Iron monatomic catalysts, their preparation and use in orr, zinc-air batteries

Abstract

The application belongs to the field of fuel cells, and particularly relates to a preparation method of a single-iron atom catalyst. A solution containing component A, component B and component C is subjected to a coprecipitation reaction to obtain a precipitate; the precipitate is aged in a component D solution to obtain an aged product; and the aged product is subjected to gradient calcination to obtain the single-iron atom catalyst. The component A contains a compound of formula 1; the component B contains at least one of iron cyanide, dopamine and a salt thereof; the component C contains an iron source and a zinc source; and the component D contains a water-soluble compound having a fragment of formula 3. The application also discloses a material prepared by the method and an application of the material in ORR and fuel cells. Research shows that the material prepared by the method has excellent catalytic activity and stability in ORR, and a metal-air battery assembled by using the material can have excellent limiting current density, peak power and discharge specific capacity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, and particularly relates to the field of zinc-air batteries. BACKGROUND

[0002] With the idea of green low-carbon environmental protection being deeply rooted in people's minds, it is urgent to find clean energy that can replace traditional fossil fuels such as coal, oil and natural gas. Metal-air batteries, such as zinc-air batteries, are attracting attention due to their high energy density, low cost and environmental friendliness. The oxidation-reduction reaction (ORR) is an important process for electrochemical energy storage and conversion, but the poor activity and slow kinetics of the four proton-coupled electron transfer steps hinder the application of zinc-air batteries in the market, and thus are extremely dependent on the efficiency of electrocatalysts.

[0003] The electrocatalysts currently used in the market are mainly based on noble metal catalysts such as platinum (Pt). However, such catalysts are scarce in resources, expensive in price and poor in stability, which is not conducive to the large-scale practical application of zinc-air batteries. Therefore, there is an urgent need to develop non-noble metal catalysts with high catalytic activity, long cycle life and low cost, such as transition metal-nitrogen-carbon (TM-C-N) catalysts, in which the transition metal (TM) refers to iron (Fe), cobalt (Go), nickel (Ni) and manganese (Mn). So far, iron monatomic catalyst Fe-N-C has become one of the most promising candidate materials due to its abundant catalytic reaction sites. Therefore, designing iron monatomic catalysts with high catalytic performance is a prerequisite for the market application of zinc-air batteries.

[0004] Although there have been many studies on iron monatomic catalysts, new materials and preparation methods need to be developed to synthesize iron monatomic catalysts with high catalytic activity and long cycle life. SUMMARY

[0005] In view of the insufficient catalytic effect of existing iron-based ORR catalytic materials, the first object of the present application is to provide a preparation method of iron monatomic catalysts, aiming to prepare ORR catalytic materials with excellent limiting current density, peak power and discharge specific capacity.

[0006] The second object of the present application is to provide the iron monatomic catalyst prepared by the preparation method.

[0007] The third object of the present application is to provide the iron monatomic catalyst for use as an ORR catalyst and for use in the preparation of metal-air batteries based thereon.

[0008] The fourth object of the present application is to provide a metal-air battery comprising the iron monatomic catalyst.

[0009] A method for preparing an iron single-atom catalyst comprises subjecting a solution containing component A, component B, and component C to a coprecipitation reaction to separate a precipitated product; aging the precipitated product in a solution of component D to separate an aged product; and subsequently subjecting the aged product to a gradient calcination to obtain an iron single-atom catalyst.

[0010] The component A comprises a compound of formula 1; the component B comprises at least one of a compound of formula 2, ferrocyanide, dopamine and its salt; the component C comprises an iron source and a zinc source; the component D comprises a water-soluble compound having a fragment of formula 3;

[0011] The gradient calcination process includes a first calcination process at a temperature T1 and a second calcination process at a temperature T2; wherein the temperature T1 is 300-500°C; the temperature T2 is 850-1200°C;

[0012]

[0013] The R1, R2, and R3 are independently H, alkyl, carboxyl, or substituted alkyl with a substituent; the substituent includes at least one of hydroxyl, alkoxy, amino, amidinyl, carboxyl, and phenyl.

