A bimetallic site-doped carbon-based catalyst and its preparation method and application

Abstract

A bimetallic active site-doped carbon-based catalyst, specifically a ZnMn-N-C catalyst, uses 1H-1,2,3-triazole, manganese nitrate, and zinc chloride as reaction raw materials. Through a solvothermal reaction and drying, Mn-MET-ZnCl2 powder is obtained, and then through primary pyrolysis, sulfuric acid treatment, and secondary pyrolysis, the ZnMn-N-C catalyst is obtained. In the present invention, by using 1H-1,2,3-triazole and zinc chloride as pore-forming agents for mesopores and micropores respectively, the pore-forming sequence is adjusted and the pore-forming process is controlled through pyrolysis. A large number of mesopores are preferentially formed, and then a large number of micropores are evenly distributed in the mesopores, forming a hierarchical pore structure, solving the problem of pore structure collapse faced in forming this structure. The obtained bimetallic site-doped carbon-based catalyst ZnMn-N-C has a high specific surface area of 1837.9 m² / g, exhibits excellent ORR activity, E 1 / 2 = 0.867 V vs. RHE. The primary zinc-air battery assembled with it as the positive electrode oxygen reduction catalyst has a high energy density of 889 Wh / kg-1 Zn.

Description

Technical Field

[0001] The present invention relates to electrochemical catalyst technology, and in particular to a bimetallic site-doped carbon-based catalyst and a preparation method and application thereof. Background Art

[0002] Energy is the foundation and driving force of human civilization progress. Due to the growing demand for energy, the consumption of fossil fuels and the total carbon emissions are rising rapidly. The development of clean, low-carbon, safe and efficient energy has received widespread attention in reducing greenhouse gas emissions and addressing climate change. Zinc-air batteries (ZABs) have become one of the effective electrochemical devices to solve energy shortages and environmental pollution due to their advantages such as high safety, environmental friendliness and high theoretical energy density. However, the sluggish kinetics of the oxygen reduction reaction (ORR) occurring at the cathode severely limits the large-scale commercial application of zinc-air batteries. With the in-depth study of reducing or replacing platinum-based catalysts with non-precious metals in fuel cells, carbon-based catalysts have become a popular exploration direction for the preparation of high-performance non-platinum ORR electrocatalysts due to their excellent conductivity, stability and porous structure. Driven by the need to reduce PGMs, transition metal embedded nitrogen-carbon composites (MNCs) have received widespread attention due to their ORR catalytic activity comparable to that of Pt / C.

[0003] The emerging transition metal iron nitrogen doped carbon-based single atom catalysts (Fe-NC SACs) have unique structures and excellent catalytic activity, and have become the main direction of current research. However, their severe Fenton reaction will lead to poor stability and reduce the performance and safety of electrochemical conversion devices. In contrast, Mn / Zn-NC has an intrinsic activity close to that of Fe-NC in the ORR process, and the Fenton reaction is negligible. Therefore, the preparation of non-Fe-based oxygen reduction catalysts with a large number of accessible active sites is currently a feasible solution to replace Pt-based catalysts.

[0004] In the prior art, the preparation of Mn / Zn-NC composite materials is to first form a microporous structure precursor with zinc salt and dimethylimidazole, and then form a mesoporous structure in the microporous structure precursor to form a Mn / Zn-NC composite material with coexistence of micropores and mesopores. The microporous structure can increase the adsorption of Zn and Mn, while the mesoporous structure exposes more active sites of the catalyst. The two can work synergistically to improve its catalytic activity. However, first forming micropores and then forming mesopores on the basis of micropores is at the expense of the microporous structure. The more mesopores formed in this process route, the more the microporous structure will be sharply reduced, and the overall performance is not ideal. Summary of the invention

[0005] Based on the above technical problems, the present invention aims to provide a method for preparing a bimetallic active site doped carbon-based catalyst. In the method, the pore-forming sequence is to first create mesopores and then create micropores, thereby obtaining a bimetallic active site doped carbon-based catalyst with more abundant mesopores and micropores coexisting, and effectively improving the catalytic activity of the catalyst.

