High-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries and its preparation method

Abstract

The present invention belongs to the field of electrocatalytic materials technology and specifically discloses a method for preparing a highly efficient bifunctional heterostructured electrocatalyst for zinc-air batteries. The method comprises the following steps: reacting an iron source, a nickel source, a zinc source, and an organic ligand at room temperature to obtain FeNi@ZIF-8; then pyrolyzing the reactants under an inert atmosphere to obtain FeNi-DACs with a rich porous structure. The FeNi-DACs serve as growth sites for LDHs, and small FeNi-LDHs are subsequently grown in situ on the pores of the FeNi-DACs to obtain the highly efficient bifunctional catalyst FeNi-LDH@DACs. This catalyst is expected to become a large-scale application material for rechargeable zinc-air batteries, replacing precious metal-based catalysts and reducing production and use costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic materials, and specifically relates to a method for preparing a FeNi-LDH@DACs heterostructure catalyst for zinc-air batteries, which is a "sesame-like" FeNi-LDH@DACs catalyst formed by coupling bimetallic atoms, i.e., polyhedrons, and bimetallic hydroxide nanodots. Background Art

[0002] In recent decades, the extensive development and application of fossil fuels have caused their reserves to decline sharply. At the same time, the extensive use of fuels such as coal and oil has also led to increased environmental pollution. Therefore, the urgent need to find new technologies for storing and converting energy is a current research hotspot. Rechargeable zinc-air batteries (ZABs) are green, safe and high-power energy supply devices that can greatly reduce people's dependence on fossil fuels and solve the environmental problems we face today. Among them, bifunctional oxygen electrocatalysts are one of the core factors that determine the efficiency and performance of ZABs. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occur at the air electrode of the battery device. Nanomaterials with high catalytic activity show good application prospects in ZABs.

[0003] For a long time, Pt- and Ru-based catalysts have been the most relied-on materials for ORR / OER because these two types of noble metal catalysts have moderate adsorption and desorption strengths for oxygen-containing intermediates, making them the benchmark catalysts for ORR and OER. However, these two noble metals are extremely low in abundance in nature, are expensive, and have poor durability and anti-poisoning properties, which severely limit their widespread application. Among the many non-noble metal catalysts, atomically dispersed transition metal-nitrogen-carbon (MNC, M = Ni, Fe, Co, etc.) materials have attracted widespread attention due to their noble metal-like catalytic activity. Compared with traditional oxygen electrocatalysts, the active site utilization rate of atomic-level catalysts is almost 100%, which greatly reduces the preparation and use costs of the catalyst. By precisely controlling the material's microstructure and the distribution of atomic sites, the stability and catalytic activity of nanomaterials can be greatly improved.

[0004] In recent years, there have been many reports on single-atom composite catalysts:

[0005] Patent application number 202310684482.6 discloses a FeNi nanoparticle and Fe-N x A method for preparing single-atom co-modified single-walled nanotubes. This method prepares a bifunctional catalyst in which bimetallic nanoparticles and single atoms are co-coupled with highly conductive carbon nanotubes. The voltage difference ΔE is about 0.77V, and its overall performance is not excellent enough, and it performs poorly in ZABs.

[0006] Patent application number 202410113305.7 discloses a composite bifunctional catalyst composed of a nickel-iron alloy and iron single-atom nitrogen-doped carbon. Specifically, the process follows: S1: nickel salt, iron salt, zinc salt, and 2-methylimidazole are mixed separately, blended with methanol, stirred at room temperature, centrifuged, washed, and dried to obtain NiFe / ZIF-8 powder; S2: the dried precursor powder is annealed at 850-1000°C for 1-3 hours under inert gas protection to obtain a nickel-iron alloy and iron single-atom nitrogen-doped carbon ORR / OER bifunctional catalyst. The nickel salt is nickel nitrate hexahydrate, nickel chloride hexahydrate, or nickel acetate tetrahydrate; the iron salt is iron acetylacetonate; and the zinc salt is zinc nitrate hexahydrate. While the catalyst exhibits good ORR catalytic performance, its OER performance is poor and its atomic utilization is limited. In addition, catalysts concentrated in metal clusters / particles, single atoms and other substances mainly exhibit single catalytic activity. This is because there is an upper limit to the catalytic activity of such substances, and conventional single-atom catalysts are easily deactivated under conditions of high-concentration alkaline solution and high potential, making it difficult to exhibit excellent bifunctional catalytic activity.

[0007] In summary, transition metal single-atom catalysts are currently a research hotspot for ZABs, but efficient bifunctional redox reaction (ORR / OER) active sites are still lacking in their applications. Therefore, designing catalysts that can overcome the slow kinetics is crucial for extending the efficient cycle life of ZABs. Therefore, the research and development of catalysts with efficient bifunctional catalytic activity is urgent. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries.

[0009] Bifunctionality refers to oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and heterostructure refers to the heterostructure formed by the coupling of two substances: metal atom pairs (FeNi-DACs) and metal hydroxide (LDH) nanodots, that is, FeNi bimetallic atom pairs are coupled with nanodot-shaped double metal hydroxides to form a heterostructure.

