A method for co-producing aviation fuel components using a graphite felt / high-entropy MOF electrode, a lignin-based fuel cell, and a method for the production of aviation fuel components.

Abstract

This invention discloses a graphite felt / high-entropy MOF electrode, a lignin-based fuel cell, and a method for co-producing aviation fuel components. The graphite felt / high-entropy MOF electrode is obtained by hydrothermal reaction of various soluble metal salts with 2,5-dihydroxyterephthalic acid in a solvent, generating a high-entropy MOF in situ on the graphite felt surface. Using the graphite felt / high-entropy MOF electrode of this invention to assemble a lignin-based flow fuel cell, high power density output and efficient conversion of biomass energy to electrical energy were successfully achieved. After prolonged power generation, this flow battery can promote the efficient and directional depolymerization of lignin macromolecules into aviation fuel precursors, producing C8-C6. 16 Small molecules are mainly concentrated in C 10 ~C 11 It can be further hydrogenated and deoxygenated to produce aviation fuel, which has great commercial prospects and utilization value.

Description

Technical Field

[0001] This invention belongs to the field of high-value utilization of lignin, specifically relating to a graphite felt / high-entropy MOF electrode, a lignin-based fuel cell, and a method for co-producing aviation fuel components. Background Technology

[0002] The global trend of reducing fossil fuel use is becoming increasingly significant, prompting greater attention to the development and utilization of clean energy. Therefore, there is an urgent need to actively develop clean and renewable energy sources. Biomass energy, as a renewable energy source, has great potential, and the conversion of biomass into clean electricity has always been a research focus. Currently, most of the anode oxidants used in reported biomass fuel cells are polyoxometalates (POMs), which are complex to synthesize, have poor solubility, and are expensive, limiting their widespread application. Furthermore, the graphite felt electrode materials used in this type of battery have drawbacks such as poor wettability, small specific surface area, and low electrocatalytic activity, resulting in high interfacial resistance between the electrolyte and the electrode. This typically limits the power density of biomass fuel cells, leading to poor battery output performance and making it difficult to meet practical needs.

[0003] As one of the three main components of biomass, lignin is abundant, renewable, and inexpensive. However, most industrial lignin is currently disposed of through incineration or direct emission. Fuel cell systems are a clean and efficient energy conversion technology that can convert lignin into electricity. However, current fuel cells suffer from problems such as high operating temperatures, low energy utilization, and low power density, making it difficult to achieve efficient direct conversion of lignin into electricity. In contrast, redox biomass fuel cells can directly and efficiently convert lignocellulosic biomass into electricity at lower temperatures.

[0004] Lignin is an important component of biomass and, as an abundant renewable resource, is often used in energy storage batteries to mitigate the instability of traditional materials due to its structural characteristics. Currently reported lignin fuel cells integrate the advantages of redox biomass fuel cells, directly converting lignin into electrical energy at low temperatures, and exhibiting higher power generation efficiency than other types of fuel cells such as microbial fuel cells. However, when used as fuel, lignin requires thermodynamic, chemical, or biological modification, leading to low energy utilization efficiency, slow electron transfer rates, low battery output power density, and poor stability. Furthermore, the internal graphite felt electrode is highly hydrophobic with a small specific surface area, resulting in slow electron transfer rates at the electrolyte-electrode interface, which restricts performance improvement and application research of this type of battery.

[0005] Currently, converting biomass into aviation fuel can effectively maintain carbon balance, improve the environment, and promote energy conservation, emission reduction, and energy transition. As a renewable energy source, biomass, when converted into aviation fuel, helps enhance the stability and security of energy supply and reduce dependence on external energy markets. Its conversion into aviation fuel also contributes to the optimization and transformation of the energy structure. By increasing the application of biomass energy in the aviation sector, dependence on fossil fuels can be reduced, the diversity and sustainability of energy use can be improved, and commercial applications can reduce airline operating costs and increase economic efficiency. Biomass aviation fuel has the same chemical composition as fossil fuels, containing C8-C. 16 The composition of lignin includes chain hydrocarbons, cycloalkanes, and aromatic compounds, varying depending on the manufacturer and raw materials. Currently, lignin depolymerization mainly relies on pyrolysis, but insufficient energy recovery leads to resource waste.

[0006] Therefore, there is an urgent need for an efficient method to convert biomass into aviation fuel, and to construct a low-temperature, high-efficiency lignin fuel cell that can generate electricity and produce aviation fuel components simultaneously by oxidizing and degrading industrial lignin. Summary of the Invention

[0007] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing a graphite felt / high-entropy MOF electrode. This invention utilizes hydrothermal synthesis technology to successfully grow a high-entropy MOF in situ on a graphite felt substrate. The resulting electrode exhibits excellent electrocatalytic activity, a large specific surface area, and a faster electron transport rate. Using this electrode in the assembly of lignin fuel cells facilitates the oxidation of lignin, thereby enabling the efficient degradation of lignin macromolecules and the simultaneous co-production of electricity and aviation fuel components.

[0008] Another object of the present invention is to provide a graphite felt / high-entropy MOF electrode prepared by the above method.

[0009] Another object of the present invention is to provide a lignin-based fuel cell constructed using the above-described graphite felt / high-entropy MOF electrode.

[0010] This invention uses lignin alkaline solution as the anode electrolyte, vanadium sulfate and nitric acid as the cathode electrolyte, oxygen as the cathode regenerator, graphite felt / high entropy MOF as the anode electrode material, and graphite felt as the cathode electrode material to assemble a lignin-based fuel cell. The resulting battery has high power density and high open-circuit voltage, and the materials used are inexpensive, readily available, safe, and environmentally friendly.

[0011] Another object of the present invention is to provide a method for co-producing aviation fuel components using the above-mentioned lignin-based fuel cell.

