Carbon fiber material, its preparation method and application in co2 capture and electrocatalytic conversion

Abstract

The present application provides a kind of carbon fiber material and its preparation method and application in CO2 capture and electrocatalytic conversion.The present application creatively combines macro-scale hierarchical porous structure for enhanced mass transfer, atomic-level carbon vacancy defects for enhanced CO2 adsorption and activation, and molecular-level Ni-N X S Y Asymmetric active sites are integrated in one. This multiscale synergistic design enables the catalyst to simultaneously address both low CO2 concentration (mass transfer limitation) and oxygen-containing (competing reactions) challenges.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic carbon dioxide reduction technology, specifically to a carbon fiber material, its preparation method, and its application in CO2 capture and electrocatalytic conversion. Background Technology

[0002] Electrocatalytic reduction (ECO2RR) of carbon dioxide (CO2) to high-value-added chemicals (such as carbon monoxide) using renewable electricity is an important pathway to achieving the carbon cycle. The value of carbon monoxide (CO) extends far beyond its use as fuel; more importantly, it plays an irreplaceable core role as a key platform molecule and energy carrier in chemical engineering, fuel synthesis, and the carbon cycle economy. Currently, research on high-performance ECO2RR catalysts is mostly based on high-purity CO2 (>99%) systems. However, industrial waste gases (such as flue gas from coal-fired power plants and steel mills), which account for a major portion of global emissions, typically have two main characteristics: low CO2 concentration (10%-20%). (Reference 1. P. Huang, Z. Yang, K. Zhai, B. Huang, J. Zhou, X. Sun, Y. Lin, J. Xu, C. Pan, Y. Dong, Y. Wang, Y. Zhang, Y. Lou, H. Huang, Y. Zhu, J. Zhang. Balancing *CHO / *CO Intermediate Flux via Carbonyl-Hydroxyl Motif Synergy Enables High-Selectivity Ethanol Electrosynthesis from Dilute CO2). J. Am. Chem. Soc. 2025, 147The catalyst contains a certain concentration of oxygen (reference 2. DJDPimlott, A. Jewlal, Y. Kim, CP Berlinguette. Oxygen-Resistant CO2 Reduction Enabled by Electrolysis of Liquid Feedstocks. J. Am. Chem. Soc. 2023, 145, 25933–25937). This presents a dual challenge to the practical application of ECO2RR: 1. Low CO2 concentration leads to severe mass transfer limitation, resulting in insufficient reactant concentration on the catalyst surface, causing a sharp decrease in reaction current and Faraday efficiency, and exacerbating the competitive hydrogen evolution reaction (HER) (reference 3. L. Xie, Y. Cai, Y. Jiang, M. Shen, JC-H. Lam, J.-j. Zhu, W. Zhu. Direct low concentration CO2 electroreduction to multicarbon products via rate-determining step tuning. Nat Commun. 2024, 15, 10386). 2. Oxygen impurities trigger competitive oxygen reduction (ORR) reactions, which not only compete with CO2 for electrons and reduce the selectivity of the target product, but also produce highly reactive oxygen intermediates that oxidize and poison the active sites of the catalyst, leading to rapid deactivation (Reference 4. H. Guo, DH Si, HJ Zhu, ZA Chen, R. Cao, YB Huang. Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen. Angew. Chem. Int. Ed. 2024, 63, e202319472).

[0003] In existing technologies, to address the mass transfer problem of low-concentration CO2, efforts are typically focused on constructing porous structures to enrich CO2 (Reference 5. F. Zhang, Y. Si, J. Yu, B. Ding. Electrospun porous engineered nanofibermaterials: A versatile medium for energy and environmental applications. Chem. Eng. J. 2022, 456, 140989); while to improve oxygen tolerance, alloying or the use of noble metals are often employed. However, non-noble metal catalyst design and preparation methods that can simultaneously and synergistically address these two major challenges remain scarce. Developing an electrocatalyst that can operate efficiently and stably directly in complex industrial flue gas containing low concentrations of oxygen has significant practical application value. Summary of the Invention

[0004] The primary objective of this invention is to overcome the shortcomings of existing technologies and provide a carbon fiber material. This carbon fiber material, as a catalyst, should possess excellent CO2 enrichment capacity, high intrinsic CO selectivity, and outstanding oxygen tolerance and long-term stability.

[0005] Another objective of this invention is to provide a method for preparing the aforementioned carbon fiber material, wherein the method is process-controllable, easily scaled up, and capable of precisely constructing the desired microstructure.

