Nitrogen-doped ordered mesoporous carbon nanospheres prepared based on pure water phase and preparation method thereof

Abstract

The invention relates to a nitrogen-doped ordered mesoporous carbon nanosphere prepared on the basis of a pure water phase and a preparation method of the nitrogen-doped ordered mesoporous carbon nanosphere, an amphiphilic copolymer is used as a structure-directing agent, a nitrogen-containing or oxygen-containing functional group monomer is used as a carbon source, and synergistic self-assembly of a template and a precursor is realized through interaction of hydrogen bonds and the like in the water phase; carrying out in-situ polymerization under the action of a proper initiator to form a polymer / template compound and precipitating the polymer / template compound into an ordered precursor; and then carrying out temperature programming carbonization in an inert atmosphere, and removing the template and the surfactant to obtain the nitrogen-doped ordered mesoporous carbon nanospheres. According to the process, water serves as a unique solvent, a corrosive etching agent is not needed, the process is simplified, environment friendliness is achieved, enlarged production is easy, the carbon yield and energy consumption have competitive advantages, and the prepared nitrogen-doped ordered mesoporous carbon shows remarkable application potential in the fields of electrochemical energy storage (such as zinc ion batteries), catalysis, environment purification and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology and relates to a method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on pure aqueous phase. Background Technology

[0002] Mesoporous carbon materials have attracted widespread attention in adsorption, separation, catalysis, and electrochemical energy storage due to their high specific surface area, tunable pore size distribution, excellent electrical conductivity, and chemical stability. Their development can be roughly divided into the following three stages: (1) Hard template method stage: Early studies often used mesoporous silica molecular sieves (such as MCM-48 and SBA-15) as hard templates, replicating the pore structure by injecting carbon sources, carbonizing, and etching to remove the template. This method can obtain highly ordered mesoporous carbon, but its preparation process is complex and costly, and it requires the use of corrosive chemicals such as hydrofluoric acid or strong alkaline solutions, which does not conform to the principles of green chemistry.

[0003] (2) Soft template method and biomass derivation stage: The subsequently developed soft template method utilizes amphiphilic block copolymers (such as Pluronic P123 and F127) as templates, which, along with carbon sources (such as phenolic resins), form ordered composite structures through solvent evaporation-induced self-assembly (EISA), followed by carbonization to obtain mesoporous carbon. This method simplifies the preparation process, but still heavily relies on organic solvents, and the carbon yield is low (typically below 30%).

[0004] Biomass-derived materials use natural polymers as carbon sources. While they have advantages such as wide availability of raw materials and low cost, the resulting carbon materials have a wide pore size distribution, disordered structure, and poor controllability.

[0005] (3) Functionalization and Compositeization Stage: In recent years, the electrochemical performance of mesoporous carbon has been further improved through strategies such as doping with heteroatoms (e.g., N, B, P, S) or combining it with other nanomaterials (e.g., carbon nanotubes, graphene, MXenes). High-performance mesoporous carbon has shown significant application potential in energy storage fields such as supercapacitors, lithium-ion batteries, sodium-ion batteries, and zinc-ion capacitors.

[0006] Among numerous energy storage systems, zinc-based electrochemical energy storage systems (including Zn-based systems) are particularly important. 2+Zinc-ion batteries (ZIBs) based on intercalation / deintercalation reactions, as well as Zn-I2 and Zn-Br2 batteries based on conversion reactions, have become strong contenders for next-generation energy storage technologies due to their high safety, low cost, and high theoretical capacity. However, the development of these systems is limited by the performance of cathode materials. Whether it is an intercalation-type cathode such as manganese-based or vanadium-based cathodes, or a conversion-type cathode such as iodine or bromine, they all suffer from problems such as insufficient conductivity, slow reaction kinetics, poor cycle stability, and dissolution of active materials (shuttle effect).

[0007] Carbon materials are widely used as conductive additives or host materials to improve cathode performance. Among these, pore structure and surface chemistry are key influencing factors. Mesoporous structures facilitate the transport of electrolyte ions and active materials (such as I3). - ,Br - Rapid diffusion and transport of nitrogen enhances rate performance; high nitrogen doping not only improves the electronic conductivity of the carbon skeleton, but also provides additional active sites through surface defects and functional groups, enhancing the adsorption and anchoring of active materials, suppressing dissolution loss, and promoting electrode reaction kinetics to a certain extent.

[0008] Nitrogen-containing polymers are considered ideal precursors for preparing nitrogen-doped carbon materials. However, carbon materials obtained by direct carbonization of traditional polymers are often predominantly microporous with disordered pore structures and poor connectivity, resulting in low specific surface area, which is not conducive to high-speed ion transport and energy storage applications.

