Graphite nitride and carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles as well as preparation method and application of graphite nitride and carbon nitride bifunctional photocatalyst

Abstract

The invention discloses a graphite nitride and carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles as well as a preparation method and application of the graphite nitride and carbon nitride bifunctional photocatalyst, and belongs to the technical field of catalyst preparation. According to the preparation method disclosed by the invention, Mn nanoparticles are successfully loaded on g-C3N5 through photodeposition and annealing, so that the bifunctional catalyst is obtained. Mn as an additional load of an oxidation reaction active site can effectively prevent recombination of photo-induced electrons and holes, so that the oxidation reaction can be greatly promoted, the dynamic balance between the oxidation reaction and the reduction reaction is promoted, the reduction reaction efficiency is further improved, and the photocatalytic activity is greatly improved. The photocatalyst is applied to photocatalytic reaction with water and furfuryl alcohol as reaction substrates, the performance of photocatalytic reduction hydrogen production can be improved under the condition that no sacrificial reagent is additionally added, meanwhile, the added furfuryl alcohol can be oxidized into furfural with higher utilization value, and the aim of achieving the oxidation-reduction dual functions at the same time is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly to a bifunctional photocatalyst of graphitic carbon nitride loaded with Mn nanoparticles, and a preparation method and application thereof. Background Art

[0002] Due to the growing energy demand and the environmental hazards caused by the combustion of fossil fuels, people are urgently looking for renewable energy sources. Among them, hydrogen (H 2 ) is considered as a major alternative resource to fossil fuels because of its zero emissions and high energy. Among the many conversion methods of H 2 , the use of photocatalytic technology to decompose water to produce H 2 while selectively synthesizing organic compounds for the manufacture of chemicals and carbon-containing fuels is widely regarded as a feasible method to solve the problems of energy shortage and environmental pollution.

[0003] Graphitic carbon nitride (g-C 3 N 4 ) has been highly regarded because of its strong stability, special electronic structure and easy manufacturability, and has become a promising catalyst for the two-electron oxygen reduction reaction (2e - @ORR). However, g-C 3 N 4 faces challenges such as a limited light absorption range and suboptimal electronic conductivity, which seriously hinder its catalytic ability. Compared with g-C 3 N 4 , graphitic carbon nitride (g-C 3 N 5 ) has attracted considerable attention due to its enhanced electron-donating sites and basic nitrogen content. And theoretically, introducing supplementary nitrogen into the triazine unit of g-C 3 N 5 expands its conjugated structure, improves its thermodynamic stability, electronic properties, and narrows the band gap. The loading of metal cocatalysts can effectively enhance the photocatalytic activity, but currently, it is still challenging to modify g-C 3 N 5 with metal cocatalysts.

[0004] Although it is currently possible to use photoexcited electrons to induce proton reduction to generate H 2 , due to the slow reaction kinetics, the oxidative half-reaction that tends to generate oxygen (O 2 ) using holes is difficult to proceed rapidly, resulting in a slowdown or even inhibition of the entire water splitting process. Similarly, in the CO 2 reduction reaction, the presence of O 2 and H 2 O may limit CO by accepting electrons and generating a series of reactive oxygen species (ROS) harmful to the system.2 Therefore, to solve these problems, the most common strategy is to use a variety of sacrificial reagents (such as methanol, triethanolamine (TEOA), sodium sulfite, lactic acid and ascorbic acid, etc.) as hole scavengers or electron donors to increase the H 2 The yield or promotion of CO 2 photoreduction; however, the consumption of sacrificial reagents is itself a process that uses chemical energy, and the oxidation products produced in this process are often useless, so that the beneficial resources obtained through photocatalysis are less than those required to produce the sacrificial reagents.

[0005] Therefore, in order to effectively improve the photocatalytic efficiency and charge separation, how to design gC 3 N 5 Nanosheets, and the realization of the dual functions of reduction and oxidation, and the reduction of the consumption of sacrificial reagents, still need further research.

[0006] Precious metals such as gold (Au), silver (Ag), and platinum (Pt) are often used as co-catalysts to quickly receive and transmit photogenerated electrons during the photocatalytic process due to their excellent electron mobility and conductivity, as well as good chemical stability and corrosion resistance, thereby improving the efficiency of photocatalytic reduction. In recent years, researchers have achieved the use of metal co-catalysts in gC 3 N 5 load on the gC 3 N 5 The special pore structure and coordination bonds are used to load palladium (Pd) or Pt, and Pt nanoparticles are loaded by electrostatic adsorption. However, due to the characteristics of these precious metals, they can only improve the reduction performance during the photocatalytic process, but have little effect on the oxidation performance. It is worth noting that the oxidation reaction and reduction reaction in the photocatalytic reaction are interrelated and together constitute a dynamic equilibrium. According to the principle of chemical equilibrium, even if the reduction rate is improved after material modification, if the oxidation reaction rate is too slow, it will still cause the entire reaction system to move in a direction that is not conducive to the reduction reaction, thereby reducing the reduction rate. Therefore, it is extremely important to improve the oxidation performance of the photocatalyst in the reaction.

[0007] The main shortcomings of the prior art are as follows:

[0008] (1) For gC 3 N 5 The utilization of photocatalytic materials is mainly based on nanoparticles. This leads to insufficient contact between the material and the reaction substrate during the reaction, reduces the exposure of effective photocatalytic reaction sites, and greatly reduces the catalytic performance.

[0009] (2) The loading of the normal metal cocatalyst is unstable and prone to shedding. Due to the inherent properties between the metal cocatalyst and g-C 3 N 5 there is no strong interaction between the metal cocatalyst and the host material, but it exists in large quantities in the solution, greatly reducing the loading amount.

[0010] (3) Currently, the loading of metal cocatalysts mainly focuses on using noble metals to improve the photocatalytic reduction performance, while the use of metal loading to improve the oxidation performance is ignored. Oxidation and reduction reactions are interrelated, and an overly slow oxidation reaction often becomes the rate-limiting reaction for the overall photocatalytic reaction rate, resulting in a decrease in the reduction rate.

[0011] (4) To improve the photocatalytic reduction performance, high-value sacrificial reagents are usually used. However, the sacrificial reagents themselves are valuable chemicals, and extensive use may even lead to a situation where the value of the photocatalytic products is less than that of the consumed sacrificial reagents.