[0006] Another object of the present invention is to provide the above-mentioned carbon fiber material as a catalyst for electrocatalytic CO2 reduction reaction, especially in electrochemical devices such as H-type electrolyzers, flow cells and metal-CO2 batteries.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A carbon fiber material, which is a nitrogen-doped porous carbon material rich in carbon vacancy defects, wherein single atoms and / or nanoclusters of metal M are anchored therein; the porous carbon material has a three-dimensional carbon nanofiber network structure. The metal M is selected from at least one of nickel, iron, or cobalt.

[0008] According to an embodiment of the invention, the carbon fiber material is further doped with carbon or sulfur, and is a porous carbon material rich in carbon vacancy defects, co-doped with carbon or sulfur and nitrogen, wherein single atoms and / or nanoclusters of metal M are anchored therein; the porous carbon material has a three-dimensional carbon nanofiber network structure. The metal M is selected from at least one of nickel, iron, or cobalt.

[0009] According to an embodiment of the invention, the carbon fiber material has one or more of the following properties: (1) Hierarchical porous and multi-channel fiber structure: The fiber has long-distance through-holes composed of mesopores and micropores, forming a "nano-sponge" structure. (2) High-density carbon vacancy defect network: The carbon framework is rich in intrinsic carbon vacancy defects; (3) Asymmetric Ni-N X S Y Active center: The doping of S atoms breaks the traditional symmetrical Ni-N4 configuration, forming a Ni-N core with Ni single atoms as the core. X S Y Asymmetric coordination structure.

[0010] This invention also provides a method for preparing the carbon fiber material as described above, comprising the following steps: (S1) Preparation of precursor solution: The carbon source polymer, pore-forming agent, metal M source and solvent are mixed to form a spinning solution; (S2) Electrospinning: The spinning solution obtained in step (S1) is electrospinned to obtain a polymer nanofiber film; (S3) Pre-oxidation stabilization: The fiber film obtained in step (S2) is subjected to pre-oxidation treatment at 220-280°C in an oxygen-containing atmosphere; (S4) Simultaneous carbonization and defect construction: The fiber material pre-oxidized in step (S3) and cyanuric acid are placed together in a tube furnace and carbonized at high temperature under an inert atmosphere; the cyanuric acid is placed upstream of the gas flow and the fiber material is placed downstream. The carbon source polymer is selected from at least one of polyacrylonitrile, polyamide, polyvinylpyrrolidone, polyacrylonitrile-based composite materials, or biomass-derived nitrogen-containing polymers. The pore-forming agent is selected from at least one of polymers or inorganic salts that can be decomposed and / or volatilized at high temperature in step (S3) pre-oxidative stabilization and / or step (S4) carbonization and defect synchronous construction steps. The metal source is at least one of a soluble nickel salt, a soluble iron salt, or a soluble cobalt salt.

[0011] In some embodiments of the present invention, the carbon source polymer in step (S1) is polyacrylonitrile.

[0012] In some embodiments of the present invention, the pore-forming agent in step (S1) is selected from at least one of polymethyl methacrylate, polylactic acid, polyvinyl alcohol, polystyrene, zinc oxide, and cadmium chloride.

[0013] In some embodiments of the present invention, the nickel source in step (S1) is nickel chloride (NiCl2·6H2O).

[0014] According to the embodiment of the invention, the mass ratio of carbon source polymer, pore-forming agent and metal M source in step (S1) is 1:(0.1-2):(0.01-0.5), for example 1:(1-2):(0.05-0.2), such as 1:(1-1.5):(0.08-0.15).

[0015] According to an embodiment of the invention, when the carbon fiber material is further doped with sulfur, the precursor solution in step (S1) also includes a sulfur source; the sulfur source is selected from sulfur-containing organic compounds and / or inorganic sulfides.

[0016] According to an embodiment of the invention, when the carbon fiber material is further doped with sulfur, the mass ratio of carbon source polymer, pore-forming agent, metal M source and sulfur source in the precursor solution of step (S1) is 1:(0.1-2):(0.01-0.5):(0.01-1), for example 1:(1-2):(0.05-0.2):(0.05-0.8), such as 1:(1-1.5):(0.08-0.15):(0.1-0.5).

[0017] In some embodiments of the present invention, the sulfur source is selected from thiourea.

[0018] According to an embodiment of the invention, when the carbon fiber material is further doped with carbon, the precursor solution in step (S1) also includes a carbon source; the carbon source is selected from urea.

[0019] According to an embodiment of the invention, when the carbon fiber material is further doped with carbon, the mass ratio of carbon source polymer, pore-forming agent, metal M source and carbon source in the precursor solution of step (S1) is 1:(0.1-2):(0.01-0.5):(0.01-1), for example 1:(1-2):(0.05-0.2):(0.05-0.8), such as 1:(1-1.5):(0.08-0.15):(0.1-0.5).

[0020] According to an embodiment of the invention, the solvent is an amide solvent, such as N,N-dimethylformamide.