[0009] For example, Chinese patent application CN202211691397.4 provides a method for preparing mesoporous multilayered helical chiral nitrogen-doped carbon nanospheres and their applications. It utilizes commercially available PEOPPOPEO triblock copolymer surfactants (such as F127, P123, F68, F108, etc.) as template agents, dopamine hydrochloride as nitrogen and carbon sources, an inorganic base as a catalyst, benzene derivative organic small molecules as structure-directing agents, and methylbenzene organic small molecules as pore-expanding agents. These reagents are dissolved in a mixture of alcohol and water to form a homogeneous solution system. The reaction yields mesoporous polydopamine nanospheres with various morphologies. The obtained polydopamine nanospheres are calcined in an inert atmosphere to finally obtain mesoporous nitrogen-doped carbon nanospheres with various morphologies. This patent is still based on an organic solvent system, and its greenness needs to be improved. At the same time, although it may achieve some morphology control, there is still significant room for improvement in terms of structural order, pore size distribution control, nitrogen doping configuration optimization, morphology uniformity and electrochemical performance of mesoporous carbon nanospheres. Summary of the Invention

[0010] The purpose of this invention is to provide a method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase. This method allows for preparation under pure aqueous conditions, and the resulting material exhibits a highly ordered mesoporous structure (pore size mainly distributed in the range of 2–50 nm), ultra-small particle size (<100 nm), and a large specific surface area (approximately 100–120 m²). 2 / g) and / or higher nitrogen and oxygen content (approximately 5~15 at%).

[0011] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase, with a BET specific surface area of ​​100-500 m². 2 / g, with a highly ordered mesoporous structure, pore size distribution of 2~50 nm, particle size less than 100 nm, and nitrogen doping content of 5~15 at.

[0012] In a second aspect, the present invention has provided a method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase, comprising the following steps: S1. Place the amphiphilic copolymer in water, stir to dissolve and form a micelle solution, then add nitrogen- or oxygen-containing small molecule monomers, disperse them fully, and then add an aqueous solution of oxidant dropwise under warm water bath conditions to initiate monomer oxidative polymerization. S2. After the reaction is complete, ethanol is added to the reaction system of S1. The resulting suspension is centrifuged, vacuum filtered to collect the solid product, and then washed and dried to obtain the amphiphilic polymer / nitrogen-containing polymer composite precursor powder. S3. The amphiphilic polymer / nitrogen-containing polymer composite precursor powder obtained in S2 is placed in an inert atmosphere for heat treatment, then cooled to room temperature, and the product is collected, which is nitrogen-doped ordered mesoporous carbon nanospheres.

[0013] Furthermore, in S1, the amphiphilic copolymer is a triblock copolymer series or a Brij series (i.e., polyoxyethylene alkyl ethers), wherein the triblock copolymer series is a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, preferably P123, F127 (i.e.), or F108, and the Brij series is Brij78, Brij67, or Brij98.

[0014] Furthermore, in S1, the nitrogen- or oxygen-containing small molecule monomer is pyrrole, aniline, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, or 2,6-diaminopyridine.

[0015] Furthermore, in S1, the molar ratio of nitrogen- or oxygen-containing small molecule monomers to amphiphilic copolymers is 1:2 to 35, and for example, it can be 1:2, 1:4, 1:8, 1:10, 1:15, 1:30, 1:35, etc.; the molar ratio of oxidant to nitrogen- or oxygen-containing small molecule monomers is 1 to 10:1, and for example, it can be 1:1, 2:1, 3:1, 5:1, 10:1, etc.

[0016] In addition, preferably, the mass ratio of the amphiphilic copolymer to deionized water is 1:50 to 200. For example, it can be 1:50, 1:100, 1:200, etc.

[0017] Furthermore, in S1, the oxidant is ammonium persulfate, potassium persulfate, or ferric chloride.

[0018] Furthermore, in S1, the reaction temperature for oxidative polymerization is 25~60℃, and the reaction time is 6~12h.

[0019] Furthermore, in S3, the inert atmosphere is provided by nitrogen or an inert gas, wherein the inert gas is argon.

[0020] Furthermore, in S3, the holding temperature during the heating heat treatment process is 600~1200℃, and the holding time is 3~4h.

[0021] Furthermore, in S3, the heating rate during the heat treatment process is 1~10℃ / min.

[0022] Furthermore, the prepared mesoporous carbon nanospheres can be used as electrode active components to construct electrochemical devices such as zinc-ion batteries, exhibiting excellent energy storage performance. Their specific capacity at a current density of 0.1 A / g is higher than that of similar undoped carbon materials, and their capacity retention exceeds 90% after 1000 cycles. In addition, this material also demonstrates good stability and activity in catalytic oxygen reduction reaction (ORR), organic pollutant adsorption, and electrocatalytic conversion.