[0012] The lignin-based fuel cell of the present invention can generate electricity mainly composed of C8 to C8 after long-term power generation. 16Small molecule substances, similar to small molecule substances that are precursors for aviation fuel, are expected to be used to prepare aviation fuel through hydrogenation and deoxygenation, and have broad application prospects and utilization value.

[0013] The objective of this invention is achieved through the following technical solution:

[0014] A method for preparing a graphite felt / high-entropy MOF composite material includes the following steps:

[0015] Soluble cobalt salt, soluble nickel salt, soluble copper salt, soluble manganese salt, soluble molybdenum salt, and 2,5-dihydroxyterephthalic acid were dissolved in a solvent, and graphite felt was added. The mixture was subjected to a hydrothermal reaction in a high-pressure reactor. After the reaction was completed, the graphite felt sample was removed, washed, and dried to obtain a graphite felt / high-entropy MOF composite material.

[0016] Preferably, the molar ratio of the soluble cobalt salt, soluble nickel salt, soluble copper salt, soluble manganese salt, and soluble molybdenum salt is (0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5).

[0017] Preferably, the soluble cobalt salt, soluble nickel salt, soluble copper salt, soluble manganese salt, and soluble molybdenum salt are CoCl5·6H2O, NiCl2·6H2O, CuCl2, MnCl2·4H2O, and MoCl5, respectively.

[0018] Preferably, the concentrations of the soluble cobalt salt, soluble nickel salt, soluble copper salt, soluble manganese salt, and soluble molybdenum salt in the solvent are all 0.01–0.18 mol / L, more preferably 0.09–0.13 mmol / L.

[0019] Preferably, the molar ratio of the soluble cobalt salt to 2,5-dihydroxyterephthalic acid is (0.5-1.5):(1-4).

[0020] Preferably, the solvent is N,N-dimethylformamide, anhydrous ethanol and water in a volume ratio of (10-15):(0.5-1.5):(0.5-1.5).

[0021] Preferably, the hydrothermal reaction temperature is 20–200°C and the time is 2–24 h; more preferably, the hydrothermal reaction temperature is 60–130°C and the time is 4–24 h; most preferably, the hydrothermal reaction temperature is 60–130°C and the time is 4–12 h.

[0022] Preferably, the washing solution is at least one of ethanol, deionized water, and acetone.

[0023] A graphite felt / high-entropy MOF composite material was prepared by the above method.

[0024] The above-mentioned graphite felt / high-entropy MOF composite material is used in lignin-based fuel cells.

[0025] The present invention also provides a lignin-based fuel cell, comprising an anode electrolyte and an anode electrode; wherein the anode electrolyte is a lignin alkaline solution and the anode electrode is the above-mentioned graphite felt / high-entropy MOF composite material.

[0026] Preferably, the concentration of lignin in the lignin alkaline solution is 1-100 g / L, more preferably 1-80 g / L, even more preferably 5-70 g / L, and most preferably 10-50 g / L.

[0027] Preferably, the hydroxide ion concentration in the lignin alkaline solution is 0.02–10 mol / L, more preferably 0.05–3 mol / L, and most preferably 0.2–2 mol / L.

[0028] Preferably, the alkali used in the lignin alkaline solution is at least one of NaOH, KOH, and ammonia water.

[0029] Preferably, the lignin used in the lignin alkaline solution is at least one of enzymatically hydrolyzed lignin, pre-hydrolyzed lignin, lignin sulfonate, and alkali lignin.

[0030] Preferably, the lignin-based fuel cell further includes a cathode electrolyte, which comprises a pentavalent vanadium salt, an acid solution, and an oxidant for cathode regeneration.

[0031] More preferably, the pentavalent vanadium salt is at least one of vanadium pentoxide, vanadium nitrate, and vanadium sulfate; the concentration of the pentavalent vanadium salt in the cathode electrolyte is 0.05–5 mol / L.

[0032] More preferably, the acid solution is at least one of hydrochloric acid aqueous solution, sulfuric acid aqueous solution and nitric acid aqueous solution; the concentration of the acid solution is 0.05 to 8.0 mol / L.

[0033] More preferably, the oxidant is at least one of nitric acid and oxygen; the concentration of the nitric acid in the cathode electrolyte is 0.01 to 8 mol / L; and the flow rate of the oxygen introduced into the cathode electrolyte is 10 to 120 mL / min.

[0034] Preferably, the lignin-based fuel cell further includes a cathode electrode; the cathode electrode is a graphite felt.

[0035] Preferably, the operating temperature of the lignin-based fuel cell is 20–120°C, more preferably 60–110°C.

[0036] The present invention also provides a method for co-producing aviation fuel components using the above-mentioned lignin-based fuel cell, comprising the following steps:

[0037] The above-mentioned lignin-based fuel cell was operated at 20–120°C. The lignin in the anode electrolyte underwent a depolymerization reaction. The depolymerization products were extracted and then subjected to hydrogenation deoxygenation treatment to obtain aviation fuel components.

[0038] Preferably, the operating temperature of the lignin-based fuel cell is 60–110°C.

[0039] Preferably, the solvent used for extraction is at least one of ethyl acetate, isopropyl acetate, and butyl acetate.

[0040] Preferably, the temperature of the hydrodeoxygenation treatment is 150–210°C, and the time is 6–10 h.

[0041] Preferably, the hydrodeoxygenation treatment is carried out under the action of a catalyst, which is at least one of a Pt / C catalyst and an Fe-based catalyst; the mass ratio of the depolymerization product to the catalyst is (0.5-1):(3-5).

[0042] Preferably, the hydrodeoxygenation treatment is carried out in a high-pressure reactor, and the solvent is at least one of cyclohexane and n-octane; the ratio of the depolymerization product to the solvent is 0.5-1.5 mg: 0.5-1.5 mL.

