Metallic single-atom doped nanocarbon material catalyst, and preparation method and application thereof

Abstract

The present application relates to the technical field of oxygen reduction catalyst, in particular to a kind of metal single-atom doped nanocarbon material catalyst and its preparation method and application.In the present application, nitrogen-containing ligand is first coordinated with metal salt to form M-N bonding complex, which can improve the proportion of effective M-N active sites, and then the graphdiyne is mixed with M-N complex, which can limit the complex in molecular pores, so that the metal atom is atomically dispersed, and finally a single-atom doped graphdiyne-based oxygen reduction catalyst material is obtained.

Description

Technical Field

[0001] This invention relates to the field of oxygen reduction catalyst technology, specifically to a metal single-atom doped nanocarbon material catalyst, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Currently, fossil fuels, primarily coal, oil, and natural gas, remain the main energy sources consumed by humankind. The shortage of fossil fuels and the resulting global warming and climate change are attracting widespread attention. Therefore, researching and developing sustainable clean energy storage and conversion technologies has become crucial for the world today. Converting chemical energy into electrical energy through electrochemical oxidation and reduction methods, and storing it in the form of batteries, is a more feasible and economical approach. High-capacity energy conversion systems, such as zinc-air batteries and fuel cells, have garnered significant attention due to their low or even zero emissions and high efficiency. The oxygen reduction reaction (ORR) is a crucial cathode reaction in fuel cell devices and is key to the realization of such devices. However, the excessively high reaction potential and short catalyst lifetime have consistently hampered research on the ORR. Currently, there are two main types of ORR catalysts: platinum group metal (PGM) catalysts and non-platinum group catalysts (mainly transition metals and nitrogen-doped carbon materials). However, platinum group materials have drawbacks such as rarity, high cost, poor stability, and susceptibility to poisoning, which has accelerated the search for non-platinum group catalysts. Currently, common non-platinum group catalysts include transition metal oxides, carbon-based materials, and transition metal macrocyclic compounds. Developing high-performance, low-cost non-platinum group catalysts has become one of the main research directions for oxygen reduction reactions.

[0004] In recent years, single-atom catalysts, as an emerging field of heterogeneous catalysis, have attracted widespread attention due to their high atom utilization and catalytic activity comparable to noble metal catalysts. Among them, the metal-nitrogen-carbon (MNC) structure utilizes nitrogen to anchor dispersed metal atoms, thereby forming single-atom sites. This type of site often exhibits excellent catalytic activity. However, generally, MNC catalysts are mostly made by combining metal salts with carbon materials and then doping them with nitrogen atoms. In this case, the coordination between metal atoms and nitrogen is less, resulting in a lower proportion of effective MN active sites, which affects the final catalyst performance. Summary of the Invention

[0005] To overcome the above problems, this invention provides a metal single-atom doped nanocarbon material catalyst, its preparation method, and its application. In this invention, a nitrogen-containing ligand is first coordinated with a metal salt to form an MN-bonded complex, which increases the proportion of effective MN active sites. Then, graphyne is mixed with the MN complex, which confines the complex within the molecular pores, thereby achieving atomic-level dispersion of the metal atoms. Therefore, a single-atom doped graphyne-based oxygen reduction catalyst material is finally obtained.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a metal single-atom-doped nanocarbon material catalyst, comprising:

[0008] Nitrogen-containing ligands and metal salts were added to solvent A and stirred to form a complex MN. Nanocarbon materials and complex MN were dispersed in solvent B and stirred for pre-adsorption. After the reaction was completed, solvent B was removed to obtain a catalyst precursor. The catalyst precursor was first heated to 600-750℃ in an inert gas atmosphere, and then calcined to 850-950℃ in a nitrogen atmosphere to obtain a metal single-atom doped nanocarbon material catalyst.

[0009] The nano-carbon material is nano-graphyne (GDY) or nano-hydrogen-substituted graphyne (HsGDY).

[0010] In a second aspect, the present invention provides a metal single-atom doped nanocarbon material catalyst prepared by the above-described preparation method.

[0011] A third aspect of the present invention provides the application of the above-mentioned metal single-atom doped nanocarbon material catalyst as an oxygen reduction working electrode catalyst or an air electrode catalyst in a zinc-air fuel cell, a hydrogen-oxygen fuel cell, a magnesium-air fuel cell, or an aluminum-air fuel cell.

