CN106830223A - A kind of activated carbon electrodes and its preparation method and application - Google Patents

Abstract

The invention discloses an activated carbon electrode and its preparation method and application. According to the weight parts, the raw materials include 30-90 parts of activated carbon of 20-300 mesh, 5-40 parts of conductive agent, 5-50 parts of clay, Composed of 5-80 parts of carbonizable organic binder and 5-30 parts of deionized water. Including: mixing activated carbon, conductive agent and clay evenly, then adding carbonizable organic binder and deionized water and mixing evenly to prepare a slurry; coating the active material slurry evenly on the electrode substrate, and placing it at 60°C‑ Dry at 160°C for 0.5h-3h; place the preliminarily dried electrode in a vacuum or nitrogen-protected atmosphere furnace, and calcinate at 500°C-1000°C for 0.5h-3h to obtain a coated electrode plate. The invention improves the conductivity and water resistance of the activated carbon electrode, has extremely high practical value in capacitive desalination, and can significantly improve the conductivity and water resistance of the activated carbon electrode.

Description

A kind of activated carbon electrode and its preparation method and application

technical field

The invention belongs to the technical field of electrochemistry, and in particular relates to an activated carbon electrode and its preparation method and application.

Background technique

The preparation and application of activated carbon electrodes is the core technology in capacitive desalination. High-efficiency activated carbon electrodes should have the characteristics of large specific surface area, abundant mesopores and high conductivity. Activated carbon electrodes used in capacitive desalination generally need to be soaked in salt solution for a long time, so they must also have good water resistance to ensure long-term use without the activated carbon falling off the current collector. In addition, the high electrical resistance of activated carbon particles limits their application in electrochemical capacitive desalination. Therefore, for the preparation of activated carbon electrodes for electrochemical capacitive desalination applications, efforts should be made to improve the coating of activated carbon particles and the electrode preparation process to improve the conductivity and water resistance of activated carbon electrodes. At present, the commonly used binders for preparing activated carbon electrodes include organic binders and inorganic binders. Organic binders include polytetrafluoroethylene, polytetrafluoroethylene, epoxy resin, phenolic resin and modified starch. However, the use of organic binders will block the micropores and mesopores of activated carbon particles, reducing the pore utilization of activated carbon, thereby reducing the desalination efficiency of activated carbon electrodes; organic binders will also increase the internal resistance of activated carbon electrodes, Reduce the electrical energy efficiency of the electrode; especially, when using organic binders, the amount of activated carbon particle coating is generally on the milligram level, and the loading is too low to reach the actual use standard of the applied electrode. During the stirring process of preparing the slurry, the organic binder will enter the micropores of the activated carbon particles, and after solidification, the micropores will be blocked and cannot be used; most of the organic binders are not conductive. The resistance is very large, which will naturally increase the internal resistance of the motor; when the organic binder is used to bond the activated carbon particles, the gap between the activated carbon particles and the particles is large, and a small amount of organic binder cannot make it well combined. Increasing the organic binder will cause the performance of activated carbon particles to decline rapidly, and the large particles of activated carbon are easy to fall off from the surface. Inorganic binders include sodium, potassium water glass, activated kaolin, clay, etc. Inorganic binders generally have a large resistance, which will increase the internal resistance of the activated carbon electrode and significantly reduce the electrochemical activity of the electrode; at the same time, it is difficult for the inorganic binder to bond the activated carbon particles to the current collector substrate well; the inorganic binder The agent cannot penetrate into the surface of carbon paper or carbon cloth, and it is easy to decompose and dissolve in water after being exposed to water, resulting in poor bonding. The organic binder has good wettability with carbon paper or carbon cloth, and its water resistance is far better than that of the inorganic binder, so it can well bond activated carbon particles and current collectors. Moreover, the water resistance of the inorganic binder is very poor, causing the activated carbon to fall off the substrate severely when it encounters water.

To sum up, the binders currently used in the preparation of activated carbon electrodes have the defects of poor electrical conductivity and poor water resistance.

Contents of the invention

The object of the present invention is to provide an activated carbon electrode and its preparation method and application, aiming to solve the problems of poor electrical conductivity and poor water resistance of the binder used in the preparation of activated carbon electrodes.

