Preparation method of natural nitrogen and oxygen co-doped porous carbon modified electrode material

Abstract

The invention discloses a preparation method of a natural nitrogen and oxygen co-doped porous carbon modified electrode material, and the preparation method comprises the following steps: S1, dissolving peach gum powder into an aerobic acid solution, stirring to remove impurities in peach gum, and then washing the residual peach gum powder with deionized water; s2, dispersing the acid-washed peach gum powder in an organic alkali solution, stirring at room temperature, washing residual solids with deionized water, and performing vacuum drying to obtain peach gum powder rich in hydroxyl and nitrogen elements; s3, dispersing the peach gum powder rich in hydroxyl and nitrogen in deionized water to obtain a peach gum water dispersion liquid, placing the carbon felt in the peach gum water dispersion liquid, magnetically stirring to enable the surface of the carbon felt to adsorb enough peach gum molecules, and drying the peach gum-loaded carbon felt in a vacuum drying oven; and S4, taking two parts of dried peach gum molecules, carrying out carbonization treatment, and respectively obtaining the nitrogen and oxygen co-doped porous carbon electrode containing pyridine nitrogen or graphite nitrogen by adjusting the carbonization time and temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid flow batteries, and particularly relates to a preparation method of a natural nitrogen and oxygen co-doped porous carbon modified electrode material. BACKGROUND

[0002] The electrode material is a key factor determining the cost and performance of the liquid flow battery, and an ideal electrode material should have high electrical conductivity, good catalytic activity, excellent electrochemical stability, low cost, easy processing and environmental friendliness and the like. Although carbon-based materials are widely used in the electrode of the liquid flow battery due to their excellent chemical stability, the low specific surface area and limited catalytic activity of the carbon-based materials make it difficult for the liquid flow battery to achieve commercial-scale application. Although certain progress has been made in the research on the electrode material of the liquid flow battery in the prior art, the performance of certain electrode materials is improved, but problems such as high cost, insufficient comprehensive performance, complex preparation process and limited application range still exist. The carbon felt, as a commonly used electrode material of the liquid flow battery, has excellent electrochemical stability, but the surface catalytic activity and the specific surface area of the carbon felt are low, which seriously hinders the catalysis of the active substance. Therefore, the modification of the carbon felt is a key to improving the electrochemical performance of the liquid flow battery.

[0003] The main reason for the low specific electrochemical activity of the carbon felt is that the surface of the carbon felt has few oxygen-containing functional groups, resulting in poor hydrophilicity. The poor hydrophilicity leads to high interfacial resistance at the electrode-electrolyte interface, thereby having high electrochemical polarization, so that the catalytic conversion of the active substance has a high energy barrier. In addition, the low porosity is not conducive to the flow of the electrolyte, thereby reducing the active sites on the electrode surface. The commonly used modification method is to introduce heteroatoms or increase the porosity of the carbon-based electrode surface to enhance the catalytic activity of the electrode, but the introduction of the heteroatoms cannot avoid the accumulation and agglomeration between atoms, which seriously affects the inherent electrical conductivity of the carbon felt, and the introduction of the porous structure reduces the mechanical properties of the carbon felt, which is not conducive to the electrochemical performance of the electrode. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a natural nitrogen and oxygen co-doped porous carbon modified electrode material, so as to solve the problem of poor electrochemical activity of the graphite felt when used in the liquid flow battery.

