A device and method for preparing electrolyte for all-vanadium liquid flow battery by catalytic reduction

Abstract

The present invention proposes a device and method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction. The device comprises an outer tube and an inner tube, an oil bath chamber is formed between the outer tube and the inner tube, the inner tube constitutes a reaction chamber, and a graphite felt loaded with a catalyst is arranged in the reaction chamber; the method comprises preparing graphene oxide, preparing a catalyst, and catalytically oxidizing formic acid to prepare a vanadium electrolyte. Based on the device and method of the present application, the reaction rate is improved while taking into account the preparation cost.

Description

Technical Field

[0001] The invention belongs to the technical field of all-vanadium liquid flow battery electrolyte preparation, and specifically relates to a device and method for preparing all-vanadium liquid flow battery electrolyte by catalytic reduction. Background Art

[0002] With the increasing consumption of resources and the intensification of environmental problems, traditional power systems will gradually be replaced by clean and renewable energy sources such as wind and solar energy, becoming the main force of the power generation system. Electrochemical energy storage technology can effectively cope with the volatility of renewable energy systems, so it is regarded as an ideal choice for large-scale energy storage power stations. Among them, flow batteries stand out in long-term energy storage technology with their advantages such as high safety, long cycle life and recyclable electrolytes. In particular, vanadium redox flow batteries (VRFBs), whose cathode and anode solutions are both composed of vanadium ions, effectively avoid the problem of active substances crossing the membrane. However, the production cost of vanadium electrolytes is still the main obstacle to large-scale deployment and market promotion.

[0003] The methods for synthesizing the electrolyte of all-vanadium liquid flow batteries include: physical method, chemical method and electrolytic method. The physical method is mainly to dissolve trivalent or tetravalent vanadium oxide in a sulfuric acid solution of a certain concentration to obtain it directly, but due to the high price of vanadium oxide raw materials and high cost, it cannot be applied industrially on a large scale. At present, the synthesis of electrolytes for industrial all-vanadium liquid flow batteries is mainly chemical method and electrolytic method. The electrolytic method can obtain impurity-free vanadium electrolyte, but the complex equipment and electrode materials are prone to corrosion, resulting in high manufacturing costs, especially the process of converting tetravalent vanadium electrolyte to trivalent vanadium, which consumes a lot of electricity; the chemical method uses a reducing agent to reduce high-valent vanadium compounds to low-valent vanadium, which effectively reduces costs, but the existing chemical reduction method has the disadvantage of slow reaction rate. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a device and method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction, so as to improve the reaction rate while taking into account the preparation cost.

[0005] The present invention solves the above problems by the following technical means:

[0006] A device for preparing electrolyte for all-vanadium liquid flow battery by catalytic reduction comprises an outer tube and an inner tube, wherein an oil bath cavity is formed between the outer tube and the inner tube, and the inner tube forms a reaction cavity, wherein graphite felt loaded with catalyst is arranged in the reaction cavity.

[0007] Furthermore, the graphite felts are discretely arranged or closely arranged, with a number of 20-30.

[0008] Furthermore, an oil inlet is provided at the top of the outer tube, and an oil outlet is provided at the bottom of the outer tube.

[0009] A method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction using the above-mentioned device comprises the following steps:

[0010] S1: Add 0.5-1.5 parts of graphite powder to 20-25 parts of concentrated sulfuric acid, and place in a water bath at 0-10°C for 20-40 minutes. Then add 2.5-3.5 parts of potassium permanganate, raise the temperature to 20-40°C, and continue stirring for 0.5-1h. Then add 40-60 parts of deionized water, raise the temperature to 80-100°C, and stir for 10-20 minutes. Then add 8-12 parts of hydrogen peroxide solution, remove excess potassium permanganate, and then fully centrifuge and wash, and then dry to obtain graphene oxide;

[0011] S2: 6.5-6.9 parts of platinum precursor solution, 0.1-0.15 parts of graphene oxide and 0.1-0.15 parts of hexadecyltrimethylammonium bromide are placed in 100-130 parts of ethylene glycol solution, and stirred continuously for 1-1.5 hours at a stirring rate of 400-450 rad / / min. After adjusting the pH to 9-10, reflux at 120-180°C for 6-8 hours, and then centrifugally wash 3-5 times at a speed of 5000-8000 rad / min for 10-20 minutes, and finally freeze-dry for 48-50 hours to obtain a catalyst;

[0012] S3: The prepared catalyst is added to an ethanol solution containing naphthol, and the catalyst is loaded into graphite felt by ultrasound. After drying, the catalyst is placed in a reaction chamber, and 1.5-1.6 parts of a high-valent vanadium compound, 3-4 parts of sulfuric acid and 5-7 parts of formic acid are added to the reaction chamber. The oil temperature of the oil bath chamber is controlled to be constant, and vanadium electrolyte is prepared by continuous catalytic reduction.

