Preparation method and application of sponge-like porous carbon loaded with metal single atoms

Abstract

A preparation method and application of sponge-like porous carbon-supported metal single atoms, using a metal organic framework compound as a precursor, and in-situ replacement to achieve uniform dispersion of metal single atoms M on a porous carbon matrix. The carbon matrix exhibits elongated, sponge-like porous properties; the metal atoms are in a single-atom dispersion state and are connected to the carbon matrix through N and S atoms, and the N and S atoms are uniformly dispersed. The present invention provides a preparation method of porous carbon-supported metal single atoms M‑S / N, which can effectively increase the catalyst utilization efficiency during the oxygen reduction reaction of zinc-air batteries. The porous structure of the matrix increases gas and electrolyte transmission, and the good electrical conductivity can promote electron transmission. As a positive electrode catalyst for zinc-air batteries, this material exhibits excellent cycle stability and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of zinc-air batteries and relates to positive electrode catalytic materials for zinc-air batteries, and in particular to a preparation method and application of sponge-like porous carbon loaded with metal single atoms. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] With the continuous consumption of fossil energy, clean energy is gradually being utilized. Zinc-air batteries use air as the active material, which is not only environmentally friendly and pollution-free, but also reduces the weight of battery electrode materials and increases energy density. Among them, the oxygen reduction reaction (ORR) is an important electrochemical reaction in zinc-air batteries. How to achieve ORR kinetics improvement through catalyst design, thereby improving the energy storage efficiency of zinc-air batteries, is a key issue. In recent years, single-atom electrocatalysts (SAECs) formed by the coordination of metal atoms and matrices have shown outstanding advantages of excellent performance and low cost. The unique electronic structure and maximum atomic utilization efficiency give SAEC excellent electrocatalytic activity, and are highly selective in the reaction process, thereby improving reaction efficiency.

[0004] However, the inventors found that SAEC is prone to agglomeration during preparation and use, thereby losing its activity and affecting the service life of the zinc-air battery. Achieving uniform dispersion of SAEC on the substrate requires a rational design of the precursor material. MOF is a type of porous three-dimensional network constructed by inorganic metal ions / clusters and organic ligands through coordination bonds. In recent years, it has been widely used as a precursor template to prepare a series of excellent electrode materials with different structures and morphologies. As a template agent, MOF has the following main advantages: ① Diverse structure and composition, providing a large number of precursors to choose from; ② High specific surface area and rich pore structure, its derivatives can partially inherit this advantage, providing more active centers and diffusion channels for electrochemical reactions; ③ Unique inorganic and organic hybrid structure, metal ions / clusters and ligands are intertwined and connected, which can realize the in-situ hybridization of inorganic nanoparticles and nanocarbons, and promote the kinetic process of electrochemical reactions. Therefore, the inventors selected Metal-Organic Framework (MOF) compounds as precursors for preparing single-atom catalysts, and controlled the pyrolysis atmosphere during the calcination process to regulate the connection mode between single atoms and the porous carbon matrix, thereby adjusting the electronic structure and improving the ORR reaction activity. Summary of the Invention

[0005] In order to address the shortcomings of the existing technology, the present invention proposes a preparation method and application of sponge-like porous carbon-supported metal single atoms M. The strategy of N and S double anion doping is adopted to introduce N and S double anions into the MOF derivative to achieve co-doping synergy. At the same time, through precise control of the preparation process, the mother framework of MOF is effectively maintained, and a sponge-like porous structure with a high specific surface area is constructed. The prepared material significantly enhances the electrochemical performance of the metal single atom material in zinc-air batteries as a catalyst.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] On the one hand, a preparation method and application of sponge-like porous carbon loaded with metal single atoms, wherein the metal single atoms are uniformly loaded onto the porous carbon matrix. Spherical aberration electron microscopy shows that the carbon matrix presents elongated, sponge-like porous properties; the metal atoms are in a single-atom dispersion state and are connected to the carbon matrix through N and S atoms, and the N and S atoms are uniformly dispersed. In order to improve the uniform dispersion and strong connection of metal single atoms on the matrix, the carbon matrix contains rich mesopores and micropores, and realizes N and S heteroatom doping and modification. The loaded metal single atoms are positive trivalent metal atoms, which are connected to the carbon matrix through N and S atoms.