[0006] Another object of the present invention is to provide a bimetallic active site doped carbon-based catalyst prepared by the above method.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A bimetallic active site doped carbon-based catalyst, specifically a ZnMn-NC catalyst, characterized in that: 1H-1,2,3-triazole, manganese nitrate and zinc chloride are used as reaction raw materials, and Mn-MET-ZnCl is obtained by solvent thermal reaction and drying. 2 The powder is then subjected to primary pyrolysis, sulfuric acid treatment and secondary pyrolysis to obtain a ZnMn-NC catalyst, which has a mesoporous distribution inside, and a hierarchical pore structure of micropores is further distributed inside the mesopores.

[0009] Furthermore, the manganese nitrate is prepared as a manganese nitrate aqueous solution with a mass concentration of 45-55%, and the dosage ratio of 1H-1,2,3-triazole, manganese nitrate aqueous solution and zinc chloride is 300-400 μL: 200-300 μL: 1-2 g.

[0010] Furthermore, the temperature of the solvent thermal reaction is 80-120° C., and the reaction time is 12-48 hours.

[0011] Furthermore, the primary pyrolysis is carried out by heating the temperature to 400-500°C at a rate of 3-5°C / min, keeping the temperature for 30-40 min, and then heating the temperature to 800-1000°C at the same heating rate, and keeping the temperature for 1-2 h.

[0012] Furthermore, the sulfuric acid treatment is to put the product obtained by the primary pyrolysis into a 0.5-1 mol / L sulfuric acid solution and stir it at 60-80°C for 10-12h, then wash it with ultrapure water, filter it and dry it to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst.

[0013] Furthermore, the secondary pyrolysis is carried out at 800-1000°C in an argon environment, and the pyrolysis time is 1-2h.

[0014] A method for preparing a bimetallic active site doped carbon-based catalyst, characterized in that: 1H-1,2,3-triazole, manganese nitrate and zinc chloride are used as reaction raw materials, and Mn-MET-ZnCl is obtained by solvent thermal reaction and drying. 2The powder was then subjected to primary pyrolysis, sulfuric acid treatment and secondary pyrolysis to obtain the ZnMn-NC catalyst.

[0015] Furthermore, the manganese nitrate is prepared as a manganese nitrate aqueous solution with a mass concentration of 45-55%, and the dosage ratio of 1H-1,2,3-triazole, manganese nitrate aqueous solution and zinc chloride is 300-400 μL: 200-300 μL: 1-2 g.

[0016] Furthermore, the temperature of the solvent thermal reaction is 80-120° C., and the reaction time is 12-48 hours.

[0017] Furthermore, the primary pyrolysis is carried out by heating the temperature to 400-500°C at a rate of 3-5°C / min, keeping the temperature for 30-40 min, and then heating the temperature to 800-1000°C at the same heating rate, and keeping the temperature for 1-2 h.

[0018] The present invention aims to first form a mesoporous structure and then further create micropores in the mesopores to form a nesting doll-like rich pore structure with micropores distributed in the mesopores. Compared with the prior art of replacing micropores with mesopores, it has a better specific surface area and a richer pore structure, thereby achieving a double increase in the adsorption amount of metal ions and the amount of surface exposed active sites.

[0019] However, in the actual preparation process, since a large number of mesoporous structures are prepared first and then micropores are formed in the mesopores, the progress is difficult to control during the pore-making process. The formation of a large number of mesopores and the subsequent further activation and transformation of the mesoporous structure to generate micropores will lead to serious problems of material structure collapse and a sharp drop in catalytic performance.