[0021] According to an embodiment of the invention, the mixing in step (S1) is carried out by stirring and mixing at 40-80°C for 1-36 hours, for example, stirring and mixing at 50-75°C for 10-20 hours.

[0022] According to the embodiment of the invention, the process parameters for electrospinning in step (S2) are: positive voltage 15-25 kV, injection speed 0.05-0.15 mm / min.

[0023] In some embodiments of the present invention, the process parameters for electrospinning in step (S2) are: positive voltage 16-20kV, injection speed 0.05-0.15 mm / min, receiving distance 13-17 cm, and ambient humidity <30%.

[0024] According to the embodiment of the invention, in step (S3), the nanofiber membrane obtained in step (2) is dried before pre-oxidation, specifically by placing the nanofiber membrane obtained in step (2) in a 40-70℃ forced-air drying oven for 1-24 hours.

[0025] According to an embodiment of the invention, the oxygen-containing atmosphere in step (S3) is an air atmosphere.

[0026] According to the embodiment of the invention, the pre-oxidation temperature in step (S3) is 240-280°C, and the pre-oxidation time is 0.5-5h, for example, 1-3h.

[0027] According to an embodiment of the invention, the heating rate of the pre-oxidation in step (S3) is 0.5-5℃ / min, for example 1-3℃ / min.

[0028] According to the embodiment of the invention, the mass ratio of the pre-oxidized fiber material to cyanuric acid in step (S4) is 1:(2-50), for example 1:(5-25), such as 1:(10-20).

[0029] According to the embodiment of the invention, the high-temperature carbonization in step (S4) is to keep the temperature at 800-1200°C for 0.5-5 hours, for example, to keep the temperature at 900-1100°C for 1-3 hours.

[0030] According to the embodiment of the invention, in step (S4), the temperature is increased to 900-1100°C at a rate of 3-8°C / min and held at that temperature for 1-3 hours.

[0031] According to an embodiment of the invention, the method includes the following steps: (1) Preparation of precursor solution: The carbon source polymer, pore-forming agent, nickel source and sulfur source are mixed with solvent at a mass ratio of 1:(1-10):(0.001-0.1):(0.01-1) and stirred at 60-70°C to form a spinning solution; wherein, the carbon source polymer is polyacrylonitrile; the pore-forming agent is one of polymethyl methacrylate, polystyrene, zinc oxide and / or cadmium chloride; the nickel source is nickel chloride; the sulfur source is thiourea; and the solvent is N,N-dimethylformamide; (2) Electrospinning: The spinning solution obtained in step (1) is electrospinned to obtain a polymer nanofiber film; the electrospinning process parameters include: positive voltage 16-20 kV, injection speed 0.05-0.15 mm / min, receiving distance 13-17 cm, and ambient humidity <30%; (3) Pre-oxidation stabilization: The fiber film obtained in step (2) is pre-oxidized in air at 240-280℃ for 0.5-3h; this step cross-links and cyclizes the linear polymer chains, realizing the transformation from thermoplastic to thermosetting, and ensuring that the fiber morphology does not melt and collapse during subsequent high-temperature carbonization. (4) Simultaneous carbonization and defect construction: The fiber after pre-oxidation in step (3) and cyanuric acid are placed together in a tube furnace and carbonized at high temperature under nitrogen. The cyanuric acid is placed upstream of the gas flow and the fiber material is placed downstream. During the carbonization process, the temperature is increased to 900-1100℃ at a rate of 3-8℃ / min and held for 1-3 hours. During this process, the polymer is carbonized into a conductive N-doped carbon skeleton, the nickel species are reduced and anchored, and the sulfur source is decomposed to achieve S doping. The cyanuric acid decomposes during the heating process and continuously releases small molecule gases such as NH3 and CO2. These gases act as "molecular scalpels" at high temperature, producing in-situ etching and "shearing" effects on the growing carbon lattice, thereby creating high-density carbon vacancy defects in the carbon fiber simultaneously and directly.

[0032] The present invention also provides carbon fiber materials prepared by the method described above.

[0033] This invention provides the use of the carbon fiber material described above as a catalyst in an electrochemical system to convert CO2 into CO.

[0034] According to an embodiment of the invention, the catalyst converts CO2 into CO in a low-concentration oxygen-containing CO2 system.

[0035] According to an embodiment of the invention, the electrochemical system converts CO2 into CO in a CO2 system with an oxygen content of 0-40%, for example, in a CO2 system with an oxygen content of 0.1-30%.

[0036] According to an embodiment of the invention, the electrochemical system converts CO2 into CO in a system with a CO2 concentration of 10% or more (e.g., 20% or more, 30% or more).

