A modified graphite felt electrode, its preparation and its application in lignin-based fuel cells

Abstract

This invention discloses a modified graphite felt electrode, its preparation, and its application in lignin-based fuel cells. The modified graphite felt electrode described in this invention is a CoS2 / CoS heterojunction modified graphite felt electrode. By modifying the anode graphite felt electrode of the battery, its electrocatalytic activity is significantly improved, thereby enhancing battery performance. This invention also uses potassium triiodide as an oxidant to oxidize and degrade lignin as the anode electrolyte, and uses the CoS2 / CoS heterojunction modified graphite felt electrode as the anode to construct a lignin-based fuel cell system. This achieves efficient degradation of industrial lignin while simultaneously utilizing the chemical energy released during the degradation process to generate electricity, thus achieving high-value utilization of industrial lignin.

Description

Technical Field

[0001] This invention belongs to the fields of ecological environment and new energy, specifically relating to a modified graphite felt electrode, its preparation, and its application in lignin-based fuel cells. Background Technology

[0002] Biomass is primarily composed of three components: cellulose, hemicellulose, and lignin. Of all the chemical components of biomass, lignin is the main component, found in softwoods, hardwoods, and grasses. Lignin is a biomass renewable energy source that is abundant on Earth but underestimated and underutilized. Structurally, lignin is a complex amorphous three-dimensional biomolecule with a benzene ring backbone, resulting from the random repetition of methoxy-hydroxycinnamyl alcohol units linked together by different types of COC and CC unit bonds and various functional methoxy, carbonyl, hydroxyl, and carboxyl groups.

[0003] However, lignin's complex structure and low reactivity limit its further applications. Although a significant amount of lignin is separated from papermaking and chemical pulping, only a very small amount is used as high-value products such as adhesives, dispersants, and fillers. The vast majority is either incinerated as cheap fuel or indiscriminately discharged, resulting in extremely low resource utilization. The biggest challenge facing lignin application technology is that the structural complexity, variability, and chemical stubbornness of lignin make it very difficult to convert it into fine chemicals, polymers, and materials using green and efficient methods. This difficulty in utilizing this resource underscores the greater commercial value of developing lignin products.

[0004] The conversion of biomass energy into clean electricity has always been a research focus. Traditional biomass power generation, also known as direct combustion power generation, involves burning lignin directly in a boiler, with the resulting steam driving a steam turbine and generator to produce electricity. This technology suffers from problems such as low thermal conversion efficiency and high costs associated with the collection, transportation, and storage of biomass.

[0005] Fuel cell technology can directly convert the chemical energy in fuel into electrical energy. This technology boasts advantages such as high power generation efficiency and low environmental pollution, and is considered a next-generation power generation technology. In recent years, biomass-based fuel cells have attracted considerable attention, including solid oxide fuel cells, microbial fuel cells, photovoltaic fuel cells, and redox flow fuel cells. However, current fuel cells using industrial lignin as fuel suffer from drawbacks such as severe lignin aggregation and low reactivity, resulting in slow electron transfer rates and low power density. This exacerbates the difficulty of lignin utilization, hindering the high-value utilization of industrial lignin.

[0006] Therefore, developing efficient, high-power-density fuel cells that can directly utilize lignin as fuel is a pressing problem that needs to be solved.

[0007] Furthermore, the electrode is the site where electrochemical redox reactions occur in the active materials, significantly impacting fuel cell performance. Graphite felt is currently a typical electrode material for biomass fuel cells. This carbon material possesses a three-dimensional structure and advantages such as high stability and high conductivity. However, due to shortcomings such as small specific surface area, strong hydrophobicity, and low electrochemical catalytic activity, the original graphite felt electrode requires modification. Optimizing the electrode to achieve the best battery performance remains a pressing issue. Summary of the Invention

[0008] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing modified graphite felt electrodes.

[0009] This invention significantly improves the electrocatalytic activity of the graphite felt electrode at the battery anode by modifying it, thereby enhancing battery performance.

[0010] Another object of the present invention is to provide a modified graphite felt electrode prepared by the above preparation method.