[0023] To address the common challenge of "difficulty in forming and solidifying ordered mesoporous structures" in pure aqueous systems, this invention designs a coupling mechanism of in-situ oxidative polymerization, synergistic self-assembly, and polymerization-induced precipitation. Based on this mechanism, the components of each raw material and process conditions are optimized and combined to achieve the production of nitrogen-doped mesoporous carbon nanospheres with "high order, ultra-small particle size, and large specific surface area" even in pure aqueous systems.

[0024] Specifically, this invention first selects nitrogen-containing small molecule monomers such as pyrrole, which are highly soluble in water, readily undergo oxidative polymerization, and possess a π-conjugated structure, as carbon / nitrogen sources. In a pure water micelle system formed by an amphiphilic copolymer template, an oxidant such as ammonium persulfate is introduced, and slow, controlled in-situ oxidative polymerization is carried out at 25–60°C. During this process, the newly formed oligomeric / polypyrrole segments, on the one hand, possess a π-conjugated backbone and polar groups, enabling them to interact with the hydrophobic segments of the amphiphilic copolymer through hydrophobic / π~π interactions and with the hydrophilic segments through hydrogen bonds; on the other hand, they exhibit a tendency to gradually decrease in water solubility. Therefore, the polymerization reaction itself becomes the driving force, preferentially enriching and "locking" the monomers at the micelle core-shell interface or within the micelles, achieving spatial and temporal synergistic coupling between the polymerization process and the template self-assembly process, rather than a simple superposition of self-assembly followed by curing.

[0025] Meanwhile, this invention, by limiting the mass ratio of template to water to 1:50~200, the molar ratio of monomer to template to 1:2~30, the molar ratio of oxidant to monomer to 1~100:1, and the polymerization time of 6~12 h and a suitable polymerization temperature, ensures that the in-situ polymerization rate matches the micelle self-assembly and growth process: the template concentration is sufficient to form large-scale ordered micelle domains, the monomer concentration provides sufficient carbon / nitrogen sources while avoiding the formation of large free polymers, and a slight excess of oxidant ensures complete polymerization without "bursting" and destroying the ordered structure. Within this process window, as the degree of polymerization gradually increases, the template / polymer composite evolves from a soluble micelle system into precursor particles with a certain degree of rigidity and precipitates from the aqueous phase, i.e., "polymerization-induced precipitation" occurs, thus completing the solidification of the ordered structure and limiting the particle size in the aqueous phase.

[0026] Building upon this, the present invention further controls the carbonization heating rate (1~10℃ / min), carbonization temperature (600~1200℃), and holding time (3~4 h) to ensure that the template decomposition / removal and polymer carbonization processes proceed relatively gently and synchronously, maximizing the preservation of the ordered mesoporous structure and spherical morphology in the precursor. Since the precursor itself is composed of a nitrogen-containing π-conjugated polymer, carbonization naturally results in uniformly nitrogen-doped, regularly pore-forming materials with a particle size less than 100 nm and a specific surface area of ​​100~500 m². 2 Ordered mesoporous carbon nanospheres with a pore size ranging from 2 to 50 nm per g.

[0027] It can be said that the technical effect of this invention does not stem from a single raw material or a single process parameter, but rather from the combined effect of a whole set of mechanism designs: "specific nitrogen-containing monomer + specific amphiphilic copolymer template + pure aqueous phase + oxidative polymerization system + limited ratio and temperature and time conditions".

[0028] Compared with the prior art, the present invention has the following advantages: (1) Green and environmentally friendly, with simplified process The entire synthesis process of this invention uses water as the sole reaction medium, completely avoiding the use of toxic organic solvents such as phenols, aldehydes, and alcohols in traditional methods, making the reaction system safe and environmentally friendly. The template removal process is completed spontaneously through pyrolysis, eliminating the need for additional chemical etching steps or template recovery processes, thus eliminating dependence on highly corrosive chemicals such as hydrofluoric acid. This method significantly simplifies the process flow, reduces wastewater discharge, and meets the requirements of green chemistry and sustainable development.

[0029] (2) Low cost and low energy consumption This invention employs an aqueous system and a one-step self-assembly process, with mild reaction conditions (room temperature or low-temperature water bath is sufficient) and significantly lower energy consumption than organic solvent systems. The raw materials used are inexpensive and readily available, with a high carbonization yield (>40%), greatly reducing the material cost per batch. The overall production cost has a significant competitive advantage, making it suitable for industrial-scale application.