[0037] According to an embodiment of the invention, the electrochemical system includes an H-type electrolytic cell, a flow cell electrolytic system, or a rechargeable zinc-carbon dioxide (Zn-CO2) battery.

[0038] According to an embodiment of the invention, the flow cell electrolysis system operates at high current densities (>200 mA cm⁻¹). -2CO2 is converted to CO by catalysis (preferably continuous catalysis).

[0039] According to the embodiments of the invention, the carbon fiber catalyst can be directly used as the catalytic layer of the gas diffusion electrode, maintaining a CO Faraday efficiency of nearly 100% under high CO2 conversion.

[0040] According to an embodiment of the invention, the rechargeable zinc-carbon dioxide (Zn-CO2) battery uses carbon fiber material as the cathode, coupling CO2 reduction with zinc oxidation to simultaneously output electrical energy and produce CO. This catalyst enables the battery to cycle stably for extended periods in a flue gas atmosphere (e.g., 20% CO2, 10% O2).

[0041] Compared with the prior art, the carbon fiber material of the present invention has the following significant advantages: 1. “Structure-Active Site” Dual-Functional Synergistic Design: This invention creatively combines a macroscopic hierarchical porous structure for enhancing mass transfer, atomic-level carbon vacancy defects for enhancing CO2 adsorption and activation, and molecular-level Ni-N for inhibiting oxygen poisoning. X S Y The asymmetric active centers are integrated into one unit. This multi-scale synergistic design enables the catalyst to simultaneously address the dual challenges of low CO2 concentration (mass transfer limitation) and oxygen content (competitive reaction).

[0042] 2. Superior performance: The obtained catalyst exhibits CO Faradaic efficiency close to or exceeding 90% under high-purity CO2, low-concentration CO2 (20%) and high oxygen concentration (up to 30%) conditions. It also maintains 90 hours of operational stability in H-type electrolyzers and demonstrates an ultra-long operational stability of over 250 hours in Zn-CO2 batteries. Its performance is comprehensively superior to the undoped sulfur comparative sample.

[0043] 3. The preparation method is ingenious and efficient: The "gas molecule shearing" strategy is adopted, which utilizes the gas from CA decomposition to construct carbon vacancy defects in situ during carbonization. The carbon framework formation, heteroatom doping, defect introduction and metal anchoring are completed in one step. The process is simple and controllable, avoiding ultra-high temperature, highly corrosive reagents or complex post-processing, which is conducive to large-scale preparation.

[0044] 4. Broad application prospects: This catalyst can be directly used to treat industrial flue gas that has not been deeply purified, eliminating the expensive and energy-intensive CO2 purification and concentration steps. It provides a practical material solution for the direct conversion "from chimney to chemicals", with significant economic and social benefits.

[0045] Specifically, the carbon fiber material of the present invention has the following advantages: (1) Hierarchical porous and multi-channel fiber structure: The fiber has long-range through-holes composed of mesopores and micropores, forming a "nano-sponge" structure, which provides an ideal three-dimensional mass transfer channel for the rapid diffusion, enrichment and capture of low-concentration CO2.

[0046] (2) High-density carbon vacancy defect network: The carbon skeleton is rich in intrinsic carbon vacancy defects. These defects serve as high-energy adsorption sites to enhance CO2 capture, and also optimize the catalytic pathway by modulating the electronic structure of neighboring metal species.

[0047] (3) Asymmetric Ni-N X S Y Active center: The successful doping of S atoms broke the traditional symmetrical Ni-N4 configuration, forming a Ni-N core with Ni single atoms as the core. X S Y Asymmetric coordination structure. This structure is key to endowing the catalyst with high oxygen tolerance, as its electronic structure is modulated to preferentially adsorb and activate CO2 molecules, while significantly inhibiting its reductive activity towards O2.

[0048] In summary, the carbon fiber material of this invention can enrich carbon dioxide in low CO2 concentration, oxygen-containing industrial flue gas environments, and can efficiently and stably electrocatalytically reduce CO2 to CO, thus possessing great potential for practical applications. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the preparation process of the carbon fiber material of the present invention.

[0050] Figure 2 The adsorption-desorption curves of the carbon fiber materials prepared in Comparative Example 2 and Comparative Example 3 were measured under CO2 atmosphere. Figure 2 a) and aperture distribution map ( Figure 2 (b) and the adsorption-desorption curves of the carbon fiber material prepared in Example 1 under CO2 atmosphere ( Figure 2 c) and nitrogen adsorption-desorption curves ( Figure 2 (d).

[0051] Figure 3 Scanning electron microscope (SEM) images of the carbon fiber materials prepared in Comparative Example 2 and Example 1.

