Preparation method of a photocatalyst for photocatalytic hydrogen evolution and oxidation of 5-hydroxymethylfurfural and application thereof in high-selectivity generation of 2,5-furan dicarboxylic acid

Abstract

The application relates to a preparation method and application of a photocatalyst for photocatalytic hydrogen evolution and 5-hydroxymethylfurfural oxidation, and relates to a preparation method and application of a photocatalyst.The application aims to solve the problems that traditional hydrogen production methods have many limitations, it is difficult to realize an economically competitive hydrogen production route, a value-added reaction cannot be realized in cooperation with the hydrogen production process, and the overall economic value cannot be improved.The application is based on an ultrathin porous CN nanosheet, and the surface is modified by -C=N to induce 5-hydroxymethylfurfural to selectively generate 2,5-furan dicarboxylic acid.In addition, long-life free electrons are effectively captured and utilized, various metal phthalocyanines are loaded on the surface, efficient hydrogen production is realized, the photocatalytic activity of the catalyst is significantly improved, and the catalyst has stability and durability, and can realize the application of photocatalytic technology in an industry.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a photocatalyst. Background Art

[0002] With the growing global demand for clean energy, green hydrogen, as one of the most ideal energy sources, is considered the main direction of future hydrogen energy development. The production of so-called "green hydrogen", that is, the use of renewable energy to produce hydrogen, has become the preferred approach. However, traditional hydrogen production methods have many limitations, making it difficult to achieve an economically competitive hydrogen production route. Therefore, the use of synergistic value-added reactions is an effective way to overcome these limitations. Value-added reactions that work in conjunction with the hydrogen production process can increase the overall economic value. At the same time, the widespread distribution and renewable availability of biomass make it an important source of alternatives to fossil fuels. Therefore, the by-products of hydrogen production are used in biomass conversion to achieve comprehensive resource utilization.

[0003] In this field, the present invention proposes a novel catalyst design for photocatalytic hydrogen production coupled with the selective oxidation of HMF to FDCA. The development of this technology will help promote the development and promotion of bio-based chemicals, while also providing important support for the utilization of biorenewable energy and the development of the green chemical industry. HMF (5-hydroxymethylfurfural) is an important bio-based compound with abundant oxidation products and numerous potential applications. The selective production of FDCA (2,5-furandicarboxylic acid) is of particular significance. FDCA can serve as an important biorenewable chemical, replacing traditional petroleum-based chemicals, reducing dependence on non-renewable resources and promoting the utilization of biorenewable resources. FDCA can also be used to produce biodegradable polyester plastics, offering excellent performance and good degradability. It is a green chemical raw material that can effectively promote the development of the green chemical industry. Furthermore, as an important organic synthesis intermediate, FDCA is used in the synthesis of drugs and medical materials, and has broad application prospects in the pharmaceutical field. Therefore, given the application value of FDCA produced by the oxidation of HMF, research on its production, synthesis, and application will help promote the development and promotion of bio-based chemicals. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems that traditional hydrogen production methods have many limitations, which make it difficult to achieve an economically competitive hydrogen production route, unable to achieve value-added reactions synergistic with the hydrogen production process and unable to improve the overall economic value, and to provide a preparation method and application of a photocatalytic hydrogen evolution synergistic HMF oxidation photocatalyst.

[0005] A method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural is specifically completed by the following steps:

[0006] 1. Preparation of ultrathin porous CN nanosheets:

[0007] ①, dispersing melamine and cyanuric acid in deionized water, heating and stirring for a period of time, cooling to room temperature, and then centrifuging to remove the supernatant to obtain a precipitate; drying the precipitate, and then heating it from room temperature to 500°C to 550°C under a nitrogen atmosphere for a first calcination to obtain a product after the first calcination;

[0008] ②, heating the product after the first calcination from room temperature to 520°C to 550°C in an air atmosphere for a second calcination to obtain a second calcined product; and acid-treating the second calcined product to obtain ultrathin porous CN nanosheets;