[0010] In order to solve the above problems, the present invention provides a method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries, comprising the following steps:

[0011] Step 1: Evenly mix 850-950 mg of zinc salt, 20-40 mg of iron salt, 40-60 mg of nickel salt, and 40-60 mL of alcohol to obtain solution A;

[0012] Step 2: Evenly mix 1.90-2.10 g of ligand and 40-60 mL of alcohol to obtain solution B;

[0013] Step 3: Under vigorous stirring conditions at 2000-3000 rpm, solution B is quickly added to solution A and stirred evenly (vigorously) until the color of the resulting solution changes from transparent to milky white turbidity (stirring time is about 0.5-1.5 hours), and then allowed to stand at room temperature for 22-26 hours. The resulting precipitate is washed with alcohol, dried (vacuum dried), and ground to obtain the precursor FeNi@ZIF-8;

[0014] Step 4: Pyrolyze the FeNi@ZIF-8 precursor obtained in step 3 at 800-1000°C for 2-4 hours under inert gas protection at a heating rate of 5-15°C / min. After the pyrolysis is completed and cooled to room temperature, the product FeNi-DACs is obtained;

[0015] Explanation: The carbon converted from the organic ligands in FeNi@ZIF-8 can reduce the metal ions to dimetallic atomic pairs; at the above pyrolysis temperature, the zinc ions will be reduced; ZIF-8 represents a metal organic framework (MOFs) mainly composed of zinc ions and organic ligands, Zn 2+ Can be Fe 3+ and Ni 2+ replace.

[0016] Step 5: Evenly mix 65-85 mg of FeNi-DACs, 30-50 mg of nickel salt, 65-85 mg of iron salt, and 30-50 mL of deionized water, and sonicate for 2-4 hours to obtain a mixed solution;

[0017] Step 6: 6-12 ml of 0.05-0.15 M alkali solution was added dropwise (the addition time was about 20-40 min) to the mixed solution obtained in step 5, followed by stirring for 0.5-1.5 h, washing with deionized water, and drying in a vacuum oven at 40-60 ° C (about 24-36 h). After grinding and sieving (until it passed a 300-mesh sieve), an efficient bifunctional electrocatalyst FeNi-LDH@DACs for zinc-air batteries was obtained.

[0018] Note: Alkali is added dropwise to completely precipitate the metal ions in the mixed solution. This allows the metal ions to co-precipitate onto the nitrogen-doped carbon framework (FeNi-DACs) loaded with metal atom pairs. LDH stands for layered metal hydroxide.

[0019] Improvement of the preparation method of the high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention:

[0020] In the step 1:

[0021] The zinc salt is any one of zinc nitrate, zinc acetate, and zinc sulfate;

[0022] The iron salt is any one of ferric nitrate, ferric sulfate, and ferric chloride;

[0023] The nickel salt is any one of nickel nitrate, nickel sulfate and nickel chloride;

[0024] In the step 2:

[0025] The ligands are methylimidazole and dimethylimidazole;

[0026] In the step 5:

[0027] The nickel salt is any one of nickel nitrate, nickel sulfate and nickel chloride;

[0028] The iron salt is any one of ferric nitrate (preferably), ferric sulfate, and ferric chloride;

[0029] As a further improvement of the preparation method of the high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention:

[0030] The alcohol solution in step 1 and step 2 is the same alcohol solution, which is methanol or ethanol;

[0031] In the step 6, the alkali solution is any one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia water.

[0032] As a further improvement of the preparation method of the high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention:

[0033] The nickel salt in step 5 is the same as the nickel salt in step 1.

[0034] As a further improvement to the method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention, in step 3:

[0035] The alcohol washing step comprises: standing the precipitate and washing it with an alcohol solution for 3 to 5 times (so that no impurities such as unreacted organic ligands remain in the FeNi@ZIF-8 after washing);

[0036] The drying step is: drying at 50-80° C. under vacuum conditions for 10-20 hours;

[0037] The grinding step is as follows: grinding until the particles pass through a 300-mesh sieve (i.e., grinding until the particle size disappears).

[0038] As a further improvement of the preparation method of the high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention,

[0039] In the step 1, the zinc salt, the iron salt, and the nickel salt are mixed with the alcohol solution and then magnetically stirred until the zinc salt, the iron salt, and the nickel salt are completely dissolved in the alcohol solution (stirring time is about 20 to 40 minutes);

[0040] In the step 2, the ligand and the alcohol solution are mixed and then magnetically stirred until the ligand is completely dissolved in the alcohol solution (stirring time is about 20 to 40 minutes).

[0041] As a further improvement of the preparation method of the high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention,

[0042] The inert gas used for pyrolysis in step 4 is one of helium, nitrogen and argon.

[0043] As a further improvement of the preparation method of the high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries of the present invention,

[0044] In step 5, the mass ratio of nickel salt to iron salt is 0.45-0.6:1.

