Preparation method of nonmetal B and F doped carbon nitride material and application of nonmetal B and F doped carbon nitride material in photocatalytic nitrogen fixation

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method of a nonmetal B and F doped carbon nitride material and application of the nonmetal B and F doped carbon nitride material in photocatalytic nitrogen fixation. Comprising the following steps: dissolving boron trifluoride diethyl etherate and melamine in dichloromethane, stirring at room temperature until the dichloromethane solvent is completely volatilized, calcining the obtained substance in a muffle furnace, cooling to room temperature, and uniformly grinding to obtain the nonmetal B and F doped C3N4 photocatalyst. The B and F atoms provide active sites for the photocatalytic nitrogen reduction reaction, the reaction band gap is reduced, the separation of photo-induced electron holes is promoted, and the photocatalytic nitrogen fixation performance is improved. The method is simple in process operation, mild in reaction condition and wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and in particular relates to a preparation method of a non-metallic B and F doped carbon nitride material and an application thereof in photocatalytic nitrogen fixation. Background Art

[0002] Nitrogen accounts for up to 78% of the atmospheric environment and is an essential element for almost all forms of life on Earth. Nitrogen and its compounds are widely used in life and production.

[0003] Ammonia is a green energy carrier and a raw material for agriculture, industry, medicine and other fields. Natural nitrogen fixation alone is not enough. The Haber-Bosch reaction is a major achievement in artificial nitrogen fixation technology worldwide. The Haber-Bosch reaction is carried out under high temperature and high pressure conditions, consuming a lot of energy and producing a lot of carbon dioxide in the process. The N≡N bond energy in nitrogen is as high as 972 kJ·mol -1 Therefore, seeking efficient, low-energy, and clean methods for nitrogen fixation and ammonia synthesis has become a research hotspot in recent years.

[0004] Photocatalytic nitrogen fixation is a new technology that uses solar energy to reduce N2 to NH3 under mild reaction conditions, and has broad application prospects. Carbon nitride is one of the research focuses of photocatalytic nitrogen fixation due to its physicochemical stability, low cost, environmental friendliness, simple process, suitable energy gap and adjustable electronic properties. However, due to the rapid recombination of photoinduced electron-hole pairs, poor active sites and weak charge migration pathways, the actual photocatalytic efficiency of carbon nitride is greatly inhibited when applied on a large scale. In order to solve these problems, methods such as element doping (S, O, P, B), introduction of defects or vacancies, morphology control and heterojunction design are used to modify carbon nitride. It is worth noting that the doping of non-metallic elements can effectively adjust the electronic structure and surface properties of the material while maintaining the thermal stability and metal-free properties of the material.

[0005] Therefore, we will utilize non-metallic B and F doped carbon nitride photocatalysts for photocatalytic nitrogen fixation. The carbon nitride material with simple preparation method is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to synthesize ammonia using a low-energy, low-cost, green method and to design non-metallic B and F-doped carbon nitride photocatalysts for photocatalytic nitrogen fixation.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A non-metallic B and F doped carbon nitride material, the preparation method of which comprises the following steps:

[0009] 1) Add boron trifluoride etherate dropwise into dichloromethane, then add melamine, and stir until the dichloromethane solvent is completely evaporated;

[0010] 2) The solid obtained in step 1) is calcined at high temperature and then ground to obtain B and F doped carbon nitride powder.

[0011] Furthermore, in the above-mentioned method for preparing a non-metallic B and F doped carbon nitride material, in step 1), the stirring is continuous stirring at room temperature for 5-8 hours.

[0012] Furthermore, in the above-mentioned method for preparing a non-metallic B and F doped carbon nitride material, in step 1), the molar ratio of boron trifluoride etherate to melamine is (1, 3, 5, 7, 9, 11, 13):100.

[0013] Furthermore, in the above-mentioned method for preparing a non-metallic B and F doped carbon nitride material, in step 2), the calcination temperature is 550° C., the holding time is 5 h, and the heating rate is 5° C. / min.

[0014] Application of any of the above-mentioned non-metallic B and F-doped carbon nitride materials in photocatalytic nitrogen fixation.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention combines melamine with boron trifluoride etherate by calcination to obtain a non-metallic B and F doped carbon nitride photocatalyst, and uses the catalyst for photocatalytic nitrogen fixation to synthesize ammonia, thereby greatly improving the separation efficiency of photogenerated electrons and holes, enhancing the light absorption capacity, and enhancing the photocatalytic performance.

[0017] 2. The method for preparing non-metallic B and F doped carbon nitride of the present invention has simple operation steps, mild reaction conditions, and is environmentally friendly, which is conducive to large-scale promotion and use.

[0018] 3. The non-metallic B and F doped carbon nitride prepared by the present invention has low cost and stable properties.

[0019] 4. The non-metallic B and F-doped carbon nitride photocatalyst prepared by the present invention has high catalytic activity for synthesizing ammonia, and the maximum ammonia yield can reach 466.92 μmol·L -1 , which has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flow chart of preparing non-metallic B and F doped carbon nitride material of the present invention.

[0021] Figure 2 The XRD diagrams of the non-metal B and F doped carbon nitrides obtained in Examples 1-7 of the present invention and the carbon nitride obtained in Example 8.

[0022] Figure 3 FTIR graphs of the non-metal B and F doped carbon nitrides obtained in Examples 1-7 of the present invention and the carbon nitride obtained in Example 8.

[0023] Figure 4 This is the XPS graph of the non-metal B and F doped carbon nitride obtained in Example 6 of the present invention and the carbon nitride obtained in Example 8.

