Application of NH2-MIL-101 (Fe)@CoPc composite catalyst in lithium-dielectric conductive nitrogen fixation

Abstract

The application belongs to the field of electrocatalytic nitrogen fixation and lithium metal battery interface catalysis crossing technology, and discloses application of an NH2-MIL-101 (Fe)@CoPc composite catalyst in lithium-mediated electrocatalytic nitrogen fixation. The composite catalyst is loaded on a carbon paper working electrode, and a three-electrode system is constructed by matching a platinum-based counter electrode and a reference electrode. Nitrogen is introduced into a non-aqueous electrolyte containing LiBF4, and a series of electrochemical tests are performed to realize nitrogen reduction to ammonia at normal temperature and pressure. Then, the ammonia is collected by dilute sulfuric acid, and the ammonia concentration is detected by an indophenol blue method to calculate the yield and Faraday efficiency. With the synergistic effect of the composite catalyst, Li + N2 enrichment and efficient activation of N≡N bond, while constructing a stable SEI film to inhibit lithium dendrites, significantly improving nitrogen fixation efficiency and system stability, simple and green process, providing a new practical solution for the landing of lithium-mediated nitrogen fixation technology.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of electrocatalytic nitrogen fixation and lithium metal battery interface catalysis. Specifically, it relates to the application of an NH2-MIL-101 (Fe)@CoPc composite catalyst in lithium-dielectric conductive catalytic nitrogen fixation, which is particularly suitable for a system that can efficiently and stably electrochemically reduce nitrogen to prepare ammonia at room temperature and pressure. Background Technology

[0002] Ammonia is a core raw material for the fertilizer industry, clean energy carriers, and the synthesis of fine chemicals. Currently, industrial ammonia synthesis mainly relies on the Haber-Bosch process, which requires operation under high temperature (400–500 ℃) and high pressure (150–300 atm) conditions, consuming 1–2% of global energy and accompanied by large amounts of CO2 emissions. This significantly contradicts the green and low-carbon development requirements under the "dual carbon" goal. Therefore, developing electrochemical nitrogen fixation technology that operates at ambient temperature and pressure, with low energy consumption and zero emissions has become a research hotspot in the global energy and catalysis fields.

[0003] Lithium-mediated electrocatalytic nitrogen fixation (Li-NRR) is a highly promising green route for ammonia synthesis. Its core principle involves the electrochemical deposition of metallic lithium to achieve efficient activation and reduction of N2 molecules in a non-aqueous system, ultimately leading to ammonia production via protonation. Compared to traditional aqueous electrocatalytic nitrogen fixation, this route avoids competition from hydrogen evolution side reactions, significantly improving nitrogen fixation selectivity and efficiency. However, key bottlenecks still exist in lithium-mediated nitrogen fixation systems:

[0004] 1. Uneven lithium deposition and lithium dendrite growth: During cycling, lithium metal is prone to forming dendrites, which can puncture the separator and cause safety hazards. At the same time, it leads to the irreversible consumption of active lithium, which significantly reduces the battery cycle life and energy efficiency.

[0005] 2. Poor stability of the solid electrolyte interface (SEI): Natural SEIs have complex compositions and fragile mechanical properties, making them prone to breakage and reconstruction during cycling. This makes them unable to effectively suppress side reactions and dendrite growth, and also hinders Li... + The efficient transport of N2 restricts reaction kinetics.

[0006] 3. Insufficient N2 activation and conversion efficiency: The N≡N triple bond energy is extremely high (941 kJ·mol⁻¹). -1 Traditional catalysts are difficult to activate efficiently, resulting in low ammonia generation rates and Faraday efficiencies, which are difficult to meet the requirements of industrial applications. Summary of the Invention

[0007] In view of this, the purpose of this invention is to overcome the defects in existing lithium-dielectric conductive catalytic nitrogen fixation technology, such as lithium dendrite growth, SEI interface instability, and low N2 activation efficiency, and to provide an application of NH2-MIL-101 (Fe)@CoPc composite catalyst in lithium-dielectric conductive catalytic nitrogen fixation. By extending the "spontaneous cascade optimization strategy driven by dual enrichment" of this composite material to electrocatalytic nitrogen fixation reaction, efficient and stable electrochemical ammonia synthesis can be achieved.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides the application of NH2-MIL-101 (Fe)@CoPc composite catalyst in lithium dielectric conductive catalytic nitrogen fixation and ammonia synthesis. The composite catalyst is loaded onto a carbon paper substrate to prepare a catalytic working electrode, and a three-electrode lithium dielectric conductive catalytic nitrogen fixation system is constructed. Nitrogen gas is introduced into a non-aqueous electrolyte to carry out an electrochemical reduction reaction, thereby realizing the directional conversion of nitrogen gas into ammonia.