[0052] Figure 4 The graph shows the long-term electrolytic stability test of the carbon fiber material prepared in Example 1 under a high-purity CO2 atmosphere, and the comparison graph shows the CO Faraday efficiency of the carbon fiber materials prepared in Example 1, Example 2 and Comparative Example 1 under different 90% CO2 concentrations and 10% O2 concentrations.

[0053] Figure 5This is a comparison chart of the CO Faraday efficiency of the carbon fiber material prepared in Example 1 under different CO2 and O2 concentrations.

[0054] Figure 6 This is a test diagram of the long-term electrolytic stability of the carbon fiber material prepared in Example 1 under a simulated flue gas atmosphere.

[0055] Figure 7 The graph shows the power density and CO Faraday efficiency of the carbon fiber material prepared in Example 1 in a Zn-CO2 battery.

[0056] Figure 8 The graph shows the charge-discharge cycle performance of a Zn-CO2 battery assembled using the carbon fiber material prepared in Example 1 as the cathode in an oxygen-containing atmosphere. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0058] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0059] Example 1: Ni-NS@TCNF S Preparation (1) Weigh 1.0 g of polyacrylonitrile (PAN), 1.0 g of polymethyl methacrylate (PMMA), 0.05 g of NiCl2·6H2O, 0.388 g of CdCl2 and 0.3 g of thiourea and dissolve them in 10 mL of DMF. Stir magnetically at 65 °C for 12 hours to obtain a uniform, pale yellow, viscous precursor solution.

[0060] (2) The precursor solution obtained in step (1) is loaded into the electrospinning machine syringe, the positive voltage is set to 19 kV, the negative voltage to 1 kV, the injection speed to 0.08 mm / min, the distance from the needle to the roller receiver to 15 cm, the roller speed to 140 rpm, the ambient temperature to 35℃, the humidity to <20%, and the spinning is carried out for 10 hours to obtain a white nanofiber membrane.

[0061] (3) The nanofiber membrane obtained in step (2) was dried overnight in a 60°C forced-air drying oven, and then placed in a muffle furnace and heated to 260°C at 1°C / min in an air atmosphere and kept at the temperature for 120 minutes for pre-oxidation to obtain a pre-oxidized membrane.

[0062] (4) Weigh 0.6 g of the pre-oxidized film obtained in step (3) and 10 g of cyanuric acid (CA) and place them in the downstream and upstream regions of the gas flow in the tube furnace, respectively. Under N2 atmosphere, heat to 1000℃ at 5℃ / min and hold for 120 minutes to carry out carbonization and defect construction.

[0063] (5) After the furnace temperature has cooled naturally to room temperature, the sample is taken out to obtain carbon fiber material, denoted as Ni-NS@TCNF. S .

[0064] Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the obtained materials are as follows: Figure 3 As shown. By Figure 3 It can be seen that the obtained material has a three-dimensional fiber network and a multi-level pore structure.

[0065] Example 2: Ni-N@TCNF S Preparation The steps are basically the same as in Example 1, except that 0.3 g of thiourea is replaced with 0.3 g of urea in the precursor preparation, while other steps and parameters remain unchanged. The resulting carbon fiber material is denoted as Ni-N@TCNF. S .

[0066] Comparative Example 1: NS@TCNF S Preparation The steps are basically the same as in Example 1, except that NiCl2·6H2O is not added in the precursor preparation, while other steps and parameters remain unchanged. The resulting carbon fiber material is denoted as NS@TCNF. S .

[0067] Comparative Example 2: Ni / TCNF S Preparation of -10CA (1) Weigh 1.0 g PAN, 1.0 g PMMA, and 0.05 g NiCl2·6H2O and dissolve them in 10 mL DMF. Stir magnetically at 60 °C for 12 hours to obtain a uniform green and transparent precursor solution.

[0068] (2) The precursor solution obtained in step (1) was loaded into the electrospinning machine syringe, the positive voltage was set to 19 kV, the negative voltage to 2.5 kV, the injection speed to 0.1 mm / min, the distance from the needle to the roller receiver to 15 cm, the roller speed to 140 r / min, the ambient temperature to 35℃, and the spinning was carried out for 7 hours to obtain a white nanofiber membrane.

[0069] (3) After drying the nanofiber membrane obtained in step (2), pre-oxidize it in air at 1℃ / min to 260℃ for 60 minutes.

[0070] (4) Weigh 0.4 g of the pre-oxidized film obtained in step (3) and 10 g of cyanuric acid (CA) and place them upstream and downstream of the gas flow in the tube furnace, respectively. Under N2 atmosphere, heat to 1000℃ at 5℃ / min and hold for 120 minutes to perform carbonization and gas molecule shearing to construct carbon vacancy defects.