[0024] Figure 5 It is a nitrogen fixation curve diagram of the non-metal B and F doped carbon nitride materials obtained in Examples 1-7 of the present invention and the carbon nitride material obtained in Example 8 under irradiation of a xenon lamp.

[0025] Figure 6 This is a diagram of the photocatalytic nitrogen fixation mechanism of the non-metallic B and F doped carbon nitride material prepared in the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with the embodiments so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0027] according to Figure 1 The flow chart shown is for preparing non-metallic B and F doped carbon nitride materials.

[0028] Example 1

[0029] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0030] 1) Add 210 μL of boron trifluoride ether to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0031] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1 The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (1% BF-CN).

[0032] Example 2

[0033] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0034] 1) Add 630 μL of boron trifluoride ether to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0035] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (3% BF-CN).

[0036] Example 3

[0037] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0038] 1) Add 1050 μL of boron trifluoride etherate to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0039] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1 The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (5% BF-CN).

[0040] Example 4

[0041] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0042] 1) Add 1470 μL of boron trifluoride ether to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0043] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1 The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (7% BF-CN).

[0044] Example 5

[0045] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0046] 1) Add 1890 μL of boron trifluoride ether to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0047] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1 The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (9% BF-CN).

[0048] Example 6

[0049] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0050] 1) Add 2310 μL of boron trifluoride ether to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0051] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1 The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (11% BF-CN).

[0052] Example 7

[0053] A method for preparing a non-metallic B and F doped carbon nitride material comprises the following steps:

[0054] 1) Add 2730 μL of boron trifluoride ether to 50 mL of dichloromethane, then add 10 g of melamine, and stir at room temperature for 5-8 hours until the dichloromethane solvent is completely evaporated;

[0055] 2) The white solid obtained in step 1) was placed in a muffle furnace and heated at 5°C·min -1 The temperature was raised to 550° C., calcined for 5 hours, cooled to room temperature and ground to obtain B and F doped carbon nitride powder (13% BF-CN).

[0056] Example 8

[0057] Carbon nitride is prepared by the following steps:

[0058] 1) Add 10 g of melamine to 50 mL of dichloromethane and stir at room temperature for 5-8 h until the dichloromethane solvent is completely evaporated. Put the obtained solid into a muffle furnace and heat it at 5 °C / min. -1 Raise the temperature to 550°C and calcine for 5 hours;

[0059] 2) Grind the yellow block solid obtained after cooling to room temperature to grind it into powder.

[0060] Examples 1-8 were characterized by using XRD and XPS to identify the product composition and crystal form.

[0061] Figure 2 The XRD diagrams of the non-metal B and F doped carbon nitrides obtained in Examples 1-7 and the carbon nitride obtained in Example 8 are shown.

[0062] Figure 3 FTIR graphs of the non-metal B and F doped carbon nitrides obtained in Examples 1-7 and the carbon nitride obtained in Example 8.

[0063] Figure 4The XPS graphs of the non-metallic B and F doped carbon nitride obtained in Example 6 and the carbon nitride obtained in Example 8 show that the B and F elements are successfully doped into the carbon nitride.

[0064] The photocatalytic nitrogen fixation test procedure is as follows: Photocatalytic nitrogen fixation is carried out in a photocatalytic reactor. 50 mg of non-metallic B and F doped carbon nitride catalyst is weighed and added to 100 mL of methanol aqueous solution (containing 5% methanol by volume), and ultrasonically dispersed for 15 minutes. In a dark environment, high-purity nitrogen is introduced for 30 minutes, and then the xenon light source is turned on. Samples are taken manually every 30 minutes, and the concentration of generated ammonia is tested by Nessler's reagent.

[0065] Figure 5 It is a nitrogen fixation curve diagram of the non-metal B and F doped carbon nitride materials obtained in Examples 1-7 and the carbon nitride material obtained in Example 8 under xenon lamp irradiation.

[0066] Figure 6 This is a diagram of the photocatalytic nitrogen fixation mechanism of the non-metallic B and F doped carbon nitride material prepared in the present invention.

[0067] The results show that the present invention successfully prepared non-metallic B and F doped carbon nitride photocatalysts by using boron trifluoride etherate, and the material has excellent photocatalytic nitrogen fixation performance. Under full spectrum irradiation, the photocatalytic nitrogen fixation efficiency can reach 186.77μmol·L -1 ·h -1 The non-metallic B-doped and F-doped carbon nitride materials prepared by the present invention have great development and application prospects in the photocatalytic green synthesis of ammonia.

Claims

1. A non-metallic B and F doped carbon nitride material, characterized in that: The preparation method thereof comprises the following steps: 1) Add boron trifluoride etherate dropwise into dichloromethane, then add melamine, and stir until the dichloromethane solvent is completely evaporated; 2) The solid obtained in step 1) is calcined at high temperature and then ground to obtain B and F doped carbon nitride powder.

2. A non-metallic B and F doped carbon nitride material according to claim 1, characterized in that: In step 1), the stirring is continuous stirring at room temperature for 5-8 hours.

3. The non-metallic B and F doped carbon nitride material according to claim 1, characterized in that: In step 1), the molar ratio of boron trifluoride etherate to melamine is (1, 3, 5, 7, 9, 11, 13):

100.

4. The non-metallic B and F doped carbon nitride material according to claim 1, characterized in that: In step 2), the calcination temperature is 550°C, the holding time is 5h, and the heating rate is 5°C / min.

5. Use of the non-metallic B and F doped carbon nitride material according to any one of claims 1 to 4 in photocatalytic nitrogen fixation.

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