A three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst and its preparation method

Abstract

The present invention relates to the technical field of inorganic photocatalysis, and specifically discloses a three-dimensional maple leaf micro-nano flower Cd<subgt;0.8< / subgt;Zn<subgt;0.2< / subgt;S photocatalyst and a preparation method thereof. The preparation method includes the following steps: Step 1: Take Cd(NO<subgt;3< / subgt;)<subgt;2< / subgt>·4H<subgt;2O, Zn(NO<subgt;3< / subgt;)<subgt;2·6H<subgt;2O, and H<subgt;2NCSNH<subgt;2 and mix them to obtain a mixed solution; Step 2: Add an ethylenediamine aqueous solution to the mixed solution and stir to obtain a suspension; and the ethylenediamine aqueous solution is obtained by mixing ethylenediamine and water in a volume ratio of 2:(1-4); Step 3: Pour the suspension into the inner lining of a reaction kettle, stir, and carry out hydrothermal reaction at 160-200 °C for 6-24 h; Step 4: After cooling to room temperature, centrifuge and wash with absolute ethanol and distilled water respectively for multiple times, and then dry overnight in vacuum to obtain the Cd<subgt;0.8< / subgt;Zn<subgt;0.2S photocatalyst. The three-dimensional maple leaf micro-nano flower Cd<subgt;0.8< / subgt;Zn<subgt;0.2S photocatalyst prepared by the preparation method in the present invention can effectively improve the photocatalytic effect for the problem that most semiconductor catalysts have a relatively wide energy band and are difficult to effectively absorb visible light.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic photocatalysis, and particularly relates to a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst and a preparation method thereof. Background Art

[0002] Ammonia plays an indispensable role in crop fertilizers, textile leather, and green energy hydrogen storage. Especially in the current situation where the world may face a second food crisis, ammonia plays a very important role in increasing the yield of food crops. For more than a hundred years, the artificial synthesis of ammonia by humans has mainly relied on the Haber process. The traditional ammonia production reaction is a reversible reaction of nitrogen and hydrogen under the action of a catalyst at high temperature (500 - 600 °C) and high pressure (20 - 50 MPa). This reaction not only consumes a large amount of fossil fuels but also releases a large amount of greenhouse gases, and the reaction efficiency is extremely low. Therefore, there is an urgent need for an environmentally friendly method for artificial ammonia synthesis. Photocatalytic nitrogen fixation technology uses a green, efficient, and environmentally friendly semiconductor material as the catalytic reaction medium, water and nitrogen as reactants, and solar energy as the driving energy, which is an economically friendly, safe, and environmentally friendly technology.

[0003] However, most of the semiconductor catalysts currently used have a relatively wide band gap and are difficult to effectively absorb visible light, and the photocatalytic effect needs to be improved. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst and a preparation method thereof.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions to achieve:

[0006] A preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, comprising the following steps:

[0007] Step 1: Take 3 - 6 mmol of Cd(NO3)2•4H2O, 1 - 2 mmol of Zn(NO3)2•6H2O, and 5 - 10 mmol of H2NCSNH2 and mix them to obtain a mixed solution;

[0008] Step 2: Add 50 - 70 mL of an ethylenediamine aqueous solution to the mixed solution and stir for 45 - 90 min to obtain a suspension; and the ethylenediamine aqueous solution is obtained by mixing ethylenediamine and water with a volume ratio of 2:(1 - 4).

[0009] Step 3: Pour the suspension into the inner lining of the reactor and stir for 0.5 - 2 h, then carry out hydrothermal reaction at 160 - 200 °C for 6 - 24 h;

[0010] Step 4: After cooling to room temperature, centrifuge and wash with absolute ethanol and distilled water respectively for multiple times, and then dry overnight under vacuum to obtain the Cd 0.8 Zn 0.2 S photocatalyst.

[0011] Further, in Step 2, the suspension is stirred under the cooperation of a magnetic rotor and a magnetic stirring table, and the rotational speed of the magnetic stirring table is 500 - 800 r / min.

[0012] Further, in Step 3, the hydrothermal reaction temperature is 160 - 200 °C.