[0012] (5) Most semiconductor photocatalytic materials can only achieve one application of reduction or oxidation. Currently, there are few design ideas for realizing dual-functional applications by simultaneously utilizing the oxidation and reduction effects of semiconductor materials.

[0013] (6) Currently, the products generated by selective biomass photoreforming are single.

[0014] Based on this, it is very necessary to develop a new method to achieve the stable loading of metal cocatalysts on the surface of g-C 3 N 5 and obtain a catalyst with oxidation and reduction dual functions. SUMMARY OF THE INVENTION

[0015] The purpose of the present invention is to provide a dual-functional photocatalyst of graphitic carbon nitride loaded with Mn nanoparticles and its preparation method and application to solve the problems existing in the above-mentioned prior art.

[0016] To achieve the above purpose, the present invention provides the following solutions:

[0017] One of the technical solutions of the present invention: A dual-functional photocatalyst of graphitic carbon nitride (g-C 3 N 5 ) loaded with Mn nanoparticles, including a graphitic carbon nitride carrier and Mn nanoparticles loaded on the graphitic carbon nitride carrier;

[0018] The loading amount of the Mn nanoparticles is 1-7 wt%.

[0019] The Mn element (Mn nanoparticles) under special conditions in the photocatalyst has multiple oxidation states. Therefore, during the photocatalytic process, it can transfer electrons through the rapid conversion between different oxidation states, preferentially acting as an electron acceptor to receive photo-generated holes, effectively separating photo-generated carriers, and then leaving behind photo-generated holes with strong oxidizing properties, which participate in the oxidation reaction to enhance the oxidation performance. Moreover, Mn has multiple stable oxidation states, enabling it to more effectively serve as an electron transfer medium, promoting the separation of photo-generated carriers during the process of receiving and transferring photo-generated holes, providing more active sites for the oxidation reaction, and thus improving the oxidation performance. In contrast, the oxidation state changes of some other transition metals (such as Fe, Co, Ni, etc.) may be relatively single or the redox reaction rate is slower. Therefore, the loading of Mn nanoparticles can improve the oxidation reaction efficiency, and at the same time provide additional active sites for the oxidation reaction, promoting the dynamic balance between the oxidation reaction and the reduction reaction, and further driving the reduction reaction efficiency. Additionally, the interaction between the loaded Mn nanoparticles and the unsaturated coordinated N atoms in g-C 3 N 5 itself can effectively separate photo-generated electron-hole pairs, increase the visible light response while improving the photocatalytic performance, making the obtained photocatalyst have strong visible light catalytic performance. When applied to the photocatalytic reaction with water and furfuryl alcohol as reaction substrates, it can improve the performance of photocatalytic hydrogen production by reduction without adding sacrificial reagents additionally. At the same time, the added furfuryl alcohol can be oxidized to furfural with higher utilization value, achieving the goal of simultaneously achieving oxidation and reduction dual functions.

[0020] Furthermore, the loading amount of the Mn nanoparticles is preferably 5 wt%.

[0021] The second technical solution of the present invention: A preparation method of the above-mentioned dual-functional photocatalyst of graphitic carbon nitride loaded with Mn nanoparticles, comprising the following steps:

[0022] Disperse graphitic carbon nitride in water to obtain a graphitic carbon nitride suspension; drop Mn 2+ solution into the graphitic carbon nitride suspension, first stir and react under dark conditions, and then age and react under light conditions to obtain a precursor; perform annealing treatment on the precursor to obtain the dual-functional photocatalyst of graphitic carbon nitride loaded with Mn nanoparticles (abbreviated as Mn / g-C 3 N 5 ).

[0023] The present invention successfully loaded Mn nanoparticles on g-C 3 N 5 through photodeposition and annealing. First, through the photodeposition method, metal ions (i.e., Mn 2+) It undergoes a reduction reaction with the photo-generated electrons produced by the catalyst, causing metal ions to be reduced to metal atoms on the surface of the photocatalyst and deposited uniformly. As the reaction progresses, more metal atoms continue to deposit and gradually aggregate to form metal particles at the nanoscale, which are evenly distributed on the surface of the photocatalyst. Subsequently, annealing can, on the one hand, eliminate some lattice defects and stresses that may be generated during the photo-deposition process, making the crystal structures of the photocatalyst and the metal more stable; on the other hand, appropriate annealing temperature and time can promote the formation of better chemical bonding between the metal particles and the photocatalyst, enhancing the interaction between the metal and the photocatalyst, thereby improving the performance of the photocatalyst. Therefore, in the Mn nanoparticle-loaded graphitic carbon nitride bifunctional photocatalyst obtained by this method, the loading of Mn nanoparticles is more uniform and stable and not easily detached.

[0024] Furthermore, both the graphitic carbon nitride and the Mn nanoparticle-loaded graphitic carbon nitride bifunctional photocatalyst are in a layered flaky structure (i.e., a lamellar structure).

[0025] Compared with non-flaky materials, such as materials with irregular morphologies like bulk materials, flaky materials have a larger specific surface area, can come into contact with reaction substrates more fully, and the transfer rate of photo-generated charges between layers is faster, thereby enhancing the reactivity of the reaction.

[0026] Furthermore, the dosage ratio of the graphitic carbon nitride to water is 50 - 200 mg: 30 - 100 mL.

[0027] Furthermore, the Mn 2+ solution includes manganese chloride (MnCl 2 ), manganese nitrate (Mn(NO 3 )) 2 solution, and manganese sulfate (MnSO 4 ) solution; the concentration of the Mn 2+ solution is 0.01 - 0.1 mol·L -1 .

[0028] Furthermore, the dosage ratio of the graphitic carbon nitride suspension to the Mn 2+ solution is 30 - 100 mL: 100 - 3000 μL.

[0029] Furthermore, the reaction time for stirring the reaction under dark conditions is 1 - 5 h; the reaction time for aging the reaction under light conditions is 1 - 5 h.

[0030] Furthermore, the conditions of the light include: the wavelength of the light is less than 420 nm, greater than or equal to 420 nm, or full spectrum.

[0031] Further, the light source of the illumination is an ultraviolet mercury lamp (providing light with a wavelength less than 420 nm) or a 300-W xenon lamp (providing light with a wavelength greater than or equal to 420 nm or full-spectrum light), that is, the aging reaction under the illumination condition is specifically an aging reaction under the irradiation of an ultraviolet mercury lamp or a xenon lamp.

