A method for preparing a Mg-CO2 battery catalyst material

Abstract

The application discloses a preparation method of a Mg-CO2 battery catalyst material. First, MBenes nanosheets and COFs nanosheets modified by alkali metal ions are subjected to intercalation treatment to make the two closely combined to form a composite carrier, and then the composite carrier is combined with a Ga-In-Sn alloy obtained by laser melting technology to obtain the Mg-CO2 battery catalyst material. The preparation method is simple, the process is easy to control, and is suitable for large-scale industrial production. The catalyst material prepared by the method has a high specific surface area, good electrical conductivity and thermal stability. When the catalyst material is applied to a Mg-CO2 battery, the cycle performance of the battery can be significantly improved, and the battery can still maintain a high capacity after multiple charge-discharge cycles, and the service life of the battery is long.

Description

Technical Field

[0001] This invention belongs to the field of magnesium-carbon dioxide batteries and relates to a method for preparing Mg-CO2 battery catalyst materials. Background Technology

[0002] Meeting the ever-growing energy demands of human society and addressing the environmental problems arising from the excessive consumption of fossil fuels are key issues that need to be resolved to achieve sustainable development. Excessive consumption of fossil fuels typically leads to excessive carbon dioxide emissions, accelerating global warming. Therefore, in recent years, academia and industry have been vigorously developing new energy systems to reduce carbon dioxide emissions and convert it into valuable chemicals. Currently, in exploring systems for carbon dioxide emission reduction and utilization, rechargeable metal-carbon dioxide batteries demonstrate significant advantages in effective emission reduction, CO2 value-added conversion, and high-performance energy storage. Therefore, rechargeable Mg-CO2 batteries are considered a "two birds with one stone" strategy and have become a research hotspot in the fields of CO2 emission reduction and electrochemical energy storage. However, alkali metals have high reactivity and are prone to dendrite formation during cycling, leading to serious battery safety issues, which shortens battery cycle life and limits practical applications. Therefore, researching magnesium, which has relatively low reactivity and is dendrite-free, as the negative electrode for Mg-CO2 batteries is crucial for their development.

[0003] Chinese invention patent application No. 201410500300.6 discloses a graphene-FeOF cathode composite material and its preparation method. The method involves mixing the materials and then reacting them in a water bath to form a solid-liquid mixture. This material is the first to synthesize FeOF from iron fluoride and graphene oxide. Graphene oxide acts as both a reactant and a conductive agent, increasing conductivity to some extent. However, the active sites in this composite material are uneven, the coordination degree is low, and the raw material, iron fluoride, is toxic and easily pollutes the environment.

[0004] Chinese Invention Patent No. 201610951729.6 discloses a two-dimensional transition metal carbide / nitride composite material with nano-sulfur particles, its preparation, and its application. This composite material consists of MXene nanosheets and nano-sulfur particles. The preparation method uses formic acid as a reducing agent to allow the generated nano-sulfur to grow uniformly on the surface of the MXene nanosheets. After neutralization, washing, and centrifugation, the MXene-sulfur particle composite material is obtained. This composite material has a high degree of integration, requires no binder or conductive agent, and has a simple process. However, it has poor thermal stability; sulfur is easily lost at high temperatures, affecting material properties, and is prone to side reactions and poor selectivity.

[0005] The paper “JOURNAL OF ELECTROCHEMISTRY 2019, 25(2):280” discloses a two-dimensional multilayer Ti3C2Tx Preparation and capacitance properties of MXene / polypyrrole nanowire composites were studied by loading one-dimensional polypyrrole nanowires onto Ti3C2T. x The two-dimensional surface of MXene effectively improves the self-stacking phenomenon of MXene, thereby enhancing capacitance performance. However, its material has a small specific surface area, low surface activity, and poor catalytic efficiency.

[0006] In summary, the main drawbacks of current metal-carbon dioxide batteries are:

[0007] First, the catalyst material composite is uneven, resulting in poor catalyst activity;

[0008] Second, the catalyst has poor stability and is sensitive to external conditions such as chemical reaction temperature and pH.

[0009] Third, the catalyst has low atom utilization and poor catalytic activity;

[0010] Fourth, the preparation process is too complicated and the cost is too high, making it difficult to apply on a large scale.

