Preparation method of nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode

Abstract

This invention relates to a method for preparing nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt. Using biomass waste such as wood, bamboo, and bamboo shoot shells as carbon sources, the carbon is pretreated with dilute nitric acid to alter the chemical composition of the cell walls. Oxygen-doped bamboo shoot shell carbon is obtained by high-temperature calcination in a tube furnace under a nitrogen atmosphere. This carbon is then coated onto the surface of the carbon felt using an impregnation method, followed by plasma treatment of the modified carbon felt surface with an ammonia-argon mixture plasma source as the nitrogen source, resulting in a nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode. This electrode exhibits significantly improved hydrophilicity compared to the original carbon felt. The doping of nitrogen and oxygen elements in the biomass carbon catalyst introduces more active sites, enhancing the electrocatalytic activity and reaction kinetic reversibility of the electrode. The modified electrode uses readily available and inexpensive raw materials, making it suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of vanadium redox flow battery energy storage technology, and specifically relates to a method for preparing a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode and its application in vanadium redox flow batteries. Background Technology

[0002] To ensure sustainable economic and ecological development, the world is deploying green energy development to reduce fossil fuel use, achieve energy structure transformation, and reduce environmental pollution. New energy sources such as wind, solar, and tidal power have become new development needs, but the significant intermittency and volatility of renewable energy sources pose serious obstacles to grid integration. Therefore, the development of large-scale renewable energy storage systems is urgently needed. Vanadium redox flow batteries, due to their long cycle life, high safety, fast response speed, flexible design, and low cycle cost, can play a key role in improving renewable energy utilization and ensuring the stability of smart grids. However, existing electrode materials, such as rudimentary carbon felt, while possessing high electronic conductivity and corrosion resistance, suffer from poor hydrophilicity, insufficient electrochemical active sites, and low electrochemical activity. This significantly affects the polarization and efficiency of electrode redox reactions; therefore, developing electrode materials with high electrochemical activity is of great significance.

[0003] Based on extensive previous research, common modification methods include acid treatment, heat treatment, microwave treatment, electrochemical oxidation, and the introduction of catalysts. Catalysts include metals, metal oxides, and carbon-based materials. Among these, carbon-based catalysts have gradually attracted widespread attention from researchers due to their stable physicochemical properties.

[0004] The enormous potential of biomass-derived carbon catalysts is reflected in the following advantages: (1) reasonable cost; (2) feasible structural design; and (3) rich natural pore structure and impurity element content. Therefore, developing biomass-derived carbon catalysts for use in vanadium redox flow battery electrodes is an effective and economical strategy, and is of great significance for promoting its industrialization and seizing the commanding heights of emerging industries.

[0005] Patent CN116154197A discloses a biomass-modified vanadium redox flow battery electrode, its preparation method, and its application. The technical solution yields a modified biomass-deposited heteroatom-doped graphite felt electrode. However, the process is complex and energy-intensive, requiring two high-temperature carbonization steps. Preparing the boron-nitrogen-doped graphite felt electrode requires heating to 800°C and holding for 2 hours in a mixed nitrogen and oxygen atmosphere. After placing the boron-nitrogen-doped graphite felt electrode in a biomass slurry, it needs to be further heated to 800°C and held for 2 hours in a nitrogen atmosphere, with a heating rate of 10~12°C / min to obtain the modified biomass-deposited heteroatom-doped graphite felt. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for preparing a nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode and its application.

[0007] As one aspect of the present invention, the present invention provides a method for preparing a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode, comprising the following steps: (S1) Cut the bamboo shoot shells into slices and put them into a dilute nitric acid solution. Place them in a shaker and shake. Then wash them with deionized water until neutral and dry them in an oven. (S2) The acid-pretreated bamboo shoot shells are heated under a nitrogen atmosphere to obtain oxygen-enriched bamboo shoot shell carbon; (S3) Grind bamboo shoot shell carbon into powder, use N,N-dimethylformamide as solvent to prepare ink, soak the original carbon felt in ink, and put it in an oven to dry, repeating several times until the ink is completely absorbed. (S4) The surface of oxygen-enriched bamboo shoot shell carbon-coated carbon felt is subjected to plasma treatment using a plasma source to obtain a nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode.