[0011] Another object of the present invention is to provide the application of the above-mentioned modified graphite felt electrode in lignin-based fuel cells.

[0012] Another object of the present invention is to provide a lignin-based fuel cell.

[0013] This invention constructs a lignin-based fuel cell system that efficiently degrades industrial lignin while simultaneously generating electricity by fully utilizing the chemical energy released during the degradation process, thus achieving high-value utilization of industrial lignin.

[0014] The objective of this invention is achieved through the following technical solution:

[0015] A method for preparing a modified graphite felt electrode includes the following steps:

[0016] Cobalt salt, urea, and sulfur source were mixed in an organic solvent to obtain a precursor solution. Graphite felt was placed in the precursor solution and hydrothermally reacted in a hydrothermal reactor at 20–200°C for 0.5–20 hours. After cooling, the electrode was washed and dried to obtain a CoS2 / CoS heterojunction modified graphite felt electrode.

[0017] Preferably, the molar ratio of the cobalt salt, urea and sulfur source is 1-5:5-20:10-50; more preferably, it is 2:10:25.

[0018] Preferably, the organic solvent is a mixture of ethylene glycol (EG) and dimethylformamide (DMF) in a volume ratio of 0.1-2:0.5-3; more preferably, it is a mixture of ethylene glycol (EG) and dimethylformamide (DMF) in a volume ratio of 0.9:1.

[0019] Preferably, the ratio of the cobalt salt to the organic solvent is 0.1–2 mmol: 20–50 ml; more preferably, it is 1 mmol: 35 ml.

[0020] Preferably, the cobalt salt is at least one of cobalt sulfate (CoSO4·7H2O), cobalt carbonate (CoCO3), and cobalt nitrate (Co(NO3)2); more preferably, it is cobalt sulfate (CoSO4·7H2O).

[0021] Preferably, the sulfur source is at least one of sublimed sulfur and hydrogen sulfide; more preferably, it is sublimed sulfur.

[0022] Preferably, the washing refers to washing with water several times until there are no obvious CoS2 / CoS particles in the wastewater; the drying conditions are drying at 40-80°C for 10-20 hours; more preferably, the drying conditions are drying at 60°C for 12 hours.

[0023] A modified graphite felt electrode prepared by the above method.

[0024] The above-mentioned modified graphite felt electrode is used in lignin-based fuel cells.

[0025] A lignin-based fuel cell includes an anode electrolyte and a cathode electrolyte; the anode electrolyte is obtained by dissolving potassium iodide and elemental iodine in water at a molar ratio of 1-5:0.1-3, adding lignin, and then heating the mixture to react.

[0026] The potassium iodide and iodine react to generate KI3, which acts as an oxidant to oxidize and degrade lignin under heating conditions.

[0027] Preferably, the concentration of potassium iodide in the anolyte is 0.5–3 mol / L, and more preferably 1–2 mol / L.

[0028] Preferably, the concentration of lignin in the anolyte is 4–40 g / L.

[0029] Preferably, the lignin is at least one of alkali lignin, sodium lignin sulfonate, pre-hydrolyzed lignin, and enzymatically hydrolyzed lignin; more preferably, it is alkali lignin.

[0030] Preferably, the heating reaction is carried out at a temperature of 70–90°C for 1–9 hours.

[0031] Preferably, the lignin-based fuel cell further includes the modified graphite felt electrode described above, which serves as the anode electrode.

[0032] Preferably, the cathode electrolyte is a 0.5-5 mol / L vanadium oxysulfate solution, obtained by reacting V2O5, H2SO4 and water.

[0033] More preferably, the H2SO4 is a concentrated sulfuric acid solution with a mass fraction of 90-98%, and its ratio with V2O5 is 10-60 ml: 2-20 g; the ratio of V2O5 with water is 1-20 g: 50-500 ml.

[0034] More preferably, the reaction is carried out under ice bath conditions for 5 to 24 hours, and H2SO4 is added to the reaction system dropwise.