[0011] Based on this, the present invention aims to provide a catalyst material with high specific surface area, good electrical conductivity, and chemical and thermal stability. Summary of the Invention

[0012] To address the aforementioned technical problems, this invention aims to provide a method for preparing Mg-CO2 battery catalyst materials. First, MBENS nanosheets are intercalated with alkali metal ion-modified COFs nanosheets to form a composite support, which is then combined with a Ga-In-Sn alloy obtained through laser melting. This method is simple, easy to control, and suitable for large-scale industrial production. The resulting catalyst material exhibits high specific surface area, good electrical conductivity, and thermal stability. When applied to Mg-CO2 batteries, it significantly improves battery cycle performance, maintains high capacity even after multiple charge-discharge cycles, and extends battery life.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0014] A method for preparing a Mg-CO2 battery catalyst material comprises the following steps in sequence:

[0015] S1. Mix the MAB precursor powder with LiF and HCl evenly, centrifuge at 2000-4000 rpm for 1-2 h, filter, and dry at 80-100℃ for 10-12 h to obtain MBenes.

[0016] S2. Add acetic acid to the aldehyde monomer solution and react for 1-3 hours. Then add amino monomer solution and react for 24-48 hours to obtain a COF nanosheet mixture.

[0017] S3. After mixing the COFs nanosheet mixture with the alkali metal solution evenly, heat it in a water bath at 75-95℃ for 10-12h, filter it, and dry it at 80-100℃ for 10-12h to obtain alkali metal@COFs powder.

[0018] S4. After mixing Ga, In, and Sn in a mass ratio of 70:24.5:5.5, place the mixture in a reactor under an inert atmosphere, scan the molten metal with a femtosecond laser, cool it to room temperature at a rate of 500-3000℃ / min, and then sonicate it for 3-10 hours to obtain Ga. 70 In 24.5 Sn 5.5 alloy solution;

[0019] S5. The products obtained in steps S1 and S3 are immersed in the alloy solution obtained in step S4. After a pressurized reaction under an argon atmosphere, the mixture is filtered and dried to obtain MBENS-SA@COFs / Ga. 70 In 24.5 Sn 5.5 That is, Mg-CO2 battery catalyst material.

[0020] As a limitation of the preparation method of the present invention, in step S1, the MAB precursor is (Mo 2 / 3 Y 1 / 3 The MAB precursor is one of 2AlB2, Cr3AlB4, Fe2AlB2, and Mn2AlB2; the molar ratio of the MAB precursor to LiF and HCl is 1:(2-6):2.

[0021] As another limitation of the preparation method of the present invention, in step S2, the aldehyde monomer is tricarboxymethyl phloroglucinol or 2,5-dihydroxyterephthalaldehyde; the amino monomer is 2,5-diaminobenzenesulfonic acid or aminoguanidine hydrochloride.

[0022] As a third limitation of the preparation method of the present invention, in step S2, the molar ratio of acetic acid to aldehyde monomer and amino monomer is (2-4):1:(1-2).

[0023] As a fourth limitation of the preparation method of the present invention, in step S3, the alkali metal solution is one or more of Na2CO3, NaCl, NaNO3, Na3PO4, NaSO4, Li2CO3, LiCl, LiNO3, Li3PO4, LiSO4, K2CO3, KCl, KNO3, K3PO4, and K2SO4; the molar ratio of the COFs nanosheet mixture to the alkali metal solution is 1:(0.5-1.5).

[0024] As a fifth limitation of the preparation method of the present invention, in step S4, the laser power is 400W and the laser time is 2-10min.

[0025] The laser technology used in this invention is a femtosecond laser with a wide pulse width, which can suppress heat diffusion and avoid thermal damage while melting the metal substrate. Excessive power or time can cause local heat flux density to exceed the material's thermal conductivity, leading to liquid metal splashing, resulting in uneven alloy composition and reduced conductivity and catalytic activity. Conversely, insufficient power or time will prevent complete melting of the alloy, causing discontinuous conductive network filling, which in turn increases resistance and reduces charging and discharging efficiency during battery charging and discharging.

[0026] As a sixth limitation of the preparation method of the present invention, in step S5, the pressurized reaction is first pressurized from atmospheric pressure to 0.1-0.5 MPa and reacted for 5 min, and then heated to 150°C under atmospheric pressure and kept at that temperature for 14 h.