[0043] Preferably, the hydrogen pressure in the hydrodeoxygenation treatment is 3-5 MPa.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] 1. This invention uses low-cost and environmentally friendly transition metals, resulting in low cost, low price, and high cost-effectiveness. It prepares a graphite felt / high-entropy MOF electrode. The high-entropy alloy catalyst breaks through the limitations of traditional single-component catalysts, introduces the concept of multi-components, and provides a new idea for the design of more efficient catalysts. This electrode not only has a high specific surface area and excellent electrocatalytic activity, but its preparation process is also simple and can achieve the best results without complicated calcination steps.

[0046] 2. When the graphite felt / high-entropy MOF electrode of this invention is applied to lignin-based fuel cells, it exhibits a power density far exceeding that of similar designs currently reported, and its performance is particularly outstanding.

[0047] 3. The lignin-based fuel cell of this invention does not require the addition of an additional redox couple to assist electron transfer in its anolyte, thereby simplifying the electron transfer and subsequent lignin separation and purification process. Furthermore, the battery can directly generate electricity using unheated electrolyte, effectively avoiding lignin condensation, further simplifying the power generation process and reducing energy consumption. Moreover, the lignin-based fuel cell of this invention generates electricity by directly electrocatalytically oxidizing lignin on the electrode. The application of graphite felt / high-entropy MOF electrodes significantly improves the oxidation rate and electron transport efficiency of lignin, thereby greatly enhancing the overall performance of the fuel cell.

[0048] 4. The graphite felt / high-entropy MOF electrode of this invention possesses excellent corrosion resistance and thermal stability, making it suitable for harsh catalytic environments. Through the inherent synergistic effect of severe lattice distortion and tunable electronic structure, it exhibits a large number of active sites. Furthermore, its catalytic performance can be adjusted by modifying the composition and structure of the high-entropy alloy, resulting in excellent electrocatalytic activity. The synthesized MOF material has a highly controllable structure, a large specific surface area, and good stability. Therefore, the lignin-based fuel cell of this invention can induce the deep degradation of a large number of lignin macromolecules, thereby comprehensively improving the various performance indicators of the fuel cell.

[0049] 5. The long-term power generation products of the lignin-based liquid flow fuel cell constructed with the graphite felt / high-entropy MOF electrode of this invention are mainly C8 to C6. 16 Small molecules, primarily concentrated in C 10 ~C 11 It can be further hydrogenated and deoxygenated to produce aviation fuel, which has broad application prospects and utilization value. Attached Figure Description

[0050] Figure 1 The current density-voltage-output power diagram is shown for the lignin-based liquid flow fuel cell constructed using the CoNiCuMnMo-MOF / GF electrode in Example 1.

[0051] Figure 2 The image shows the XRD pattern of the CoNiCuMnMo-MOF / GF electrode in Example 1, where HEA-MOF / GF represents CoNiCuMnMo-MOF / GF.

[0052] Figure 3 The current density-voltage-output power graph of the lignin-based liquid flow fuel cell constructed with the 1CoNiCuMnMo-HEO / GF electrode is shown.

[0053] Figure 4The figure shows the current density-voltage-output power of a lignin-based flow fuel cell constructed with CoNiCuMnMo-MOF / GF electrodes prepared with different metal concentrations in Example 2. In the figure, HEA-MOF / GF is CoNiCuMnMo-MOF / GF.

[0054] Figure 5 The figure shows the current density-voltage-output power of a lignin-based flow fuel cell constructed using CoNiCuMnMo-MOF / GF electrodes prepared with different hydrothermal reaction times in Example 3. In the figure, HEA-MOF / GF is CoNiCuMnMo-MOF / GF, and HEA / GF is CoNiCuMnMo / GF.

[0055] Figure 6 The LSV and EIS plots are from the electrochemical tests of the CoNiCuMnMo-MOF / GF electrode in Example 4.

[0056] Figure 7 This is a SEM image of the CoNiCuMnMo-MOF / GF electrode from Example 4.

[0057] Figure 8 The diagram shows the electron transfer rate and energy released after long-term power generation from enzymatic hydrolysis of lignin in Example 5.

[0058] Figure 9 This is a GC-MS image of the degradation products of lignin after long-term power generation following enzymatic hydrolysis in Example 5.

[0059] Figure 10 For Comparative Example 2, the current density-voltage-output power graph of the lignin-based liquid flow fuel cell constructed with graphite felt electrodes is shown.

[0060] Figure 11 The current density-voltage-output power graphs are for the lignin-based liquid flow fuel cells constructed with CoNiCuMnMo-MOF / GF electrodes before and after calcination in Comparative Example 3. Detailed Implementation

[0061] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0062] Unless otherwise specified, "room temperature" in this invention refers to 10-30°C.

[0063] The enzymatically hydrolyzed lignin used in the following embodiments and comparative examples of this invention was purchased from Shandong Longli Biotechnology Co., Ltd. The graphite felt was purchased from Carbon Energy, Taiwan, and was ultrasonically cleaned with anhydrous ethanol, acetone, 75% hydrochloric acid solution, and deionized water before use.

[0064] The electrical performance (current density, voltage, and output power) of the battery prepared in this invention was tested using the scanning current method.

[0065] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0066] Example 1: Preparation and performance study of CoNiCuMnMo-MOF / GF electrode

[0067] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0068] 2. Preparation of CoNiCuMnMo-MOF / GF electrode: 3 mmol CoCl5·6H2O, 3 mmol NiCl2·6H2O, 3 mmol CuCl2, 3 mmol MnCl2·4H2O, 3 mmol MoCl5, and 9 mmol 2,5-dihydroxyterephthalic acid were dissolved in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water to obtain a hydrothermal reaction solution. A 5 cm × 0.5 cm × 0.5 cm graphite felt was adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 24 h. After the reaction, the sample was removed, washed several times with deionized water, and dried to obtain the graphite felt / high-entropy MOF electrode.

