A preparation method and application of a composite catalyst for iron-chromium liquid flow battery electrodes

Abstract

The application relates to the technical field of energy materials, and particularly discloses a preparation method and application of a composite catalyst for an iron-chromium liquid flow battery electrode, which takes tea dregs as raw materials, obtains a biochar precursor through a series of treatments, mixes the biochar precursor with sodium tungstate through ultrasonic mixing, adopts a hydrothermal method, and finally obtains the composite catalyst through drying, calcination, washing and other operations. The application takes organic solid waste as the basis, combines the sodium tungstate which can promote the improvement of the battery performance by using the characteristics that the organic solid waste has a developed pore structure after carbonization, and prepares the composite catalyst which can be applied to the iron-chromium liquid flow battery negative electrode carbon cloth. The catalyst is applied to the carbon cloth electrode of the iron-chromium liquid flow battery, can well improve the hydrophilicity and conductivity of the carbon cloth, can improve the capacity retention rate of the carbon cloth, and promotes the improvement of the electrochemical performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy materials, in particular to a preparation method and application of a composite catalyst for an iron-chromium flow battery electrode. BACKGROUND

[0002] Electrochemical energy storage needs a more flexible technical supplement. Lithium ion batteries are the main way of electrochemical energy storage, but there are some technical bottlenecks, such as poor safety and short cycle life, so it is necessary to seek a safer, more reliable and durable energy storage technology to meet the energy storage needs brought by the rapid development of renewable energy.

[0003] Flow batteries have many advantages such as low cost, large scale, strong safety, etc., and are considered as one of the preferred technologies for large-scale energy storage. Iron-chromium flow batteries have many advantages such as green safety, low toxicity and low corrosion, wide operating temperature range, abundant resources of electrolyte raw materials, low price, etc., and are currently developing rapidly, and are expected to become one of the mainstream routes for flow batteries in the future.

[0004] The electrode is a key material for flow batteries, which should have good corrosion resistance, excellent electrochemical activity and stability, etc. Carbon cloth material is flexible and has good electrical conductivity, which has been used in fuel cells and supercapacitors. However, the unmodified carbon cloth has problems such as poor electrical conductivity, poor hydrophilicity and low capacity retention rate. Therefore, a catalyst for iron-chromium flow batteries is needed to improve the performance of the electrode of the battery. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a preparation method and application of a composite catalyst for an iron-chromium flow battery electrode. The tea residue is used as raw material, and after a series of treatments, a biochar precursor is obtained. The biochar precursor is then mixed with sodium tungstate by ultrasonic, and then a hydrothermal method is used. After drying, calcining and washing, a composite catalyst is obtained. The catalyst can improve the hydrophilicity and electrical conductivity of the carbon cloth, and can improve the capacity retention rate of the carbon cloth, promote the improvement of the electrochemical performance of the battery, and solve the problems mentioned in the background art.

[0006] To achieve the above purpose, the present application provides the following technical scheme: a preparation method of a composite catalyst for an iron-chromium flow battery electrode, comprising the following steps:

[0007] S1, pretreatment of biomass waste: the collected biomass waste is washed with deionized water, then dried and crushed, and then placed in a muffle furnace for pre-carbonization, and then acid washed to obtain a biochar precursor;

[0008] S2, preparing a tungsten salt aqueous solution: preparing a tungsten salt aqueous solution by ultrasonic treatment of a tungsten salt;

[0009] S3, hydrothermal reaction: immersing the biochar precursor into the tungsten salt aqueous solution, adding an oxalic acid solution, and then ultrasonic treatment, and then performing hydrothermal reaction on the mixture after ultrasonic treatment;

[0010] S4, drying, calcination, and washing to obtain a composite catalyst: after the hydrothermal reaction, the mixture is dried in an oven, and then the mixture is calcined under nitrogen protection, and the calcined sample is washed with deionized water until neutral, and then dried to obtain the composite catalyst.

[0011] Preferably, in step S1, the biomass waste is tea residue, which is crushed and then passed through a 100-mesh sieve.

[0012] Preferably, in step S1, the pre-carbonization temperature is 600℃, and the pre-carbonization time is 30min.

[0013] Preferably, in step S1, the acid used for pickling is dilute hydrochloric acid with a concentration of 0.1mol / L.

