A hollow porous carbon material, its preparation method, and a battery

Abstract

The present invention discloses a preparation method of a hollow porous carbon material, which comprises the following steps: dissolving dimethylimidazole in water to form solution A; dissolving zinc nitrate and hydrochloric acid dopamine in water, stirring evenly to form solution B, and then adding it to solution A to form solution C; after stirring and reacting solution C, centrifuging to obtain a catalyst precursor; drying the catalyst precursor and then performing high-temperature calcination. The present invention also discloses the hollow porous carbon material prepared by the above preparation method and a battery using the above hollow porous carbon material as a cathode. The hollow porous carbon material of the present invention is synthesized in an aqueous phase, has a relatively simple production process, less pollution, and is easy to achieve mass production. The prepared hollow porous carbon material has good electrochemical performance as an oxygen reduction electrocatalyst. A zinc-air battery or a microbial fuel cell using it as a cathode has a high power density and excellent stability performance.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and particularly to a hollow porous carbon material, a preparation method thereof, and a battery. Background Art

[0002] Zinc-air (Zn-air) batteries have received extensive attention due to their high energy density, simple manufacturing process, low cost, safety, environmental friendliness, and renewable utilization. A Zn-air battery is a new type of chemical power source with oxygen in the air as the positive electrode active material and metallic zinc as the negative electrode active material. A microbial fuel cell is a device that directly converts the chemical energy in organic matter into electrical energy using electrogenic microorganisms as the anode catalyst, and has broad application prospects in the fields of wastewater treatment and new energy development. A microbial fuel cell utilizes the metabolism of microorganisms to oxidize and decompose organic waste while generating electrical energy. Organic matter is oxidized at the anode to produce electrons and CO2. The electrons are transferred to the cathode through an external circuit. Finally, O2 is the ultimate electron acceptor, combines with protons diffused from the anode to react to form water, thereby generating electrical energy. The slow kinetic reaction rate of the oxygen reduction reaction (ORR) at the cathode is the main factor hindering the performance of Zn-air battery microbial fuel cells. Therefore, the development of cathode catalysts with excellent ORR activity is of great significance for the development of Zn-air batteries and microbial fuel cells. Currently, the optimal ORR catalyst is still a platinum-based catalyst, but it has disadvantages such as scarcity, high price, easy poisoning, and poor methanol tolerance. Therefore, designing and developing green, low-cost, highly active, selective, and stable catalysts is the key to solving this problem. Metal-doped hollow carbon materials have received extensive attention due to their excellent catalytic activity, good selectivity, and high stability. The hollow carbon framework structure can generate more active sites and increase the mass transfer ability, thereby enhancing the ORR catalytic activity. Metal-organic framework ZIF-8, as a typical precursor of porous carbon materials, has characteristics such as good chemical stability, extremely high specific surface area, and extremely large pore volume. However, how to simply prepare hollow porous carbon materials with excellent performance and make them better used as ORR catalysts in Zn-air batteries and microbial fuels is still a difficult point in current research. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of a hollow porous carbon material, which is synthesized in an aqueous phase, has a relatively simple production process, less pollution, and is easy to achieve mass production. The prepared hollow porous carbon material has good electrochemical performance as an oxygen reduction electrocatalyst.

[0004] Another purpose of the present invention is to provide a hollow porous carbon material prepared by the above preparation method.

[0005] Another purpose of the present invention is to provide a battery with high power density and excellent stability performance.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A preparation method of a hollow porous carbon material, comprising the following steps:

[0008] Dissolve dimethylimidazole in water to form solution A;

[0009] Dissolve zinc nitrate and dopamine hydrochloride in water, stir evenly to form solution B, and then add it to solution A to form solution C;

[0010] After the solution C is stirred and reacted, it is centrifuged to obtain a catalyst precursor;

[0011] The catalyst precursor is dried and then calcined at high temperature.

[0012] Preferably, the mass ratio of dimethylimidazole, zinc nitrate, and dopamine hydrochloride is: (3-13):(0.3-1.5):(0.1-0.3).

[0013] Preferably, the stirring reaction of the solution C is specifically: after the solution C is stirred and reacted, a metal salt is added and the stirring reaction is continued.

[0014] Preferably, the dosage ratio of the metal salt to dopamine hydrochloride is (1-8 mmol):1 g.

[0015] Preferably, the metal salt is one or two of inorganic iron salts, inorganic cobalt salts, and inorganic nickel salts.