[0035] Preferably, the lignin-based fuel cell further includes a graphite felt electrode as a cathode electrode.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] (1) This invention uses industrial lignin as a direct fuel, which reduces costs while realizing the high-value utilization of industrial lignin.

[0038] (2) The present invention uses KI3, an oxidant that is inexpensive, environmentally friendly and easy to handle, to generate clean electricity from industrial lignin under simple heating conditions.

[0039] (3) This invention can degrade industrial lignin with KI3 through heating alone, which greatly reduces energy consumption and cost. At the same time, it can also convert biomass energy into clean electricity.

[0040] (4) In this invention, two sulfides (CoS2 / CoS) with different band structures are synthesized on a graphite felt electrode and a heterojunction is formed between them. The uneven charge distribution of the heterojunction will enhance the electrocatalytic activity of the electrode by enhancing the charge transfer activity.

[0041] (5) The present invention uses only one-step hydrothermal method to modify the electrode, which greatly reduces energy consumption and cost.

[0042] (6) The present invention uses modified graphite felt as the anode electrode of fuel cell, which improves the anode electron transfer efficiency and thus improves battery performance. Attached Figure Description

[0043] Figure 1 The graph shows the power generation performance of the battery in Example 1 under different anolytes.

[0044] Figure 2 The graph shows the power generation performance of alkali lignin at different reaction temperatures in Example 2.

[0045] Figure 3 The graph shows the power generation performance of alkali lignin at different reaction times in Example 3.

[0046] Figure 4 This is a SEM image of GF-CoS2 / CoS in Example 4.

[0047] Figure 5 The image shows the XRD pattern of the CoS2 / CoS nanoheterostructure in Example 5.

[0048] Figure 6 The image shows the HRTEM and EDX elemental analysis results of the CoS2 / CoS nanoheterostructure in Example 6.

[0049] Figure 7 This is a comparison chart of the power generation performance of the battery before and after modification of the anode graphite felt electrode in Example 7.

[0050] Figure 8 The graph shows the power generation performance of different types of lignin as fuel in Example 8.

[0051] Figure 9 The graph shows the power generation performance of alkali lignin degradation by different oxidants in Comparative Examples 1, 2, 3, and 4.

[0052] Figure 10 The present invention provides a process flow for a lignin-based fuel cell.

[0053] Figure 11 This is the process flow for assembling a lignin-based fuel cell using modified graphite felt electrodes according to the present invention. Detailed Implementation

[0054] 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.

[0055] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0056] The cathode electrolytes in the examples and comparative examples were prepared by adding 10 g of V2O5 to 262 ml of water while stirring vigorously, and adding 38 ml of concentrated H2SO4 (98%) solution dropwise to the V2O5 suspension under ice cooling, and reacting for 20 hours.

[0057] Example 1: Effect of different anolytes on battery power generation performance

[0058] 1. Preparation of anolyte: 0.0075g of elemental iodine, 8.3g of potassium iodide, 7.49g of sodium iodide and 3.18g of a mixture of elemental iodine, and 8.3g of potassium iodide and 3.18g of a mixture of elemental iodine were dissolved in deionized water to prepare four 25ml solutions. Then, 1g of alkali lignin was added to each solution, and the mixtures were thoroughly mixed. The solutions were then heated at 90℃ for 3 hours to obtain four different electrolytes for testing.

[0059] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0060] 3. Battery System Construction and Electrical Performance Testing: The electrolyte from step 1 was added to the anolyte tank and placed in an 80°C constant-temperature water bath. The electrolyte from step 2 was added to the cathode electrolyte tank and placed in an 80°C constant-temperature water bath. Graphite felt was used to fill the flow channels of the anode and cathode plates, respectively, and the battery was assembled. The anolyte tank was connected to the anode inlet and outlet of the battery using conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to its operating temperature of 80°C, and its electrical performance was tested using the scanning current method. The results are as follows: Figure 1 As shown in the figure, the battery performance is optimal when potassium iodide and elemental iodine are mixed as the anolyte, with a maximum voltage of 0.86V and a maximum current density of 1363.6mA / cm². 2 The maximum power density is 200mW / cm³. 2 Iodine is poorly soluble in water, but it dissolves well in iodized salts to form triiodide, thus exerting its function. In this embodiment, potassium iodide and sodium iodide are selected as supporting electrolytes to combine with iodine to form potassium triiodide and sodium triiodide, respectively. As can be seen from the above, potassium triiodide, formed by potassium iodide as a supporting electrolyte and combining with iodine, can effectively oxidize and degrade alkali lignin and generate electricity efficiently.