[0027] The composite of liquid metal and MBenzes-COFs was achieved via a two-step gradient pressure swing method. First, under argon pressure of 0.1–0.5 MPa, low-viscosity Ga... 70 In 24.5 Sn 5.5Liquid alloy preferentially penetrates the interlayer of MBENS. Its surface tension and fluidity effectively alleviate local stress in Mg-CO2 batteries during charging and discharging. Furthermore, Sn, due to its high melting point, can form microcrystalline nuclei under localized high pressure, briefly exhibiting solid-like properties. This prevents the COFs material from having its pores destroyed under subsequent high-temperature conditions due to insufficient thermal stability of the organic framework and differences in thermal expansion under normal pressure heating. If the pressure exceeds 0.5 MPa, excessive pressure will damage the organic framework structure of the COFs material, affecting its porous confinement effect. A reaction time of 5 minutes under argon pressure (0.1-0.5 MPa) is necessary to ensure sufficient penetration of the liquid alloy into the MBENS interlayer and the formation of a stable local structure. A reaction time less than 5 minutes results in insufficient penetration and fails to achieve the desired composite effect; a reaction time greater than 5 minutes leads to energy waste. Heating to 150℃ under normal pressure is done because this temperature promotes the interaction between the liquid metal and MBENS-COFs, allowing the liquid metal to better fill the interlayer spaces of MBENS and the channels of COFs, forming a more stable composite structure. Holding at this temperature for 14 hours ensures that the interaction is fully realized, allowing the material's structure and properties to reach their optimal state. If the holding time is less than 14 hours, the interaction will be insufficient, and the material's properties will be unstable; if the holding time is greater than 14 hours, it will lead to excessive aging of the material, affecting its performance.

[0028] As a seventh limitation of the preparation method of the present invention, in step S5, the drying temperature is 80-100℃ and the time is 10-12h.

[0029] In this invention, the liquid metal is composed of gallium (Ga), indium (In), and tin (Sn) in a mass ratio of 70:24.5:5.5. This ratio ensures that the alloy remains stable in a liquid state at room temperature, while also possessing low viscosity and high conductivity. Ga, as the base liquid medium, has a melting point of only 29.8°C and a viscosity as low as 1.99 mPa·s, ensuring rapid penetration of the liquid metal into the MBENS interlayer and COFNS pores during the pressurization process. During the charge and discharge process of Mg-CO2 batteries, the deposition and stripping of Mg triggers drastic volume changes. These volume changes generate strong stress within the material, leading to microstructural defects such as grain boundary propagation and crack initiation. If these defects are not repaired in time, they will gradually develop, eventually causing the active material to detach from the electrode surface, severely affecting the cycle stability of the battery. After Ga rapidly penetrates into the MBENS interlayer and COFNS pores, its excellent fluidity and unique physicochemical properties enable it to form a dynamic repair mechanism within the material. When micro-defects appear in a material, Ga can rapidly flow and fill these defect sites, effectively preventing further crack propagation. However, Ga₂O₃ readily forms on its surface in its liquid state, and is solid at room temperature, significantly reducing metal diffusion efficiency and generating ohmic impedance. The difference in atomic radius between indium (In) (R = 167 pm) and Ga (R = 135 pm) introduces lattice distortion, disrupting the regular oxidation process of Ga. This lattice distortion disrupts the regular arrangement of Ga atoms, inhibiting the continuous formation of Ga₂O₃, further reducing the barrier to Ga diffusion and thus decreasing ohmic impedance. The synergy of these two factors effectively improves the metal diffusion rate. Compared to Ga(4s⁻¹), Ga₂O₃… 2 4p 1 ) and In(5s 2 5p 1 ), the valence electron structure of the Sn atom (5s 2 5p 2 Ga-In alloys can provide more unpaired electrons, exhibiting strong adsorption for CO2. Through charge transfer, they further weaken the C=O bond, allowing the formation of the *MgCO3·5H2O intermediate state to overcome a smaller potential barrier, thereby lowering the reaction energy barrier of the rate-determining step *MgCO2→*MgCO3·xH2O. The incorporation of Sn effectively overcomes the low catalytic activity of Ga and In. However, pure Sn exhibits a volume expansion rate as high as 260% during charging, and this high expansion stress can pose a short-circuit risk within the battery. Ga-In alloys, in their amorphous liquid state at room temperature, can effectively absorb the expansion stress generated by Sn.