[0009] 2. Preparation of cyanamide-functionalized CN nanosheets:

[0010] The ultrathin porous CN nanosheets and dried potassium thiocyanate are mixed and fully ground to obtain a mixture; the mixture is placed in a tube furnace, and under the protection of an argon atmosphere, the temperature is raised from room temperature to 350°C to 450°C, and the temperature is kept at 350°C to 450°C for 0.5h to 1.5h, and then the temperature is raised to 500°C to 550°C, and the temperature is kept at 500°C to 550°C for 20min to 40min to obtain a reaction product; the reaction product is centrifuged and washed with deionized water as a cleaning agent to obtain a precipitate; and the precipitate is dried to obtain a cyanamide-functionalized CN nanosheet.

[0011] 3. Disperse the metal phthalocyanine and cyanamide functionalized CN nanosheets in anhydrous ethanol, then heat and stir until dry to obtain a photocatalytic hydrogen evolution synergistic HMF oxidation photocatalyst.

[0012] A photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural is used for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural to produce 2,5-furandicarboxylic acid with high selectivity.

[0013] Principle of the present invention:

[0014] The present invention is based on ultrathin porous CN nanosheets and uses NC≡N surface modification to induce HMF (5-hydroxymethylfurfural) to selectively generate FDCA (2,5-furandicarboxylic acid). In addition, the effective capture and utilization of holes produces long-lived free electrons, and by loading various metal phthalocyanines (MPc) on its surface, efficient hydrogen production is achieved. This catalyst significantly improves photocatalytic activity and is stable and durable, enabling the application of photocatalytic technology in industry. In addition, the catalyst has the advantages of low cost and easy preparation, which is conducive to the promotion and application of photocatalytic technology.

[0015] Beneficial effects of the present invention:

[0016] The photocatalytic hydrogen evolution and HMF oxidation photocatalyst prepared by the present invention has high efficiency in photocatalytic hydrogen evolution and HMF (5-hydroxymethylfurfural) selective oxidation, with a hydrogen production efficiency of 4.38 mmol g -1 h -1 HMF was selectively oxidized to generate FDCA (2,5-furandicarboxylic acid) with a yield of 1.16 mmol g -1 h -1 ;

[0017] Second, the present invention introduces negatively charged groups through -C≡N modification, and the HMF aldehyde group C and the cyano group are nucleophilic and preferentially oxidized, thereby improving the efficiency of selective oxidation to FDCA;

[0018] Third, because the free electron lifetime is very long and can be used for hydrogen evolution reaction, the g-C3N4 modified with -C≡N surface of the present invention is generally suitable for various optimization methods to improve hydrogen evolution activity;

[0019] 4. The photocatalyst prepared by the present invention for photocatalytic hydrogen evolution synergistic HMF oxidation shows good activity and selectivity in the photocatalytic hydrogen evolution synergistic HMF oxidation reaction, providing a new efficient and environmentally friendly catalyst design idea, which is expected to be widely used in the fields of renewable energy and organic matter oxidation. At the same time, it has high charge transfer efficiency and internal and external quantum efficiency at a suitable single wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Transmission electron microscopy image of 0.5NiPc / CA-CN;

[0021] Figure 2 AFM atomic force microscopy image of 0.5NiPc / CA-CN;

[0022] Figure 3 This is the EDX element scanning result of 0.5NiPc / CA-CN;

[0023] Figure 4 UV absorption spectra of CN, 0.5NiPc / CN, CA-CN and 0.5NiPc / CA-CN;

[0024] Figure 5 Comparison of hydrogen production rates of CN, 0.5NiPc / CN, 0.5Pt / CN, 0.5NiPc / CA-CN and 0.5Pt / CA-CN;

[0025] Figure 6 Comparison of the oxidation products of 5-hydroxymethylfurfural synergized by photocatalytic hydrogen evolution of CN, 0.5NiPc / CN, 0.5Pt / CN, 0.5NiPc / CA-CN and 0.5Pt / CA-CN;