[0069] 3. Preparation of anolyte: Weigh 4g NaOH and dissolve it in 50ml deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0070] 4. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of pure nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0071] 5. Battery Assembly and Electrical Performance Measurement: Construct the battery system. The LFFC (flow fuel cell) consists of two all-carbon graphite electrodes with serpentine flow channels, and has a total effective area of ​​1 cm². 2The Nafion 211 membrane separates the electrodes. Graphite felt fills the cathode channel of the battery system, and the graphite felt / high-entropy MOF electrode fills the anode channel. The anolyte and catholyte are mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 + The cathode electrolyte was regenerated. The LFFC system operated at 90°C. The sample cell performance was tested using the 857 flow cell testing system.

[0072] The battery's electrical performance was tested using the scanning current method, and the results are as follows: Figure 1 As shown, the maximum power density of the CoNiCuMnMo-MOF / GF electrode is 261.03 mW / cm². 2 It has good battery performance.

[0073] The XRD pattern of CoNiCuMnMo-MOF / GF in Example 1 is as follows: Figure 2 As shown, the peaks at 25.7° and 43.9° correspond to the (002) and (101) crystal planes of carbon. The other peaks are caused by MOFs. In other words, the main peaks of CoNiCuMnMo-MOF / GF can be indexed with MOFs.

[0074] Comparative Example 1: Preparation and Performance Study of CoNiCuMnMo-HEO / GF High-Entropy Oxide Electrode

[0075] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0076] 2. Preparation of CoNiCuMnMo-HEO / GF electrode: 3 mmol CoCl5·6H2O, 3 mmol NiCl2·6H2O, 3 mmol CuCl2, 3 mmol MnCl2·4H2O, and 3 mmol MoCl5 were dissolved in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water to obtain a hydrothermal reaction solution. A 5 cm × 0.5 cm × 0.5 cm graphite felt, after pretreatment, was adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 24 h. After cooling to room temperature, the prepared sample was washed several times with deionized water and dried overnight in an oven at 60 °C to obtain the graphite felt / high-entropy oxide electrode.

[0077] 3. Preparation of anolyte: Weigh 4g NaOH and dissolve it in 50ml deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0078] 4. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0079] 5. Battery Assembly and Electrical Performance Measurement: Construct the battery system. The LFFC consists of two all-carbon graphite electrodes with serpentine flow channels, and has a total effective area of ​​1 cm². 2 The Nafion 211 membrane separates the electrodes. Graphite felt fills the cathode channel of the battery system, and a CoNiCuMnMo-HEO / GF high-entropy oxide electrode fills the anode channel. The anolyte and catholyte are mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 + This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0080] The battery's electrical performance was tested using the scanning current method, and the results are as follows: Figure 3As shown, when the CoNiCuMnMo-HEO / GF electrode is used as the anode electrode, the maximum power density of the battery is 242.41 mW / cm². 2 The maximum power density in Example 1 was 261.03 mW / cm³. 2 In comparison, it can be seen that the performance of Example 1 is significantly better after adding the MOF framework.

[0081] Example 2: The effect of CoNiCuMnMo-MOF / GF electrodes prepared with different metal concentrations on fuel cells.

[0082] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0083] 2. Preparation of CoNiCuMnMo-MOF / GF electrode: The first hydrothermal reaction solution was prepared by dissolving 3 mmol CoCl5·6H2O, 3 mmol NiCl2·6H2O, 3 mmol CuCl2, 3 mmol MnCl2·4H2O, 3 mmol MoCl5, and 9 mmol 2,5-dihydroxyterephthalic acid in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water. The second hydrothermal reaction solution was prepared by dissolving 4 mmol CoCl5·6H2O, 4 mmol NiCl2·6H2O, 4 mmol CuCl2, 4 mmol MnCl2·4H2O, 4 mmol MoCl5, and 12 mmol 2,5-dihydroxyterephthalic acid in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water. The second hydrothermal reaction solution was prepared by dissolving 6 mmol CoCl5·6H2O, 6 mmol... NiCl2·6H2O, CuCl2, 6 mmol MnCl2·4H2O, 6 mmol MoCl5, and 18 mmol 2,5-dihydroxyterephthalic acid were dissolved in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water to obtain the third group of hydrothermal reaction solutions. Pretreated 5 cm × 0.5 cm × 0.5 cm graphite felts were adhered to the solutions with medical tape and placed in the hydrothermal reaction solutions to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 24 h. After the reaction was completed and cooled to room temperature, the samples were removed, washed several times with deionized water, and dried overnight in an oven at 60 °C to obtain three types of graphite felt / high-entropy MOF electrodes.

[0084] 3. Preparation of anolyte: Weigh 4g NaOH and dissolve it in 50ml deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0085] 4. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0086] 5. Battery Assembly and Electrical Performance Measurement: Three battery systems were constructed. The LFFC consisted of two all-carbon graphite electrodes with serpentine flow channels, and had a total effective area of ​​1 cm². 2 The Nafion 211 membranes were used as separators. Graphite felt was filled in the cathode channels of the three battery systems, and the three types of graphite felt / high-entropy MOF electrodes obtained from the above operation were each filled in the anode channel of one battery system. The anolyte and catholyte were mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 + This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0087] The battery's electrical performance was tested using the scanning current method, and the results are as follows: Figure 4 As shown, the graphite felt / high-entropy MOF electrode obtained by using 6 mmol of each metal salt as the third group of hydrothermal reaction solutions exhibits the best battery performance, with a maximum voltage of 1.5 V and a maximum current density of 772.59 mA / cm². 2 The maximum power density is 366.62 mW / cm³. 2 The graphite felt / high-entropy MOF electrode obtained using 4 mmol of each metal salt as the third group of hydrothermal reaction solutions had the second highest maximum power density at 333.91 mW / cm². 2 This demonstrates that the graphite felt / high-entropy MOF electrode obtained by using 6 mmol of each metal salt as the third group of hydrothermal reaction solutions has superior battery performance.

