Electrode material for preparing ammonia through electro-catalysis nitrogen reduction, preparation method and application of electrode material

Abstract

The invention belongs to the technical field of electro-catalysis materials, and particularly relates to an electro-catalysis nitrogen reduction ammonia production electrode material, a preparation method and application thereof. The chemical formula of the electrocatalytic nitrogen reduction ammonia production electrode material is Sr < 0.3 > Co < 0.7 > Fe < 2 > O < 4 >; the preparation method of the electrocatalytic nitrogen reduction ammonia electrode material comprises the following steps: S1, dissolving ferric salt and cobalt salt in water, and uniformly stirring to obtain a pre-solution; s2, adding a Sr (OH) 2 solution into the pre-solution to adjust the pH value of the pre-solution, uniformly stirring to obtain a mixed solution, standing and aging for 1-5 hours, centrifuging, and collecting to obtain a precipitate; and S3, calcining the precipitate in an argon atmosphere, and grinding after calcining to obtain the electrode material for preparing ammonia through electro-catalysis nitrogen reduction. According to the present invention, with the large lattice spacing, the electron distribution between the material atoms can be regulated and controlled, the catalyst activity can be completely activated, the nitrogen can be effectively adsorbed by the twisted lattice structure, and the high ammonia yield and the high Faraday efficiency can be achieved under the low voltage;

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic materials, and in particular relates to an electrode material for electrocatalytic nitrogen reduction to produce ammonia, a preparation method and application thereof. Background Art

[0002] As one of the most important chemical raw materials, NH3 plays an extraordinary and important role in human society and industrial development. At present, the large-scale production of NH3 relies on the Haber-Bosch process (150-350atm, 350-550℃), but the Haber-Bosch industrial ammonia production has serious defects, such as high energy consumption, poor efficiency, and environmental pollution. The energy used for agricultural production and industrial applications each year accounts for 1% of the world's total energy supply and 3-5% of the total natural gas production. Therefore, the development of stable, green and efficient alternative energy sources is of great practical significance. From this perspective, the use of electrical energy for electrocatalytic nitrogen reduction to produce ammonia will be the next generation of green and environmentally friendly sustainable ammonia production technology with great potential. However, the low solubility of N2 in water systems and the high bond energy of N≡N severely limit the activation and hydrogenation kinetic rates.

[0003] At present, in order to achieve more efficient and stable high-activity and high-selectivity electrocatalytic nitrogen reduction to ammonia electrode materials, researchers have developed many catalysts or catalytic electrodes, and related technologies have also been reported. Patent CN 109174122A controls the concentration of chloride salts, as well as the amount of KBr, surfactants and hydrochloric acid to regulate the morphology and composition of the catalyst, and prepares a long needle sea urchin-shaped PdCu I r nitrogen reduction electrocatalyst, which has a high active specific surface area and promotes nitrogen adsorption. However, the price of precious metal-based materials is expensive and the hydrogen evolution side reaction is serious, and the yield and efficiency are difficult to meet the requirements. Patent CN114457357 A obtains single-crystal ultra-thin FeMo3S4 nanosheets through an organic-hard template synthesis method. This electrocatalyst activates multiple active sites and effectively reduces the energy barrier in the nitrogen reduction process. Harsh control conditions are not conducive to sustainable development and difficult to mass produce, and the unstable catalyst structure easily leads to catalytic activity deactivation. It is still urgent to develop an electrocatalytic nitrogen reduction to ammonia electrode with simple process, low cost and large-scale production.

[0004] In summary, the problems existing in the prior art are:

[0005] (1) At present, catalysts are always based on precious metals, which are expensive, scarce in reserves, and accompanied by serious hydrogen evolution side reactions.

[0006] (2) Transition metal composite materials with complex components have complex processes, poor structural stability, and are difficult to produce in large quantities.

[0007] Difficulty in solving the above technical problems:

[0008] (1) When ammonia is produced on a large scale, the strong N≡N bond can only be broken under high temperature and high pressure. Therefore, large-scale ammonia production currently relies on the Haber-Bosch process, which has high energy consumption, strict equipment requirements, and emits a large amount of greenhouse gases.

[0009] (2) The solubility of nitrogen in water is extremely low, and the activity of the electrocatalyst is very high. Common catalyst synthesis methods, such as doping and substitution, are difficult to fully activate the catalyst activity and fully expose the active sites.

[0010] (3) In industrial applications, the cost, synthesis process, energy efficiency and stability of materials are crucial. However, most of the electrocatalytic nitrogen reduction electrodes reported so far are limited by the complex and strict synthesis process and the stability of the material structure during the reaction. Therefore, it is extremely important to find an efficient, simple and stable electrocatalytic nitrogen reduction electrode for ammonia production. Summary of the invention

[0011] In view of the deficiencies in the prior art, the present invention provides an electrode material for electrocatalytic nitrogen reduction to produce ammonia, a preparation method and application thereof.

