Preparation method and application of Pr2O3 / porous graphite phase carbon nitride composite material

Abstract

The invention discloses a kind of preparation method of Pr2O3 / porous graphite phase carbon nitride composite material and its application, belong to inorganic material synthesis and analysis field.The composite material first adopts urea and magnesium sulfate stirring at room temperature reaction and further hydrothermal reaction to prepare porous g-C3N4 precursor after drying, then it is dissolved in ethylene glycol and sodium hydroxide is added and porous g-C3N4 yellow powder product is prepared using solvent thermal reaction, and then praseodymium nitrate is added by liquid phase stirring reaction and after drying, finally solid phase heating reaction is used to prepare.The present invention has few raw material consumption, low cost, and preparation method is simple, without complicated instrument and equipment, reaction conditions are relatively mild, and main preparation link is carried out in aqueous phase, is environmentally friendly, product can significantly enhance the photocatalytic degradation efficiency of bromophenol blue dye, energy saving, consumption reduction and emission reduction, and the catalyst recycling rate constructed by the composite material is higher, and stability and recyclability are good.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and in particular relates to a preparation method and application of a Pr2O3 / porous graphite phase carbon nitride composite material. Background Art

[0002] With the development of science and technology, water pollution is becoming increasingly serious. In particular, some companies produce or use organic dyes that are difficult to degrade due to their complex structure, high stability, strong light resistance, and antioxidant properties. If directly discharged, they can cause significant harm to the environment and human health. Bromophenol blue (BPB) is a typical example of synthetic, difficult-to-degrade organic dyes. It is widely used in industries such as pharmaceuticals, cosmetics, textiles, and printing inks. In some laboratories, it is also used in small quantities as a color marker, acid-base indicator, or agarose gel. Currently, photocatalytic degradation is the primary method for post-processing this dye.

[0003] Semiconductor-based catalysts have been widely used in photocatalytic applications, including carbon dioxide reduction, water splitting, and organic pollutant removal, for decades. Recently, graphitic carbon nitride (g-C3N4) has emerged as one of the most promising candidates for semiconductor photocatalysis due to its thermal and photochemical stability, suitable band gap, low cost, and ease of preparation. Its two-dimensional layered structure, similar to the conjugated structure of graphene, facilitates charge carrier transport. Furthermore, it possesses a narrow band gap (2.70 eV) and can effectively absorb visible light at 460 nm. However, its photocatalytic efficiency is limited by its rapid electron-hole recombination rate, small surface area, and narrow visible light response range. To address this bottleneck, various approaches have been employed, including controlling the porous structure to expand the surface area, copolymerizing with organic compounds, and doping with metal ions, to modulate the surface properties, optical and electronic characteristics, and conduction band edge effects of photocatalysts. This facilitates the separation of photon-generated carriers, reduces the band gap, and enhances visible light absorption.

[0004] Compared with other metal ions, rare earth metal ions can be doped into graphitic carbon nitride to form composite materials. They can use empty 4f orbitals as trap states to promote photoinduced carrier distribution and prevent carrier recombination, thereby improving photocatalytic efficiency, thus having important development prospects. Therefore, praseodymium oxide (Pr2O3), one of the representatives of multivalent lanthanide oxides, was selected as a doping source. Using a small amount of raw materials, a simple preparation method, and mild reaction conditions, it was doped into porous graphitic carbon nitride with a large specific surface area to construct a composite material. The built-in redox center Pr2O3 was used to generate the Pr 3+ / Pr 2+, accelerating the generation of more hydroxyl radicals to participate in the catalytic process, and through the interaction with the organic functional groups of the target dye, it is easy to generate a variety of Lewis base complexes, so that the organic pollutants are concentrated in disguise on the catalyst surface, supplemented by the high separation efficiency of electron-hole pairs, and the synergistic effect is fully exerted, so that the Pr2O3 / porous g-C3N4 composite material exhibits unique catalytic properties in the photodegradation of bromophenol blue. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the existing photocatalytic degradation technology of dyes, such as expensive raw materials for the synthesis of photocatalysts, complex processes, harsh reaction conditions, high degradation energy consumption, long time consumption, and low recycling rate. A new Pr2O3 / porous g-C3N4 composite material with low dosage and strong photocatalytic effect is prepared through inexpensive raw materials, simple reaction processes, relatively mild reaction conditions, a green reaction environment, and an efficient separation method. The porous graphitic carbon nitride with strong thermal and photochemical stability, suitable band gap width, low cost and easy preparation is used as an excellent carrier doped with Pr2O3 microparticles that can enhance visible light absorption, promote electron-hole pair separation efficiency, and indirectly improve the target pollutant loading rate. The synergistic effect is exerted to significantly improve the photodegradation efficiency of bromophenol blue and achieve safe emission.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a Pr2O3 / porous graphite phase carbon nitride composite material, specifically comprising the following steps:

