hydrogen desorption," exhibiting characteristics closer to "thermodynamically neutral adsorption." This is consistent with the conclusion that ReS2 and its S site are considered excellent HER active sites in various reports.

[0153] Therefore, the information provided by the HER step diagram can be summarized as follows:

[0154] (1) With only the binary structure of PCN-AgBr, at least one key step in HER has a relatively large free energy change, which limits the overall hydrogen evolution kinetics.

[0155] (2) After the introduction of ReS2, several active sites on the ternary heterojunction (especially ReS2-related sites) significantly reduced the free energy change of this step, making the entire HER pathway closer to the "optimal paradigm".

[0156] (3) This is highly consistent with the phenomenon in the hydrogen production experiment that “only ReS2 or AgBr modification alone can bring limited improvement, while the hydrogen production rate is highest when ReS2+AgBr is co-modified.”

[0157] 8. pg-C3N4, AgBr NPs (20%)@pg-C3N4, and (AgBr NPs (20%)-ReS2QDs (5% by mass))@pg-C3N4 were obtained according to the preparation method of the examples; ReS2QDs (5%)@pg-C3N4 were obtained according to the method of Comparative Example 2;

[0158] The hydrogen production performance and photon utilization efficiency of the above materials were tested, and the hydrogen evolution rate per unit mass of catalyst was as follows: Figure 15 As shown, the X-axis represents different types of photocatalytic materials. The Y-axis represents the H2 generation rate, in nmol·h⁻¹. -1·g -1 nmol: nanomolar, a unit representing the amount of hydrogen produced. Hourly: indicates the rate. Per gram of catalyst: This value represents the rate expressed per unit mass (1 gram) of catalyst, a common method for assessing the intrinsic activity of a catalyst, facilitating fair comparisons of samples of different masses.

[0159] Depend on Figure 15 It can be seen that the pg-C3N4 base material exhibits the lowest activity, approximately 1500 nmol·h⁻¹. -1 ·g -1 This indicates that its catalytic efficiency is limited when used alone. Loading only ReS2 quantum dots: Performance improved, but not significantly. Loading only AgBr: Performance improved significantly, more than three times that of pure pg-C3N4. This indicates that AgBr can effectively promote charge separation or broaden light absorption. Co-loading (AgBr + ReS2 quantum dots): Performance peaked, far exceeding any single modified sample. This indicates a "synergistic effect" between AgBr and ReS2 quantum dots. They may have constructed a more efficient charge transfer pathway, thereby maximally suppressing electron-hole recombination and improving photocatalytic hydrogen production efficiency.

[0160] The total hydrogen production rate histogram is as follows: Figure 16 As shown, this graph compares the hydrogen production capacity of different materials at different time points. X-axis: represents time (hours), from 1 to 6. Y-axis: represents the hydrogen production rate, in µmol·g. -1 A higher value indicates a stronger hydrogen production capacity.

[0161] Depend on Figure 16 It was observed that the hydrogen production rate of all materials continuously increased from 1 hour to 6 hours. At each time point, the purple material (AgBr (20%) + ReS2 quantum dots (5%) @ pg-C3N4) exhibited the highest hydrogen production rate. This was particularly evident at 6 hours, where its performance significantly outperformed other materials. Pure pg-C3N4 (brown) showed the lowest rate, confirming that the addition of AgBr and ReS2 quantum dots significantly enhances hydrogen production. In summary, the AgBr (20%) + ReS2 quantum dots (5%) @ pg-C3N4 material system exhibited the best hydrogen production performance, with its rate increasing with reaction time.

[0162] The relationship between hydrogen formation rate and reaction time of AgBr(20%) + ReS2QDs(5%)@pg-C3N4 under different conditions is as follows: Figure 17As shown, the X-axis (horizontal axis) represents the reaction time (h), indicating the duration of the photocatalytic reaction (hours), ranging from 0 to 30 hours. The Y-axis (vertical axis) represents the H2 generation rate (µmol·g⁻¹). -1 The value represents the amount of hydrogen produced per gram of the composite material during the reaction, expressed in micromoles per gram (µmol·g). -1 This is the core indicator for evaluating the efficiency of photocatalytic hydrogen production.

[0163] Multiple curves (different colors): Black, red, blue, green and purple curves represent the performance of the same material in multiple repeated experimental cycles (e.g., cycle 1, cycle 2, ..., up to cycle 5).