[0030] (3) Controllable structure and excellent performance The nitrogen-doped ordered mesoporous carbon material obtained by this invention has the characteristics of uniform and tunable mesoporous structure, high specific surface area, high nitrogen doping content and ultra-small particle size.

[0031] This structure enables the material to exhibit excellent performance in applications such as electrochemical energy storage, catalysis, and adsorption. For example, when used as a positive electrode active material in zinc-ion battery systems, it exhibits high specific capacity, excellent rate performance, and long cycle life; in electrocatalytic reactions, its abundant nitrogen active sites and ordered mesoporous structure significantly improve reaction rate and stability.

[0032] (4) The process is highly scalable and easy to scale up production. The synthesis method employed in this invention is a one-step aqueous phase reaction, characterized by a simple process flow, mild reaction conditions, and high reproducibility. Product formation relies on a self-assembly process, requiring no complex equipment control. This method is easily scalable for continuous industrial production, suitable for large-scale manufacturing and batch stability control, and possesses promising industrialization prospects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation process of the nitrogen-doped ordered mesoporous carbon material of the present invention, showing the entire process from raw materials to the final product.

[0034] Figure 2 The nitrogen adsorption-desorption isotherm (BET method) of the nitrogen-doped ordered mesoporous carbon material prepared in Example 1 shows a typical type IV curve and a type H1 hysteresis loop.

[0035] Figure 3The pore size distribution curve (BJH method) of the material prepared in Example 1 shows that its average pore size distribution is around 24.8 nm.

[0036] Figure 4 The image shown is a scanning electron microscope (SEM) image of the material prepared in Example 1, which shows that its macroscopic morphology consists of uniform porous spherical particles.

[0037] Figure 5 The images show transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the material prepared in Example 1, clearly demonstrating its ordered porous structure.

[0038] Figure 6 The full X-ray photoelectron spectroscopy (XPS) spectrum and fine C1s, O1s, and N1s spectra of the material prepared in Example 1 were obtained to confirm its high nitrogen content and nitrogen configuration distribution.

[0039] Figure 7 The image shows a SEM image of Comparative Example 1 (nitrogen-doped carbon prepared without the P123 template), revealing its dense and disordered morphology.

[0040] Figure 8 The nitrogen adsorption-desorption isotherm and pore size distribution diagram of the material prepared in Comparative Example 1 show that its pore size distribution is random and its specific surface area is low.

[0041] Figure 9 The charge-discharge curves of the material from Example 1 as the positive electrode of a zinc-iodine battery under high load (5 mg) conditions at a current density of 1 A / g are shown.

[0042] Figure 10 The chart shows the rate performance comparison of the material from Example 1 as the positive electrode of a zinc-iodine battery (current density from 0.1 A / g to 10 A / g).

[0043] Figure 11 The graph shows the long-cycle performance (1500 cycles) of the material from Example 1 as the positive electrode of a zinc-iodine battery under high loading (5 mg) conditions at a current density of 1 A / g.

[0044] Figure 12 The graph shows the long-cycle performance (2000 cycles) of the material from Example 1 as the positive electrode of a zinc-iodine battery under low loading (3 mg) conditions at a current density of 1 A / g.

[0045] Figure 13 The images show the TEM / SEM results for comparative examples 2-4. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0048] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0049] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0050] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0051] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0052] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0053] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0054] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0055] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0056] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0057] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0058] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0059] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0060] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, but sequentially is preferred.

[0061] This invention discovers through research that the conventional approach to preparing ordered mesoporous carbon is to use mixed solvent systems such as alcohol / water, utilizing organic solvents to adjust interfacial tension and solubility to improve the compatibility between the template and the carbon source, and to achieve the solidification and shaping of the structure through processes such as the evaporation (EISA) of organic solvents and the sol-gel transition. Therefore, within this mainstream framework, the pure water system used in this invention is generally considered to have the following technical obstacles: First, many traditional carbon sources have insufficient solubility in water and insufficient compatibility with the template, making it difficult to form a homogeneous template-precursor mixed phase in pure water; Second, in pure water systems, the interaction between the template and general carbon sources relies mainly on weak hydrogen bonds and van der Waals forces, resulting in limited interaction energy. Self-assembly often remains at a local short-range order, making it difficult to form a stable large-scale ordered mesoporous structure; Third, in the absence of organic solvent evaporation or sol-gel solidification channels, simple aqueous phase self-assembly is difficult to "freeze" the soft micelle structure. During drying and subsequent heat treatment, particle agglomeration and pore collapse are very likely to occur, often resulting in disordered porous carbon or bulk dense carbon. These common understandings naturally lead those skilled in the art to tend to use mixed solvent systems such as alcohol / water, rather than attempting to construct highly ordered mesoporous carbon structures in a completely pure aqueous phase.