[0008] (1) Preparation of porous g-C3N4 precursor:

[0009] A certain amount of urea and magnesium sulfate were weighed and dissolved in distilled water. After stirring at room temperature, the mixture was dried in an oven. The resulting solid was then placed in a crucible and placed in a muffle furnace to react at a certain temperature for a period of time. After natural cooling, the product was dispersed with a dilute hydrochloric acid solution and continued to stir and react. Finally, the product was washed with water until neutral and dried in an oven to obtain a porous g-C3N4 precursor.

[0010] (2) Preparation of porous g-C3N4:

[0011] A certain amount of the porous g-C3N4 precursor prepared in step (1) was weighed and dispersed in a certain amount of ethylene glycol. An appropriate amount of NaOH was added thereto. After rapid stirring, the mixture was transferred to a reactor and placed in an oven at a certain temperature to react for a period of time. The mixture was naturally cooled to room temperature. The resulting precipitate was rinsed with deionized water and dried to obtain a light yellow powder product.

[0012] (3) Synthesis of Pr2O3 / porous g-C3N4 composite materials:

[0013] A certain amount of porous g-C3N4 powder prepared in step (2) was weighed and dispersed in an appropriate amount of ultrapure water, a certain amount of Pr(NO3)3·6H2O was added and ultrasonically dispersed, heated and stirred to react for a period of time, and after drying, the crucible containing the sample was placed in a muffle furnace and set at a certain temperature for calcination for a period of time. After annealing, a Pr2O3 / porous g-C3N4 composite material was obtained.

[0014] Furthermore, in step (1), the mass ratio of urea to magnesium sulfate is 15-25 g:0.05-0.15 g; and the concentration of the dilute hydrochloric acid solution is 0.4-0.6 mol / L.

[0015] Furthermore, in step (1), the parameters for the reaction at room temperature followed by drying in an oven are as follows: stirring at room temperature for 0.5 to 3 hours, followed by drying in an oven at 80 to 120° C. for 18 to 30 hours.

[0016] Furthermore, the reaction parameters in the muffle furnace in step (1) are: heating at a rate of 4 to 6°C / min to 400 to 600°C for 1 to 4 hours.

[0017] Furthermore, the parameters of the final drying in the oven in step (1) are: drying in the oven at 60-90° C. for 8-15 hours.

[0018] Furthermore, in step (2), the mass ratio of the porous g-C3N4 precursor and NaOH is 0.4-0.6 g: 0.05-0.15 g.

[0019] Furthermore, the reaction parameters in step (2) are: setting the oven at 140-180° C. for reaction for 8-15 hours; and the drying parameters are: drying at 60-90° C. for 8-15 hours.

[0020] Furthermore, in step (3), the mass ratio of the porous g-C3N4 powder and Pr(NO3)3·6H2O is 200 mg:1~6 mg.

[0021] Furthermore, the reaction parameters in step (3) are: stirring reaction at 60-90° C. for 4-8 hours; and the drying parameters are: drying in an oven at 70-100° C. for 1-4 hours.