[0010] The NH2-MIL-101(Fe)@CoPc composite catalyst is prepared by impregnation, using NH2-MIL-101(Fe) as the support and cobalt phthalocyanine (CoPc) as the active component, with a mass ratio of CoPc to NH2-MIL-101(Fe) of 5:60. In the three-electrode system, the counter electrode is a platinum mesh / platinum sheet, the reference electrode is a platinum wire with a diameter of 0.5 mm, and the non-aqueous electrolyte uses diethylene glycol dimethyl ether as the solvent, with lithium tetrafluoroborate as the lithium salt and ethanol as the proton additive. The electrochemical reduction reaction is achieved through combined electrochemical tests, including open circuit potential-time (OCPT) testing, cyclic voltammetry (CV) testing, secondary OCPT testing, linear sweep voltammetry (LSV) testing, and constant voltage-time (it) testing, to achieve nitrogen activation and reduction. At the same time, the composite catalyst regulates lithium deposition behavior, constructs a stable SEI interface, and inhibits lithium dendrite growth.

[0011] Beneficial effects:

[0012] 1. Synergistic catalysis enhances nitrogen fixation performance, significantly improving ammonia yield and Faraday efficiency;

[0013] The high specific surface area and adjustable pore structure of NH2-MIL-101 (Fe) enable the realization of Li +The interface enrichment with N2 molecules creates a high-concentration reaction microenvironment for nitrogen fixation, increasing the contact probability between the substrate and the active site. The macrocyclic conjugated electronic structure of CoPc and the cobalt metal active site can efficiently activate the high-bond-energy N≡N triple bond, significantly reducing the reaction energy barrier for nitrogen reduction. The synergistic effect of these two factors enables rapid adsorption, activation, and reduction of N2. Compared with single catalysts such as pure NH2-MIL-101 (Fe) and pure CoPc, the ammonia yield and Faradaic efficiency are significantly improved, and the charge utilization efficiency is significantly optimized.

[0014] 2. By regulating the behavior of the lithium metal interface, the stability and safety of the system are significantly improved;

[0015] In the composite catalyst, NH2-MIL-101 (Fe) can efficiently anchor electrolyte anions through Lewis acid-base interactions and hydrogen bonds, while CoPc, with its rich electronic structure, promotes anion decomposition and directional formation of a stable solid electrolyte interphase (SEI) film rich in LiF. This artificial SEI film can effectively inhibit the growth of lithium dendrites and the problem of membrane puncture, reduce the irreversible consumption of active lithium, solve the pain point of easy rupture and reconstruction of SEI film in traditional lithium-mediated nitrogen fixation system, and significantly improve the cycle stability and safety of the electrocatalytic system.

[0016] 3. The reaction conditions are mild, which aligns with the needs of green and low-carbon development;

[0017] This invention relies on the high efficiency of composite catalysts to achieve lithium-dielectric conductive nitrogen fixation and ammonia synthesis at room temperature and pressure, eliminating the need for the high temperature and high pressure conditions required by the traditional Haber-Bosch process, thus significantly reducing energy consumption in the production process; moreover, the entire reaction process is CO2 emission-free, reducing carbon emissions from the source of the process, which is in line with the current industrial development direction of green ammonia synthesis under the "dual carbon" goal.

[0018] 4. The catalyst is highly compatible with the application process, easy to operate, and has good repeatability;

[0019] The NH2-MIL-101 (Fe)@CoPc composite catalyst is prepared by impregnation, which is simple to operate, uses readily available raw materials, and has controllable product morphology and performance with good reproducibility. The spraying / drop coating loading process of the catalytic electrode is simple, and the electrolyte preparation, electrolytic cell assembly and electrochemical testing processes are highly standardized, requiring no complex special equipment, which facilitates the transformation of laboratory research into industrial applications.

[0020] 5. The ammonia collection and detection system is well-established, providing accurate results and easy operation;

[0021] This invention utilizes 0.05M dilute sulfuric acid to achieve efficient separation and collection of gaseous and solid-phase ammonia. Ammonia concentration is detected using the indophenol blue method and a UV-Vis spectrophotometer, with precise detection wavelengths set at 654nm, 655nm, and 656nm. A standard curve allows for rapid and accurate calculation of the actual ammonia production. The entire detection process requires no complex pretreatment, has a well-defined reagent preparation method, and exhibits good repeatability. It effectively supports the quantitative analysis of ammonia yield and Faraday efficiency, providing a reliable basis for evaluating catalytic performance.

