1. Fe₂/MoS₂An electrocatalyst, characterized by comprising a diatomic metallic iron source and MoS₂Said MoS₂Is a monolithic layer structure; the diatomic metallic iron source is anchored in the MoS₂The above.

2. An Fe according to claim 1₂/MoS₂The electrocatalyst is characterized in that the diatomic metallic iron source is Fe₂（CO）₉。

3. Fe as defined in any one of claims 1 to 2₂/MoS₂The preparation method of the electrocatalyst is characterized by comprising the following steps of:

the method comprises the following steps: weighing molybdic acid and thiourea, dissolving the molybdic acid and the thiourea in a solvent in sequence, fully stirring, and reacting for 15-20 hours at the temperature of 150-220 ℃ to obtain MoS₂Powder;

step two: the MoS prepared in the step one₂Immersing the powder into a mixture of water and isopropanol, and carrying out ultrasonic stripping; under the protection of inert gasPerforming lower crushing treatment, centrifuging the solution obtained after crushing treatment, and collecting supernatant; then, the collected supernatant is continuously centrifuged to obtain sediment MoS₂；

Step three: taking Fe₂（CO）₉Placing the mixture in a sulfuric acid solution, and carrying out ultrasonic treatment;

step four: centrifuging, washing and drying the solution in the third step, and collecting Fe₂（CO）₉；

Step five: collecting the collected Fe₂（CO）₉Adding into MoS₂Then adding methanol for hydrothermal reaction;

step six: centrifuging, washing and drying the solution obtained in the step five to obtain a metal Fe cluster anchored on MoS₂The electrocatalyst of (1).

4. An Fe according to claim 3₂/MoS₂The preparation method of the electrocatalyst is characterized in that in the first step, molybdic acid and thiourea are added according to the molar ratio of Mo to S of 1: 2-2.2.

5. An Fe according to claim 3₂/MoS₂The preparation method of the electrocatalyst is characterized in that in the second step, the volume ratio of water to isopropanol in ultrasonic stripping is 1: 4-5, the ultrasonic temperature is less than or equal to 30 ℃, and the centrifugal rotating speed is 6000-11000 r/min.

6. An Fe according to claim 3₂/MoS₂The preparation method of the electrocatalyst is characterized in that in the third step, the sulfuric acid with the concentration of 0.1-0.8 mol/L is placed in a sulfuric acid solution for 70-80 hours, and ultrasonic treatment is performed once every 3-4 hours, wherein each time lasts for 20-40 min.

7. An Fe according to claim 3₂/MoS₂The preparation method of the electrocatalyst is characterized in that in the fourth step, the centrifugal rotating speed is 3000-8000 r/min, washing is carried out for 10-20 times, and drying is carried out in a vacuum environment at 70-80 ℃.

8. An Fe according to claim 3₂/MoS₂The preparation method of the electrocatalyst is characterized in that in the fifth step, Fe₂（CO）₉Is in mass of Fe₂（CO）₉And MoS₂2-5% of the total mass, and the hydrothermal reaction is carried out for 70-80 h at a constant temperature of 60-70 ℃.

9. An Fe according to claim 3₂/MoS₂The preparation method of the electrocatalyst is characterized in that in the sixth step, the rotating speed is 6000-11000 r/min.

10. Use of an electrocatalyst according to claim 1 or 2 or obtained by a method according to any one of claims 3 to 9 in an industrial nitrogen reduction reaction.

Background

In agricultural production, nitrogen-rich soils are critical for high yield in the field, but the nitrogen reserves in the soil are quickly depleted at each harvest, and if nitrogen is not replenished, crop yield per year is reduced. Nitrogen is about 78% of the atmospheric volume, but it exists in the form of a gas that is chemically inert and useless to most plants. The ammonia synthesized by the Haber-Bosch method is widely applied to the production of synthetic nitrogen fertilizers, and the application of the ammonia is a necessary condition for continuously producing high-yield crops; typical yields of this industrial nitrogen reduction (NRR) are below 200mmol gcat^-1h^-1. This process is carried out at high temperatures of 400-. A more sustainable ammonia production process is water-based electrocatalysis at ambient conditionsNRR is used. However, these reaction rates and bias current densities are typically less than 10 mmol gcat, respectively^-1h^-1And 1 mA cm^-2. The N.ident.N bond cleavage of nitrogen requires 941 kJ/mol. From an energy perspective, nitrogen electrocatalytic reduction is very interesting as a promising low temperature ammonia synthesis tool.