[0005] The technical solution adopted by the present application is a preparation method of a natural nitrogen and oxygen co-doped porous carbon modified electrode material, and the preparation steps are as follows: S1, dissolving peach gum powder into an oxygen-containing acidic solution, stirring to remove impurities in the peach gum, and then washing the residual peach gum powder with deionized water; S2, dispersing the acid-washed peach gum powder in an organic alkali solution, stirring at room temperature, washing the residual solid with deionized water, and vacuum drying to obtain a peach gum powder rich in hydroxyl and nitrogen elements. S3, disperse the peach kernel gum powder rich in hydroxyl and nitrogen elements in deionized water to obtain a peach kernel gum water dispersion, place the carbon felt in the peach kernel gum water dispersion, and magnetically stir to adsorb a sufficient amount of peach kernel gum molecules on the surface of the carbon felt, and then dry the peach kernel gum-loaded carbon felt in a vacuum drying oven; S4, take two portions of the dried peach kernel gum molecules, place them in a tube furnace for carbonization treatment, and by adjusting the carbonization time and temperature, obtain a nitrogen and oxygen co-doped porous carbon electrode containing pyridine nitrogen and a nitrogen and oxygen co-doped microporous carbon electrode containing graphite nitrogen, respectively.

[0006] Further, in S1, the mass-to-volume ratio of the peach kernel gum powder and the acidic solution is 1:(10-30) g / mL, and the pH of the aerobic acidic solution is 4-6. The stirring conditions are: temperature 50-60 DEG C, speed 400-1200 r / min, and time 12-48 h. After washing with deionized water, the pH of the residual peach kernel gum powder is 6-7.

[0007] Further, in S2, the mass-to-volume ratio of the acid-washed peach kernel gum powder and the organic alkali solution is 1:(2-10) g / mL, the stirring time is 6-8 h, the pH of the residual solid after washing with deionized water is 7-8, the temperature for vacuum drying is 40-60 DEG C, and the time is 8-12 h. Further, in S3, the magnetic stirring time is 12-18 h, and the loading mass ratio of the peach kernel gum molecules on the carbon felt is (0.1-0.15):1 g / g.

[0008] Further, in S4, the carbonization time of the nitrogen and oxygen co-doped porous carbon electrode containing pyridine nitrogen is 3-6 h at a temperature of 400-600 DEG C. The carbonization time of the nitrogen and oxygen co-doped microporous carbon electrode containing graphite nitrogen is 6-8 h at a temperature of 800-1000 DEG C.

[0009] Further, the aerobic acidic solution is one of dilute sulfuric acid, dilute nitric acid, and dilute phosphoric acid.

[0010] Further, the organic alkali solution is one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.

[0011] The beneficial effects of the present application are: 1. The present application uses a one-step carbonization method to prepare a nitrogen and oxygen co-doped porous carbon material, which does not require the use of additional nitrogen and oxygen sources compared to traditional nitrogen and oxygen atom modified electrodes, effectively ensuring the uniform arrangement of nitrogen and oxygen heteroatoms inside the peach kernel gum molecules, maximizing the problem of heteroatom stacking or agglomeration, and effectively enhancing the catalytic performance of the flow battery electrode.

[0012] 2. This invention achieves a uniform porous carbon structure on the surface of the carbon felt electrode, effectively avoiding the problem of uneven pore size caused by traditional pore-forming methods.

[0013] 3. This invention enables the regulation of the content of pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen, and introduces different nitrogen-containing structures for specific flow battery systems, avoiding the problem of uncontrollable functional group types caused by traditional nitrogen doping.

[0014] 4. The composite electrode of the present invention has good conductivity, stable ion transport channels and chemical stability, and exhibits high capacity retention, low polarization and longer cycle life in flow batteries.

[0015] 5. This invention is low in cost and environmentally friendly, and is applicable to a variety of flow battery systems. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is the thermogravimetric curve of the peach gum molecules after alkali treatment modification in Example 1 of the present invention.

[0018] Figure 2 These are SEM images of the pyridine nitrogen-gum modified electrode of the present invention, wherein (a) is the original carbon felt electrode and (b) is the SEM image of the pyridine nitrogen-gum modified electrode.

[0019] Figure 3 These are EDS images of the pyridine nitrogen-gum modified electrode of the present invention, where (a) is the N element distribution, (b) is the O element distribution, and (c) is the C element distribution.

[0020] Figure 4 This is a TEM image of the pyridine nitrogen-gum modified electrode of the present invention.