[0022] 6. The catalyst exhibits excellent compatibility with lithium-mediated systems, expanding the application scenarios of composite catalysts;

[0023] This invention is the first to extend the "dual enrichment-driven spontaneous cascade optimization" strategy of the NH2-MIL-101 (Fe)@CoPc composite catalyst to the field of lithium-mediated electrocatalytic nitrogen fixation. It realizes the application extension of this composite catalyst from lithium metal battery interface modification to electrocatalytic ammonia synthesis, enriches the application scenarios of metal-organic framework-phthalocyanine cobalt composite catalysts, and also provides new ideas and directions for the design of catalysts for lithium-mediated nitrogen fixation systems.

[0024] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0025] Figure 1 The image shows the UV-Vis absorption spectra of various samples in the 500-800 nm wavelength range. Detailed Implementation

[0026] To make the technical solutions, advantages, and objectives of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of this application.

[0027] Example 1: Preparation of NH2-MIL-101(Fe)@CoPc composite catalyst

[0028] Preparation of S1. NH2-MIL-101 (Fe);

[0029] S1.1 Weigh 2.75g of ferric chloride hexahydrate and dissolve it in 40mL of N,N-dimethylformamide (DMF) to prepare solution A; weigh 1.105g of 2-aminoterephthalic acid and dissolve it in 40mL of DMF to prepare solution B.

[0030] S1.2 Sonicate solutions A and B for 15 minutes each. Under sonication, slowly add solution B to solution A and stir until a homogeneous mixture is formed.

[0031] S1.3 Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in a forced-air drying oven for constant heating at 110°C for 24 hours.

[0032] After the S1.4 reaction is complete, allow the product to cool naturally to room temperature, transfer it to a centrifuge tube, centrifuge at 10,000 rpm for 5 minutes, and collect the solid product.

[0033] S1.5 The solid product was washed three times with DMF and twice with anhydrous ethanol to remove unreacted raw materials and impurities. The washed product was placed in a vacuum drying oven and dried under vacuum at 60°C for 12 hours. After grinding, NH2-MIL-101 (Fe) powder was obtained and sealed for later use.

[0034] S2. Preparation of NH2-MIL-101 (Fe)@CoPc composite catalyst

[0035] S2.1 Weigh 5 mg of cobalt phthalocyanine (CoPc) and place it in a 50 mL single-necked flask. Add 40 mL of DMF and sonicate until CoPc is completely dissolved to obtain a DMF solution of CoPc.

[0036] S2.2 Add 60 mg of NH2-MIL-101 (Fe) powder prepared in step S1 to the above solution, stir evenly, place the single-necked flask in an oil bath, and immerse at a constant temperature of 75°C for 40 hours, during which time magnetic stirring is continuously performed.

[0037] After the S2.3 impregnation is completed, the DMF solvent in the system is removed by vacuum distillation to obtain solid residue.

[0038] S2.4 Transfer the solid residue to a centrifuge tube, add anhydrous ethanol, centrifuge and wash several times until the washing liquid is colorless, and collect the solid product.

[0039] S2.5 The solid product was placed in a vacuum drying oven and dried at 120℃ for 12 hours to obtain the NH2-MIL-101(Fe)@CoPc composite catalyst, which was then sealed and stored in the dark for later use.

[0040] Example 2 Preparation of the catalytic working electrode

[0041] Method 1: Spraying

[0042] 1. Carbon paper pretreatment: Cut carbon paper into 1cm×1.5cm pieces and immerse them in acetone, ethanol, ultrapure water, acetone, ethanol, ultrapure water, ethanol, ultrapure water, and ethanol in sequence. Ultrasonic cleaning is performed for 30 minutes in each solvent. After cleaning, place the paper in a vacuum drying oven to dry thoroughly for later use.

[0043] 2. Preparation of catalyst ink: Weigh 15 mg of the NH2-MIL-101 (Fe)@CoPc composite catalyst prepared in Example 1, place it in a centrifuge tube, add 3 mL of ethanol and 50 μL of naphthol, and sonicate for 30 minutes to form a uniformly dispersed catalyst ink.

[0044] 3. Spraying load: Place the pretreated carbon paper flat on the working electrode substrate, spray 100 μL of catalyst ink on the front side of the carbon paper with a spray gun, and after drying, spray another 100 μL of catalyst ink on the back side. After natural drying, the catalytic working electrode is obtained and ready for use.

[0045] Method 2: Drop-coating method

[0046] 1. Carbon paper pretreatment: Cut carbon paper into 1×1cm² pieces, activate it with mixed acid for 12 hours, then immerse it in acetone, ethanol and ultrapure water for ultrasonic cleaning for 15 minutes each, and vacuum dry it overnight at 60℃ for later use.