In the prior art, the electrocatalytic reduction process for converting nitrogen into ammonia is usually carried out at a high temperature and a high pressure of 400-600 ℃, and the reaction process usually adopts noble metal catalysts such as Pt, Au and the like, so that the whole reaction process has harsh conditions, high cost and low yield; chinese patent publication No. CN107999114A, published 2018, 5-month 8, discloses a non-noble metal catalyst for preparing ammonia by electrochemically reducing nitrogen, wherein sulfides, phosphides, and nitrides of transition metal elements are directly contacted with an electrolyte aqueous solution, and a negative voltage is applied to the electrolyte aqueous solution, so as to realize the preparation of ammonia by electrochemically reducing nitrogen.

Disclosure of Invention

In order to solve the technical problems, the invention provides Fe for improving the catalytic activity of a catalyst₂/MoS₂An electrocatalyst, a preparation method and application; mixing MoS₂The stripping is of a single-layer structure, which is beneficial to nitrogen adsorption; fe is synthesized by hydrothermal synthesis method₂（CO）₉Anchored in MoS₂Preparation of diatomic dispersed Fe₂/ MoS₂A catalyst; the method has the characteristics of simple process, low energy consumption, mild conditions, good product appearance and the like, and is suitable for large-scale production and application.

The specific technical scheme of the invention is as follows: fe₂/MoS₂Electrocatalyst comprising diatomic metallic iron source and MoS₂Said diatomic metallic iron source anchored to the MoS₂The MoS₂Is a monolithic layer structure.

The invention prepares single-layer MoS by multiple times of ultrasonic₂More S vacancies are exposed, which is beneficial to bonding with Fe; the electrocatalyst is prepared from molybdic acid, thiourea and nonacarbonyl diiron by a hydrothermal method, and the Fe prepared by the method₂-MoS₂Catalyst, MoS₂The layer is a single-layer structureHas higher carrier density and higher mobility, MoS₂The gap level of the silicon is similar to that of typical silicon and has a nano-sheet structure, which is beneficial to nitrogen adsorption; the synergistic effect between the diatomic metallic iron source metal clusters is beneficial to improving the catalytic activity of single metal atoms.

Preferably, the diatomic metallic iron source is Fe₂（CO）₉。

The invention comprises the anchoring of the metal Fe cluster on MoS₂The preparation method of the electrocatalyst comprises the following steps:

the method comprises the following steps: weighing molybdic acid and thiourea, dissolving the molybdic acid and the thiourea in a solvent in sequence, fully stirring, and reacting for 15-20 hours at the temperature of 150-220 ℃ to obtain MoS₂Powder;

step two: the MoS prepared in the step one₂The powder was immersed in a mixture of water and isopropanol and subjected to ultrasonic exfoliation. Crushing under the protection of inert gas, centrifuging the solution obtained after crushing, and collecting supernatant; then, the collected supernatant is continuously centrifuged to obtain sediment MoS₂；

Step three: taking Fe₂（CO）₉Placing in sulfuric acid solution, and carrying out ultrasonic treatment.

Step four: centrifuging, washing and drying the solution in the third step, and collecting Fe₂（CO）₉。

Step five: collecting the collected Fe₂（CO）₉Adding into MoS₂Then, methanol is added for hydrothermal reaction.

Step six: centrifuging, washing and drying the solution obtained in the step five to obtain a metal Fe cluster anchored on MoS₂The electrocatalyst of (1).