[0032] Further, after the aging reaction, there are also steps of filtration, washing, and vacuum drying. After vacuum drying, a precursor powder (denoted as Mn x / g-C 3 N 5 powder) is obtained, where Mn X represents that Mn may have multiple valence states, and all are converted to the 0-valence state after subsequent annealing treatment); the temperature of the vacuum drying is 20 - 80 °C, and the time is 5 - 10 h.

[0033] Further, the conditions of the annealing treatment include: the annealing atmosphere is air, hydrogen, nitrogen, argon (Ar), or a hydrogen-argon mixed atmosphere, the annealing temperature is 100 - 300 °C, and the annealing time is 1 - 5 h.

[0034] The third technical solution of the present invention: Application of the above-mentioned graphite carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles in photocatalytic water splitting for hydrogen production by reduction coupling (the meaning of coupling is simultaneous) with the oxidation of furfuryl alcohol to produce furfural.

[0035] Further, the steps of photocatalytic water splitting for hydrogen production by reduction coupling with the oxidation of furfuryl alcohol to produce furfural include: mixing the graphite carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles with water and furfuryl alcohol, evacuating, and then reacting under the illumination condition.

[0036] The present invention discloses the following technical effects:

[0037] The present invention has successfully loaded Mn nanoparticles on g-C 3 N 5 by photodeposition and annealing, and finally prepared a Mn / g-C 3 N 5 bifunctional photocatalytic material with high visible light response activity. The results of photocatalytic water splitting for hydrogen production and coupling with the oxidation of furfuryl alcohol to produce furfural show that the visible light photocatalytic activity of the Mn / g-C 3 N 5 material is significantly enhanced, which can meet the function of simultaneously generating green energy and converting high-value chemicals in photocatalytic reduction reactions and oxidation reactions. Among them, 5-Mn / g-C 3 N 5 has the best performance, and its hydrogen production rate is 3.5 times that of pure g-C 3 N 5 , and the conversion rate of furfuryl alcohol oxidation to furfural is that of pure g-C3 N 5 2.7 times that of. And it has good photocatalytic cycle stability and has certain application value in two application directions of photocatalytic hydrogen evolution and conversion of furfuryl alcohol into high-value chemicals. The photocatalytic material prepared by this preparation method has high photocatalytic efficiency, and has good effects on visible-light photocatalytic water splitting to produce hydrogen and oxidation conversion of furfuryl alcohol. In addition, the preparation method of the present invention has low requirements for equipment, resulting in low investment cost for mass production, which is beneficial to practical application. The advantages of the present invention compared with the prior art are specifically as follows:

[0038] (1) Compared with the prior art, using non-precious metal Mn as a co-catalyst itself reduces the preparation and development cost of the catalyst. Secondly, after loading, Mn can bond with the unsaturated coordinated N atoms on g-C 3 N 5 to form a bond, making the combination tighter and not easy to fall off, greatly expanding the applicable range of the metal co-catalyst loaded on the surface of g-C 3 N 5 and having universality;

[0039] (2) The loaded Mn nanoparticle / graphitic carbon nitride bifunctional photocatalyst Mn / g-C 3 N 5 prepared by the present invention has broad light absorption and a narrower band gap. In addition, the flaky microstructure increases the surface area of contact between the catalyst and the reaction substrate. The loading of Mn as an additional oxidation reaction active site can effectively prevent the recombination of photo-generated electrons and holes, which can greatly promote the progress of the oxidation reaction, promote the dynamic balance between the oxidation reaction and the reduction reaction, and further drive the reduction reaction efficiency, thereby greatly improving the photocatalytic activity. The hydrogen production rate of the 5-Mn / g-C 3 N 5 sample can reach 567.8 μmol·g -1 ·h -1 , and the yield of furfural obtained by the oxidation of furfuryl alcohol can reach 595.6 μmol·g -1 ·h -1 , which are 3.5 times and 2.7 times higher than those of pure g-C 3 N 5 respectively.

[0040] (3) The hydrogen produced by the method of the present invention is green hydrogen, which is not only environmentally friendly and pollution-free, but also has great application prospects. Similarly, furfural, as one of the main production raw materials of high-value chemicals, also has great utilization value. For example, the furfural obtained by the photocatalytic reaction can be subjected to a polycondensation reaction with tannin to produce a green bioadhesive that meets the national adhesion strength standard. Description of the Drawings

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0042] Figure 1 For Comparative Example 1, g-C prepared in Example 1, Example 2, Example 3, and Example 4 3 N 5 nanosheets, 1-Mn / g-C 3 N 5 、3-Mn / g-C 3 N 5 、5-Mn / g-C 3 N 5 and 7-Mn / g-C 3 N 5 X-ray diffraction patterns (XRD);

[0043] Figure 2 For the 5-Mn / g-C prepared in Example 3 3 N 5 photocatalyst and the g-C prepared in Comparative Example 1 3 N 5 nanosheets SEM images, where (a) and (b) are 5-Mn / g-C 3 N 5 , (c) and (d) are g-C 3 N 5 nanosheets;

[0044] Figure 3 For the 5-Mn / g-C prepared in Example 3 3 N 5 photocatalyst TEM images, where (a) is a high-resolution TEM image, and (b)-(d) are low-resolution TEM images;

[0045] Figure 4 For the 5-Mn / g-C prepared in Example 3 3 N 5 photocatalyst and the g-C prepared in Comparative Example 1 3 N 5 XPS test results, where (a) is the total X-ray photoelectron spectroscopy spectrum (XPS-Survey) of the two, (b) is the high-resolution XPS C 1s spectrum of the two, (c) is the XPS N 1s spectrum of the two, and (d) is the XPS Mn 2p spectrum of 5-Mn / g-C 3 N 5 ;

[0046] Figure 5 The 5-Mn / g-C prepared for Example 3 3 N 5 photocatalyst and the g-C prepared for Comparative Example 1 3 N 5 electron spin resonance (ESR) spectra of the nanosheets, where (a) is the intensity of the hydroxyl radicals (·OH) generated by the two under different illumination times, and (b) is the intensity of the superoxide radicals (·O 2- ) generated;

[0047] Figure 6 For the g-C prepared in Comparative Example 1 3 N 5 nanosheets and the 3-Mn / g-C prepared in Examples 2-4 3 N 5 、5-Mn / g-C 3 N 5 and 7-Mn / g-C 3 N 5 Test results of the bifunctional photocatalytic performance of photocatalysts for photocatalytic water splitting reduction to produce hydrogen and simultaneously photocatalytic oxidation of furfuryl alcohol to produce furfural, where (a) is the graph of the change in the photocatalytic water splitting hydrogen production curve, and (b) is the bar graph of the coupling performance of the hydrogen production efficiency and the efficiency of furfuryl alcohol conversion to furfural;