[0022] Furthermore, the calcination parameters in step (3) are: calcining in a muffle furnace at a heating rate of 3 to 6°C / min to 350 to 450°C for 1 to 4 hours.

[0023] Another object of the present invention is to provide an application of the Pr2O3 / porous g-C3N4 composite material prepared as described above in the field of photocatalytic degradation of bromophenol blue.

[0024] Beneficial effects of the present invention:

[0025] 1. The preparation method of the composite material is simple and does not require complex instruments and equipment; the amount of raw materials used is small and the cost is low; the main preparation steps are carried out in the aqueous phase, which is environmentally friendly;

[0026] 2. The reaction conditions are relatively mild; the post-preparation treatment process is simple and easy to separate and purify;

[0027] 3. The catalyst constructed using this composite material significantly enhances the photocatalytic degradation efficiency of bromophenol blue due to the synergistic effect between the porous graphene-phase carbon nitride with a large specific surface area, high conductivity, and suitable band gap width, and the praseodymium oxide particles with empty 4f orbitals that act as traps to promote electron-hole pair separation, thereby increasing visible light absorption and target enrichment. This results in energy conservation, emission reduction, and environmental protection.

[0028] 4. The catalyst constructed with Pr2O3 / porous g-C3N4 composite material has a high recycling rate and good stability and recyclability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Figure 1 Schematic diagram of the preparation of Pr2O3 / porous g-C3N4 composite material and its application in photocatalytic degradation of bromophenol blue.

[0031] Figure 2 SEM image (A), electron energy spectrum (B) and TEM image (C) of Pr2O3 / porous g-C3N4 composite material (the inner image is the lattice image).

[0032] Figure 3 The XPS total spectrum (A) of the Pr2O3 / porous g-C3N4 composite material and the XPS high-resolution spectra of C1s (B), N1s (C), O 1S (D) and Pr3d (E).

[0033] Figure 4 BET adsorption-desorption curve of Pr2O3 / porous g-C3N4 composite material (A) (the figure in A is the fitted pore size distribution curve) and AC impedance comparison diagram of different materials (B).

[0034] Figure 5 Comparison of the catalytic activity (A) and degradation rate (B) of different materials for the degradation of bromophenol blue under visible light. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] In the following examples, the morphology of the Pr2O3 / porous g-C3N4 composite materials was characterized by a Hitachi F-4800 scanning electron microscope (SEM) and a Hitachi HT-7700 transmission electron microscope. The surface elements, content and chemical valence of the composite materials were analyzed by a PHI Quantera II X-ray photoelectron spectroscopy (XPS). The AC impedance test was performed on a CHI1650 electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. The experiment adopted a three-electrode system (i.e., a glassy carbon electrode modified with each material as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire electrode as the counter electrode). The photocatalytic degradation experiment of bromophenol blue was carried out using a CME-PC6 photocatalytic instrument (500W) produced by China Science Micro Energy (Beijing) Technology Co., Ltd.

[0037] 1. Preparation method of Pr2O3 / porous g-C3N4 composite material (such as Figure 1 shown):

[0038] Example 1

[0039] (1) Weigh 15 g of urea and 0.05 g of magnesium sulfate and dissolve them in 20 mL of distilled water. Stir at room temperature for 0.5 h and then dry in an oven at 80 °C for 30 h.

[0040] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 4°C / min to 400°C for 1 hour and then cooled naturally.

[0041] (3) Disperse the product with 0.4 mol / L dilute hydrochloric acid solution and stir for 1 h, then wash with water until neutral, and dry in an oven at 60 °C for 15 h;

[0042] (4) Weigh 0.4 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 40 mL of ethylene glycol. Add 0.05 g of NaOH and stir rapidly for 1 h. Then transfer it to a reactor and place it in an oven set at 140 °C for 15 h, then cool it naturally to room temperature.

[0043] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0044] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 1 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat it to 60°C and stir it for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0045] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0046] Example 2

[0047] (1) Weigh 18 g of urea and 0.08 g of magnesium sulfate and dissolve them in 25 mL of distilled water. Stir at room temperature for 1 h and then dry in an oven at 90 °C for 26 h.