[0008] On the other hand, a method for preparing sponge-like porous carbon-loaded metal single atoms is prepared by deriving from Al-MOF. The trivalent metal atom (M) partially replaces the metal Al in situ during the synthesis of Al-MOF to prepare M-Al-MOF, thereby ensuring the uniform dispersion of the metal atom M in the matrix and obtaining a porous carbon-loaded metal single atom material.

[0009] A third aspect relates to the use of an elongated, sponge-like porous carbon-supported metal single-atom material, or a sponge-like porous carbon-supported metal single-atom material obtained using the aforementioned preparation method, in the positive electrode of a zinc-air battery. The porous nature of the prepared electrode material facilitates gas diffusion and ion transport, thereby ensuring the electrochemical reaction proceeds.

[0010] In a fourth aspect, an application of a zinc-air battery includes a zinc negative electrode, an electrolyte containing a zinc salt, a separator, and a catalyst positive electrode.

[0011] In a fifth aspect, a method for preparing a positive electrode of a zinc-air battery includes a current collector, a conductive material, a binder and a catalyst material, wherein the binder bonds the conductive material and the catalyst material to the current collector, and the catalyst material is any of the sponge-like porous carbon-loaded metal single-atom materials described above or the sponge-like porous carbon-loaded metal single-atom material obtained by the preparation method described above.

[0012] The beneficial effects of the present invention are:

[0013] 1. The present invention uses M-Al-MOF as a template, which has rich pores and surface interface effects, increases mass transfer and gas diffusion, and promotes electrochemical reactions.

[0014] 2. The method of calcining in an atmosphere containing heteroatoms or solid decomposable organic matter adopted in the present invention achieves sufficient doping of N and S atoms, which is beneficial to increasing the anchoring of metal atoms and the connection between them and the matrix.

[0015] 3. The metal single atoms in the present invention are obtained by in-situ doping of heterogeneous atoms into Al-MOF, have the characteristics of uniform dispersion, and are fixed by N and S during the calcination process, ensuring the uniform dispersion and effective utilization of the metal single atoms M.

[0016] 4. The material designed by the present invention is applied to zinc-air batteries. The energy storage device has high energy density and broad practical application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : Scanning electron microscopy image of the Fe-Al-MOF obtained in Example 1;

[0018] Figure 2 : X-ray spectrum of Fe-S / N obtained in Example 1;

[0019] Figure 3 : Transmission electron microscopy image and elemental scan of Fe-S / N obtained in Example 1;

[0020] Figure 4 : Spherical aberration electron microscope image of Fe-S / N obtained in Example 1;

[0021] Figure 5 : XPS pattern of Fe-S / N obtained in Example 1;

[0022] Figure 6 : Cycling performance of the zinc-air battery obtained in Example 1. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, 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 belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] Example 1

[0026] A preparation method and application of sponge-like porous carbon supported metal single atom Fe, comprising the following steps:

[0027] (1) Aluminum nitrate nonahydrate and ferric nitrate nonahydrate and 1,4-naphthalenedicarboxylic acid were dissolved in water at a molar ratio of 10:1, and then the two solutions were mixed and fully stirred at room temperature and placed in a reactor. The mixture was heated at 180 degrees Celsius for 24 hours, centrifuged and dried to obtain the precursor Fe-Al-MOF. The morphology of Fe-Al-MOF is shown in its scanning electron micrograph ( Figure 1 ).

[0028] (2) 300 mg of Fe-Al-MOF was placed in a small porcelain boat, and thiourea (CH4N2S) with a mass ratio of 1:2 to the precursor was placed in a large porcelain boat. The small porcelain boat was placed in the large porcelain boat, and the lid was closed. The boat was placed in a tube furnace, and argon was first introduced. The temperature was raised to 300 °C at a heating rate of 2 °C / min and kept warm for 120 minutes. The temperature was then raised to 900 °C at a heating rate of 5 °C / min and kept warm for 120 minutes. When the temperature reached 900 °C, the argon was turned off and the ammonia was turned on. After keeping warm for 120 minutes, the ammonia was turned off and the temperature was lowered to room temperature by argon.

