Co-N / Co-C catalyst prepared by degrading PET (Polyethylene Terephthalate) as well as preparation method and application of Co-N / Co-C catalyst

Abstract

The invention provides a Co-N / Co-C catalyst prepared by degrading plastic PET (Polyethylene Terephthalate) as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) degrading PET to obtain a terephthalic acid ligand; (2) dissolving the phthalic acid ligand and CoCl2. 6H2O in a solvent, and carrying out solvothermal reaction, so as to obtain a precursor Co-MOFs; and (3) mixing the precursor Co-MOFs with melamine, and carrying out pyrolysis carbonization in a protective atmosphere to obtain the Co-N / Co-C catalyst. The method comprises the following steps: degrading waste plastic PET to obtain a ligand BDC, coordinating with Co metal salt, and calcining with MEL to obtain the N-doped carbon-based composite material. The Co-based catalyst and the zinc-air battery can degrade PET, so that environmental pollution is reduced, contribution is made to green chemistry, and further commercialized and large-scale application of the Co-based catalyst and the zinc-air battery is promoted.

Description

A Co-N / Co@C catalyst prepared by PET degradation, its preparation method, and its applications. Technical Field

[0001] This invention relates to the field of catalyst materials technology, and in particular to a Co-N / Co@C catalyst prepared by degrading PET, its preparation method, and its application. Background Technology

[0002] The oxygen reduction reaction (ORR) is a crucial reaction in the discharge process of zinc-air batteries. Currently, noble metal-based catalysts have demonstrated excellent ORR catalytic activity and applicability. However, the scarcity and high cost of noble metals greatly limit the further commercialization of zinc-air batteries.

[0003] Transition metal-nitrogen-carbon (MNC) catalysts are considered the most promising alternatives to noble metal-based catalysts due to their excellent ORR catalytic activity, tunable electronic structure, highly exposed active sites, and efficient O2 adsorption capacity. Among them, Co-based catalysts exhibit superior intrinsic ORR catalytic activity. However, these single-atom ORR catalysts require precise atomic control, experimental manipulation, and structural design, which significantly hinders their economic viability, scalability, and versatility in other energy conversion and storage applications.

[0004] Furthermore, some plastics can be made from polyethylene terephthalate (PET), which is difficult to biodegrade, taking approximately 500 years to degrade naturally. Statistics show that with the development of human society and production needs, the amount of discarded plastic waste increases year by year, and the situation is becoming increasingly serious in my country. A large amount of plastic waste urgently needs to be disposed of effectively, reasonably, and greenly. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a Co-N / Co@C catalyst, its preparation method, and its application, to solve the problems of the difficulty in large-scale quantitative preparation of existing MNC single-atom catalysts and the green chemistry and environmental friendliness of waste plastic degradation and reuse.

[0006] To achieve the above and other related objectives, this invention provides a method for preparing a Co-N / Co@C catalyst, comprising the following steps:

[0007] (1) Degradation of PET yields terephthalic acid (BDC) ligands;

[0008] (2) The phthalic acid ligand and CoCl2·6H2O were dissolved in a solvent and subjected to a solvothermal reaction to obtain the precursor Co-MOFs;

[0009] (3) The precursor Co-MOFs are mixed with melamine (MEL) and pyrolyzed under a protective atmosphere to obtain the Co-N / Co@C catalyst.

[0010] This invention synthesizes MOF materials by degrading waste plastics to obtain ligands, which are then coordinated with Co metal salts. These MOF materials are then pyrolyzed and carbonized with MEL to obtain a carbon-based composite material containing Co nanoparticles and N doping. This composite material serves as a catalyst for waste recycling, simplifying the original degradation process and allowing for the recovery and reuse of degradation products in a single step. It enables large-scale mass production and exhibits ORR performance comparable to commercial Pt / C catalysts. Furthermore, in aqueous alkaline zinc-air batteries, it surpasses the peak power density of zinc-air batteries assembled with Pt / C catalysts as air cathodes. This further promotes the reuse of waste plastics, reduces environmental pollution, and drives the mass production and commercialization of Co-based catalysts.

[0011] Co-MOFs are nanoporous crystalline materials formed by the coordination self-assembly of Co(II) and BDC, exhibiting highly stable structures and catalytic activity. This invention uses Co-MOFs as templates and performs N doping through mixing and calcination with MEL to obtain Co-N / Co@C. During the synthesis process, the integrity of the porous carbon framework structure of Co-MOFs is preserved, containing Co metal nanoparticles and Co single atoms. The high-temperature carbonization process in the preparation of the Co-N / Co@C catalyst exposes more active sites and introduces oxygen-containing functional groups, thus facilitating the electrocatalytic reaction.