[0071] (5) The carbonized sample was ground, acid-washed in 2 M hydrochloric acid solution at 70°C for 10 hours, washed and dried to obtain the catalyst, denoted as Ni / TCNF. S -10CA. Scanning electron microscope (SEM) images of the obtained material are shown below. Figure 3 As shown. By Figure 3 It is evident that the obtained material possesses a three-dimensional fiber network and a hierarchical porous structure. Furthermore, this material is rich in carbon vacancy defects and hierarchical channels generated by CA etching, but the active centers are traditional Ni-N. x The structure can be used to compare and test the unique contribution of sulfur doping to oxygen tolerance.

[0072] Comparative Example 3: Ni / TCNF S The preparation steps are basically the same as those of Comparative Example 2, except that cyanuric acid (CA) is not added in step (4), and the pre-oxidized film is carbonized under N2 atmosphere using the same procedure. The resulting carbon fiber material is denoted as Ni / TCNF. S This carbon fiber material was used to demonstrate that the catalyst's ability to enrich low-concentration CO2 and its intrinsic activity would significantly decrease in the absence of "gas molecule shearing" to introduce carbon vacancy defects.

[0073] Performance Test Examples The carbon fiber materials prepared in Examples 1 and 2 and Comparative Examples 1, 2 and 3 were subjected to performance evaluation. 1. Analysis of CO2 adsorption capacity and defect enrichment effect CO2 adsorption-desorption testing is a direct method for evaluating a material's affinity for CO2 molecules and its ability to fill micropores. This is illustrated by the Ni / TCNF prepared in Comparative Example 2. S Ni / TCNF prepared by -10CA and Comparative Example 3 S CO2 adsorption-desorption performance was tested. The Ni / TCNF prepared in Comparative Example 2... S Under the test conditions (195 K, 6 hours), the CO2 adsorption capacity of -10CA reached 174.01 cm⁻¹. 3 / g. Its adsorption isotherm shows a rapid upward trend in the low-pressure region (P / P0 < 0.02), indicating the presence of a large number of ultramicropores (<0.7 nm) and high-energy adsorption sites matching the size of CO2 molecules in the material. Comparative Example 3 prepared Ni / TCNF S The CO2 adsorption capacity was significantly lower under the same conditions, at 66.54 cm⁻¹.3 / g, and the adsorption capacity increases slowly in the low-pressure region. This comparative data indicates that the carbon vacancy defects generated by in-situ etching of cyanuric acid (CA) decomposition gas are the direct cause of the large number of micropores and high-energy surface sites in the material. These defect-formed nanospaces are highly matched with the kinetic diameter of CO2 molecules (0.33 nm), resulting in stronger van der Waals force overlap, thus exhibiting a stronger physical adsorption affinity for CO2. The Ni-NS@TCNF prepared in Example 1... S CO2 adsorption-desorption performance tests and nitrogen adsorption-desorption performance tests were conducted. The test results are as follows: Figure 2 As shown in c and d. The results indicate that the Ni-NS@TCNF prepared in Example 1... S It possesses a large specific surface area and strong carbon dioxide adsorption capacity, and numerous micropores are formed on the fibers. That is, the carbon fiber material obtained after sulfur doping in this invention exhibits stronger CO2 physical adsorption affinity and specific surface area. The above test results demonstrate that the "gas molecule shearing" strategy used in the preparation of carbon fiber materials in this invention effectively constructs an active interface in the material structure capable of efficiently enriching and concentrating CO2 molecules, which is more beneficial for the subsequent electrocatalytic conversion of CO2 by the material.

[0074] 2. H-type electrolytic cell test: 2.5 mg of catalyst sample was mixed with 300 µL of ethanol and 50 µL of Nafion-117 solution and sonicated for 30 min to obtain a uniform ink. 100 µL of the ink was then evenly spread on a 1×1 cm² surface. 2 The gas diffusion layer was dried overnight. The powdered catalyst was loaded at a concentration of approximately 0.7 mg / cm³ on the gas diffusion layer. -2 At 25°C and one atmosphere, the working electrode uses a catalyst-supported electrode, and the counter electrode is 1×1 cm. 2 A platinum sheet electrode and an Ag / AgCl reference electrode were used, with the two cells separated by a proton exchange membrane. 30 mL of 0.5 M KHCO3 electrolyte was added to both the cathode and anode. The cathode gas flow rate was controlled at 15 mL / min using a mass flow meter, and CO2 was continuously introduced for 20 min until saturation was reached, after which electrochemical tests were performed. The Ni-NS@TCNF prepared in Example 1... S Within the potential range of -0.7 V to -0.8 V (vs. RHE), the CO Faraday efficiency (FE) CO The efficiency reaches 100%; in a CO2 atmosphere containing 10% O2, its FE CO It maintains over 99% efficiency within the range of -0.65 V to -0.75 V. After continuous electrolysis for 55 hours at -0.8 V, FE... CO The content remained stable at over 90%. Meanwhile, the Ni-N@TCNF prepared in Example 2... SThe catalyst's performance deteriorates significantly under oxygen-containing conditions. Figure 4 ).

