CN105836855A - Preparation method and application of graphene gas diffusion electrode - Google Patents

Abstract

The invention relates to the technical field of electrode material preparation, in particular to a preparation method and application of a graphene gas diffusion electrode. The specific preparation process is as follows: mix flake graphite, NaNO ₃ and concentrated sulfuric acid in an ice bath, and react slowly with KMnO ₄ , then add an appropriate amount of 30% H ₂ O ₂ to fully react, filter, and wash until neutral dry. The product is ultrasonically obtained in an aqueous solution to obtain a dispersion, and the pH is adjusted. After centrifugation, the upper stable liquid is taken, and an appropriate amount of hydrazine hydrate is added to obtain a graphene dispersion. The dispersion liquid is evenly mixed with graphite powder, ethanol, and polytetrafluoroethylene (PTFE) emulsion. When the water bath is kept at a constant temperature until the mixture is a thick paste, it is attached to a stainless steel mesh and pressed to form a graphene gas diffusion electrode. The invention has stronger oxidation ability in the electro-Fenton system, and can be used in the treatment of various types of wastewater containing organic pollutants.

Description

A kind of preparation method and application of graphene gas diffusion electrode

technical field

The invention relates to the technical field of sewage treatment, in particular to a method for preparing a graphene gas diffusion electrode and a method for using the same.

Background technique

As a kind of advanced oxidation technology, the electro-Fenton method has attracted widespread attention in the field of environmental protection because of its thorough degradation, high efficiency, simple operation, and low time and energy consumption. It is widely used in the treatment of wastewater containing organic pollutants. middle. In order to improve the catalytic activity of the cathode for the two-electron reduction reaction of dissolved oxygen in the electro-Fenton system and promote the further development of electro-Fenton oxidation technology, the preparation and selection of electrode materials has become a new research hotspot in this field. The cathode materials used in the traditional electro-Fenton system are mainly graphite, activated carbon or activated carbon fiber, etc. The catalytic activity of this type of electrode is not high enough, and the current efficiency is low, so the application of the electro-Fenton method is restricted to a certain extent.

Contents of the invention

The purpose of the present invention is to provide a preparation method and application of a graphene gas diffusion electrode, so as to improve the catalytic activity and current efficiency of the electrode in the electro-Fenton system.

In order to achieve the above object, the technical solution provided by the invention is: a kind of preparation method of graphene gas diffusion electrode, comprises the steps:

Step (1): React graphite flakes, NaNO ₃ and concentrated sulfuric acid at a ratio of 3.0 g: 1.5 ~ 2 g: 160 mL in an ice-water bath for 1 h, then weigh 9.0437 g KMnO ₄ and slowly add it to the beaker drop by drop within 3 h , react for 2 h;

Step (2): Remove the ice-water bath, raise the temperature to about 40 °C, and continue to stir for 1.5 h; slowly add 160 mL of distilled water, heat to boiling, and stir for 1 h;

Step (3): Put the mixed solution obtained in step 2 for a period of time, add 30 mL of 30% H ₂ O ₂ at 48-52°C, add 175 mL of distilled water, react for 3 h, filter after cooling; use a mass fraction of 30 % hydrochloric acid until there is no sulfate group, and then washed with distilled water until PH = 7, and the filter residue is vacuum-dried at 40°C to obtain graphene oxide;

Step (4): Weigh 100.0 mg of the graphene oxide obtained in Step 3 and put it into 100 mL of aqueous solution for ultrasonication until a stable dispersion with almost no obvious particles is obtained; take ammonia water with a mass fraction of 28% to adjust the pH of the dispersion to 10 ;

Step (5): The solution obtained in step 4 was centrifuged at 4000 r min ^-1 for 3 min to remove a very small amount of unexfoliated graphite oxide, and 0.2 mL of hydrazine hydrate was added to the centrifuged graphene oxide dispersion, and the Reaction 2 h, obtain graphene dispersion liquid;

Step (6): Take 0.8 g graphite and 160 mL Sonicate the 3% ethanol mixture at room temperature for 10 min, add 10-30 mL of the graphene dispersion obtained in step 5 and 0.2 g of polytetrafluoroethylene (PTFE) at room temperature for 15 min, heat in a water bath at a constant temperature of 80 °C until it becomes a paste, and take it out;

Step (7): After the paste mixture obtained in step 6 is slightly cooled, it evenly adheres to both sides of the nickel mesh. After the paste is solidified for a period of time, it is cold-pressed for 3 minutes (thickness is 0.5 - 0.7 mm), and placed in a muffle furnace Calcined at 300 °C for 1.5 h to obtain a graphene gas diffusion electrode.

The application of the graphene gas diffusion electrode obtained by the above preparation method in the electro-Fenton system.

The method for using the graphene gas diffusion electrode obtained by the above preparation method in the electric-Fenton system, before use, the electrode is soaked in acetone for 24 h to remove the residual ethanol and surface active substances in PTFE on its surface, and finally use Ionized water was repeatedly rinsed and dried, and connected and used according to the method of conventional electrodes.