[0012] The purpose of the present invention can be achieved through the following technical solutions:

[0013] An electrode material for electrocatalytic nitrogen reduction to produce ammonia, wherein the chemical formula of the electrode material for electrocatalytic nitrogen reduction to produce ammonia is Sr 0.3 Co 0.7 Fe2O4.

[0014] A method for preparing an electrode material for producing ammonia by electrocatalytic nitrogen reduction, the preparation method comprising:

[0015] S1, dissolving iron salt and cobalt salt in water, stirring evenly to obtain a pre-solution;

[0016] S2, adding Sr(OH)2 solution to the pre-solution to adjust the pH value of the pre-solution, and stirring to obtain a mixed solution, and then standing and aging for 1-5 hours, and then centrifuging to collect the precipitate;

[0017] S3. The precipitate is calcined in an argon atmosphere, and after calcination, it is ground to obtain an electrode material for electrocatalytic nitrogen reduction to produce ammonia.

[0018] Furthermore, the iron salt is at least one of ferric nitrate, ferric chloride and ferric sulfate.

[0019] Furthermore, the cobalt salt is at least one of cobalt nitrate, cobalt chloride and cobalt sulfate.

[0020] Furthermore, the molar ratio of the iron salt to the cobalt salt is 1:1.

[0021] Furthermore, the pH of the mixed solution obtained in step S2 is ≥12.

[0022] Furthermore, the calcination conditions are a temperature of 600-800° C. and a calcination time of 1-3 hours.

[0023] The invention discloses an application of an electrode material for producing ammonia by electrocatalytic nitrogen reduction.

[0024] Beneficial effects of the present invention:

[0025] 1. The electrocatalytic material used in the present invention can synthesize ammonia by electrocatalytic nitrogen reduction in a green, efficient and stable manner at room temperature and pressure.

[0026] 2. The present invention has a larger lattice spacing that can regulate the electron distribution between material atoms and fully activate the catalyst activity. The distorted lattice structure can effectively adsorb nitrogen and achieve high ammonia yield and high Faraday efficiency at a lower voltage.

[0027] 3. The present invention uses transition metal-based catalysts, avoiding expensive precious metal-based materials, and utilizing the most common and extremely cheap spinel material as the main body. The material structure is stable and has great advantages in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 The Sr provided in the embodiment of the present invention 0.3 Co 0.7 Synthesis flow chart of Fe2O4 electrode material for electrocatalytic nitrogen reduction to produce ammonia.

[0030] Figure 2 This is a flow chart of the synthesis of CoFe2O4 electrocatalytic nitrogen reduction electrode materials for producing ammonia provided as a comparative example of the present invention.

[0031] Figure 3 Sr 0.3 Co 0.7 SEM image (a) and TEM image (b) of Fe2O4 electrode material for electrocatalytic nitrogen reduction to produce ammonia.

[0032] Figure 4 SEM image (a) and TEM image (b) of CoFe2O4 electrocatalytic nitrogen reduction to produce ammonia electrode material.

[0033] Figure 5 For Sr0.3 Co 0.7 Nitrogen temperature-programmed desorption measurement diagram of Fe2O4 and CoFe2O4 electrode materials for electrocatalytic nitrogen reduction to produce ammonia.

[0034] Figure 6 The UV-visible absorption spectra of the electrolyte before and after electrolysis at open circuit voltage, and in nitrogen and argon atmospheres.

[0035] Figure 7 The Sr provided in the embodiment of the present invention 0.3 Co 0.7 Fe2O4 electrocatalytic nitrogen reduction to ammonia performance test diagram: LSV curve spectrum under different atmospheres (a), ammonia yield under different voltages (b), corresponding Faraday efficiency (c), cycle stability diagram (d).

[0036] Figure 8 At -0.3V vs.RHE 14 Electrolyte for electrolysis under N2 saturation conditions 1 H-NMR spectra and 15 Electrolyte for electrolysis under N2 saturation conditions 1 H-NMR spectrum.

[0037] Fig. 9 This is a performance comparison chart of all spinel catalysts reported at this stage in the electrocatalytic nitrogen reduction to ammonia production. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing an electrode material for producing ammonia by electrocatalytic nitrogen reduction, the preparation method comprising:

[0041] S1, 1 g of ferric chloride and 0.8 g of cobalt chloride were dissolved in 50 mL of deionized water and stirred to obtain a pre-solution;

[0042] S2. Add Sr(OH)2 solution to the pre-solution and stir to obtain a mixed solution. Adjust the pH of the mixed solution to ≥12, then allow to stand for aging for 2 hours, centrifuge, dry overnight at 80°C, and collect the precipitate.