[0014] The present invention innovatively co-precipitates component C, a bimetallic component containing iron and zinc, in components A and B, followed by aging in component D before undergoing the two-stage gradient calcination process. This unexpectedly yields an iron single-atom catalyst with unique physicochemical structural characteristics suitable for ORR. For example, a material with abundant ORR catalytic active sites and a uniform distribution of iron nanoparticles with a distinct hollow cage structure can be prepared. Research has also demonstrated that the material produced by this preparation method exhibits excellent catalytic activity and stability in ORR. When assembled into a metal-air battery, it can exhibit ORR catalytic materials with excellent limiting current density, peak power, and discharge specific capacity.

[0015] In the present invention, the R1 can be H, C1~C 10 The substituted alkyl group may be a group with a substituent on a saturated carbon chain of C1 to C6, such as a carboxyl group, an amino group, an indolyl group, or the like. Studies have shown that using an amino-substituted alkyl component A can be combined with other processes to further synergistically improve the material's limiting current density, peak power, and specific discharge capacity.

[0016] Preferably, in the component A, R1 is a carboxymethyl group. Studies of the present invention have shown that the combination of the preferred component A and the process of the present invention can achieve better synergistic performance, which helps to further improve the limiting current density, peak power and discharge specific capacity of the prepared material.

[0017] In the present invention, in the component B, R2 is a C1-C4 alkyl group. There is no particular requirement for the substitution position of R2, for example, it can be the 2nd, 4th or 5th position.

[0018] In the present invention, in the component C, the iron source is a water-soluble compound of divalent iron and / or trivalent iron. The water-soluble compound is, for example, at least one of sulfates, nitrates, chlorides, and organic acid salts of the metal element.

[0019] In the present invention, the zinc source is a water-soluble zinc ion compound.

[0020] In the present invention, the molar ratio of Fe / Zn in the component C is 0.02 to 3:1; further, it can be 0.03 to 2:1.

[0021] Preferably, the molar ratio of component A: component B and component C is 0.1-1.1:2-8:1; further can be 0.8-1:4-8:1.

[0022] In the present invention, the temperature in the coprecipitation stage is 15 to 45° C., and may be room temperature.

[0023] In the present invention, the coprecipitation reaction time is 0.5 h or longer, and further 10 to 35 h. Considering the preparation efficiency, it can be further 20 to 30 h.

[0024] In the present invention, after the coprecipitation reaction, solid-liquid separation is performed to obtain a precipitated product, which is then subjected to a subsequent aging reaction.

[0025] In the present invention, the coprecipitation reaction can be innovatively placed in a solution of component D for aging treatment, which can further effectively regulate the physicochemical structure, grains, grain boundaries, and orientation of the material to obtain a hollow cage structure, provide more catalytic sites, synthesize new electrocatalysts, further improve their oxygen reduction catalytic performance, and enhance their catalytic stability, limiting current density, peak power, and discharge specific capacity.

[0026] In the present invention, the component D comprises at least one of Formula 3-A and Formula 3-B;

[0027]

[0028] The research of the present invention shows that the use of formula 3-A as component D can be further combined with other technical processes to further enhance the ORR performance of the prepared material, which helps to further improve the material's limiting current density, peak power and discharge specific capacity.

[0029] In the present invention, the solvent in the component D solution is, for example, an aqueous solvent, such as water, or a water-organic solvent mixture. The organic solvent is, for example, a water-soluble organic solvent, and may further be a C1-C4 alcohol, acetone, or the like.

[0030] In the present invention, the concentration of the solute in the component D solution is 2 to 10 g / L, preferably 4 to 7 g / L.

[0031] Preferably, the weight ratio of the precipitated product to component D is 1:1-15; further, it can be 1:1.5-5.

[0032] Preferably, the aging treatment temperature is 15-45° C., and can further be room temperature.

[0033] Preferably, the aging treatment time is 0.5 h or longer, preferably 1 to 10 h, and further preferably 5 to 9 h.

[0034] In the present invention, after the aging reaction, solid-liquid separation is performed to obtain an aged product, which is then subjected to a subsequent two-gradient calcination treatment.

[0035] In the present invention, the aged product is innovatively subjected to the two-stage gradient calcination treatment, which can give the prepared material rich ORR-adaptive physicochemical characteristics and obtain better limiting current density, peak power and discharge specific capacity.

[0036] In the present invention, the gradient calcination process is carried out in a protective atmosphere.

[0037] In the present invention, the protective atmosphere is, for example, at least one of nitrogen and inert gas.