[0061] Example 2: Electrogenicity of KI3 Degrading Alkali Lignin at Different Reaction Temperatures

[0062] 1. Preparation of anolyte: Dissolve 8.3g potassium iodide and 3.18g iodine in 25ml deionized water to prepare three identical mixtures (25ml each). Then add 1g alkali lignin to each mixture, mix thoroughly, and heat at 70℃, 80℃, and 90℃ for 3h respectively to obtain three anolytes obtained under different heating conditions, which are then tested.

[0063] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0064] 3. Battery System Construction and Electrical Performance Testing: The electrolyte from step 1 was added to the anolyte tank and placed in an 80°C constant-temperature water bath. The electrolyte from step 2 was added to the cathode electrolyte tank and placed in an 80°C constant-temperature water bath. Graphite felt was used to fill the flow channels of the anode and cathode plates, respectively, and the battery was assembled. The anolyte tank was connected to the anode inlet and outlet of the battery using conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to its operating temperature of 80°C, and its electrical performance was tested using the scanning current method. The results are as follows: Figure 2 As shown in the figure, the battery constructed with the electrolyte pretreated at 70℃ has a maximum voltage of 0.76V and a maximum current density of 948.1mA / cm². 2 The maximum power density is 150.8 mW / cm³. 2 The battery constructed with electrolyte pretreated at 90℃ exhibited the best performance, with a maximum voltage of 0.86V and a maximum current density of 1363.6mA / cm². 2 The maximum power density is 200mW / cm³. 2 As shown above, battery performance increases with increasing reaction temperature. However, considering that lignin may carbonize during prolonged reactions at 100℃, clogging the battery and preventing it from operating for extended periods, and that high temperatures can cause lignin to condense and form recalcitrant polymers, thus hindering the high-value utilization of lignin, and that controlling the reaction temperature below 100℃ is beneficial for energy conservation, the optimal reaction temperature for the anolyte is set at 90℃. The reaction temperature significantly affects the rate of potassium triiodide degradation of alkali lignin and battery performance; at 90℃, potassium triiodide exhibits the best efficiency in degrading alkali lignin and optimal power generation performance.

[0065] Example 3: Power generation performance of KI3 degrading alkali lignin at different reaction times

[0066] 1. Preparation of anolyte: Dissolve 8.3g potassium iodide and 3.18g iodine in 25ml deionized water to prepare 4 identical mixtures (25ml each). Then add 1g alkali lignin to each mixture, mix thoroughly, and heat at 90℃ for 1h, 3h, 5h, and 7h respectively to obtain 4 different anolytes with different heating reaction times, which are then tested.

[0067] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0068] 3. Battery system construction and electrical performance testing: The construction method is the same as in Example 2, and the results are as follows. Figure 3 As shown, battery performance improves with increasing reaction time, reaching a maximum voltage of 0.87V and a maximum current density of 1388.7mA / cm² after 7 hours. 2 The maximum power density is 218.05 mW / cm³. 2At the beginning of the reaction, the battery performance increased rapidly over time, but after 3 hours the increase in battery performance was not significant, indicating that KI3 can efficiently oxidize and degrade alkali lignin in a short period of time.

[0069] Example 4: Modification of graphite felt (GF) electrode by one-step hydrothermal method

[0070] 1. Preparation of precursor solution: Mix 40.16 mg CoSO4·7H2O, 42.24 mg urea and 56.12 mg sublimed sulfur in a mixed solution of 33.2 ml ethylene glycol (EG) and 36.8 ml dimethylformamide (DMG), stir magnetically for 1 hour, and set aside for use.