[0026] Figure 7 The stability test performance results of 0.5NiPc / CA-CN are shown below;

[0027] Figure 8 The relationship between the charge transfer efficiency, internal quantum efficiency and absorption spectrum of 0.5NiPc / CA-CN;

[0028] Figure 9 This is the relationship between the hydrogen production performance and charge transfer efficiency of CN, 0.5H2Pc / CN, 0.5ZnPc / CN, 0.5FePc / CN, 0.5CuPc / CN, 0.5NiPc / CN, CA-CN, 0.5H2Pc / CA-CN, 0.5ZnPc / CA-CN, 0.5FePc / CA-CN, 0.5CuPc / CA-CN, and 0.5NiPc / CA-CN. DETAILED DESCRIPTION

[0029] Specific embodiment 1: This embodiment provides a method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural, which is specifically completed by the following steps:

[0030] 1. Preparation of ultrathin porous CN nanosheets:

[0031] ①, dispersing melamine and cyanuric acid in deionized water, heating and stirring for a period of time, cooling to room temperature, and then centrifuging to remove the supernatant to obtain a precipitate; drying the precipitate, and then heating it from room temperature to 500°C to 550°C under a nitrogen atmosphere for a first calcination to obtain a product after the first calcination;

[0032] ②, heating the product after the first calcination from room temperature to 520°C to 550°C in an air atmosphere for a second calcination to obtain a second calcined product; and acid-treating the second calcined product to obtain ultrathin porous CN nanosheets;

[0033] 2. Preparation of cyanamide-functionalized CN nanosheets:

[0034] The ultrathin porous CN nanosheets and dried potassium thiocyanate are mixed and fully ground to obtain a mixture; the mixture is placed in a tube furnace, and under the protection of an argon atmosphere, the temperature is raised from room temperature to 350°C to 450°C, and the temperature is kept at 350°C to 450°C for 0.5h to 1.5h, and then the temperature is raised to 500°C to 550°C, and the temperature is kept at 500°C to 550°C for 20min to 40min to obtain a reaction product; the reaction product is centrifuged and washed with deionized water as a cleaning agent to obtain a precipitate; and the precipitate is dried to obtain a cyanamide-functionalized CN nanosheet.

[0035] 3. Disperse the metal phthalocyanine and cyanamide functionalized CN nanosheets in anhydrous ethanol, then heat and stir until dry to obtain a photocatalytic hydrogen evolution synergistic HMF oxidation photocatalyst.

[0036] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the volume ratio of melamine to deionized water in step 1 (1) is (5g-15g):500mL; the volume ratio of cyanuric acid to deionized water in step 1 (1) is (2g-6g):500mL. Other steps are the same as those in specific embodiment 1.

[0037] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that the heating and stirring temperature in step 1 (1) is 60°C to 100°C, and the stirring time is 2 to 4 hours; the centrifugation speed in step 1 (1) is 4000 to 6000 rpm, and the centrifugation time is 5 to 10 minutes. Other steps are the same as those in specific embodiments 1 or 2.

[0038] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: in step 1 (1), the precipitate is dried at 80°C to 100°C for 10 to 12 hours; the heating rate in step 1 (1) is 1°C / min to 3°C / min; and the first calcination time in step 1 (1) is 3 to 5 hours. The other steps are the same as specific embodiments 1 to 3.

[0039] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the heating rate in step 1 (2) is 1°C / min to 3°C / min; the second calcination time in step 1 (2) is 2 to 4 hours; the acid treatment in step 1 (2) involves washing the product after the second calcination with nitric acid at a temperature of 105°C to 120°C for 1 to 3 hours, then washing with water until neutral and drying to obtain ultrathin porous CN nanosheets; the concentration of the nitric acid is 5 mol / L. Other steps are the same as those in specific embodiments 1 to 4.