[0013] Furthermore, the temperature of the oil bath chamber is 60-100°C.

[0014] Furthermore, in the catalyst, the mass ratio of hexadecyltrimethylammonium bromide to platinum is 0.5-1:1.

[0015] Furthermore, in the catalyst, the loading amount of platinum is 20-40%.

[0016] Furthermore, the molar concentration of the sulfuric acid is 3-4 mol / L.

[0017] Furthermore, the amount of formic acid exceeds the theoretical amount by 5-8%.

[0018] Furthermore, the high-valent vanadium compound is vanadium pentoxide, ammonium metavanadate or vanadyl sulfate.

[0019] Beneficial effects of the present invention:

[0020] The prepared catalyst Pt / GO@CTAB has higher catalytic activity than the existing Pt / C catalyst and can reduce the cost of platinum metal;

[0021] In the process of catalytic oxidation of formic acid to prepare vanadium electrolyte, the efficiency is increased by 42.86% compared with traditional catalysts;

[0022] The obtained electrolyte contains CTAB, which has higher battery performance, including energy efficiency and capacity retention rate, than electrolytes prepared by other catalysts.

[0023] The designed catalytic reaction device does not require filtering the catalyst and can reduce high-valent vanadium compounds into directly usable 3.5-valent vanadium electrolyte in one step, which is more efficient and convenient than traditional reduction methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] Figure 1 A schematic diagram of a device for preparing electrolyte for all-vanadium liquid flow battery by catalytic reduction according to a preferred embodiment of the present invention;

[0026] Figure 2 Schematic diagram of the preparation process of the catalyst;

[0027] Figure 3 This is a graph showing the average conversion rate changes of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention.

[0028] Figure 4 Graphs showing the energy efficiency of batteries according to Example 1, Comparative Example 1 and Comparative Example 2 of the present invention.

[0029] Figure 5 The battery capacity attenuation change diagram of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] like Figure 1As shown, this embodiment first discloses a device for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction, comprising an outer tube 1 and an inner tube 2, wherein an oil bath chamber is formed between the outer tube and the inner tube, and the inner tube forms a reaction chamber, wherein graphite felt 3 loaded with a catalyst is arranged in the reaction chamber; the graphite felts are discretely or closely arranged, and the number is 20-30; an oil inlet 4 is provided on the top of the outer tube, and an oil outlet 5 is provided on the bottom of the outer tube, one end of the inner tube is a reaction stock solution inlet 6, and the other end is a vanadium electrolyte outlet 7, and the high-valent vanadium compound, sulfuric acid solution and formic acid mixed suspension of the reference reaction enter the reaction chamber from the reaction stock solution inlet to participate in the reaction.

[0032] This embodiment also provides a method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction using the above-mentioned device. The process flow is as follows: Figure 2 As shown, the invention is specifically described in the following embodiments.

[0033] In the following embodiments, the concentration test instrument is a ZDJ-4A automatic potentiometric titrator from Shanghai Yifen Scientific Instrument Co., Ltd.; the high-performance battery detection system is a CT-4008Tn-5V / 12A-S1-F from Shenzhen Xinwell Electronics Co., Ltd.; graphite powder is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a product number of G434784; potassium permanganate is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a product number of P477466; formic acid solution is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a product number of F301789; formic acid solution is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a product number of F301789; platinum precursor solution is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a product number of C139933; CTAB is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a product number of H108983.