[0038] Preferably, the gas pressure during the gradient calcination stage is 1-2.5 MPa, and can further be 1.5-2 MPa. Studies of the present invention have shown that under a preferred slightly positive pressure, the physicochemical structure of the product can be further optimized, and its oxygen reduction catalytic activity can be further improved.

[0039] The temperature T1 is 340-460°C.

[0040] Preferably, the holding time t1 at the temperature T1 is 1 to 6 hours, and can further be 1 to 3 hours.

[0041] Preferably, the temperature T2 is 900-1150°C.

[0042] Preferably, the holding time t2 at the temperature T2 is 1 to 8 hours, and can further be 2 to 4 hours.

[0043] The present invention also provides an iron single-atom catalyst prepared by the preparation method.

[0044] The preparation method of the present invention can give the prepared material special physical and chemical characteristics suitable for ORR, and the material prepared by the preparation method has excellent activity and stability in ORR catalysis. When assembled into a zinc-air battery, excellent limiting current density, peak power and discharge specific capacity can be obtained.

[0045] The present invention also provides an application of the iron single-atom catalyst prepared by the preparation method, which is used as an ORR catalyst.

[0046] In the present invention, the iron single-atom catalyst can be used as an ORR catalytic material based on conventional means, and then used to prepare an ORR catalytic device, such as a battery. For example, one illustrative application of the present invention is to use the iron single-atom catalyst as an ORR catalyst to prepare a metal-air battery, further a zinc-air battery.

[0047] The present invention also provides an electrode for a metal-air battery, which comprises the iron single-atom catalyst prepared by the preparation method.

[0048] The electrode of the present invention, except for the iron single-atom catalyst, may have other components and parts known to the public.

[0049] The present invention also provides a metal-air battery comprising an electrode containing the iron single-atom catalyst of the present invention.

[0050] The metal-air battery of the present invention may have conventional structures, components and ingredients except for the iron single-atom catalyst of the present invention.

[0051] In the present invention, the metal-air battery may further be a zinc-air battery.

[0052] Beneficial effects

[0053] The present invention innovatively co-precipitates component A of formula 1, component B of formula 2, and component C of a Zn-Fe combination, then ages the co-precipitated reaction product with component D, followed by a two-gradient calcination treatment. This unexpectedly yields an iron single-atom catalyst prepared by a new preparation method, providing new preparation materials and ideas, and further improving its catalytic activity and stability in oxygen reduction catalysis.

[0054] In the present invention, based on the new preparation method, the physicochemical structure of the product can be further optimized by further optimizing and controlling component A, component B, component D, and calcination mechanism, so that it can exhibit better performance in oxygen reduction catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1: SEM image of the sample obtained in Example 1;

[0056] Figure 2 : ORR reaction CV diagram of the sample obtained in Example 1;

[0057] Figure 3 : ORR reaction LSV diagram of the sample obtained in Example 1. DETAILED DESCRIPTION

[0058] The following examples illustrate the specific steps of the present invention. It should be understood that these examples are only for illustration of the present invention and are not intended to limit the scope of the present invention in any way. Various processes and methods not described in detail in the present invention are conventional methods well known in the art.

[0059] In the present invention, the raw materials selected can be purchased from commercial sources. In addition, the present invention has no special requirements on the chirality of the raw materials, and can be conventional meso or racemic raw materials.

[0060] Example 1

[0061] Step (1): Coprecipitation

[0062] Component A (Formula 1-A, which is Formula 1 wherein R1 is a carboxymethyl group) and component B are mixed at a molar ratio of 0.92:4:1. and component C (a mixture of ferrous sulfate and zinc nitrate with a Fe / Zn molar ratio of 0.035:1, the molar amount of component C is based on the total molar amount of Fe+Zn) are dispersed in water (in the initial stage, the concentration of component A can be 2±0.5 g / L), and co-precipitated with stirring at room temperature for 24±2 hours, followed by solid-liquid separation to obtain a precipitated product;

[0063] Step (2): Aging

[0064] The precipitated product obtained in step (1) is placed in a solution of component D (Formula 3-A) (the concentration of component D is 4 g / L), wherein the weight ratio of the precipitated product to component D is 1:1.5; then stirred and aged at room temperature for 8 hours; then solid-liquid separation is performed to obtain an aged product;

[0065] Step (3): Two-stage gradient processing

[0066] The aged product obtained in step (2) is placed in a tubular furnace, and an Ar inert atmosphere is introduced to fill the tube with the inert atmosphere until it is saturated. The temperature is raised to 300°C (marked as T1) at a heating rate of 5°C / min, and kept warm for 2h (marked as t1). The temperature is then raised to 900°C (sintering temperature T2) at a heating rate of 5°C / min, and then kept warm for 3h (marked as t2) to obtain an iron single-atom oxygen reduction catalytic material (active material).