[0048] Figure 7 For the g-C prepared in Comparative Example 1 3 N 5 nanosheets, the 5-Mn / g-C prepared in Example 3 3 N 5 、the 5-Fe / g-C prepared in Comparative Example 3 3 N 5 、the 5-Co / g-C prepared in Comparative Example 4 3 N 5 and the 5-Ni / g-C prepared in Comparative Example 5 3 N 5 Test results of the bifunctional photocatalytic performance of photocatalysts for photocatalytic water splitting reduction to produce hydrogen and simultaneously photocatalytic oxidation of furfuryl alcohol to produce furfural;

[0049] Figure 8 For the 5-Mn / g-C prepared in Example 3 3 N 5 hydrogen production cycle diagram;

[0050] Figure 9 For the 5-Mn / g-C prepared in Example 3 3 N 5 XRD diagrams before and after the photocatalytic reaction;

[0051] Figure 10 5-Mn / g-C prepared for Example 3 3 N 5 XPS-Survey spectra before and after the photocatalytic reaction;

[0052] Figure 11 Schematic diagram of the principle of photocatalytic water splitting for hydrogen production by reduction coupling with the oxidation of furfuryl alcohol to furfural over the bifunctional photocatalyst of graphitic carbon nitride loaded with Mn nanoparticles in the present invention. Detailed Description of the Invention

[0053] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0054] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0055] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0056] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0057] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0058] It should be noted that the aspects not detailed in the present invention are all conventional operating means in the art and are not the focus of the present invention.

[0059] As a first aspect of the present invention, the present invention provides a bifunctional photocatalyst of manganese nanoparticles loaded on graphitic carbon nitride (g-C 3 N 5 ), which comprises a graphitic carbon nitride support and manganese nanoparticles loaded on the graphitic carbon nitride support;

[0060] The loading amount of the manganese nanoparticles is 1-7 wt%.

[0061] The meaning of the loading amount is: the mass of the loaded manganese nanoparticles / the mass of the g-C 3 N 5 support × 100%.

[0062] As a second aspect of the present invention, the present invention provides a preparation method of the above-mentioned bifunctional photocatalyst of manganese nanoparticles loaded on graphitic carbon nitride, comprising the following steps:

[0063] Disperse graphitic carbon nitride in water to obtain a graphitic carbon nitride suspension; drop a Mn 2+ solution into the graphitic carbon nitride suspension, first stir and react under dark conditions, and then age and react under light conditions to obtain a precursor; perform annealing treatment on the precursor to obtain the bifunctional photocatalyst of manganese nanoparticles loaded on graphitic carbon nitride (abbreviated as Mn / g-C 3 N 5 ).

[0064] As a preferred embodiment of the present invention, both the graphitic carbon nitride and the bifunctional photocatalyst of manganese nanoparticles loaded on graphitic carbon nitride are in a layered sheet structure (i.e., a lamellar structure).

[0065] As a preferred embodiment of the present invention, the dosage ratio of the graphitic carbon nitride to water is 50-200 mg: 30-100 mL.

[0066] As a preferred embodiment of the present invention, the Mn 2+ solution includes manganese chloride solution, manganese nitrate solution and manganese sulfate solution; the concentration of the Mn 2+ solution is 0.01-0.1 mol·L -1 .

[0067] As a preferred embodiment of the present invention, the dosage ratio of the graphitic carbon nitride suspension to the Mn 2+ solution is 30-100 mL: 100-3000 μL.

[0068] As a preferred embodiment of the present invention, the reaction time of the stirring reaction under dark conditions is 1-5 h; the reaction time of the aging reaction under light conditions is 1-5 h.

[0069] As a preferred embodiment of the present invention, the conditions of the light irradiation include: the wavelength of the light is less than 420 nm, greater than or equal to 420 nm, or full spectrum.

[0070] As a preferred embodiment of the present invention, the light source for the light irradiation is an ultraviolet mercury lamp (providing light with a wavelength less than 420 nm) or a 300 W xenon lamp (providing light with a wavelength greater than or equal to 420 nm or full spectrum).

[0071] As a preferred embodiment of the present invention, after the aging reaction, the steps further include filtration, washing, and vacuum drying. After vacuum drying, a precursor powder (i.e., Mn x / g-C 3 N 5 powder) is obtained; the temperature of the vacuum drying is 20 - 80 °C, and the time is 5 - 10 h.

[0072] As a preferred embodiment of the present invention, the conditions of the annealing treatment include: the annealing atmosphere is air, hydrogen, nitrogen, argon, or a hydrogen-argon mixed atmosphere, the annealing temperature is 100 - 300 °C, and the annealing time is 1 - 5 h.

[0073] As an embodiment of the present invention, the graphitic carbon nitride can be obtained by purchase or prepared by an existing preparation method of graphitic carbon nitride.

[0074] As a preferred embodiment of the present invention, the preparation steps of the graphitic carbon nitride include: mixing 3-amino-1,2,4-triazole, KCl, and KOH and grinding them to obtain a mixture; calcining the mixture, and after the calcination is completed, cooling, washing, and vacuum drying to obtain the graphitic carbon nitride;

[0075] The mass ratio of 3-amino-1,2,4-triazole, KCl, and KOH is 12:18:1; the temperature of the calcination is 550 °C, and the time is 4 h.

[0076] As a third aspect of the present invention, the present invention provides the application of the above-mentioned graphitic carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles in the photocatalytic water splitting reduction hydrogen production coupling (the meaning of coupling is simultaneous) with the oxidation of furfuryl alcohol to form furfural.

[0077] As a preferred embodiment of the present invention, the steps of photocatalytic water splitting reduction hydrogen production coupling with the oxidation of furfuryl alcohol to form furfural include: mixing the graphitic carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles with water and furfuryl alcohol, evacuating, and then reacting under light irradiation conditions.

[0078] Schematic diagram of the principle of photocatalytic water splitting reduction to produce hydrogen and the coupling of furfuryl alcohol oxidation to produce furfural by the bifunctional photocatalyst of Mn nanoparticle-loaded graphitic carbon nitride Figure 11 is shown. Furfural alcohol derived from biomass materials was added to the photocatalytic reaction system to replace the use of ordinary sacrificial reagents. While enhancing the hydrogen production performance, it also generated the more valuable chemical furfural through the photocatalytic oxidation reaction.