[0016] More preferably, the metal salt is anhydrous ferric chloride, nickel nitrate hexahydrate, or cobalt nitrate tetrahydrate.

[0017] Preferably, the concentration of dimethylimidazole in the solution A is (8-32) g / 100 mL; the concentration of zinc nitrate in the solution B is (6-30) g / 100 mL.

[0018] Preferably, the zinc nitrate is zinc nitrate hexahydrate.

[0019] Preferably, the reaction time of the solution C is 0.5-2 h.

[0020] Preferably, the reaction time after adding FeCl3 is 12-36 h.

[0021] Preferably, the drying is specifically: drying at 80-100 °C for 12-24 h.

[0022] Preferably, the high-temperature calcination is specifically: calcining at 800-1000 °C for 2-4 h.

[0023] A hollow porous carbon material is prepared by the preparation method of the hollow porous carbon material and has a hollow concave dodecahedron structure.

[0024] A battery includes a cathode, and the cathode is prepared from the hollow porous carbon material; the battery is a zinc-air battery or a microbial fuel cell.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) In the preparation method of the hollow porous carbon material of the present invention, mainly dimethylimidazole, zinc nitrate, and dopamine hydrochloride are used as raw materials. Among them, the ZIF-8 framework structure formed by dimethylimidazole and zinc nitrate will not collapse during the pyrolysis process, and still maintains a good framework structure, which can generate more active sites and increase the mass transfer ability. Among them, Zn in the catalyst precursor gasifies during the pyrolysis process to generate a large number of micropores, thereby achieving the purpose of pore formation without using a template agent, simplifying the experimental operation steps, and accelerating the synthesis speed of the catalyst. Dopamine hydrochloride can polymerize under alkaline conditions, which is beneficial to delaying the formation of ZIF-8, and a carbon film is formed on its surface. The amino group on the surface provides active sites for the anchoring of metal sources and can well inhibit the aggregation of metallic iron.

[0027] (2) In the preparation method of the hollow porous carbon material of the present invention, the metal-doped hollow concave dodecahedron carbon material obtained by doping with metals has highly dispersed metal atoms, which are doped into the carbon skeleton in the form of single atoms, enabling the active sites of the material to be fully exposed. And this structure has a relatively high specific surface area, and its rich hierarchical pore structure can effectively promote the material exchange efficiency in the solid-liquid phase interface, greatly improving the oxygen reduction reaction activity.

[0028] (3) In the preparation method of the hollow porous carbon material of the present invention, the solvent used is water, which is inexpensive, easily available, environmentally friendly, and does not pose a hazard to human health, realizing the concept of green and environmental protection synthesis. The synthesis process is simple, the operation is easy, has universality, and can scale up the experimental scale to a certain extent, so as to increase the yield while maintaining the properties of the material in all aspects and realizing industrial production.

[0029] (4) The hollow porous carbon material prepared by the present invention has obvious catalytic advantages as an oxygen reduction reaction electrocatalyst, especially as a cathode material for zinc-air batteries and microbial fuel cells, and is used as a high-performance cathode catalyst in zinc-air batteries and microbial fuel cells to replace noble metal catalysts. Description of the Drawings

[0030] Figure 1 It is a scanning electron microscope image of the iron-nitrogen co-doped hollow concave dodecahedron carbon material prepared in Example 1 of the present invention.

[0031] Figure 2 It is the transmission electron microscope image and iron element distribution map of the iron and nitrogen co-doped hollow concave dodecahedral carbon material prepared in Example 1 of the present invention.

[0032] Figure 3 It is the nitrogen adsorption and desorption isotherm diagram of the iron and nitrogen co-doped hollow concave dodecahedral carbon material in Example 1 of the present invention.

[0033] Figure 4 It is the pore size distribution diagram of the iron and nitrogen co-doped hollow concave dodecahedral carbon material in Example 1 of the present invention.

[0034] Figure 5 It is the ORR performance test result diagram of the iron and nitrogen co-doped hollow concave dodecahedral carbon material in Example 1 of the present invention compared with 20% Pt / C.

[0035] Figure 6 It is the zinc-air battery performance test result diagram of the iron and nitrogen co-doped hollow concave dodecahedral carbon material in Example 1 of the present invention compared with 20% Pt / C.

[0036] Figure 7 It is the microbial fuel cell performance test result diagram of the iron and nitrogen co-doped hollow concave dodecahedral carbon material in Example 1 of the present invention compared with 20% Pt / C.