[0029] (3) Weigh 30 mg of the sample carbonized in step (2) and add it to a hydrofluoric acid solution containing 1-10% by mass, and stir at room temperature for 6 hours. Filter and dry to obtain Fe-S / N. The crystallinity of Fe-S / N is shown in its powder X-ray diffraction pattern ( Figure 2 ); the morphology and element distribution of Fe-S / N are shown in its transmission electron microscope image ( Figure 3 ), the surface of the material becomes rough and presents a typical porous structure; the microscopic morphology of Fe-S / N is shown in its spherical aberration electron microscope image ( Figure 4 ); the electron spectrum of Fe-S / N is shown in its XPS diagram ( Figure 5 ), the material contains elements such as Fe, S, and N, indicating that the double anion is successfully introduced into the derivative material.

[0030] (4) Using PTFE as a binder, carbon black as a conductive agent, the prepared Fe-S / N as a catalytic material, and nickel foam as a current collector, a zinc sheet was used as a negative electrode; a mixed solution of zinc acetate and potassium hydroxide was used as an electrolyte; the assembled zinc-air battery can be cycled for more than 300 hours, and its overpotential remains basically unchanged ( Figure 6 ).

[0031] Example 2

[0032] A preparation method and application of sponge-like porous carbon loaded with metal single atom Cr, comprising the following steps:

[0033] (1) Aluminum nitrate nonahydrate and chromium nitrate nonahydrate with a molar ratio of 12:1 were dissolved in water respectively with 1,4-naphthalenedicarboxylic acid. The two solutions were then mixed and fully stirred at room temperature and placed in a reactor. The mixture was heated at 150 degrees Celsius for 15 hours, centrifuged, and dried to obtain the precursor Cr-Al-MOF.

[0034] (2) 300 mg of Cr-Al-MOF was placed in a small porcelain boat, and thiourea (CH4N2S) with a mass ratio of 1:2 to the precursor was placed in a large porcelain boat. The small porcelain boat was placed in the large porcelain boat, and the lid was closed. The boat was placed in a tube furnace, and argon was first introduced. The temperature was raised to 300 °C at a heating rate of 2 °C / min and kept warm for 100 minutes. The temperature was then raised to 900 °C at a heating rate of 5 °C / min and kept warm for 140 minutes. When the temperature reached 900 °C, the argon was turned off and the ammonia was turned on. After keeping warm for 120 minutes, the ammonia was turned off and the temperature was lowered to room temperature by argon.

[0035] (3) Weigh 50 mg of the sample carbonized in step (2) and add it to a hydrofluoric acid solution containing 1-10% by mass, and stir it at room temperature for 10 hours. After filtration, dry it to obtain Cr-S / N.

[0036] (4) Using PTFE as a binder, carbon black as a conductive agent, the prepared Cr-S / N as a catalytic material, and nickel foam as a current collector, a zinc sheet was used as a negative electrode; a mixed solution of zinc acetate and potassium hydroxide was used as an electrolyte; and a zinc-air battery was assembled.

[0037] Example 3

[0038] A preparation method and application of sponge-like porous carbon loaded with metal single atoms In, comprising the following steps:

[0039] (1) Aluminum nitrate nonahydrate and indium nitrate tetrahydrate with a molar ratio of 15:1 were dissolved in water respectively with 1,4-naphthalenedicarboxylic acid. The two solutions were then mixed and stirred thoroughly at room temperature and placed in a reactor. The mixture was heated at 185 degrees Celsius for 15 hours, centrifuged, and dried to obtain the precursor In-Al-MOF.

[0040] (2) 300 mg of In-Al-MOF was placed in a small porcelain boat, and thiourea (CH4N2S) with a mass ratio of 1:3 to the precursor was placed in a large porcelain boat. The small porcelain boat was placed in the large porcelain boat, and the lid was closed. The boat was placed in a tube furnace, and argon was first introduced. The temperature was raised to 300 °C at a heating rate of 2 °C / min and kept warm for 100 minutes. The temperature was then raised to 800 °C at a heating rate of 5 °C / min and kept warm for 140 minutes. When the temperature reached 800 °C, the argon was turned off and the ammonia was turned on. After keeping warm for 120 minutes, the ammonia was turned off and the temperature was lowered to room temperature by argon.