[0045] This invention aims to address the limited catalytic activity (ORR) of current single-atom catalysts and their insufficient cycling stability under high potential conditions in alkaline solutions. In light of these difficulties and challenges, double hydroxide (LDH) nanodots are introduced to provide efficient OER active sites. Simultaneously, the bimetallic atom pairs supported on a layered porous carbon matrix enhance the conductivity of the hydroxide. This method offers simple reaction conditions, low cost, and excellent stability.

[0046] This invention discloses a method for preparing a "sesame-like" FeNi-LDH@DACs catalyst for zinc-air batteries, which is composed of double metal atom (FeNi-DACs) polyhedrons coupled with double metal hydroxide (FeNi-LDH) nanodots. FeNi-LDH has an electron-donating effect on DACs, modulating the d-band center of the metal atom sites and the interaction between oxygen-containing intermediates and active sites. Furthermore, it provides a sufficient conductive carbon network for the LDH's OER catalysis process, improving electron transfer efficiency and thus enabling the catalyst to exhibit high ORR / OER activity.

[0047] The present invention reduces reliance on various precious metal materials in production applications, while overcoming the drawbacks of existing materials, such as limited catalytic activity, poor stability, and rapid degradation in highly alkaline solutions. The preparation method is simple and the raw materials are readily available. The "sesame-like" FeNi-LDH@DACs prepared by this method for zinc-air batteries exhibit excellent bifunctional catalytic activity under alkaline conditions. This invention provides a feasible solution for the synthesis of highly efficient bifunctional catalysts and the practical application of ultra-stable ZABs.

[0048] The present invention aims to provide a strategy for synthesizing heterostructures controlled by an interfacial coupling mechanism, by confining the growth of nano-dot FeNi-LDH at the interface of highly conductive carbon-supported DACs to achieve both efficient bifunctional catalytic activity and stability. Another object of the present invention is to apply the above catalyst in rechargeable zinc-air batteries.

[0049] This study uses an interfacial coupling mechanism to control the synthesis of heterostructures, resulting in the synthesis of a sesame-like material, FeNi-LDH@DACs, composed of bimetallic atoms (FeNi-DACs) polyhedrons and double metal hydroxide (FeNi-LDH) nanodots. This heterostructure, combining bimetallic FeNi atoms with efficient ORR catalytic activity and bimetallic FeNi hydroxide with excellent OER catalytic activity, overcomes the sluggish kinetics and achieves a high cycle life for ZABs.

[0050] The present invention discloses a highly efficient bifunctional electrocatalyst for zinc-air batteries, the "sesame-like" FeNi-LDH@DACs, prepared according to any of the above-described methods. The catalyst comprises adjacent heteronuclear bimetallic atom pairs and nanodot-shaped bimetallic hydroxides, exhibiting excellent electrochemical activity and stability, with a half-wave potential of 0.86 V and a current density of 10 mA / cm. 2 (E j＝10 ) is only 300mV, and the voltage difference is only 0.67V, which proves that it has good bifunctional electrocatalytic activity. When this catalyst is used as the air cathode of ZABs and compared with the composite catalyst composed of Pt / C+RuO2 (commercial precious metal catalyst), its open circuit voltage is as high as 1.498V, while Pt / C+RuO2 is only 1.426V. The peak power density during discharge is 211.6mW cm -2 The precious metal composite catalyst was only 149.4 mW cm -2 , at 10 mA cm -2 Under current density conditions of 1.5 volts, the voltage difference increased by only 0.02 V after 1500 stable cycles (500 hours), demonstrating overall superior performance to the precious metal Pt / C+RuO2 composite catalyst. The zinc-air battery catalyst of the present invention not only possesses dual-functional catalytic activity, meeting the application needs of battery development, but also addresses the common issues of low output power, poor cycle stability, and high cost in zinc-air batteries.

[0051] In the present invention:

