Preparation method of nano porous carbon loaded Fe-O single cluster electrocatalyst

Abstract

The invention provides a preparation method of a nano porous carbon loaded Fe-O single cluster electrocatalyst, which comprises the following steps: mixing and stirring catechol, formaldehyde, sodium carbonate and water to a clear solution state, and aging the obtained solution in a drying oven until the solution forms solid gel; the solid gel and a polyether solution are mixed, soaked and stirred, and the soaked gel is placed in a drying oven to be dried; roasting the dried gel in a nitrogen atmosphere, and then roasting in a carbon dioxide atmosphere; carrying out ball milling on the calcined sample to obtain nano-porous carbon powder; ca-L-Fe28 is dissolved in water, then a proper amount of calcined sample powder is added into the water, then the solution is centrifuged and dried, and the composite nano-porous carbon loaded Fe-O single cluster electrocatalyst is obtained. The prepared catalyst has a good dispersion effect and good oxidation-reduction performance, urea can be synthesized under low-energy-consumption and mild conditions, and the synthesis method of the electrocatalyst is simple in process and suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and relates to a preparation method of an electrocatalyst based on Fe-O single clusters supported on nanoporous carbon. Background Art

[0002] Urea (CO(NH 2 ) 2 ) is one of the most widely produced organic chemicals in the world, with a market share of $75 billion. More than 90% of urea is used as a nitrogen-containing fertilizer (~46%) in agriculture, while the remaining urea can be used in synthetic resins, barbiturates, dermatological products, etc. Currently, the Bosch-Meiser process has been industrially established for artificial urea production, which is achieved by coupling CO 2 and NH 3 . Considering this fact, the urgency of developing another efficient and sustainable urea production route under mild conditions is highlighted. From multiple perspectives, electrochemical technology is an attractive alternative for future urea synthesis. Electrocatalytic nitrogen reduction reaction to produce ammonia from atmospheric nitrogen and water is an emerging technology. In this regard, nitrate (NO 3- ) is a very ideal nitrogen-containing reactant with a solid state. Given the large difference in bond energy between the N=O bond (204 kJmol -1 ) and the N≡N bond (941 kJmol -1 ), recently, the NO 3- reduction reaction has attracted the attention of chemists to circumvent the above problems. Coupling nitrate or nitrite with carbon dioxide may be another way to drive electrocatalytic urea synthesis. The key challenges include finding active sites for the previous C-N coupling to increase the selectivity of urea and suppressing the occurrence of the unwanted hydrogen evolution reaction (HER) to enhance the Faraday efficiency.

[0003] Carbon materials have important applications in the field of electrocatalysis. Due to their special electronic structure and chemical activity, carbon materials can act as catalysts or catalytic support materials in electrocatalytic reactions and play an important role.

[0004] Chinese Patent with Publication No. CN113546666A provides a preparation method of a porous material with an iron-nitrogen-carbon structure wrapping iron clusters. The specific process is as follows: Add potassium ferrate, melamine, and soluble starch to high-purity water, continuously stir and mix evenly, then dry and grind to obtain a sample; Heat the obtained sample to 550 °C under argon protection and hold for 1.5 h for pre-carbonization, then continue to heat to 850 - 1100 °C and hold for 2 h for secondary carbonization, and then naturally cool to room temperature to obtain a black powdery porous material with an iron-nitrogen-carbon structure wrapping iron clusters.

[0005] The Chinese patent with the publication number CN118287122A provides a preparation method and an application method for a multi - pore nitrogen - doped carbon - supported iron oxide cluster and iron single - atom catalyst, including the following steps: S1. Prepare an iron - based metal - organic framework, and calcine the iron - based metal - organic framework at high temperature in a nitrogen or argon atmosphere to obtain a carbonized iron - based metal - organic framework; S2. Add 50 mg of the carbonized iron - based metal - organic framework to 100 mL of an acid solution, stir magnetically at room temperature, and remove unstable iron species by pickling; S3. Repeatedly leach the pickled carbonized iron - based metal - organic framework with distilled water, wash it to neutrality, and then put it into a vacuum drying oven to dry; S4. Grind the powder obtained in step S3 with an agate mortar to obtain a multi - pore nitrogen - doped carbon - supported iron oxide cluster and iron single - atom catalyst.