[0164] Depend on Figure 17 As can be seen from each curve, the hydrogen production rate increases significantly with the passage of reaction time (e.g., from 0 μmol·g at 0 hours). -1 Increased to approximately 20,000 μmol·g over about 6 hours. -1 This indicates that the material can continuously and efficiently generate hydrogen throughout the entire photocatalytic reaction process.

[0165] Material stability: The hydrogen production rate-time curves of different colors almost completely overlapped, and the final hydrogen production all converged to approximately 20,000 μmol·g. -1 The results show that the hydrogen production performance of this composite material is highly repeatable and stable, with minimal differences between multiple experimental runs.

[0166] An AQE test was performed on (AgBr NPs (20%) - ReS2QDs (5%))@pg-C3N4, and the results are as follows: Figure 18 As shown, the X-axis represents light of different wavelengths (410 nm, 450 nm, etc.), indicating the irradiation conditions under which the test was conducted. The Y-axis represents AQE (%) – apparent quantum efficiency. This is the core indicator for measuring the efficiency of photocatalytic materials in converting photons into hydrogen.

[0167] Depend on Figure 18It can be seen that as the irradiation wavelength increases from 410 nm (meaning a decrease in light energy), the AQE gradually decreases (from 13% at 410 nm to 7% at 610 nm). This indicates that the material has a higher utilization efficiency for short-wavelength (high-energy) light. Material characteristics: An AQE of 13% under 410 nm illumination is considered a high efficiency level in the field of photocatalytic hydrogen production, proving the excellent light utilization performance of this composite material; It shows that (AgBr NPs (20%)-ReS2QDs (5%))@pg-C3N4 exhibits good photon utilization efficiency at different light wavelengths, and the response to short-wavelength light is particularly strong, thus confirming that it is a high-performance photocatalytic material.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a nanocomposite photocatalytic material, characterized in that, The preparation method includes the following steps: (a) Melamine is ground, then cyanuric acid is added and ground again. Then, anhydrous ethanol is added and stirred and ultrasonically treated. After drying, a precursor is obtained. The precursor is ground into powder and heated to 450~550℃ for calcination, cooling, grinding into powder, and drying to obtain porous carbon nitride. (b) Porous carbon nitride was added to deionized water and stirred. Silver nitrate solution was then added and stirred to obtain a dispersion. Potassium bromide solution was added dropwise to the dispersion and stirred for a period of time. After filtration, washing, calcination, and grinding, a composite material of porous carbon nitride and silver bromide nanoparticles was obtained. (c) Grind rhenium disulfide powder and add N-methylpyrrolidone to mix well to obtain a mixture. The mixture is then subjected to ultrasonic crushing and centrifugation. The supernatant is collected to obtain a rhenium disulfide quantum dot dispersion. (d) The composite material of porous carbon nitride and silver bromide nanoparticles is added to deionized water and stirred for a period of time. Then, rhenium disulfide quantum dot dispersion is added and stirred for a period of time. After freeze drying and baking, the nanocomposite photocatalytic material is obtained.

2. The preparation method according to claim 1, characterized in that, In step (a), the mass ratio of melamine to cyanuric acid is (2~3):

1.

3. The preparation method according to claim 1, characterized in that, In step (a), the heating rate is 1.8~2.2℃ / min, and the calcination time is 4~6h.

4. The preparation method according to claim 1, characterized in that, In step (b), the calcination temperature is 120~140℃ and the time is 18~25h; the mass content of silver bromide nanoparticles in the composite material of porous carbon nitride and silver bromide nanoparticles is 5%~20%.

5. The preparation method according to claim 1, characterized in that, In step (c), the ultrasonic power is 160~200W and the time is 8~12h; the centrifugation includes first centrifuging at 3500~4500rpm for 15~25min, collecting the supernatant, and then centrifuging at 12000~14000rpm for 15~25min.

6. The preparation method according to claim 1, characterized in that, In step (d), the mass percentage of rhenium disulfide quantum dots in the nanocomposite photocatalytic material is 1% to 10%.

7. The nanocomposite photocatalytic material prepared by any one of claims 1 to 6.

8. The application of the nanocomposite photocatalytic material prepared by any one of claims 1 to 6 in the photocatalytic degradation of organic matter.

9. The application of the nanocomposite photocatalytic material prepared by any one of claims 1 to 6 in wastewater treatment.

10. The application of the nanocomposite photocatalytic material prepared by any one of claims 1 to 6 in photocatalytic hydrogen production.

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