[0079] As a preferred embodiment of the present invention, the dosage ratio of the Mn nanoparticle-loaded graphitic carbon nitride bifunctional photocatalyst, water, and furfuryl alcohol is 50 mg: 80 - 95 mL: 5 - 20 mL, where the total volume of water and furfuryl alcohol is ensured to be constant at 100 mL; the light source used during the reaction is a 300 W xenon lamp, and the wavelength of the light is greater than or equal to 420 nm, that is, the reaction is carried out using visible light. The reaction temperature of the entire photocatalytic reaction is controlled at 25 °C using a condensing water device.

[0080] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0081] In the specific embodiments of the present invention, room temperature specifically refers to 20 - 30 °C.

[0082] All raw materials used in the following examples, comparative examples, and test examples of the present invention are ordinary commercially available products.

[0083] Example 1

[0084] A bifunctional catalyst of Mn nanoparticle-loaded g-C 3 N 5 was prepared according to the following steps:

[0085] (1) Preparation of g-C 3 N 5 nanosheets

[0086] Weighed 6 g of 3-amino-1,2,4-triazole, 9 g of KCl, and 0.5 g of KOH according to a mass ratio of 12:18:1 and added them to a mortar for thorough grinding to make the mixture uniform. Then, the obtained mixture was placed in a muffle furnace and heated to 550 °C at a heating rate of 5 °C·min -1 , and kept at 550 °C for 4 h. After the reaction ended, the product was cooled to room temperature and washed with a large amount of hot water at 80 °C to remove metal salts until the metal salts in the test sample were completely washed away using AgNO 3 . Then, the product was collected by filtration and vacuum-dried at 80 °C for 12 h to obtain g-C 3 N 5 nanosheets.

[0087] (2) Mn nanoparticle-loaded g-C 3 N5 Preparation of bifunctional catalyst

[0088] Disperse 100 mg of the g-C prepared in step (1) 3 N 5 nanosheets into 50 mL of water and stir vigorously at a rotation speed of 600 revolutions per minute to obtain g-C 3 N 5 suspension. Then, add 364 μL of 0.05 mol·L 3 N 5 concentration of MnCl -1 solution dropwise to the g-C 2 suspension, continuously stir in the dark for 2 h, and then age under the full spectrum using a 300 W xenon lamp for 1 h. After that, filter, wash the mixture at 60 °C, and dry it in vacuum at 60 °C for 8 h to obtain Mn x / g-C 3 N 5 powder. Heat the Mn x / g-C 3 N 5 powder in an H 2 / Ar (5 vol% / 95 vol%) atmosphere at a heating rate of 5 °C·min -1 to 200 °C and anneal at 200 °C for 3 h to obtain the g-C loaded with Mn nanoparticles 3 N 5 bifunctional catalyst, named 1-Mn / g-C 3 N 5 photocatalyst (1-Mn represents the loading amount of Mn is 1 wt%).

[0089] Example 2

[0090] Same as Example 1, the difference is only that the dosage of the MnCl 2 solution is 1092 μL, and the obtained product, the g-C loaded with Mn nanoparticles 3 N 5 bifunctional catalyst is named 3-Mn / g-C 3 N 5 photocatalyst (3-Mn represents the loading amount of Mn is 3 wt%).

[0091] Example 3

[0092] Same as Example 1, the difference is only that the dosage of the MnCl 2 solution is 1820 μL, and the obtained product, the g-C loaded with Mn nanoparticles 3 N 5 bifunctional catalyst is named 5-Mn / g-C 3 N 5Photocatalyst (5-Mn represents that the loading amount of Mn is 5 wt%).

[0093] Example 4

[0094] Same as Example 1, except that the amount of MnCl 2 solution is 2548 μL, and the obtained product is the g-C loaded with Mn nanoparticles 3 N 5 The bifunctional catalyst is named 7-Mn / g-C 3 N 5 Photocatalyst (7-Mn represents that the loading amount of Mn is 7 wt%).

[0095] Comparative Example 1

[0096] g-C 3 N 5 Preparation of g-C

[0097] Weigh 6 g of 3-amino-1,2,4-triazole, 9 g of KCl and 0.5 g of KOH according to the mass ratio of 12:18:1, add them to a mortar and grind thoroughly to make them evenly mixed. Then, put the obtained mixture into a muffle furnace and heat it to 550 °C at a heating rate of 5 °C·min -1 , and keep it at 550 °C for 4 h. After the reaction is completed, cool the product to room temperature, wash it with a large amount of hot water at 80 °C to remove metal salts until the metal salts in the test sample are completely washed away. Then, collect the product by filtration and vacuum dry it at 80 °C for 12 h to obtain g-C 3 N 3 nanosheets. 5

[0098] Comparative Example 2

[0099] Mn x / g-C 3 N 5 3 Preparation of powder

[0100] (1) Preparation of g-C 3 N 5 nanosheets

[0101] Weigh 6 g of 3-amino-1,2,4-triazole, 9 g of KCl and 0.5 g of KOH according to the mass ratio of 12:18:1, add them to a mortar and grind thoroughly to make them evenly mixed. Then, put the obtained mixture into a muffle furnace and heat it to 550 °C at a heating rate of 5 °C·min -1 , and keep it at 550 °C for 4 h. After the reaction is completed, cool the product to room temperature, wash it with a large amount of hot water at 80 °C to remove metal salts until the metal salts in the test sample are completely washed away. Then, collect the product by filtration and vacuum dry it at 80 °C for 12 h 3The metal salts in the test sample were completely washed out. Then, the product was collected by filtration and vacuum-dried at 80 °C for 12 h to obtain g-C 3 N 5 nanosheets.

[0102] (2) Preparation of Mn x / g-C 3 N 5 powder

[0103] Disperse 100 mg of the g-C 3 N 5 nanosheets prepared in step (1) into 50 mL of water and stir evenly to obtain a g-C 3 N 5 suspension. Then, 364 μL of 0.05 mol·L 3 concentration of MnCl 5 solution was dropped into the g-C -1 suspension, continuously stirred in the dark for 2 h, and then aged under a xenon lamp for 1 h. After that, the mixture was filtered, washed, and vacuum-dried at 60 °C to obtain Mn 2 / g-C x N 3 powder.