[0062] Based on this, the present invention does not simply replace alcohol / water with water, but rather addresses the aforementioned technical obstacles of pure water systems by specifically designing special monomer types, special oxidative polymerization methods, and ratios / process windows. Through a new mechanism of action, it compensates for the lack of solubility, interaction strength, and structural solidification means in pure water systems. Specifically: (1) In terms of raw material selection, this invention limits the use of nitrogen-containing monomers such as pyrrole, which are highly soluble in water, easily oxidized and polymerized, and have a π-conjugated skeleton, so that they can penetrate into the hydrophobic core or interface region of the amphiphilic copolymer micelles and form strong π-π and hydrophobic interactions with the template after polymerization, significantly enhancing the binding between the template and the precursor; (2) In terms of reaction mode, this invention uses oxidants such as ammonium persulfate to initiate in-situ oxidative polymerization in pure water, making the "polymerization reaction" itself the core factor driving self-assembly and structural solidification: as polymerization proceeds, the polymer / template complex gradually loses its solubility and undergoes polymerization-induced precipitation, directly forming spherical precursor particles with a certain mechanical strength in the aqueous phase, thereby replacing the solidification path that relies on solvent evaporation or gelation in the traditional alcohol / water system; (3) In terms of process parameters, this invention achieves dynamic balance of polymerization rate, template self-assembly and precipitation solidification process by strictly limiting the ratio of template:water, monomer:template, oxidant:monomer, as well as temperature and time, thus avoiding the large-scale agglomeration and structural collapse of free polymers. It is the combination of the special monomers, special oxidant systems and special process conditions that enables the production of highly ordered mesoporous carbon nanospheres with ultra-small particle size and large specific surface area in the seemingly "difficult" solvent system of pure water. This mechanism design has no clear inspiration in existing similar processes using alcohol / water or other organic solvent systems.

[0063] In other words, this invention does not simply use common amphiphilic copolymer templates and nitrogen-containing monomers. Instead, it addresses the technical obstacles commonly found in pure aqueous systems, such as insufficient solubility, insufficient assembly driving force, and difficulty in structural solidification. Through innovative mechanisms of in-situ oxidative polymerization, synergistic self-assembly, and polymerization-induced precipitation, as well as corresponding component selection and process window limitation, it transforms the "pure aqueous phase" from a solvent system that is difficult to use in existing technologies into an effective solution for the stable preparation of highly ordered, ultra-small particle size, and large specific surface area mesoporous carbon nanospheres. This demonstrates the key innovations of this invention in terms of its mechanism of action and process design.

[0064] The concept of the present invention will be further described in detail below with reference to specific embodiments and experimental data. In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available materials or conventional processing techniques in the art.

[0065] Example 1: Preparation of nitrogen-doped ordered mesoporous carbon material (P123 / PPy-1) (1) Accurately weigh 800 mg of P123 (Mw=5800) into a 250 mL beaker and add 80 mL of deionized water. Place the beaker in the air and stir magnetically at 500 rpm for 30 minutes until P123 is completely dissolved to obtain a micelle solution.

[0066] (2) Add 300 μL of pyrole monomer (Pyrole, 99%) to the above solution and continue stirring for 5 minutes to ensure complete dispersion. Transfer the beaker to a 40°C water bath. Separately, dissolve 1.2 g of ammonium persulfate (APS) in 50 mL of 0.1 M sulfuric acid solution and slowly add it to the beaker. After the addition is complete, maintain the reaction under warm water bath conditions for 8 hours. Throughout the process, the solution gradually changes from colorless to bluish-black and finally to jet black.

[0067] (3) After the reaction was completed, the resulting dark black suspension was transferred in batches to 50 mL centrifuge tubes, and anhydrous ethanol was added at a volume ratio of 1:1. The mixture was centrifuged at 10,000 rpm for 3 minutes, and the supernatant was discarded. The precipitate was resuspended in 50 mL of anhydrous ethanol, ultrasonically dispersed, and centrifuged again. This washing process was repeated twice. The final precipitate was transferred to a freeze-drying bottle and freeze-dried at -50℃ for 24 hours to obtain a black, fluffy P123 / polypyrrole composite precursor powder.