[0075] 3. Performance testing of the oxygen resistance system: The oxygen resistance of the carbon fiber material was tested in an H-type electrolytic cell. The working electrode used was Ni-NS@TCNF loaded with the material prepared in Example 1. S The self-made electrode and counter electrode are 1×1 cm. 2 A platinum sheet electrode and an Ag / AgCl reference electrode were used, with the two cells separated by a proton exchange membrane (Nafion). 30 mL of 0.5 M KHCO3 electrolyte was added to both the cathode and anode. The cathode gas flow rate was controlled at 30 mL / min using a mass flow meter. High-purity CO2 (99.99%) and high-purity O2 (99.99%) were mixed to achieve O2 concentrations of 0%, 10%, 20%, 30%, and 40%, respectively. Electrochemical performance was tested after continuously introducing the mixed gas for 20 min. The results showed that even at oxygen concentrations as high as 40%, the Ni-NS@TCNF prepared in Example 1... S It still has good catalytic performance. Figure 5 In other words, the carbon fiber material of the present invention has excellent oxygen resistance.

[0076] 4. Simulated Flue Gas Test: The test system was consistent with the H-type electrolytic cell system. High-purity CO2 (99.99%), high-purity O2 (99.99%), and high-purity N2 (99.99%) were mixed to achieve CO2, O2, and N2 concentrations of 20%, 10%, and 70%, respectively. After continuously introducing the mixed gas for 20 min, various electrochemical performance tests were performed. In a simulated flue gas of 20% CO2 + 10% O2 + 70% N2, at a potential of -0.7 V, the Ni-NS@TCNF prepared in Example 1... S FE CO The selectivity is 90%, and it can maintain more than 85% selectivity during 90 hours of constant potential electrolysis. Figure 6 The selectivity of the carbon fiber materials prepared in Example 2 and Comparative Example 1 was much lower than 10 hours.

[0077] 5. Zn-CO2 battery test: In a typical H cell, 0.11 g of zinc acetate and 30 mL of 6 mol KOH solution were added to the anode, and 30 mL of 1 mol KHCO3 solution was added to the cathode. A 2×2 cm⁻¹ galvanometer was used. 2 A zinc sheet electrode was used as the positive electrode. 4.5 mg of Ni-NS@TCNF prepared in Example 1 was taken. S As a catalyst, 420 µL of ethanol and 30 µL of Nafion solution were mixed and sonicated for 30 min to obtain a uniform ink. 100 µL of this ink was then evenly spread on a 1×1 cm² surface.2 The self-made electrode was dried overnight and used as the negative electrode. Open-circuit voltage, charge-discharge curve testing, charge-discharge cycle testing, and multi-stage current discharge (iStep) testing were performed. Gas chromatography was used to examine the reaction products to test whether the carbon fiber material of this invention also exhibited good reduction performance in the battery system. The Ni-NS@TCNF prepared in Example 1 was used. S A neutral aqueous Zn-CO2 battery was assembled for the cathode. In a high-purity CO2 atmosphere, the battery achieved a peak power density of 2.79 mW / cm². -2 FE CO The efficiency was 96.62%, and it could be stably cycled for 180 hours (659 cycles). In a CO2 atmosphere containing 10% O2, the peak power density was 3.39 mW / cm². -2 ( Figure 7 ), FE CO The success rate was 94.04%, and the stable cycle time was extended to 245 hours (882 cycles). Figure 8 It exhibits excellent oxygen tolerance and stability.

[0078] The above test results demonstrate that this invention, through a unique "gas molecule shearing" preparation method, successfully prepared materials with hierarchical porosity, carbon vacancy defects, and Ni-N composites. X S Y Carbon fiber materials with asymmetric active centers can enrich carbon dioxide in low-concentration, oxygen-containing industrial flue gas environments and can efficiently and stably electrocatalytically reduce CO2 to CO, possessing great potential for process applications.

[0079] The exemplary embodiments of the present invention have been described above. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon fiber material, characterized in that, It is a nitrogen-doped porous carbon material rich in carbon vacancy defects, wherein single atoms and / or nanoclusters of metal M are anchored therein; the porous carbon material has a three-dimensional carbon nanofiber network structure. The metal M is selected from at least one of nickel, iron, or cobalt.