[0088] Example 3: Effects of CoNiCuMnMo-MOF / GF electrodes with different reaction times on fuel cells

[0089] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0090] 2. Preparation of graphite felt / high-entropy MOF electrodes: A hydrothermal reaction solution was prepared by dissolving 6 mmol CoCl5·6H2O, 6 mmol NiCl2·6H2O, 6 mmol CuCl2, 6 mmol MnCl2·4H2O, 6 mmol MoCl5, and 18 mmol 2,5-dihydroxyterephthalic acid in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water. Pretreated 5 cm × 0.5 cm × 0.5 cm graphite felts were adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reactions were carried out at 120 °C in a high-pressure reactor for 4 h, 6 h, and 12 h, respectively. After the reaction, the samples were removed, washed multiple times with deionized water, and dried to obtain three types of graphite felt / high-entropy MOF electrodes.

[0091] 3. Preparation of anolyte: Weigh 4g NaOH and dissolve it in 50ml deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0092] 4. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0093] 5. Battery Assembly and Electrical Performance Measurement: Three battery systems were constructed. The LFFC consisted of two all-carbon graphite electrodes with serpentine flow channels, and had a total effective area of ​​1 cm². 2 The Nafion 211 membranes were used as separators. Graphite felt was filled in the cathode channels of the three battery systems, and the three types of graphite felt / high-entropy MOF electrodes obtained from the above operation were each filled in the anode channel of one battery system. The anolyte and catholyte were mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2+ This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0094] The battery's electrical performance was tested using the scanning current method, and the results are as follows: Figure 5 As shown, the graphite felt / high-entropy MOF electrode exhibits the best battery performance after 12 hours of hydrothermal reaction, with a maximum voltage of 1.58V and a maximum current density of 1454.1 mA / cm². 2 The maximum power density is 545.48 mW / cm³. 2 The battery performance was lower for hydrothermal reactions of 4h and 6h. This indicates that the graphite felt / high-entropy MOF electrode battery with a hydrothermal reaction of 12h exhibits the best performance and is more conducive to lignin oxidation.

[0095] Example 4: Electrochemical activity of the CoNiCuMnMo-MOF / GF electrode

[0096] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0097] 2. Preparation of graphite felt / high-entropy MOF electrode: A hydrothermal reaction solution was prepared by dissolving 6 mmol CoCl5·6H2O, 6 mmol NiCl2·6H2O, 6 mmol CuCl2, 6 mmol MnCl2·4H2O, 6 mmol MoCl5, and 18 mmol 2,5-dihydroxyterephthalic acid in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water. A 5 cm × 0.5 cm × 0.5 cm graphite felt was adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 12 h. After the reaction, the sample was removed, washed several times with deionized water, and dried to obtain the graphite felt / high-entropy MOF electrode.

[0098] 3. Preparation of graphite felt / high-entropy oxide electrode: A hydrothermal reaction solution was prepared by dissolving 6 mmol CoCl5·6H2O, 6 mmol NiCl2·6H2O, 6 mmol CuCl2, 6 mmol MnCl2·4H2O, and 6 mmol MoCl5 in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water. A 5 cm × 0.5 cm × 0.5 cm graphite felt was adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 12 h. After the reaction, the sample was removed, washed several times with deionized water, and dried to obtain the graphite felt / high-entropy oxide electrode.

[0099] 4. Prepare NaOH solution: Weigh 8g of NaOH and dissolve it in 100ml of deionized water to obtain a 2mol / L NaOH solution.

[0100] 5. Using a Gamry electrochemical workstation, the reference electrode was a standard Ag / AgCl electrode, the counter electrode was a graphite rod, and the working electrodes were the prepared graphite felt / high-entropy MOF electrode and the graphite felt / high-entropy oxide electrode. Linear sweep voltammetry was employed. The test range was from 1.5V to -0.5V and between this range and the reversible hydrogen electrode (RHE), with a scan rate of 5mV / s in 2mol / L NaOH solution. The electrode potential was calculated using the formula E. RHE =E Ag / AgCl +0.197V +0.059V × pH. Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 20 kHz to 0.01 Hz over a frequency range of 5 mV.

[0101] The test results are as follows Figure 6 As shown, it can be concluded that the graphite felt / high-entropy MOF electrode with MOF addition, compared to the graphite felt / high-entropy oxide electrode without MOF, achieves a lower speed at 50 mA / cm². 2 It exhibits a smaller overpotential and lower impedance at the current density. This demonstrates that the graphite felt / high-entropy MOF electrode with the addition of a high-entropy organic framework (MOF) possesses better reaction kinetics and electrochemical activity.

[0102] The SEM image of the CoNiCuMnMo-MOF / GF electrode in this embodiment is as follows: Figure 7 As shown, the morphology of the high-entropy MOF is that a layer of sheet-like material is loaded onto the carbon fiber and stacked into a block shape, with a relatively uniform distribution.

[0103] Example 5: Preparation of aviation fuel precursors by long-term power generation from flow batteries

[0104] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0105] 2. Preparation of graphite felt / high-entropy MOF electrode: A hydrothermal reaction solution was prepared by dissolving 6 mmol CoCl5·6H2O, 6 mmol NiCl2·6H2O, 6 mmol CuCl2, 6 mmol MnCl2·4H2O, 6 mmol MoCl5, and 18 mmol 2,5-dihydroxyterephthalic acid in a mixed solvent of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water. A 5 cm × 0.5 cm × 0.5 cm pretreated graphite felt was adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 12 h. After the reaction, the sample was removed, washed several times with deionized water, and dried to obtain the graphite felt / high-entropy MOF electrode.

[0106] 3. Preparation of anolyte: Weigh 8g of NaOH and dissolve it in 100ml of deionized water, stirring for 10min. Then weigh 1g of enzymatically hydrolyzed lignin, add it to the solution, stir for 20min, and filter to obtain 100ml of lignin alkaline solution as anolyte.