[0014] Preferably, in step S2, the tungsten salt is Na2WO4·2H2O, the mass ratio of tungsten salt to water is 9.8955:100, the ultrasonic treatment time is 10min, and the concentration of the tungsten salt aqueous solution is 0.3mol / L.

[0015] Preferably, in step S3, the molar ratio of the oxalic acid solution to the tungsten salt aqueous solution is 1:1, the ultrasonic treatment time is 10min, the temperature of the hydrothermal reaction is 180℃, and the time of the hydrothermal reaction is 24h.

[0016] Preferably, in step S4, the calcination temperature is 800℃, and the holding time is 2h.

[0017] In another aspect, to achieve the above-mentioned purpose, the application also provides the following technical scheme: application of a composite catalyst in a carbon cloth electrode of an iron-chromium flow battery.

[0018] Preferably, the application specifically includes the following:

[0019] The purchased carbon cloth is pretreated, cut, and then washed with deionized water, and then placed in a muffle furnace for high-temperature activation;

[0020] The composite catalyst is mixed with a binder, and after ultrasonic treatment, a catalyst ink is obtained, and then the pretreated carbon cloth is placed in the catalyst ink, and after standing, drying is performed;

[0021] The above steps are repeated multiple times until the ink is completely absorbed, and a carbon cloth electrode modified by the composite catalyst is obtained.

[0022] Preferably, the carbon cloth size is 540mm*200mm; the high-temperature activation temperature is 500 DEG C, and the time is 2h.

[0023] The application has the advantages that: the application uses organic solid waste as the base, utilizes the characteristics of the developed pore structure after carbonization, and combines with sodium tungstate which can promote the improvement of battery performance, to prepare a composite catalyst which can be applied to the carbon cloth of the iron-chromium liquid flow battery negative electrode. The catalyst is applied to the carbon cloth electrode of the iron-chromium liquid flow battery, which can improve the hydrophilicity and conductivity of the carbon cloth, and improve the capacity retention rate of the carbon cloth, and promote the improvement of the electrochemical performance of the battery. In the liquid flow battery with continuous electrolyte flow, the electrochemical performance of the electrode is stable, and the capacity retention rate is 50% higher than that of the original carbon cloth after 60 times of charge-discharge cycle, and has good capacity retention rate. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a scanning electron microscope photo of unmodified carbon cloth;

[0025] Figure 2 It is a contact angle diagram of unmodified carbon cloth;

[0026] Figure 3 It is a contact angle diagram of the carbon cloth of example 1;

[0027] Figure 4 It is a contact angle diagram of the carbon cloth of example 4;

[0028] Figure 5 It is a contact angle diagram of the carbon cloth of example 5;

[0029] Figure 6 It is a battery capacity retention rate curve of example 4. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0031] The application provides a technical solution: a preparation method of a composite catalyst for an iron-chromium liquid flow battery electrode, which specifically comprises the following steps:

[0032] S1, pretreatment of biomass waste: the collected biomass waste (tea dregs) is washed with deionized water, then dried and crushed (after crushing, pass through a 100 mesh sieve), and placed in a muffle furnace for pre-carbonization, the pre-carbonization temperature is 600℃, the pre-carbonization time is 30min, and then it is washed with acid (dilute hydrochloric acid, concentration is 0.1mol / L) to obtain a biochar precursor;

[0033] S2, preparation of tungsten salt aqueous solution: the tungsten salt is treated by ultrasonic to prepare a tungsten salt aqueous solution;

[0034] The tungsten salt is Na2WO4·2H2O, the mass ratio of tungsten salt to water is 9.8955 or 6.597 or 13.194:100, the ultrasonic treatment time is 10min, and the concentration of the tungsten salt aqueous solution is 0.2-0.4mol / L.

[0035] S3, hydrothermal reaction: the biochar precursor is immersed in the tungsten salt aqueous solution, oxalic acid solution is added, then ultrasonic treatment is performed for 10min, the mixture after ultrasonic treatment is poured into a reaction kettle, then transferred to an oven, and finally hydrothermal reaction is performed, the temperature is 180℃, and the time is 24h;

[0036] The molar ratio of the oxalic acid solution to the tungsten salt aqueous solution is 1:1.

[0037] S4, drying, calcination and washing to obtain a composite catalyst: after the hydrothermal reaction is completed, the mixture is placed in an oven for drying, then the mixture is placed in a tube furnace for calcination under nitrogen protection, the calcination temperature is 600-800℃, the holding time is 2-4h, the calcined sample is washed with deionized water until neutral, and after drying, the composite catalyst is obtained.