[0021] Figure 5 These are the electrochemical performance test results of the pyridine nitrogen-gum modified electrode for vanadium anodes and cathodes, where (a) is the CV curve of the vanadium anode of the pyridine nitrogen-gum modified electrode, and (b) is the CV curve of the vanadium cathode of the pyridine nitrogen-gum modified electrode.

[0022] Figure 6 This is the thermogravimetric curve of the alkali-treated modified peach gum molecules in Example 3 of the present invention.

[0023] Figure 7This is the thermogravimetric curve of the alkali-treated modified gum molecules in Example 2 of the present invention.

[0024] Figure 8 These are SEM images of the graphite nitrogen-gum modified electrode of the present invention, wherein (a) is the SEM of the original gum electrode and (b) is the SEM of the graphite nitrogen-gum modified electrode.

[0025] Figure 9 This is a TEM image of the graphite nitrogen-gum modified electrode of this invention.

[0026] Figure 10 This is an XPS image of the graphite nitrogen-gum electrode carbonized at 900°C in this invention.

[0027] Figure 11 This is the CV curve of the vanadium cathode of the graphite nitrogen-modified gum electrode of this invention.

[0028] Figure 12 This invention describes the cycle performance of the graphite nitrogen-gum modified electrode in a zinc-iron flow battery.

[0029] Figure 13 This invention describes the rate performance of the graphite nitrogen-gum modified electrode in a zinc-iron flow battery.

[0030] Figure 14 This invention relates to the power density of the graphite nitrogen-gum modified electrode in a zinc-iron flow battery. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a method for preparing a porous carbon-modified electrode material co-doped with natural nitrogen and oxygen. The specific preparation steps are as follows: S1, dissolve peach gum powder in an aerobic acidic solution, with a mass-to-volume ratio of peach gum powder to acidic solution of 1:(10~30)g / mL, and the pH of the aerobic acidic solution is 4~6. Stir at 400~1200 r / min for 12~48h at 50~60℃ to remove impurities from the peach gum. Then wash the remaining peach gum powder with deionized water until the pH is 6~7. The aerobic acidic solution is one of dilute sulfuric acid, dilute nitric acid, or dilute phosphoric acid.

[0033] S2, the acid-washed gum powder is dispersed in an organic alkaline solution at a mass-to-volume ratio of 1:(2~10) g / mL, stirred at room temperature for 6~8 hours, then washed with deionized water to a pH of 7~8, and dried in a vacuum drying oven at 40~60℃ for 8~12 hours to obtain gum powder rich in hydroxyl groups and nitrogen. The organic alkaline solution is one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, or tetrabutylammonium hydroxide.

[0034] S3. Disperse peach gum powder rich in hydroxyl and nitrogen elements in deionized water to obtain a peach gum aqueous dispersion. Place carbon felt in the peach gum aqueous dispersion and stir magnetically for 12-18 hours to allow sufficient peach gum molecules to be adsorbed on the surface of the carbon felt. The mass ratio of peach gum molecules loaded on the carbon felt is (0.1-0.15):1 g / g. Dry the carbon felt loaded with peach gum in a vacuum drying oven to avoid oxidation of peach gum molecules.

[0035] S4. Take two portions of dried gum molecule and place them in a tube furnace for carbonization. One portion is carbonized for 3-6 hours at a temperature of 400-600℃ to obtain a nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen. The other portion is carbonized for 6-8 hours at a temperature of 800-1000℃ to obtain a nitrogen-oxygen co-doped microporous carbon electrode containing graphitic nitrogen.

[0036] Based on the unique properties of peach gum, this invention constructs a peach gum-modified electrode that not only introduces natural hydroxyl and nitrogen-containing groups but also fully leverages the unique advantages of peach gum. By controlling different carbonization times, different types of nitrogen-containing groups can be obtained, exhibiting excellent catalytic effects on active substances with varying properties. Simultaneously, the microporous structure promotes electrolyte flow, reduces electrode-electrolyte interface resistance, facilitates rapid electron transport, enhances battery reaction kinetics, extends battery cycle life, and significantly improves overall battery performance.