Compared with prior art, the advantage of the present invention is:

1. What the present invention produces is a gas diffusion electrode doped by graphene. Compared with ordinary gas diffusion electrodes, the catalytic properties and high specific surface area of graphene itself provide graphene gas diffusion electrodes with better response Conditions and places, thus showing higher catalytic activity and current efficiency in the electro-Fenton system;

2. During the calcination process, the volume of polytetrafluoroethylene decreases, and the porosity of the electrode itself increases, so that the effective contact area between the electrode and the solution increases during the electro-Fenton reaction process, and the production of electrogenerated H ₂ O ₂ is promoted. Effectively improve the generation efficiency of hydroxyl radicals and enhance the oxidation capacity of the system;

3. Wide range of applications: it can be used in the treatment of various types of wastewater containing organic pollutants.

Description of drawings

Fig. 1 is the real photo of the graphene gas diffusion electrode prepared by embodiment 2;

Fig. 2 is the scanning electron microscope (SEM) of the graphene gas diffusion electrode prepared in embodiment 2;

Fig. 3 is the degradation efficiency of Rhodamine B by different electrodes in the electro-Fenton system of Example 2. (CP: conventional carbon electrode; DGE: graphene gas diffusion electrode).

detailed description

The present invention will be described in detail below with reference to the drawings and embodiments.

Example 1:

A kind of preparation method of graphene gas diffusion electrode, comprises the steps:

Step (1): flake graphite, NaNO ₃ and concentrated sulfuric acid were reacted in an ice-water bath at a ratio of 3.0 g: 1.5 g: 160 mL for 1 h, and then 9.0437 g KMnO ₄ was weighed and slowly added to the beaker dropwise within 3 h. Reaction 2 h;

Step (2): Remove the ice-water bath, raise the temperature to about 40 ℃, and continue stirring for 1.5 h. Slowly add 160 mL of distilled water, heat to boiling, and stir for 1 h;

Step (3): Put the mixed solution obtained in step 2 for a period of time, add 30 mL of 30% H ₂ O ₂ at 48-52°C, add 175 mL of distilled water, react for 3 h, and filter after cooling. Wash with 30% hydrochloric acid until there is no sulfate group, and then wash with distilled water until PH=7. The filter residue was vacuum-dried at 40°C to obtain graphene oxide;

Step (4): Weigh 100.0 mg of the graphene oxide obtained in Step 3 and put it into 100 mL aqueous solution for ultrasonication until a stable dispersion with almost no obvious particles is obtained. Get mass fraction and be that the ammoniacal liquor of 28% regulates the pH of dispersion liquid to 10;

Step (5): The solution obtained in step 4 was centrifuged at 4000 r min ^-1 for 3 min to remove a very small amount of unexfoliated graphite oxide, and 0.2 mL of hydrazine hydrate was added to the centrifuged graphene oxide dispersion, and the Reaction 2 h, obtain graphene dispersion liquid;

Step (6): Take 0.8 g graphite and 160 mL Sonicate the 3% ethanol mixture at room temperature for 10 min, add 30 mL of the graphene dispersion obtained in step 5 and 0.2 g of polytetrafluoroethylene (PTFE) at room temperature for 15 min, heat in a water bath at a constant temperature of 80 °C until it becomes a paste, and take it out;

Step (7): After the paste mixture obtained in step 6 is slightly cooled, it is evenly attached to both sides of the nickel mesh. After standing for a period of time, the paste is solidified, and then cold-pressed for 3 minutes (thickness is 0.7 mm), and placed in a muffle furnace at 300 °C Calcined for 1.5 h, the graphene gas diffusion electrode was obtained.

Example 2:

A kind of preparation method of graphene gas diffusion electrode, comprises the steps:

Step (1): React graphite flakes, NaNO ₃ and concentrated sulfuric acid at a ratio of 3.0 g: 2 g: 160 mL in an ice-water bath for 1 h, then weigh 9.0437 g KMnO ₄ and slowly add it to the beaker dropwise within 3 h. 2 h;

Step (2): Remove the ice-water bath, raise the temperature to about 40 ℃, and continue stirring for 1.5 h. Slowly add 160 mL of distilled water, heat to boiling, and stir for 1 h;

Step (3): Put the mixed solution obtained in step 2 for a period of time, add 30 mL of 30% H ₂ O ₂ at 48-52°C, add 175 mL of distilled water, react for 3 h, and filter after cooling. Wash with 30% hydrochloric acid until there is no sulfate group, and then wash with distilled water until PH=7. The filter residue was vacuum-dried at 40°C to obtain graphene oxide;

Step (4): Weigh 100.0 mg of the graphene oxide obtained in Step 3 and put it into 100 mL aqueous solution for ultrasonication until a stable dispersion with almost no obvious particles is obtained. Get mass fraction and be that the ammoniacal liquor of 28% regulates the pH of dispersion liquid to 10;