[0030] The doping of liquid metal enables the uniform distribution of Sn microcrystal nuclei between the MBENS layers. The Ga-In liquid matrix encapsulates the Sn nuclei to form a continuous liquid phase, creating a flexible liquid interlayer. The fluidity of the liquid metal allows it to dynamically fill micro-defects at grain boundaries or cracks caused by the dramatic volume expansion of Mg during deposition / exfoliation, blocking crack propagation paths, maintaining the integrity of the overall electrode structure, and preventing active material detachment. This effectively improves the strength of MBENS-COFs, ensuring battery cycle stability and slowing down cycle decay at high current densities. Furthermore, the Ga-In alloy wets the surface of the MBENS-COFs, increasing the electrolyte wetting rate, accelerating ion transport efficiency, and further improving conductivity.

[0031] The ion intercalation composite technology employed in this invention achieves effective intercalation through the Coulomb attraction between alkali metal ions and functional groups on the surface of MBenes. COFs, due to their periodically arranged nanopores and abundant functional groups, can immobilize alkali metal ions (Li₂O₃) through electrostatic adsorption or chemical bonding. + Na + K + This confinement effect ensures a uniform ion distribution, enabling the formation of uniform ionic bonds between the MBENS active surface and COFs, thereby creating a stable alternating composite structure. The use of alkali metal ions effectively avoids the strong electrostatic interactions caused by the excessively high charge density of high-valence metal ions, allowing them to occupy the active sites of MBENS-COFs and suppressing the drawbacks of liquid metal catalysis.

[0032] The MBEnes-SA@COFs / Ga prepared by this invention 70 In 24.5 Sn 5.5 The composite electrode material effectively leverages the high catalytic activity of MBEnes, the porous confinement effect of COFs, and the synergistic effect of the dynamic conductive network of liquid metal to achieve a reversible Mg-CO2 battery reaction. During discharge, Mg is released from the magnesium anode. 2+ Rapidly conducted via liquid metal to the MBenzes-COFs composite support, CO2 is reduced to MgCO3·5H2O+C by lowering the formation energy barrier of the *MgCO3·xH2O intermediate state. During charging, the nanocrystalline eutectic structure of the Ga-In-Sn liquid metal accelerates the decomposition of MgCO3·5H2O and the oxidative regeneration of C through a dynamic electron transport pathway, forming a reversible cyclic pathway with low overpotential. The overall reaction can be represented as... Sn has strong electron-donating properties, which can effectively weaken C=O, thereby reducing the potential barrier of CO2 during discharge and accelerating conductivity. Ga / In, as the conductive matrix and grid-modified metal respectively, form a liquid flexible protective layer in the gap of MBENS-COFs, effectively suppressing the solidification of Sn and absorbing the strain energy during cycling, thus effectively improving electrode life and enhancing cycling capability.

[0033] This invention employs a liquid metal composite MBenzes-COFs material. MBenzes-COFs form an interlayer composite framework through ion intercalation composite technology, possessing a large specific surface area, numerous active sites, and abundant ion channels. The liquid metal is formed into a nano-eutectic through laser melting, ensuring uniform bonding of the electrodes to the metal matrix and effectively compensating for volumetric strain in the Mg-CO2 battery during cycling. Simultaneously, the liquid metal effectively protects the electrode surface, forming an artificial SEI film, resulting in good cycle stability of the Mg-CO2 battery in acidic and alkaline environments. The laser process effectively shortens the process flow and improves synthesis efficiency.

[0034] The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0035] The above technical solution has the following advantages or beneficial effects:

[0036] 1. The preparation method of this invention is simple, the process is easy to control, and it is suitable for large-scale industrial production;

[0037] 2. The catalyst material prepared by this invention has high specific surface area, good electrical conductivity, and thermal stability;

[0038] 3. When the catalyst material prepared by this invention is applied to Mg-CO2 batteries, it can give the batteries good cycle performance.

[0039] This invention is applicable to the preparation of Mg-CO2 battery catalyst materials.

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0041] Figure 1 The image shows a SEM image of the catalyst material prepared in Example 1 of this invention.