[0052] The strong interaction between LDH and DACs in FeNi-LDH@DACs can change the charge distribution of the FeNi atomic pairs and enhance the ORR catalytic activity of the FeNi atomic pairs. The structural advantage ensures a strong coupling between the polyhedron and the LDH interface, while controlling the size of the LDH, which not only ensures a good catalytic effect during the reaction, but also improves the stability of the catalyst. It has rich pores and defect structures, which can ensure that the ORR and OER active sites are fully exposed, achieving efficient bifunctional catalysis. The "sesame-like" FeNi-LDH@DACs prepared by the present invention can integrate the catalytic advantages of both LDH and DACs to achieve efficient bifunctional catalytic activity. The key points of the heterostructure synthesis include not only the fine control of the precursor to obtain uniformly distributed bimetallic active sites, but also the need to control the size and distribution of LDH. This synthetic strategy provides a valuable reference for the efficient and economical synthesis of bifunctional electrocatalysts, which may accelerate the commercialization of ZABs.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) The present invention adopts the strategy of controlling the synthesis of heterogeneous structures by interface coupling mechanism to synthesize FeNi-LDH@DACs, which shows excellent ORR / OER catalytic activity and stability in alkaline electrolytes, and the output power and stability in ZABs are better than those of composite precious metal catalysts. The raw materials in this method are simple and easy to obtain, the reaction conditions are relatively mild, the overall cost is low, the method is easy to promote, and it can be mass-produced. By controlling the ratio of zinc source, iron source, nickel source and alkaline solution, by controlling the ratio of metal salts, reaction time, reaction temperature and other parameters, by controlling the pyrolysis time, pyrolysis temperature and other parameters, the "sesame-like" FeNi-LDH@DACs catalyst for zinc-air batteries is regulated. The present invention adopts a wet chemical method to convert Fe 3+ and Ni 2+ Dispersed in the unit cell skeleton of ZIF-8, it forms a rhombic dodecahedron with uniformly distributed FeNi atomic pairs after annealing. Under high temperature conditions, Zn will volatilize in large quantities, causing the polyhedron to produce a large number of mesopores and defect structures, which not only expose a large number of accessible ORR active sites, but also provide suitable anchoring sites for metal ions to generate small-sized LDHs under alkaline conditions, and can also limit the subsequent growth of nanosheets to generate LDH NDs.

[0055] (2) In the FeNi-LDH@DACs for zinc-air batteries of the present invention, FeNi-DACs and FeNi-LDH serve as efficient ORR and OER catalytic active sites, respectively, and the rational coupling of the two can compensate for the inherent defects of the materials and improve the catalytic upper limit, showing better output power and cycle performance in the ZABs test. The half-wave potential of the "sesame-like" FeNi-LDH@DACs heterostructure for zinc-air batteries of the present invention is as high as 0.86 V in 0.1 M KOH solution, and the half-wave potential is as high as 0.86 V at a current density of 10 mA cm -2 The overpotential is only 300 mV, so the voltage difference between OER and ORR is only 0.67 V. Its application in rechargeable ZABs shows excellent output power (211.6 mW cm -2 ) and long cycle stability (500h, 10mA cm -2 ), which is significantly better than Pt / C+RuO2 catalyst (149.4 mW cm -2 ,140h,10mA cm -2 ).

[0056] It is important to emphasize that:

[0057] The metal salt content of NiFe / ZIF-8 obtained by 202410113305.7 is relatively high, and metal alloys and metal atoms will be formed after pyrolysis. However, the metal salt content in the precursor FeNi@ZIF-8 of the present invention is relatively low, and bimetallic atomic pairs will be formed after pyrolysis.

[0058] The OER performance of the present invention is better. The overpotential of 202410113305.7 at 10mA / cm2 is 370mV, while that of the present invention is 300mV. The power density of the present invention is relatively higher, which is 211.6mW cm -2 , the peak power density of 202410113305.7 is 202mW / cm2.

[0059] In summary, the present invention provides a method for preparing a highly efficient bifunctional heterostructure electrocatalyst for zinc-air batteries. The method comprises the following steps: using an iron source, a nickel source, a zinc source, and an organic ligand as reaction materials, reacting at room temperature to obtain FeNi@ZIF-8, then pyrolyzing the FeNi-DACs under an inert atmosphere to obtain FeNi-DACs with a rich porous structure. The FeNi-DACs serve as growth sites for LDHs, and then in situ growing small FeNi-LDHs on the pores of the FeNi-DACs to obtain the highly efficient bifunctional catalyst FeNi-LDH@DACs. The advantages of the present invention are that the catalyst synthesis process is simple, the raw materials are readily available, and it is suitable for large-scale production. In alkaline solution, the catalyst exhibits excellent catalytic performance in both the oxygen reduction reaction and the oxygen evolution reaction. When applied to rechargeable zinc-air batteries, the open circuit voltage can reach 1.498V, while also exhibiting excellent cycling stability (1500h) and rate capability. This indicates that the catalyst has the potential to become a large-scale application material for rechargeable zinc-air batteries, replacing precious metal-based catalysts and reducing production and use costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0061] Figure 1 Schematic diagram of the preparation method of the zinc-air battery electrocatalyst of the present invention;

[0062] Figure 2 This is the XRD pattern of the zinc-air battery electrocatalyst prepared in Example 2 of the present invention;

[0063] Figure 3 The SEM and STEM images of the zinc-air battery electrocatalyst prepared in Example 2 of the present invention;

[0064] Figure 4 LSV diagram of the zinc-air battery electrocatalyst prepared in Example 2 of the present invention before and after cycling;

[0065] Figure 5 The discharge curve and corresponding power diagram of the zinc-air battery prepared in Example 2 of the present invention;

[0066] Figure 6 This is a cyclic charge and discharge diagram of the zinc-air battery prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0067] To further illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention, and the scope of protection of the present invention is not limited thereto.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Meanwhile, the term "and / or / and" as used herein includes any combination of one or more of the related listed items.

[0069] In the following case: the vigorous stirring in step 3 is 2500 rpm; the stirring speed in the remaining steps is 1000 rpm.