The present invention is achieved in this way, a kind of activated carbon electrode, described activated carbon electrode is made of 30 parts-90 parts of activated carbon of 20 mesh-300 mesh number, 5 parts-40 parts of conductive agent, 5 parts-50 parts of clay according to the raw material of weight part , 5-80 parts of carbonizable organic binder and 5-30 parts of deionized water.

Further, the conductive agent is one or more of acetylene black, graphite powder, carbon nanotubes, and carbon fibers.

Further, the clay is one or more of activated kaolin, diatomaceous earth, medical stone, and porous alumina.

Further, the carbonizable organic binder is one or more of modified starch, polytetrafluoroethylene, polytetrafluoroethylene, epoxy resin, and phenolic resin.

Another object of the present invention is to provide a kind of preparation method of described activated carbon electrode, the preparation method of described activated carbon electrode comprises the following steps:

Step 1: Mix activated carbon, conductive agent and clay uniformly, then add carbonizable organic binder and deionized water and mix uniformly to prepare slurry;

Step 2, uniformly coating the active material slurry on the electrode substrate, and drying at 60°C-160°C for 0.5h-3h;

Step 3: Place the preliminarily dried electrode in a vacuum or nitrogen-protected atmosphere furnace, and calcinate at 500°C-1000°C for 0.5h-3h to obtain a coated electrode plate.

Further, the electrode substrate is: carbon paper or carbon cloth.

Another object of the present invention is to provide a capacitive desalination device prepared from the activated carbon electrode.

The activated carbon electrode provided by the invention and its preparation method and application improve the conductivity and water resistance of the activated carbon electrode, and the prepared activated carbon electrode has extremely high practical value in capacitive desalination. The activated carbon electrode of the present invention is applied in the CDI desalination technology, and the energy consumption is only one-fifth of that of the RO technology, taking 500ppm TDS as an example. Based on the 5-year equipment life, the annual operating cost of a set of 6 tons/hour processing capacity equipment is about 20,000 US dollars, which is more than 50% lower than the operating cost of RO technology of the same scale. The present invention can significantly improve the conductivity and water resistance of the activated carbon electrode while ensuring the high load capacity of the activated carbon electrode, and the prepared activated carbon electrode has excellent performance in electrochemical ^desalination ; In sodium chloride solution, the specific capacity of capacitive desalination can reach 14.6 mg·g ^-1 . Using a mixed binder, the conductivity of the activated carbon electrode after high-temperature carbonization is significantly improved, which increases the utilization rate of the current; the organic bond cannot bind the large particles of activated carbon well, but it can make the activated carbon particles and the current collector very well. collection; activated carbon particles still have good cohesion, which also proves from the other hand that the above-mentioned inorganic binders cannot bond activated carbon particles and current collectors well, but can make activated carbon large particles have good bonding performance between them.

The invention adopts the method of combining the inorganic binder and the organic binder, while ensuring the coating amount of the activated carbon particles, the activated carbon electrode has good conductivity, and the combination of the activated carbon particles and the electrode base material is stable, and has a good The water resistance of the activated carbon electrode further improves the electrochemical performance of the activated carbon electrode and greatly reduces the electrode manufacturing cost in practical applications; the filler contains a certain proportion of carbonizable organic binder, which is calcined at high temperature under vacuum or nitrogen protection, not only can be opened The mesopores of the more active particles and can carbonize the organic binder. The organic binder after carbonization has good conductivity, and makes the activated carbon particles and the electrode substrate tightly combined, so that the entire electrode has good conductivity; the filler contains a certain proportion of inorganic binder, so that the activated carbon The combination of particles is not very tight, so that the porosity of the electrode surface is properly distributed, so that the salt solution can better enter the electrode surface, and the utilization rate of activated carbon particles is improved. In the comparison test, the three electrodes A, B, and C The amount of activated carbon is the same, but the desalination effect of electrode A is much better than that of electrodes B and C, which means that the utilization rate of activated carbon particles in electrode A is higher than that of electrodes B and C; further improving the efficiency of activated carbon electrodes electrochemical performance. And the proportion of the added inorganic binder can be adjusted to adjust the pores on the surface of the activated carbon electrode. From the mercury intrusion data graph in the comparison test, it can be seen that the pore size distribution of the A electrode at 45nm is significantly higher than that of the B and C electrodes, and the micropores mainly play a role in capacitive desalination, and the conductivity of the A electrode is much higher than that of the electrodes B and C. Far better than B and C electrodes, and the electron transmission speed is fast, which leads to the desalination efficiency of A electrode is better than that of B and C electrodes. The pore size distribution at 100 microns should be the pores between the activated carbon particles. It can be found that the pore distribution of the A electrode is more uniform and reasonable than that of the B and C electrodes, which is more conducive to the uniform distribution of the liquid and increases the utilization of electrons and micropores.