[0038] The application of the composite catalyst prepared by the above preparation method in an iron-chromium flow battery carbon cloth electrode specifically includes the following:

[0039] The purchased carbon cloth is pretreated, cut and washed with deionized water, and then placed in a muffle furnace for high temperature activation; the carbon cloth is a commercially available PAN-based carbon cloth with a thickness of 0.167mm, and the size of the carbon cloth is 540mm×200mm; the high temperature activation temperature is 500℃, and the time is 2h;

[0040] The composite catalyst is mixed with a binder, and after ultrasonic treatment, a catalyst ink is obtained, and then the pretreated carbon cloth is placed in it, and after standing, drying is performed;

[0041] Repeat several times until the ink is completely absorbed, and a carbon cloth electrode modified by the composite catalyst is obtained.

[0042] Further, the adhesive is N,N-dimethylformamide (DMF); the mass-volume ratio of the composite catalyst and N,N-dimethylformamide (DMF) is 1 mg:2.2 ml.

[0043] A single cell was assembled with a commercially available carbon cloth, and the electrode area was 540 mm x 200 mm. The micrograph of the commercially available unmodified carbon cloth is shown in Figure 1 The hydrophilicity is shown in Figure 2 The supporting electrolyte is a 2 mol / L HCl solution, the iron ion concentration in the electrolyte is 1.2 mol / L, and the chromium ion concentration is 1.4 mol / L.

[0044] Example 1

[0045] A preparation method of a composite catalyst for an iron-chromium flow battery electrode, specifically comprising the following:

[0046] S1, biomass waste pretreatment: the collected biomass waste (tea dregs) is washed with deionized water, then dried and crushed (after crushing, pass through a 100 mesh sieve), and placed in a muffle furnace for pre-carbonization, the pre-carbonization temperature is 600℃, the pre-carbonization time is 30 min, and then it is washed with acid (dilute hydrochloric acid, concentration is 0.1 mol / L) to obtain a biochar precursor;

[0047] S2, preparation of a tungsten salt aqueous solution: the tungsten salt is treated by ultrasonic to prepare a tungsten salt aqueous solution;

[0048] The tungsten salt is Na2WO4·2H2O, the mass ratio of tungsten salt to water is 6.597:100, the ultrasonic treatment time is 10 min, and the concentration of the tungsten salt aqueous solution is 0.2 mol / L.

[0049] S3, hydrothermal reaction: the biochar precursor is immersed in the tungsten salt aqueous solution, oxalic acid solution is added, then ultrasonic treatment is performed for 10 min, the mixture after ultrasonic treatment is poured into a reaction kettle, then transferred to an oven, and finally hydrothermal reaction is performed, the temperature is 180℃, and the time is 24 h;

[0050] The molar ratio of the oxalic acid solution to the tungsten salt aqueous solution is 1:1.

[0051] S4, drying, calcination, and washing to obtain a composite catalyst: after the hydrothermal reaction is completed, the mixture is placed in an oven for drying, then the mixture is placed in a tube furnace for calcination under the protection of nitrogen, the calcination temperature is 800℃, the holding time is 2 h, the calcined sample is washed with deionized water until neutral, and after drying, the composite catalyst is obtained.

[0052] Example 2

[0053] A preparation method of a composite catalyst for an electrode of an iron-chromium flow battery, the steps are basically the same as those of embodiment 1, except that the calcination time of step S4 is 3h.

[0054] Example 3

[0055] A preparation method of a composite catalyst for an electrode of an iron-chromium flow battery, the steps are basically the same as those of embodiment 1, except that the calcination time of step S4 is 4h.

[0056] Comparing the results of comparative examples 1-3, the preferred calcination time is 2h. After loading the composite catalyst on the carbon cloth, the hydrophilicity is improved, as shown in Figure 3 .

[0057] Example 4

[0058] A preparation method of a composite catalyst for an electrode of an iron-chromium flow battery, the steps are basically the same as those of embodiment 1, except that in step S2, a 0.3mol / L aqueous tungstate solution is prepared according to a mass ratio of Na2WO4·2H2O:water of 9.8955:100. Using this composite catalyst, the hydrophilicity of the carbon cloth is significantly improved, as shown in Figure 4 .