[0037] Figure 8 It is the SEM image of the nitrogen-doped irregular polyhedron carbon material prepared in Example 5 of the present invention.

[0038] Figure 9 It is the SEM image of the nitrogen-doped self-derived carbon nanotube porous material prepared in Example 6 of the present invention.

[0039] Figure 10 It is the SEM image of the iron and nitrogen co-doped self-derived carbon nanotube porous material prepared in Example 7 of the present invention. Detailed implementation manners

[0040] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto.

[0041] Example 1

[0042] A preparation method of an iron and nitrogen co-doped hollow concave dodecahedral carbon material (denoted as FeNC) specifically includes the following steps:

[0043] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. After stirring solution C for 1 h, dissolve 0.1 mmol of anhydrous FeCl3 in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h. Then centrifuge the solution to obtain the catalyst precursor, and place it in an oven to dry at 80 °C for 12 h. Finally, perform high-temperature carbonization in a tube furnace at a temperature of 900 °C for 3 h.

[0044] For the FeNC catalyst obtained in this example, its morphology was characterized by scanning electron microscopy, and the results are as Figure 1 shown. It can be clearly seen from Figure 1 that the prepared FeNC catalyst is a hollow and concave dodecahedron structure. The transmission electron microscope was used to study the microstructure of the FeNC catalyst, and the results are as Figure 2 (a) in it shows that the prepared carbon material is a hollow and concave dodecahedron ultrathin carbon layer structure. It can be seen from Figure 2 (b) in it that iron in the catalyst exists in the form of single atoms. Figure 3 And Figure 4 are the specific surface area and pore size analysis of the FeNC catalyst prepared by the above method using a fully automatic physical and chemical sorption analyzer. Figure 3 is the nitrogen adsorption and desorption isotherm diagram of the FeNC catalyst material. The typical type IV adsorption isotherm and H4-type hysteresis loop are mainly due to capillary condensation in the pore structure, and at the same time indicate that there are a large number of micropores and mesopores in the material. Both of these pores play important roles in the oxygen reduction reaction. Among them, micropores can make oxygen molecules in the electrolyte approach the active reaction sites, while mesopores can enhance the mass transfer efficiency, provide sufficient oxygen, and accelerate the ORR reaction process. Figure 4 is the pore size distribution diagram of the FeNC hollow and concave dodecahedron carbon material. It can be seen from Figure 4 that the pore size of the carbon material is mainly composed of micropores and mesopores, supplemented by macropores. Micropores and mesopores can provide active sites, and macropores provide channels, thus effectively improving the ORR activity of the catalyst. Figure 5 is the linear sweep voltammetry (LSV) curve of the ORR activity of the catalysts FeNC and PtC in 0.1 M KOH. It can be obtained from the figure that the initial potential of FeNC is 1.01 V, higher than 1.00 V of PtC, and the half-wave potential of FeNC is 0.886 V, higher than 0.867 V of PtC, and the current density is 6.12 mA cm -2 , higher than 5.71 mA cm -2 of PtC. Figure 6Voltage and power density data of a zinc-air battery assembled with catalysts FeNC and PtC as cathode materials. The open-circuit voltage of the FeNC-based zinc-air battery is 1.453 V, slightly higher than that of the PtC-based (1.446 V). The power density of the FeNC-based zinc-air battery is 460 mW cm -2 which is much higher than 236 mW cm of the PtC-based -2 , indicating that the synthesized catalyst FeNC has good discharge performance in the zinc-air battery. Figure 7 Voltage and power density data of a microbial fuel cell assembled with catalysts FeNC and PtC as cathode materials. The open-circuit voltage of the FeNC-based microbial fuel cell is 818 mV, higher than that of the PtC-based (797 mV). The power density of the FeNC-based microbial fuel cell is 3083 ± 10 mW cm -2 which is much higher than 2405 ± 44 mW cm of the PtC-based -2 . A series of results indicate that the synthesized FeNC catalyst has the potential to replace PtC.

[0045] Example 2

[0046] A preparation method of a cobalt-nitrogen co-doped hollow concave dodecahedral carbon material (denoted as CoNC), which specifically includes the following steps:

[0047] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. After stirring solution C for 1 h, dissolve 0.2 mmol of cobalt nitrate tetrahydrate in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h. Then centrifuge the solution to obtain the catalyst precursor, and place it in an oven to dry at 80 °C for 12 h. Finally, perform high-temperature carbonization in a tube furnace at a temperature of 900 °C and a calcination time of 3 h.