[0008] The nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode of the present invention is obtained by sequentially doping biomass carbon with oxygen and nitrogen.

[0009] Preferably, the volume concentration of the dilute nitric acid solution in step (S1) is 5%-20%.

[0010] Preferably, in step (S1), the shaking speed is 100-250 rpm and the oscillation time is 8-15 h.

[0011] Preferably, the heating temperature in step (S2) is 700-900℃ and the heating time is 1-3 h.

[0012] More preferably, the heating temperature in step (S2) is 800°C and the heating time is 2 hours.

[0013] Preferably, in step (S3), the mass-to-volume ratio of bamboo shoot shell carbon powder to solvent is 1-3 g / L. Uniform ink is obtained by ultrasonication for 5-8 hours, and the original carbon felt is cut into 3×4.5cm pieces. 2 After repeated soaking and drying, repeat this process 3 times until the ink is completely absorbed.

[0014] Preferably, in step (S4), the plasma source is one of a single argon plasma source, a single ammonia plasma source, or a mixed argon and ammonia plasma source. The ratio of argon to ammonia in the mixed argon and ammonia plasma source is 2:1, 1:2, or 1:1 (gas flow rate ratio), with a ratio of 2:1 being optimal.

[0015] Preferably, in step (S4), the power of the plasma source is 150-250 W, with 200 W being the optimal power condition.

[0016] Preferably, in step (S4), the plasma treatment time is 20-40 s, with 30 s being the optimal treatment time.

[0017] As another aspect of the present invention, the present invention provides a nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode obtained by the above preparation method.

[0018] As another aspect of the present invention, the present invention provides an application of a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode.

[0019] Specifically, a three-electrode system for a vanadium redox flow battery was constructed using a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode as the working electrode, a platinum electrode as the counter electrode, and an Hg / Hg2SO4 electrode as the reference electrode. The electrolyte composition was 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. A vanadium redox flow battery was also assembled using a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode as the positive electrode, a Nafion 212 membrane as the ion exchange membrane, and an electrolyte composition of 1.5 mol / L VOSO4 and 3.0 mol / L H2SO4. The battery achieved a flow rate of 100 mA / cm². 2 Charge and discharge tests were conducted under the specified conditions.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are: To address the poor hydrophilicity and electrocatalytic performance of traditional carbon felt, and considering the availability of raw materials, this invention utilizes biomass waste such as wood, bamboo, and bamboo shoot shells to design a high-performance biochar catalyst with O and N ortho-position co-doping. Acid pretreatment alters the chemical composition of the cell wall, removing a large amount of hemicellulose and some lignin, thus forming porous biochar with a large specific surface area and introducing numerous oxygen-containing functional groups during carbonization. N doping is then successfully achieved through argon-ammonia plasma treatment. Benefiting from the increase in polar functional groups, this method improves the overall hydrophilicity of the electrode, provides additional active sites, reduces charge transfer resistance, and enhances the electrode's catalytic performance. Compared to the smooth carbon fibers of traditional carbon felt, vanadium ions are more easily adsorbed on the ABSC-N-CF surface, and the redox reaction kinetics are faster at the O and N co-doped active sites. Compared to traditional carbon felt, the electrode obtained in this invention exhibits better performance at a current density of 100 mA / cm². 2 At that time, the energy efficiency increased from 75% to 83%, and remained at 80% after 500 cycles.

[0021] The oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode obtained by this invention only requires one carbonization step and achieves nitrogen doping with the help of plasma technology. The processing time is short, the experimental energy consumption is low, and the process is simple. Attached Figure Description

[0022] Figure 1 The cyclic voltammetry curves of the electrode materials obtained in Comparative Examples 1, 2, and 3 are shown.

[0023] Figure 2 The cyclic voltammetry curves of the electrode materials obtained in Examples 1, 4, 5, 6, and 7 are shown.

[0024] Figure 3 The cyclic voltammetry curves are for the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrodes obtained in Examples 1, 2, and 3.

[0025] Figure 4 The cyclic voltammetry curves are for the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrodes obtained in Examples 1, 4, and 5.