[0020] In view of this, in the present invention, 1H-1,2,3-triazole, manganese nitrate and excess zinc chloride are reacted by solvent thermal reaction to generate Mn-MET-ZnCl 2Powder, during the pyrolysis process, a staged heating pyrolysis was used in the first pyrolysis process. In the first stage of heating, MET was slowly thermally decomposed at a lower temperature to generate a large number of uniformly distributed mesoporous structures. During this process, zinc chloride gradually formed a molten structure. Then the temperature continued to rise. When the second stage temperature was reached, the molten zinc chloride was fully etched and pore-formed in the metal organic framework material, and a uniformly distributed microporous structure was formed in the mesopores, so that the material obtained a hierarchical pore structure with a high specific surface area. In the pore-forming process of zinc chloride, the metal Zn / Mn that is easy to agglomerate will be anchored in the form of a single atom on the carbon skeleton with nitrogen defect positions, so that the content of Zn / Mn distributed by a single atom is further increased, that is, the high specific surface area and the hierarchical pore structure of micropores distributed in the mesopores allow the material to adsorb more Zn / Mn, while exposing more active sites, enhancing its ORR activity, and at the same time increasing the degree of graphitization of the entire carbon material. The increase in the degree of graphitization not only helps to increase the current density, but also improves the stability of the carbon material. The synergistic effect of the high specific surface area hierarchical pore structure and single atomic sites is beneficial to improving the catalytic activity and battery performance of the catalyst.

[0021] That is, in the present invention, by using 1H-1,2,3-triazole and excess zinc chloride for two-stage pyrolysis regulation, the mesopores are first prepared and then a hierarchical pore structure of micropores is formed in the mesopores, which effectively solves the problem of carbon structure collapse.

[0022] Furthermore, the sulfuric acid treatment is to put the product obtained by the primary pyrolysis into a 0.5-1 mol / L sulfuric acid solution and stir it at 60-80°C for 10-12h, then wash it with ultrapure water, filter it and dry it to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst.

[0023] Furthermore, the secondary pyrolysis is carried out at 800-1000°C in an argon environment, and the pyrolysis time is 1-2h.

[0024] The carbon framework structure is consolidated through secondary pyrolysis, making the carbon structure containing micropores in the mesopores more stable.

[0025] A method for preparing a bimetallic active site doped carbon-based catalyst, characterized in that it comprises the following steps:

[0026] (1) Mix 600-800 µL of 1H-1,2,3-triazole, 400-600 µL of 50% manganese nitrate aqueous solution and 2-4 g of ZnCl 2 Add to 30-70 mL N,N-dimethylformamide and mix thoroughly with ultrasound, then transfer to a constant temperature of 80-120 °C for 12-24 h for solvothermal reaction;

[0027] (2) After the reaction is completed, centrifuge and then place in a constant temperature drying oven at 60-80 °C for drying to obtain Mn-MET-ZnCl 2 powder;

[0028] (3) The Mn-MET-ZnCl 2 The powder is placed in agate and ground evenly, and then pyrolyzed once, specifically, the temperature is raised to 400-500 °C at a rate of 3-5 °C / min, kept at that temperature for 30-40 min, and then raised to 800-1000 °C at the same rate, and kept at that temperature for 1-2 h;

[0029] (4) placing the product after the primary pyrolysis into a 0.5-1 mol / L sulfuric acid solution and stirring at 60-80 °C for 10-12 hours, then washing with ultrapure water, filtering and drying to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst;

[0030] (5) The primary zinc / manganese single atom carbon-based oxygen reduction catalyst is transferred to a tubular furnace filled with argon and subjected to secondary pyrolysis at a temperature of 800-1000°C for 1-2 h to obtain a ZnMn-NC catalyst, which is a bimetallic site-doped carbon-based catalyst.

[0031] The application of the ZnMn-NC catalyst is specifically in the preparation of zinc-air batteries.

[0032] Furthermore, the ZnMn-NC catalyst is used in the preparation of a primary zinc-air battery.

[0033] Furthermore, the ZnMn-NC catalyst is used in the preparation of a rechargeable and dischargeable zinc-air battery.

[0034] In the ZnMn-NC catalyst prepared in the present invention, which has a hierarchical pore structure with abundant mesopores and micropores uniformly distributed in the mesopores, its abundant mesoporous structure plays a role in transferring solutes and oxygen in the battery electrode material, and the micropores distributed inside it effectively anchor more single-atom distributed Zn / Mn, further enhancing its ORR activity, thereby improving the energy density and long-term stability of the battery.