[0040] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the mass ratio of the ultrathin porous CN nanosheets and dried potassium thiocyanate in step 2 is (700 mg to 900 mg): (1.5 g to 1.7 g); the dried potassium thiocyanate in step 2 is potassium thiocyanate vacuum-dried at 140°C for 2 to 4 hours. The other steps are the same as specific embodiments 1 to 5.

[0041] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the heating rate in step 2 is 5°C / min to 15°C / min, and the precipitate is dried at 50°C to 70°C in step 2. The other steps are the same as specific embodiments 1 to 6.

[0042] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the heating and stirring temperature in step 3 is 50°C to 70°C, and the stirring speed is 180 rpm to 220 rpm; and the metal phthalocyanine in step 3 is nickel phthalocyanine, copper phthalocyanine, zinc phthalocyanine, or iron phthalocyanine. The other steps are the same as specific embodiments 1 to 7.

[0043] Specific Embodiment 9: This embodiment differs from Specific Embodiments 1 to 8 in that the mass ratio of the metal phthalocyanine to the cyanamide-functionalized CN nanosheets in step 3 is (0.1-1):100; and the volume ratio of the cyanamide-functionalized CN nanosheets in step 3 to anhydrous ethanol is (15 mg-30 mg):(40 mL-60 mL). Other steps are the same as Specific Embodiments 1 to 8.

[0044] Specific embodiment ten: This embodiment is a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural, which is used for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural to generate 2,5-furandicarboxylic acid with high selectivity.

[0045] The following examples are used to verify the beneficial effects of the present invention:

[0046] Example 1: A method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural is specifically completed by the following steps:

[0047] 1. Preparation of ultrathin porous CN nanosheets:

[0048] ①, 10g of melamine and 4g of cyanuric acid were dispersed in 500mL of deionized water, heated and stirred at 80°C for 3h, and then centrifuged at a speed of 4000r / min for 5min, and the supernatant was removed to obtain a precipitate; the precipitate was dried at 80°C for 12h, and then heated from room temperature to 520°C at a heating rate of 1°C / min under nitrogen atmosphere, and calcined at 520°C for 4h to obtain a product after the first calcination;

[0049] ②, heating the product after the first calcination from room temperature to 520°C at a heating rate of 1°C / min in an air atmosphere, and calcining at 520°C for 2 hours to obtain a product after the second calcination; and acid-treating the product after the second calcination to obtain ultrathin porous CN nanosheets (CN);

[0050] The acid treatment in step 1 (2) is to use nitric acid at a temperature of 105° C. to wash the product after the second calcination for 2 hours, then use water to wash it until it is neutral and dry it to obtain ultrathin porous CN nanosheets; the concentration of the nitric acid is 5 mol / L;

[0051] 2. Preparation of cyanamide-functionalized CN nanosheets:

[0052] 800 mg of ultrathin porous CN nanosheets and 1.6 g of dried potassium thiocyanate were mixed and thoroughly ground to obtain a mixture; the mixture was placed in a tube furnace, and under argon atmosphere, the temperature was increased from room temperature to 400°C at a heating rate of 10°C / min, and kept at 400°C for 1 hour, then increased to 500°C at a heating rate of 10°C / min, and kept at 500°C for 30 minutes to obtain a reaction product; the reaction product was centrifuged and washed three times with deionized water as a cleaning agent to obtain a precipitate; the precipitate was dried at 60°C to obtain cyanamide-functionalized CN nanosheets (CA-CN);

[0053] The dried potassium thiocyanate in step 2 is potassium thiocyanate dried in vacuum at 140° C. for 3 h;

[0054] Third, 0.5 mg of metal phthalocyanine and 100 mg of cyanamide-functionalized CN nanosheets were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60 ° C and a stirring speed of 200 r / min until dry to obtain a photocatalytic hydrogen evolution synergistic HMF oxidation photocatalyst (0.5NiPc / CA-CN);

[0055] The metal phthalocyanine described in step 3 is nickel phthalocyanine.