[0048] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 4.5°C / min to 400°C for 1 hour and then cooled naturally.

[0049] (3) Disperse the product with 0.4 mol / L dilute hydrochloric acid solution and stir for 1 h, then wash with water until neutral, and dry in an oven at 60 °C for 15 h;

[0050] (4) Weigh 0.4 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 40 mL of ethylene glycol. Add 0.05 g of NaOH and stir rapidly for 1 h. Then transfer it to a reactor and place it in an oven set at 140 °C for 15 h, then cool it naturally to room temperature.

[0051] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0052] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 2 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat to 60°C and stir to react for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0053] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0054] Example 3

[0055] (1) Weigh 15 g of urea and 0.05 g of magnesium sulfate and dissolve them in 20 mL of distilled water. Stir at room temperature for 0.5 h and then dry in an oven at 80 °C for 30 h.

[0056] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 4°C / min to 400°C for 1 hour and then cooled naturally.

[0057] (3) Disperse the product with 0.5 mol / L dilute hydrochloric acid solution and stir for 2 h, then wash with water until neutral, and dry in an oven at 70 °C for 12 h;

[0058] (4) Weigh 0.5 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 50 mL of ethylene glycol. Add 0.08 g of NaOH and stir rapidly for 2 h. Then transfer it to a reactor and place it in an oven set at 150 °C for 12 h, then cool it naturally to room temperature.

[0059] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0060] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 4 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat it to 60°C and stir it for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0061] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0062] Example 4

[0063] (1) Weigh 15 g of urea and 0.05 g of magnesium sulfate and dissolve them in 20 mL of distilled water. Stir at room temperature for 0.5 h and then dry in an oven at 80 °C for 30 h.

[0064] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 4°C / min to 400°C for 1 hour and then cooled naturally.

[0065] (3) Disperse the product with 0.4 mol / L dilute hydrochloric acid solution and stir for 1 h, then wash with water until neutral, and dry in an oven at 60 °C for 15 h;

[0066] (4) Weigh 0.4 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 40 mL of ethylene glycol. Add 0.05 g of NaOH and stir rapidly for 1 h. Then transfer it to a reactor and place it in an oven set at 140 °C for 15 h, then cool it naturally to room temperature.

[0067] (5) The resulting precipitate was rinsed with deionized water and dried at 70 °C for 12 h to obtain a light yellow powdery product;

[0068] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 15 mL of ultrapure water. Add 4 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 10 min. Heat it to 70°C and stir it for 6 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0069] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 400 °C at a heating rate of 4 °C / min for 3 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0070] Example 5

[0071] (1) Weigh 20 g of urea and 0.10 g of magnesium sulfate and dissolve them in 25 mL of distilled water. Stir at room temperature for 1 h and then dry in an oven at 100 °C for 24 h.

[0072] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 5°C / min to 500°C for 2 h and then cooled naturally.

[0073] (3) Disperse the product with 0.4 mol / L dilute hydrochloric acid solution and stir for 1 h, then wash with water until neutral, and dry in an oven at 60 °C for 15 h;

[0074] (4) Weigh 0.4 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 40 mL of ethylene glycol. Add 0.05 g of NaOH and stir rapidly for 1 h. Then transfer it to a reactor and place it in an oven set at 140 °C for 15 h, then cool it naturally to room temperature.

[0075] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0076] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 6 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat to 60°C and stir to react for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0077] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0078] Example 6

[0079] (1) Weigh 20 g of urea and 0.10 g of magnesium sulfate and dissolve them in 25 mL of distilled water. Stir at room temperature for 1 h and then dry in an oven at 100 °C for 24 h.

[0080] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 5°C / min to 500°C for 2 h and then cooled naturally.