[0107] 4. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 600ml of this electrolyte as the cathode electrolyte.

[0108] 5. Battery Assembly: Construct the battery system. The LFFC consists of two all-carbon graphite electrodes with serpentine flow channels, and has a total effective area of ​​1 cm². 2 The Nafion 211 membrane is used as a separator. Graphite felt is filled in the cathode channel, and the graphite felt / high-entropy MOF electrode obtained from the above operation is filled in the anode channel. The anolyte and catholyte are mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 +This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0109] 6. A constant current discharge method was used for testing, and a long-term continuous discharge experiment was conducted on the lignin-based fuel cell at a voltage of 0.3V. During this period, when C8~C8 were detected in the anolyte... 16 Power generation ceases when the molar concentration of the component reaches 20%. For example... Figure 8 As shown, at a voltage of 0.3V, 1g of enzymatic hydrolysis of lignin can generate 500mWh of electricity.

[0110] 7. The obtained anolyte was extracted with ethyl acetate. The resulting extract was the precursor component of the co-produced aviation fuel. The product in the extract was sent for GC-MS analysis. The sample was filtered through a 0.22 μm microporous membrane and then directly loaded for GC-MS analysis. The column was HP-5MS (30.0 m × 250 μm, 0.25 μm); the initial temperature was 40 °C and held for 1 min, then increased to 120 °C at a rate of 5 °C / min, and then increased to 280 °C at a rate of 10 °C / min and held for 15 min; the vaporization chamber temperature was 280 °C; the transfer line temperature was 300 °C; the carrier gas was He; the carrier gas flow rate was 1.0 mL / min; the split ratio was 20:1; and the injection volume was 1 μL. The mass spectrometry conditions were: EI source; electron energy 70 eV; ion source temperature 230 °C; quadrupole 150 °C; scan mode: Scan; scan mass range: 20–500 μ.

[0111] Test results are as follows Figure 9 As shown. From Figure 9 It can be seen that the long-term power generation products of flow fuel cells include straight-chain hydrocarbons, aromatic hydrocarbons, and cycloalkanes, and can produce C8 to C6 hydrocarbons after prolonged power generation. 16 Small molecule substances, similar to aviation fuel precursors, can be further hydrogenated and deoxygenated to produce aviation fuel, which has great commercial prospects and utilization value.

[0112] Example 6: A method for preparing aviation fuel components using aviation fuel precursor solutions generated from cogeneration, comprising the following steps:

[0113] The extract from Example 5 was subjected to solvent evaporation by heating to obtain a solid lignin degradation product. 0.01 g of this lignin degradation product, 0.05 g of Pt / C catalyst powder (brand: Macklin, manufacturer: Guangzhou Rongman Biotechnology, catalog number: P822267-1g), and 10 mL of cyclohexane solvent were added to a high-pressure reactor. After removing air from the reactor, 5 MPa of high-pressure hydrogen gas was introduced, and the reaction was heated and stirred at 180°C for 8 hours. The yield of the product was then detected by gas chromatography. Hexane was used as an internal standard, and the conversion, yield, and selectivity were calculated using the internal standard method. The calculation formulas are as follows:

[0114]

[0115] Among them, f i and f s These are the correction factors for the analyte and the internal standard, respectively, calculated using the effective carbon number method. A i and A s These are the peak areas of the analyte and the internal standard, respectively, in m. s For the quality of the internal standard, m i The mass of the sample was determined. Results showed that the aviation fuel component yield was approximately 25%, and the conversion rate was approximately 69%.

[0116] Comparative Example 2: The effect of using graphite felt as the anode electrode on lignin liquid flow fuel cells

[0117] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0118] 2. Preparation of anolyte: Weigh 4g of NaOH and dissolve it in 50ml of deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0119] 3. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0120] 4. Battery assembly and electrical performance measurement: The LFFC consists of two all-carbon graphite electrodes with serpentine flow channels, and has a total effective area of ​​1 cm². 2 The Nafion 211 membrane separates the flow channels. Graphite felt fills the cathode channel, and graphite felt fills the anode channel. The anolyte and catholyte flow rates are 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 +This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0121] The battery's electrical performance was tested using the scanning current method, and the results are as follows: Figure 10 As shown, the maximum voltage is 1.45V and the maximum current density is 465.62mA / cm². 2 The maximum power density is 139.09 mW / cm³. 2 The performance is far inferior to that of the graphite felt / high-entropy MOF electrode obtained by hydrothermal reaction for 12 hours in Example 3. Therefore, the graphite felt / high-entropy MOF electrode can achieve efficient degradation of lignin and power generation.

[0122] Comparative Example 3: Effect of calcined CoNiCuMnMo-HEO / GF(N2) electrode on fuel cell

[0123] 1. Before use, the graphite felt should be pretreated by ultrasonic cleaning in acetone for 15 minutes, rinsing several times with deionized water, then transferring it to a 75% hydrochloric acid solution for ultrasonic cleaning for 15 minutes. After ultrasonic cleaning, rinse several times with deionized water and then transfer it to concentrated nitric acid for ultrasonic cleaning for 15 minutes. Finally, rinse several times with deionized water and then soak the carbon cloth in anhydrous ethanol for later use.

[0124] 2. Preparation of CoNiCuMnMo-HEO / GF(N2) electrodes: 3 mmol CoCl5·6H2O, 3 mmol NiCl2·6H2O, 3 mmol CuCl2, 3 mmol MnCl2·4H2O, 3 mmol MoCl5, and 9 mmol 2,5-dihydroxyterephthalic acid were dissolved in a mixed solution of 39 ml N,N-dimethylformamide, 3 ml anhydrous ethanol, and 3 ml water to obtain a hydrothermal reaction solution. Two pretreated 5 cm × 0.5 cm × 0.5 cm graphite felts were adhered to the solution with medical tape and placed in the hydrothermal reaction solution to ensure sufficient reaction. The hydrothermal reaction was carried out at 120 °C in a high-pressure reactor for 24 h. After the reaction, the samples were removed, washed several times with deionized water, and dried to obtain two CoNiCuMnMo-MOF / GF electrodes. One of the dried samples was placed in a muffle furnace and calcined at 500℃ for 2 hours with N2 to obtain a calcined CoNiCuMnMo-HEO / GF(N2) electrode. The heating rate was 5℃ / min.