[0042] Figure 2 The Ga prepared in step S4 of Example 1 of this invention 70 In 24.5 Sn 5.5 eutectic structure elemental distribution diagram;

[0043] Figure 3 The MBEnes-SA@COFs / Ga prepared in Example 2 of this invention 70 In 24.5 Sn 5.5 Macroscopic sample image;

[0044] Figure 4 The catalyst material prepared in Example 3 of this invention was used in a Mg-CO2 battery, and the battery operated at 200 mAg. -1 Charge-discharge curves at current density;

[0045] Figure 5 The catalyst material prepared in Example 4 of this invention is used in a Mg-CO2 battery, and the cycle performance of the battery at different current densities is shown in the figure.

[0046] Figure 6 The Ga prepared in Example 4 of this invention 70 In 24.5 Sn 5.5 SEM images of the eutectic structure at different scales. Detailed Implementation

[0047] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0048] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0049] Example 1

[0050] This embodiment prepares a Mg-CO2 battery catalyst material, and the preparation process and steps are as follows:

[0051] S1, 1 mol (Mo 2 / 3 Y 1 / 3 The AlB2 precursor powder was mixed with 2 mol LiF and 2 mol HCl, centrifuged at 2000 rpm for 1 h, filtered, and dried at 80 °C for 12 h to obtain Mo. 4 / 3 B2;

[0052] S2. Add 2 mol of acetic acid to 1 mol of trimethylolpropionate solution and react for 1 h. Then add 1 mol of aminoguanidine hydrochloride solution and react for 24 h to obtain a COF nanosheet mixture.

[0053] S3. Mix 1 mol COFs nanosheets with 0.5 mol Na2CO3 solution until homogeneous, heat in a water bath at 75℃ for 12 h, filter, and dry at 80℃ for 12 h to obtain Na@COFs powder.

[0054] S4. After mixing Ga, In, and Sn in a mass ratio of 70:24.5:5.5, the mixture is placed in a reactor under an inert atmosphere and melted using a femtosecond laser at a power of 400W for 2 minutes. The mixture is then cooled to room temperature at a rate of 500℃ / min and sonicated for 3 hours to obtain Ga. 70 In 24.5 Sn 5.5 alloy solution;

[0055] S5. The products obtained in steps S1 and S3 are immersed in the alloy solution obtained in step S4. Under an argon atmosphere, the pressure is first increased from atmospheric pressure to 0.1 MPa and reacted for 5 min. Then, the mixture is heated to 150°C under atmospheric pressure and held for 14 h. After filtration, the mixture is dried at 80°C for 12 h to obtain MBenes-COFs / liquid alloy, which is the Mg-CO2 battery catalyst material.

[0056] like Figure 1 The image shows a SEM image of the catalyst material prepared in this embodiment. As can be seen from the image, the liquid metal forms a spatial network, and Mo... 4 / 3 B2 forms an alternating structure with the COFs surface, with multiple defects, pores, and ion channels, which can provide Mg with... 2+ Efficient transport during battery cycling.

[0057] like Figure 2 The Ga prepared in step S4 of this embodiment is 70 In 24.5 Sn 5.5 The elemental distribution diagram of the alloy solution shows that Ga and In form the conductive matrix and the network-modifying metal, respectively, while Sn, as the conductive metal, exhibits good dispersion and fluidity, forming a dynamic conductive network.

[0058] Example 2

[0059] This embodiment prepares a Mg-CO2 battery catalyst material, and the preparation process and steps are as follows:

[0060] S1. Mix 1 mol of Cr3AlB4 precursor powder with 3 mol of LiF and 2 mol of HCl until homogeneous, centrifuge at 3000 rpm for 1.5 h, filter, and dry at 90℃ for 11 h to obtain Cr3B4.

[0061] S2. Add 3 mol of acetic acid to a 1 mol solution of 2,5-dihydroxyterephthalaldehyde and react for 2 h. Then add 1.5 mol of 2,5-diaminobenzenesulfonic acid and react for 36 h to obtain a COF nanosheet mixture.

[0062] S3. Mix 1 mol COFs nanosheet mixture with 1 mol LiCl solution until homogeneous, heat in a water bath at 85℃ for 11 h, filter, and dry at 90℃ for 11 h to obtain Li@COFs powder.