[0012] Preferably, in step (1), the degradation method of PET is as follows: dissolve PET powder and NaOH powder in water, react at 40~200℃ for 3~24 h, adjust the pH value to 1, filter, dry, and obtain terephthalic acid ligand.

[0013] Preferably, after adjusting the pH, the process also includes washing and drying steps.

[0014] More preferably, the washing process includes: first wetting the organic filter paper with ethanol, and then washing it three times with deionized water.

[0015] Preferably, the PET powder and NaOH powder are ground into small-particle-size powders before being dissolved.

[0016] More preferably, the drying process adopts vacuum drying, with a temperature of 50~80℃ and a time of 12~48h.

[0017] Preferably, in step (1), NaOH powder is dispersed in water to obtain solution A, and PET and solution A are quickly mixed and reacted under stirring conditions so that the PET powder is immersed below the liquid surface.

[0018] Preferably, in step (1), the reaction temperature is 120~200℃, the reaction time is 3~12 h, and the stirring rate is 300~600 rpm.

[0019] Preferably, in step (2), the solvent is a mixture of N,N-dimethylformamide, ethanol and water in a volume ratio of (6~8):1:1.

[0020] Preferably, in step (2), the solvothermal reaction temperature is 40~200℃ and the time is 3~15 h.

[0021] Preferably, in step (2), the molar ratio of phthalic acid ligand to CoCl2·6H2O is 1:(0.5~5).

[0022] Preferably, in step (3), the mass ratio of the precursor Co-MOFs to melamine is 1:(0.5~10).

[0023] Preferably, in step (3), the pyrolysis carbonization is carried out in a tube furnace. First, a protective gas is introduced into the tube furnace to purge the air inside the tube, and the temperature is controlled to rise at 3~25℃ / min.

[0024] Preferably, in step (3), the pyrolysis carbonization temperature is 800~1200℃, the time is 0.5~7 h, and the heating rate is 3~15℃ min. −1 .

[0025] The present invention also provides a Co-N / Co@C catalyst prepared by the above preparation method.

[0026] The present invention also provides an application of the above-mentioned Co-N / Co@C catalyst in the preparation of zinc-air batteries.

[0027] As described above, the present invention has the following beneficial effects:

[0028] (1) By degrading waste plastic PET, ligand BDC is obtained, which is then coordinated with Co metal salt and calcined with MEL to obtain N-doped carbon-based composite material, namely Co-N / Co@C catalyst. Degrading PET not only reduces environmental pollution and contributes to the cause of green chemistry, but also promotes the further commercialization and large-scale application of Co-based catalysts and zinc-air batteries;

[0029] (2) Compared with precious metal-based catalysts, it significantly reduces production costs;

[0030] (3) Improve the ORR performance of the catalyst in the battery compared to commercial Pt / C catalysts. Attached Figure Description

[0031] Figure 1 shows SEM images of BDC-D obtained from degradation in Example 1 and the pure chemical drug BDC-P.

[0032] Figure 2 shows the SEM image (a), EDX mapping (b), and energy-dispersive X-ray elemental mapping (EDX) of the Co-N / Co@C catalyst prepared in Example 1 (c).

[0033] Figure 3 shows the XRD patterns of BDC-D and BDC-P obtained in Example 1.

[0034] Figure 4 shows the XRD patterns of the Co-N / Co@CD catalyst and the Co-N / Co@CP catalyst obtained in Example 1.

[0035] Figure 5 shows the linear voltammetric scan (LSV) curves of Co-N / Co@CD catalyst, commercial Pt / C and Co-N / Co@CP catalyst in 0.1 M KOH electrolyte with different MEL feed ratios.

[0036] Figure 6 shows the open-circuit voltages of the Co-N / Co@CD catalyst prepared in Example 1, the commercial Pt / C catalyst, and the Co-N / Co@CP catalyst applied to zinc-air batteries.

[0037] Figure 7 shows the peak power density of the Co-N / Co@CD catalyst prepared in Example 1, the commercial Pt / C catalyst, and the Co-N / Co@CP catalyst applied to a zinc-air battery. Detailed Implementation

[0038] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0039] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0040] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0041] Example 1

[0042] This application provides a method for preparing a Co-N / Co@C catalyst for the degradation of PET, comprising the following steps:

[0043] Step (1): Preparation of ligand BDC: Dissolve 1.5 g PET powder and 1.25 g NaOH in 30 mL deionized water, label it solution A, stir, and after the powder is submerged in the liquid, hydrothermally heat at 200℃ for 6 h; then adjust the pH of the hydrothermally heated solution A to pH=1 using NaOH and HCl solutions, label it solution B. Filter and wash solution B, collect the sample, and vacuum dry at 60℃.