[0081] (3) Disperse the product with 0.5 mol / L dilute hydrochloric acid solution and stir for 2 h, then wash with water until neutral, and dry in an oven at 70 °C for 12 h;

[0082] (4) Weigh 0.5 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 50 mL of ethylene glycol. Add 0.1 g of NaOH and stir rapidly for 3 h. Then transfer it to a reactor and place it in an oven set at 150 °C for 12 h, then cool it naturally to room temperature.

[0083] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0084] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 6 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat to 60°C and stir to react for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0085] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0086] Example 7

[0087] (1) Weigh 20 g of urea and 0.10 g of magnesium sulfate and dissolve them in 25 mL of distilled water. Stir at room temperature for 1 h and then dry in an oven at 100 °C for 24 h.

[0088] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 5°C / min to 500°C for 2 h and then cooled naturally.

[0089] (3) Disperse the product with 0.5 mol / L dilute hydrochloric acid solution and stir for 2 h, then wash with water until neutral, and dry in an oven at 70 °C for 12 h;

[0090] (4) Weigh 0.5 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 50 mL of ethylene glycol. Add 0.1 g of NaOH and stir rapidly for 3 h. Then transfer it to a reactor and place it in an oven set at 150 °C for 12 h, then cool it naturally to room temperature.

[0091] (5) The resulting precipitate was rinsed with deionized water and dried at 80 °C for 12 h to obtain a light yellow powdery product;

[0092] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 15 mL of ultrapure water. Add 1 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 8 min. Heat to 70°C and stir for 6 h. Then transfer it to an oven set at 80°C and dry it for 3 h.

[0093] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 4 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0094] Example 8

[0095] (1) Weigh 25 g of urea and 0.15 g of magnesium sulfate and dissolve them in 30 mL of distilled water. Stir at room temperature for 2 h and then dry in an oven at 120 °C for 20 h.

[0096] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 6°C / min to 600°C for 1 h and then cooled naturally.

[0097] (3) Disperse the product with 0.5 mol / L dilute hydrochloric acid solution and stir for 2 h, then wash with water until neutral, and dry in an oven at 70 °C for 12 h;

[0098] (4) Weigh 0.5 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 50 mL of ethylene glycol. Add 0.1 g of NaOH and stir rapidly for 3 h. Then transfer it to a reactor and place it in an oven set at 150 °C for 12 h, then cool it naturally to room temperature.

[0099] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0100] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 2 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat to 60°C and stir to react for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0101] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0102] Example 9

[0103] (1) Weigh 25 g of urea and 0.15 g of magnesium sulfate and dissolve them in 30 mL of distilled water. Stir at room temperature for 2 h and then dry in an oven at 120 °C for 20 h.

[0104] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 6°C / min to 600°C for 1 h and then cooled naturally.

[0105] (3) Disperse the product with 0.6 mol / L dilute hydrochloric acid solution and stir for 1.5 h, then wash with water until neutral, and dry in an oven at 80 °C for 8 h;

[0106] (4) Weigh 0.6 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 60 mL of ethylene glycol. Add 0.15 g of NaOH and stir rapidly for 4 h. Then transfer it to a reactor and place it in an oven set at 180 °C for 8 h. Then cool it naturally to room temperature.

[0107] (5) The resulting precipitate was rinsed with deionized water and dried at 60 °C for 15 h to obtain a light yellow powdery product;

[0108] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 10 mL of ultrapure water. Add 4 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 5 min. Heat it to 60°C and stir it for 8 h. Then transfer it to an oven set at 70°C and dry it for 4 h.

[0109] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 350 °C at a heating rate of 3 °C / min for 4 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0110] Example 10

[0111] (1) Weigh 25 g of urea and 0.15 g of magnesium sulfate and dissolve them in 30 mL of distilled water. Stir at room temperature for 2 h and then dry in an oven at 120 °C for 20 h.

[0112] (2) The obtained solid was placed in a crucible and placed in a muffle furnace at a heating rate of 6°C / min to 600°C for 1 h and then cooled naturally.

