Preparation of Cs and cyano-codoped yellow g-C3N4 and application of Cs and cyano-codoped yellow g-C3N4 in photocatalytic production of hydrogen peroxide

Abstract

The invention discloses preparation of Cs and cyano-codoped yellow g-C3N4 and application of the Cs and cyano-codoped yellow g-C3N4 in photocatalytic production of hydrogen peroxide. The method comprises the following steps: weighing a certain amount of cesium bromide, mixing the cesium bromide with a certain amount of urea, and uniformly grinding; putting the sample into a quartz crucible, and covering the quartz crucible with a quartz cover; putting the mixture into a muffle furnace, heating to 500-600 DEG C within 100-120 minutes, preserving heat for 2 hours at the temperature, and naturally cooling to room temperature, so as to obtain the Cs-g-C3N4 photocatalytic material. According to the preparation method, CsBr is used as a doping agent, Cs2 + is released near the polymerization temperature of urea, a homojunction of g-C3N4 is prepared, and the homojunction has excellent photocatalytic hydrogen peroxide production performance.

Description

Technical Field

[0001] The present invention relates to a photocatalytic material, in particular to a yellow gC co-doped with Cs and cyanide. 3 N 4 Preparation and application of photocatalytic hydrogen peroxide production Background Art

[0002] Traditional industrial preparation of hydrogen peroxide mostly relies on the anthraquinone method. Although this process is mature, the process is lengthy and complicated, involving a large amount of organic solvents. It not only has high energy consumption and huge equipment investment, but is also prone to causing thorny environmental problems such as chemical leakage and pollution emissions. It is difficult to comply with increasingly stringent environmental regulations and sustainable development demands.

[0003] At the same time, the wave of clean energy transformation is sweeping the world, and solar energy has attracted much attention for its significant advantages of being inexhaustible, clean and zero-carbon. Photocatalytic technology can cleverly build a bridge between solar energy utilization and green synthesis of chemicals, opening up a new path for hydrogen peroxide production. In the process of deepening scientific research and exploration, many semiconductor photocatalytic materials have emerged, such as titanium dioxide and cadmium sulfide. They can excite electron-hole pairs under light, drive water and oxygen to undergo redox reactions, and accurately synthesize hydrogen peroxide. The whole process is gentle and free of high temperature and high pressure stress, and does not require complicated additives, which greatly reduces production costs and pollution risks from the source.

[0004] C 3 N 4 It is a typical polymer semiconductor. The C and N atoms in its structure are sp 2 Hybridization forms a highly delocalized π-conjugated system with a planar two-dimensional sheet structure similar to graphene. It has the characteristics of suitable bandgap width (~2.7eV), no metal, low cost, good chemical stability, etc. Since 2014, scientists have discovered that carbon nitride has a good performance in photocatalytic H 2 O 2 However, due to the limitation of fast charge recombination, the photocatalytic production of H in pristine carbon nitride is 2 O 2 The efficiency is still unsatisfactory. For this reason, scientists have proposed different strategies to solve the carbon nitride problem, such as generating heterojunctions, increasing structural defects, and constructing nanostructured carbon nitride. Zhou et al. used bamboo fibers to produce hybrid C / gC with enhanced photocatalytic activity. 3 N 4 Photocatalyst and H 2 O 2 The production rate is higher than that of pure gC without any sacrificial agent. 3 N 46.2 times higher (Zhou J, ShanT, Luo H, et al.Enhanced single-electron transfer for efficiently photocatalytic H 2 O 2 production over gC 3 N 4 decorated with TEMPO-oxidized cellular carbon[J].Journal of Environmental Chemical Engineering,2023,11(2):109512). In order to improve the efficiency of carbon nitride in producing hydrogen peroxide, the method of introducing defects is also a common modification method. Recently, Fabrice et al. introduced nitrogen defects and alkali metal doping, and inspired the design of modified carbon nitride photocatalysts by precisely controlling structural defects and foreign element doping (Habarugira FN,Yao D,Miao W,et al.Synergy ofsodium do**and nitrogen defects in carbon nitride for promoted photocatalytic synthesis of hydrogen peroxide[J].Chinese Chemical Letters,2024,35(8):109886). However, although many methods have been found to improve gC 3 N 4 However, so far, the photocatalytic performance of gC 3 N 4 The industrial production of hydrogen peroxide remains challenging. Summary of the invention

[0005] The purpose of the present invention is to provide a yellow gC co-doped with Cs and cyanide. 3 N 4 Preparation and application of photocatalytic hydrogen peroxide production by controlling Cs 2+ Doped gC 3 N 4 , improve gC 3 N 4 Photocatalytic performance of hydrogen peroxide production.