[0068] (4) Take the above precursor powder and spread it evenly in a graphite boat. Place the graphite boat in the constant temperature zone of a horizontal tube furnace, seal it, and purge it with high-purity nitrogen (99.999%) for 5 minutes to remove all air. Then, under a continuous nitrogen flow, program the temperature to 800°C at a rate of 5°C / min. After reaching 800°C, hold it at that temperature for 3 hours. After the program is completed, stop heating and allow the furnace to cool naturally to room temperature (<50°C) under nitrogen protection. Remove the graphite boat, collect the black lumps inside, and grind them slightly to obtain the final product P123 / PPy-1.

[0069] Examples 2-3: Effect of different template solution concentrations (P123 / PPy-2, P123 / PPy-3) The preparation process is the same as in Example 1, except that the mass of P123 added is changed in step (1). Specifically, the mass of P123 added in Example 2 (P123 / PPy-2) is 25 mg, and the mass of P123 added in Example 3 (P123 / PPy-3) is 1500 mg. All other parameters are exactly the same as in Example 1.

[0070] Comparative Example 1: Preparation of template-free nitrogen-doped carbon (PPy) Without adding the P123 template, the remaining steps were exactly the same as in Example 1. Specifically, 300 μL of pyrrole monomer was directly dissolved in 80 mL of deionized water, and 50 mL of 0.1 M sulfuric acid solution containing 1.2 g of APS was slowly added under a 40°C water bath. The reaction was allowed to proceed for 8 hours. Subsequent centrifugation, washing, drying, and pyrolysis at 800°C for 3 hours yielded the product PPy.

[0071] Material structure characterization The materials obtained in Example 1 and Comparative Example 1 were systematically characterized: (1) Pore structure analysis: N2 adsorption-desorption isotherm of P123 / PPy-1 in Example 1 ( Figure 2 The curve is a typical type IV curve, with a distinct H1-type hysteresis loop near P / P0 = 0.9, indicating that it has regular cylindrical mesopores. The specific surface area of ​​BET is 10⁸ m². 2 / g. Pore size distribution curve ( Figure 3 The sample showed a sharp single peak with a most probable pore size of 2.7 nm. In contrast, PPy in Comparative Example 1 (…) Figure 8 It is mainly filled with micropores, with a specific surface area of ​​only 12.6 m². 2 / g, with a wide and disordered pore size distribution.

[0072] (2) Morphological and structural analysis: SEM images of P123 / PPy-1 ( Figure 4 The image shows that it consists of spherical particles with porous surfaces. HRTEM image ( Figure 5 The image clearly shows ordered, alternating light and dark channels, confirming its ordered mesoporous structure. Comparative Example 1: SEM image of PPy ( Figure 7 It then appears as a dense, irregular mass of large aggregates.

[0073] (3) Surface chemical analysis: X-ray photoelectron spectroscopy (XPS) analysis showed that the total nitrogen content of the material was as high as 14.5 at%. After peak fitting, its N 1s fine spectrum could be clearly resolved into two main characteristic peaks: the peak with a binding energy of 398.5 eV was attributed to pyridine nitrogen (N-6), while the peak with a binding energy of 401.5 eV was attributed to graphitic nitrogen (NQ). This result indicates that the material successfully combines high nitrogen doping with a large-pore structure, and the nitrogen species exist in a form with extremely high electrochemical activity.

[0074] (4) Electrochemical performance testing Using the above materials as the negative electrode active material, conductive carbon black as the conductive agent, and PVDF as the binder, a slurry was prepared by mixing them in NMP solvent at a mass ratio of 7:2:1. This slurry was pressed onto a titanium mesh, dried at 60°C for 12 hours, and then pressed into a sheet to form the working electrode. Zinc foil was used as the counter electrode and reference electrode, a glass fiber membrane as the separator, and an aqueous solution of 3M ZnSO4 + 0.5M KI as the electrolyte. A CR2025 coin cell was assembled in air.

[0075] Charge-discharge test: At a current density of 1 A / g, the P123 / PPy-1 electrode ( Figure 9 The first-week discharge specific capacity reached 125 mAh / g, and the charge-discharge curve was approximately a sloping line, exhibiting typical capacitive behavior.

[0076] Ratio performance: such as Figure 10 As shown, the reversible capacities of the P123 / PPy-1 electrode at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A / g are 195, 188, 158, 126, 103, 75, and 22 mAh / g, respectively. When the current density returns to 0.1 A / g, the capacity recovers to 198 mAh / g, demonstrating excellent rate performance and structural stability.

[0077] Cyclic performance: such as Figure 11 As shown, under a high loading of 5 mg, the P123 / PPy-1 electrode maintained a capacity retention of 99.7% after 1500 cycles at a high current density of 1 A / g; Figure 12 As shown, with a low loading of 3 mg, the P123 / PPy-1 electrode maintained a capacity retention of 97.1% after 2000 cycles at a high current density of 1 A / g, demonstrating its good cycling stability.

