CN111509238A - A kind of preparation method of macroscopic graphene modified electrode material - Google Patents

Abstract

The invention discloses a preparation method of a macroscopic quantity graphene modified electrode material, relates to the field of electrode materials for all vanadium redox flow batteries (VRB), in particular to a preparation method of a high-performance macroscopic quantity graphene modified carbon felt suitable for all vanadium redox flow batteries, and solves the problems of poor conductivity, low specific surface area, low electrochemical activity, poor catalytic performance of vanadium ion electric pairs, low performance of single cells, high cost and the like of commercial carbon felts for vanadium batteries at the present stage. The invention takes a commercial carbon felt as a raw material and utilizes a Chemical Vapor Deposition (CVD) method to prepare the graphene modified carbon felt. The composite carbon felt prepared by the invention has the advantages of good conductivity, high specific surface area, good electrochemical catalytic performance, excellent chemical stability, good VRB battery performance, low cost and the like. The preparation method has the advantages of simple and easy operation, low product cost, easy industrial production, environmental protection and the like, and can be widely applied to the field of all-vanadium redox flow batteries.

Description

A kind of preparation method of macroscopic graphene modified electrode material

Technical field:

The invention relates to the field of electrode materials for all-vanadium redox flow batteries (VRB), in particular to a preparation method of a high-performance macro-scale graphene modified electrode material suitable for all-vanadium redox flow batteries.

Background technique:

With the rapid growth of the global population and rapid economic development, the energy crisis is becoming more and more serious. The development of new energy is an effective way to solve the energy crisis. Renewable and clean energy is currently a hot spot in scientific research and industrial development because of its environmental friendliness and sustainability. Renewable energy generation processes such as wind and solar show the disadvantages of discontinuity and instability. Therefore, it is urgent to develop efficient, environmentally friendly, low-cost, safe and reliable large-scale energy storage technologies. All-vanadium redox flow batteries (VRBs) are widely used in large-scale wind and solar power generation processes due to their power and energy independence, simple and flexible design, long cycle life, fast charge and discharge, and low operating costs. energy storage equipment. At the same time, VRB is also a large-scale energy storage technology widely tried in the fields of power station energy storage and power grid peak regulation in recent years. However, the commercialization of vanadium batteries is currently limited by high costs. Among them, the electrode material is the key factor that determines the cost of the stack. An electrode material suitable for vanadium batteries should have the advantages of excellent electrical conductivity, high specific surface area, superior electrochemical activity and low cost. Electrodes of traditional metal materials have poor electrochemical reversibility and are easily passivated by acidic electrolytes; while noble metals such as platinum and iridium have the advantages of high electrochemical activity, good catalytic performance and good chemical stability, but such materials are expensive, It restricts its large-scale application in vanadium batteries. At present, the most widely used electrode materials for vanadium batteries are carbon materials, such as graphite felt, graphite, carbon cloth and carbon fiber. However, the direct application of such carbon materials has problems such as low electrical conductivity, poor electrochemical activity, and poor battery performance. In view of this, such carbon-based materials must be modified to improve the electrical conductivity and electrochemical activity of electrodes. As of now, there is still no suitable method to solve these key problems.

Invention content:

In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for preparing a macro-scale graphene modified electrode material suitable for vanadium batteries, which solves the problems of poor electrical conductivity, low chemical activity, and low carbon felt in the prior art. Low surface area, poor stability, poor performance in VRB and high cost of VRB. Using this method, a low-cost and high-performance composite carbon felt can be obtained, which has the advantages of high electrical conductivity, high specific surface area, high electrochemical activity, good catalytic performance for vanadium ions, good stability, and good performance in VRB battery applications.

Concrete technical scheme of the present invention:

A preparation method of a macroscopic graphene modified electrode material, comprising the following steps and process conditions:

(1) Soak the dried carbon felt in an acid solution, soak it at room temperature for a certain period of time, and then ultrasonically vibrate it for a certain period of time; wherein, the time for soaking the carbon felt in the acid solution is 12-18h, and the ultrasonic oscillation time is 0.5-1.5h ;

(2) the carbon felt in step (1) is repeatedly cleaned with deionized water;

(3) drying the cleaned carbon felt;

(4) Put the 20cm×20cm×5.5mm carbon felt on the graphite uniform heating sample stage at the bottom of the preparation chamber, and align the sample with the gas outlet direction at the top of the preparation chamber;

(5) Open the _H2 valve on the preparation chamber, clean it for 1-3 minutes, and close the _H2 valve;

(6) Open the CH ₄ valve on the preparation chamber, clean it for 1 to 3 minutes, and close the CH ₄ valve;