[0125] 3. Preparation of anolyte: Weigh 4g NaOH and dissolve it in 50ml deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0126] 4. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0127] 5. Battery Assembly and Electrical Performance Measurement: Two battery systems were constructed. The LFFC consisted of two all-carbon graphite electrodes with serpentine flow channels, and had a total effective area of ​​1 cm². 2 The Nafion 211 membrane was used as a separator. Graphite felt was filled in the cathode channels of both battery systems. The CoNiCuMnMo-MOF / GF electrode obtained from the above operation and the calcined CoNiCuMnMo-HEO / GF(N2) electrode were each filled in the anode channel of one battery system. The anolyte and catholyte were mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 + This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0128] The battery's electrical performance was tested using the scanning current method, and the results are as follows: Figure 11 As shown, the maximum power density of the calcined CoNiCuMnMo-HEO / GF(N2) electrode is 250 mW / cm². 2 Compared with the uncalcined CoNiCuMnMo-MOF electrode under the same conditions, the performance is worse, which proves that the CoNiCuMnMo-MOF / GF electrode is more conducive to improving battery performance and lignin oxidation. Moreover, the battery power density corresponding to the calcined CoNiCuMnMo-HEO / GF(N2) electrode is much lower than the power density under the optimal conditions in Example 3.

[0129] Comparative Example 4: CoNiFe-LDH / NF nanowire electrode used in lignin flow fuel cell

[0130] 1. Preparation of CoNiFe-LDH / NF nanowire electrode: 2 mmol Co(NO3)2·6H2O, 1 mmol NiCl2·6H2O, 0.5 mmol FeCl3·6H2O, 5 mmol NH4F, and 5 mmol urea were dissolved in 50 mL of deionized water. A 4 cm × 1 cm × 0.7 cm nickel foam was added for impregnation, and the mixture was placed in a high-pressure reactor for hydrothermal reaction at 140 °C for 6 h. After the reaction, the sample was removed, washed with deionized water, and dried to obtain the CoNiFe-LDH / NF nanowire electrode.

[0131] 2. Preparation of anolyte:

[0132] Weigh 4g of NaOH and dissolve it in 50ml of deionized water, stirring for 10 minutes. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10 minutes, and filter to obtain the anolyte of the lignin alkaline solution.

[0133] 3. Preparation of cathode electrolyte:

[0134] Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, then stir at room temperature. Next, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while continuously stirring. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Measure 100ml of this electrolyte as the cathode electrolyte.

[0135] 4. Battery System Construction and Electrical Performance Testing: The battery system, LFFC, was constructed, consisting of two all-carbon graphite electrodes with serpentine flow channels, and a total effective area of ​​1 cm². 2 The Nafion 211 film is used as a separator. Graphite felt is filled in the cathode channel, and the CoNiFe-LDH / NF nanowire electrode obtained by the above operation is filled in the anode channel. The anolyte and catholyte are mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 + This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0136] The electrical performance of the fuel cell was tested using the scanning current method. The constructed fuel cell had a maximum voltage of 1.56V and a maximum power density of 263.5mW / cm³. 2 The power density is much lower than that of Embodiment 3 of this application.

[0137] Comparative Example 5: Using a foamed nickel anode with a solid electrocatalyst supported for use in a lignin-based liquid flow fuel cell

[0138] 1. Preparation of CoS@Ni foam electrode: Cut the nickel foam into 2cm pieces. 2 ×3cm 2 The sheet-like nickel foam was ultrasonically cleaned using concentrated hydrochloric acid, anhydrous ethanol, and deionized water. Then, the nickel foam was dried in an oven at 60°C for 1 hour. An electrodeposition solution was prepared by mixing 0.05 mol / L CoCl2 and 0.5 mol / L CH4N2S. A CoS@Ni foam electrode was prepared for 30 minutes at a constant voltage of -1 V vsAg / AgCl using chronoamperometry. The prepared CoS@Ni foam electrode was washed with deionized water and dried at 60°C for 1 hour.

[0139] 2. Preparation of anolyte: Weigh 4g of NaOH and dissolve it in 50ml of deionized water, stirring for 10min. Then weigh 2g of enzymatically hydrolyzed lignin, add it to the solution, stir for 10min, and filter to obtain the anolyte of lignin alkaline solution.

[0140] 3. Preparation of the cathode electrolyte: Weigh 20g of vanadium pentoxide powder and add it to a beaker containing 524ml of deionized water, and stir at room temperature. Then, slowly add 76ml of 98.3% concentrated sulfuric acid to the solution while stirring continuously. After 24 hours, add 4ml of nitric acid and continue stirring until a clear, bright yellow solution forms. Let it stand for 72 hours to obtain the high-valence vanadium cathode electrolyte. Take 100ml of this electrolyte as the cathode electrolyte.

[0141] 4. Battery Assembly and Electrical Performance Measurement: Construct the battery system. The LFFC consists of two all-carbon graphite electrodes with serpentine flow channels, and has a total effective area of ​​1 cm². 2 The Nafion 211 membrane is used as a separator. Graphite felt is filled in the cathode channel, and the CoS@Ni foam electrode obtained from the above operation is filled in the anode channel. The anolyte and catholyte are mixed at 10 mL / min. -1 The LFFC was pumped in at a flow rate of 40 mL / min under nitric acid catalysis. -1 The flow rate injects oxygen into the cathode, causing the VO generated at the cathode to... 2+ Oxidized to VO2 + This allows for the regeneration of the cathode electrolyte. The LFFC system operates at 90°C. Sample cell performance was tested using the 857 flow battery testing system.