[0056] Comparative Example 1: The preparation method of 0.5NiPc / CN is completed according to the following steps:

[0057] 0.5 mg of metal phthalocyanine and 100 mg of the ultrathin porous CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5NiPc / CN; the metal phthalocyanine was nickel phthalocyanine.

[0058] Comparative Example 2: The preparation method of 0.5Pt / CN is completed according to the following steps:

[0059] 2.1 mL of chloroplatinic acid and 100 mg of the ultrathin porous CN nanosheets obtained in Example 1 were dispersed in 100 mL of water, stirred for 2 h under irradiation with a 300 W xenon lamp, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5 Pt / CN.

[0060] Comparative Example 3: The preparation method of 0.5Pt / CA-CN is completed according to the following steps:

[0061] 2.1 mL of chloroplatinic acid and 100 mg of the cyanamide-functionalized CN nanosheets obtained in Example 1 were dispersed in 100 mL of water, stirred for 2 h under irradiation with a 300 W xenon lamp, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5Pt / CA-CN.

[0062] Comparative Example 4: The preparation method of 0.5H2Pc / CN is completed according to the following steps:

[0063] 0.5 mg of non-metallic phthalocyanine and 100 mg of the ultrathin porous CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5H2Pc / CN.

[0064] Comparative Example 5: The preparation method of 0.5ZnPc / CN is completed according to the following steps:

[0065] 0.5 mg of metal phthalocyanine and 100 mg of the ultrathin porous CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5ZnPc / CN; the metal phthalocyanine was zinc phthalocyanine.

[0066] Comparative Example 6: The preparation method of 0.5FePc / CN is completed according to the following steps:

[0067] 0.5 mg of metal phthalocyanine and 100 mg of the ultrathin porous CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5FePc / CN; the metal phthalocyanine was iron phthalocyanine.

[0068] Comparative Example 7: The preparation method of 0.5CuPc / CN is completed according to the following steps:

[0069] 0.5 mg of metal phthalocyanine and 100 mg of the ultrathin porous CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5CuPc / CN; the metal phthalocyanine was copper phthalocyanine.

[0070] Comparative Example 8: The preparation method of 0.5H2Pc / CA-CN is completed according to the following steps:

[0071] 0.5 mg of non-metallic phthalocyanine and 100 mg of the cyanamide-functionalized CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5H2Pc / CA-CN.

[0072] Comparative Example 9: The preparation method of 0.5ZnPc / CA-CN is completed according to the following steps:

[0073] 0.5 mg of non-metallic phthalocyanine and 100 mg of cyanamide-functionalized CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5ZnPc / CA-CN; the metal phthalocyanine was zinc phthalocyanine.

[0074] Comparative Example 10: The preparation method of 0.5FePc / CA-CN is completed according to the following steps:

[0075] 0.5 mg of non-metallic phthalocyanine and 100 mg of cyanamide-functionalized CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5FePc / CA-CN; the metal phthalocyanine was iron phthalocyanine.

[0076] Comparative Example 11: The preparation method of 0.5CuPc / CA-CN is completed by the following steps:

[0077] 0.5 mg of non-metallic phthalocyanine and 100 mg of cyanamide-functionalized CN nanosheets obtained in Example 1 were dispersed in 50 mL of anhydrous ethanol, and then heated and stirred at 60° C. and a stirring speed of 200 r / min until dry to obtain 0.5CuPc / CA-CN; the metal phthalocyanine was copper phthalocyanine.

[0078] Figure 1 This is the relationship between the hydrogen production performance and charge transfer efficiency of CN, 0.5H2Pc / CN, 0.5ZnPc / CN, 0.5FePc / CN, 0.5CuPc / CN, 0.5NiPc / CN, CA-CN, 0.5H2Pc / CA-CN, 0.5ZnPc / CA-CN, 0.5FePc / CA-CN, 0.5CuPc / CA-CN, and 0.5NiPc / CA-CN.

[0079] Figure 1 ETE: Charge transfer efficiency, from Figure 1 It can be seen that effective cyanamide functionalization can generally improve the photocatalytic performance of various co-catalysts (various metal phthalocyanines - MPc including precious metal Pt).