[0035] The present invention has the following technical effects:

[0036] In the present invention, 1H-1,2,3-triazole and zinc chloride are used as pore-forming agents for mesopores and micropores, respectively, and the pore-forming order and pore-forming process are adjusted by pyrolysis to preferentially form a large number of mesopores, and then a large number of micropores are evenly distributed in the mesopores to form a hierarchical pore structure, thereby solving the problem of pore structure collapse faced in forming the structure. The obtained bimetallic site-doped carbon-based catalyst ZnMn-NC has a high specific surface area of ​​1837.9 m² / g and exhibits excellent ORR activity, E 1 / 2 =0.867 V vs. RHE, and the primary zinc-air battery assembled with it as the positive electrode oxygen reduction catalyst has 889 Wh / kg -1 High energy density of Zn. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 : Scanning electron microscope (SEM) image of the ZnMn-NC catalyst prepared in Example 3 of the present invention.

[0038] Figure 2 : Transmission electron microscope (TEM) image of the ZnMn-NC catalyst prepared in Example 3 of the present invention.

[0039] Figure 3 : High-resolution transmission electron microscopy (HR-TEM) image of the ZnMn-NC catalyst prepared in Example 3 of the present invention.

[0040] Figure 4 : Annular dark field scanning projection electron microscopy (HAADF-STEM) image of the ZnMn-NC catalyst prepared in Example 3 of the present invention.

[0041] Figure 5 : X-ray diffraction (XRD) pattern of the ZnMn-NC catalyst prepared in Example 3 of the present invention.

[0042] Figure 6 : N of the ZnMn-NC catalyst prepared in Example 3 of the present invention 2 Adsorption–desorption isotherms (inset shows pore distribution).

[0043] Figure 7 : Comparison chart of oxygen reduction LSV of ZnMn-NC catalyst prepared by the present invention and commercial Pt / C catalyst.

[0044] Figure 8 : LSV comparison diagram of oxygen reduction of ZnMn-NC catalyst prepared by the present invention and Pt / C catalyst.

[0045] Fig. 9 : Comparison of energy density of primary zinc-air batteries assembled with ZnMn-NC catalyst prepared by the present invention and Pt / C catalyst.

[0046] Fig.10 : Long-term constant current density discharge diagram of a primary zinc-air battery assembled with a bimetallic site-doped carbon-based catalyst prepared by the present invention.

[0047] Fig.11 : Comparison chart of charge / discharge cycle test of rechargeable zinc-air battery assembled with ZnMn-NC catalyst prepared by the present invention and commercial Pt / C catalyst. DETAILED DESCRIPTION

[0048] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0049] Example 1

[0050] A method for preparing a bimetallic active site doped carbon-based catalyst comprises the following steps:

[0051] (1) Mix 600 μL of 1H-1,2,3-triazole, 600 μL of 50% manganese nitrate aqueous solution and 2 g of ZnCl 2 The mixture was added into 30 mL of N,N-dimethylformamide and mixed by ultrasound, and then transferred to a constant temperature of 100 °C for 18 h of solvothermal reaction.

[0052] (2) After the reaction, the mixture was centrifuged and then placed in a constant temperature drying oven at 70 °C for drying to obtain Mn-MET-ZnCl 2 powder;

[0053] (3) The Mn-MET-ZnCl 2 The powder was placed in agate and ground evenly, and then pyrolyzed once, specifically, the temperature was raised to 400 °C at a rate of 4 °C / min, kept at that temperature for 40 min, and then raised to 1000 °C at the same rate and kept at that temperature for 1.5 h;

[0054] (4) The product after the primary pyrolysis was placed in a 0.8 mol / L sulfuric acid solution and stirred at 70 °C for 12 h, then washed with ultrapure water, filtered and dried to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst;

[0055] (5) The primary zinc / manganese single atom carbon-based oxygen reduction catalyst was transferred to a tubular furnace filled with argon and subjected to secondary pyrolysis at 1000°C for 1 h to obtain a ZnMn-NC catalyst, which is a bimetallic site-doped carbon-based catalyst.

[0056] Example 2

[0057] A method for preparing a bimetallic active site doped carbon-based catalyst comprises the following steps:

[0058] (1) Mix 800 μL of 1H-1,2,3-triazole, 400 μL of 50% manganese nitrate aqueous solution and 4 g of ZnCl 2 The mixture was added into 70 mL of N,N-dimethylformamide and mixed by ultrasound, and then transferred to a constant temperature of 80 °C for 12 h of solvothermal reaction.