(7) Open the high vacuum valve on the preparation chamber, manually open the high vacuum unit, and evacuate for 4 to 6 minutes, so that the vacuum degree in the preparation chamber is 2.5×10 ^-2 to 3×10 ^-3 Pa; close the high vacuum valve and manually Turn off the high vacuum unit;

( ₈ ) open the H valve, adjust the gas flow to be 150～200sccm, heat the preparation chamber to a temperature of 1000±10°C, and the temperature rise time is 100～120min;

(9) Keep the temperature at 1000±10℃ for 5-20min;

(10) During the holding time, open the _CH4 valve, adjust the gas flow to 20～30sccm, and maintain the reaction time to be 5～20min;

(11) Close the CH ₄ valve, maintain the H ₂ flow at 150-200sccm, and cool with the furnace;

(12) After the temperature dropped to room temperature, the H valve was closed to obtain a graphene _- modified carbon felt sample.

In the method for preparing the macro-scale graphene-modified electrode material, in step (1), the temperature for drying the carbon felt is 400-500°C.

In the preparation method of the described macro-scale graphene modified electrode material, in step (1), the acid solution is one of sulfuric acid, nitric acid and hydrochloric acid, and the acid solution concentration is 1-3 mol/L.

In the preparation method of the macro-scale graphene modified electrode material, in step (2), the cleaning times are 10-15 times.

In the preparation method of the macro-scale graphene modified electrode material, in step (3), the drying temperature of the carbon felt is 80-120°C.

In the preparation method of the macro-scale graphene modified electrode material, in step (5), the cleaning times are 3 to 5 times.

In the preparation method of the macro-scale graphene modified electrode material, in step (6), the cleaning times are 3 to 5 times.

In the preparation method of the macro-scale graphene-modified electrode material, in the graphene-modified carbon felt, the graphene loading is 0.3-1 wt%.

The design idea of the present invention is: in the present invention, _CH4 is used as a carbon source, and under the reduction effect of _H2 and high temperature, _CH4 is cracked to obtain graphene. Further, the prepared graphene is evenly coated on the carbon felt, thereby obtaining the graphene carbon felt.

Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

1. the present invention takes commercial carbon felt as raw material, adopts the method for chemical vapor deposition, prepares graphene modified carbon felt electrode material, and this electrode material has high electrical conductivity, large specific surface area, good vanadium ion catalytic performance, good stability, The advantages of high electrochemical catalytic activity.

2. The method for preparing the graphene-modified carbon felt used in the present invention has easily available raw materials, low cost, simple and easy operation, and is suitable for large-scale development.

3. The whole preparation process of the present invention has industrial practical features such as low equipment price, low cost of raw materials and easy availability, simple and convenient operation process, etc., which is helpful for the large-scale production of electrode materials for commercialization of VRB.

In a word, the present invention uses commercial carbon felt as raw material and adopts vapor deposition method to prepare graphene-modified carbon felt composite electrode, which improves the electrical conductivity, specific surface area, electrochemical activity, stability and electrochemical catalytic performance of the carbon felt. Compared with the VRB battery assembled with unmodified commercial carbon felt, the VRB battery with graphene-modified carbon felt has high power density (Fig. 1), as well as high efficiency, superior rate capability and cycling performance (Fig. 2). . High-performance graphene-modified carbon felt composite electrodes were prepared by uniformly depositing graphene with high specific surface area and high conductivity on the surface of commercial carbon felt by vapor deposition method. The raw materials used in this kind of method are cheap and easy to obtain, the operation is simple and convenient, and suitable for large-scale industrial development, and it is expected to prepare a low-cost and high-performance commercial electrode material for vanadium batteries.

Description of drawings:

Figure 1 is the area of the prepared graphene-modified carbon felt. Among them, (a) is the actual graph of the graphene carbon felt of 20cm×20cm×5.5mm; (b) is the cyclic voltammetry curve, the abscissa Voltage represents the voltage (V), and the ordinate Current density represents the current density (mA/cm ^{2 )} . ), Pure CF stands for pristine carbon felt, and G-CF stands for graphene carbon felt.

Figure 2 is a comparison of the efficiency of vanadium cells using commercial carbon felt and graphene-modified carbon felt. In the figure, the abscissa Cyclenumber represents the cycle number, the ordinate Efficiency represents the battery efficiency (%), EE:Pristine CF represents the energy efficiency of the original carbon felt, VE:Pristine CF represents the voltage efficiency of the original carbon felt, EE:G/CF represents Energy efficiency of graphene carbon felt, VE:G/CF represents the voltage efficiency of graphene carbon felt.

Detailed ways:

In the specific implementation process, the present invention uses commercial carbon felt as a raw material, and adopts a chemical vapor deposition (CVD) method to prepare a graphene-modified carbon felt electrode. The electrode material has the advantages of high electrical conductivity, large specific surface area, good vanadium ion catalytic performance, good stability, and high electrochemical catalytic activity.