[0034] Example 1

[0035] A method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction using the above-mentioned device comprises the following steps:

[0036] S1: Weigh 1g of graphite powder on a scale, add 20mL of concentrated sulfuric acid and place in an ice-water bath at 0℃ for 30min, then slowly add 3g of potassium permanganate, heat to 35℃ and stir for 1h, then add 50mL of deionized water, heat to 98℃ and stir for 15min, then add 10mL of hydrogen peroxide solution to remove excess potassium permanganate, then centrifuge and wash thoroughly, and dry to obtain GO (graphene oxide);

[0037] S2: Use a pipette to measure 6.836 mL of platinum precursor solution (0.05 M), 0.1 g of GO and 0.1 g of CTAB (hexadecyltrimethylammonium bromide), put them into 125 mL of ethylene glycol solution, and stir continuously for 1 hour at a stirring rate of 450 rad / / min. After adjusting the pH to 9.5 with KOH (0.1 M), reflux at 120 ° C for 6 hours, then centrifuge and wash 3 times at a speed of 5000 rad / min for 20 minutes, and finally freeze-dry for 48 hours to obtain the catalyst Pt / GO@CTAB.

[0038] S3: The prepared catalyst was added to the ethanol solution containing naphthol, loaded into the graphite felt by ultrasound, and placed in the reaction chamber after drying. 16.38 g V was weighed on a balance. 2 O 5 , 120 ml of sulfuric acid (3 M) and 6.28 g of formic acid, the outer tube oil bath temperature is 80°C, and continuous catalytic reduction is performed to prepare a 3.5-valent vanadium electrolyte (1.5 M).

[0039] The prepared electrolyte was titrated by ferrous sulfate reduction method to analyze the concentration, and the concentration of trivalent vanadium was obtained: the concentration of tetravalent vanadium = 1.02.

[0040] Example 2

[0041] A method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction using the above-mentioned device comprises the following steps:

[0042] S1: Weigh 1.5g of graphite powder on a balance, add 25mL of concentrated sulfuric acid, place in an ice-water bath at 0℃ for 30min, then slowly add 3.5g of potassium permanganate, heat to 35℃ and continue stirring for 2h, then add 60mL of deionized water, heat to 98℃ and stir for 20min, then add 15mL of hydrogen peroxide solution to remove excess potassium permanganate, then centrifuge and wash thoroughly, and dry to obtain GO.

[0043] S2: Use a pipette to measure 6.836 mL of platinum precursor solution (0.05 M), 0.1 g of GO and 0.1 g of CTAB, put them into 125 mL of ethylene glycol solution, and stir continuously for 1 hour at a stirring rate of 500 rad / / min. After adjusting the pH to 9.5 with KOH (0.1 M), reflux at 150 ° C for 7 hours, then centrifuge and wash three times at a speed of 6000 rad / min for 15 minutes, and finally freeze-dry for 49 hours to obtain the catalyst Pt / GO@CTAB.

[0044] S3: The prepared catalyst is added to an ethanol solution containing naphthol, loaded onto graphite felt using ultrasound, and placed in a reaction chamber after drying. 13.65 g of V2O5, 100 ml of sulfuric acid (3 M) and 5.23 g of formic acid are weighed on a balance. The oil bath temperature of the outer tube is 60°C, and continuous catalytic reduction is performed to prepare a 3.5-valent vanadium electrolyte (1.5 M).

[0045] The prepared electrolyte was titrated by ferrous sulfate reduction method to analyze the concentration, and the concentration of trivalent vanadium was obtained: the concentration of tetravalent vanadium = 1.01.

[0046] Example 3

[0047] A method for preparing an electrolyte for an all-vanadium liquid flow battery by catalytic reduction using the above-mentioned device comprises the following steps:

[0048] S1: Weigh 1.5g of graphite powder on a balance, add 25mL of concentrated sulfuric acid, place in an ice-water bath at 0℃ for 30min, then slowly add 3.5g of potassium permanganate, heat to 35℃ and continue stirring for 2h, then add 60mL of deionized water, heat to 98℃ and stir for 20min, then add 15mL of hydrogen peroxide solution to remove excess potassium permanganate, then centrifuge and wash thoroughly, and dry to obtain GO.

[0049] S2: Use a pipette to measure 6.836 mL of platinum precursor solution (0.05 M), 0.5 g of GO and 0.1 g of CTAB, put them into 125 mL of ethylene glycol solution, and stir continuously for 1 hour at a stirring rate of 600 rad / / min. After adjusting the pH to 9.5 with KOH (0.1 M), reflux at 180 ° C for 8 hours, then centrifuge and wash three times at a speed of 8000 rad / min for 20 minutes, and finally freeze-dry for 50 hours to obtain the catalyst Pt / GO@CTAB.