[0026] Figure 5 The cyclic voltammetry curves are for the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrodes obtained in Examples 1, 6, and 7.

[0027] Figure 6 The cyclic voltammetry curves are for the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrodes obtained in Examples 1, 8, and 9.

[0028] Figure 7 The image shows an electron microscope (EM) image of the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode obtained in Example 1.

[0029] Figure 8 The graph shows the battery cycle performance of the carbon felt electrodes obtained in Example 1 and Comparative Example 7. Detailed Implementation

[0030] To facilitate a better understanding of this invention, the invention will be described more comprehensively and in detail below with reference to the accompanying drawings and preferred embodiments. However, the scope of protection of this invention is not limited to the specific embodiments described below. It should be noted that reagents or instruments used without a specified manufacturer are considered to be conventional products that can be purchased commercially.

[0031] Comparative Example 1 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 700℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5 cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed, resulting in an oxygen-rich bamboo shoot shell carbon-coated carbon felt electrode material.

[0032] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 1 As shown.

[0033] Comparative Example 2 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of this oxygen-enriched carbon was ground into powder and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was then cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed, resulting in an oxygen-rich bamboo shoot shell carbon-coated carbon felt electrode material.

[0034] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 1 As shown.

[0035] Comparative Example 3 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 900℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of this oxygen-enriched carbon was ground into powder and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was then cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed, resulting in an oxygen-rich bamboo shoot shell carbon-coated carbon felt electrode material.

[0036] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 1 As shown.

[0037] Figure 1 The cyclic voltammetry curves of the electrode materials obtained in Comparative Examples 1, 2, and 3 show that the oxygen-enriched carbon-modified electrode obtained by carbonizing the bamboo shoot shell at 800℃ has the largest peak current and a smaller peak potential difference, indicating that it has the best electrochemical performance. This demonstrates that 800℃ is the optimal carbonization temperature.

[0038] Comparative Example 4 Weigh 1g of bamboo shoot shells and wash them with deionized water until neutral. Dry them in a 60℃ oven, then carbonize them in a tube furnace at 800℃ for 2 hours under a N2 atmosphere to obtain bamboo shoot shell charcoal. The heating rate is 5℃ / min. Weigh 30mg of bamboo shoot shell charcoal, grind it into powder, and add it to 15mL of DMF solution. Sonicate for 6 hours to obtain uniform ink. Cut the original carbon felt into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed, resulting in carbon felt electrode material coated with bamboo shoot shell carbon.

[0039] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 2 As shown.

[0040] Comparative Example 5 Weigh 1g of bamboo shoot shells and wash them with deionized water until neutral. Dry them in a 60℃ oven, then carbonize them in a tube furnace at 800℃ for 2 hours under a N2 atmosphere to obtain bamboo shoot shell charcoal. The heating rate is 5℃ / min. Weigh 30mg of bamboo shoot shell charcoal, grind it into powder, and add it to 15mL of DMF solution. Sonicate for 6 hours to obtain uniform ink. Cut the original carbon felt into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain carbon felt electrode material coated with bamboo shoot shell carbon. The oxygen-rich bamboo shoot shell carbon-coated carbon felt is then treated for 30 seconds using an Ar / NH3 plasma source (gas flow rate ratio 2:1) with a power of 200W to obtain nitrogen-doped biomass carbon-modified carbon felt electrode material.

[0041] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 2 As shown.

[0042] Comparative Example 6 An Ar / NH3 plasma source (gas flow rate ratio 2:1) was used to ionize a 3×4.5 cm plasma. 2 The original carbon felt was processed for 30 seconds with a plasma source power of 200 W to obtain nitrogen-doped modified carbon felt electrode material.

[0043] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 2 As shown.

[0044] Comparative Example 7 Using 3×4.5 cm 2 A standard carbon felt electrode was used as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode to construct a three-electrode unit system for an all-vanadium redox flow battery. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry was performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 2 As shown.