[0113] (3) Disperse the product with 0.6 mol / L dilute hydrochloric acid solution and stir for 1.5 h, then wash with water until neutral, and dry in an oven at 80 °C for 8 h;

[0114] (4) Weigh 0.6 g of the porous g-C3N4 precursor prepared in step (3) above and disperse it in 60 mL of ethylene glycol. Add 0.15 g of NaOH and stir rapidly for 4 h. Then transfer it to a reactor and place it in an oven set at 180 °C for 8 h. Then cool it naturally to room temperature.

[0115] (5) The resulting precipitate was washed with deionized water and dried at 90 °C for 8 h to obtain a light yellow powdery product;

[0116] (6) Weigh 200 mg of the porous g-C3N4 powder prepared in step (5) and disperse it in 20 mL of ultrapure water. Add 6 mg of Pr(NO3)3·6H2O and ultrasonically disperse it for 20 min. Heat to 90°C and stir to react for 5 h. Then transfer it to an oven set at 100°C and dry it for 1 h.

[0117] (7) Finally, the crucible containing the sample was placed in a muffle furnace and calcined to 450 °C at a heating rate of 6 °C / min for 2 h. After annealing, the Pr2O3 / porous g-C3N4 composite material was obtained.

[0118] 2. Evaluation of the photocatalytic degradation effect of Pr2O3 / porous g-C3N4 composites on bromophenol blue

[0119] (1) The morphology of Pr2O3 / porous g-C3N4 composites was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 2 As shown), the SEM image of the composite material ( Figure 2 A) It can be seen that the white spherical particles Pr2O3 are evenly distributed on the surface of the wrinkled porous C3N4, and the corresponding electron energy spectrum results ( Figure 2 B) also confirmed that the composite material contains C, N, O and Pr elements. TEM image of Pr2O3 / porous g-C3N4 composite material ( Figure 2 C) clearly observed that the black spherical particles of Pr2O3 were successfully loaded onto the transparent porous C3N4 surface. Figure 2 After enlarging the bright and dark parts in C, the lattice spacing is calculated to be approximately 0.294nm ( Figure 2 C), which corresponds exactly to the (112) crystal plane of Pr2O3.

[0120] (2) X-ray photoelectron spectroscopy (XPS) was used to study the elemental composition and chemical state of Pr2O3 / porous g-C3N4 composite materials. Figure 3 shown. Figure 3A is the total spectrum of the composite material, and it can be seen that C1s, N 1s, O 1s and Pr 3d spectral lines are clearly present in the composite material. Peak fitting C1s spectrum ( Figure 3 B) and found that the energy spectrum peaks at 284.68eV and 287.88eV correspond to the sp of C in the coupling CC and NC=C. 2 hybridization; Figure 3 The N1s characteristic spectrum in C can be fitted with three peaks, which are located at 398.28, 399.88 and 400.78 eV respectively. The first two peaks may correspond to the sp 2 The N-C=C bond and C-(N)3 bond formed by hybridization, and the peak at 400.78eV corresponds to the CNH bond in the composite material; Figure 3 D shows that the O1s high-resolution spectrum fitting peak in the composite material is located at 531.3 eV, corresponding to the C=O bond in the composite material; Figure 3 The two characteristic peaks of Pr2O3 in E are located at 932.28 and 954.08 eV, which correspond to Pr 3+ 3D 5 / 2 and 3D 3 / 2 The above characterization results confirmed that the composite material was successfully prepared.