[0043] S3, calcining the precipitate in an argon atmosphere at a temperature of 700°C for 2 hours, and grinding the precipitate to obtain an electrode material for electrocatalytic nitrogen reduction to produce ammonia; the chemical formula of the electrode material for electrocatalytic nitrogen reduction to produce ammonia is Sr 0.3 Co 0.7 Fe2O4; Sr 0.3 Co 0.7 The SEM and TEM images of Fe2O4 electrocatalytic nitrogen reduction to produce ammonia electrode materials are shown in Figure 3 shown.

[0044] Comparative Example 1

[0045] 1 g of ferric chloride and 0.8 g of cobalt chloride were dissolved in 50 mL of deionized water and stirred evenly; saturated Sr(OH)2 solution was then added until the pH was ≥ 12, and then aged for 2 hours; after aging, the mixture was centrifuged several times to wash away Sr 2+ , and dried at 80°C overnight; finally, calcined at 700°C in an argon atmosphere for 2 hours, and ground to obtain the final electrode material; the chemical formula of the electrode material at this time is CoFe2O4; the SEM and TEM images of the CoFe2O4 electrocatalytic nitrogen reduction to ammonia electrode material are shown in Figure 4 shown.

[0046] Electrocatalytic nitrogen reduction to ammonia was performed in a two-compartment electrolyzer separated by a Celgard membrane under ambient conditions. All potentials were converted to the potential of the reversible hydrogen electrode (RHE). Purified N2 was continuously fed into the cathode chamber to ensure that the entire cathode was surrounded by N2 bubbles. The gas flow rates of nitrogen and argon were 30 sccm. Product selectivity was carried out in N2-saturated 0.1 M HCl at ambient temperature and pressure. Constant potential tests were tested at different potentials, including -0.1 V, -0.2 V, -0.3 V, -0.4 V, and -0.5 V vs. RHE. After the electrocatalytic reduction reaction, the electrolyte was collected and analyzed by color development for quantitative determination. To prepare the working electrode, 5 mg of catalyst and 50 μL of Nafion solution (5 wt %) were dispersed in 950 μL of ethanol and a uniform slurry was formed by ultrasonic treatment for at least 1 h. Then, 20 μL of catalyst slurry was loaded into a 1×1 cm 2 The catalyst was deposited on carbon paper and dried under ambient conditions before use. Based on the total mass of the catalyst, a mass loading of 0.1 mg cm -2 .

[0047] Table 1 shows the catalytic performance of the catalysts reported at low voltages at this stage. 0.3 Co 0.7 Fe2O4 electrocatalytic nitrogen reduction to produce ammonia electrode material has good prospects for electrocatalytic nitrogen reduction at room temperature, atmospheric pressure and low voltage.

[0048] Table 1

[0049]

[0050]

[0051] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0052] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. An electrode material for electrocatalytic nitrogen reduction to produce ammonia, characterized in that: The chemical formula of the electrode material for electrocatalytic nitrogen reduction to produce ammonia is Sr 0.3 Co 0.7 Fe2O4.

2. A method for preparing an electrode material for electrocatalytic nitrogen reduction to produce ammonia, characterized in that: The preparation method comprises: S1, dissolving iron salt and cobalt salt in water, stirring evenly to obtain a pre-solution; S2, adding Sr(OH)2 solution to the pre-solution to adjust the pH value of the pre-solution, stirring evenly to obtain a mixed solution, and then standing and aging for 1-5 hours, and then centrifuging to collect the precipitate; S3. The precipitate is calcined in an argon atmosphere, and after calcination, it is ground to obtain an electrode material for electrocatalytic nitrogen reduction to produce ammonia.

3. The method for preparing an electrode material for electrocatalytic nitrogen reduction to produce ammonia according to claim 2, characterized in that: The iron salt is at least one of ferric nitrate, ferric chloride and ferric sulfate.

4. The method for preparing an electrode material for electrocatalytic nitrogen reduction to produce ammonia according to claim 2, characterized in that: The cobalt salt is at least one of cobalt nitrate, cobalt chloride and cobalt sulfate.

5. The method for preparing an electrode material for electrocatalytic nitrogen reduction to produce ammonia according to claim 2, characterized in that: The molar ratio of the iron salt to the cobalt salt is (1-3):

1.

6. The method for preparing an electrode material for electrocatalytic nitrogen reduction to produce ammonia according to claim 2, characterized in that: The pH of the mixed solution obtained in step S2 is ≥12.

7. The method for preparing an electrode material for electrocatalytic nitrogen reduction to produce ammonia according to claim 2, characterized in that: The calcination conditions are a temperature of 600-800° C. and a calcination time of 1-3 hours.

8. Use of the electrode material for electrocatalytic nitrogen reduction to produce ammonia as claimed in claim 1 in electrocatalytic nitrogen reduction to produce ammonia.

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