2. The carbon fiber material according to claim 1, characterized in that, The carbon fiber material is further doped with carbon or sulfur, and is a porous carbon material rich in carbon vacancy defects, co-doped with carbon or sulfur and nitrogen, wherein single atoms and / or nanoclusters of metal M are anchored therein; the porous carbon material has a three-dimensional carbon nanofiber network structure. The metal M is selected from at least one of nickel, iron, or cobalt.

3. The carbon fiber material according to claim 1 or 2, characterized in that, The carbon fiber material has one or more of the following properties: (1) Hierarchical porous and multi-channel fiber structure: The fiber has long-distance through-holes composed of mesopores and micropores, forming a "nano-sponge" structure. (2) High-density carbon vacancy defect network: The carbon framework is rich in intrinsic carbon vacancy defects; (3) Asymmetric Ni-N X S Y Active center: The doping of S atoms breaks the traditional symmetrical Ni-N4 configuration, forming a Ni-N core with Ni single atoms as the core. X S Y Asymmetric coordination structure.

4. The method for preparing the carbon fiber material according to any one of claims 1-3, characterized in that, Includes the following steps: (S1) Preparation of precursor solution: The carbon source polymer, pore-forming agent, metal M source and solvent are mixed to form a spinning solution; (S2) Electrospinning: The spinning solution obtained in step (S1) is electrospinned to obtain a polymer nanofiber film; (S3) Pre-oxidation stabilization: The fiber film obtained in step (S2) is subjected to pre-oxidation treatment at 220-280°C in an oxygen-containing atmosphere; (S4) Simultaneous carbonization and defect construction: The fiber material pre-oxidized in step (S3) and cyanuric acid are placed together in a tube furnace and carbonized at high temperature under an inert atmosphere; the cyanuric acid is placed upstream of the gas flow and the fiber material is placed downstream. The carbon source polymer is selected from at least one of polyacrylonitrile, polyamide, polyvinylpyrrolidone, polyacrylonitrile-based composite materials, or biomass-derived nitrogen-containing polymers. The pore-forming agent is selected from at least one of polymers or inorganic salts that can be decomposed and / or volatilized at high temperature in step (S3) pre-oxidative stabilization and / or step (S4) carbonization and defect synchronous construction steps. The metal source is at least one of a soluble nickel salt, a soluble iron salt, or a soluble cobalt salt.

5. The preparation method according to claim 4, characterized in that, The carbon source polymer mentioned in step (S1) is polyacrylonitrile; Preferably, the pore-forming agent in step (S1) is selected from at least one of polymethyl methacrylate, polylactic acid, polyvinyl alcohol, polystyrene, zinc oxide, and cadmium chloride; Preferably, the nickel source in step (S1) is nickel chloride; Preferably, in step (S1), the mass ratio of the carbon source polymer, the pore-forming agent, and the metal M source is 1:(0.1-2):(0.01-0.5). Preferably, when the carbon fiber material is further doped with sulfur, the precursor solution in step (S1) further includes a sulfur source; the sulfur source is selected from sulfur-containing organic compounds and / or inorganic sulfides; Preferably, when the carbon fiber material is further doped with sulfur, the mass ratio of carbon source polymer, pore-forming agent, metal M source and sulfur source in the precursor solution of step (S1) is 1:(0.1-2):(0.01-0.5):(0.01-1). Preferably, the sulfur source is selected from thiourea; Preferably, the solvent is an amide solvent; Preferably, the mixing in step (S1) is carried out by stirring at 40-80°C for 1-36 hours.

6. The preparation method according to claim 4 or 5, characterized in that, The electrospinning process parameters in step (S2) are: positive voltage 15-25 kV, injection speed 0.05-0.15 mm / min.

7. The preparation method according to any one of claims 4-6, characterized in that, In step (S3), the nanofiber membrane obtained in step (2) is dried before pre-oxidation; Preferably, the oxygen-containing atmosphere in step (S3) is an air atmosphere; Preferably, the pre-oxidation temperature in step (S3) is 240-280℃, and the pre-oxidation time is 0.5-5h; Preferably, the heating rate of the pre-oxidation in step (S3) is 0.5-5℃ / min.

8. The preparation method according to any one of claims 4-7, characterized in that, In step (S4), the mass ratio of the pre-oxidized fiber material to cyanuric acid is 1:(2-50). Preferably, the high-temperature carbonization in step (S4) is carried out at 800-1200°C for 0.5-5 hours; Preferably, in step (S4), the temperature is increased to 900-1100°C at a rate of 3-8°C / min and held at that temperature for 1-3 hours.

9. The use of the carbon fiber material according to any one of claims 1-3 as a catalyst in an electrochemical system to convert CO2 into CO.

10. The use according to claim 9, wherein, The electrochemical system includes an H-type electrolytic cell, a flow cell electrolytic system, or a rechargeable zinc-carbon dioxide battery.

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