[0012] The beneficial effects of this invention are as follows:

[0013] (1) In this invention, nitrogen-containing ligands are first coordinated with metal salts to form MN-bonded complexes, which can increase the proportion of effective MN active sites. However, the MN complexes are relatively large in size and difficult to disperse in traditional carbon materials. Therefore, they tend to agglomerate during high-temperature annealing, which is not conducive to the formation of high-density atomic-level active sites. Graphdiyne is rich in sp and sp 2 Graphdiyne, a two-dimensional network of carbon allotropes, possesses large and tunable molecular pores. Mixing graphdiyne with an MN complex confines the complex within the molecular pores, resulting in atomic-level dispersion of metal atoms. This ultimately yields a single-atom-doped graphdiyne-based oxygen reduction catalyst.

[0014] (2) First, the nitrogen-containing ligand is coordinated with the metal salt to form an MN bonded complex. This can change the ratio of the central atom to the coordinating atoms and also conveniently adjust the number of coordinating atoms in the final reaction site, thereby controlling the electronic structure of the transition metal atoms in the catalyst product and obtaining an electrocatalyst material with excellent performance.

[0015] (3) Compared with the MNC catalyst formed by combining metal salts with carbon materials and then doping with N atoms, the single-atom doped graphene-based oxygen reduction catalyst material in this invention has a higher number of MN active sites, thus exhibiting good catalytic activity. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 These are SEM and TEM images of graphyne; where a is the SEM image and b is the TEM image.

[0018] Figure 2 The images show SEM and TEM images of the single-atom doped graphitic ytylene oxide reduction catalyst Zn-N-GDY synthesized in Example 1; where a is an SEM image and b is a TEM image.

[0019] Figure 3 The results of oxygen reduction activity detection are for the catalysts prepared in Example 1 and Comparative Examples 1-2 in Experimental Example 1.

[0020] Figure 4 The results of the antitoxicity test for Zn-N-GDY prepared in Example 1;

[0021] Figure 5 ORR polarization curves of Zn-N-GDY prepared in Example 1 before and after 5000 CV cycles;

[0022] Figure 6 In Example 1, a represents the LSV curves of Zn-N-GDY prepared at different rotation speeds, b represents the yield of H2O2 during catalysis, and c represents the corresponding number of electrons transferred during catalysis. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

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

[0025] A first typical embodiment of the present invention provides a method for preparing a metal single-atom-doped nanocarbon material catalyst, comprising:

[0026] Nitrogen-containing ligands and metal salts were added to solvent A and stirred to form a complex MN. Nanocarbon materials and complex MN were dispersed in solvent B and stirred for pre-adsorption. After the reaction was completed, solvent B was removed to obtain a catalyst precursor. The catalyst precursor was first heated to 600-750℃ in an inert gas atmosphere, and then calcined to 850-950℃ in a nitrogen atmosphere to obtain a metal single-atom doped nanocarbon material catalyst.

[0027] The nano-carbon material is nano-graphyne (GDY) or nano-hydrogen-substituted graphyne (HsGDY).

[0028] In one or more embodiments, the metal salt is preferably one of anhydrous ZnCl2, anhydrous FeCl3, or copper acetylacetonate.

[0029] In one or more embodiments, the nitrogen-containing ligand is preferably one of pyrazole-3-carboxylic acid, urea, cyanamide, dicyandiamide, or 2,2-bipyridine.

[0030] In one or more embodiments, the molar ratio of the metal salt to the nitrogen-containing ligand is 1:1 to 1:100, preferably 1:10.

[0031] In one or more embodiments, the stirring reaction takes 20 to 30 hours to form the complex MN.

[0032] In one or more embodiments, solvent A is preferably ethanol or deionized water, and solvent B is preferably an ethanol solution with a volume concentration of 20% to 100%, with the preferred ethanol solution being a mixed solution of ethanol and deionized water.

[0033] In one or more embodiments, the molar ratio of the metal salt to graphyne or hydrogen-substituted graphyne is 0.1% to 10%, preferably 1% to 2.5%.

[0034] In one or more embodiments, the pre-adsorption time for stirring is 20 to 30 hours.

[0035] In one or more embodiments, the calcination time is 0.5 to 2 hours, preferably 0.5 hours.