[0070] Example 1: A method for preparing a high-efficiency bifunctional electrocatalyst for zinc-air batteries, comprising the following steps:

[0071] Step 1: Evenly mix 850 mg of zinc nitrate hexahydrate, 20 mg of ferric nitrate nonahydrate, 40 mg of nickel nitrate hexahydrate, and 40 ml of methanol, and stir thoroughly until dissolved (magnetic stirring for 20 min) to obtain solution A;

[0072] Step 2: 1.90 g of dimethylimidazole and 40 ml of methanol were uniformly mixed and stirred thoroughly until dissolved (magnetic stirring for 20 min) to obtain solution B;

[0073] Step 3: Liquid B was rapidly added to Liquid A under vigorous stirring at 2500 rpm and stirred rapidly for 60 minutes (at this time, the color of the mixed solution changed from transparent to milky white turbidity), and then allowed to stand at room temperature for 22 hours. The obtained product was washed with methanol three times (the amount of methanol used in each wash was about 45 ml), and then vacuum dried at 50°C overnight (12 hours) and then ground (until it passed a 300-mesh sieve) to obtain the precursor FeNi@ZIF-8; set aside;

[0074] Step 4: The precursor FeNi@ZIF-8 obtained in step 3 was pyrolyzed at 800°C for 2 h under Ar atmosphere at a heating rate of 5°C / min. After the pyrolysis was completed, it was naturally cooled to room temperature to obtain the product FeNi-DACs;

[0075] Step 5: Evenly mix 65 mg of FeNi-DACs, 30 mg of nickel nitrate hexahydrate, 65 mg of ferric nitrate nonahydrate, and 30 ml of deionized water, and ultrasonicate for 2 h to obtain a mixed solution;

[0076] Step 6: 6 ml of 0.05 M alkali solution (potassium hydroxide aqueous solution) was added dropwise to the mixed solution obtained in the above step 5 (the addition time was about 30 min), followed by stirring for 0.5 h, washing with deionized water (about 40 ml), and drying in a vacuum oven at 50 ° C to constant weight (about drying for 24 h). After grinding (until passing a 300-mesh sieve), an efficient bifunctional electrocatalyst FeNi-LDH@DACs for zinc-air batteries was obtained.

[0077] The specific surface area of ​​the catalyst prepared in Example 1 is 481.9 m 2 g -1 .

[0078] Its performance data are as follows:

[0079] Electrochemical tests showed that the half-wave potential of the catalyst obtained in Example 1 in a strong alkaline solution with a pH of 13 was 0.75 V. j＝10 The overpotential is 580V and the voltage difference is 1.06V.

[0080] When used in ZABs, the open circuit voltage is 1.420 V and the power density during discharge is 161.2 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.10V after 420 stable cycles (140h).

[0081] Example 2: A method for preparing a high-efficiency bifunctional electrocatalyst for zinc-air batteries, comprising the following steps:

[0082] Step 1: 900 mg of zinc nitrate hexahydrate, 30 mg of ferric nitrate nonahydrate, 50 mg of nickel nitrate hexahydrate, and 50 ml of methanol were uniformly mixed and stirred thoroughly (magnetic stirring for 20 min) to obtain solution A;

[0083] Step 2: 2.00 g of dimethylimidazole and 50 ml of methanol solution were uniformly mixed and fully stirred (magnetic stirring for 20 min) to obtain solution B;

[0084] Step 3: Liquid B was rapidly added to Liquid A under vigorous stirring at 2500 rpm and stirred rapidly for 60 minutes (at this time, the color of the mixed solution changed from transparent to milky white turbidity), and then allowed to stand at room temperature for 24 hours. The obtained product was washed with methanol three times, dried under vacuum at 50°C overnight, and then ground to obtain the precursor FeNi@ZIF-8; set aside;

[0085] Step 4: The precursor FeNi@ZIF-8 obtained in step 3 was pyrolyzed at 900°C for 3 h in an Ar atmosphere at a heating rate of 10°C / min. After the pyrolysis was completed and naturally cooled to room temperature, the product obtained was FeNi-DACs;

[0086] Step 5: Evenly mix 75 mg of FeNi-DACs, 40 mg of nickel nitrate hexahydrate, 75 mg of ferric nitrate nonahydrate, and 40 ml of deionized water, and sonicate for 3 h to obtain a mixed solution;

[0087] Step 6: 9 ml of 0.10 M alkali solution (potassium hydroxide aqueous solution) was added dropwise to the mixed solution obtained in the above step 5 (the addition time was about 30 min), followed by stirring for 1.0 h. After washing with deionized water, the mixture was dried in a vacuum oven at 50 ° C to constant weight (about 24 h). After grinding, an efficient bifunctional electrocatalyst FeNi-LDH@DACs for zinc-air batteries was obtained.

[0088] The specific surface area of ​​the catalyst prepared in Example 2 is 646.4 m 2 g -1 .