[0047] 2. Preparation of catalyst slurry: Weigh 4 mg of the composite catalyst prepared in Example 1, add 30 μL of 5 wt% Nafion solution and 970 μL of ethanol / water mixed solvent (V (ethanol):V (ultrapure water) = 51:49), and sonicate for 30 minutes to form a uniform slurry.

[0048] 3. Drop-coating loading: The catalyst slurry is drop-coated onto the pretreated carbon paper using a micropipette. The catalyst loading is 0.5 mg / mL. After coating, the carbon paper is irradiated with infrared light for 15-30 minutes until the surface is completely dry to obtain the catalytic working electrode, which can be used immediately or stored in vacuum.

[0049] Example 3 Construction of a three-electrode lithium-dielectric conductive catalytic nitrogen fixation system

[0050] Electrolytic cell and electrode cleaning: Disassemble the three-electrode single electrolytic cell, brush it with detergent powder, rinse it with pure water and then ultrasonically clean it with ethanol in sequence; clean the beaker and glass bottle for collecting gaseous / solid ammonia with pure water and then rinse them with ethanol; except for the working electrode, place the rest of the device in an oven to dry, and dry the working electrode with a hair dryer.

[0051] Electrolyte preparation: Under continuous stirring on a stirring table, mix 46.728g diethylene glycol dimethyl ether, 0.46875g lithium tetrafluoroborate, and 500μL ethanol, bring the volume to 50mL, and stir until completely dissolved to obtain a non-aqueous electrolyte; or prepare an electrolyte composed of THF, 0.2MLiBF4, and 2vol% ethanol.

[0052] Electrolytic cell assembly: The catalytic working electrode, platinum mesh counter electrode, and 0.5 mm diameter platinum wire reference electrode prepared in Example 2 were placed into a single electrolytic cell. The electrodes were isolated by polytetrafluoroethylene clamps. The prepared electrolyte was added, and the electrolytic cell was sealed to construct a three-electrode electrocatalytic system.

[0053] Example 4 Electrochemical Test of Lithium-Dielectric Conductive Catalysis for Nitrogen Fixation

[0054] The assembled single electrolytic cell was fixed on a stirring table with a rotation speed of 300 r / min. High-purity nitrogen gas was introduced from the inlet of the electrolytic cell at a flow rate of 20 mL / min. The outlet was connected to a glass bottle containing 50 mL of 0.05 M dilute sulfuric acid. The airtightness of the device was verified by generating bubbles. Nitrogen was continuously introduced for 30 minutes to saturate the electrolyte with nitrogen gas.

[0055] Connect the electrolytic cell to the CHI 760E electrochemical workstation and perform the following electrochemical tests in sequence:

[0056] OCPT test: Open circuit potential-time test, test duration 400 seconds, to determine whether the system has reached a stable state;

[0057] CV test: Cyclic voltammetry test, scan rate 0.5V / s, complete multiple scans to activate the catalyst and expose active sites;

[0058] Second OCPT test: Perform another 400-second open-circuit potential-time test to ensure system stability;

[0059] LSV test: Linear sweep voltammetry, scan rate 0.02 V / s, to study the electrocatalytic nitrogen fixation activity of the catalyst;

[0060] IT testing: Constant voltage-time test, test duration 7200 seconds, to achieve constant voltage electrochemical reduction of nitrogen to synthesize ammonia.

[0061] OCPT test

[0062] The basic information of the OCPT test is shown in Table 1, the key test parameters are shown in Table 2, the test data covers the complete cycle from 0.1s to 1800s, and the key data points selected according to the time gradient are shown in Table 3.

[0063] Table 1

[0064] project Parameter value Test date February 8, 2026 Test type Open circuit potential-time test Instrument Model CHI760E Total test duration 1.8e+3 sec (30 minutes) Data recording mode Record the open circuit potential value at time intervals. Total number of data points 4628 groups (covering the entire test duration, with no missing data)

[0065] Table 2

[0066] parameter numerical values Remark Initial potential (0.1s) -0.4201 V Test start time potential Final potential (1800s) -3.974 V Potential at the end of the test Potential variation range -0.4201 V ~ -3.974 V Overall potential negative shift Average potential -2.197 V Average potential over the entire test cycle Maximum potential fluctuation ±0.005 V Maximum potential change within any consecutive 10 seconds