Before preparing the graphene-modified carbon felt electrode, the carbon felt is treated as follows:

(1) soak the dried carbon felt in an acid solution, soak it at room temperature for a certain period of time, and then ultrasonically vibrate it for a certain period of time; wherein, the carbon felt drying temperature is 400 to 500 ° C, and the acid solution is one of sulfuric acid, nitric acid and hydrochloric acid. The concentration of the acid solution is 1-3 mol/L, the time for soaking the carbon felt in the acid solution is 12-18 hours, and the ultrasonic oscillation time is 0.5-1.5 hours;

(2) the carbon felt in step (1) is repeatedly cleaned with deionized water, and the cleaning times are 10 to 15 times;

(3) The cleaned carbon felt is subjected to drying treatment, and the drying temperature of the carbon felt is 80-120°C.

Hereinafter, the present invention will be further described with reference to the embodiments.

Example 1

In the present embodiment, the preparation method of graphene modified carbon felt, the steps are as follows:

(1) As shown in Figure 1(a), put a 20cm×20cm×5.5mm carbon felt on the graphite uniform heating sample stage at the bottom of the preparation chamber, and align the sample with the gas outlet direction at the top of the preparation chamber.

( ₂ ) open the H valve on the preparation chamber, clean for _2min , close the H valve; further, repeat the cleaning 4 times;

( ₃ ) open the CH valve on the preparation chamber, clean for 2min, and close the CH valve; further, repeat the cleaning ₄ times;

(4) Open the high vacuum valve on the preparation chamber, manually open the high vacuum unit, and evacuate for 5 minutes, so that the vacuum degree in the preparation chamber is 2.5 × 10 ^-2 ~ 3 × 10 ^-3 Pa; close the high vacuum valve, and manually close the high vacuum vacuum unit;

( ₅ ) open the H valve, adjust the gas flow rate to be 150～200sccm, heat the preparation chamber to a temperature of 1000±10°C, and the heating time is 100～120min;

(6) Keep the temperature at 1000±10℃ for 5min;

( ₇ ) in the holding time, open the CH valve, adjust the gas flow to be 20～30sccm, maintain the reaction time to be 5min, prepare graphene by chemical vapor deposition on the carbon felt, to form the graphene modified carbon felt;

(8) Close the CH ₄ valve, maintain the H ₂ flow at 150-200sccm, and cool with the furnace;

(9) After the temperature drops to room temperature, close the H valve, and the graphene _- modified carbon felt sample can be obtained.

In this embodiment, the graphene loading on the graphene-modified carbon felt is 0.3 wt %, and the graphene in the obtained modified carbon felt is evenly distributed, and no aggregation phenomenon occurs.

The relevant performance data of this embodiment are as follows:

The internal resistance of the carbon felt in the all-vanadium redox flow battery was measured at room temperature to be 0.65Ω·cm ² . The surface resistance of the composite electrode prepared in this ratio was lower than that of the commercial carbon felt (0.72Ω·cm ² ). The battery efficiency in VRB It is higher than the commercial carbon felt, adapts to the application requirements of VRB, and can promote the industrial development of all-vanadium redox flow batteries. But the deposition amount of graphene needs to be increased to further improve the battery performance.

Example 2

The difference from Example 1 is that:

1. In step (7), the time for chemical vapor deposition to prepare the graphene-modified carbon felt is 10 min.

2. The graphene-modified carbon felt was prepared by the other same steps as in Example 1, and the graphene loading on the graphene-modified carbon felt was 0.6 wt%.

As the graphene deposition time increases, under the same conditions, the graphene loading on the modified electrode increases, so the electrical conductivity of the composite electrode increases, which is higher than that of Example 1. Therefore, the internal resistance of the modified electrode in the all-vanadium redox flow battery measured at room temperature is 0.55Ω·cm ² , and the surface resistance of the composite electrode prepared in this ratio is lower than that of the original carbon felt (0.72Ω·cm ² ), VRB The energy efficiency of the cells in the carbon felt is higher than that of the original carbon felt, see Figure 2. As shown in Figure 1(b), compared with the VRB battery assembled with unmodified commercial carbon felt, the VRB battery with graphene-modified carbon felt has a high power density. Therefore, the composite carbon felt can be well adapted to the vanadium battery system, and its low cost and good battery performance can promote the large-scale commercial production of vanadium batteries.

Example 3

The difference from Example 1 is that:

1. In step (7), the time for chemical vapor deposition to prepare the graphene-modified carbon felt is 15 min.

2. The graphene-modified carbon felt was prepared by the other same steps as in Example 1, and the graphene loading on the graphene-modified carbon felt was 0.8 wt%.