The invention selects MoS₂Supported Fe₂The clusters act as catalysts for the nitrogen reduction reaction to produce ammonia. Fe₂/ MoS₂Has high catalytic activity on electrochemical NRR relative to MoS₂Single Fe atom of at least one in MoS₂In the vicinity of which Fe atoms (i.e., Fe)₂/MoS₂) Is favorable to N₂Is favorable for the effective activation of the N-N bond.

Preferably, in the first step, the addition sequence of molybdic acid and thiourea is not changed, and the addition amount is 1: 2-2.2 according to the molar ratio of Mo to S.

In the invention, molybdic acid and thiourea in the step one are used for synthesizing MoS₂The order of addition is not changed, otherwise MoS is affected₂Morphology; methanol acts as a solvent for dissolution.

Preferably, in the second step, the volume ratio of water to isopropanol in ultrasonic stripping is 1:4 to 5. The ultrasonic temperature is less than or equal to 30 ℃, and the centrifugal rotating speed is 6000-11000 r/min.

Ultrasonic stripping MoS in the second step of the invention₂Peeling off as a single layer structure to N₂Is promoted by adsorption of Fe₂（CO）₉And MoS₂Multiple times of ultrasonic treatment is needed during mixing, so that the anchoring of Fe to MoS is facilitated₂On the layer.

Preferably, in the third step, the concentration of the sulfuric acid is 0.1-0.8 mol/L and is used for dissolving Fe₂（CO）₉Of (1) is described.

Preferably, the centrifugal speed in the fourth step is 3000-8000 r/min.

Preferably, in the fifth step, Fe₂（CO）₉Is in mass of Fe₂（CO）₉And MoS₂2-5% of the total mass.

Preferably, the rotating speed in the sixth step is 6000 to 11000 r/min.

The invention comprises the application of the electrocatalyst or the electrocatalyst prepared by the preparation method in industrial nitrogen reduction reaction.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention adopts hydrothermal synthesis method to synthesize Fe₂（CO）₉Anchored in MoS₂Preparation of diatomic dispersed Fe₂/ MoS₂The catalyst has high catalytic activity on electrochemical NRR (non-catalytic reduction) compared with MoS₂Single Fe atom of at least one in MoS₂In the vicinity of which Fe atoms (i.e., Fe)₂/MoS₂) Is favorable to N₂The side adsorption of (2) is favorable for the effective activation of the N-N bond;

(2) diatomic dispersed Fe of the invention₂/ MoS₂The preparation method of the catalyst has the advantages of simple process and good product appearance, and the catalyst used for preparing ammonia by electrochemical reduction has the advantages of low energy consumption and mild conditions, and is suitable for large-scale production and application.

Drawings

FIG. 1 shows the anchoring of Fe clusters to MoS in the present invention₂Top electron micrograph;

FIG. 2 is a MoS without Fe loading after ultrasonic stripping in the present invention₂Electron micrographs of (A);

FIG. 3 is a MoS of the present invention without ultrasonic exfoliation₂Electron micrographs of (A);

FIG. 4 is a nitrogen reduction activity test chart of examples and comparative examples of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples. The devices, connections, and methods referred to in this disclosure are those known in the art, unless otherwise indicated.

Example 1

Fe₂/MoS₂An electrocatalyst and a method of making the same comprising the steps of:

the method comprises the following steps: weighing 9.0g of molybdic acid and 7.6g of thiourea, dissolving the molybdic acid and the thiourea in 30ml of water in sequence, fully stirring, and reacting for 18 hours at 160 ℃ to obtain MoS₂Powder;

step two: the MoS prepared in the step one₂The powder was immersed in a mixture of water and isopropyl alcohol at a volume ratio of 1:4 (total volume of water and isopropyl alcohol was 60 ml) and subjected to ultrasonic exfoliation. Crushing for 5 hours under the protection of nitrogen, centrifuging the solution obtained after crushing at the centrifugal rotation speed of 8000r/min, and collecting supernatant; then, the collected supernatant was centrifuged for 30 minutes to obtain MoS₂Precipitating;

step three: taking Fe₂（CO）₉Placing in 0.5mol/L sulfuric acid solution for 72h, and performing ultrasonic treatment once every 3 hours for 30min each time;

step four: centrifuging the solution of step three at 5000r/min, washing for 15 times, and cooling at 70 deg.CDrying in vacuum environment, and collecting Fe₂（CO）₉；