[0104] Comparative Example 3

[0105] Preparation of 5-Fe / g-C

[0106] Same as Example 1, except that 364 μL of 0.05 mol·L 3 concentration of MnCl 5 solution was replaced with 1790 μL of 0.05 mol·L -1 concentration of FeCl 2 solution, and the obtained product was a g-C -1 loaded with Fe nanoparticles 3 solution, and the obtained product was a g-C 3 N 5 catalyst, named 5-Fe / g-C 3 N 5 photocatalyst (5-Fe represents a Fe loading of 5 wt%).

[0107] Comparative Example 4

[0108] Preparation of 5-Co / g-C

[0109] Same as Example 1, except that 364 μL of 0.05 mol·L 3 concentration of MnCl 5 solution was replaced with 1790 μL of 0.05 mol·L -1 concentration of MnCl 2 solution was replaced with 1790 μL of 0.05 mol·L2 The solution was replaced with 1697 μL of 0.05 mol·L -1 concentration of CoCl 2 solution, and the obtained product was g-C loaded with Co nanoparticles 3 N 5 catalyst, named 5-Co / g-C 3 N 5 photocatalyst (5-Co represents a Co loading of 5 wt%).

[0110] Comparative Example 5

[0111] 5-Ni / g-C 3 N 5 Preparation of photocatalyst

[0112] Same as Example 1, except that 364 μL of 0.05 mol·L -1 concentration of MnCl 2 solution was replaced with 1704 μL of 0.05 mol·L -1 concentration of NiCl 2 solution, and the obtained product was g-C loaded with Ni nanoparticles 3 N 5 catalyst, named 5-Ni / g-C 3 N 5 photocatalyst (5-Ni represents a Ni loading of 5 wt%).

[0113] Test Example 1

[0114] Material characterization

[0115] (1) X-ray diffraction (XRD) test results

[0116] Figure 1 For the g-C loaded with Mn nanoparticles prepared in Examples 1-4 3 N 5 bifunctional catalyst (1-Mn / g-C 3 N 5 、3-Mn / g-C 3 N 5 、5-Mn / g-C 3 N 5 and 7-Mn / g-C 3 N 5 ) and the XRD patterns of the g-C 3 N 5 nanosheets prepared in Comparative Example 1, it can be observed that all samples have a relatively obvious diffraction peak at about 28°, which can be attributed to the (002) crystal plane of g-C 3 N 5 indicating g-C3 N 5 has very good crystallinity. After Mn doping, the g-C nitride 3 N 5 (002) peak shows little change, indicating that the incorporation of Mn does not disrupt the original crystal structure. No characteristic peaks attributed to Mn are found in the XRD patterns of all Mn / g-C 3 N 5 samples, suggesting that the loading amount of Mn in this catalyst is very small and the distribution is relatively dispersed.

[0117] (2) Scanning electron microscope (SEM) test results

[0118] Figure 2 For the 5-Mn / g-C 3 N 5 photocatalyst prepared in Example 3 and the g-C 3 N 5 nanosheets prepared in Comparative Example 1. Among them, (a) and (b) are 5-Mn / g-C 3 N 5 , and (c) and (d) are g-C 3 N 5 nanosheets. As Figure 2 shown, it can be clearly observed that g-C 3 N 5 exhibits a layered sheet structure, demonstrating that a thin-layer g-C 3 N 5 material with high crystallinity has been successfully prepared by the alkaline potassium salt thermal polymerization method. And by comparing with the morphology of 5-Mn / g-C 3 N 5 , it can be found that after Mn doping, the morphology of the sample does not change significantly and still presents a sheet-like structure.

[0119] (3) Transmission electron microscope (TEM) test results

[0120] Figure 3 For the TEM image of the 5-Mn / g-C 3 N 5 photocatalyst prepared in Example 3. Among them, (a) is a high-resolution TEM image, and (b)-(d) are low-resolution TEM images ((b)-(d) show three different positions). As Figure 3 shown, it can be clearly observed that g-C 3 N 5 exhibits a layered sheet structure, demonstrating that a thin-layer g-C 3 N 5Materials. And it can be clearly seen from the figure that there are black particulate matters (the part in the circle), with the particle size range roughly between 5 - 20 nm, which are attributed to the Mn nanoparticles loaded on the surface of g-C 3 N 5 by the hydrogen reduction method. It is proved that Mn has been successfully reduced and successfully loaded on the surface of g-C 3 N 5 by using the innovative hydrogen reduction method proposed in the present invention.

[0121] (4) X-ray photoelectron spectroscopy (XPS) test results

[0122] X-ray photoelectron spectroscopy is used to characterize the material composition and valence state of the photocatalyst. Figure 4 For the 5-Mn / g-C 3 N 5 photocatalyst prepared in Example 3 and the g-C 3 N 5 nanosheets prepared in Comparative Example 1, the XPS test results are as follows. Among them, (a) is the total XPS spectrum (XPS-Survey) of the two, showing that the elements C, N, and O exist in these samples, while Mn element also exists in 5-Mn / g-C 3 N 5 . (b) is the high-resolution XPS C 1s spectrum of the two. Among them, the four main peaks of CN are respectively at 288.9, 288.3, 286.6, and 284.8 eV. They originate from the triazole group on the surface of the CN skeleton and the carbon atoms bonded adjacent to three Ns, that is, N=C-N in the N-containing aromatic ring, the terminal amino group or C≡N converted from C-NH x , and C-C / C=C in the physically adsorbed C-containing substances. (c) is the XPS N 1s spectrum of the two, which consists of three binding peaks at 398.6, 400.5, and 401.3 eV, representing the bicoordinate N (C-N=C), tricoordinate N (N-(C) 3 ) in the framework, and the N-H x group respectively. It should be noted that with the doping of Mn and the coordination with g-C 3 N 5 , the characteristic peaks corresponding to the C and N elements of 5-Mn / g-C 3 N 5 shift to higher binding energies, indicating the existence of electron redistribution from the C / N domain to the Mn domain. The obvious peak shift of C and N in 5-Mn / g-C 3 N 5 may be due to the formation of more Mn-N bonds and then the interaction with other stronger bonds. The formation of Mn-N bonds produces a polarization effect, which changes g-C 3 N 5The distribution of the electron cloud, resulting in a decrease in the electron cloud density around C and N atoms. (d) is 5-Mn / g-C 3 N 5 XPS Mn 2p spectrum of 3 N 5 from which the characteristic peaks attributed to Mn in 5-Mn / g-C

