Preparation method of macroscopic quantity graphene modified electrode material
The technical field is as follows:
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 graphene modified electrode material suitable for all-vanadium redox flow batteries.
Background art:
with the rapid growth of global population and the rapid development of economy, the energy crisis is becoming more severe. The development of new energy is an effective way to solve the energy crisis. Renewable clean energy is currently a focus of scientific research and industrial development because of environmental friendliness and sustainability. Renewable energy power generation processes such as wind energy and solar energy show the disadvantages of discontinuity and instability. Therefore, the development of a large-scale energy storage technology with high efficiency, environmental protection, low cost, safety and reliability is urgently needed. The all-vanadium redox flow battery (VRB) has the advantages of independent power and energy, simple and flexible design, long cycle life, rapid charge and discharge, low operation cost and the like, so that the VRB is widely applied to large-scale energy storage equipment in the process of wind energy and solar power generation. Meanwhile, the VRB is a large-scale energy storage technology which is widely tried in the fields of power station energy storage, power grid peak regulation and the like in recent years. However, the commercial development of vanadium batteries is currently limited by high cost. Among them, the electrode material is a key factor determining the cost of the stack. An electrode material suitable for a vanadium battery has the advantages of excellent conductivity, high specific surface area, excellent electrochemical activity, low cost and the like. The traditional metal material electrode has poor electrochemical reversibility and is easy to be passivated by acid electrolyte; although noble metals such as platinum and iridium have the advantages of high electrochemical activity, good catalytic performance, good chemical stability and the like, the materials are expensive, and the large-scale application of the materials in vanadium batteries is restricted. At present, the most widely used electrode materials for vanadium batteries are carbon materials, such as: graphite felt, graphite, carbon cloth, carbon fiber and the like. However, the carbon material has the problems of low conductivity, poor electrochemical activity, poor battery performance and the like in the direct application process. In view of this, modification treatment of such carbon-based materials is necessary to improve the electrical conductivity and electrochemical activity of the electrode. To date, there has not been a suitable method to address these critical issues.
The invention content is as follows:
in order to overcome the defects of the prior art, the invention aims to provide a preparation method of a macroscopic quantity graphene modified electrode material suitable for a vanadium battery, and the preparation method is used for solving the problems of poor conductivity, low chemical activity, low specific surface area, poor stability, poor performance in VRB, high VRB cost and the like of a carbon felt in the prior art. The composite carbon felt with low cost and high performance can be obtained by adopting the method, and has the advantages of high conductivity, high specific surface area, high electrochemical activity, good catalytic performance to vanadium ions, good stability, good performance in VRB battery application and the like.
The specific technical scheme of the invention is as follows:
a preparation method of a macroscopic quantity graphene modified electrode material comprises 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) opening H2A 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.
According to the preparation method of the macroscopic quantity graphene modified electrode material, in the step (1), the drying treatment temperature of the carbon felt is 400-500 ℃.
In the preparation method of the macroscopic quantity graphene modified electrode material, 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.
According to the preparation method of the macroscopic quantity graphene modified electrode material, in the step (2), the cleaning times are 10-15.
According to the preparation method of the macroscopic quantity graphene modified electrode material, in the step (3), the drying temperature of the carbon felt is 80-120 ℃.
According to the preparation method of the macroscopic quantity graphene modified electrode material, in the step (5), the cleaning times are 3-5 times.
According to the preparation method of the macroscopic quantity graphene modified electrode material, in the step (6), the cleaning times are 3-5 times.
According to the preparation method of the macroscopic quantity graphene modified electrode material, the graphene loading amount in the graphene modified carbon felt is 0.3-1 wt%.
The design idea of the invention is as follows: the invention uses CH4As carbon source, in H2Reduction of (2) and reaction of CH at elevated temperature4And cracking to obtain the graphene. Further, the prepared graphene is uniformly coated on the carbon felt, so that the graphene carbon felt is obtained.
Compared with the prior art, the invention has the following remarkable advantages and beneficial effects:
1. the graphene modified carbon felt electrode material is prepared by taking a commercial carbon felt as a raw material and adopting a chemical vapor deposition method, and has the advantages of high conductivity, large specific surface area, good vanadium ion catalytic performance, good stability, high electrochemical catalytic activity and the like.
2. The method for preparing the graphene modified carbon felt has the advantages of easily available raw materials, low cost, simple and easy operation and suitability for large-scale development.