[0048] Example 3

[0049] A preparation method of a nickel-nitrogen co-doped hollow concave dodecahedral carbon material (denoted as NiNC), which specifically includes the following steps:

[0050] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. After stirring solution C for 1 h, dissolve 0.2 mmol of nickel nitrate in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h. Then centrifuge the solution to obtain the catalyst precursor, and place it in an oven to dry at 80 °C for 12 h. Finally, perform high-temperature carbonization in a tube furnace at a temperature of 900 °C and a calcination time of 3 h.

[0051] Example 4

[0052] A preparation method of a nitrogen-doped hollow concave dodecahedral carbon material (denoted as NC) specifically comprises the following steps:

[0053] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. Stir for 16 h. Then centrifuge the solution to obtain a catalyst precursor, and place it in an oven to dry at 80 °C for 14 h. Finally, perform high-temperature carbonization in a tubular furnace at a temperature of 900 °C for a calcination time of 3 h.

[0054] Example 5

[0055] A preparation method of a nitrogen-doped irregular polyhedral carbon material (denoted as NC-2) specifically comprises the following steps:

[0056] Dissolve 12.7 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.744 g of zinc nitrate hexahydrate and 0.1 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. Stir for 16 h. Then centrifuge the solution to obtain a catalyst precursor, and place it in an oven to dry at 80 °C for 14 h. Finally, perform high-temperature carbonization in a tubular furnace at a temperature of 900 °C for a calcination time of 3 h.

[0057] Figure 8 SEM image of the nitrogen-doped irregular polyhedral carbon material prepared in this example.

[0058] Example 6

[0059] A preparation method of a nitrogen-doped self-derived carbon nanotube porous material (denoted as NC-CNTs) specifically comprises the following steps:

[0060] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.2 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. Stir for 16 h. Then centrifuge the solution to obtain a catalyst precursor, and place it in an oven to dry at 80 °C for 14 h. Finally, perform high-temperature carbonization in a tubular furnace at a temperature of 900 °C for a calcination time of 3 h.

[0061] Figure 9 SEM image of the nitrogen-doped self-derived carbon nanotube porous material prepared in this example.

[0062] Example 7

[0063] A preparation method of an iron-nitrogen co-doped self-derived carbon nanotube porous material (denoted as FeNC-CNTs) specifically includes the following steps:

[0064] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of dopamine hydrochloride in 5 mL of water to form solution B, and add it to A to form solution C. After stirring solution C for 1 h, dissolve 0.2 mmol of anhydrous FeCl3 in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h. Then, centrifuge the solution to obtain a catalyst precursor, and place it in an oven to dry at 80 °C for 12 h. Finally, perform high-temperature carbonization in a tube furnace at a temperature of 900 °C and a calcination time of 3 h.

[0065] Figure 10 This is the SEM image of the iron-nitrogen co-doped self-derived carbon nanotube porous material prepared in this example.

[0066] Comparative Example 1

[0067] A preparation method of an iron-nitrogen co-doped porous carbon material (denoted as FeNC-PPy) specifically includes the following steps:

[0068] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of pyrrole in 5 mL of water to form solution B, and add it to A to form solution C. After stirring solution C for 1.5 h, dissolve 0.1 mmol of anhydrous FeCl3 in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h. Then, centrifuge the solution to obtain a catalyst precursor, and place it in an oven to dry at 80 °C for 16 h. Finally, perform high-temperature carbonization in a tube furnace at a temperature of 900 °C and a calcination time of 3 h.

[0069] Comparative Example 2

[0070] A preparation method of an iron-nitrogen co-doped porous carbon material (denoted as FeNC-PANI) specifically includes the following steps:

[0071] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A. Dissolve 0.372 g of zinc nitrate hexahydrate and 0.1 g of aniline in 5 mL of water to form solution B, and add it to A to form solution C. After stirring solution C for 1.5 h, dissolve 0.1 mmol of anhydrous FeCl3 in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h. Then, centrifuge the solution to obtain a catalyst precursor, and place it in an oven to dry at 80 °C for 16 h. Finally, perform high-temperature carbonization in a tube furnace at a temperature of 900 °C and a calcination time of 3 h.