[0121] (3) The specific surface area and porous structure of porous g-C3N4 and Pr2O3 / porous g-C3N4 composite materials (when the mass percentage of Pr2O3 loaded in the composite material is 2%, it is marked as 2% PCN) were analyzed by N2 adsorption-desorption experiments. Figure 4 As shown in A, the samples all show type IV isothermal model curves and have H3 type hysteresis loops, indicating that there are irregular pores in the material. From the pore size distribution curve ( Figure 4 As can be seen from the figure in Figure A, most of the pores are mesopores. The specific surface area of ​​the composite material (94.7924m 2 / g) is much larger than the specific surface area of ​​porous g-C3N4 (65.1976m 2 / g) is large, and the corresponding pore volume is also large, which is expected to increase the active site area on the surface of the composite material and help improve the photocatalytic efficiency; In addition, electrochemical impedance spectroscopy (EIS) characterization was used to explore the charge transfer behavior of different materials. Figure 4 B) As can be seen, the bare glassy carbon electrode is almost a straight line throughout the high-frequency range, indicating that the bare glassy carbon electrode has a low resistance. After the electrode is modified with a Pr2O3 / porous g-C3N4 composite, it exhibits a semicircular arc with a much smaller Nyquist diameter than the single Pr2O3 and single porous g-C3N4 composites in the high-frequency range, which is closer to that of the bare glassy carbon electrode. This indicates that the combination of Pr2O3 and porous g-C3N4 can improve the conductivity of the single material, resulting in lower solid-state interface resistance and faster electron transfer.

[0122] (4) In order to study the catalytic effect of the prepared composite material in the degradation of organic dyes, the photocatalytic degradation of bromophenol blue was studied under visible light. That is, a pre-prepared bromophenol blue solution (10 mg / L) was added to a beaker, and then 10 mg of the prepared catalyst was added. After ultrasonic dispersion for 5 minutes, the mixture was stirred in the dark for 30 minutes to allow the catalyst and dye to reach adsorption and desorption equilibrium. A 420 nm filter was used to filter out ultraviolet light. The experiment was carried out under visible light irradiation. Samples were collected every 10 minutes, and the solution after centrifugation was used for spectral analysis. Figure 5 A is a comparison chart of the catalytic activity of photodegradation of bromophenol blue calculated based on the spectra of bromophenol blue degradation by different materials under visible light. It can be seen from the figure that the catalytic activity of porous g-C3N4 is improved after loading Pr2O3. Among them, when the mass percentage of Pr2O3 loaded in the composite material reaches 2% (marked as 2% PCN, and other composite materials with different mass percentages are marked in this way), its catalytic activity reaches the highest. Figure 5 B is the degradation rate diagram of a series of materials obtained by linear fitting of first-order reaction kinetics. The results show that the catalytic rate of the prepared materials for the degradation of bromophenol blue under visible light is in the following order: 2% PCN>3% PCN>1% PCN>0.5% PCN>porous g-C3N4. Pr2O3 has almost no photocatalytic effect. The degradation rate of the Pr2O3 / porous g-C3N4 composite material with a mass percentage of 2% Pr2O3 calculated by K value is 0.04582min -1 ) is a single porous g-C3N4 material (0.01407min -1) is 4.28 times that of the previous study. This indicates that the loading of Pr2O3 on the surface of porous g-C3N4 does improve its catalytic activity in the degradation of bromophenol blue under visible light. Compared with other existing catalysts (Moussaid D, Khallouk K, Tagnaouti Moumnani F, Fahoul Y, Tanji K, Barakat A, Kherbeche A, Beniazza R. High photocatalytic activity and stability of MnV2O6 and Mn2V2O7 synthesized by simple low temperature method for bromophenol blue degradation[J]. Journal of Photochemistry and Photobiology A: Chemistry, 2023, 444: 114922-114935 and Khan Z, Ali F, Said A, Arif U, Khan K, Ali N, Shabir G. Polyethylene glycol capped copper ferrite porous nanostructured materials for efficient photocatalytic degradation of bromophenol blue[J]. Environmental Research, 2022, 215: 114148-114155), the catalyst constructed by the composite material with a mass percentage of 2% loaded Pr2O3 on porous g-C3N4 has a small amount of use, short time consumption and high degradation completeness for the photodegradation reaction of bromophenol blue.

[0123] (5) In order to study the number of times the composite material can be reused as a catalyst, the cyclic performance of the Pr2O3 / porous g-C3N4 composite material with a loading mass percentage of 2% was tested. It was found that when the catalyst was used for the first time, the degradation rate of bromophenol blue was close to 100%. As the number of cycles increased, the catalytic ability of the material decreased. However, after four cycles, the degradation effect of bromophenol blue was always maintained at more than 80%, indicating that the prepared composite material has good stability and reusability.