[0142] The battery performance was tested using the scanning current method. The constructed fuel cell had a maximum voltage of 1.38V and a maximum power density of 176mW / cm³. 2 It can be seen that the voltage and power density are much lower than those in Embodiment 3 of this application.

[0143] Table 1 is a comprehensive comparison of the above embodiments and comparative examples in terms of operating temperature, open-circuit voltage, and maximum power density.

[0144] Table 1. Comprehensive Comparison of Lignin-Based Flow Fuel Cell Systems

[0145]

[0146]

[0147] Comparing all examples and comparative examples, it is evident that the battery with the best power generation performance is the lignin-based fuel cell system constructed in Example 3 using an electrocatalyst prepared by hydrothermal reaction for 12 hours and enzymatically hydrolyzed lignin as raw material. It achieves an open-circuit voltage of 1.58V and a maximum power density of 545.48 mW / cm³. 2 This is far higher than the comparative ratio.

[0148] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. Use of a graphite felt / high-entropy MOF composite in a lignin-based fuel cell, characterized in that, The graphite felt / high-entropy MOF composite material is used as an anode electrode of a lignin-based fuel cell. The graphite felt / high-entropy MOF composite material is prepared by the following steps: The soluble cobalt salt, the soluble nickel salt, the soluble copper salt, the soluble manganese salt, the soluble molybdenum salt and 2,5-dihydroxyterephthalic acid are dissolved in a solvent, a graphite felt is added, and a hydrothermal reaction is carried out in a high-pressure reactor; after the reaction is completed, the graphite felt sample is taken out, washed, and dried to obtain the graphite felt / high-entropy MOF composite material.

2. Use according to claim 1, characterized in that, The molar ratio of the soluble cobalt salt, the soluble nickel salt, the soluble copper salt, the soluble manganese salt and the soluble molybdenum salt is (0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5); And / or, the soluble cobalt salt, the soluble nickel salt, the soluble copper salt, the soluble manganese salt and the soluble molybdenum salt are CoCl5·6H2O, NiCl2·6H2O, CuCl2, MnCl2·4H2O and MoCl5, respectively; And / or, the concentration of the soluble cobalt salt, the soluble nickel salt, the soluble copper salt, the soluble manganese salt and the soluble molybdenum salt in the solvent is 0.01-0.18 mol / L; And / or, the molar ratio of the soluble cobalt salt and 2,5-dihydroxyterephthalic acid is (0.5-1.5):(1-4); And / or, the temperature of the hydrothermal reaction is 20-200 ℃, and the time is 2-24 h; And / or, the solvent is N,N-dimethylformamide, anhydrous ethanol and water in a volume ratio of (10-15):(0.5-1.5):(0.5-1.5).

3. A lignin-based fuel cell, characterized by, The anode electrolyte and the anode electrode; wherein the anode electrolyte is a lignin alkali solution, and the anode electrode is the graphite felt / high-entropy MOF composite material according to any one of claims 1-2.

4. The lignin-based fuel cell of claim 3, wherein, The concentration of lignin in the lignin alkali solution is 1-100 g / L; And / or, the concentration of hydroxyl ions in the lignin alkali solution is 0.02-10 mol / L; And / or, the alkali used in the lignin alkali solution is at least one of NaOH, KOH and ammonia water; And / or, the lignin used in the lignin alkali solution is at least one of enzymatic hydrolysis lignin, pre-hydrolysis lignin, lignin sulfonate and alkali lignin.

5. The lignin-based fuel cell according to claim 3 or 4, wherein, The cathode electrolyte further comprises a pentavalent vanadium salt, an acid solution and an oxidizing agent; The pentavalent vanadium salt is at least one of vanadium pentoxide, vanadyl nitrate and vanadyl sulfate; The concentration of the pentavalent vanadium salt in the cathode electrolyte is 0.05-5 mol / L; The acid solution is at least one of hydrochloric acid aqueous solution, sulfuric acid aqueous solution and nitric acid aqueous solution; The concentration of the acid solution is 0.05-8.0 mol / L; The oxidizing agent is at least one of nitric acid and oxygen; the concentration of the nitric acid in the cathode electrolyte is 0.01-8 mol / L; The flow rate of the oxygen introduced into the cathode electrolyte is 10-120 mL / min; And / or, the cathode electrode further comprises a graphite felt. And / or, the lignin-based fuel cell has an operating temperature of 20-120 ℃.

6. A method for cogeneration of a wood-based fuel cell aviation fuel component according to any one of claims 3 to 5, characterized in that, The method comprises the following steps: The lignin-based fuel cell is operated at 20-120 ℃, and the lignin in the anode electrolyte is depolymerized, the depolymerization product is extracted, and then subjected to a hydrodeoxygenation treatment to obtain an aviation fuel component.

7. The method of claim 6, wherein, The lignin-based fuel cell has an operating temperature of 80-110 ℃. And / or, the solvent used for extraction is at least one of ethyl acetate, isopropyl acetate and butyl acetate.

8. The method of claim 6 or 7, wherein, The hydrodeoxygenation treatment has a temperature of 150-210 ℃ and a time of 6-10 h. And / or, the hydrodeoxygenation treatment is carried out in the presence of a catalyst, the catalyst is at least one of a Pt / C catalyst and a Fe-based catalyst, and the mass ratio of the depolymerization product to the catalyst is (0.5-1):(3-5). And / or, the hydrodeoxygenation treatment is carried out in a high-pressure reaction kettle, the solvent is at least one of cyclohexane and n-octane, and the ratio of the depolymerization product to the solvent is 0.5-1.5 mg:0.5-1.5 mL. And / or, the hydrogen pressure of the hydrodeoxygenation treatment is 3-5 MPa.

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