[0006] The catalyst provided by this invention patent application has differences in both the preparation process and the application field compared with the above - mentioned patent literature. Summary of the Invention

[0007] The present invention provides a preparation method for a nano - porous carbon - supported Fe - O single - cluster electrocatalyst. This catalyst has good electrochemical performance. Combining with the iron - oxygen single - cluster Ca - L - Fe 28 a Ca - L - Fe 28 @nano - porous carbon single - cluster catalyst was synthesized.

[0008] The present invention adopts the following technical solutions to achieve the above - mentioned purpose:

[0009] A preparation method for a nano - porous carbon - supported Fe - O single - cluster electrocatalyst, the steps of which are as follows:

[0010] (1) Mix catechol or bisphenol A, formaldehyde, sodium carbonate and water and stir until it becomes a clear solution state. Place the obtained solution in an oven for aging until a solid gel is formed;

[0011] (2) Prepare a polyether solution. Divide the solid gel obtained in step (1) into small pieces of 3 - 4 cm, mix and soak them with the polyether solution, stir, and then place the soaked gel in an oven to dry;

[0012] (3) Calcine the dried gel in a nitrogen atmosphere, and then calcine it in a carbon dioxide atmosphere;

[0013] (4) Ball - mill the calcined sample to obtain nano - porous carbon powder; Dissolve Ca - L - Fe 28 in water, then add an appropriate amount of the calcined sample powder to the water, stir for 12 hours, let it stand for 12 hours, and then centrifuge, dry, to obtain a composite nano - porous carbon - supported Fe - O single - cluster electrocatalyst.

[0014] Moreover, in step (1), the weight ratio of catechol, formaldehyde, sodium carbonate and water is 50 - 60:70 - 80:1:130 - 150.

[0015] Moreover, in step (1), the weight ratio of bisphenol A, formaldehyde, sodium carbonate and water is 100 - 120:70 - 80:1:130 - 150.

[0016] Moreover, in step (1), the stirring time is 1 hour.

[0017] Moreover, in step (2), the mass fraction of the polyether is 1%, and the mass ratio to the solid gel feed is 2:1.

[0018] Moreover, in step (2), the drying time is 72 hours and the temperature is 50 °C.

[0019] Moreover, in step (3), the nitrogen calcination time is 1 hour and the temperature is 600 °C; the carbon dioxide calcination time is 1 hour and the temperature is 950 °C.

[0020] Moreover, the heating rate of the nitrogen calcination is 5 °C / min; the heating rate of the carbon dioxide calcination is 5 °C / min.

[0021] Moreover, in step (4), the mass ratio of the Fe - O single cluster, the powder of the nanoporous carbon, and water is 1:5:500.

[0022] Moreover, in step (4), the ball - milling time is 3 hours and the drying temperature is 90 °C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention prepares catechol / bisphenol A nanoporous carbon at low cost, loads iron - oxygen single clusters, has a good dispersion effect, and can be prepared in batches. It has good redox performance, can synthesize urea under low - energy - consumption and mild conditions, and the electrocatalyst synthesis method of the present invention has the characteristics of simple process and low cost, and is suitable for large - scale production. Description of the Drawings

[0025] Figure 1 is the XRD pattern of the catechol / bisphenol A - derived carbon and Ca - L - Fe 28 @C involved in the present invention;

[0026] Figure 2 is the electron microscopy characterization diagram of the electrocatalyst of the nanoporous carbon loaded with Fe - O single clusters provided by the present invention;

[0027] Figure 3 is the batch product diagram of the electrocatalyst of the nanoporous carbon loaded with Fe - O single clusters in the present invention;

[0028] Figure 4 is the graph of urea production and Faraday efficiency of the Fe-O single cluster electrocatalyst supported on nanoporous carbon provided by the present invention in 0.1 M KNO 3 electrolyte; Detailed implementation manners

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0030] Example 1

[0031] Steps for a preparation method of an Fe-O single cluster (Ca-L-Fe 28 ) electrocatalyst supported on nanoporous carbon:

[0032] (1) Mix 24.86 g of catechol (51.53 g of bisphenol A), 35.1 g of formaldehyde, 0.047 g of sodium carbonate with 67.5 g of water and stir until it becomes a clear solution state. Place the obtained solution in an oven for aging, at 30 °C for one day and at 90 °C for two days.