[0050] S3: The prepared catalyst is added to an ethanol solution containing naphthol, loaded onto graphite felt using ultrasound, and placed in the inner tube of a reactor after drying. 20.475 g of V2O5, 150 ml of sulfuric acid (3 M) and 7.85 g of formic acid are weighed on a balance. The oil bath temperature of the outer tube is 100°C, and continuous catalytic reduction is performed to prepare a 3.5-valent vanadium electrolyte (1.5 M).

[0051] The prepared electrolyte was titrated by ferrous sulfate reduction method to analyze the concentration, and the concentration of trivalent vanadium was obtained: the concentration of tetravalent vanadium = 1.01.

[0052] Comparative Example 1

[0053] S1: Weigh 1g of graphite powder on a balance, add 20mL of concentrated sulfuric acid, place in an ice-water bath at 0℃ for 30min, then slowly add 3g of potassium permanganate, heat to 35℃ and continue stirring for 1h, then add 50mL of deionized water, heat to 98℃ and stir for 15min, then add 10mL of hydrogen peroxide solution to remove excess potassium permanganate, then centrifuge and wash thoroughly, and dry to obtain GO.

[0054] S2: Use a pipette to measure 6.836 mL of platinum precursor solution (0.05 M) and 0.1 g of GO and put them into 125 mL of ethylene glycol solution. Stir continuously for 1 hour at a stirring rate of 450 rad / / min. Adjust the pH to 9.5 with KOH (0.1 M) and reflux at 120 ° C for 6 hours. Then centrifuge and wash three times at a speed of 5000 rad / min for 20 minutes. Finally, freeze-dry for 48 hours to obtain the catalyst Pt / GO.

[0055] S3: Add naphthol-containing ethanol solution to the prepared catalyst, load it onto graphite felt using ultrasound, dry it and place it in the inner tube of the reactor, weigh 16.38 g of V2O5, 120 ml of sulfuric acid (3M) and 6.28 g of formic acid using a balance, set the oil bath temperature of the outer tube at 80°C, and perform continuous catalytic reduction to prepare a 3.5-valent vanadium electrolyte (1.5M).

[0056] The prepared electrolyte was titrated by ferrous sulfate reduction method to analyze the concentration, and the concentration of trivalent vanadium was obtained: the concentration of tetravalent vanadium = 1.03.

[0057] Comparative Example 2

[0058] S1: Add naphthol-containing ethanol solution to the prepared catalyst, use ultrasound to load the existing catalyst Pt / C (40%) into the graphite felt, place it in the inner tube of the reactor after drying, weigh 16.38g V2O5, 120ml sulfuric acid (3M) and 6.28g formic acid on a balance, set the oil bath temperature of the outer tube at 80°C, and continue catalytic reduction to prepare a 3.5-valent vanadium electrolyte (1.5M).

[0059] The prepared electrolyte was titrated by ferrous sulfate reduction method to analyze the concentration, and the concentration of trivalent vanadium was obtained: the concentration of tetravalent vanadium = 1.02.

[0060] Comparative Example 3

[0061] S1: Without placing any catalyst in the reaction chamber, 16.38 g of V2O5, 120 ml of sulfuric acid (3 M) and 6.28 g of formic acid were weighed on a balance, the outer tube oil bath temperature was 80°C, and 3.5-valent vanadium electrolyte (1.5 M) was prepared by continuous catalytic reduction.

[0062] The prepared electrolyte was titrated by ferrous sulfate reduction method to analyze the concentration, and the concentration of trivalent vanadium was obtained: the concentration of tetravalent vanadium=0.

[0063] Test Example 1

[0064] The electrolytes prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested for concentration. Figure 3 ,Depend on Figure 3 It can be seen that the presence of a catalyst is a necessary condition in the method for preparing an electrolyte by catalytic reduction described in the present invention, and the new catalyst Pt / GO@CTAB containing CTAB proposed in the present invention has a faster catalytic rate than the traditional commercial catalysts Pt / C and Pt / GO. Compared with Pt / C, the catalytic rate of Pt / GO@CTAB proposed in the present invention is increased by 42.86%. In addition, the energy efficiency of the electrolyte obtained in Example 1, Comparative Example 1 and Comparative Example 2 in the all-vanadium redox flow battery under the same conditions is as follows: Figure 4 As shown, the new catalyst Pt / GO@CTAB containing CTAB proposed in the present invention has higher energy efficiency than the traditional commercial catalysts Pt / C and Pt / GO, indicating that the catalyst preparation process of adding CTAB proposed in the present invention has the advantage of improving the electrochemical performance of vanadium electrolyte. Finally, the electrolyte prepared in Example 1, Comparative Example 1 and Comparative Example 2 was subjected to 30 cycles of charge and discharge experiments to obtain the capacity retention rate of the battery, as shown in FIG. Figure 5 As shown, it can be seen that the new catalyst Pt / GO@CTAB containing CTAB proposed in the present invention has a higher capacity retention rate and a higher electrolyte utilization rate, and can effectively reduce the cost of all-vanadium liquid flow batteries.