[0059] (2) After the reaction, the mixture was centrifuged and then placed in a constant temperature drying oven at 80 °C for drying to obtain Mn-MET-ZnCl 2 powder;

[0060] (3) The Mn-MET-ZnCl 2 The powder was ground evenly in agate and then pyrolyzed once, specifically by heating to 400 °C at a rate of 3 °C / min, keeping the temperature for 40 min, and then heating to 1000 °C at the same rate and keeping the temperature for 1 h.

[0061] (4) The product after the primary pyrolysis was placed in a 1 mol / L sulfuric acid solution and stirred at 60 °C for 10 h, then washed with ultrapure water, filtered and dried to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst;

[0062] (5) The primary zinc / manganese single atom carbon-based oxygen reduction catalyst was transferred to a tubular furnace filled with argon and subjected to secondary pyrolysis at 800 °C for 2 h to obtain a ZnMn-NC catalyst, which is a bimetallic site-doped carbon-based catalyst.

[0063] The bimetallic site-doped carbon-based catalyst ZnMn-NC prepared in this example has a high specific surface area of ​​1829.8 m² / g. x The content of active sites is 21.35%, showing excellent ORR activity, E 1 / 2 = 0.864 Vvs. RHE.

[0064] Example 3

[0065] A method for preparing a bimetallic active site doped carbon-based catalyst comprises the following steps:

[0066] (1) Mix 740 μL of 1H-1,2,3-triazole, 585 μL of 50% manganese nitrate aqueous solution and 3.4 g of ZnCl 2The mixture was added into 50 mL of N,N-dimethylformamide and mixed by ultrasound, and then transferred to a constant temperature of 120 °C for 24 h of solvothermal reaction.

[0067] (2) After the reaction, the mixture was centrifuged and then placed in a constant temperature drying oven at 60 °C for drying to obtain Mn-MET-ZnCl 2 powder;

[0068] (3) The Mn-MET-ZnCl 2 The powder was placed in agate and ground evenly, and then pyrolyzed once, specifically, the temperature was raised to 450 °C at a rate of 5 °C / min, kept at that temperature for 35 min, and then raised to 900 °C at the same rate and kept at that temperature for 2 h;

[0069] (4) The product after the primary pyrolysis was placed in a 0.5 mol / L sulfuric acid solution and stirred at 80 °C for 12 h, then washed with ultrapure water, filtered and dried to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst;

[0070] (5) The primary zinc / manganese single atom carbon-based oxygen reduction catalyst was transferred to a tubular furnace filled with argon and subjected to secondary pyrolysis at 900 °C for 1 h to obtain a ZnMn-NC catalyst, which is a bimetallic site-doped carbon-based catalyst.

[0071] The bimetallic site-doped carbon-based catalyst ZnMn-NC prepared in this example has a high specific surface area of ​​1830.1 m² / g. x The content of active sites is 22.16%, showing excellent ORR activity, E 1 / 2 = 0.870 Vvs. RHE.

[0072] The scanning electron microscope (SEM) image of the ZnMn-NC catalyst prepared in Example 3 is as follows: Figure 1 As shown in the figure, it can be seen that the ZnMn-NC catalyst prepared in this embodiment presents a three-dimensional morphology with a rich porous structure. It has a rich mesoporous structure, and a large number of micropores are formed inside the mesopores. This is due to the organic ligands of the metal organic framework material formed by 1H-1,2,3-triazole, which first decomposes to form a mesoporous structure during the first pyrolysis, and the excess ZnCl 2 The microporous structure can be obtained by synergistically providing pore-forming ability in a molten state at a relatively high temperature, thereby realizing a hierarchical pore structure in which mesopores are formed first and then micropores are formed in the mesopores. Figure 2 This is a transmission electron microscope (TEM) image of the ZnMn-NC catalyst prepared in this example, from which it can be seen that a three-dimensional porous structure is formed.