[0033] (2) Prepare a 1% polyether solution, divide the solid gel obtained in step (1) into small pieces of 3 - 4 cm, mix and soak them according to the mass ratio of gel to 1% polyether solution of 1:2, stir gently for 5 to 6 hours, and repeat twice.

[0034] (3) Pour out the solvent from the soaked gel, and place it in an oven to dry within the range of 50 °C for 72 hours;

[0035] (4) Calcine the dried sample in a nitrogen atmosphere at 600 °C for 1 hour with a heating rate of 5 °C / min; further calcine the calcined sample in a carbon dioxide atmosphere at 950 °C for two hours with a heating rate of 5 °C / min.

[0036] (5) Ball-mill the calcined sample to obtain a black powder of nanoporous carbon; dissolve 10 mg of Fe-O single cluster in 50 ml of water, ultrasonicate for 10 min, then add 50 mg of nanoporous carbon powder to the water, stir for 12 hours, let it stand for 12 hours, then centrifuge and place it in a vacuum drying oven at 90 °C to dry to obtain 40 mg of the composite catalyst (it can be prepared in batches). See Figures 1 to 3 ( Figure 1 is the XRD pattern of the material. As shown in the figure, only the diffraction peaks of the carbon material appear in the composite material, proving that there is no accumulation of the material on the carbon carrier and it is evenly dispersed; Figure 2 is the electron microscope image of the composite material, which can further illustrate the even dispersion of the material; Figure 3 is the batch preparation diagram of the material, proving that this catalytic material can be prepared on a large scale).

[0037] (6) The test uses a three - electrode system. The carbon paper is clamped by the electrode clip as the working electrode, the silver / silver chloride electrode as the reference electrode, and the platinum sheet as the counter electrode. 0.1 M KNO 3 The electrolyte is measured for its catalytic activity under a sufficient supply of CO 2 . The applied voltage is - 1.3 V and the test duration is 2 hours. The test results Figure 4 are shown as follows. The urea production can reach 13.2 mmol / h / g cat , and the Faraday efficiency is 26%.

[0038] The above - mentioned embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited to the above - mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a nanoporous carbon-supported Fe-O single cluster electrocatalyst, characterized in that: The steps are: (1) mixing catechol or bisphenol A, formaldehyde, sodium carbonate and water and stirring until a clear solution is obtained, and aging the obtained solution in an oven until the solution forms a solid gel; (2) preparing a polyether solution, dividing the solid gel obtained in step (1) into small pieces of 3-4 cm, mixing and soaking the solid gel in the polyether solution, stirring, and placing the soaked gel in an oven to dry; (3) calcining the dried gel in a nitrogen atmosphere and then calcining it in a carbon dioxide atmosphere; (4) ball-milling the calcined sample to obtain nanoporous carbon powder; dissolving the Fe-O single cluster in water, then adding an appropriate amount of the calcined sample powder into the water, stirring and standing, then centrifuging the solution and drying to obtain a composite nanoporous carbon-loaded Fe-O single cluster electrocatalyst.

2. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (1), the weight ratio of catechol, formaldehyde, sodium carbonate and water is 50-60:70-80:1:130-150.

3. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (1), the weight ratio of bisphenol A, formaldehyde, sodium carbonate and water is 100-120:70-80:1:130-150.

4. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (1), the stirring time is 1 hour.

5. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (2), the mass fraction of the polyether is 1%, and the mass ratio of the polyether to the solid gel is 2:

1.

6. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (2), the drying time is 72 hours and the temperature is 50°C.

7. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (3), the nitrogen calcination time is 1 hour at a temperature of 600°C; the carbon dioxide calcination time is 1 hour at a temperature of 950°C.

8. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (4), the mass ratio of the Fe-O single cluster, the nanoporous carbon powder and water is 1:5:

500.

9. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 1, characterized in that: In step (4), the ball milling time is 3 hours and the drying temperature is 90°C.

10. The method for preparing the nanoporous carbon supported Fe-O single cluster electrocatalyst according to claim 7, characterized in that: The nitrogen calcination heating rate is 5°C / min; the carbon dioxide calcination heating rate is 5°C / min.

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