[0071] 2. Place the graphite felt (1.3cm×1.3cm×3mm) in the precursor solution from step 1, and then transfer it to a 100ml polytetrafluoroethylene-lined autoclave. Keep the autoclave at 180℃ in an oven for 12 hours to obtain GF-CoS2 / CoS.

[0072] 3. Morphological characterization of the modified electrode: The modified electrode was characterized using scanning electron microscopy, and the results are as follows: Figure 4 As shown, CoS2 / CoS is uniformly loaded on the graphite felt, and the calculated loading is approximately 1.0 mg / cm³. 2 .

[0073] Example 5: XRD characterization of CoS2 / CoS nanoheterostructures

[0074] 1. Preparation of CoS2 / CoS nanoheterojunctions: 40.16 mg CoSO4·7H2O, 42.24 mg urea and 56.12 mg sublimed sulfur were mixed in a mixed solution of 33.2 ml ethylene glycol (EG) and 36.8 ml dimethylformamide (DMG), and magnetically stirred for 1 hour. Then the mixture was transferred to a 100 ml polytetrafluoroethylene-lined autoclave and kept in an oven at 180 °C for 12 hours to obtain CoS2 / CoS nanoheterojunctions.

[0075] 2. XRD characterization of CoS2 / CoS: The composition and structure of the prepared materials were analyzed using XRD, such as... Figure 5 As shown in the figure, all diffraction peaks of the prepared material can be well indexed to cubic CoS2 (JCPDS 89-1492) and hexagonal CoS (JCPDS 65-3418). The XRD pattern of the prepared material is consistent with the predicted theoretical patterns of CoS2 and CoS crystal structures, and no impurities were found, thus confirming that the prepared material is a CoS2 / CoS heterojunction.

[0076] Example 6: Characterization of the structure and composition of CoS2 / CoS nanoheterojunctions

[0077] 1. Preparation of CoS2 / CoS nanoheterojunctions: 40.16 mg CoSO4·7H2O, 42.24 mg urea and 56.12 mg sublimed sulfur were mixed in a mixed solution of 33.2 ml ethylene glycol (EG) and 36.8 ml dimethylformamide (DMG), and magnetically stirred for 1 hour. Then the mixture was transferred to a 100 ml polytetrafluoroethylene-lined autoclave and kept in an oven at 180 °C for 12 hours to obtain CoS2 / CoS nanoheterojunctions.

[0078] 2. High-resolution transmission electron microscopy (HRTEM) characterization of CoS2 / CoS: To investigate the structure of the CoS2 / CoS nanoheterojunction on the graphite felt electrode, HRTEM was used to analyze and characterize the morphology of the CoS2 / CoS prepared in Example 5, such as... Figure 6 As shown. Figure 6 Figure a shows CoS2 / CoS particles with a size of 100 nm. Figure 6 Images b and c are HRTEM images, showing clear lattice fringes, indicating good crystallization of the nanoparticles, and the corresponding crystal planes of CoS2 and CoS are identified by comparison with XRD. Additionally, Figure 6 The absence of obvious amorphous regions at the CoS2 / CoS interface in the C-type structure confirms the formation of the heterostructure. From... Figure 6 High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and Figure 6 The energy-dispersive X-ray spectroscopy (EDX) elemental analysis of the CoS2 / CoS heterojunctions in samples e and f shows that the uniform distribution of Co and S is consistent with the morphology of the CoS2 / CoS heterojunction. Therefore, this further confirms the formation of the CoS2 / CoS heterojunction.

[0079] Example 7: Power generation performance of fuel cell using modified graphite felt electrode (GF-CoS2 / CoS)

[0080] 1. Mix 40.16 mg CoSO4·7H2O, 42.24 mg urea, and 56.12 mg sublimed sulfur in a mixed solution of 33.2 ml ethylene glycol (EG) and 36.8 ml dimethylformamide (DMG). Stir magnetically for 1 hour. Then transfer the precursor solution to a 100 ml polytetrafluoroethylene-lined autoclave and place a graphite felt (1.3 cm × 1.3 cm × 3 mm) inside. Place the autoclave in an oven and maintain at 180 °C for 12 hours to obtain GF-CoS2 / CoS.