[0063] S4. After thoroughly mixing Ga, In, and Sn at a mass ratio of 70:24.5:5.5, the mixture is placed in a reactor under an inert atmosphere. The metal is melted using a nanosecond laser at a power of 400 W for 5 minutes. After cooling to room temperature at a rate of 1000℃ / min, the mixture is sonicated for 5 hours to obtain Ga. 70 In 24.5 Sn 5.5 alloy solution;

[0064] S5. The products obtained in steps S1 and S3 are immersed in the alloy solution obtained in step S4. Under an argon atmosphere, the pressure is first increased from atmospheric pressure to 0.2 MPa and reacted for 5 min. Then, the mixture is heated to 150°C under atmospheric pressure and held for 14 h. After filtration, the mixture is dried at 90°C for 11 h to obtain MBenes-COFs / liquid alloy, which is the Mg-CO2 battery catalyst material.

[0065] like Figure 3 The MBEnes-SA@COFs / Ga prepared in this embodiment is an example. 70 In 24.5 Sn 5.5 The macroscopic sample image shows that the system is uniformly mixed and has a good morphology.

[0066] Example 3

[0067] This embodiment prepares a Mg-CO2 battery catalyst material, and the preparation process and steps are as follows:

[0068] S1. Mix 1 mol Fe2AlB2 precursor powder with 4 mol LiF and 2 mol HCl evenly, centrifuge at 4000 rpm for 2 h, filter, and dry at 100℃ for 10 h to obtain Fe2B2.

[0069] S2. Add 4 mol of acetic acid to 1 mol of 2,5-dihydroxyterephthalaldehyde and react for 3 h. Then add 2 mol of aminoguanidine hydrochloride and react for 48 h to obtain a COF nanosheet mixture.

[0070] S3. Mix 1 mol COFs nanosheet mixture with 1.5 mol KNO3 solution until homogeneous, heat in a water bath at 95℃ for 10 h, filter, and dry at 100℃ for 10 h to obtain K@COFs powder.

[0071] S4. After uniformly mixing Ga, In, and Sn at a mass ratio of 70:24.5:5.5, the mixture is placed in a reactor under an inert atmosphere. The metal is melted using a nanosecond laser at a power of 400W for 10 minutes. After cooling to room temperature at a rate of 3000℃ / min, the mixture is sonicated for 10 hours to obtain Ga. 70 In 24.5 Sn 5.5 alloy solution;

[0072] S5. The products obtained in steps S1 and S3 are immersed in the alloy solution obtained in step S4. Under an argon atmosphere, the pressure is first increased from atmospheric pressure to 0.5 MPa and reacted for 5 min. Then, the mixture is heated to 150°C under atmospheric pressure and held for 14 h. After filtration, the mixture is dried at 100°C for 10 h to obtain MBenes-COFs / liquid alloy, which is the Mg-CO2 battery catalyst material.

[0073] like Figure 4 The catalyst material prepared in this embodiment is used in a Mg-CO2 battery, and the battery operates at 200 mAg. -1 The charge-discharge curves at current density show that the maximum number of cycles reaches 65, indicating excellent cycle performance.

[0074] Example 4

[0075] This embodiment prepares a Mg-CO2 battery catalyst material, and the preparation process and steps are as follows:

[0076] S1. Mix 1 mol of Mn2AlB2 precursor powder with 6 mol of LiF and 2 mol of HCl until homogeneous, centrifuge at 4000 rpm for 2 h, filter, and dry at 90℃ for 10 h to obtain Mn2B2.

[0077] S2. Add 4 mol of acetic acid to 1 mol of tricarboxymethyl phloroglucinol solution and react for 3 h. Then add 1 mol of 2,5-diaminobenzenesulfonic acid and react for 48 h to obtain a COFs nanosheet mixture.

[0078] S3. Mix 1 mol COFs nanosheet mixture with 0.5 mol NaSO4 solution, heat in a water bath at 75℃ for 12 h, filter, and dry at 80℃ for 10 h to obtain Na@COFs powder.