[0124] The above detailed description of the analytical methods involved in the present invention provides a detailed introduction. It should be noted that the above description is intended solely to help those skilled in the art better understand the methods and concepts of the present invention, and is not intended to limit the relevant content. Without departing from the principles of the present invention, those skilled in the art may make appropriate adjustments or modifications to the present invention, and such adjustments and modifications shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Pr2O3 / porous graphite phase carbon nitride composite material, characterized in that: The following steps are involved: (1) Preparation of porous g-C3N4 precursor: A certain amount of urea and magnesium sulfate were weighed and dissolved in distilled water. After stirring at room temperature, the mixture was dried in an oven. The resulting solid was then placed in a crucible and placed in a muffle furnace to react at a certain temperature for a period of time. After natural cooling, the product was dispersed with a dilute hydrochloric acid solution and continued to stir and react. Finally, the product was washed with water until neutral and dried in an oven to obtain a porous g-C3N4 precursor. (2) Preparation of porous g-C3N4: A certain amount of the porous g-C3N4 precursor prepared in step (1) was weighed and dispersed in a certain amount of ethylene glycol. An appropriate amount of NaOH was added thereto. After rapid stirring, the mixture was transferred to a reactor and placed in an oven at a certain temperature to react for a period of time. The mixture was naturally cooled to room temperature. The resulting precipitate was rinsed with deionized water and dried to obtain a light yellow powder product. (3) Synthesis of Pr2O3 / porous g-C3N4 composite materials: A certain amount of porous g-C3N4 powder prepared in step (2) was weighed and dispersed in an appropriate amount of ultrapure water, a certain amount of Pr(NO3)3·6H2O was added and ultrasonically dispersed, heated and stirred to react for a period of time, and after drying, the crucible containing the sample was placed in a muffle furnace and set at a certain temperature for calcination for a period of time. After annealing, a Pr2O3 / porous g-C3N4 composite material was obtained.

2. The method for preparing a Pr2O3 / porous graphite phase carbon nitride composite material according to claim 1, characterized in that: In step (1), the mass ratio of urea to magnesium sulfate is 15-25 g:0.05-0.15 g; and the concentration of the dilute hydrochloric acid solution is 0.4-0.6 mol / L.

3. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: The parameters for the step (1) of stirring the reaction at room temperature and then placing it in an oven for drying are: stirring at room temperature for 0.5 to 3 hours and then placing it in an oven for drying at 80 to 120° C. for 18 to 30 hours.

4. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: The reaction parameters in the muffle furnace in step (1) are: heating to 400-600° C. at a heating rate of 4-6° C. / min for 1-4 hours.

5. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: In step (2), the mass ratio of the porous g-C3N4 precursor and NaOH is 0.4-0.6 g: 0.05-0.15 g.

6. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: The reaction parameters in step (2) are: setting the oven at 140-180° C. for reaction for 8-15 hours; and the drying parameters are: drying at 60-90° C. for 8-15 hours.

7. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: In step (3), the mass ratio of porous g-C3N4 powder and Pr(NO3)3·6H2O is 200 mg:1~6 mg.

8. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: The reaction parameters in step (3) are: stirring reaction at 60-90° C. for 4-8 hours; and drying parameters are: drying in an oven at 70-100° C. for 1-4 hours.

9. The method for preparing a Pr2O3 / porous graphite-phase carbon nitride composite material according to claim 1, characterized in that: The calcination parameters in step (3) are: calcining in a muffle furnace at a heating rate of 3 to 6°C / min to 350 to 450°C and calcining for 1 to 4 hours.

10. Use of the Pr2O3 / porous g-C3N4 composite material prepared by the method according to any one of claims 1 to 9 in the field of photocatalytic degradation of bromophenol blue.

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