[0078] Comparative Example 2: Compared to Example 1, the only difference is that the pyrrole monomer is replaced with an equimolar amount of dopamine hydrochloride.

[0079] Experimental results show that although the nitrogen content of the sample obtained in Comparative Example 2 is still at a high level, its nitrogen configuration and pore structure characteristics are significantly different from those in Example 1. On the one hand, nitrogen adsorption-desorption tests show that although the specific surface area of ​​the sample in Comparative Example 2 is similar to that in Example 1, at 105 m², it is still significantly different from that in Example 1. 2 / g, but SEM / TEM revealed that the particle morphology of the Comparative Example 2 sample was no longer that of uniformly sized and well-spherically shaped nanospheres, but rather exhibited varying degrees of particle aggregation and irregular morphology, and lacked the clear mesoporous characteristics of Example 1. These results fully demonstrate that, within the framework of the pure aqueous phase oxidative polymerization-cooperative self-assembly-polymerization-induced precipitation mechanism constructed in this invention, only specific species, represented by pyrrole, can most effectively achieve the efficient synergistic effect of amphiphilic copolymer templates and the stable construction of ordered mesoporous structures in a pure aqueous phase.

[0080] Comparative Example 3: Compared to Example 1, the only difference is that the reaction solvent system is replaced with a mixture of equal volumes of ethanol and water (volume ratio 1:1).

[0081] Adding ethanol to the solution inhibits the hydrophobic interaction of P123 molecules, making it more difficult for them to form large aggregates, thereby reducing the micelle size and altering the shape of the nanospheres. Test results show that the specific surface area of ​​the sample in Comparative Example 3 is 10² m², as indicated by nitrogen adsorption-desorption tests. 2 / g, SEM / TEM observations showed that the particles in Comparative Example 3 were elliptical nanospheres with obvious particle aggregation, and also lacked the clear mesoporous characteristics of Example 1. This indicates that simply using the commonly used alcohol / water mixed solvent system in existing technologies will disrupt the fine matching relationship between in-situ oxidative polymerization and template synergistic self-assembly in this invention, making it difficult to obtain mesoporous carbon nanospheres with ultra-small particle size, highly ordered structure, and large specific surface area.

[0082] Comparative Example 4: Compared to Example 1, the only difference is that template agent P123 is replaced with template agent F127.

[0083] Experimental results show that the pore structure characteristics of the sample obtained in Comparative Example 4 are significantly different from those in Example 1: on the one hand, nitrogen adsorption-desorption tests show that the specific surface area of ​​the sample in Comparative Example 4 is lower than that in Example 1, only 54 m². 2 / g, on the other hand, SEM / TEM revealed that although Comparative Example 4 still consisted of nanospheres with good sphericity, its particle size uniformity was poor, with significant particle aggregation and insufficient mesoporous morphology. These results indicate that P123 is the most suitable template agent for obtaining mesoporous carbon nanospheres with uniform particle size, clear and ordered mesopores, and a large specific surface area.

[0084] Comparative Example 5: Compared to Example 1, the addition of an oxidant was omitted. Without the oxidant, the polymerization reaction of the monomers lacks a necessary initiator, making it difficult to polymerize and form a complete nanosphere structure. This demonstrates that an oxidant is indispensable for successfully realizing the mesoporous carbon nanospheres of this invention.

[0085] The TEM / SEM results of Comparative Examples 2, 3, and 4 are attached. Figure 13 As shown.

[0086] A comparison of Example 1 and the comparative examples above shows that this invention uses pure water as the sole solvent, completely eliminating inorganic alkalis and aromatic small molecule directing / pore-expanding agents. It initiates in-situ oxidative polymerization of pyrrole monomers in a pure water micelle system using oxidants such as ammonium persulfate. The self-assembly drive and structural solidification are achieved by utilizing the strong interaction between the nascent polymer and the template during polymerization, as well as the polymerization-induced precipitation process. This fundamentally overcomes the technical obstacles commonly found in traditional aqueous systems, such as insufficient solubility, insufficient assembly driving force, and difficulty in structural solidification. However, deviating from these key conditions defined by this invention makes it difficult to obtain particle sizes smaller than 100 nm and specific surface areas of 100-500 m². 2 Highly ordered mesoporous carbon nanospheres with pore sizes concentrated in the range of 2 to 50 nm and nitrogen content of 5 to 15 at% cannot exhibit the high rate performance and long cycle stability achieved by this invention in zinc-based energy storage systems such as zinc-iodine batteries.