Due to the increase of graphene deposition time, under the same conditions, the graphene loading on the modified electrode increases, so the conductivity of the composite electrode is improved, which is higher than that of Examples 1 and 2. However, due to the increase of graphene loading, agglomeration occurs on the surface of carbon felt carbon fibers, which affects the performance of the modified carbon felt in vanadium batteries. At the same time, due to the long deposition time, the preparation cost of carbon felt increases, which is not conducive to the industrial development of vanadium batteries.

Example 4

The difference from Example 1 is that:

1. In step (7), the time for chemical vapor deposition to prepare the graphene-modified carbon felt is 20 min.

2. The graphene-modified carbon felt was prepared by the other same steps as in Example 1, and the graphene loading on the graphene-modified carbon felt was 1wt%.

Due to the further increase of the graphene deposition time, under the same conditions, the graphene loading on the modified electrode increases, so the electrical conductivity of the composite electrode is improved, which is higher than that of Examples 1, 2 and 3. However, due to the increase of graphene loading, agglomeration occurs on the surface of carbon felt carbon fibers, which affects the performance of the modified carbon felt in vanadium batteries. At the same time, due to the long deposition time, the preparation cost of carbon felt increases, which is not conducive to the industrial development of vanadium batteries.

The results of the examples show that the present invention uses carbon felt as a raw material, adopts the steps in Example 2, and prepares a graphene-modified carbon felt electrode material by a chemical vapor deposition method. The graphene modified electrode prepared by the invention has the advantages of high electrical conductivity, large specific surface area, good vanadium ion catalytic performance, good stability, and high electrochemical catalytic activity. The preparation method of the invention is simple and easy to operate, environmentally friendly, low in cost of raw materials, easy for large-scale industrial production, and can be widely used in the commercial field of all-vanadium redox flow batteries.

Claims (8)

1. A preparation method of a macroscopic quantity graphene modified electrode material is characterized by comprising the following steps and process conditions:

(1) soaking the dried carbon felt in an acid solution at normal temperature for a certain time, and then ultrasonically oscillating for a certain time; wherein the carbon felt is soaked in the acid solution for 12-18 hours, and the ultrasonic oscillation time is 0.5-1.5 hours;

(2) reversely washing the carbon felt in the step (1) by using deionized water;

(3) drying the cleaned carbon felt;

(4) placing a 20cm × 20cm × 5.5.5 mm carbon felt on a graphite uniform heating sample table at the bottom in a preparation chamber, and aligning a sample to the direction of a gas outlet at the top in the preparation chamber;

(5) opening H on the preparation chamber₂Cleaning the valve for 1-3 min, and closing H₂A valve;

(6) opening CH on preparation Chamber₄Cleaning a valve for 1-3 min, and closing CH₄A valve;

(7) opening a high vacuum valve on the preparation chamber, manually opening a high vacuum unit, vacuumizing for 4-6 min to ensure that the vacuum degree in the preparation chamber is 2.5 × 10^-2～3×10^-3Pa; closing the high vacuum valve, and manually closing the high vacuum unit;

(8) is openedH₂A valve, adjusting the gas flow to be 150-200 sccm, heating the preparation chamber to 1000 +/-10 ℃ for 100-120 min;

(9) preserving the heat at 1000 +/-10 ℃ for 5-20 min;

(10) within the holding time, CH is opened₄A valve for adjusting the gas flow to 20-30 sccm and maintaining the reaction time to 5-20 min;

(11) close CH₄Valve, maintenance H₂Cooling along with the furnace with the flow rate of 150-200 sccm;

(12) after the temperature is reduced to room temperature, H is turned off₂And (5) a valve is used for obtaining a graphene modified carbon felt sample.

2. The preparation method of the macroscopic quantity graphene modified electrode material as claimed in claim 1, wherein in the step (1), the drying temperature of the carbon felt is 400-500 ℃.

3. The method for preparing the macroscopic quantity graphene modified electrode material according to claim 1, wherein in the step (1), the acid solution is one of sulfuric acid, nitric acid and hydrochloric acid, and the concentration of the acid solution is 1-3 mol/L.

4. The method for preparing the macroscopic quantity of graphene modified electrode material according to claim 1, wherein in the step (2), the number of times of cleaning is 10-15.

5. The preparation method of the macroscopic quantity graphene modified electrode material as claimed in claim 1, wherein in the step (3), the drying temperature of the carbon felt is 80-120 ℃.

6. The method for preparing the macroscopic quantity of graphene modified electrode material according to claim 1, wherein in the step (5), the number of times of cleaning is 3-5 times.

7. The method for preparing the macroscopic quantity of graphene modified electrode material according to claim 1, wherein in the step (6), the number of times of cleaning is 3-5 times.

8. The preparation method of the macroscopic quantity of graphene modified electrode material as claimed in claim 1, wherein the graphene loading amount in the graphene modified carbon felt is 0.3-1 wt%.

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