[0080] Figure 2 Transmission electron microscopy image of 0.5NiPc / CA-CN;

[0081] from Figure 2 It can be seen that NiPc is uniformly loaded and the overall catalyst is a smooth two-dimensional sheet structure.

[0082] Figure 3 AFM atomic force microscopy image of 0.5NiPc / CA-CN;

[0083] from Figure 3 It can be seen that the thickness of 0.5NiPc / CA-CN is approximately 3nm to 4nm.

[0084] Figure 4 This is the EDX element scanning result of 0.5NiPc / CA-CN;

[0085] from Figure 4 It can be seen that the proportions of elements C, N and Ni are basically consistent with the synthetic ratio, and it can be seen that NiPc is evenly dispersed.

[0086] Figure 5 UV absorption spectra of CN, 0.5NiPc / CN, CA-CN and 0.5NiPc / CA-CN;

[0087] Figure 5 An absorption peak at 675 nm can be observed in the Q band region of 0.5NiPc / CN and 0.5NiPc / CA-CN, which is attributed to the absorption characteristics of NiPc. The absorption peak areas of the two signals are almost identical, indicating that the introduction of cyanamide does not affect the dispersion and loading of NiPc. The change in the B band absorption peak is attributed to a slight shift in the band gap caused by the introduction of cyanamide. (400-500 nm)

[0088] Application experiment 1: Photocatalytic hydrogen evolution using CN, 0.5NiPc / CN, 0.5Pt / CN, 0.5NiPc / CA-CN, and 0.5Pt / CA-CN was performed in the following steps:

[0089] The photocatalytic water splitting experiment was carried out by an integrated system consisting of a photoreactor and a gas chromatography online analysis system (Beijing Perfectlight, Labsolar-6A circulation system). Operation method: 50 mg of CN, 0.5 NiPc / CN, 0.5 Pt / CN, 0.5 NiPc / CA-CN and 0.5 Pt / CA-CN were dispersed in 100 mL of a 5 mol / L HMF (5-hydroxymethylfurfural) aqueous solution in a cubic glass cell and kept stirring. Before the reaction, the mixture was degassed by vacuum to remove oxygen and carbon dioxide dissolved in the water. Subsequently, the solution was irradiated with a 300 W xenon lamp for 4 hours, and the water flow was circulated to maintain a constant temperature (5°C).

[0090] Figure 6 Comparison of hydrogen production rates of CN, 0.5NiPc / CN, 0.5Pt / CN, 0.5NiPc / CA-CN and 0.5Pt / CA-CN;

[0091] Figure 6 The photocatalytic hydrogen evolution capacity of each catalyst is provided. The hydrogen production rates of samples CN, 0.5NiPc / CN, 0.5Pt / CN, 0.5NiPc / CA-CN and 0.5Pt / CA-CN are 0.03mmolg -1 h -1 、0.52mmolg -1 h -1 、2.30mmolg -1 h -1 、4.38mmolg -1 h -1 and 4.45mmolg -1 h -1 The final results showed that the 0.5NiPc / CA-CN heterojunction exhibited a high H2 yield rate. This rate was approximately 148 times that of pure CN and close to that of 0.5Pt / CA-CN. Compared with 0.5Pt / CA-CN, the 0.5NiPc / CA-CN prepared by this invention significantly reduced costs and improved economic competitiveness.