[0037] Example 1 S1, Dissolve 1g of peach gum powder in a dilute sulfuric acid solution with pH=5. The mass-to-volume ratio of peach gum powder to acidic solution is 1:20g / mL. Stir at 800 ran / min for 30 h at 55℃. Then wash the residual peach gum powder with deionized water until pH=6.5. S2, the acid-washed gum powder was dispersed in a tetramethylammonium hydroxide solution at a mass-to-volume ratio of 1:5 g / mL, stirred at room temperature for 7 h, and then the residual solid was washed with deionized water until pH=7.5. The powder was then dried in a vacuum drying oven at 50℃ for 10 h to obtain gum powder rich in hydroxyl groups and nitrogen.

[0038] S3. Peach gum powder rich in hydroxyl and nitrogen elements is dispersed in 20 ml of deionized water to obtain a peach gum aqueous dispersion. Carbon felt is placed in the peach gum aqueous dispersion and magnetically stirred for 15 h to allow sufficient peach gum molecules to be adsorbed on the surface of the carbon felt. The mass ratio of peach gum molecules loaded on the carbon felt is 0.13:1 g / g. Then, the carbon felt loaded with peach gum is dried in a vacuum drying oven.

[0039] S4. The dried carbon felt loaded with peach gum was divided into two parts and placed in a tube furnace for carbonization. One part was carbonized for 4 hours at a temperature of 500℃ to obtain a nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen. The other part was carbonized for 7 hours at a temperature of 900℃ to obtain a nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen.

[0040] Thermogravimetric analysis (TGA) results of the alkali-treated modified gum molecules in this embodiment are shown below. Figure 1 As shown, the number of oxygen-containing functional groups and nitrogen-containing groups on the surface of the unsaturated olefin (C=C) structure in the gum molecule is significantly increased.

[0041] The nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen obtained in this embodiment was used as the positive electrode, and the nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen was used as the negative electrode. They were assembled into a vanadium redox flow battery for electrochemical testing. The assembled vanadium redox flow battery had an energy efficiency of 85%, which is higher than the 82% of the traditional original electrode, showing excellent electrochemical performance.

[0042] In zinc-iron flow batteries, since both zinc deposition and the catalytic conversion of potassium ferricyanide require electrode materials with high conductivity, both the positive and negative electrodes are selected as nitrogen- and oxygen-co-doped microporous carbon electrodes containing graphite nitrogen. The assembled zinc-iron flow battery has an energy efficiency of 90%, which is higher than the original electrode's 87%. This is due to the high conductivity of the graphite nitrogen electrode, which makes it easy for zinc to be deposited uniformly, thereby reducing the formation of zinc dendrites.

[0043] Example 2 S1, dissolve 1g of peach gum powder in a dilute sulfuric acid solution with pH=4, the mass-to-volume ratio of peach gum powder to acidic solution is 1:10 g / mL, stir at 400r / min for 12 h at 50℃, and then wash the remaining peach gum powder with deionized water until pH=6.

[0044] S2, the acid-washed gum powder was dispersed in a tetramethylammonium hydroxide solution at a mass-to-volume ratio of 1:2 g / mL, stirred at room temperature for 6 hours, and then the residual solid was washed with deionized water until pH=7. The powder was then dried in a vacuum drying oven at 40℃ for 8 hours to obtain gum powder rich in hydroxyl groups and nitrogen.

[0045] S3. Peach gum powder rich in hydroxyl and nitrogen elements is dispersed in 20 ml of deionized water to obtain a peach gum aqueous dispersion. Carbon felt is placed in the peach gum aqueous dispersion and magnetically stirred for 12 h to allow sufficient peach gum molecules to be adsorbed on the surface of the carbon felt. The mass ratio of peach gum molecules loaded on the carbon felt is 0.1:1 g / g. Then, the carbon felt loaded with peach gum is dried in a vacuum drying oven.