[0073] Figure 3 This is a high-resolution transmission electron microscopy (HR-TEM) image of the ZnMn-NC catalyst prepared in this example. The irregular lattice fringes indicate that the carbon matrix has amorphous properties. The selected area electron diffraction pattern in the inset also proves that there are no crystals in the entire carbon matrix, which indicates that the metal Zn / Mn is successfully embedded in the carbon matrix in the form of single atoms.

[0074] Figure 4 This is the aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the ZnMn-NC catalyst prepared in this example. The single bright spot directly proves the dispersion of Zn / Mn atoms, demonstrating that the synthesized ZnMn-NC catalyst has abundant and uniformly dispersed single-atom Zn / Mn sites.

[0075] like Figure 5 As shown, the X-ray diffraction pattern (XRD) of the ZnMn-NC catalyst prepared in this example shows that it does not have a crystalline metal structure.

[0076] To analyze transition metal Zn / Mn-N x The content of active sites was tested by X-ray photoelectron spectroscopy (XPS). Figure 6 As shown, Zn / Mn-N x The content of active sites is as high as 21.83%. The presence of high content of active sites indicates that the endogenous doping of excessive ZnCl 2 Not only is pore creation achieved inside the metal-organic framework material, but the easily agglomerated metal Mn / Zn is also successfully anchored in the form of single atoms on the defective carbon skeleton.

[0077] like Figure 7 As shown in Figure 2, the ZnMn-NC catalyst prepared in this example exhibits a typical type IV nitrogen adsorption-desorption isotherm. The pore size distribution shows that the ZnMn-NC catalyst has a multi-level pore structure dominated by mesopores, and its specific surface area is as high as 1837.9 m 2 g -1 , which contains a hierarchical porous structure with a large number of micropores, which can accelerate electron transfer and material transfer.

[0078] like Figure 8 The LSV curve shown in the figure shows the excellent electrochemical performance of the catalyst. It can be seen from the figure that the ZnMn-NC catalyst prepared in Example 3 shows a better electrochemical performance than Pt / C (E 1 / 2 = 0.86 V vs. RHE, J L = 5.81 mA cm -2 ) has better ORR activity (E 1 / 2 = 0.867 V vs. RHE, J L = 5.9 mA cm -2 ).

[0079] Comparative Example 1

[0080] Compared with Example 3, the temperature was directly raised to 900° C. at the same rate and kept at that temperature for 2 h during the first pyrolysis process; the remaining steps were the same as those in Example 3.

[0081] Since the temperature was directly raised to a high temperature of 900 °C during the first pyrolysis process, the decomposition of MET gradually intensified with the increase of temperature, resulting in a large number of mesopores with poor stability during the formation of mesopores. When excessive zinc chloride was used to form micropores during the subsequent heat preservation process, a large number of mesopores collapsed, resulting in the lack of abundant mesopores in the carbon material. The hierarchical pore structure of micropores with uniform internal distribution significantly reduced the specific surface area. After testing, its BET specific surface area was 844.7 m 2 g -1 , Zn / Mn-N x The content of active sites is 9.16%.

[0082] Example 4

[0083] Application of bimetallic site doped carbon-based catalyst (ZnMn-NC) in the preparation of primary zinc-air batteries and rechargeable zinc-air batteries:

[0084] 2 mg of the ZnMn-NC catalyst prepared in Example 3 was weighed and uniformly dispersed in a mixed solution consisting of 195 μL of ethanol and 5 μL of naphthol, and then evenly coated on a 4 cm 2 Carbon cloth was used as the positive electrode oxygen reduction catalyst, a Zn sheet with a thickness of 0.2 mm was selected as the negative electrode, and a 6 mol / L KOH solution was used as the electrolyte to assemble a primary zinc-air battery.

[0085] Control group: The ZnMn-NC catalyst prepared in Example 3 was replaced with a commercially available Pt / C catalyst, and a primary zinc-air battery was assembled and prepared in the same manner.

[0086] Fig. 9 This is a comparison of the energy density of a primary zinc-air battery assembled with the ZnMn-NC catalyst prepared in Example 3 and the commercial Pt / C catalyst; as can be seen from the figure, at a fixed current density of 50 mA / cm 2 When discharged at low temperatures, the primary zinc-air battery assembled with Mn-N@8Gra-L catalyst has a capacity of 889 Wh / kg -1 The high energy density of Zn far exceeds the energy density of a primary zinc-air battery assembled with Pt / C (763 Wh / kg -1 Zn).