[0013] Further, in Step 3, the hydrothermal reaction time is 6 - 24 h.

[0014] Further, in Step 3, the inner lining of the reactor is a polytetrafluoroethylene inner lining.

[0015] Further, in Step 4, the number of times of centrifugal washing with absolute ethanol and distilled water respectively is 2 - 3 times.

[0016] Further, in Step 4, the temperature of vacuum overnight drying is 60 - 80 °C.

[0017] A three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst prepared by the above preparation method, and the Cd 0.8 Zn 0.2 S photocatalyst is in the shape of a three-dimensional maple leaf micro-nano flower.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] The present invention successfully prepares the Cd 0.8 Zn 0.2 S photocatalyst by changing the molar ratio of Cd(NO3)2•4H2O to Zn(NO3)2•6H2O. Specifically, the present invention changes the microscopic morphology of the photocatalyst, increases its specific surface area, and regulates its corresponding band gap through the cooperation of appropriate molar components of raw materials (3:1). The change in specific surface area can increase the contact area between the catalyst and nitrogen, which is beneficial to the subsequent activation and dissociation of nitrogen. And the appropriate regulation of the band gap plays an indispensable role in the migration and recombination rate of photo-generated carriers and the redox ability in the photocatalytic nitrogen fixation reaction.

[0020] The Cd 0.8 Zn 0.2The S photocatalyst has good light absorption in the visible light region and has very potential applications in photocatalytic organic degradation, photocatalytic hydrogen production, and other optoelectronic fields. Cd 0.8 Zn 0.2 The appropriate conduction band and valence band positions of S can promote the progress of the photocatalytic nitrogen fixation reaction; ethylenediamine can enhance the diffraction peaks and promote the crystallization and accelerate the sulfidation process during the synthesis of sulfides. Therefore, due to the above advantages, the three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst prepared by ethylenediamine and water in a certain solvent ratio through the hydrothermal method can find some applications in the field of ammonia production.

[0021] In the present invention, the preparation method uses ethylenediamine and water as raw materials to prepare the Cd 0.8 Zn 0.2 S photocatalyst with strong stability and high photocatalytic nitrogen fixation activity. Under the irradiation of a simulated solar xenon lamp, the ammonia production concentration of 50 mg of the catalyst in a 1 mmol / L methanol hole sacrificial agent solution under light for 2 h is 139.137 μmol / L, and the ammonia production rate can reach 69.5685 μmol / L / h.

[0022] In addition, the catalyst in the present invention has the advantages of high purity, simple synthesis, low cost, etc., and the synthesized photocatalyst has the advantages of controllable morphology and stable crystal size. Using thiourea as the sulfur source has a relatively high safety factor. Therefore, the product prepared by the present invention can be widely applied in the field of photocatalytic nitrogen fixation.

[0023] In summary, the three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst prepared by the preparation method in the present invention can effectively improve the photocatalytic effect for the problem that most semiconductor catalysts have a wide band gap and are difficult to effectively absorb visible light. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the X-ray diffraction (XRD) pattern of the Cd 0.8 Zn 0.2 S photocatalyst in Example 1 of the present invention;

[0025] Figure 2 It is the scanning electron microscope (SEM) image of the Cd 0.8 Zn 0.2 S photocatalyst in Example 1 of the present invention;

[0026] Figure 3 It is the enlarged view of the scanning electron microscope (SEM) image of the Cd 0.8 Zn 0.2 S photocatalyst in Example 1 of the present invention;

[0027] Figure 4 In Example 1 of the present invention, Cd 0.8 Zn 0.2 Chromatograms (ion chromatograph) of the S photocatalyst at standard NH4 solution concentrations of 25 μmol / L, 50 μmol / L, 100 μmol / L, 200 μmol / L, and 400 μmol / L; +

[0028] Figure 5 In Example 1 of the present invention, Cd 0.8 Zn 0.2 Standard curve fitted by the S photocatalyst;

[0029] Figure 6 In Examples 1, 2, and 3 of the present invention, Cd 0.8 Zn 0.2 Chromatograms of the S photocatalyst after the photocatalytic reaction for pure Cd 0.8 Zn 0.2 S;

[0030] Figure 7 In Examples 1, 2, and 3 of the present invention, Cd 0.8 Zn 0.2 Enlarged chromatogram of the S photocatalyst in the chromatograph at 3.7 - 4.2 min after the photocatalytic reaction. Detailed implementation manners

[0031] The following further elaborates and explains the specific content of the present invention in conjunction with examples.