[0067] Table 3

[0068] Time (sec) Potential (V) Time (sec) Potential (V) Time (sec) Potential (V) Time (sec) Potential (V) 0.1 -0.4201 100 -0.4142 500 -0.4089 1000 -0.4035 1 -0.4204 200 -0.4078 600 -0.4072 1200 -0.4012 10 -0.4208 300 -0.403 700 -0.4061 1400 -0.3998 30 -0.4206 400 -0.4005 800 -0.405 1600 -0.3985 50 -0.4187 450 -0.3997 900 -0.4042 1800 -0.3974

[0069] Description of data characteristics of OCPT test:

[0070] 1. Potential change trend: The potential showed a continuous negative shift throughout the test, gradually decreasing from the initial -0.4201 V to -0.3974 V at 1800s, with an overall shift of 0.0227 V. The shift rate gradually slowed down over time, and the potential change became more gradual in the later stage (after 1000s), with fluctuations ≤ ±0.002 V, indicating that the system gradually reached a stable state.

[0071] 2. Data stability: The potential fluctuations were relatively obvious in the first 100 seconds (maximum fluctuation 0.005 V), mainly due to the initial stabilization process of the electrode-electrolyte interface; after 100 seconds, the fluctuation amplitude decreased significantly (≤±0.003 V), and after 1000 seconds, it entered the stable stage. The data repeatability was good, with no abnormal jumps or abrupt changes, indicating that the test system was stable and reliable.

[0072] 3. Data integrity: The test records data at uniform time intervals, with no missing, duplicate or abnormal data points, which can be directly used for subsequent work such as open circuit potential stability analysis and electrode interface behavior research.

[0073] CV test

[0074] The basic information of the CV test is shown in Table 4, the key electrochemical parameters are shown in Table 5, and the test data covers the cyclic scan range from -0.5 V to -5.0 V and back to -0.5 V.

[0075] Table 4

[0076] project Parameter value Test date February 8, 2026 Instrument Model CHI760E Initial potential (Init E) -0.5 V Highest potential (High E) -0.5 V Lowest potential (Low E) -5 V Initial scan direction (Init P / N) N (cathode direction) Scan Rate 0.5 V / s Number of scan segments 20 Sampling Interval 0.001 V Quiet Time 2 sec Sensitivity 0.001 A / V

[0077] Table 5

[0078] parameter numerical values Remark Peak potential (Ep) -0.913 V reduction peak potential Peak current (ip) 8.038e-8 A Reduction peak current Battery capacity (Ah) 5.064e-9 C Electrode reaction transfer of charge

[0079] Description of data characteristics for CV testing:

[0080] 1. Scanning trend: During cathode scanning, as the potential increases negatively (from -0.5 V to -5.0 V), the current gradually increases negatively (reduction reaction intensifies), reaching a peak current of 8.038e-8 A at -0.913 V, and then the current continues to increase negatively to -3.463e-3 A at -5.0 V; During anodic scanning, the potential returns from -5.0 V to the positive direction, and the current gradually rises positively (oxidation reaction occurs), eventually returning to the initial potential of -0.5 V at -5.829e-6 A, forming a complete cyclic voltammetry curve.

[0081] 2. Data integrity: A total of 10,001 potential-current data points (potential interval 0.001 V) were recorded during the test, covering the entire scan range. The data is continuous and without missing data, and can be used for subsequent electrochemical behavior analysis (such as reaction reversibility, electron transfer number calculation, etc.).

[0082] Secondary OCPT test

[0083] Table 6 shows the basic information of the secondary OCPT test. The core characteristics of the secondary OCPT test data are as follows:

[0084] (a) Data range

[0085] Time range: 0.1 seconds to 462.8 seconds (4628 data points in total)

[0086] Potential range: -2.222V ~ -1.807V (The final data ends with a potential value of -1.807V, indicating good data integrity).

[0087] (II) Trends

[0088] 1. Overall trend: The potential value gradually increases (approaching 0V) over time, without significant fluctuations or sudden changes, indicating that the system gradually becomes stable during the test.

[0089] 2. Stage characteristics:

[0090] Initial stage (0.1 seconds to 100 seconds): The potential rise rate is relatively fast, from -2.222V to -1.962V, with a cumulative rise of 0.26V;

[0091] Mid-term phase (100 seconds to 300 seconds): The rate of increase slows down, rising from -1.962V to -1.860V, a cumulative increase of 0.102V;

[0092] Later stage (300 seconds to 462.8 seconds): The rate of increase further decreases, slowly rising from -1.860V to -1.807V, with a cumulative increase of 0.053V, and the system gradually approaches a stable state.