[0045] Figure 2The cyclic voltammetry curves of the electrode materials obtained in Examples 1, 4, 5, 6, and 7 show that the cyclic voltammetry curve of Example 1 has the largest peak current and the smallest peak potential difference, indicating that the carbon felt modified with the oxygen-nitrogen co-doped shell carbon catalyst has the best electrochemical performance, which is significantly better than the original shell carbon modified carbon felt, the shell carbon modified carbon felt with only N doping, and the carbon felt modified only by plasma treatment.

[0046] Example 1 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 30 s using Ar / NH3 (gas flow rate ratio 2:1) as a plasma source with a power of 200 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0047] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 3 As shown. Electron micrograph of the electrode prepared in Example 1 is shown below. Figure 7 As shown, biomass carbon is relatively uniformly distributed on the surface of the carbon fiber, which helps to increase the defects in the electrode and enhance its electrocatalytic activity.

[0048] Using the modified electrode material prepared in this example as the positive electrode, Nafion 212 as the separator, and 1.5 mol / L VOSO4 and 3.0 mol / L H2SO4 as the electrolyte, a vanadium redox flow battery was assembled, operating at 100 mA / cm². 2 The battery was charged and discharged under current density. As a comparison, Comparative Example 7 underwent battery charge and discharge performance testing under the same conditions. The results are as follows: Figure 8 As shown.

[0049] The battery based on this embodiment retains 80% of its energy efficiency after 500 cycles without significant degradation. However, the control battery showed significant performance degradation after 200 cycles due to polarization issues. This may be attributed to the O, N co-doped biomass carbon catalyst providing additional active sites that accelerate charge transfer, and the plasma treatment increasing the hydrophilicity of the electrodes. This helps reduce electrochemical polarization and ohmic polarization between the electrolyte and the electrode surface during battery operation.

[0050] Example 2 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 20 s using Ar / NH3 (gas flow rate ratio 2:1) as a plasma source with a power of 200 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0051] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 3 As shown.

[0052] Example 3 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 40 s using Ar / NH3 (gas flow rate ratio 2:1) as a plasma source with a power of 200 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0053] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 3 As shown.

[0054] Figure 3 The cyclic voltammetry curves of the electrode materials obtained in Examples 1, 2, and 3 show that the cyclic voltammetry curve of Example 1 is the most stable, indicating that the oxygen-nitrogen co-doped biomass carbon catalyst modified carbon felt obtained in Example 1 has the best electrochemical performance, and that the optimal plasma treatment time is 30s.

[0055] Example 4 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 30 s using Ar / NH3 (gas flow rate ratio 2:1) as a plasma source with a power of 150 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0056] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry was performed on the three-electrode system with a scan rate set to 10 mV / s. The cyclic voltammetry curves are shown below. Figure 4 As shown.

[0057] Example 5 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 30 s using Ar / NH3 (gas flow rate ratio 2:1) as a plasma source with a power of 250 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0058] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 4 As shown.

[0059] Figure 4 The cyclic voltammetry curves of the electrode materials obtained in Examples 1, 4, and 5 show that the cyclic voltammetry curve of Example 1 is the most stable, indicating that the oxygen-nitrogen co-doped biomass carbon catalyst modified carbon felt obtained in Example 1 has the best electrochemical performance, and that the optimal power condition for plasma treatment is 200 W.

[0060] Example 6 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated with Ar as a plasma source for 30 s, and the power of the plasma source is 200 W, to obtain oxygen and nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0061] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 5 As shown.

[0062] Example 7 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is then treated with NH3 as a plasma source for 30 seconds at a power of 200 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0063] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 5 As shown.

[0064] Figure 5 The cyclic voltammetry curves of the electrode materials obtained in Examples 1, 6, and 7 show that the cyclic voltammetry curve of Example 1 is the most stable and has the lowest redox peak potential, indicating that the oxygen-nitrogen co-doped biomass carbon catalyst modified carbon felt obtained in Example 1 has the best electrochemical performance, indicating that the plasma source is preferably an Ar / NH3 mixed gas.

[0065] Example 8 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 30 s using Ar / NH3 (gas flow rate ratio 1:1) as a plasma source with a power of 200 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0066] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry tests were performed on the three-electrode system at a scan rate of 10 mV / s. The cyclic voltammetry curves are shown below. Figure 6 As shown.