[0059] Example 5

[0060] A preparation method of a composite catalyst for an electrode of an iron-chromium flow battery, the steps are basically the same as those of embodiment 1, except that in step S2, a 0.4mol / L aqueous tungstate solution is prepared according to a mass ratio of Na2WO4·2H2O:water of 13.194:100. Using this composite catalyst, the hydrophilicity of the carbon cloth is also significantly improved, as shown in Figure 5 .

[0061] Comparing the results of comparative examples 1-5, the preferred aqueous tungstate solution is prepared according to a mass ratio of Na2WO4·2H2O:water of 9.8955:100. Thus, the composite catalyst is obtained by combining with the tea dregs biochar. The carbon cloth electrode loaded with the composite catalyst has improved hydrophilicity, and after 60 cycles of the battery, the battery capacity retention curve is as shown in Figure 6 , the battery capacity decays more slowly than the battery without catalyst loading, and is 50% higher than the battery without catalyst loading.

[0062] The present application uses organic solid waste as the base, takes advantage of its developed pore structure after carbonization, and combines with sodium tungstate which can promote the improvement of battery performance, to prepare a composite catalyst that can be applied to the carbon cloth negative electrode of the iron-chromium flow battery. The catalyst is applied to the carbon cloth electrode of the iron-chromium flow battery, which can well improve the hydrophilicity and conductivity of the carbon cloth, and can improve the capacity retention rate of the carbon cloth, and promote the improvement of the electrochemical performance of the battery.

[0063] The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the description of the application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0064] Although the application has been described with reference to the aforementioned embodiments, it will be understood that the technical solutions recorded in the aforementioned embodiments can be modified, or some technical features thereof can be replaced equivalently by those skilled in the art, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. An iron-chromium flow battery carbon cloth electrode, characterized in that, The preparation of the carbon cloth electrode comprises the following steps: The purchased carbon cloth is pretreated, cut, cleaned with deionized water, and then placed in a muffle furnace for high-temperature activation. The high-temperature activation temperature is 500 ℃, and the time is 2 h. The composite catalyst is mixed with the binder, and the catalyst ink is obtained after ultrasonic treatment. Then, the pretreated carbon cloth is placed in the catalyst ink, and after standing, it is dried. Repeat several times until the ink is completely absorbed, and a carbon cloth electrode modified by the composite catalyst is obtained. The preparation of the composite catalyst comprises the following steps: S1, biomass waste pretreatment: the collected biomass waste is washed with deionized water, then dried and crushed, and then placed in a muffle furnace for pre-carbonization. Then, it is acid washed to obtain a biochar precursor. The biomass waste is tea residue, which is crushed and sieved through a 100-mesh sieve; S2, preparation of tungsten salt aqueous solution: tungsten salt is treated by ultrasonic to prepare a tungsten salt aqueous solution; S3, hydrothermal reaction: the biochar precursor is immersed in the tungsten salt aqueous solution, oxalic acid solution is added, and then ultrasonic treatment is performed. The mixture after ultrasonic treatment is subjected to hydrothermal reaction; S4, drying, calcination, and washing to obtain a composite catalyst: after the hydrothermal reaction is completed, the mixture is placed in an oven for drying. Then, the mixture is calcined under nitrogen protection. The calcination temperature is 800 ℃, and the holding time is 2 h. The calcined sample is washed with deionized water until it is neutral. After drying, the composite catalyst is obtained.

2. The ferric-chromic flow battery carbon cloth electrode of claim 1, wherein: In step S1, the pre-carbonization temperature is 600 ℃, and the pre-carbonization time is 30 min.

3. The ferric-chromic flow battery carbon cloth electrode of claim 1, wherein: In step S1, the acid used for acid washing is dilute hydrochloric acid with a concentration of 0.1 mol / L.

4. The ferric-chromic flow battery carbon cloth electrode of claim 1, wherein: In step S2, the tungsten salt is Na2WO4·2H2O, the mass ratio of tungsten salt to water is 9.8955:100, the ultrasonic treatment time is 10 min, and the concentration of the tungsten salt aqueous solution is 0.3 mol / L.

5. The ferric-chromic flow battery carbon cloth electrode of claim 1, wherein: In step S3, the molar ratio of oxalic acid solution to tungsten salt aqueous solution is 1:1; the ultrasonic treatment time is 10 min; the hydrothermal reaction temperature is 180 ℃, and the time is 24 h.

6. The ferric-chromic flow battery carbon cloth electrode of claim 1, wherein: The size of the carbon cloth is 540 mm x 200 mm.

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