3. The whole preparation process of the invention has the industrial and practical characteristics of low equipment price, low and easily obtained raw material cost, simple and convenient operation process and the like, and is beneficial to the large-scale production of the electrode material for VRB commercialization.
In a word, the graphene modified carbon felt composite electrode is prepared by taking the commercial carbon felt as a raw material and adopting a vapor deposition method, so that the conductivity, the specific surface area, the electrochemical activity, the stability and the electrochemical catalytic performance of the carbon felt are improved. In contrast to VRB cells assembled with unmodified commercial carbon felt, VRB cells employing graphene-modified carbon felt had high power density (fig. 1), as well as high efficiency, superior rate performance and cycling performance (fig. 2). And uniformly depositing the graphene with high specific surface area and high conductivity on the surface of the commercial carbon felt by using a vapor deposition method to prepare the high-performance graphene modified carbon felt composite electrode. The method has the advantages of low cost and easy obtainment of raw materials, simple and convenient operation, suitability for large-scale industrial development, and hopeful preparation of a commercial electrode material for the vanadium battery with low cost and high performance.
Description of the drawings:
FIG. 1 is an area of the obtained graphene modified carbon felt, wherein (a) is a physical graph of the graphene carbon felt with a thickness of 20cm × 20cm × 5.5.5 mm, and (b) is a cyclic voltammogram, Voltage (V) is represented by Voltage on the abscissa, and Current density is represented by Current density (mA/cm) on the ordinate2) The Pure CF stands for the original carbon felt, and the G-CF stands for the 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 represents the number of cycles, the ordinate represents the battery Efficiency (%), EE: prime CF represents the energy Efficiency of the original carbon felt, VE: prime CF represents the voltage Efficiency of the original carbon felt, EE: G/CF represents the energy Efficiency of the graphene carbon felt, and VE: G/CF represents the voltage Efficiency of the graphene carbon felt.
The specific implementation mode is as follows:
in the specific implementation process, the graphene modified carbon felt electrode is prepared by taking a commercial carbon felt as a raw material and adopting a Chemical Vapor Deposition (CVD) method. The electrode material has the advantages of high conductivity, large specific surface area, good vanadium ion catalytic performance, good stability, high electrochemical catalytic activity and the like.
Before preparing the graphene modified carbon felt electrode, the carbon felt is treated as follows:
(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 drying temperature of the carbon felt is 400-500 ℃, 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 soaking time of the carbon felt in the acid solution is 12-18 hours, and the ultrasonic oscillating time is 0.5-1.5 hours;
(2) repeatedly washing the carbon felt in the step (1) with deionized water, wherein the washing times are 10-15 times;
(3) and drying the cleaned carbon felt at the temperature of 80-120 ℃.
The present invention will be further described with reference to the following examples.
Example 1
In this embodiment, the preparation method of the graphene modified carbon felt includes the following steps:
(1) as shown in FIG. 1(a), a 20cm × 20cm × 5.5.5 mm carbon felt was placed on a graphite homothermal sample stage at the bottom of the preparation chamber and the sample was aimed in the direction of the gas outlet at the top of the preparation chamber.
(2) Opening H on the preparation chamber2Valve, cleaning for 2min, closing H2A valve; further, the washing was repeated 4 times;
(3) opening CH on preparation Chamber4Valve, cleaning for 2min, closing CH4A valve; further, the washing was repeated 4 times;
(4) opening the high vacuum valve on the preparation chamber, manually opening the high vacuum unit, and vacuumizing for 5min to make the vacuum degree in the preparation chamber 2.5 × 10-2~3×10-3Pa; closing the high vacuum valve, and manually closing the high vacuum unit;
(5) opening H2A valve, adjusting the gas flow to be 150-200 sccm, heating the preparation chamber to 1000 +/-10 ℃ for 100-120 min;
(6) keeping the temperature at 1000 +/-10 ℃ for 5 min;
(7) within the holding time, CH is opened4The valve is used for adjusting the gas flow to be 20-30 sccm, maintaining the reaction time to be 5min, and preparing graphene on the carbon felt through chemical vapor deposition to form a graphene modified carbon felt;
(8) close CH4Valve, maintenance H2Cooling along with the furnace with the flow rate of 150-200 sccm;
(9) after the temperature is reduced to room temperature, H is turned off2And (5) a valve is used for obtaining the graphene modified carbon felt sample.