[0081] 2. Preparation of anolyte: Dissolve 8.3g potassium iodide and 3.18g iodine in 25ml deionized water to prepare two identical mixtures (25ml each). Then add 1g alkali lignin to each mixture, mix them evenly, and heat at 90℃ for 3h to obtain the anolyte.

[0082] 3. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0083] 4. Battery System Construction and Electrical Performance Testing: To demonstrate the significant role of CoS2 / CoS modified graphite felt in improving battery performance, this embodiment compares and studies the performance differences of assembled fuel cells using graphite felt (GF) and CoS2 / CoS modified graphite felt (GF-CoS2 / CoS) as the anode electrode materials, respectively. Specifically, the electrolyte prepared in step 2 was added to the anode electrolyte tank and placed in an 80°C constant temperature water bath. The cathode electrolyte prepared in step 3 was stored in the cathode electrolyte tank and placed in an 80°C constant temperature water bath. GF and GF-CoS2 / CoS were used as anode electrode materials to fill the anode plate channels, while graphite felt was used in both the cathode plate channels. The anode electrolyte tank was connected to the anode inlet and outlet of the battery via conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to the operating temperature of 80°C, and the electrical performance of the battery was tested using the scanning current method. The results are as follows: Figure 7 As shown in the figure, when unmodified virgin graphite felt (GF) is used as the electrode, the maximum voltage of the battery is 0.86V and the maximum current density is 1363.6mA / cm². 2 The maximum power density is 200mW / cm³. 2 When CoS2 / CoS modified graphite felt is used as the electrode, the maximum voltage of the battery is 0.88V and the maximum current density is 2350.4mA / cm². 2 The maximum power density is 400 mW / cm³. 2 It is evident that, compared to the unmodified state, the maximum power density of the battery using graphite felt as an electrode after CoS2 / CoS modification increased by 2 times.

[0084] Example 8: Power generation performance of GF-CoS2 / CoS modified fuel cells based on different lignin fuels

[0085] 1. Preparation of anolyte: Dissolve 8.3g potassium iodide and 3.18g iodine in 25ml deionized water to prepare 4 identical mixtures. Then add 1g alkali lignin, sodium lignin sulfonate, enzymatically hydrolyzed lignin, and pre-hydrolyzed lignin to each mixture. After uniform mixing, heat the mixture at 90℃ for 3h to obtain 4 kinds of anolytes.

[0086] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0087] 3. Battery System Construction and Electrical Performance Testing: This embodiment investigated the performance of assembled fuel cells using different types of lignin as fuel. Specifically, the electrolyte prepared in step 1 was added to the anolyte tank and kept in an 80°C constant temperature water bath. The cathode electrolyte prepared in step 2 was stored in the cathode electrolyte tank and kept in an 80°C constant temperature water bath. GF-CoS2 / CoS was used as the anolyte material and filled into the anode plate channels. Graphite felt was used in both the cathode plate channels. The battery was assembled, and the results are as follows: Figure 8 As shown in the figure. The results indicate that potassium triiodide can effectively degrade various industrial lignins, and different industrial lignins can be efficiently converted into electrical energy. The battery exhibits the best electrical performance when pre-hydrolyzed lignin is used as fuel. The maximum voltage of the battery is 0.94V, and the maximum current density is 2421.48 mA / cm². 2 The maximum power density is 441.54 mW / cm³. 2 Therefore, using potassium triiodide as an anodic oxidant to treat industrial lignin for co-generation power generation has high applicability and realizes the high-value utilization of industrial lignin.

[0088] Comparative Example 1: Power generation performance of ferric chloride oxidative degradation of alkali lignin

[0089] 1. Preparation of anolyte: Dissolve 13.6515g of ferric chloride and 4.2ml of concentrated hydrochloric acid in deionized water to prepare 25ml of a mixture. Add 1g of alkali lignin, mix thoroughly, and heat at 90℃ for 3 hours to obtain the electrolyte. To be tested.