Step five: 3mg of the collected Fe was taken₂（CO）₉Adding to 97mg MoS₂Then adding 30ml of methanol solution, uniformly mixing, and standing for 72 hours in a constant temperature environment of 60 ℃;

step six: centrifuging the solution obtained in the step five at the centrifugal rotating speed of 8000r/min, washing and drying to obtain a metal Fe cluster anchored on MoS₂The electrocatalyst of (a);

and (3 mg) of the electrocatalyst obtained in the step six is added into a mixed solution consisting of 10ml of water and 30ml of ethanol to prepare a catalyst solution, and a proper amount of the catalyst solution is dropwise added onto 1cm by 1cm carbon paper to measure the reduction activity of the catalyst solution.

Example 2

An electrocatalyst with Fe clusters anchored on MoS2 and a preparation method thereof comprise the following steps:

the method comprises the following steps: weighing 9.0g of molybdic acid and 8.0g of thiourea, dissolving the molybdic acid and the thiourea in 30ml of water in sequence, fully stirring, and reacting for 15h at 180 ℃ to obtain MoS₂Powder;

step two: the MoS prepared in the step one₂The powder was immersed in a mixture of water and isopropyl alcohol at a volume ratio of 1:5 (total volume of water and isopropyl alcohol was 60 ml) and subjected to ultrasonic exfoliation. Crushing for 5.5 hours under the protection of nitrogen, centrifuging the solution obtained after crushing at the rotating speed of 6000r/min, and collecting supernatant; the collected supernatant was centrifuged for 40 minutes to obtain MoS₂Precipitating;

step three: taking Fe₂（CO）₉Placing in 0.1mol/L sulfuric acid solution for 80h, and performing ultrasonic treatment once every 4 hours for 40min each time;

step four: centrifuging the solution in the third step at 3000r/min, washing for 20 times, drying at 75 deg.C under vacuum, and collecting Fe₂（CO）₉；

Step five: 2mg of the collected Fe was taken₂（CO）₉Adding to 98mg MoS₂Then adding 20ml of methanol solution, uniformly mixing, and standing for 80 hours at the constant temperature of 65 ℃;

step six: centrifuging the solution in the fifth step, and separatingThe rotating speed of the core is 6000r/min, and the metal Fe cluster obtained by washing and drying is anchored on the MoS₂The electrocatalyst of (a);

and (3) adding 5mg of the electrocatalyst obtained in the step six into a mixed solution consisting of 10ml of water and 30ml of ethanol to prepare a catalyst solution, dropwise adding a proper amount of the catalyst solution onto 1cm by 1cm of carbon paper, and measuring the reduction activity of the catalyst solution.

Example 3

Fe cluster anchoring on MoS₂The electrocatalyst and the preparation method thereof comprise the following steps:

the method comprises the following steps: weighing 9.0g of molybdic acid and 7.6g of thiourea, dissolving the molybdic acid and the thiourea in 30ml of water in sequence, fully stirring, and reacting for 20 hours at 200 ℃ to obtain MoS₂Powder;

step two: the MoS prepared in the step one₂The powder was immersed in a mixture of water and isopropyl alcohol at a volume ratio of 1:4 (total volume of water and isopropyl alcohol was 60 ml) and subjected to ultrasonic exfoliation. Crushing for 6 hours under the protection of nitrogen, centrifuging the solution obtained after the crushing at the centrifugal rotation speed of 11000r/min, and collecting supernatant; then, the collected supernatant was centrifuged for 20 minutes to obtain MoS₂Precipitating;

step three: taking Fe₂（CO）₉Placing in 0.8mol/L sulfuric acid solution for 70h, and performing ultrasonic treatment once every 4 hours for 20min each time;

step four: centrifuging the solution in step three at 8000r/min, washing for 10 times, drying at 80 deg.C under vacuum, and collecting Fe₂（CO）₉；