[0079] S4. After uniformly mixing Ga, In, and Sn at a mass ratio of 70:24.5:5.5, the mixture is placed in a reactor under an inert atmosphere. The metal is melted using a nanosecond laser with a power of 400 W for 5 minutes. After cooling to room temperature at a rate of 2000℃ / min, the mixture is sonicated for 3 hours to obtain Ga. 70 In 24.5 Sn 5.5 alloy solution;

[0080] S5. The products obtained in steps S1 and S3 are immersed in the alloy solution obtained in step S4. Under an argon atmosphere, the pressure is first increased from atmospheric pressure to 0.5 MPa and reacted for 5 min. Then, the mixture is heated to 150°C under atmospheric pressure and held for 14 h. After filtration, the mixture is dried at 100°C for 10 h to obtain MBenes-COFs / liquid alloy, which is the Mg-CO2 battery catalyst material.

[0081] like Figure 5 The graph shows the application of the catalyst material prepared in this embodiment in a Mg-CO2 battery. The comparison of the battery's cycle performance at different current densities shows that at 1000 mAg... -1 At high current densities, the number of cycles can reach 52, and the number of cycles decreases only slightly with increasing current density, demonstrating good cycle life.

[0082] like Figure 6 The Ga prepared in this embodiment 70 In 24.5 Sn 5.5 SEM images at 5, 10, and 20 μm show that the three metals form a nano-eutectic structure, with Sn microcrystals encapsulated by the Ga-In liquid system, forming irregular spherical clusters.

[0083] Comparative Example

[0084] To investigate the effects of different parameters and reactants on the performance of the product of this invention, the following comparative experiments were conducted. Different Mg-CO2 battery catalyst materials were prepared according to the following comparative examples:

[0085] Comparative Example 1

[0086] This comparative example prepares a Mg-CO2 battery catalyst material. The preparation process is similar to that of Example 1, except that in step S4, the mass ratio of Ga, In, and Sn is 70:10:20.

[0087] Comparative Example 2

[0088] This comparative example prepares a Mg-CO2 battery catalyst material. The preparation process is similar to that of Example 1, except that in step S4, the mass ratio of Ga, In, and Sn is 60:35:5.

[0089] Comparative Example 3

[0090] This comparative example prepares a Mg-CO2 battery catalyst material. The preparation process is similar to that of Example 1, except that in step S4, instead of using a Ga-In-Sn alloy, the following alloys or metallic elements are used:

[0091] Group A: Only Ga metal is used;

[0092] Group B: Only In metal is used;

[0093] Group C: Only Sn metal is used;

[0094] Group D: Using Ga-In alloys;

[0095] Group E: Use Ga-Sn alloy.

[0096] Comparative Example 4

[0097] This comparative example prepares a Mg-CO2 battery catalyst material. The preparation process is similar to that of Example 1, except that in step S3, ion intercalation technology is not used; instead, Mo is used... 4 / 3 B2 and COFs were mixed in a simple solution, and the rest of the process was the same as in Example 1.

[0098] Comparative Example 5

[0099] This comparative example prepares a Mg-CO2 battery catalyst material. The preparation process is similar to that of Example 1, except that in step S4, femtosecond laser technology is not used, but a conventional tube furnace is used to melt the Ga-In-Sn alloy.

[0100] Performance testing

[0101] The catalyst materials prepared in Examples 1-4 and Comparative Examples 1-5 of this invention were used as positive electrode catalysts in magnesium-carbon dioxide batteries, and their cycle performance was tested. The specific test results are shown in the table below:

[0102]

[0103]