[0006] In order to achieve the above object, the present invention provides a Cs-gC 3 N 4The preparation method of the photocatalytic material comprises: mixing CsBr and urea, and grinding them thoroughly. Placing them in a quartz crucible with a diameter of 25 mm, covering them with a quartz cover, and placing them in a muffle furnace, heating them at 500-550° C., and cooling them to room temperature after the reaction is completed to obtain Cs-gC 3 N 4 Photocatalytic materials.

[0007] Preferably, the molar ratio of CsBr to urea is 1:20 to 1:170.

[0008] Preferably, the heating rate is 40-70°C / min.

[0009] Preferably, the heating to 500° C. to 600° C. is maintained for 2 hours.

[0010] Preferably, after the material is synthesized, alcohol is used to disperse the solid, and then solid-liquid separation is performed to remove unreacted substances.

[0011] Another object of the present invention is to provide Cs-gC prepared by the method 3 N 4 Photocatalytic materials.

[0012] Another object of the present invention is to provide the Cs-gC 3 N 4 Application of photocatalytic materials in photocatalytic production of hydrogen peroxide.

[0013] The Cs-gC of the present invention 3 N 4 Photocatalytic materials and their preparation and application have the following advantages:

[0014] (1) The present invention uses CsBr as a dopant to release Cs near the urea polymerization temperature. 2+ , prepare gC 3 N 4 The homojunction has excellent photocatalytic performance in producing hydrogen peroxide;

[0015] (2) The present invention adopts a one-step calcination method, uses relatively low-priced urea as a precursor, and prepares Cs-gC in large quantities through a simple synthesis process. 3 N 4 Photocatalytic materials;

[0016] (3) The present invention controls the gC 3 N 4 The molar ratio with CsBr, reaction temperature and calcination time can control the catalyst size and band gap. The preparation method has strong controllability, easy controllable process parameters, is safe, green, pollution-free and has high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The XRD patterns of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention are shown.

[0018] Figure 2 This is an EDS analysis result diagram of the composition of the photocatalytic materials prepared in Example 1 and Example 2 of the present invention.

[0019] Figure 3 The UV-visible absorption spectra of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention.

[0020] Figure 4 This is a graph showing the relationship between the amount of hydrogen peroxide produced by visible light photocatalysis and time for the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention.

[0021] Figure 5 This is a photocatalytic hydrogen peroxide production rate diagram of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention.

[0022] Figure 6 The graph is a relationship between the amount of hydrogen peroxide produced by visible light photocatalysis and time of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention, and a scanning electron microscope image of the photocatalytic material prepared in Example 1. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A Cs-gC 3 N 4 The preparation method of the photocatalytic material is as follows:

[0026] 0.8 g of CsBr powder was mixed with 10 g of urea and ground thoroughly. The mixture was collected in a quartz crucible, covered in a muffle furnace, heated to 500-600 °C at a heating rate of 40-70 °C / min, maintained for 2 h, and then naturally cooled to room temperature to obtain Cs-gC 3 N 4 Photocatalytic materials.

[0027] Example 2

[0028] A Cs-gC 3 N 4The preparation method of the photocatalytic material is as follows:

[0029] 0.4 g of CsBr powder was mixed with 10 g of urea and ground thoroughly. The mixture was collected in a quartz crucible, covered in a muffle furnace, heated to 500-600 °C at a heating rate of 40-70 °C / min, maintained for 2 h, and then naturally cooled to room temperature to obtain Cs-gC 3 N 4 Photocatalytic materials.

[0030] Comparative Example 1

[0031] A Cs-gC 3 N 4 The preparation method of the photocatalytic material is as follows:

[0032] 0.2 g of CsBr powder was mixed with 10 g of urea and ground thoroughly. The mixture was collected in a quartz crucible, covered in a muffle furnace, heated to 500-600 °C at a heating rate of 40-70 °C / min, maintained for 2 h, and then naturally cooled to room temperature to obtain Cs-gC 3 N 4 Photocatalytic materials.

[0033] Comparative Example 2

[0034] A gC 3 N 4 The preparation method of the photocatalytic material is as follows:

[0035] 10g urea was ground into powder, and the powder was collected in a quartz crucible. The crucible was covered with a lid and heated to 500℃~600℃ at a heating rate of 40~70℃ / min. After maintaining for 2h, it was naturally cooled to room temperature to obtain gC 3 N 4 Photocatalytic materials.

[0036] Comparative Example 3

[0037] A Cs-gC 3 N 4 The preparation method of the photocatalytic material is as follows:

[0038] Mix 1.6 g of CsBr powder with 10 g of urea and grind thoroughly. Collect the mixture into a quartz crucible, cover it with a lid, heat it to 500-600 °C at a rate of 40-70 °C / min, maintain for 2 h, and then cool it naturally to room temperature to obtain Cs-gC 3 N 4 Photocatalytic materials.