[0032] Examples

[0033] Example 1

[0034] A preparation method of a three - dimensional maple leaf micro - nano flower Cd 0.8 Zn 0.2 S photocatalyst, comprising the following steps:

[0035] Step 1: Weigh 3 mmol of Cd(NO3)2·4H2O, 1 mmol of Zn(NO3)2·6H2O, and 5 mmol of H2NCSNH2 into a beaker with a magnetic rotor;

[0036] Step 2: Take 25 mL of ethylenediamine and 25 mL of distilled water to obtain an ethylenediamine aqueous solution, add the ethylenediamine aqueous solution to the beaker in Step 1, and place it on a magnetic stirring table with a rotation speed of 600 r / min and stir for 45 min to obtain a suspension;

[0037] Step 3: Pour the suspension in the beaker in Step 2 into a 100 - mL polytetrafluoroethylene liner, stir for 1 h, and then carry out a hydrothermal reaction at 180 °C for 12 h; ​

[0038] Step 4: After cooling to room temperature, the product in Step 3 is centrifugally washed three times with absolute ethanol and distilled water respectively, and then placed in a vacuum drying oven for overnight drying at 60 °C to obtain maple leaf-shaped Cd 0.8 Zn 0.2 S photocatalyst.

[0039] Example 2

[0040] A preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, comprising the following steps:

[0041] Step 1: Weigh 4.5 mmol of Cd(NO3)2·4H2O, 1.5 mmol of Zn(NO3)2·6H2O, and 7.5 mmol of H2NCSNH2 into a beaker with a magnetic rotor;

[0042] Step 2: Take 40 mL of ethylenediamine and 20 mL of distilled water to obtain an ethylenediamine aqueous solution. Add the ethylenediamine aqueous solution to the beaker in Step 1, and place it on a magnetic stirring table with a rotation speed of 500 r / min and stir for 60 min to obtain a suspension;

[0043] Step 3: Pour the suspension in the beaker in Step 2 into a 100 mL polytetrafluoroethylene inner liner, stir for 0.5 h, and then carry out a hydrothermal reaction at 160 °C for 24 h;

[0044] Step 4: After cooling to room temperature, the product in Step 3 is centrifugally washed twice with absolute ethanol and distilled water respectively, and then placed in a vacuum drying oven for overnight drying at 70 °C to obtain maple leaf-shaped Cd 0.8 Zn 0.2 S photocatalyst.

[0045] Example 3

[0046] A preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, comprising the following steps:

[0047] Step 1: Weigh 6 mmol of Cd(NO3)2·4H2O, 2 mmol of Zn(NO3)2·6H2O, and 10 mmol of H2NCSNH2 into a beaker with a magnetic rotor;

[0048] Step 2: Take 23 mL of ethylenediamine and 47 mL of distilled water to obtain an ethylenediamine aqueous solution. Add the ethylenediamine aqueous solution to the beaker in Step 1, and place it on a magnetic stirring table with a rotation speed of 800 r / min and stir for 90 min to obtain a suspension;

[0049] Step 3: Pour the suspension in the beaker from Step 2 into a 100 mL polytetrafluoroethylene liner, stir for 2 h, and then carry out a hydrothermal reaction at 200 °C for 6 h;

[0050] Step 4: After cooling to room temperature, centrifuge and wash the product from Step 3 three times with absolute ethanol and distilled water respectively, and then place it in a vacuum drying oven for overnight drying at 80 °C to obtain maple leaf-shaped Cd 0.8 Zn 0.2 S photocatalyst.