[0041] (3) Weigh 50 mg of the sample carbonized in step (2) and add it to a hydrofluoric acid solution containing 1-10% by mass, and stir it at room temperature for 10 hours. After filtration, dry it to obtain In-S / N.

[0042] (4) Using PTFE as a binder, carbon black as a conductive agent, the prepared In-S / N as a catalytic material, and nickel foam as a current collector, a zinc sheet was used as a negative electrode; a mixed solution of zinc acetate and potassium hydroxide was used as an electrolyte; and a zinc-air battery was assembled.

[0043] Example 4

[0044] A preparation method and application of sponge-like porous carbon loaded with metal single atom Ce, comprising the following steps:

[0045] (1) Aluminum nitrate nonahydrate and cerium nitrate hexahydrate with a molar ratio of 10:1 were dissolved in water respectively with 1,4-naphthalenedicarboxylic acid. The two solutions were then mixed and fully stirred at room temperature and placed in a reactor. The mixture was heated at 165 degrees Celsius for 18 hours, centrifuged, and dried to obtain the precursor Ce-Al-MOF.

[0046] (2) 300 mg of Ce-Al-MOF was placed in a small porcelain boat, and thiourea (CH4N2S) with a mass ratio of 1:3 to the precursor was placed in a large porcelain boat. The small porcelain boat was placed in the large porcelain boat, and the lid was closed. The boat was placed in a tube furnace, and argon was first introduced. The temperature was raised to 300 °C at a heating rate of 2 °C / min and kept warm for 100 minutes. The temperature was then raised to 700 °C at a heating rate of 5 °C / min and kept warm for 140 minutes. When the temperature reached 700 °C, the argon was turned off and the ammonia was turned on. After keeping warm for 120 minutes, the ammonia was turned off and the temperature was lowered to room temperature by argon.

[0047] (3) Weigh 30 mg of the sample carbonized in step (2) and add it to a hydrofluoric acid solution containing 1-10% by mass, and stir at room temperature for 6 hours. Filter and dry to obtain Ce-S / N.

[0048] (4) Using PTFE as a binder, carbon black as a conductive agent, the prepared Ce-S / N as a catalytic material, and nickel foam as a current collector, a zinc sheet was used as a negative electrode; a mixed solution of zinc acetate and potassium hydroxide was used as an electrolyte; and a zinc-air battery was assembled.

[0049] The description of the embodiments disclosed in the present invention is not intended to limit the scope of the present invention, but is used to describe the present invention. Accordingly, the scope of the present invention is not limited by the above embodiments, but is defined by the claims or their equivalents.

Claims

1. A method for preparing sponge-like porous carbon supported by metal single atom Fe, characterized in that: The following steps are involved: Step S1: Aluminum nitrate nonahydrate and ferric nitrate nonahydrate and 1,4-naphthalenedicarboxylic acid in a molar ratio of 10:1 are dissolved in water, respectively. The two solutions are then mixed and fully stirred at room temperature, placed in a reactor, reacted at 180° C. for 24 hours, centrifuged, and dried to obtain a precursor Fe-Al-MOF. Step S2: 300 mg of Fe-Al-MOF was placed in a small porcelain boat, and thiourea with a mass ratio of 1:2 to the precursor was placed in a large porcelain boat. The small porcelain boat was placed in the large porcelain boat, the lid was closed, and the boat was placed in a tube furnace. Argon was first introduced and the temperature was increased to 300°C at a rate of 2°C / min and held for 120 min. The temperature was then increased to 900°C at a rate of 5°C / min and held for 120 min. When the temperature reached 900°C, the argon gas was turned off and the ammonia gas was turned on. After holding for 120 min, the ammonia gas was turned off and the temperature was cooled to room temperature with argon gas. Step S3: Weigh 30 mg of the sample carbonized in step S2, add it to a hydrofluoric acid solution containing 1-10% by mass, and stir it at room temperature for 6 hours. After filtration, dry it to obtain Fe-S / N.

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