[0046] S4. Take two portions of dried gum molecules and place them in a tube furnace for carbonization. One portion is carbonized for 3 hours at a temperature of 400°C to obtain a nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen. The other portion is carbonized for 6 hours at a temperature of 800°C to obtain a nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen.

[0047] Thermogravimetric analysis (TGA) results of the alkali-treated modified gum molecules in this embodiment are shown below. Figure 7 As shown, the increase in oxygen-containing functional groups and nitrogen-containing groups on the surface of the unsaturated olefin (C=C) structure in the gum molecule, but due to the decrease in alkali concentration, the introduction of oxygen-containing and nitrogen-containing groups on the surface is not significant, and the thermogravimetric curve is not much different from the original.

[0048] The morphology of the nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen obtained in this embodiment is as follows: Figure 2 As shown, (a) is the original carbon felt electrode, and (b) is the SEM image of the pyridine nitrogen-gum modified electrode. Compared with the original electrode, the gum modified electrode has more carbon layers on its surface. The EDS image of the pyridine nitrogen-gum modified electrode is shown below. Figure 3 As shown, (a) is the distribution of N elements, (b) is the distribution of O elements, and (c) is the distribution of C elements. The elemental distribution of nitrogen-oxygen co-doping can be seen. The TEM image of the pyridine nitrogen-gum modified electrode is shown below. Figure 4 As shown, the surface has a low degree of graphitization, which is due to the low carbonization temperature and the fact that the nitrogen-containing groups on the surface are mainly composed of pyridine nitrogen.

[0049] The nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen obtained in this embodiment was used as the positive electrode, and the nitrogen-oxygen co-doped microporous carbon electrode containing graphitic nitrogen was used as the negative electrode. Electrochemical tests were performed, and the results are as follows: Figure 5 As shown in the figure, (a) is the CV curve of the vanadium anode of the pyridine nitrogen-gum modified electrode, and (b) is the CV curve of the vanadium cathode of the pyridine nitrogen-gum modified electrode. It can be seen from the figure that the nitrogen and oxygen co-doped porous carbon electrode of pyridine nitrogen has a smaller voltage difference on the vanadium anode side, indicating that it has higher reaction kinetics and catalytic activity for vanadium anode ions.

[0050] In zinc-iron flow batteries, both the positive and negative electrodes are nitrogen- and oxygen-co-doped microporous carbon electrodes containing graphite nitrogen. The battery has an energy efficiency of 89% and excellent conductivity.

[0051] Example 3 S1, Dissolve 1g of peach gum powder in a dilute sulfuric acid solution with pH=6. The mass-volume ratio of peach gum powder to acidic solution is 1:30g / mL. Stir at 1200 ran / min for 48 h at 60℃. Then wash the residual peach gum powder with deionized water until pH=7. S2, the acid-washed gum powder was dispersed in a tetramethylammonium hydroxide solution at a mass-to-volume ratio of 1:10 g / mL, stirred at room temperature for 8 hours, and then the residual solid was washed with deionized water until pH=8. The powder was then dried in a vacuum drying oven at 60℃ for 12 hours to obtain gum powder rich in hydroxyl groups and nitrogen.

[0052] S3. Peach gum powder rich in hydroxyl and nitrogen elements is dispersed in 20 ml of deionized water to obtain a peach gum aqueous dispersion. Carbon felt is placed in the peach gum aqueous dispersion and magnetically stirred for 8 hours to allow sufficient peach gum molecules to be adsorbed on the surface of the carbon felt. The mass ratio of peach gum molecules loaded on the carbon felt is 0.15:1 g / g. Then, the carbon felt loaded with peach gum is dried in a vacuum drying oven.

[0053] S4. The dried carbon felt loaded with peach gum was divided into two parts and placed in a tube furnace for carbonization. One part was carbonized for 6 hours at 600°C to obtain a nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen. The other part was carbonized for 8 hours at 1000°C to obtain a nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen.