[0123] can be clearly observed, which can prove the successful doping of Mn. 3 N 5 In addition, since the carrier displacement direction between the catalyst and the cocatalyst can be understood by exploring the change in the magnitude of the elemental binding energy, in-situ irradiation XPS of 5-Mn / g-C Figure 4 was also carried out to explore the influence of carrier displacement on the performance improvement. As shown in (b), (c), and (d) in 3 N 5 , under light illumination conditions, the characteristic peaks of C 1s and N1s both shift significantly towards the lower binding energy direction. Relatively speaking, the binding energy of Mn 2p shows a positive shift, indicating that a large amount of photo-generated charges on Mn are transferred to g-C 3 N 5 through the tightly bound Mn-N bond. Therefore, under dark conditions, due to the formation of a large number of Mn-N bonds, a polarization effect will occur, changing the distribution of the electron cloud in g-C 3 N 5 , resulting in a large number of electrons migrating to Mn. Subsequently, after exposure to light, the photo-generated electrons shift from Mn to the CN surface and participate in the subsequent reduction reaction, while a large number of photo-generated holes accumulate on Mn, leading to an increase in the oxidation reaction rate.

[0124] (5) Electron spin resonance (ESR) detection results

[0125] Figure 5 ESR spectra of the 5-Mn / g-C 3 N 5 photocatalyst prepared in Example 3 and the g-C 3 N 5 nanosheets prepared in Comparative Example 1. Among them, (a) is the intensity of the hydroxyl radical (·OH) generated by the two under different light illumination times, and (b) is the intensity of the superoxide radical (·O 2- ) generated by the two under different light illumination times. Dark represents the dark condition. It can be clearly observed from Figure 5 that compared with g-C 3 N 5 , with the increase of the light illumination time, 5-Mn / g-C 3 N 5It can exhibit a higher free radical generation rate, indicating that the sample after Mn doping can generate more free radicals beneficial to the photocatalytic reaction under the same light illumination conditions, thereby enhancing the photocatalytic performance. It should be noted that ·OH and ·O 2- respectively represent the intermediate free radicals required for the photocatalytic oxidation reaction and the reduction reaction. Therefore, the simultaneous increase in the intensities of both further proves that for 5-Mn / g-C 3 N 5 both the photocatalytic oxidation reaction and the reduction reaction capabilities are enhanced.

[0126] Test Example 2

[0127] Photocatalytic Performance Test

[0128] Add 50 mg of the photocatalyst into the photocatalytic reaction flask, then add 92 mL of deionized water and 8 mL of furfuryl alcohol. Pump the inside of the reaction flask to a vacuum state and ensure that there is no dissolved air in the water. The light source used during the reaction is a 300 W xenon lamp, and the wavelength of the light is greater than or equal to 420 nm, that is, the reaction is carried out using visible light. Use a condensing water device to control the reaction temperature of the entire photocatalytic reaction at 25°C. Automatically inject the gas in the reaction flask into the gas chromatograph for detection every 60 min.

[0129] Figure 6 For the g-C 3 N 5 nanosheets prepared in Comparative Example 1, the Mn x / g-C 3 N 5 prepared in Comparative Example 2, and the 1-Mn / g-C 3 N 5 prepared in Examples 1-4, 3-Mn / g-C 3 N 5 5-Mn / g-C 3 N 5 and 7-Mn / g-C 3 N 5 The test results of the bifunctional photocatalytic performance of the photocatalyst for photocatalytic water splitting reduction to produce hydrogen and simultaneously photocatalytic oxidation of furfuryl alcohol to produce furfural. Among them, (a) is the graph of the change in the photocatalytic water splitting hydrogen production curve. It can be seen that as the illumination time extends, the hydrogen production amount also gradually increases, showing a linear growth trend. (b) is the bar graph of the coupling performance of the hydrogen production efficiency and the efficiency of furfuryl alcohol conversion to furfural. It can be seen that g-C 3 N 5 Mn x / g-C 3 N 5 1-Mn / g-C 3 N 5 3-Mn / g-C 3 N5 and 5-Mn / g-C 3 N 5 and 7-Mn / g-C 3 N 5 The H 2 generation rates are 160.1, 199.7, 277.3, 482.3, 567.8, and 414.7 μmol·g -1 ·h -1 respectively. The corresponding generation rates of furfural obtained by the oxidation of furfuryl alcohol are 219.1, 332.4, 439.5, 554.1, 595.6, and 525.2 μmol·g -1 ·h -1 respectively. All Mn / g-C 3 N 5 are significantly superior to g-C 3 N 5 and Mn x / g-C 3 N 5 . It can also be found that when the loading amount of Mn reaches 5 wt%, the photocatalytic activity of the material is the highest, and the hydrogen production rate and the conversion rate of furfural are 3.5 and 2.7 times that of g-C 3 N 5 respectively. When the loading amount of Mn is insufficient or exceeds 5 wt%, the increase in activity is significantly slow, which may be due to the reduced utilization rate of Mn atoms. It should be noted that the performance of Mn x / g-C 3 N 5 in Comparative Example 2 is worse than that of 1-Mn / g-C 3 N 5 in Example 1. This may be because the Mn loaded on the surface of g-C 3 N 5 in Comparative Example 2 mainly exists in the form of oxides with different valence states rather than Mn nanoparticles. Therefore, the improvement of the oxidation performance of g-C 3 N 5 is not obvious. This further proves that in the preparation process of the photocatalyst of the present invention, the loading method of metal nanoparticles is realized by combining photodeposition and annealing. This method is innovative and irreplaceable, and is an important condition for improving the performance of subsequent photocatalysts. In addition, the performance of all samples is improved after loading Mn, indicating that the loading of Mn enhances the oxidation performance of the catalyst, thereby driving the improvement of the reduction performance and achieving the goal of bifunctional coupling.