The method of the invention has simple equipment and simple operation, all processes can be automated, the process can be simplified, and the time and efficiency of electrode preparation can be improved.

Description of drawings

Fig. 1 is a flow chart of the preparation method of the activated carbon electrode provided by the embodiment of the present invention.

Fig. 2 is a schematic diagram of the desalination performance of the electrodes prepared in Examples 1 and 2 provided in the examples of the present invention in a 2000 μS·cm ^-1 sodium chloride solution.

Fig. 3 is a schematic diagram of cyclic voltammetry with a scan rate of 1 mV/s in 0.5M NaCl solution for three electrodes provided by the embodiment of the present invention.

Fig. 4 is a schematic diagram of impedance diagrams of three electrodes provided in an embodiment of the present invention in a 0.5M NaCl solution.

Fig. 5 is a schematic diagram of the change of conductivity with time in the NaCl solution provided by the embodiment of the present invention.

Fig. 6 is a schematic diagram of the electrode desalination cycle performance of three electrodes provided in the embodiment of the present invention in a sodium chloride solution.

Fig. 7 is a diagram of mercury intrusion data of electrodes A, B, and C provided by the embodiment of the present invention.

Fig. 8 is a diagram of Bet data of electrodes A, B, and C provided by the embodiment of the present invention.

Fig. 9 shows that electrodes A, B, and C provided by the embodiment of the present invention were soaked in NaCl solution for one month respectively.

Fig. 10 shows the resistance values at 1, 2, 3, and 4 cm on the surface of electrodes A, B, and C provided by the embodiment of the present invention.

Fig. 11 is a comparison of the bending strength of electrodes A, B, and C provided by the embodiment of the present invention.

Fig. 12 is a cross-sectional and surface SEM image of electrodes A, B, and C provided by an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The application principle of the present invention will be described in detail below in conjunction with the accompanying drawings.

The activated carbon electrode provided by the embodiments of the present invention consists of 30-90 parts of activated carbon of 20 mesh-300 mesh, 5-40 parts of conductive agent, 5-50 parts of clay, and 5 parts of carbonizable organic binder according to the raw materials in parts by weight. 1-80 parts and 5-30 parts of deionized water.

As shown in Figure 1, the preparation method of the activated carbon electrode provided by the embodiment of the present invention comprises the following steps:

S101: Mix activated carbon, conductive agent and clay uniformly, then add carbonizable organic binder and deionized water and mix uniformly to prepare slurry;

S102: uniformly coating the active material slurry on the electrode substrate, and drying at 60°C-160°C for 0.5h-3h;

S103: Place the preliminarily dried electrode in a vacuum or nitrogen-protected atmosphere furnace, and calcinate at 500°C-1000°C for 0.5h-3h to obtain a coated electrode plate.

The electrode base material is: carbon paper, carbon cloth.

The conductive agent is one or more of acetylene black, graphite powder, carbon nanotube, carbon fiber and the like.

The clay is one or more of activated kaolin, diatomaceous earth, medical stone, porous alumina and the like.

The carbonizable organic binder is one or more of modified starch, polytetrafluoroethylene, polytetrafluoroethylene, epoxy resin, phenolic resin and the like.

The application principle of the present invention will be further described below in combination with specific embodiments.

Example 1:

An activated carbon electrode with good conductivity and water resistance, the raw materials in parts by weight include: 80 parts of activated carbon of 20-300 mesh, 5 parts of conductive agent, 5 parts of clay, 5 parts of carbonizable organic binder, deionized 5 parts of water.