[0044] Step (2): Preparation of precursor Co-MOFs: Weigh 0.75 mmol CoCl2·6H2O and BDC powder into a reaction vessel, then add 30 mL N,N-dimethylformamide (DMF), 4 mL ethanol and 4 mL deionized water. After the powdered drug is completely dissolved, place it in a forced-air oven at 140℃ for 9 h. Finally, wash with deionized water 3 times and ethanol once, and then vacuum dry at 60℃.

[0045] Step (3): Preparation of the composite catalyst of Co nanoparticles and single-atom Co-NC: Weigh 10 mg of the prepared precursor Co-MOFs powder and 50 mg of MEL and place them in a crucible. Place the crucible in the heating zone of a tube furnace and purge with nitrogen for 30 min. Heat the crucible to 900 °C at a rate of 3 °C / min. After holding the crucible at 900 °C for 2 h, allow it to cool naturally to room temperature under nitrogen protection to obtain the sample Co-N / Co@C, which is the composite catalyst of Co nanoparticles and single-atom Co-NC.

[0046] The material obtained in this embodiment was characterized, and the results are as follows:

[0047] Figures 1a and 1b are SEM images of BDC-D obtained by degradation in Example 1 and pure chemical drug BDC-P. As can be seen from the figures, the drug BDC exhibits a layered stacked morphology, while the BDC obtained by degrading PET exhibits a finer amorphous block shape.

[0048] Figures 2a and 2b are SEM images of the catalyst for synthesizing Co-N / Co@CD from degraded PET and the pure chemical Co-N / Co@CP obtained in Example 1. There is no significant difference in morphology, indicating that the degraded TPA can react normally with Co. 2+ Coordination was performed; Figure 2c shows the energy-dispersive X-ray elemental (EDX) image, indicating the uniform distribution of Co, C, and N elements in the Co-N / Co@C composite material.

[0049] Figure 3 shows the XRD patterns of BDC-D and BDC-P obtained in Example 1, with characteristic peaks corresponding one-to-one. Figure 4 shows the XRD patterns of the degradation-synthesized Co-N / Co@CD catalyst (a) and the non-degradation-synthesized Co-N / Co@CP catalyst (b). The XRD patterns show that Co-N / Co@C exhibits high crystallinity, and the XRD spectrum has a broad characteristic peak around 21°, corresponding to the (002) crystal plane of graphite carbon (PDF#41-1487). Simultaneously, three characteristic peaks at 44°, 51°, and 75° correspond to the (111), (200), and (220) crystal planes of metallic cobalt (PDF#15-0806), respectively, indicating that the Co-N / Co@CD and Co-N / Co@CP composites simultaneously contain both graphite carbon and metallic Co phases.

[0050] The prepared composite material was subjected to rotating ring-disk electrode testing, and the results are shown in Figure 5. The LSV curves in Figure 5 indicate that the catalyst exhibits excellent ORR activity in O2-saturated 0.1 M KOH electrolyte, with Co-N / Co@CD possessing a high onset potential (Eonset) of 0.99 V and a half-wave potential (E) of 0.85 V. 1 / 2 ), superior to Co-N / Co@CP (Eonset = 0.85 V, E 1 / 2 = 0.78 V), even compared to commercial Pt / C (Eonset = 0.99 V, E 1 / 2 = 0.86 V) equivalent catalyst. This result indicates that Co-N / Co@CD can catalyze ORR efficiently, which is beneficial to improving the energy utilization rate of O2.

[0051] As shown in Figure 6, the Co-N / Co@CD battery exhibits a high open-circuit voltage of 1.365 V and demonstrates greater stability over extended periods in aqueous zinc-air batteries. Meanwhile, Figure 7 shows that the Co-N / Co@CD battery maintains a voltage of 271.4 mA cm⁻¹. -2 The peak power density output at the given current density is as high as 184.5 mW / cm². -2 The Co-N / Co@CP battery used has a capacity of 181.2 mA cm⁻¹. -2 It has a current density of 143.7 mW / cm². -2 The peak power density of commercially available Pt / C batteries is 141.4 mA cm⁻¹. -2 The peak power density at the current density is 122.9 mW / cm². -2 The increased catalytic activity and ion transport rate are due to the degradation and etching effects of NaOH and HCl. This result indicates that Co-N / Co@CD can operate stably and environmentally friendly, improving the environmental applicability and versatility of non-precious metal-based catalysts in energy conversion and storage.

[0052] Example 2

[0053] This application provides a method for preparing a Co-N / Co@C catalyst for the degradation of PET, comprising the following steps:

[0054] Step (1): Preparation of ligand BDC: Dissolve 1.5 g PET powder and 1.25 g NaOH in 30 mL deionized water, label it solution A, stir, and after the powder is submerged in the liquid, hydrothermally heat at 200℃ for 6 h; then adjust the pH of the hydrothermally heated solution A to pH=1 using NaOH and HCl solutions, label it solution B. Filter and wash solution B, collect the sample, and vacuum dry at 60℃.