[0067] According to GB / T 24533-2019, the specific surface area of ​​the obtained material was measured to be 587.9m 2 / g; a rotating disk electrode was used, and the prepared active material was used as the working electrode (active material, conductive carbon black, and polytetrafluoroethylene were uniformly mixed into a uniform slurry at a mass ratio of 2:1:1, and the slurry was coated on a sheet pressed from nickel foam and gas diffusion membrane, with a plate loading of 1 mg cm -2 Catalytic performance was tested in a three-electrode system using a silver chloride electrode as the working electrode, a platinum electrode as the counter electrode, and the limiting current density of the ORR was tested in a 0.1 M KOH system. The results are shown in Table 1.

[0068] The final active material, conductive carbon black, and polytetrafluoroethylene were uniformly mixed in a mass ratio of 2:1:1 to form a uniform slurry. The slurry was coated on a sheet made of nickel foam and gas diffusion membrane. The electrode loading was 1 mg cm -2 The air cathode was made, the polished zinc sheet was used as the metal cathode, and 6M KOH + 0.2M Zn(Ac)2 was used as the electrolyte. The electrochemical test system was used at 25℃ and the current was 10mAcm -2 The assembled zinc-air battery was tested under a large current of , and the results are shown in Table 1.

[0069] Example 2

[0070] Compared with Example 1, the only difference is that the type of component A is changed. The experimental groups are:

[0071] Group A: Component A is Formula 1-B, and its structure is

[0072] Group B: Component A is Formula 1-C, and its structure is

[0073] The test was carried out in the manner of Example 1. The results are shown in Table 1.

[0074] Example 3

[0075] Compared with Example 1, the only difference is that the type of component B is changed. The experimental groups are:

[0076] Group A: Component B is potassium ferrocyanide;

[0077] Group B: Component B is dopamine hydrochloride;

[0078] The test was carried out in the manner of Example 1. The results are shown in Table 1.

[0079] Example 4

[0080] Compared with Example 1, the only difference is that the type of component D is changed, specifically, component D is replaced by Formula 3-B. Other operations and parameters are the same as in Example 1. Tests were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0081] Example 5

[0082] Compared with Example 1, the only difference is that the conditions of step 3 are changed. The experimental groups are:

[0083] Group A: T1 is 450℃, time t1 is 1.5h; temperature T2 is 1150℃, time t2 is 2h;

[0084] Group B: T1 and T2 heating and holding stages were carried out under slightly positive pressure, the pressure being 1.5-2 MPa;

[0085] Other operations and parameters are the same as in Example 1.

[0086] Example 6

[0087] Compared with Example 1, the only difference is that in step 1, the molar ratio of component A, component B and component C is 1:8:1, and the molar ratio of Fe / Zn in component C is 2:1;

[0088] In step 2, the weight ratio of the precipitated product to component D is 1:5; the aging time is 6 hours;

[0089] Other operations and parameters are the same as in Example 1.

[0090] Comparative Example 1

[0091] Compared with Example 1, the only difference is that in step (1), component A is not added, and other operations and parameters are the same as in Example 1.

[0092] Comparative Example 2

[0093] Compared with Example 1, the only difference is that in step (1), zinc sulfate is not added to component C, and the missing zinc is supplemented by the iron in an equimolar amount. Other operations and parameters are the same as those in Example 1.

[0094] Comparative Example 3

[0095] Compared with Example 1, the only difference is that step (2) is not performed, and the precipitated product of step (1) is directly used as the raw material for the gradient roasting treatment of step (3). Other operations and parameters are the same as those of Example 1.

[0096] Comparative Example 4

[0097] Compared with Example 1, the only difference is that step (2) is not performed, and the ingredient D in step 2 is directly added in the co-precipitation system of step 1, and the precipitated product is directly used as raw material for the gradient calcination process of step (3), and other operations and parameters are the same as Example 1.

[0098] Comparative Example 5

[0099] Compared with Example 1, the only difference is that in step 2, the ingredient D is replaced by the same weight of perchloric acid, and other operations and parameters are the same as Example 1.