A kind of method for activated carbon electrode preparation, concrete steps are as follows:

Step 1: Mix activated carbon, conductive agent and clay uniformly, then add carbonizable organic binder and deionized water and mix uniformly to prepare slurry.

Step 2, uniformly coating the active material slurry on the electrode substrate, and drying at 100° C. for 1 hour.

Step 3: Place the preliminarily dried electrode in a vacuum or nitrogen-protected atmosphere furnace, and calcinate at 600° C. for 3 hours to obtain a coated electrode plate.

Example 2:

An activated carbon electrode with good conductivity and water resistance, the raw materials in parts by weight include: 60 parts of activated carbon of 20-300 mesh, 10 parts of conductive agent, 5 parts of clay, 20 parts of carbonizable organic binder, deionized 5 parts of water.

A kind of method for activated carbon electrode preparation, concrete steps are as follows:

Step 1: Mix activated carbon, conductive agent and clay uniformly, then add carbonizable organic binder and deionized water and mix uniformly to prepare slurry.

Step 2, uniformly coating the active material slurry on the electrode substrate, and drying at 150° C. for 0.5 hour.

Step 3. Place the preliminarily dried electrode in a vacuum or nitrogen-protected atmosphere furnace, and calcinate at 900° C. for 2 hours to obtain a coated electrode plate.

A voltage of 1.5V was applied to both ends of the activated carbon electrodes prepared in Example 1 and Example 2, the adsorption time was 60 minutes, the electrode regeneration time was 30 minutes, and then the cycle was continued. It can be seen from the figure that both electrodes have good electrosorption properties, and after ¹ hour of electrosorption process, the conductivity of the NaCl solution decreased from 2000 μS cm to 1300 ^μS cm with 1000 μS·cm ^-1 , according to the formula, it can be calculated that the electrostatic desalination capacity of the electrode prepared in Example 1 is 10 mg/g, while that of the electrode prepared in Example 2 is 14.5 mg/g. The present invention adopts cheap raw materials and a simple and fast process to prepare an activated carbon electrode with high desalination performance. Applying this activated carbon electrode to sewage treatment, seawater desalination, industrial water softening, etc. will greatly reduce the cost of sewage treatment , has great commercial value.

The application effects of the present invention will be described in detail below in conjunction with comparative experiments.

In comparative experiments, three different activated carbon electrodes were prepared by using mixed binders, organic binders and inorganic binders, using the same preparation process. These three electrodes are respectively named as A electrode, B electrode and C electrode.

First, the bending strength of the three electrodes was compared, and it was found that the electrode prepared by using the mixed binder had good bending strength, which could be bent 360° without the activated carbon particles falling off from the surface of the graphite paper; When the electrode of the agent is bent to 270°, the activated carbon particles on the surface of the graphite paper begin to fall off; while the electrode using the inorganic binder is slightly bent, the activated carbon particles will break into pieces and fall from the surface of the graphite paper, which also shows that Inorganic binders cannot combine activated carbon particles with graphite paper substrates well. In order to further verify the superiority of the activated carbon electrodes prepared with mixed binders, the electrochemical analysis of the three electrodes was also carried out. From the cyclic voltammogram 3, it can be found that there is no redox peak in the curve, so it can be concluded that there is no electron gain and loss and transfer of materials on the surfaces of the three pairs of electrodes, only the adsorption and desorption of ions, that is, the capacitance is all from Electric double layer due to Coulomb interaction rather than faradaic capacitance. It can also be observed that the area of the cyclic voltammetry curve of the A electrode is larger than that of the B electrode and the C electrode, and it can be concluded that the capacitance of the A electrode is larger. On this basis, the impedance of these three kinds of electrodes was also analyzed. It can also be seen from the impedance diagram 4 that the A electrode has a smaller electrochemical impedance, indicating that the electron transmission speed on the surface of the A electrode is faster than that of the B electrode and the C electrode, which is of great significance in terms of electrostatic desalination performance .