[0093] Table 6

[0094] project Details Test type Open circuit potential-time test Test date February 8, 2026 Instrument Model CHI760E Test duration 600 seconds Data Dimensions Time (Time / sec), Potential (Potential / V)

[0095] LSV test

[0096] Basic information about the LSV test is shown in Table 7, and a selection of core data (the complete data contains 6000+ groups; the following is a selection of key intervals) is shown in Table 8. Data trend analysis:

[0097] 1. Forward potential range (1.0 V ~ 0.0 V): The current drops rapidly from 3.349e-3 A to 1.603e-5 A, showing a significant decreasing trend, indicating that oxidation reaction mainly occurs on the electrode surface in this range, and the oxidation reaction rate gradually weakens as the potential decreases.

[0098] 2. Near zero potential (0.0 V ~ -0.2 V): The current is at a low level (1.603e-5 A ~ 2.210e-6 A) and changes slowly, which may be the transition stage from oxidation to reduction reaction, and the electrode surface has low reactivity.

[0099] 3. Negative potential range (-0.2 V ~ -5.0 V): The current changes from positive to negative and continues to increase (the absolute value increases), gradually changing from 7.860e-9 A to -2.245e-3 A (approximate value), indicating that the reduction reaction begins to occur and gradually becomes dominant. As the potential increases negatively, the reduction reaction rate continues to increase.

[0100] Table 7

[0101] project Specific parameters Experiment Date February 8, 2026 Experimental methods Linear scanning voltammetry Instrument Model CHI760E Initial potential (Init E) 1 V Final potential (Final E) -5 V Scan Rate 0.02 V / s Sampling Interval 0.001 V Quiet Time 2 sec Sensitivity 0.001 A / V

[0102] Table 8

[0103] Potential (V) Current (A) Potential (V) Current (A) Potential (V) Current (A) 1 3.349e-3 0 1.603e-5 -1 -3.98E-05 0.5 8.948e-5 -0.24 7.860e-9 -1.5 -9.71E-05 0.2 3.851e-5 -0.5 -1.08E-05 -2 -2.34E-04 0 1.603e-5 -0.8 -2.35E-05 -2.5 -6.45E-04 -0.1 9.620e-6 -0.9 -3.22E-05 -3 -1.10E-03 -0.2 2.210e-6 -1 -3.98E-05 -3.5 -1.56E-03 -0.3 -2.60E-06 -1.2 -5.70E-05 -4 -2.04E-03 -0.4 -6.71E-06 -1.4 -7.98E-05 -4.5 -2.240e-3 (approximate value) -0.5 -1.08E-05 -1.6 -1.23E-04 -5 -2.245e-3 (approximate value)

[0104] IT test

[0105] The basic information for the IT test is shown in Table 9, and the test data (example: the first 10 data points) is shown in Table 10.

[0106] Data trends:

[0107] 1. Data range

[0108] Time range: 0.1 s ~ 4625.0 s (fully covers 7200 s of runtime, with data points spaced 0.1 s apart, totaling 72000 data points)

[0109] Current range: -1.390×10 -3A ~ -7.325×10 -4 A (the negative sign indicates that the current direction is the same as the set direction)

[0110] 2. Key Trends

[0111] Overall trend: The current value gradually increases (approaching 0) over time, with no obvious jumps or fluctuations, indicating that the test system is stable.

[0112] Segmentation features:

[0113] Initial stage (0.1 s ~ 100 s): The current decay rate is relatively fast, from -1.390 × 10 -3 A dropped rapidly to -8.763 × 10⁻⁶. -4 A, mainly the charging of the double layer on the electrode surface and the initial reaction transition stage;

[0114] Mid-term phase (100 s ~ 3000 s): The current decay rate slows down, from -8.763 × 10 -4 A steadily decreased to -7.542×10 -4 A. The system gradually enters a stable reaction state;

[0115] Later stage (3000 s ~ 7200 s): The current basically stabilizes, with minimal fluctuations (±5×10⁻⁶). -6 A), eventually stabilizing at -7.325×10 -4 A value around A indicates that the electrode reaction has reached dynamic equilibrium.

[0116] Table 9

[0117] project Specific parameters Test type Ampere chronoamperometry Test date February 8, 2026 Instrument Model CHI760E Initial potential (Init E) -3 V Sampling Interval 0.1 s Run Time 7.2 × 10³ s (i.e., 2 hours) Quiet Time 0 s Sensitivity 0.001 A / V Data Dimensions Two-dimensional data of time (Time / sec) and current (Current / A)

[0118] Table 10

[0119] Time (s) Current (A) Time (s) Current (A) 0.1 -1.39E-03 0.6 -1.37E-03 0.2 -1.38E-03 0.7 -1.36E-03 0.3 -1.38E-03 0.8 -1.36E-03 0.4 -1.37E-03 0.9 -1.35E-03 0.5 -1.37E-03 1 -1.35E-03

[0120] Example 5: Ammonia Collection and Concentration Detection

[0121] (a) Collection of ammonia

[0122] 1. Gaseous ammonia collection: During the electrochemical test, a glass bottle containing 50 mL of 0.05 M dilute sulfuric acid connected to the outlet is used to absorb gaseous ammonia, resulting in a gaseous ammonia absorption liquid.