[0100] Comparative Example 6

[0101] Compared with Example 1, the only difference is that in step 3, the two-stage gradient calcination process is not performed, that is, the temperature of T1 is set to be the same as T2, and other operations and parameters are the same as Example 1.

[0102] Comparative Example 7

[0103] Compared with Example 1, the only difference is that in step 3, the two-stage gradient calcination process is not performed, that is, the temperature of T2 is set to be the same as T1, and other operations and parameters are the same as Example 1.

[0104] The test results of each case are shown in Table 1:

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from Table 1, the present application innovatively co-precipitates ingredient A, ingredient B and ingredient C, and then performs aging reaction on the co-precipitated reaction product with ingredient D, and then performs two-stage gradient calcination process, so that a new iron monatomic catalyst prepared by a new preparation method is unexpectedly obtained, which provides a new material and a new preparation idea, and further improves the catalytic activity and stability in oxygen reduction catalysis.

Claims

1. A method for preparing an iron single-atom catalyst, characterized in that: A solution containing component A, component B, and component C is subjected to a coprecipitation reaction to separate and obtain a precipitated product; Then, the precipitated product is aged in the component D solution to separate and obtain an aged product; The aged product is then subjected to gradient calcination to obtain; The component A comprises a compound of formula 1; the component B comprises at least one of a compound of formula 2, ferrocyanide, dopamine and its salts; the component C comprises an iron source and a zinc source; the component D comprises a water-soluble compound having a fragment of formula 3; the iron source is a water-soluble compound of divalent iron and / or trivalent iron; The zinc source is a water-soluble zinc ion compound; The gradient calcination process includes a first calcination process at a temperature T1 and a second calcination process at a temperature T2; wherein the temperature T1 is 300-500°C; the temperature T2 is 850-1200°C; Formula 1; Formula 2; Formula 3; The R1, R2, and R3 are independently H, alkyl, carboxyl, or substituted alkyl with a substituent; the substituent includes at least one of hydroxyl, alkoxy, amino, amidino, carboxyl, and phenyl.

2. The method for preparing the iron single-atom catalyst according to claim 1, wherein: In the component A, R1 is H, C1~C 10 The substituted alkyl group is a group with a substituent on a saturated carbon chain of C1 to C6, and the substituent is a carboxyl group, an amino group or an indolyl group.

3. The method for preparing the iron single-atom catalyst according to claim 1, wherein: In the component B, R2 is a C1~C4 alkyl group.

4. The method for preparing the iron single-atom catalyst according to claim 1, wherein: In the component C, the molar ratio of Fe / Zn is 0.02-3:

1.

5. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The molar ratio of component A: component B and component C is 0.1-1.1:2-8:

1.

6. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The temperature during the co-precipitation stage is 15~45°C.

7. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The coprecipitation reaction time is more than 0.5h.

8. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The component D comprises at least one of Formula 3-A and Formula 3-B; Formula 3-A Formula 3-B.

9. The method for preparing the iron single-atom catalyst according to claim 1 or 8, wherein: The concentration of the solute in the component D solution is 2 to 10 g / L.

10. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The weight ratio of the precipitated product to component D is 1:1-15.

11. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The temperature of the aging treatment is 15~45℃.

12. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The aging time is more than 0.5h.

13. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The gradient calcination process was carried out in a protective atmosphere.

14. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The gas pressure in the gradient calcination stage is 1~2.5MPa.

15. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The holding time t1 at temperature T1 is 1~6h.

16. The method for preparing the iron single-atom catalyst according to claim 1, wherein: The holding time t2 at temperature T2 is 1~8h.

17. An iron single-atom catalyst prepared by the preparation method according to any one of claims 1 to 16.

18. Use of an iron single-atom catalyst prepared by the preparation method according to any one of claims 1 to 16, characterized in that: It was used as an ORR catalyst.

19. The use according to claim 18, characterized in that It is used as an ORR catalyst to prepare metal-air batteries.

20. The use according to claim 19, characterized in that It is used as an ORR catalyst to prepare zinc-air batteries.

21. An electrode for a metal-air battery, characterized in that: An iron single-atom catalyst prepared by the preparation method according to any one of claims 1 to 16.

22. The metal-air battery electrode according to claim 21, wherein The metal-air battery is a zinc-air battery.

23. A metal-air battery, characterized in that: Comprising the electrode according to claim 21 or 22.

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