[0054] The thermogravimetric test diagram of this embodiment is as follows: Figure 6 As shown, the increase in oxygen-containing functional groups and nitrogen-containing groups on the surface of the unsaturated olefin (C=C) structure in the gum molecule, however, leads to the destruction of the gum molecule structure due to the increase in alkali concentration, resulting in a decrease in mechanical properties, which is not conducive to the application of flow batteries.

[0055] The nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen obtained in this embodiment was used as the positive electrode, and the nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen was used as the negative electrode. They were assembled into a vanadium redox flow battery for testing. Due to the high concentration of alkali, the molecular structure of gum arabic was destroyed, and the energy efficiency of the assembled vanadium redox flow battery was 83%, which was lower than the original electrode's 82%.

[0056] In the zinc-iron flow battery, both the positive and negative electrodes are nitrogen- and oxygen-co-doped microporous carbon electrodes containing graphite nitrogen. Due to the high concentration of alkali, the molecular structure of gum arabic is destroyed, and the energy efficiency of the assembled zinc-iron flow battery is 88%, which is lower than the original electrode's 87%.

[0057] Example 4 The difference from Example 1 is that in S4, the carbonization temperature of the nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen is 850°C.

[0058] Everything else is the same as in Example 1.

[0059] In this embodiment, the specific morphology of the nitrogen-oxygen co-doped porous carbon electrode containing graphitic nitrogen is as follows: Figure 8 As shown, (a) is the SEM image of the original gum electrode, and (b) is the SEM image of the graphite nitrogen-gum modified electrode. Compared with the original electrode, the gum modified electrode has more carbon layers on its surface. The transmission electron microscopy image is shown below. Figure 9 As shown, the surface exhibits a high degree of graphitization, which is due to the high carbonization temperature. The nitrogen-containing groups on the surface are predominantly composed of graphitic nitrogen, and XPS analysis confirms that the carbonization temperature plays a decisive role in the formation of graphitic nitrogen. Figure 10 As shown, more graphitic nitrogen was formed. The prepared graphitic nitrogen-doped nitrogen-oxygen co-doped electrode was applied in an all-vanadium redox flow battery. Due to the high conductivity of graphitic nitrogen, it can accelerate the reaction kinetics of the vanadium battery anode and improve the catalytic conversion of anode ions, such as... Figure 11 As shown.

[0060] Example 5 The difference from Example 1 is that in S4, the carbonization temperature of the nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen is 1000°C.

[0061] Everything else is the same as in Example 1.

[0062] In this embodiment, due to the increased carbonization temperature, the resulting nitrogen-oxygen co-doped porous carbon electrode containing graphitic nitrogen has a more stable graphitic nitrogen structure.

[0063] Example 6 The difference from Example 1 is that in S4, the carbonization temperature of the nitrogen-oxygen co-doped microporous carbon electrode containing graphite nitrogen is 900°C and the carbonization time is 8h.

[0064] Everything else is the same as in Example 1.

[0065] The electrode material obtained in this embodiment was assembled into a zinc-iron flow battery for testing, and the results are as follows: Figures 12-14 As shown, compared to the original electrode, this embodiment exhibits better cycle life, rate performance, and power density. The energy efficiency of this embodiment is 90%, higher than the original electrode's 87%, at 350 mA / cm². 2 It can still operate stably at current densities of up to 350 mA / cm². The original electrode, due to its low conductivity, only operates at this current density. 2 Uniform zinc deposition is impossible at the current density, resulting in highly unstable charge-discharge curves, and the power density is 130 mV / cm higher than that of the original electrode. 2 These battery data all demonstrate the superiority of nitrogen- and oxygen-co-doped microporous carbon electrodes made of graphite nitrogen.

[0066] Example 7 The difference from Example 1 is that in S1, the acidic solution is replaced with dilute nitric acid, and the mass-to-volume ratio of gum powder to dilute nitric acid solution is 1:17 g / mL. Everything else is the same as in Example 1.