[0123] 2. Solid ammonia collection: After the electrochemical test is completed, disassemble the electrolytic cell, remove the carbon paper from the working electrode, place it in a beaker containing 30 mL of 0.05 M dilute sulfuric acid, shake and wash, and collect the solid ammonia absorption liquid.

[0124] (II) Determination of ammonia concentration by indophenol blue method

[0125] 1. Preparation of standard solutions

[0126] Prepare a 1wt% LiBF4 electrolyte solution, dilute it 8 times to obtain the base solution; dissolve 4 mg NH4Cl in 40 mL of the base solution and stir to dissolve.

[0127] Take eight 10mL glass bottles and label them as 10μg / mL NH4Cl, 0, 50, 100, 150, 200, 250, and 300. Add 1mL of the above NH4Cl solution + 9mL of base solution to the 10μg / mL NH4Cl bottle and sonicate. Add the base solution of “2000μL - labeled value” to the other seven bottles, and then add the corresponding labeled value of 10μg / mL NH4Cl solution. Mix by sonication to obtain a series of ammonia standard solutions.

[0128] 2. Preparation of color developer

[0129] 0.05M NaClO (prepared fresh): Add 2mL NaClO to 21.54mL water, wrap with aluminum foil and stir;

[0130] 1wt% sodium nitrosoferricyanide aqueous solution (prepared fresh): 47.86mg sodium nitrosoferricyanide dissolved in 5mL of water, wrapped in aluminum foil to dissolve;

[0131] Colorimetric base solution: Dissolve 1.32g NaOH in 33mL water, weigh out 1 / 19 of the solution mass of salicylic acid and sodium citrate respectively, add them, stir to dissolve, and obtain a 1M NaOH solution of 5wt% salicylic acid + 5wt% sodium citrate.

[0132] 3. Color reaction

[0133] Take four 10mL glass bottles and label them g (gas phase), l (blank electrolyte), l (blank electrolyte), and s (solid phase); add 2mL of electrolyte diluted 8 times to bottle l, add 2mL of solid phase ammonia absorption solution to bottle s, and add 2mL of gas phase ammonia absorption solution to bottle g.

[0134] Add 2 mL of colorimetric base solution + 1 mL of 0.05 M NaClO + 0.2 mL of 1 wt% sodium nitrosoferricyanide aqueous solution to each of the four glass bottles, mix well, place in a box wrapped with tin foil, and let stand at room temperature for 2 hours to complete the color development.

[0135] 4. Ultraviolet detection and standard curve plotting

[0136] Ultraviolet detection was performed using a UV-Vis spectrophotometer. Instrument model: GENESYS50; scanning wavelength range: 500-800 nm; scanning interval: 1.0 nm; scanning speed: medium speed.

[0137] Rinse the cuvette with the basic solution, add blank solution for blank calibration, and then measure the absorbance of the ammonia standard series solutions and sample colorimetric solutions in sequence. The absorbance of each sample solution is shown in the figure below. Figure 1 As shown. (Through) Figure 1 It can be seen that the absorbance of the sample solution is the highest when the scanning wavelength is 654nm, 655nm, and 656nm.

[0138] Therefore, in subsequent ultraviolet detection, the scanning wavelengths were directly set to 654nm, 655nm, and 656nm, with the net height at three points as the detection index. During detection, the cuvettes were rinsed with the base solution, and blank solution was added for blank calibration. Subsequently, the absorbance of the ammonia standard series solutions and the sample colorimetric solution were measured sequentially, as shown in Table 11.

[0139] Table 11

[0140] Wavelength (nm) Sample 1 (Abs) Sample 2 (Abs) Sample 3 (Abs) Sample 4 (Abs) Sample 5 (Abs) Sample 6 (Abs) Sample 7 (Abs) 656 0.08934 0.04317 0.08294 0.03272 0.08333 0.06941 0.07238 655 0.08839 0.0435 0.08364 0.03255 0.08378 0.07085 0.07262 654 0.08893 0.04257 0.08178 0.03279 0.0843 0.06946 0.07238

[0141] A scatter plot was drawn with the concentration of the ammonia standard solution as the x-axis and the absorbance as the y-axis, and linear regression was performed to obtain the standard curve equation y=kx+b. The actual concentrations of ammonia in the gas phase and solid phase were calculated by substituting the absorbance of the sample into the equation.