[0090] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0091] 3. Battery System Construction and Electrical Performance Testing: The electrolyte from step 1 was added to the anolyte tank and placed in an 80°C constant-temperature water bath. The electrolyte from step 2 was added to the cathode electrolyte tank and placed in an 80°C constant-temperature water bath. Graphite felt was used to fill the flow channels of the anode and cathode plates, respectively, and the battery was assembled. The anolyte tank was connected to the anode inlet and outlet of the battery using conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to its operating temperature of 80°C, and its electrical performance was tested using the scanning current method. The results are as follows: Figure 9 As shown in the figure, the maximum voltage of the battery composed of the electrolyte treated at 90℃ is 0.545V, and the maximum current density is 608mA / cm². 2 The maximum power density is 67.5 mW / cm³. 2 Compared to Example 1, which used potassium triiodide as the oxidant, the power density decreased by 132.5 mW / cm². 2 .

[0092] Comparative Example 2: Electrogenicity of Copper Chloride Oxidative Degradation of Alkali Lignin

[0093] 1. Preparation of anolyte: Dissolve 8.524g of copper chloride and 4.2ml of concentrated hydrochloric acid in deionized water to prepare 25ml of mixed solution. Add 1g of alkali lignin, mix evenly, and heat at 90℃ for 3h to obtain the electrolyte, which is then tested.

[0094] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0095] 3. Battery System Construction and Electrical Performance Testing: The electrolyte from step 1 was added to the anolyte tank and placed in an 80°C constant-temperature water bath. The electrolyte from step 2 was added to the cathode electrolyte tank and placed in an 80°C constant-temperature water bath. Graphite felt was used to fill the flow channels of the anode and cathode plates, respectively, and the battery was assembled. The anolyte tank was connected to the anode inlet and outlet of the battery using conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to its operating temperature of 80°C, and its electrical performance was tested using the scanning current method. The results are as follows: Figure 9 As shown, the battery composed of an electrolyte treated at 90℃ has a maximum voltage of 0.509V and a maximum current density of 448mA / cm². 2 The maximum power density is 47.5 mW / cm³. 2 Compared to Example 1, which used potassium triiodide as the oxidant, the power density decreased by 152.5 mW / cm². 2 .

[0096] Comparative Example 3: Electrogenic Performance of Copper Chloride / Titanium Oxide Sulphate Synergistic Degradation of Alkali Lignin

[0097] 1. Preparation of anolyte: Dissolve 8.524g of copper chloride, 5g of titanium oxysulfate, and 4.2ml of concentrated hydrochloric acid in deionized water to prepare 25ml of mixed solution. Add 1g of alkali lignin, mix evenly, and heat at 90℃ for 3h to obtain the electrolyte, which is then tested.

[0098] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0099] 3. Battery System Construction and Electrical Performance Testing: The electrolyte from step 1 was added to the anolyte tank and placed in an 80°C constant-temperature water bath. The electrolyte from step 2 was added to the cathode electrolyte tank and placed in an 80°C constant-temperature water bath. Graphite felt was used to fill the flow channels of the anode and cathode plates, respectively, and the battery was assembled. The anolyte tank was connected to the anode inlet and outlet of the battery using conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to its operating temperature of 80°C, and its electrical performance was tested using the scanning current method. The results are as follows: Figure 9 As shown in the figure, the maximum voltage of the battery composed of the electrolyte treated at 90℃ is 0.565V, and the maximum current density is 668mA / cm². 2 The maximum power density is 74.7 mW / cm³.2 Compared to Example 1, which used potassium triiodide as the oxidant, the power density decreased by 125.3 mW / cm². 2 .

[0100] Comparative Example 4: Battery performance using unmodified graphite felt electrodes

[0101] 1. Preparation of anolyte: Dissolve 8.3g potassium iodide and 3.18g iodine in deionized water to prepare 25ml of mixed solution. Add 1g alkali lignin, mix evenly, and heat at 90℃ for 3h to obtain the electrolyte, which is then tested.