[0089] Its performance data are as follows:

[0090] Electrochemical tests showed that the half-wave potential of the catalyst obtained in Example 2 in a strong alkaline solution with a pH of 13 was 0.86 V. j＝10 The overpotential is 300V and the voltage difference is 0.67V.

[0091] When used in ZABs, the open circuit voltage is 1.498 V and the power density during discharge is 211.6 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by only 0.02V after 1500 stable cycles (500h).

[0092] In addition, the half-wave potential of FeNi-DACs is 0.85 V, E j＝10 The overpotential is 400 V, and its electrochemical performance is far from that of the final FeNi-LDH@DACs.

[0093] Example 3: A method for preparing a high-efficiency bifunctional electrocatalyst for zinc-air batteries, comprising the following steps:

[0094] Step 1: Evenly mix 950 mg of zinc nitrate hexahydrate, 40 mg of ferric nitrate nonahydrate, 60 mg of nickel nitrate hexahydrate, and 60 ml of methanol, and stir thoroughly (magnetic stirring for 20 min) to obtain solution A;

[0095] Step 2: 2.10 g of dimethylimidazole and 60 ml of methanol were uniformly mixed and stirred thoroughly (magnetic stirring for 20 min) to obtain solution B;

[0096] Step 3: Liquid B was rapidly added to Liquid A under vigorous stirring at 2500 rpm, and the mixture was stirred rapidly for 60 minutes (at this time, the color of the mixed solution changed from transparent to milky white turbidity), and then allowed to stand at room temperature for 26 hours. The obtained product was washed with methanol three times and dried under vacuum at 50°C overnight (12 hours) to obtain the precursor FeNi@ZIF-8; set aside;

[0097] Step 4: The precursor FeNi@ZIF-8 obtained in step 3 was pyrolyzed at 1000°C for 4 h under an Ar atmosphere at a heating rate of 15°C / min. After the pyrolysis was completed and naturally cooled to room temperature, the product obtained was FeNi-DACs;

[0098] Step 5: Evenly mix 85 mg of FeNi-DACs, 50 mg of nickel nitrate hexahydrate, 85 mg of ferric nitrate nonahydrate, and 50 ml of deionized water, and ultrasonicate for 4 hours to obtain a mixed solution;

[0099] Step 6: 12 ml of 0.15 M alkali solution (potassium hydroxide aqueous solution) was added dropwise to the mixed solution obtained in the above step 5 (the addition time was about 30 min), followed by stirring for 1.5 h. After washing with deionized water, the mixture was dried in a vacuum oven at 50 ° C to constant weight (about 24 h). After grinding, an efficient bifunctional electrocatalyst FeNi-LDH@DACs for zinc-air batteries was obtained.

[0100] The specific surface area of ​​the catalyst prepared in Example 3 is 703.9 m 2 g -1 , the overall catalytic activity is poorer than that of Example 2.

[0101] Its performance data are as follows:

[0102] Electrochemical tests showed that the half-wave potential of the catalyst obtained in Example 3 in a strong alkaline solution with a pH of 13 was 0.84 V. j＝10 The overpotential is 360V and the voltage difference is 0.75V.

[0103] When used in ZABs, the open circuit voltage is 1.485 V and the power density during discharge is 189.6 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.12V after 750 stable cycles (250h).

[0104] In summary, Example 2 is a preferred case.

[0105] Comparative Example 1: Change "40 mg nickel nitrate hexahydrate, 75 mg ferric nitrate nonahydrate" in step 5 of Example 2 to "80 mg nickel nitrate hexahydrate, 150 mg ferric nitrate nonahydrate"; the rest is the same as Example 2.

[0106] The results obtained are: the specific surface area of ​​the prepared catalyst is 609.2m 2 g -1 .

[0107] Its performance data are as follows:

[0108] Electrochemical tests showed that the catalyst obtained in Comparative Example 1 had a half-wave potential of 0.81 V in a strong alkaline solution at pH = 13, and E j＝10 The overpotential is 450V and the voltage difference is 0.87V.

[0109] When used in ZABs, the open circuit voltage is 1.480 V and the power density during discharge is 153.1 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.15V after 600 stable cycles (200h).

[0110] Comparative Example 2: Change “40 mg nickel nitrate hexahydrate, 75 mg ferric nitrate nonahydrate” in step 5 of Example 2 to “20 mg nickel nitrate hexahydrate, 37.5 mg ferric nitrate nonahydrate”, and the rest is the same as Example 2.

[0111] The results obtained are: the specific surface area of ​​the prepared catalyst is 650.8m 2 g -1 .

[0112] Its performance data are as follows:

[0113] The electrocatalytic activity data are as follows: The catalyst obtained in Comparative Example 2 has a half-wave potential of 0.82 V in a highly alkaline solution at pH = 13, and a current density of 10 mA cm -2 The overpotential is 400mV and the voltage difference is 0.81V.

[0114] When used in ZABs, the open circuit voltage is 1.476 V and the power density during discharge is 160.5 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.16V after 720 stable cycles (240h).