[0142] Example 6 Calculation of ammonia yield and Faraday efficiency

[0143] Based on the gaseous and solid ammonia concentrations obtained in Example 5, the amount of ammonia in the gaseous and solid phases was calculated, and the total amount of ammonia, M (mol), was obtained by summing them.

[0144] Export the test data from the electrochemical workstation and calculate the total charge Q(C) consumed during the electrocatalysis process.

[0145] The charge efficiency (FE) of ammonia represents the ratio of the amount of charge used to reduce nitrogen to ammonia during the reaction to the total charge consumed in the entire electrocatalytic reaction, reflecting the efficiency of charge utilization during the catalytic reaction. Theoretically, three electrons are consumed to form one ammonia molecule. Therefore, the formula for calculating the FE of ammonia is as follows:

[0146]

[0147] In the formula, F is the Faraday constant (96485 C / mol); M is the total amount of ammonia produced in the electrolytic cell (mol); and Q is the total amount of charge applied during the electrocatalysis process (C).

[0148] Record the catalyst loading area on carbon paper The constant voltage reaction time t (s) is calculated according to the ammonia yield formula: .

[0149] Comparative Example: Using pure NH2-MIL-101 (Fe) and pure CoPc as catalysts, electrodes were prepared, systems were constructed, and electrocatalytic tests and ammonia detection were performed following the same steps as in Examples 2-6. The results showed that pure NH2-MIL-101 (Fe) had weak N2 activation ability and low ammonia yield; pure CoPc could not achieve Li + The system exhibits enrichment of N2 and significant lithium dendrite growth, resulting in poor system stability and a significantly lower Faraday efficiency compared to the NH2-MIL-101 (Fe)@CoPc composite catalyst system of this invention.

[0150] Table 12

[0151] Indicators\Experiment Number 26.2.4 (1) 3V 26.2.4 (2) 26.2.5 (1) 26.2.5 (2) 26.2.6 (1) 26.2.7 (1) 26.2.7 (2) Absorbance (l) 0.08839 0.0435 0.08364 0.03255 0.08378 0.07085 0.07262 Absorbance (g) 0.023 0.201 0.079 0.072 0.024 0.01 0.01 Absorbance (s) 0.019 0.078 0.075 0.072 0.025 0.011 0.009 m(l) (g) 569.9918792 278.3563424 539.1326945 207.2178009 540.0422284 456.0402794 467.5393861 m(g) (g) 7.488689579 78.1292166 29.71267561 26.93467736 7.885546472 2.329549964 2.329549964 m(s) (g) 3.540757203 17.58949123 16.87514882 16.16080641 4.969442019 1.635844115 1.159615843 Total m (g) 581.0213259 374.0750502 585.7205189 250.3132846 552.8972168 460.0056734 471.0285519 Q 3322 4.39 4057 4.442 338 3405 422 FE(l) 92.91713423 343.3708058 71.96435353 25.38817935 76.96103341 72.52919436 60.28311403 FE(g) 1.220767524 9.63775132 3.966098724 3.300017743 1.123763613 0.370494427 0.300365125 FE(s) 0.577959064 22.66977911 2.252523707 1.980010646 0.708191644 0.260166615 0.149517359 Total FE 94.71599772 46.1461101 78.18297556 30.66820774 78.79298867 73.15985541 60.73299652 Yield 3.016725472 1.942238059 3.0412419 1.299653607 2.87070206 2.38339135 2.44563111

[0152] As shown in Table 12, experiments revealed that the absorbance of sample 1 was 0.08839 when the scanning wavelength was 655 nm. Back-calculation showed that, using the NH2-MIL-101 (Fe)@CoPc composite catalyst of this invention, the Faradaic efficiency of sample 1 was 94.72%, and the yield was 3.017.

[0153] Conclusion: When the NH2-MIL-101 (Fe)@CoPc composite catalyst of the present invention is applied to lithium dielectric conductive nitrogen fixation, it achieves synergistic catalysis between the support and the active component, which not only improves the N2 activation and ammonia generation efficiency, but also optimizes the lithium metal anode interface behavior. Compared with the single catalyst, the ammonia yield and Faraday efficiency are significantly improved, and the cycle stability of the system is significantly enhanced.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. Application of NH2-MIL-101 (Fe)@CoPc composite catalyst in lithium-dielectric conductive nitrogen fixation and ammonia synthesis.

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