[0087] Example 4: Mass production of nitrogen-doped ordered mesoporous carbon materials Large-scale preparation of P123 / PPy-1 material was carried out according to the method in Example 1. 4 g of P123 was weighed and added to 400 mL of deionized water, stirred and dissolved at room temperature. Then, 1.5 mL of pyrrole monomer was added, and stirring continued to disperse it evenly. Separately, 6 g of ammonium persulfate (APS) was dissolved in 2500 mL of 0.1 mol sulfuric acid solution, and the solution was slowly added to the above solution. The reaction was maintained at room temperature for 6-10 hours. After the reaction was completed, anhydrous ethanol was added at a volume ratio of 1:1, and the mixture was allowed to stand for 12-24 hours to precipitate. The lower precipitate was separated by vacuum filtration. After freeze-drying or drying in a 60°C oven, the precursor powder was obtained. Under nitrogen protection, the precursor powder was pyrolyzed in a tube furnace at 800°C for 3 hours to obtain a large quantity of nitrogen-doped ordered mesoporous carbon material.

[0088] This invention successfully develops a novel method for preparing nitrogen-doped ordered mesoporous carbon nanospheres via a green aqueous pathway. This method utilizes an aqueous self-assembly system using amphiphilic copolymers as templates to achieve one-step synergistic construction of nitrogen and carbon sources, avoiding the use of organic solvents and corrosive chemicals. The process is green, safe, and highly controllable.

[0089] The nitrogen-doped ordered mesoporous carbon nanospheres prepared by this invention possess four core characteristics: ordered mesoporous structure, high specific surface area, high nitrogen doping content, and ultra-small particle size. The synergistic effect of these structural features effectively solves key scientific problems commonly found in traditional carbon materials, such as slow ion transport, insufficient adsorption capacity, and limited energy storage capacity.

[0090] When applied to the cathode of high-performance zinc-iodine ion batteries, this material exhibits excellent electrochemical performance, including high specific capacity, excellent rate performance, and long-term cycle stability. Furthermore, it shows broad application potential in fields such as environmental catalysis and the adsorption and conversion of organic pollutants.

[0091] The green aqueous synthesis strategy proposed in this invention not only significantly reduces preparation costs and environmental risks, but also has good process scalability and industrial application prospects, providing a new material foundation and sustainable technical route for the development of next-generation advanced energy storage devices and environmental functional materials.

[0092] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase, characterized in that, Its BET specific surface area reaches 100~500 m² 2 / g, with a highly ordered mesoporous structure, pore size distribution of 2~50 nm, particle size less than 100 nm, and nitrogen doping content of 5~15 at.

2. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase as described in claim 1, characterized in that, Includes the following steps: S1. Place the amphiphilic copolymer in water, stir to dissolve and form a micelle solution, then add nitrogen- or oxygen-containing small molecule monomers, disperse them fully, and then add an aqueous solution of oxidant dropwise under warm water bath conditions to initiate monomer oxidative polymerization. S2. After the reaction is complete, ethanol is added to the reaction system of S1. The resulting suspension is centrifuged, vacuum filtered to collect the solid product, and then washed and dried to obtain the amphiphilic polymer / nitrogen-containing polymer composite precursor powder. S3. The amphiphilic polymer / nitrogen-containing polymer composite precursor powder obtained in S2 is placed in an inert atmosphere for heat treatment, then cooled to room temperature, and the product is collected, which is nitrogen-doped ordered mesoporous carbon nanospheres.

3. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S1, the amphiphilic copolymer is a triblock copolymer series or a Brij series, wherein the triblock copolymer series is P123, F127 or F108, and the Brij series is Brij78, Brij67 or Brij98.

4. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S1, the nitrogen- or oxygen-containing small molecule monomer is pyrrole, aniline, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, or 2,6-diaminopyridine.

5. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S1, the mass ratio of the amphiphilic copolymer to deionized water is 1:50~200; The molar ratio of nitrogen- or oxygen-containing small molecule monomers to amphiphilic copolymers is 1:2~35; The molar ratio of oxidant to nitrogen- or oxygen-containing small molecule monomer is 1 to 10:

1.

6. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S1, the oxidant is ammonium persulfate, potassium persulfate, or ferric chloride.

7. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S1, the reaction temperature for oxidative polymerization is 25~60℃, and the reaction time is 6~12h.

8. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S3, the inert atmosphere is provided by nitrogen or an inert gas, wherein the inert gas is argon.

9. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S3, the holding temperature during the heating heat treatment process is 600~1200℃, and the holding time is 3~4h.

10. The method for preparing nitrogen-doped ordered mesoporous carbon nanospheres based on a pure aqueous phase according to claim 2, characterized in that, In S3, the heating rate during the heat treatment process is 1~10℃ / min.

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