[0051] Referring to Figure 1 , for the photocatalyst prepared in Example 1 of the present invention, obvious diffraction peaks appeared at 24.835°, 26.526°, 28.203°, 36.648, 43.737°, 47.869°, 51.871°, and 52.852°. These correspond to the (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0), (1 0 3), (1 1 2), and (2 0 1) crystal planes of Cd0.8Zn0.2S in PDF#49-1302. Moreover, the diffraction peaks are sharp and there are no other miscellaneous peaks, which proves that the method of the present invention can successfully prepare Cd 0.8 Zn 0.2 S photocatalyst.

[0052] Combined with Figure 2 and Figure 3 , it can be seen that: the Cd 0.8 Zn 0.2 S prepared by the method of the present invention presents a micro-nano maple leaf flower three-dimensional stacking structure, with uniform composition, a relatively large specific surface catalytic activity area, which increases the contact area between the catalyst and nitrogen, and is beneficial to the subsequent activation and dissociation of nitrogen.

[0053] Referring to Figure 4 , according to the chromatogram of the Cd 0.8 Zn 0.2 S photocatalyst of the present invention at different standard concentrations, it can be seen that the peak time of ammonium ion is about 4.27 min, and its peak area will linearly increase correspondingly with the increase of concentration.

[0054] Referring to Figure 5 , it can be seen from the standard curve fitted with the Cd 0.8 Zn 0.2 S photocatalyst that: the Cd 0.8 Zn 0.2 S photocatalyst prepared by the present invention has a relatively high correlation coefficient. Combined with Figure 4 , the ammonia production of the sample can be accurately determined according to the peak area of ammonium ion at about 4.27 min of the test sample by using its standard curve.

[0055] Referring to Figure 6 , it can be seen that for the Cd 0.8 Zn 0.2 S prepared in each embodiment of the present invention, the peak time of the ion chromatography injection after the photocatalytic reaction is about 4.2 min, further indicating that Cd 0.8 Zn 0.2 S has the performance of nitrogen fixation and ammonia production.

[0056] Referring to Figure 7 , it can be seen that in each embodiment of the present invention, the ammonia production amount of the Cd 0.8 Zn 0.2 S photocatalyst in Example 1 is the largest, and the ammonia production amount is 139.137 μmol / L.

Claims

1. A preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, characterized in that, Including the following steps: Step 1: Take 3 - 6 mmol of Cd(NO3)2·4H2O, 1 - 2 mmol of Zn(NO3)2·6H2O, and 5 - 10 mmol of H2NCSNH2 and mix them to obtain a mixed solution; Step 2: Add 50 mL - 70 mL of ethylenediamine aqueous solution to the mixed solution and stir for 45 - 90 min to obtain a suspension; and the ethylenediamine aqueous solution is obtained by mixing ethylenediamine and water with a volume ratio of 2:(1 - 4); Step 3: Pour the suspension into the inner lining of the reaction kettle, stir for 0.5 h - 2 h, and then carry out hydrothermal reaction at 160 - 200 °C for 6 - 24 h; Step 4: After cooling to room temperature, centrifuge and wash with absolute ethanol and distilled water for multiple times respectively, and then dry overnight under vacuum to obtain the Cd 0.8 Zn 0.2 S photocatalyst.

2. The preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, characterized in that In Step 2, the suspension is stirred under the cooperation of a magnetic rotor and a magnetic stirring table, and the rotational speed of the magnetic stirring table is 500 - 800 r / min.

3. A preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, characterized in that, In Step 3, the inner lining of the reaction kettle is a polytetrafluoroethylene inner lining.

4. The preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, characterized in that In Step 4, the number of times of centrifugal washing with absolute ethanol and distilled water is 2 - 3 times.

5. A preparation method of a three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst, characterized in that In Step 4, the temperature of vacuum overnight drying is 60 - 80 °C.

6. A three-dimensional maple leaf micro-nano flower Cd 0.8 Zn 0.2 S photocatalyst prepared by the preparation method according to any one of claims 1-5, characterized in that: The Cd 0.8 Zn 0.2 S photocatalyst is in the shape of three-dimensional maple leaf micro-nano flowers.

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