[0036] In one or more embodiments, during calcination, the heating rate is 1 to 10 °C / min, more preferably 5 °C / min.

[0037] A second typical embodiment of the present invention provides a metal single-atom doped nanocarbon material catalyst prepared by the above preparation method.

[0038] A third typical embodiment of the present invention provides the application of the above-mentioned metal single-atom doped nano-carbon material catalyst as an oxygen reduction working electrode catalyst or an air electrode catalyst in zinc-air fuel cells, hydrogen-oxygen fuel cells, magnesium-air fuel cells or aluminum-air fuel cells.

[0039] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0040] Graphdiyne and hydrogen-substituted graphdiyne were synthesized via a cross-coupling reaction using copper foil as a substrate. The synthesized graphdiyne was then peeled off from the copper foil to obtain powder samples. The morphology of the synthesized graphdiyne was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are as follows: Figure 1 As stated, from Figure 1 As can be seen, both the internal and external morphology of GDY are porous network structures.

[0041] Example 1

[0042] 2 mg of anhydrous ZnCl2 and 4 mg of cyanamide were dissolved in 10 mL of ethanol and stirred for 24 h to obtain a Zn-N complex. 10 mg of GDY was dissolved in ethanol, ultrasonically dispersed for 0.5 h, and then the Zn-N complex was added. Stirring continued for 24 h. The mixture was filtered with 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The catalyst precursor was transferred to a quartz boat and placed in a tubular furnace. After evacuating to a vacuum using a vacuum pump, argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 650 °C in an argon atmosphere. At this point, the argon gas was stopped, and NH3 was introduced to remove the argon gas. The furnace was heated to 900 °C in an NH3 atmosphere and pyrolyzed for 0.5 h, then cooled to room temperature to obtain the single-atom doped graphene oxy-acetylene reduction catalyst Zn-N-GDY. The morphology of the synthesized single-atom doped graphene oxy-acetylene reduction catalyst Zn-N-GDY was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are as follows. Figure 2 As stated, from Figure 2 It can be seen that the structure of GDY is maintained during the high-temperature calcination process.

[0043] Example 2

[0044] 2 mg of anhydrous ZnCl2 and 2 mg of 2,2-bipyridine were dissolved in 10 mL of ethanol and stirred for 24 h to obtain a Zn-N complex. 10 mg of HsGDY was dissolved in 50% ethanol and ultrasonically dispersed for 0.5 h. The Zn-N complex was then added, and stirring continued for 24 h. The mixture was filtered through 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The powder was transferred to a quartz boat and placed in a tubular furnace. After evacuating to a vacuum using a vacuum pump, argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 650 °C in an argon atmosphere. At this point, the argon gas supply was stopped, and NH3 was introduced to remove the argon gas. The furnace was then heated to 900 °C in an NH3 atmosphere and pyrolyzed for 0.5 h before cooling to room temperature to obtain the single-atom doped graphitic ytylene-oxygen reduction catalyst Zn-N-HsGDY.

[0045] Example 3

[0046] 1.5 mg of anhydrous FeCl3 and 2 mg of pyrazole-3-carboxylic acid were dissolved in 10 mL of ethanol and stirred for 24 h to obtain the Fe-N complex. 10 mg of GDY was dissolved in ethanol, ultrasonically dispersed for 0.5 h, and then the Fe-N complex was added, with stirring continued for 24 h. The mixture was filtered through 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The catalyst precursor was transferred to a quartz boat, placed in a tubular furnace, and evacuated using a vacuum pump. Argon gas was then introduced, repeated three times to ensure the removal of O2. The mixture was heated to 600 °C in an argon atmosphere. At this point, the argon gas supply was stopped, and NH3 was introduced to remove the argon gas. The mixture was then heated to 850 °C in an NH3 atmosphere and pyrolyzed for 0.5 h before cooling to room temperature to obtain the single-atom doped graphitic ytylene-oxygen reduction catalyst Fe-N-GDY.