[0104] As can be seen from the table above, when the catalyst materials prepared in Examples 1-4 of this invention are applied to magnesium-carbon dioxide batteries, their performance in a 200mAh g⁻¹ range is [missing information]. -1 and 1000mAh g -1 The cycling performance at current density is significantly better than that of comparative examples 1-5, which is attributed to the rational preparation process, the synergistic effect of each material, and the precise composition ratio of this invention. In terms of the preparation process, ion intercalation composite technology enables alkali metal ions to form a stable composite structure with MBEnes and COFs; laser melting technology precisely controls the formation of a nano-eutectic alloy; and a two-step gradient pressure switching method ensures a tight bond between the liquid metal and the composite support. Among the materials, the high catalytic activity of MBEnes, the porous confinement effect of COFs, and the unique properties of the liquid metal work synergistically. Ga constructs a conductive network, In inhibits oxidation, Sn promotes the reaction, and its expansion stress is absorbed by the Ga-In alloy. Regarding the composition ratio, from the molar ratio of the raw materials to the mass ratio of the liquid metal, everything is precisely set to ensure sufficient reaction and stable product performance, ultimately achieving a significant improvement in battery cycling performance. In Comparative Examples 1 and 2, the change in the liquid alloy ratio led to a decrease in battery performance. This was mainly due to excess Ga, which made it easier to oxidize into Ga2O3 solid. As an insulator, Ga2O3 covering the material surface hinders electron conduction, thus reducing conductivity. Excess Sn caused solidification at room temperature, resulting in the loss of the dynamic repair ability of the liquid metal. Insufficient In made it difficult to break the regular oxidation of Ga, increasing ohmic impedance. Similarly, excessive In increased surface viscosity, hindering liquid penetration. Insufficient Sn reduced CO2 adsorption sites, decreasing catalytic activity and thus leading to a decrease in battery performance. If a simple solution intercalation method was used (Comparative Example 4), the interlayer was only bound by van der Waals forces. During cycling, the MBene-COFs framework structure collapsed, failing to form a confinement effect. Uneven distribution of active materials resulted in a decrease in cycling performance (1000mAh g). -1 The number of cycles is only 35. If the alloy is melted in a traditional tube furnace (Comparative Example 5), the cooling rate is slower than that of the laser method, which gives Sn atoms enough time to diffuse and recombine, making it easy to form component segregation regions and preventing the formation of a eutectic structure. As a result, the conductive network inside the material is destroyed, the ion transport path is blocked, the active sites of the electrode material are reduced and unevenly distributed, and ultimately the battery performance is reduced.

[0105] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a Mg-CO2 battery catalyst material, characterized in that, Follow these steps in sequence: S1. Mix the MAB precursor powder with LiF and HCl evenly, centrifuge at 2000-4000 rpm for 1-2 h, filter, and dry at 80-100℃ for 10-12 h to obtain MBenes. S2. Add acetic acid to the aldehyde monomer solution and react for 1-3 hours. Then add the amino monomer solution and react for 24-48 hours to obtain a COF nanosheet mixture. S3. After mixing the COFs nanosheet mixture with the alkali metal solution evenly, heat it in a water bath at 75-95℃ for 10-12h, filter it, and dry it at 80-100℃ for 10-12h to obtain alkali metal@COFs powder. S4. After mixing Ga, In, and Sn in a mass ratio of 70:24.5:5.5, place the mixture in a reactor under an inert atmosphere, scan the molten metal with a femtosecond laser, cool it to room temperature at a rate of 500-3000℃ / min, and then sonicate it for 3-10 hours to obtain Ga. 70 In 24.5 Sn 5.5 alloy solution; S5. The products obtained in steps S1 and S3 are immersed in the alloy solution obtained in step S4. After a pressurized reaction under an argon atmosphere, the mixture is filtered and dried to obtain MBENS-SA@COFs / Ga. 70 In 24.5 Sn 5.5 That is, Mg-CO2 battery catalyst material.

2. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S1, the MAB precursor is (Mo 2 / 3 Y 1 / 3 The MAB precursor is one of 2AlB2, Cr3AlB4, Fe2AlB2, and Mn2AlB2; the molar ratio of the MAB precursor to LiF and HCl is 1:(2-6):

2.

3. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S2, the aldehyde monomer is tricarboxymethyl phloroglucinol or 2,5-dihydroxyterephthalaldehyde; the amino monomer is 2,5-diaminobenzenesulfonic acid or aminoguanidine hydrochloride.

4. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S2, the molar ratio of acetic acid to aldehyde monomer and amino monomer is (2-4):1:(1-2).

5. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S3, the alkali metal solution is one or more of Na2CO3, NaCl, NaNO3, Na3PO4, NaSO4, Li2CO3, LiCl, LiNO3, Li3PO4, LiSO4, K2CO3, KCl, KNO3, K3PO4, and K2SO4; the molar ratio of the COFs nanosheet mixture to the alkali metal solution is 1:(0.5-1.5).

6. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S4, the laser power is 400W and the laser time is 2-10min.

7. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S5, the pressurized reaction is first pressurized from atmospheric pressure to 0.1-0.5 MPa and reacted for 5 minutes, and then heated to 150°C under atmospheric pressure and kept at that temperature for 14 hours.

8. The method for preparing a Mg-CO2 battery catalyst material according to claim 1, characterized in that, In step S5, the drying temperature is 80-100℃ and the time is 10-12h.

Images