In this embodiment, the graphene loading amount on the graphene modified carbon felt is 0.3 wt%, and the obtained modified carbon felt has uniform graphene distribution and no aggregation phenomenon.
The relevant performance data for this example is as follows:
the internal resistance of the carbon felt in the all-vanadium redox flow battery measured at room temperature is 0.65 omega cm2The surface resistance of the composite electrode prepared by the proportion is smaller than that of a commercial carbon felt (0.72 omega cm)2) The battery efficiency in the VRB is higher than that of a commercial carbon felt, the VRB is suitable for the application requirement of the VRB, and the industrial development of the all-vanadium redox flow battery can be promoted. However, the deposition amount of graphene needs to be increased to further improve the battery performance.
Example 2
The difference from the embodiment 1 is that:
1. in the step (7), the time for preparing the graphene modified carbon felt by chemical vapor deposition is 10 min.
2. The same other steps as in example 1 were used to prepare a graphene modified carbon felt, with a graphene loading of 0.6 wt% on the graphene modified carbon felt.
Due to the fact that the deposition time of the graphene is increased, under the same condition, the graphene loading amount on the modified electrode is increased, and therefore the graphene is used for preparing the electrodeThe conductivity of the composite electrode is improved, and is higher than that of the composite electrode in example 1. Therefore, the internal resistance of the modified electrode in the all-vanadium redox flow battery was measured to be 0.55 Ω · cm at room temperature2The surface resistance of the composite electrode prepared by the proportion is lower than that of the original carbon felt (0.72 omega cm)2) The cell energy efficiency in VRB is higher than that of the raw carbon felt, see fig. 2. As shown in fig. 1(b), VRB cells employing graphene modified carbon felt have a high power density compared to VRB cells assembled with unmodified commercial carbon felt. Therefore, the composite carbon felt can be well adapted to a vanadium battery system, the cost is low, and the large-scale commercial production of the vanadium battery can be promoted due to the good battery performance.
Example 3
The difference from the embodiment 1 is that:
1. in the step (7), the time for preparing the graphene modified carbon felt by chemical vapor deposition is 15 min.
2. The same other steps as in example 1 were used to prepare a graphene modified carbon felt, with a graphene loading of 0.8 wt% on the graphene modified carbon felt.
Due to the fact that the deposition time of graphene is increased, under the same conditions, the graphene loading amount on the modified electrode is increased, and therefore the conductivity of the composite electrode is improved and is higher than those of the composite electrode in examples 1 and 2. However, due to the fact that the loading amount of graphene is increased, agglomeration phenomenon occurs on the surface of carbon fiber of the carbon felt, and the performance of the modified carbon felt in the vanadium battery is influenced. Meanwhile, the deposition time is long, so that the preparation cost of the carbon felt is increased, and the industrial development of the vanadium battery is not facilitated.
Example 4
The difference from the embodiment 1 is that:
1. in the step (7), the time for preparing the graphene modified carbon felt by chemical vapor deposition is 20 min.
2. The same other steps as in example 1 were used to prepare a graphene modified carbon felt, with a graphene loading of 1 wt% on the graphene modified carbon felt.
Due to the fact that the deposition time of the graphene is further increased, under the same conditions, the graphene loading amount on the modified electrode is increased, and therefore the conductivity of the composite electrode is improved and is higher than those of the composite electrode in examples 1, 2 and 3. However, due to the fact that the loading amount of graphene is increased, agglomeration phenomenon occurs on the surface of carbon fiber of the carbon felt, and the performance of the modified carbon felt in the vanadium battery is influenced. Meanwhile, the deposition time is long, so that the preparation cost of the carbon felt is increased, and the industrial development of the vanadium battery is not facilitated.
The example results show that the graphene modified carbon felt electrode material is prepared by using the carbon felt as a raw material and adopting the steps in the example 2 and a chemical vapor deposition method. The graphene modified electrode prepared by the method has the advantages of high conductivity, large specific surface area, good vanadium ion catalytic performance, good stability, high electrochemical catalytic activity and the like. The preparation method disclosed by the invention is simple and easy to operate, environment-friendly, low in raw material cost, easy for large-scale industrial production, and widely applicable to the commercial field of all-vanadium redox flow batteries.