[0055] Step (2): Preparation of precursor Co-MOFs: Weigh 0.75 mmol CoCl2·6H2O and BDC powder into a reaction vessel, then add 30 mL N,N-dimethylformamide (DMF), 4 mL ethanol and 4 mL deionized water. After the powdered drug is completely dissolved, place it in a forced-air oven at 140℃ for 9 h. Finally, wash 3 times with deionized water and 1 time with ethanol, and then vacuum dry at 60℃.

[0056] Step (3): Preparation of the composite catalyst of Co nanoparticles and single-atom Co-NC: Weigh 10 mg of the prepared precursor Co-MOFs powder and 10 mg of MEL and place them in a crucible. Place the crucible in the heating zone of a tube furnace and purge with nitrogen for 30 min. Heat the crucible to 900 °C at a rate of 3 °C / min. After holding the crucible at 900 °C for 2 h, allow it to cool naturally to room temperature under nitrogen protection to obtain the sample Co-N / Co@C, which is the composite catalyst of Co nanoparticles and single-atom Co-NC.

[0057] Example 3

[0058] This application provides a method for preparing a Co-N / Co@C catalyst for the degradation of PET, comprising the following steps:

[0059] Step (1): Preparation of ligand BDC: Dissolve 1.5 g PET powder and 1.25 g NaOH in 30 mL deionized water, label it solution A, stir, and after the powder is submerged in the liquid, hydrothermally heat at 200℃ for 6 h; then adjust the pH of the hydrothermally heated solution A to pH=1 using NaOH and HCl solutions, label it solution B. Filter and wash solution B, collect the sample, and vacuum dry at 60℃.

[0060] Step (2): Preparation of precursor Co-MOFs: Weigh 0.75 mmol CoCl2·6H2O and BDC powder into a reaction vessel, then add 30 mL N,N-dimethylformamide (DMF), 4 mL ethanol and 4 mL deionized water. After the powdered drug is completely dissolved, place it in a forced-air oven at 140℃ for 9 h. Finally, wash with deionized water 3 times and ethanol once, and then vacuum dry at 60℃.

[0061] Step (3): Preparation of the composite catalyst of Co nanoparticles and single-atom Co-NC: Weigh 10 mg of the prepared precursor Co-MOFs powder and 100 mg of MEL and place them in a crucible. Place the crucible in the heating zone of a tube furnace and purge with nitrogen for 30 min. Heat the crucible to 900 °C at a rate of 3 °C / min. After holding the crucible at 900 °C for 2 h, allow it to cool naturally to room temperature under nitrogen protection to obtain the sample Co-N / Co@C, which is the composite catalyst of Co nanoparticles and single-atom Co-NC.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a Co-N / Co@C catalyst, characterized in that, Includes the following steps: (1) PET was degraded to obtain terephthalic acid ligands; (2) the terephthalic acid ligands and CoCl2·6H2O were dissolved in a solvent and subjected to a solvothermal reaction to obtain precursor Co-MOFs; (3) the precursor Co-MOFs were mixed with melamine and pyrolyzed under a protective atmosphere to obtain Co-N / Co@C catalyst.

2. The preparation method according to claim 1, characterized in that: In step (1), the degradation method of PET is as follows: dissolve PET powder and NaOH powder in water, react at 40~200℃ for 3~24 h, adjust the pH value to 1, filter, dry, and obtain terephthalic acid ligand.

3. The preparation method according to claim 1, characterized in that: In step (2), the solvent is a mixture of N,N-dimethylformamide, ethanol and water in a volume ratio of (6~8):1:

1.

4. The preparation method according to claim 1, characterized in that: In step (2), the solvothermal reaction temperature is 40~200℃ and the time is 3~15 h.

5. The preparation method according to claim 1, characterized in that: In step (2), the molar ratio of phthalic acid ligand to CoCl2·6H2O is 1:(0.5~5).

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of the precursor Co-MOFs to melamine is 1:(0.5~10).

7. The preparation method according to claim 1, characterized in that: In step (3), the pyrolysis carbonization is carried out in a tube furnace. First, protective gas is introduced into the tube furnace to purge the air inside the tube, and the temperature is controlled to rise at 3~25℃ / min.

8. The preparation method according to claim 1, characterized in that: In step (3), the pyrolysis carbonization temperature is 800~1200℃, the time is 0.5~7 h, and the heating rate is 3~15℃ min. −1 .

9. A Co-N / Co@C catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the Co-N / Co@C catalyst as described in claim 9 in the preparation of zinc-air batteries.

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