[0115] Comparative Example 3

[0116] Steps 1 to 4 are the same as those in Example 2;

[0117] Step 5: Add 40 mg of nickel nitrate hexahydrate, 75 mg of ferric nitrate nonahydrate, and 9 ml of 0.10 M alkali solution (potassium hydroxide aqueous solution) to 40 ml of deionized water, and react at room temperature and a rotation speed of 1000 rpm for 1 hour; wash with deionized water, and dry in a vacuum oven at 50°C to constant weight to obtain the product FeNi-LDH;

[0118] Then 75 mg of FeNi-DACs was added and physically ground with the above FeNi-LDH for one hour to obtain a highly efficient bifunctional electrocatalyst FeNi-LDH / DACs for zinc-air batteries (FeNi-DACs and FeNi-LDH were only connected in a stacked state).

[0119] The results obtained are: the specific surface area of ​​the prepared catalyst is 603.9m 2 g -1 .

[0120] The electrocatalytic activity data are as follows: the half-wave potential of the obtained catalyst in a strong alkaline solution of pH = 13 is 0.83 V, and the current density is 10 mA cm -2 The overpotential is 390mV and the voltage difference is 0.79V.

[0121] When used in ZABs, the open circuit voltage is 1.491 V and the power density during discharge is 172.9 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.14V after 780 stable cycles (260h).

[0122] In Comparative Example 3, it is difficult to form an effective heterostructure between FeNi-DACs and FeNi-LDH by physical grinding, so the electrochemical and battery performance of FeNi-LDH / DACs are not as good as those in Example 2 of the present invention.

[0123] Comparative Example 4-1: The “40 mg of nickel nitrate hexahydrate, 75 mg of ferric nitrate nonahydrate” in step 5 of Example 2 was changed to “20 mg of nickel nitrate hexahydrate, 95 mg of ferric nitrate nonahydrate”, that is, the mass ratio of the nickel source to the iron source was 0.21:1; the rest was the same as in Example 2.

[0124] The results obtained are: the specific surface area of ​​the prepared catalyst is 637.3m 2 g -1 The electrocatalytic activity data are as follows: the half-wave potential of the obtained catalyst in a strong alkaline solution of pH = 13 is 0.79 V, and the current density is 10 mA cm -2 The overpotential is 470 mV, resulting in a voltage difference of 0.91 V.

[0125] When used in ZABs, the open circuit voltage is 1.461 V and the power density during discharge is 142.9 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.24V after 390 stable cycles (130h).

[0126] Comparative Example 4-2: The “40 mg of nickel nitrate hexahydrate, 75 mg of ferric nitrate nonahydrate” in step 5 of Example 2 was changed to “55 mg of nickel nitrate hexahydrate, 60 mg of ferric nitrate nonahydrate”, that is, the mass ratio of the nickel source to the iron source was 0.91:1; the rest was the same as in Example 2.

[0127] The results obtained are: the specific surface area of ​​the prepared catalyst is 643.7m 2 g -1 .

[0128] The electrocatalytic activity data are as follows: the half-wave potential of the obtained catalyst in a strong alkaline solution of pH = 13 is 0.80 V, and the current density is 10 mA cm -2 The overpotential is 400mV and the voltage difference is 0.83V.

[0129] When used in ZABs, the open circuit voltage is 1.479 V and the power density during discharge is 170.6 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.21V after 900 stable cycles (300h).

[0130] Comparative Example 5: The “9 ml of 0.10 M alkali solution (potassium hydroxide aqueous solution)” in step 6 of Example 2 was changed to “4.5 ml of 0.10 M alkali solution”, that is, the amount of alkali solution was changed to half of that in Example 2; the rest was the same as in Example 2.

[0131] The results obtained are: the specific surface area of ​​the prepared catalyst is 649.8m 2 g -1 The electrocatalytic activity data are as follows: the half-wave potential of the obtained catalyst in a strong alkaline solution of pH = 13 is 0.83 V, and the current density is 10 mA cm -2 The overpotential is 390mV, resulting in a voltage difference of 0.79V.

[0132] When used in ZABs, the open circuit voltage is 1.481 V and the power density during discharge is 172.3 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.16V after 900 stable cycles (300h).

[0133] Comparative Example 6: The "9 ml of 0.10 M alkali solution" in step 6 of Example 2 was changed to "18 ml of 0.10 M alkali solution", that is, the amount of alkali solution was changed to twice that of Example 2; the rest was the same as Example 2.

[0134] The results obtained are: the specific surface area of ​​the prepared catalyst is 573.5m2 g -1 The electrocatalytic activity data are as follows: the half-wave potential of the obtained catalyst in a strong alkaline solution of pH = 13 is 0.76 V, and the current density is 10 mA cm -2 The overpotential is 370mV, resulting in a voltage difference of 0.84V.

[0135] When used in ZABs, the open circuit voltage is 1.453 V and the power density during discharge is 149.2 mW cm -2 , at 10mAcm -2 Under the current density condition, the voltage difference between charge and discharge increased by 0.23V after 480 stable cycles (160h).