[0067] The positive and negative electrode materials obtained in this embodiment were assembled into a vanadium redox flow battery for testing. The energy efficiency was 85%, which is higher than the original electrode's 82%, indicating that dilute nitric acid can also achieve the effect of cleaning the surface of gum arabic.

[0068] Example 8 The difference from Example 1 is that in S1, the acidic solution is replaced with dilute phosphoric acid, and the mass-to-volume ratio of gum powder to dilute phosphoric acid solution is 1:25 g / mL.

[0069] Everything else is the same as in Example 1.

[0070] The positive and negative electrode materials obtained in this embodiment were assembled into a vanadium redox flow battery for testing. The energy efficiency was 86%, which is higher than the original electrode's 82%, indicating that dilute phosphoric acid can also achieve the effect of cleaning the surface of gum arabic.

[0071] Example 9 The difference from Example 1 is that in S2, the organic base solution is replaced with tetraethylammonium hydroxide, and the mass-to-volume ratio of gum powder and tetraethylammonium hydroxide solution is 1:4 g / mL.

[0072] Everything else is the same as in Example 1.

[0073] The positive and negative electrode materials obtained in this embodiment were assembled into a vanadium redox flow battery for testing. The energy efficiency was 85%, which is higher than the original electrode's 82%, indicating that tetraethylammonium hydroxide can also introduce nitrogen- and oxygen-containing groups into the gum precursor.

[0074] Example 10 The difference from Example 1 is that in S2, the organic base solution is replaced with tetrabutylammonium hydroxide, and the mass-volume ratio of gum powder to tetrabutylammonium hydroxide solution is 1:4 g / mL.

[0075] Everything else is the same as in Example 1.

[0076] The electrode material obtained in this embodiment was assembled into a zinc-iron flow battery for testing. The energy efficiency was 88%, which is higher than the original electrode's 87%, indicating that tetrabutylammonium hydroxide can also introduce nitrogen- and oxygen-containing groups into the gum precursor.

[0077] Comparative Example 1 The difference from Example 1 is that in S4, the carbonization time of the nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen is 7h and the temperature is 700℃.

[0078] Everything else is the same as in Example 1.

[0079] The positive and negative electrode materials obtained in this comparative example were assembled into a vanadium redox flow battery for testing. The energy efficiency was 79%, lower than the original electrode's 82%, indicating that the pyrrole nitrogen-modified electrode has no catalytic performance in the vanadium redox battery. In this comparative example, due to the excessively high temperature, nitrogen-containing groups easily transformed into pyrrole nitrogen. When assembled into a vanadium redox flow battery, the pyrrole nitrogen-modified electrode exhibited lower catalytic effect on vanadium because its adsorption capacity is lower than that of pyridine nitrogen and its conductivity is lower than that of graphite nitrogen.

[0080] Comparative Example 2 The difference from Example 1 is that in S4, the carbonization time of the nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen is 1.5 h and the temperature is 300 °C.

[0081] Everything else is the same as in Example 1.

[0082] The positive and negative electrode materials obtained in this comparative example were assembled into a vanadium redox flow battery for testing. The energy efficiency was 80%, which was lower than the original electrode's 82%. In this comparative example, due to insufficient carbonization time, the carbon felt could not form a pyridine nitrogen structure.

[0083] Comparative Example 3 The difference from Example 1 is that in S1, the mass-to-volume ratio of gum powder and dilute sulfuric acid solution is 1:5 g / mL.

[0084] Everything else is the same as in Example 1.

[0085] The positive and negative electrode materials obtained in this comparative example were assembled into a vanadium redox flow battery for testing. The energy efficiency was 80%, which was lower than the original electrode's 82%, indicating that the amount of dilute sulfuric acid was too low, resulting in impurities on the gum surface not being completely cleaned.

[0086] Comparative Example 4 The difference from Example 1 is that in S2, the alkaline solution is replaced with sodium hydroxide.

[0087] Everything else is the same as in Example 1.