[0072] Comparative Example 3

[0073] A preparation method of a nitrogen-doped porous carbon material (denoted as NC-NoP) specifically includes the following steps:

[0074] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A, dissolve 0.372 g of zinc nitrate hexahydrate in 5 mL of water to form solution B, add it to A to form solution C, and stir for 16 h. Then centrifuge the solution to obtain the catalyst precursor, place it in an oven and dry it at 80 °C for 12 h. Finally, perform high-temperature carbonization in a tubular furnace at a temperature of 900 °C and a calcination time of 3 h.

[0075] Comparative Example 4

[0076] A preparation method of an iron-nitrogen co-doped porous carbon material (denoted as FeNC-NoP) specifically includes the following steps:

[0077] Dissolve 6.35 g of dimethylimidazole in 40 mL of water to form solution A, dissolve 0.372 g of zinc nitrate hexahydrate in 5 mL of water to form solution B, add it to A to form solution C. After stirring solution C for 1 h, dissolve 0.1 mmol of anhydrous FeCl3 in 5 mL of water to form solution D, and then add it to solution C and stir for 12 h; then centrifuge the solution to obtain the catalyst precursor, place it in an oven and dry it at 80 °C for 12 h. Finally, perform high-temperature carbonization in a tubular furnace at a temperature of 900 °C and a calcination time of 3 h.

[0078] Using the control variable method, with the experimental conditions of Example 1 as the basic experimental conditions (that is, unless otherwise specified, the experimental conditions except for the variables are the same as those in Example 1), by changing the types of nitrogen sources (hydroxytyramine hydrochloride, pyrrole, aniline) and metals (iron salts, nickel salts, cobalt salts) in the catalyst, the porous carbon materials shown in Table 1 are prepared. Through comparative experiments, the ORR activity performance of 11 carbon material catalysts and commercial 20% Pt / C in 0.1 M KOH solution is compared. The initial potential and half-wave potential results of each catalyst are summarized and compared as shown in Table 1.

[0079] Table 1 Comparison of ORR data parameters of different examples, comparative examples and PtC under 0.1 M KOH conditions

[0080]

[0081] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the described embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a hollow porous carbon material, characterized in that, It includes the following steps: Dissolve dimethylimidazole in water to form solution A; Dissolve zinc nitrate hexahydrate and dopamine hydrochloride in water, stir evenly to form solution B, and then add it to solution A to form solution C; the mass ratio of dimethylimidazole, zinc nitrate hexahydrate, and dopamine hydrochloride is: 6.35:0.372:0.1; after solution C is stirred and reacted, centrifuge to obtain a catalyst precursor; After the catalyst precursor is dried, it is calcined at 800 - 1000 °C to obtain a hollow porous carbon material with a hollow concave dodecahedron structure; The hollow porous carbon material is used as an oxygen reduction electrocatalyst.

2. The preparation method of the hollow porous carbon material according to claim 1, characterized in that, The stirring reaction of solution C is specifically: after solution C is stirred and reacted, a metal salt is added and the stirring reaction continues.

3. The preparation method of the hollow porous carbon material according to claim 2, characterized in that, The dosage ratio of the metal salt to dopamine hydrochloride is (1 - 8 mmol): 1 g.

4. The preparation method of the hollow porous carbon material according to claim 2, wherein The dosage ratio of the metal salt to dopamine hydrochloride is 1 mmol: 1 g.

5. The method for preparing the hollow porous carbon material according to claim 2, wherein, The metal salt is anhydrous ferric chloride, nickel nitrate hexahydrate, or cobalt nitrate tetrahydrate.

6. The preparation method of the hollow porous carbon material according to claim 1, wherein, The concentration of dimethylimidazole in solution A is (8 - 32) g / 100 mL; the concentration of zinc nitrate hexahydrate in solution B is (6 - 30) g / 100 mL.

7. The preparation method of the hollow porous carbon material according to claim 1, characterized in that, The drying is specifically: drying at 80 - 100 °C, and the drying time is 12 - 24 h.

8. The preparation method of the hollow porous carbon material according to claim 1, wherein, The time of the high-temperature calcination is 2 - 4 h.

9. A hollow porous carbon material prepared by the preparation method of the hollow porous carbon material according to any one of claims 1 - 8.

10. A battery, comprising a cathode, characterized in that, The cathode is prepared from the hollow porous carbon material according to claim 9; the battery is a zinc-air battery or a microbial fuel cell.

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