Step five: 5mg of the collected Fe was taken₂（CO）₉Adding to 95mg MoS₂Then adding 30ml of methanol solution, uniformly mixing, and standing for 70 hours in a constant temperature environment of 70 ℃;

step six: centrifuging the solution obtained in the step five, washing and drying at the centrifugal rotating speed of 11000r/min to obtain a metal Fe cluster anchored in MoS₂The electrocatalyst of (a);

and (3) adding 1mg of the electrocatalyst obtained in the step six into a mixed solution consisting of 10ml of water and 30ml of ethanol to prepare a catalyst solution, dropwise adding a proper amount of the catalyst solution onto 1cm by 1cm of carbon paper, and measuring the reduction activity of the catalyst solution.

Example 4:

fe cluster anchoring on MoS₂The electrocatalyst and the preparation method thereof comprise the following steps:

the method comprises the following steps: weighing 9.0g of molybdic acid and 7.6g of thiourea, dissolving the molybdic acid and the thiourea in 30ml of water in sequence, fully stirring, and reacting for 20 hours at 220 ℃ to obtain MoS₂Powder;

step two: the MoS prepared in the step one₂The powder was immersed in a mixture of water and isopropyl alcohol at a volume ratio of 1:4 (total volume of water and isopropyl alcohol was 60 ml) and subjected to ultrasonic exfoliation. Crushing for 6 hours under the protection of nitrogen, centrifuging the solution obtained after the crushing at the centrifugal rotation speed of 11000r/min, and collecting supernatant; then, the collected supernatant was centrifuged for 20 minutes to obtain MoS₂Precipitating;

step three: taking Fe₂（CO）₉Placing in 0.8mol/L sulfuric acid solution for 70h, and performing ultrasonic treatment once every 4 hours for 20min each time;

step four: centrifuging the solution in step three at 8000r/min, washing for 10 times, drying at 80 deg.C under vacuum, and collecting Fe₂（CO）₉；

Step five: 5mg of the collected Fe was taken₂（CO）₉Adding to 95mg MoS₂Then adding 30ml of methanol solution, uniformly mixing, and standing for 70 hours in a constant temperature environment of 70 ℃;

step six: centrifuging the solution obtained in the step five, washing and drying at the centrifugal rotating speed of 11000r/min to obtain a metal Fe cluster anchored in MoS₂The electrocatalyst of (a);

and (3) adding 1mg of the electrocatalyst obtained in the step six into a mixed solution consisting of 10ml of water and 30ml of ethanol to prepare a catalyst solution, dropwise adding a proper amount of the catalyst solution onto 1cm by 1cm of carbon paper, and measuring the reduction activity of the catalyst solution.

Comparative example 1

Comparative example 1 differs from example 4 in that step two of comparative example 1 did not match the MoS₂The powder was sonicated using the multilayer structure as is, and the remaining raw materials and processes were the same as in example 4.

As shown in fig. 4, which is a graph of the nitrogen reduction activity test results of examples 1 to 4 and comparative example 1 of the present invention, it can be seen from the graph that the activity is the best at 220 ℃, and compared with the conventional nitrogen reduction reaction requiring high temperature and high pressure at 400 to 600 ℃, the present invention has mild conditions and shows better application prospects.

Example 4 in comparison to comparative example 1, example 4 prepared a monolayer of MoS by multiple sonications₂Exhibit better reduction performance due to the monolayer MoS₂Fully exposing more S vacancies to facilitate bonding with more Fe relative to MoS₂Single Fe atom of at least one in MoS₂More Fe atoms nearby (i.e. Fe)₂/MoS₂) Is favorable to N₂Is favorable for the effective activation of the N-N bond.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.