[0092] Application Experiment 2:

[0093] The reaction solution after hydrogen evolution in Example 1 was sent to liquid chromatography for detection. Photocatalytic hydrogen evolution was accompanied by HMF oxidation. The contents of the products FDCA (2,5-furandicarboxylic acid), FFCA (5-formyl-2-furancarboxylic acid), HMFCA (5-hydroxymethyl-2-furancarboxylic acid), and DFF (2,5-furandicarboxaldehyde) were detected. Figure 7 As shown;

[0094] Figure 7Comparison of the oxidation products of 5-hydroxymethylfurfural synergized by photocatalytic hydrogen evolution of CN, 0.5NiPc / CN, 0.5Pt / CN, 0.5NiPc / CA-CN and 0.5Pt / CA-CN;

[0095] from Figure 7 It can be seen that HMF plays a vital role in the above hydrogenation reaction and promotes the efficient catalytic conversion of biomass, thereby increasing the value of this conversion process. Although pure CN generates oxidation products mainly composed of DFF, the yield is relatively low, at 4.8×10 -3 mmolg -1 h -1 DFF, FFCA, and FDCA were detected in the liquid phase over 0.5NiPc / CN and 0.5Pt / CN catalysts as oxidation products. DFF was the major product with a selectivity exceeding 96% and a yield of 0.06 and 0.33 mmol g, respectively. -1 h -1 The HMF conversion rate of 0.5NiPc / CA-CN was significantly improved. HMF was oxidized to HMFCA, FFCA and FDCA. FDCA became the main product with a yield of 1.16mmolg -1 h -1 .

[0096] Application Experiment 3: The stability test of 0.5NiPc / CA-CN was completed in the following steps:

[0097] The photocatalytic water splitting experiment was carried out by an integrated system consisting of a photoreactor and a gas chromatography online analysis system (Beijing Perfectlight, Labsolar-6A circulation system). Operation method: 0.5NiPc / CA-CN was dispersed in 100mL, 5mol / L HMF (5-hydroxymethylfurfural) aqueous solution in a cubic glass cell and kept stirring. Before the reaction, the mixture was degassed by vacuuming to remove oxygen and carbon dioxide dissolved in the water. Subsequently, the solution was irradiated with a 300W xenon lamp for 4h, and the water flow was circulated to maintain a constant temperature (5°C). After each operation for 4 hours, the used photocatalyst was separated, washed with a large amount of ethanol, and then dried at 60°C in a vacuum oven for the next cycle reaction. The stability test results are shown in FIG. Figure 8 As shown;

[0098] Figure 8 The stability test performance results of 0.5NiPc / CA-CN are shown below;

[0099] from Figure 8 It can be seen that the stability of 0.5NiPc / CA-CN was evaluated through multiple cycle experiments, and it was found that the catalyst can undergo more than 4 cycles without a significant decrease in performance.

[0100] Application Experiment 4: The internal quantum efficiency test method of 0.5NiPc / CA-CN is completed in the following steps:

[0101] 50 mg of photocatalyst powder was dispersed in 100 ml of 5 mol / L HMF aqueous solution in a cubic glass cell and stirred. Before the reaction, the mixture was degassed by vacuum to remove oxygen and carbon dioxide dissolved in the water. Subsequently, the solution was irradiated with an LED lamp of the corresponding wavelength for 4 h, and the light intensity of the lamp was confirmed with a power meter. The water flow was circulated to maintain a constant temperature (5°C). The relationship between the charge transfer efficiency, internal quantum efficiency and absorption spectrum of 0.5NiPc / CA-CN is shown in Figure 9 As shown;

[0102] Figure 9 The relationship between the charge transfer efficiency, internal quantum efficiency and absorption spectrum of 0.5NiPc / CA-CN;

[0103] Figure 9 ETE: charge transfer efficiency, IQY: internal quantum efficiency. The high performance of 0.5NiPc / CA-CN is due to effective light absorption, efficient charge transfer and high internal quantum efficiency.

[0104] Application experiment 5: The test method for the charge transfer efficiency of CN, 0.5H2Pc / CN, 0.5ZnPc / CN, 0.5FePc / CN, 0.5CuPc / CN, 0.5NiPc / CN, CA-CN, 0.5H2Pc / CA-CN, 0.5ZnPc / CA-CN, 0.5FePc / CA-CN, 0.5CuPc / CA-CN, and 0.5NiPc / CA-CN is in situ transient absorption. A fixed laser light source is used to excite the sample, obtain the absorption signal, and compare and observe the partial charge transferred.