[0088] The positive and negative electrode materials obtained in this comparative example were assembled into a vanadium redox flow battery for testing. The energy efficiency was 80%, which was lower than the original electrode's 82%. This is because the sodium hydroxide solution could not introduce more nitrogen-containing groups into the gum arabic, reducing the formation of pyridine nitrogen, thus resulting in low catalytic activity.

[0089] Comparative Example 5 The difference from Example 1 is that in S3, the loading mass ratio of gum molecules on the carbon felt is 0.08:1 g / g.

[0090] Everything else is the same as in Example 1.

[0091] The positive and negative electrode materials obtained in this comparative example were assembled into a zinc-iron flow battery for testing. The energy efficiency was 87%, which is 87% of that of the original electrode. The reason is that the amount of gum molecules loaded on the electrode surface is too small to achieve a catalytic effect.

[0092] Comparative Example 6 The difference from Example 1 is that in S3, the loading mass ratio of gum molecules on the carbon felt is 0.2:1 g / g.

[0093] Everything else is the same as in Example 1.

[0094] The positive and negative electrode materials obtained in this comparative example were assembled into a zinc-iron flow battery for testing. The energy efficiency was 86%, which was lower than the original electrode's 87%. This was because the gum molecule loading on the electrode surface was too high, forming agglomerates, which reduced the conductivity of the carbon felt electrode and was not conducive to zinc deposition.

[0095] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material, characterized in that, The preparation steps are as follows: S1. Dissolve the peach gum powder in an aerobic acidic solution, stir to remove impurities from the peach gum, and then wash the remaining peach gum powder with deionized water. S2, the acid-washed peach gum powder is dispersed in an organic alkaline solution, stirred at room temperature, and the residual solid is washed with deionized water. After vacuum drying, peach gum powder rich in hydroxyl and nitrogen elements is obtained. S3, disperse the hydroxyl and nitrogen-rich gum powder in deionized water to obtain a gum aqueous dispersion, place the carbon felt in the gum aqueous dispersion, stir magnetically to adsorb sufficient gum molecules on the surface of the carbon felt, and dry the gum-loaded carbon felt in a vacuum drying oven. S4. Take two portions of dried gum molecules and place them in a tube furnace for carbonization. By adjusting the carbonization time and temperature, nitrogen-oxygen co-doped porous carbon electrodes containing pyridine nitrogen and nitrogen-oxygen co-doped microporous carbon electrodes containing graphite nitrogen are obtained respectively.

2. The method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material according to claim 1, characterized in that, In S1, the mass-to-volume ratio of gum powder to acidic solution is 1:(10~30)g / mL, and the pH of the aerobic acidic solution is 4~6; Stirring conditions: temperature 50~60℃, speed 400~1200 r / min, time 12~48 h; The pH of the residual gum powder after washing with deionized water is 6-7.

3. The method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material according to claim 1, characterized in that, In step S2, the acid-washed gum powder and organic alkali solution are mixed at a mass-to-volume ratio of 1:(2~10) g / mL, stirred for 6~8 hours, and the pH of the residual solid after washing with deionized water is 7~8. The vacuum drying temperature is 40~60℃ and the time is 8~12 hours.

4. The method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material according to claim 1, characterized in that, In step S3, the magnetic stirring time is 12-18 hours, and the loading mass ratio of gum molecules on the carbon felt is (0.1-0.15):1 g / g.

5. The method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material according to claim 1, characterized in that, In S4, the carbonization time of the nitrogen-oxygen co-doped porous carbon electrode containing pyridine nitrogen is 3-6 h, and the temperature is 400-600 °C. The carbonization time of the nitrogen-oxygen co-doped microporous carbon electrode containing graphitic nitrogen is 6-8 hours, and the temperature is 800-1000℃.

6. The method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material according to claim 1, characterized in that, The aerobic acidic solution is one of dilute sulfuric acid, dilute nitric acid, or dilute phosphoric acid.

7. The method for preparing a natural nitrogen and oxygen co-doped porous carbon modified electrode material according to claim 1, characterized in that, The organic alkaline solution is one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.

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