[0067] Example 9 1g of bamboo shoot shell was weighed and placed in 100mL of 10% HNO3 solution. The mixture was then placed in a shaker at 150 rpm for 12 hours. After washing the shell with deionized water until neutral, it was dried in a 60℃ oven. Subsequently, it was carbonized in a tube furnace at 800℃ under a N2 atmosphere for 2 hours to obtain oxygen-enriched bamboo shoot shell carbon, with a heating rate of 5℃ / min. 30mg of the oxygen-enriched bamboo shoot shell carbon was weighed, ground into powder, and added to 15mL of DMF solution. The mixture was sonicated for 6 hours to obtain a uniform ink. The original carbon felt was cut into 3×4.5cm pieces. 2 After soaking and drying, this process is repeated three times until the ink is completely absorbed to obtain oxygen-enriched bamboo shoot shell carbon-coated carbon felt. The oxygen-enriched bamboo shoot shell carbon-coated carbon felt is treated for 30 s using Ar / NH3 (gas flow rate ratio 1:2) as a plasma source with a power of 200 W to obtain oxygen-nitrogen co-doped biomass carbon modified carbon felt electrode material.

[0068] Using the electrode material prepared in this example as the working electrode, a platinum electrode as the counter electrode, and an Hg / HgSO4 electrode as the reference electrode, a three-electrode unit system for an all-vanadium redox flow battery was constructed. The electrolyte consisted of 0.1 mol / L VOSO4 and 2.0 mol / L H2SO4. Cyclic voltammetry was performed on the three-electrode system with a scan rate set to 10 mV / s. The cyclic voltammetry curves are shown below. Figure 6As shown.

[0069] Figure 6 The cyclic voltammetry curves of the electrode materials obtained in Examples 1, 8, and 9 show that the cyclic voltammetry curve of Example 1 is the most stable and has the smallest peak potential difference, indicating that the oxygen-nitrogen co-doped biomass carbon catalyst modified carbon felt obtained in Example 1 has the best electrochemical performance, and that the optimal gas flow rate ratio of the Ar / NH3 mixed plasma source is 2:1.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode, characterized in that, Includes the following steps: (S1) Cut the bamboo shoot shells into slices and put them into a dilute nitric acid solution. Place them in a shaker and shake. Then wash them with deionized water until neutral and dry them in an oven. (S2) The acid-pretreated bamboo shoot shells are heated under a nitrogen atmosphere to obtain oxygen-enriched bamboo shoot shell carbon; (S3) Grind bamboo shoot shell carbon into powder, use N,N-dimethylformamide as solvent to prepare ink, soak the original carbon felt in ink, and put it in an oven to dry, repeating several times until the ink is completely absorbed. (S4) The surface of oxygen-rich bamboo shoot shell carbon-coated carbon felt was subjected to plasma treatment using a plasma source to obtain a nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode. Step (S1): The shaking speed is 100-250 rpm, and the shaking time is 8-15 h; The heating temperature in step (S2) is 700-900℃, and the heating time is 1-3 hours; In step (S4), the plasma source is one of the following: a single argon plasma source, a single ammonia plasma source, or a mixed argon and ammonia plasma source; the power of the plasma source is 150-250 W; and the plasma treatment time is 20-40 s.

2. The method for preparing the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode according to claim 1, characterized in that, The volume concentration of the dilute nitric acid solution in step (S1) is 5%-20%.

3. The method for preparing the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode according to claim 1, characterized in that, In step (S3), the mass-volume ratio of bamboo shoot shell carbon powder to solvent is 1-3 g / L.

4. The method for preparing the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode according to claim 1, characterized in that, In steps (S1) and (S3), the temperature of the oven is 60-80℃.

5. The nitrogen-oxygen co-doped biomass carbon catalyst modified carbon felt electrode prepared by the preparation method according to any one of claims 1-4.

6. The application of the nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode according to claim 5, characterized in that, A three-electrode unit system for an all-vanadium redox flow battery was constructed using a nitrogen-oxygen co-doped biomass carbon catalyst-modified carbon felt electrode as the working electrode, a platinum electrode as the counter electrode, and an Hg / Hg2SO4 electrode as the reference electrode. The electrochemical performance of the battery was then tested.

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