Step (5): The solution obtained in step 4 was centrifuged at 4000 r min ^-1 for 3 min to remove a very small amount of unexfoliated graphite oxide, and 0.2 mL of hydrazine hydrate was added to the centrifuged graphene oxide dispersion, and the Reaction 2 h, obtain graphene dispersion liquid;

Step (6): Take 0.8 g graphite and 160 mL Sonicate the 3% ethanol mixture at room temperature for 10 min, add 10 mL of the graphene dispersion obtained in step 5 and 0.2 g polytetrafluoroethylene (PTFE) at room temperature for 15 min, and heat it in a water bath at a constant temperature of 80 °C until it becomes a paste and take it out;

Step (7): After the paste mixture obtained in step 6 is slightly cooled, it is evenly attached to both sides of the nickel mesh. After standing for a period of time, the paste is solidified, then cold-pressed for 3 minutes (thickness is 0.5mm), and placed in a muffle furnace at 300 °C Calcined for 1.5 h, the graphene gas diffusion electrode was obtained.

The above-mentioned embodiment 2 is the best embodiment.

The electrode obtained in the above preferred embodiment was tested in the electro-Fenton system, and the sewage used was Rhodamine B simulated dye wastewater.

Before use, the electrodes were soaked in acetone for 24 h to remove residual ethanol and surface active substances in PTFE, and finally rinsed repeatedly with deionized water and dried. Then it is connected to the electro-Fenton system according to the conventional electrode method.

The test uses Rhodamine B to simulate dye wastewater. Transfer 50 mL of the prepared solution into a beaker with a Fe ²⁺ concentration of 0.33 mol/L. The titanium plate is used as the anode and the self-made graphene gas diffusion electrode is used as the cathode for degradation experiments. The effective area is 0.7 cm ² (1 cm long and 0.7 cm wide). The rhodamine B concentration was 10 mg/L, the treatment volume was 50 mL, the reaction time was 60 min, the current density was 20 mA/cm ² , the electrolyte (NaSO ₄ ) concentration was 0.05 mol/L, the electrode distance was 1 cm, and the initial pH= 3.0, full aeration. The degradation efficiency of the gas diffusion electrode (GDE) prepared above was measured in the electro-Fenton system. The results showed that under the same conditions, the removal rate of rhodamine B by the self-made gas diffusion electrode reached 90% in 60 minutes, which was 1.5 times that of the traditional carbon electrode (CP).

Claims (3)

1. the preparation method of a Graphene gas-diffusion electrode, it is characterised in that comprise the steps:

Step (1): by crystalline flake graphite, NaNO₃In ice-water bath, react 1 h with concentrated sulphuric acid in the ratio of 3.0 g: 1.5 ~ 2g: 160 mL, then weigh 9.0437 g KMnO₄In 3 h, dropwise it is slowly added to beaker, reacts 2 h；

Step (2): remove ice-water bath, is warmed up to about 40 DEG C, continues stirring reaction 1.5 h；It is slowly added to 160 mL distilled water, is heated to boiling, stirring reaction 1 h；

Step (3): the mixed solution of step 2 gained is placed a period of time, adds the H of 30 mL 30% in 48-52 DEG C₂O₂, add 175 mL distilled water, react 3 h, cooled and filtered；With the salt acid elution that mass fraction is 30% to sulfate radical-free, then being washed with distilled water to PH=7, filtering residue, in 40 DEG C of vacuum drying, prepares graphene oxide；

Step (4): the graphene oxide of step 3 gained weighs 100.0 mg ultrasonic in 100 mL aqueous solutions, until obtaining the stable dispersions almost without obvious granule；Take the pH to 10 of the ammonia regulation dispersion liquid that mass fraction is 28%；

Step (5): by the solution of step 4 gained at 4000 r min^-1It is centrifuged down 3 min and removes the graphite oxide that very small amount is unstripped, the graphene oxide dispersion after centrifugal adds 0.2mL hydrazine hydrate, reacts 2 h at 90 DEG C, obtain graphene dispersing solution；

Step (6): take 0.8 g graphite and 160 mL 3% alcohol mixtures in ultrasonic 10 min of room temperature, add graphene dispersing solution 10 ~ 30 mL and 0.2 ultrasonic 15 min of g polytetrafluoroethylene (PTFE) room temperature of step 5 gained, be heated to pasty state water-bath constant temperature 80 DEG C and take out；

Step (7): be uniformly attached to nickel screen both sides after the pasty mixture of step 6 gained somewhat cools down, after placing a period of time mushy freezing, 3 min molding of colding pressing (thickness is 0.5- 0.7 mm), calcine 1.5 h in Muffle furnace 300 DEG C, obtain Graphene gas-diffusion electrode.

2. the Graphene gas-diffusion electrode obtained according to the above-mentioned preparation method application in electricity-Fenton-like system.

3. the Graphene gas-diffusion electrode obtained according to the above-mentioned preparation method using method in electricity-Fenton-like system, it is characterized in that: before use, electrode soaks 24 h in acetone, to remove the surfactant in the ethanol of its remained on surface and PTFE, finally repeatedly rinse with deionized water and dry, accessing according to the method for conventional electrodes and use.