[0130] Figure 7 g-C 3 N 5Nanosheets, 5-Mn / g-C prepared in Example 3 3 N 5 , 5-Fe / g-C prepared in Comparative Example 3 3 N 5 , 5-Co / g-C prepared in Comparative Example 4 3 N 5 and 5-Ni / g-C prepared in Comparative Example 5 3 N 5 Test results of the bifunctional photocatalytic performance of photocatalysts for photocatalytic water splitting reduction to produce hydrogen and simultaneous photocatalytic oxidation of furfuryl alcohol to produce furfural (bar chart of the coupling performance of hydrogen production efficiency and the efficiency of furfuryl alcohol conversion to furfural). It can be seen that for g-C 3 N 5 , 5-Fe / g-C 3 N 5 , 5-Co / g-C 3 N 5 , 5-Ni / g-C 3 N 5 and 5-Mn / g-C 3 N 5 , the H 2 generation rates are 160.1, 376.7, 397.3, 414.5 and 567.8 μmol·g -1 ·h -1 respectively. And the corresponding generation rates of furfural obtained by the oxidation of furfuryl alcohol are 219.1, 326.6, 375.4, 457.4 and 595.6 μmol·g -1 ·h -1 respectively. When the same proportion of non-noble metals is loaded on g-C 3 N 5 , the photocatalytic oxidation and reduction performances are both improved. However, due to the relatively single change in oxidation state or the relatively slow redox reaction rate of transition metals such as Fe, Co, Ni, etc., the improvement in oxidation ability is relatively limited and cannot meet the conditions for achieving the redox reaction balance, resulting in relatively little improvement in photocatalytic reduction performance. While 5-Mn / g-C 3 N 5 exhibits the highest photocatalytic activity, and the hydrogen production rate and the conversion rate of furfural are respectively those of g-C 3 N 53.5 and 2.7 times that. This is because Mn has multiple stable oxidation states, enabling it to more effectively serve as an electron transfer medium, promoting the separation of photo-generated carriers during the process of receiving and transferring photo-generated holes, providing more active sites for the oxidation reaction, and thus enhancing the oxidation performance. For promoting the progress of the oxidation reaction and the dynamic balance between the oxidation reaction and the reduction reaction, and further driving the efficiency of the reduction reaction, thereby greatly improving the photocatalytic activity and achieving the goal of dual-functional coupling, the loading of non-noble metal Mn is the most suitable.

[0131] For 5-Mn / g-C 3 N 5 Perform cyclic performance tests. Specifically, add 50 mg of 5-Mn / g-C 3 N 5 into the photocatalytic reaction flask, then add 92 mL of deionized water and 8 mL of furfuryl alcohol. Pump the inside of the reaction flask to a vacuum state and ensure that there is no dissolved air in the water. The light source used during the reaction is a 300-W xenon lamp, and the wavelength of the light is greater than or equal to 420 nm, that is, the reaction is carried out using visible light. Use a condensing water device to control the reaction temperature of the entire photocatalytic reaction at 25 °C. Automatically inject the gas in the reaction flask into the gas chromatograph for detection every 60 min. After 5 h of reaction, stop the light irradiation, which is the first reaction. Subsequently, centrifuge and recover the photocatalyst sample after the reaction, and then add it again to the same reaction substrate and carry out the second reaction under the same conditions. A total of 4 cyclic tests are carried out.

[0132] Figure 8 The hydrogen production cycle diagram of 5-Mn / g-C 3 N 5 prepared in Example 3 can be observed. After 4 cyclic experiments, the hydrogen production performance of 5-Mn / g-C 3 N 5 does not decrease significantly and still remains stable.

[0133] Figure 9 The XRD diagram of 5-Mn / g-C 3 N 5 prepared in Example 3 before and after the photocatalytic reaction, Figure 10 The XRD diagram of 5-Mn / g-C 3 N 5 The XPS-Surve diagram of 5-Mn / g-C Figure 9 and Figure 10 show that after the photocatalytic reaction, the XRD diagram and XPS diagram of 5-Mn / g-C 3 N 5 barely change, further proving that 5-Mn / g-C 3 N 5It has a certain stability (not only the structure of g-C 3 N 5 is stable, but also the loading of Mn nanoparticles is stable and not easy to fall off).

[0134] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A bifunctional photocatalyst of graphite nitride and carbon nitride loaded with Mn nanoparticles, characterized in that: It includes a nitrided graphite carbon nitride carrier and Mn nanoparticles supported on the nitrided graphite carbon nitride carrier; The loading amount of the Mn nanoparticles is 1-7 wt %.

2. The method for preparing the bifunctional photocatalyst of graphite nitride and carbon nitride loaded with Mn nanoparticles according to claim 1, characterized in that: The following steps are involved: Dispersing nitrided graphite carbon nitride in water to obtain a nitrided graphite carbon nitride suspension; Mn was added dropwise into the nitrided graphite carbon nitride suspension. 2+ The solution is first stirred for reaction in the dark and then aged for reaction under light conditions to obtain a precursor; the precursor is annealed to obtain the nitrided graphite carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles.

3. The preparation method according to claim 2, characterized in that: The usage ratio of the nitrided graphite carbon nitride and water is 50-200 mg:30-100 mL.

4. The preparation method according to claim 2, characterized in that: The Mn 2+ The solution includes manganese chloride solution, manganese nitrate solution and manganese sulfate solution; the Mn 2+ The concentration of the solution is 0.01-0.1 mol·L -1 .

5. The preparation method according to claim 2, characterized in that: The nitrided graphite carbon nitride suspension and the Mn 2+ The dosage ratio of the solution is 30-100mL:100-3000μL.

6. The preparation method according to claim 2, characterized in that: The reaction time of the stirring reaction under dark conditions is 1-5 hours; the reaction time of the aging reaction under light conditions is 1-5 hours.

7. The preparation method according to claim 2, characterized in that: The conditions of the illumination include: the wavelength of the light is less than 420nm, greater than or equal to 420nm or the full spectrum.

8. The preparation method according to claim 2, characterized in that: The annealing treatment conditions include: the annealing atmosphere is air, hydrogen, nitrogen, argon or a hydrogen-argon mixed atmosphere, the annealing temperature is 100-300° C., and the annealing time is 1-5 hours.

9. Use of the bifunctional photocatalyst of graphite nitride and carbon nitride loaded with Mn nanoparticles as claimed in claim 1 in photocatalytic water decomposition reduction to produce hydrogen coupled with furfuryl alcohol oxidation to produce furfural.

10. The use according to claim 9, characterized in that The step of photocatalytic water decomposition reduction to produce hydrogen coupled with furfuryl alcohol oxidation to produce furfural comprises: mixing the graphite nitride carbon nitride bifunctional photocatalyst loaded with Mn nanoparticles with water and furfuryl alcohol, evacuating the mixture, and then reacting the mixture under light conditions.

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