In order to further verify the desalination performance of electrode A, as shown in Figure 5, an electrosorption desalination test was carried out in a sodium chloride solution with a conductivity of 2000 μS·cm ^-1 . The voltages across the three electrodes were all 1.5V, and the electrosorption time was 120 minutes. It can be found that in the early stage of adsorption of electrode A, the conductivity of the sodium chloride solution drops faster than that of electrodes B and C, and after 100 minutes, electrodes B and C have been saturated, and electrode A can continue to adsorb. After using electrode A to desalinate the sodium chloride solution, the conductivity drops to 850 μS·cm ^-1 , which is much lower than the final conductivity of electrodes B and C. This shows that the A electrode has a large specific surface area and a reasonable pore size distribution, forming a large number of effective ion channels inside the electrode. While ensuring the smooth passage of ions, it also increases the amount of ion adsorption, thereby greatly improving Electrode deionization performance of the electrode.

In order to simulate the actual electrostatic desalination process, as shown in Figure 6, three kinds of electrodes were tested for the electrolytic desalination cycle process respectively. The salt solution is a sodium chloride solution with a conductivity of 2000μS·cm ^-1 , the voltage across the electrodes is 1.5V, the adsorption time of the electrode desalination is 60 minutes, and the regeneration time of the electrodes is 30 minutes. It can be seen from the figure that the performance of electrode A is much better than that of the other two electrodes in the process of electrostatic desalination adsorption, and the ion release rate is also faster than the other two electrodes in the process of electrode regeneration. The performance of the desalination process and electrode regeneration process of the B electrode is poor, because the organic binder blocks the pores of the activated carbon, resulting in a significant drop in desalination performance. It can be clearly observed that the ions cannot be completely released during electrode regeneration, because the use of inorganic binders blocks the effective channels of ions, which hinders the adsorption and release of ions at the same time. During the process, some ions cannot be released, which will block the pores of the activated carbon and further reduce the desalination performance.

As shown in Figure 7, in the comparison test, the amount of activated carbon in the three electrodes A, B, and C is the same, and the desalination effect of the A electrode is much better than that of the B and C electrodes, which shows that the activated carbon of the A electrode The utilization rate of particles is higher than that of B and C electrodes; the electrochemical performance of activated carbon electrodes is further improved. And the proportion of the added inorganic binder can be adjusted to adjust the pores on the surface of the activated carbon electrode. From the mercury intrusion data graph in the comparison test, it can be seen that the pore size distribution of the A electrode at 45nm is significantly higher than that of the B and C electrodes, and the micropores mainly play a role in capacitive desalination, and the conductivity of the A electrode is much higher than that of the electrodes B and C. Far better than B and C electrodes, and the electron transmission speed is fast, which leads to the desalination efficiency of A electrode is better than that of B and C electrodes. The pore size distribution at 100 microns should be the pores between the activated carbon particles. It can be found that the pore distribution of the A electrode is more uniform and reasonable than that of the B and C electrodes, which is more conducive to the uniform distribution of the liquid and increases the utilization of electrons and micropores.

From the cross-sectional SEM images of electrodes A, B, and C, it can be concluded that the activated carbon particles of the C electrode with an inorganic binder have large pores on the surface of the current collector, and there is no good bonding; while the activated carbon particles of the A and B electrodes The particles are in good contact with the current collector and have good cohesion. From the surface SEM images of each electrode, it can be seen that the pore distribution on the surface of electrode A is more uniform, which is conducive to the uniform distribution of liquid and electron transmission, thus enhancing its electrostatic desalination performance.

As shown in Figure 8, the Bet data diagrams of electrodes A, B, and C are based on the mercury intrusion data, and the micropores of the activated carbon on electrodes A, B, and C are measured, that is, the Bet data. It can be clearly seen from the figure that the micropores of the activated carbon on the three electrodes are mainly distributed at about 1.5nm, and the number of micropores of the A electrode is much larger than that of the B and C electrodes. During the capacitive desalination process, the main Micropores play the role of adsorption, so it can be seen that the capacitive desalination performance of electrode A is much better than that of electrodes B and C, which is also proved from the actual capacitive desalination process.