[0039] like Figure 1As shown in the figure, the XRD spectra of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention (in the figure, the abscissa is the diffraction angle and the ordinate is the relative intensity). It can be seen from the figure that after calcination, the embodiments maintain gC 3 N 4 The diffraction peaks at 2θ=13.0°(100) and 27.5°(002) form the characteristic peaks of CsBr, while the comparative example conforms to the typical XRD characteristic peaks of g-CN.

[0040] like Figure 2 As shown, it is the EDS analysis result diagram of the composition of the photocatalytic materials prepared in Example 1 and Comparative Example 2 of the present invention. It can be seen from the figure that the weight percentages of C, N and O in Example 1 are 32.24%, 61.09% and 6.67% respectively, and the weight percentages of C, N and O in Comparative Example 2 are 36.44%, 61.34% and 2.23% respectively.

[0041] like Figure 3 As shown, the ultraviolet-visible absorption spectra of the photocatalytic materials prepared by Examples 1-2 of the present invention and Comparative Examples 1-2. It can be seen from the figure that the absorption edge of the photocatalytic materials prepared by Examples 1 and 2 shows an obvious red shift compared with Comparative Examples 1-2, and the light absorption in the visible light region (450nm~800nm) is stronger than that of Comparative Example 2, and more visible light can be utilized, which is beneficial to the photocatalytic reaction.

[0042] Experimental Example 1 Photocatalytic production of hydrogen peroxide

[0043] The photocatalytic hydrogen peroxide production experiment was carried out in an open glass circulation system. The specific process is as follows:

[0044] Disperse 20 mg of photocatalyst (photocatalytic material prepared in each embodiment or comparative example) in 50 mL of pure water solution, and stir with a rotor to make the solution uniformly dissolved. Use circulating cooling water to control the temperature at 6°C, and then use a xenon lamp (300W) to irradiate for 0.25 to 2 hours, and take samples for analysis at regular intervals. The amount of hydrogen peroxide produced is detected on a UV analyzer, using potassium ions to react with hydrogen peroxide for color development, and then using a UV analyzer to indirectly monitor the amount of hydrogen peroxide in the solution.

[0045] like Figure 4 As shown in the figure, it is a relationship diagram between the amount of hydrogen evolution under visible light and time of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention. It can be seen from the figure that the amount of hydrogen peroxide produced in Example 1 (0.8Cs-gC 3 N 4 )> Example 2 production of hydrogen peroxide (0.4Cs-gC 3 N 4)>Hydrogen peroxide production of comparative example 1 (0.2Cs-gC 3 N 4 )>The hydrogen peroxide production of Comparative Examples 2 and 3.

[0046] like Figure 5 As shown in the figure, the photocatalytic hydrogen peroxide production rate diagram of the photocatalytic materials prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention is as follows. It can be seen from the figure that Comparative Example 3 (1.6Cs-gC 3 N 4 The material prepared by the comparative example 1 (0.2Cs-gC 3 N 4 ) produced 5512 μM·g -1 ·h -1 ; The material prepared in Comparative Example 2 (gC 3 N 4 ) produced 3856 μM·g -1 ·h -1 ; Material prepared in Example 1 (0.8Cs-gC 3 N 4 The amount of hydrogen peroxide produced by the photocatalytic material is 25220 μM g -1 ·h -1 ; Material prepared in Example 2 (0.4Cs-gC 3 N 4 The amount of hydrogen peroxide produced by the photocatalytic material is 19348 μM·g -1 ·h -1 Obviously, the amount of hydrogen peroxide produced by the photocatalytic materials prepared in Examples 1 and 2 of the present invention is significantly higher than that in Comparative Examples 1-3, and the hydrogen peroxide production performance is excellent.

[0047] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. Preparation of yellow g-C3N4 co-doped with Cs and cyanide, characterized in that: The method includes: CsBr and urea were mixed and ground thoroughly, placed in a quartz crucible with a diameter of 25 mm, covered with a quartz cover and placed in a muffle furnace, heated at 550°C, and after the reaction was completed, cooled to room temperature to obtain a Cs-g-C3N4 photocatalytic material.

2. The method for preparing the Cs-g-C3N4 photocatalytic material according to claim 1, characterized in that: The molar ratio range of CsBr to urea.

3. The method for preparing the Cs-g-C3N4 photocatalytic material according to claim 1, characterized in that: The heating rate is 5°C / min.

4. The method for preparing the Cs-g-C3N4 photocatalytic material according to claim 1, characterized in that: The heating to 550° C. was maintained for 2 h.

5. The method for preparing the Cs-g-C3N4 photocatalytic material according to any one of claims 1 to 4, characterized in that: After the synthesis, the Cs-g-C3N4 is dispersed in ethanol and solid-liquid separated to remove unreacted substances.

6. Cs-g-C3N4 photocatalytic material prepared by the method according to any one of claims 1 to 5.

7. Use of the Cs-g-C3N4 photocatalytic material as claimed in claim 6 in photocatalytic production of hydrogen peroxide.

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