[0047] Example 4

[0048] 1.5 mg of anhydrous FeCl3 and 2 mg of dicyandiamide were dissolved in 10 mL of ethanol and stirred for 24 h to obtain the Fe-N complex. 10 mg of GDY was dissolved in ethanol, ultrasonically dispersed for 0.5 h, and then the Fe-N complex was added. Stirring continued for 24 h. The mixture was filtered using 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The catalyst precursor was transferred to a quartz boat and placed in a tubular furnace. After evacuating to a vacuum using a vacuum pump, argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 750 °C in an argon atmosphere. At this point, the argon gas supply was stopped, and NH3 was introduced to remove the argon gas. The furnace was then heated to 950 °C in an NH3 atmosphere and pyrolyzed for 0.5 h before cooling to room temperature to obtain the single-atom doped graphitic acetylene-oxygen reduction catalyst Fe-N-GDY.

[0049] Example 5

[0050] 1.2 mg of copper acetylacetonate and 4 mg of 2,2-bipyridine were dissolved in 10 mL of deionized water and stirred for 24 h to obtain a Cu-N complex. 10 mg of HsGDY was dissolved in 80% ethanol (v / v), ultrasonically dispersed for 0.5 h, and then the Cu-N complex was added. Stirring continued for 24 h. The mixture was filtered through 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The catalyst precursor was transferred to a quartz boat and placed in a tubular furnace. After evacuating to a vacuum using a vacuum pump, argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 750 °C in an argon atmosphere. At this point, the argon gas supply was stopped, and NH3 was introduced to remove the argon gas. The furnace was then heated to 900 °C in an NH3 atmosphere and pyrolyzed for 0.5 h before cooling to room temperature to obtain the single-atom doped graphitic ytylene-oxygen reduction catalyst Cu-N-HsGDY.

[0051] Example 6

[0052] 2 mg of copper acetylacetonate and 4 mg of urea were dissolved in 10 mL of deionized water and stirred for 24 h to obtain a Cu-N complex. 10 mg of GDY was dissolved in ethanol, ultrasonically dispersed for 0.5 h, and then the Cu-N complex was added. Stirring continued for 24 h. The mixture was filtered using 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The catalyst precursor was transferred to a quartz boat and placed in a tubular furnace. After evacuating to a vacuum using a vacuum pump, argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 750 °C in an argon atmosphere. At this point, the argon gas supply was stopped, and NH3 was introduced to remove the argon gas. The furnace was then heated to 900 °C in an NH3 atmosphere and pyrolyzed for 0.5 h before cooling to room temperature to obtain the single-atom doped graphitic ytylene-oxygen reduction catalyst Cu-N-GDY.

[0053] Comparative Example 1

[0054] 2 mg of anhydrous ZnCl2 and 10 mg of GDY were dissolved in 10 mL of ethanol and stirred for 24 h to obtain Zn-GDY. The mixture was filtered through 500 mL of deionized water, and the ethanol was evaporated at 85 °C to obtain the catalyst precursor. The catalyst precursor was transferred to a quartz boat and placed in a tubular furnace. A vacuum was created using a vacuum pump, and argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 650 °C in an argon atmosphere. The argon gas flow was then stopped, and NH3 was introduced to remove the argon gas. The furnace was then heated to 900 °C in an NH3 atmosphere and pyrolyzed for 0.5 h before cooling to room temperature to obtain the single-atom doped graphitic acetylene-oxygen reduction catalyst Zn-NO-GDY.

[0055] Comparative Example 2

[0056] 10 mg of GDY was transferred to a quartz boat and placed in a tubular furnace. A vacuum was created using a vacuum pump, and argon gas was introduced, repeated three times to ensure the removal of O2. The furnace was heated to 650 °C in an argon atmosphere. At this point, the argon gas supply was stopped, and NH3 was introduced to purge the argon gas. The furnace was then heated to 900 °C in an NH3 atmosphere and pyrolyzed for 0.5 h. After cooling to room temperature, nitrogen-doped graphdiyne-oxygen reduction catalyst NO-GDY was obtained.

[0057] Experimental Example 1

[0058] The oxygen reduction activity of the catalysts prepared in Example 1 and Comparative Examples 1-2 was tested using a rotating disk electrode in a 0.1 M KOH electrolyte. The rotation speed was kept constant at 1600 rpm, and the loading was 0.4 mg cm⁻¹. -2 The scanning speed is 5 mV / s. -1 The polarization curves of the catalyst were obtained under the specified conditions. The results are as follows: Figure 3 As shown, metal-free N-doped graphyne has extremely low oxygen reduction performance. Transition metals are directly adsorbed onto graphyne without pre-coordination and then doped with N atoms, which improves the performance but still does not achieve ideal catalytic performance. In contrast, the single-atom Zn-N-GDY formed by pre-coordinating metals with ligands and then dispersing them into graphyne has excellent oxygen reduction activity.