[0087] Fig.10 The primary zinc-air battery prepared in Example 4 was subjected to a fixed current density of 50 mA / cm 2 As shown in the figure, after a 150-h constant current density discharge, the discharge voltage of the assembled zinc-air battery only decreased by 49 mV.

[0088] Example 5

[0089] Application of bimetallic site doped carbon-based catalyst (ZnMn-NC) in the preparation of rechargeable and dischargeable zinc-air batteries:

[0090] Weigh 2 mg of ZnMn-NC catalyst prepared in Example 3 and 2 mg of RuO 2 The mixture was evenly dispersed in a mixed solution of 390 μL ethanol and 10 μL naphthol, and then evenly coated on a 4 cm 2 Carbon cloth was used as the positive electrode oxygen reduction catalyst, and a Zn sheet with a thickness of 0.2 mm was selected as the negative electrode. KOH and Zn(Ac) 2 The mixed solution is used as the electrolyte to assemble a rechargeable zinc-air battery; the concentration of KOH is 6 mol / L, Zn(Ac) 2 The concentration is 0.2 mol / L.

[0091] Control group: A commercial Pt / C catalyst was used instead of the ZnMn-NC catalyst prepared in Example 3, and a rechargeable zinc-air battery was prepared in the same manner as above for comparison.

[0092] like Fig.11 As shown, in Example 5, the ZnMn-NC catalyst and RuO 2 The assembled rechargeable zinc-air battery has a discharge voltage of 1.1664 V and a charge voltage of 2.0271 V during the charge and discharge process of more than 100 hours, with a charge and discharge voltage difference of 86.1 mV. 2 The assembled rechargeable zinc-air battery has a large charge-discharge voltage difference (90 mV), indicating that the ZnMn-NC catalyst has better long-term cycle stability than the Pt / C catalyst when used in rechargeable zinc-air batteries.

Claims

1. A method for preparing a bimetallic active site doped carbon-based catalyst, characterized in that: The method uses 1H-1,2,3-triazole, manganese nitrate and zinc chloride as reaction raw materials, obtains Mn-MET-ZnCl2 powder through solvent thermal reaction and drying, and then obtains bimetallic active site doped carbon-based catalyst ZnMn-NC through primary pyrolysis, sulfuric acid treatment and secondary pyrolysis in sequence. The primary pyrolysis is heated to 400-500°C at a rate of 3-5°C / min, kept warm for 30-40 min, and then heated to 800-1000°C at the same heating rate and kept warm for 1-2 h.

2. The method for preparing a bimetallic active site doped carbon-based catalyst according to claim 1, characterized in that: The manganese nitrate is prepared as a manganese nitrate aqueous solution with a mass concentration of 45-55%, and the dosage ratio of 1H-1,2,3-triazole, manganese nitrate aqueous solution and zinc chloride is 300-400 μL: 200-300 μL: 1-2 g.

3. A method for preparing a bimetallic active site doped carbon-based catalyst as claimed in claim 1 or 2, characterized in that: The temperature of the solvent thermal reaction is 80-120° C., and the reaction time is 12-48 hours.

4. The method for preparing a bimetallic active site doped carbon-based catalyst according to claim 3, characterized in that: The sulfuric acid treatment is to put the product obtained by the primary pyrolysis into a 0.5-1 mol / L sulfuric acid solution, and stir it at 60-80°C for 10-12h, and then wash it with ultrapure water, filter it, and dry it to obtain a primary zinc / manganese single atom carbon-based oxygen reduction catalyst.

5. The method for preparing a bimetallic active site doped carbon-based catalyst according to claim 4, characterized in that: The secondary pyrolysis is carried out in an argon environment at 800-1000°C, and the pyrolysis time is 1-2 h.

6. A bimetallic active site doped carbon-based catalyst prepared by the method of claim 5, characterized in that: The ZnMn-NC catalyst has a mesopore distribution inside, and a hierarchical pore structure of micropores is further distributed inside the mesopores.

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