Claims

1. A method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of ultrathin porous CN nanosheets: ①, dispersing melamine and cyanuric acid in deionized water, heating and stirring for a period of time, cooling to room temperature, and then centrifuging to remove the supernatant to obtain a precipitate; drying the precipitate, and then heating it from room temperature to 500°C to 550°C under a nitrogen atmosphere for a first calcination to obtain a product after the first calcination; The first calcination time in step 1① is 3h~5h; ②, heating the product after the first calcination from room temperature to 520°C~550°C in an air atmosphere for a second calcination to obtain a product after the second calcination; The product after the second calcination was treated with acid to obtain ultrathin porous CN nanosheets; The second calcination time in step 1② is 2h~4h; The acid treatment in step 1② is to wash the product after the second calcination with nitric acid at a temperature of 105°C to 120°C for 1h to 3h, then wash it with water until it is neutral and dry it; the concentration of the nitric acid is 5mol / L; 2. Preparation of cyanamide-functionalized CN nanosheets: The ultrathin porous CN nanosheets and dried potassium thiocyanate were mixed and thoroughly ground to obtain a mixture; the mixture was placed in a tube furnace, and under argon atmosphere, the temperature was raised from room temperature to 350°C to 450°C, and the temperature was kept at 350°C to 450°C for 0.5h to 1.5h, and then the temperature was raised to 500°C to 550°C, and the temperature was kept at 500°C to 550°C for 20min to 40min to obtain a reaction product; The reaction product is centrifuged and washed with deionized water to obtain a precipitate; the precipitate is dried to obtain cyanamide-functionalized CN nanosheets; The mass ratio of the ultrathin porous CN nanosheets and dried potassium thiocyanate described in step 2 is (700 mg~900 mg):(1.5 g~1.7 g); Third, the metal phthalocyanine and cyanamide functionalized CN nanosheets were dispersed in anhydrous ethanol, and then heated and stirred until dry to obtain a photocatalytic hydrogen evolution synergistic HMF oxidation photocatalyst; The metal phthalocyanine described in step 3 is nickel phthalocyanine, copper phthalocyanine, zinc phthalocyanine or iron phthalocyanine; The mass ratio of the metal phthalocyanine and the cyanamide functionalized CN nanosheets described in step 3 is (0.1~1):

100.

2. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The mass ratio of melamine described in step 1① to deionized water is (5g~15g):500mL; the mass ratio of cyanuric acid described in step 1① to deionized water is (2g~6g):500mL.

3. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The heating and stirring temperature in step 1 ① is 60 ° C ~ 100 ° C, and the stirring time is 2h ~ 4h; the centrifugal speed in step 1 ① is 4000r / min ~ 6000r / min, and the centrifugal time is 5min ~ 10min.

4. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that In step 1①, the precipitate is dried at 80°C to 100°C for 10 h to 12 h; the heating rate in step 1① is 1°C / min to 3°C / min.

5. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The heating rate described in step 1② is 1°C / min~3°C / min.

6. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The dried potassium thiocyanate in step 2 is potassium thiocyanate vacuum dried at 140° C. for 2 h to 4 h.

7. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The heating rate in step 2 is 5°C / min~15°C / min; in step 2, the precipitated material is dried at 50°C~70°C.

8. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The heating and stirring temperature in step 3 is 50° C. to 70° C., and the stirring speed is 180 r / min to 220 r / min.

9. The method for preparing a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural according to claim 1, characterized in that The volume ratio of the mass of the cyanamide-functionalized CN nanosheets described in step 3 to anhydrous ethanol is (15 mg~30 mg): (40 mL~60 mL).

10. Use of a photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural prepared by the preparation method according to claim 1, characterized in that A photocatalyst for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural is used for photocatalytic hydrogen evolution and synergistic oxidation of 5-hydroxymethylfurfural to produce 2,5-furandicarboxylic acid with high selectivity.

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