[0102] 2. The cathode electrolyte is a pre-prepared vanadium oxysulfate solution.

[0103] 3. Battery System Construction and Electrical Performance Testing: The electrolyte from step 1 was added to the anolyte tank and placed in an 80°C constant-temperature water bath. The electrolyte from step 2 was added to the cathode electrolyte tank and placed in an 80°C constant-temperature water bath. Graphite felt was used to fill the flow channels of the anode and cathode plates, respectively, and the battery was assembled. The anolyte tank was connected to the anode inlet and outlet of the battery using conduits, and the cathode tank was connected to the cathode inlet and outlet of the battery. The battery was heated to its operating temperature of 80°C, and its electrical performance was tested using the scanning current method. The results are as follows: Figure 9 As shown in the figure, the maximum voltage of the battery composed of the electrolyte treated at 90℃ is 0.86V, and the maximum current density is 1363.6mA / cm². 2 The maximum power density is 200mW / cm³. 2 The performance is far lower than that of the battery modified with graphite felt electrode in Example 7.

[0104] As shown above, compared to other oxidants, under the same conditions, potassium triiodide can better oxidize and degrade alkali lignin and generate electricity more efficiently, resulting in significantly higher battery performance. Therefore, KI3 is used as the oxidant because it offers high degradation efficiency and can couple to generate clean electrical energy. Simultaneously, electrode modification significantly improves battery performance. Based on this, a CoS2 / CoS heterojunction is synthesized on the electrode, and after modification, the battery performance is doubled.

[0105] 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.

[0106] Table 1. Comprehensive Comparison of Lignin-Based Fuel Cell Systems

[0107]

[0108] 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. A lignin-based fuel cell, characterized by, The anode electrolyte and the cathode electrolyte; the anode electrolyte is obtained by dissolving potassium iodide and iodine in water according to a molar ratio of 1-5:0.1-3, adding lignin, and then heating and reacting at 70-90 DEG C; The modified graphite felt electrode is used as the anode electrode of the lignin-based fuel cell. The preparation method of the modified graphite felt electrode comprises the following steps: The cobalt salt, urea and sulfur source are mixed in an organic solvent to obtain a precursor solution, the graphite felt is placed in the precursor solution, and the hydrothermal reaction is carried out in a hydrothermal kettle at 20-200 DEG C for 0.5-20 hours, and then the graphite felt is washed and dried after cooling to obtain the CoS2 / CoS heterojunction modified graphite felt electrode.

2. The lignin-based fuel cell of claim 1, wherein, The molar ratio of the cobalt salt, urea and sulfur source is 1-5:5-20:10-50.

3. The lignin-based fuel cell of claim 1, wherein, The organic solvent is a mixed solvent of ethylene glycol and dimethylformamide in a volume ratio of 0.1-2:0.5-3; the ratio of the cobalt salt to the organic solvent is 0.1-2 mmol:20-50 ml.

4. The lignin-based fuel cell of claim 1, wherein, In the anode electrolyte, the concentration of potassium iodide is 0.5-3 mol / L, and the concentration of lignin is 4-40 g / L; the heating reaction time is 1-9 h.

5. The lignin-based fuel cell of claim 1, wherein, The lignin is at least one of alkali lignin, sodium lignosulfonate, pre-hydrolysis lignin and enzymatic hydrolysis lignin.

6. The lignin-based fuel cell of claim 1, wherein, The cathode electrolyte is a vanadyl sulfate solution with a concentration of 0.5-5 mol / L; the vanadyl sulfate solution is obtained by mixing and reacting V2O5, H2SO4 and water; the H2SO4 is a concentrated sulfuric acid solution with a mass fraction of 90-98%, and the ratio of the concentrated sulfuric acid solution to V2O5 is 10-60 ml:2-20 g; the ratio of V2O5 to water is 1-20 g:50-500 ml; the reaction is carried out under ice bath conditions, and the reaction time is 5-24 hours; The lignin-based fuel cell further comprises a graphite felt electrode as a cathode electrode.

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