[0065] The conversion rate is calculated by sampling and testing the concentration of tetravalent vanadium and total vanadium concentration at equal time intervals, and is obtained by the formula a=CIV / Ctotal, where a is the conversion rate, CIV is the tetravalent vanadium concentration, and Ctotal is the total vanadium concentration; the concentration test instrument is the ZDJ-4A automatic potentiometric titrator of Shanghai Yifen Scientific Instrument Co., Ltd., the titrant is ammonium ferrous sulfate standard solution, the titration method is ammonium ferrous sulfate titration method, standard number: GB / T 8704.5-2020. The capacity decay change is obtained by automatically recording the discharge capacity at the initial value during the charge and discharge cycle by a high-performance battery detection system. The high-performance battery detection system is CT-4008Tn-5V / 12A-S1-F of Shenzhen Xinwell Electronics Co., Ltd. Figure 5 shown.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction, characterized in that: The device used includes an outer tube and an inner tube, an oil bath chamber is formed between the outer tube and the inner tube, the inner tube forms a reaction chamber, a graphite felt loaded with a catalyst is arranged in the reaction chamber, an oil inlet is opened at the top of the outer tube, and an oil outlet is opened at the bottom of the outer tube; The steps include: S1: Add 0.5-1.5 parts of graphite powder to 20-25 parts of concentrated sulfuric acid, and place in a water bath at 0-10°C for 20-40 minutes. Then add 2.5-3.5 parts of potassium permanganate, raise the temperature to 20-40°C, and continue stirring for 0.5-1h. Then add 40-60 parts of deionized water, raise the temperature to 80-100°C, and stir for 10-20 minutes. Then add 8-12 parts of hydrogen peroxide solution, remove excess potassium permanganate, and then fully centrifuge and wash, and then dry to obtain graphene oxide; S2: 6.5-6.9 parts of platinum precursor solution, 0.1-0.15 parts of graphene oxide and 0.1-0.15 parts of hexadecyltrimethylammonium bromide are placed in 100-130 parts of ethylene glycol solution, and stirred continuously for 1-1.5 hours at a stirring rate of 400-450 rad / min. After adjusting the pH to 9-10, reflux at 120-180°C for 6-8 hours, and then centrifugally wash 3-5 times at a speed of 5000-8000 rad / min for 10-20 minutes, and finally freeze-dry for 48-50 hours to obtain a catalyst; S3: The prepared catalyst is added to an ethanol solution containing naphthol, and the catalyst is loaded into graphite felt by ultrasound. After drying, the catalyst is placed in a reaction chamber, and 1.5-1.6 parts of a high-valent vanadium compound, 3-4 parts of sulfuric acid and 5-7 parts of formic acid are added to the reaction chamber. The oil temperature of the oil bath chamber is controlled to be constant, and vanadium electrolyte is prepared by continuous catalytic reduction.

2. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 1, characterized in that: The graphite felts are arranged discretely or closely, with a number of 20-30.

3. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 1, characterized in that: The temperature of the oil bath chamber is 60-100°C.

4. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 3, characterized in that: In the catalyst, the mass ratio of hexadecyltrimethylammonium bromide to platinum is 0.5-1:

1.

5. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 4, characterized in that: In the catalyst, the loading amount of platinum is 20-40%.

6. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 5, characterized in that: The molar concentration of the sulfuric acid is 3-4 mol / L.

7. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 6, characterized in that: The amount of formic acid is 5-8% in excess of the theoretical amount.

8. The method for preparing an electrolyte for an all-vanadium redox flow battery by catalytic reduction according to claim 7, characterized in that: The high-valent vanadium compound is vanadium pentoxide, ammonium metavanadate or vanadyl sulfate.

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