[0059] Experiment Example 2

[0060] The Zn-N-GDY prepared in Example 1 was subjected to an antitoxicity test. The results are as follows: Figure 4 As shown. From Figure 4 As can be seen, the LSV curve of Zn-N-GDY changes very little before and after the addition of methanol, indicating that Zn-N-GDY has excellent methanol resistance.

[0061] In an O2-saturated electrolyte, a potential range including the oxygen reduction peak was continuously scanned for 5000 CV cycles. The LSV curves before and after the cycles were then compared. The results are as follows: Figure 5 The results showed that the LSV curve did not change significantly, indicating that the Zn-N-GDY prepared in Example 1 had good stability.

[0062] Experimental Example 3

[0063] The oxygen reduction reaction (ORR) involves multiple free radicals and intermediates and is kinetically slow. There are two pathways for ORR: the 2-electron pathway and the 4-electron pathway. Compared to the 2-electron pathway, the 4-electron pathway offers advantages such as providing a higher electromotive force and producing less H₂O₂ that undergoes a Fenton-like reaction with transition metals. Considering cost and battery efficiency, complete conversion of O₂ to H₂O is ideal, therefore, a 4-electron pathway ORR catalyst is preferred. Based on the LSV curve data of the tested catalyst at different rotational speeds, the number of transferred electrons in the Zn-N-GDY prepared in Example 1 can be calculated using the KL equation to be approximately 3.8–3.9, indicating that the ORR reaction indeed proceeds via the 4-electron pathway.

[0064] Figure 6 In Example 1, a represents the LSV curves of Zn-N-GDY prepared at different rotation speeds, b represents the yield of H2O2 during catalysis, and c represents the corresponding number of electrons transferred during catalysis.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a metal single-atom-doped nanocarbon material catalyst, characterized in that, include: Nitrogen-containing ligands and metal salts are added to solvent A, and the mixture is stirred to form a complex MN. The nano-carbon material and the complex MN were dispersed in solvent B and stirred for pre-adsorption. After the reaction was completed, solvent B was removed to obtain the catalyst precursor. The catalyst precursor was first heated to 600-750 °C in an inert gas atmosphere, and then calcined to 850-950 °C in an ammonia atmosphere to obtain a metal single-atom doped nano-carbon material catalyst. The nano-carbon material is nano-graphyne; The metal salt is one of anhydrous ZnCl2, anhydrous FeCl3, or copper acetylacetonate. The nitrogen-containing ligand is one of pyrazole-3-carboxylic acid, urea, cyanamide, dicyandiamide, or 2,2-bipyridine; The molar ratio of metal salt to nitrogen-containing ligand is 1:1 to 1:100; When graphyne is mixed with MN complex, the complex is confined within the molecular pore.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the metal salt to the nitrogen-containing ligand is 1:

10.

3. The preparation method according to claim 1, characterized in that, The time for the stirring reaction to form the complex MN is 20-30 hours.

4. The preparation method according to claim 1, characterized in that, Solvent A is ethanol or deionized water, and solvent B is an ethanol solution with a volume concentration of 20% to 100%.

5. The preparation method according to claim 4, characterized in that, An ethanol solution is a mixture of ethanol and deionized water.

6. The preparation method according to claim 1, characterized in that, The pre-adsorption time for stirring is 20-30 h.

7. The preparation method according to claim 1, characterized in that, The calcination time is 0.5~2 h.

8. The preparation method according to claim 7, characterized in that, The calcination time is 0.5 h.

9. The preparation method according to claim 1, characterized in that, During calcination, the heating rate is 1~10 ℃ / min.

10. The preparation method according to claim 9, characterized in that, During calcination, the heating rate is 5 ℃ / min.

11. A metal single-atom doped nanocarbon material catalyst prepared by the preparation method according to any one of claims 1 to 10.

12. The application of the metal single-atom doped nanocarbon material catalyst of claim 11 in zinc-air fuel cells, hydrogen-oxygen fuel cells, magnesium-air fuel cells or aluminum-air fuel cells.

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