[0136] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries, characterized in that The steps include: Step 1: Mix 850-950 mg of zinc salt, 20-40 mg of iron salt, 40-60 mg of nickel salt, and 40-60 mL of alcohol to obtain solution A. The zinc salt is any one of zinc nitrate, zinc acetate, and zinc sulfate; The iron salt is any one of ferric nitrate, ferric sulfate, and ferric chloride; The nickel salt is any one of nickel nitrate, nickel sulfate, and nickel chloride; Step 2: Solution B was obtained by uniformly mixing 1.90-2.10 g of ligand and 40-60 mL of alcohol solution; The ligand is methylimidazole or dimethylimidazole; Step 3: Solution B was rapidly added to solution A under vigorous stirring at 2000-3000 rpm and stirred evenly until the color of the resulting solution changed from transparent to milky white and turbid. The solution was then allowed to stand at room temperature for 22-26 hours. The resulting precipitate was washed with alcohol, dried, and ground to obtain the precursor FeNi@ZIF-8. Step 4: The precursor FeNi@ZIF-8 obtained in step 3 was pyrolyzed at 800-1000 °C for 2-4 h under inert gas protection at a heating rate of 5-15 °C / min. After the pyrolysis was completed and cooled to room temperature, the product FeNi-DACs was obtained. Step 5: Mix 65-85 mg of FeNi-DACs, 30-50 mg of nickel salt, 65-85 mg of iron salt, and 30-50 mL of deionized water, then sonicate for 2-4 h to obtain a mixed solution. The nickel salt is the same as the nickel salt in step 1; The iron salt is any one of ferric nitrate, ferric sulfate, and ferric chloride; Step 6: Add 6-12 ml of 0.05-0.15 M alkali solution dropwise to the mixed solution obtained in step 5, then stir for 0.5-1.5 h, wash with deionized water, and dry in a vacuum oven at 40-60 °C. After grinding and sieving, the highly efficient bifunctional electrocatalyst FeNi-LDH@DACs for zinc-air batteries is obtained.

2. The method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries according to claim 1, characterized in that: The alcohol solution in step 1 and step 2 is the same alcohol solution, which is methanol or ethanol; In the step 6, the alkali solution is any one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia water.

3. The method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries according to claim 2, characterized in that In the step three: The alcohol washing step comprises: standing the precipitate and washing it with alcohol solution for 3 to 5 times; The drying step is as follows: drying at 50-80°C under vacuum conditions for 10-20 hours; The grinding step is as follows: grinding until the powder passes through a 300-mesh sieve.

4. The method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries according to claim 3, characterized in that: In the step 1, the zinc salt, the iron salt, and the nickel salt are mixed with the alcohol solution and then magnetically stirred until the zinc salt, the iron salt, and the nickel salt are completely dissolved in the alcohol solution; In the step 2, the ligand is mixed with the alcohol solution and then magnetically stirred until the ligand is completely dissolved in the alcohol solution.

5. The method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries according to claim 4, characterized in that: The inert gas used for pyrolysis in step 4 is one of helium, nitrogen and argon.

6. The method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries according to claim 5, characterized in that: In step 5, the mass ratio of nickel salt to iron salt is 0.45-0.6:

1.

7. The method for preparing a high-efficiency bifunctional heterostructure electrocatalyst for zinc-air batteries according to any one of claims 1 to 6, characterized by the following steps: Step 1: Evenly mix 900 mg of zinc nitrate hexahydrate, 30 mg of ferric nitrate nonahydrate, 50 mg of nickel nitrate hexahydrate, and 50 ml of methanol, and stir thoroughly to obtain solution A. Step 2: 2.00 g of dimethylimidazole and 50 ml of methanol solution were uniformly mixed and stirred thoroughly to obtain solution B; Step 3: Liquid B was rapidly added to Liquid A under vigorous stirring at 2500 rpm and stirred rapidly for 60 minutes until the color of the resulting solution changed from transparent to milky white turbidity. The solution was then allowed to stand at room temperature for 24 hours. The obtained product was washed with methanol, vacuum dried, and then ground to obtain the precursor FeNi@ZIF-8. Step 4: The precursor FeNi@ZIF-8 obtained in step 3 was pyrolyzed at 900 °C for 3 h in an Ar atmosphere at a heating rate of 10 °C / min. After the pyrolysis was completed and naturally cooled to room temperature, the product obtained was FeNi-DACs. Step 5: Evenly mix 75 mg of FeNi-DACs, 40 mg of nickel nitrate hexahydrate, 75 mg of ferric nitrate nonahydrate, and 40 ml of deionized water, and then sonicate to obtain a mixed solution; Step 6: 9 ml of 0.10 M potassium hydroxide aqueous solution was added dropwise to the mixed solution obtained in the above step 5, followed by stirring for 1.0 h. After washing with deionized water, the mixture was dried in a vacuum oven and then ground to obtain FeNi-LDH@DACs, a highly efficient bifunctional electrocatalyst for zinc-air batteries.

Images