As shown in Figure 9, the changes on the surface of electrodes A, B, and C were soaked in NaCl solution for one month. In order to verify the water resistance of the prepared electrodes, three electrodes A, B, and C were soaked in NaCl solution for one month. Month, observe the changes in the electrode surface. It can be seen from the figure that after soaking for a month, the electrode surface of A electrode has no obvious change, indicating that it has good water resistance and mechanical strength; while a large number of activated carbon particles have fallen off the surface of B electrode, but the gap between the activated carbon and the current collector It still has good bonding performance, which also proves the theory proposed above. Organic bonding cannot bind large particles of activated carbon very well, but it can make activated carbon particles and current collectors gather well; activated carbon on the surface of C electrode forms The flakes fall off from the surface of the current collector, but the activated carbon particles still have good cohesion, which also proves from the other hand that the inorganic binder cannot bond the activated carbon particles and the current collector well. , but it can make the activated carbon particles have good bonding performance.

As shown in Figure 10, the resistances at 1, 2, 3, and 4 cm on the surface of electrodes A, B, and C can be seen from the figure that the resistance of electrode A is much smaller than that of electrodes B and C, and the resistance of the three electrodes The resistance of the electrode surface does not increase linearly with the increase of the distance. This is because the resistance of the current collector is smaller than that of the activated carbon particles, and the current will flow from the positive electrode of the power supply through the activated carbon layer to the negative electrode of the power supply. The actual measured resistance is the resistance of the activated carbon layer, so the resistance of the electrode surface is only related to the thickness and internal structure of the activated carbon layer. It is also proved that the conductivity of the activated carbon electrode after high-temperature carbonization is significantly improved by using the mixed binder, and the utilization rate of the current is increased.

As shown in Figure 11, the bending strength of A, B, and C electrodes is compared.

As shown in Figure 12, the cross-section and surface SEM images of electrodes A, B, and C.

To sum up, the mixed use of inorganic binder and organic binder makes the activated carbon particles and current collectors, activated carbon particles and activated carbon particles have a good bonding effect, which ensures the mechanical strength and bonding of activated carbon electrodes. strength. After high-temperature calcination, the interior of the electrode is relatively fluffy, the specific surface area is increased, and the pore size distribution is reasonable, and a large number of effective ion channels are formed inside the electrode to ensure the smooth passage of ions, thereby greatly improving the removal of activated carbon electrodes. salt properties. Moreover, the raw materials used in the present invention are cheap and easy to obtain, the processing technology is simple and quick, has great potential to be applied to actual production, and has huge commercial value.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (7)

1. a kind of activated carbon electrodes, it is characterised in that the activated carbon electrodes are according to the raw material of weight portion by the mesh number of 20 mesh -300 30 parts -90 parts of activated carbon, 5 parts -40 parts of conductive agent, 5 parts -50 parts of clay, can be carbonized 5 parts -80 parts of organic binder bond and go from 5 parts of -30 parts of compositions of sub- water.

2. activated carbon electrodes as claimed in claim 1, it is characterised in that the conductive agent is：Acetylene black, graphite powder, carbon are received One or more in mitron, carbon fiber.

3. activated carbon electrodes as claimed in claim 1, it is characterised in that the clay is alukalin, diatomite, wheat meal One or more in stone, Woelm Alumina.

4. activated carbon electrodes as claimed in claim 1, it is characterised in that it is described be carbonized organic binder bond for modified starch, One or more in polytetrafluoroethylene (PTFE), segregation tetrafluoroethene, epoxy resin, phenolic resin.

5. a kind of preparation method of activated carbon electrodes as claimed in claim 1, it is characterised in that the preparation of the activated carbon electrodes Method is comprised the following steps：

Step one, activated carbon, conductive agent are well mixed with clay, then the organic binder bond that can be carbonized is added with deionized water and mixed Conjunction uniformly prepares slurry；

Step 2, active material slurry is coated uniformly on electrode base material, and 0.5h-3h is dried at being placed in 60 DEG C -160 DEG C；

Step 3, the electrode of preliminarily dried is placed in vacuumize or nitrogen protection atmosphere furnace in, forged at 500 DEG C -1000 DEG C 0.5h-3h is burnt, that is, obtains coated battery lead plate.

6. the preparation method of activated carbon electrodes as claimed in claim 5, it is characterised in that the electrode base material is：Carbon paper or Carbon cloth.

7. it is a kind of as described in claim 1 activated carbon electrodes prepare electric capacity demineralizer.