Method for preparing carbon-cobalt core-shell structure catalyst based on waste and application of the catalyst in electro-fenton degradation of organic pollutants

Abstract

The application discloses a method for preparing a carbon-cobalt core-shell structure catalyst based on waste and application of the carbon-cobalt core-shell structure catalyst in electro-Fenton degradation of organic pollutants, clean waste bamboo shoots are dried after being washed, and are ground into powder to obtain material A; the material A is carbonized in a hydrothermal reaction kettle to obtain material B; the material B is centrifugally cleaned, dried, and ground to obtain material C; deionized water, Co(NO3)2.6H2O and triphenylphosphine are sequentially added into the material C, and the mixture is uniformly stirred and vacuum dried to obtain material D; the material D is placed in a tube furnace, and is calcined under an inert atmosphere and at a temperature of 750-850 DEG C to obtain the carbon-cobalt core-shell structure catalyst. –1 The nitrogen and phosphorus double-doped carbon-coated Co nanoparticle core-shell structure prepared based on the waste has an excellent electro-Fenton performance, and can degrade 95% of a 10mg / L methylene blue solution in a 0.05mol / L Na2SO4 solution in only 15min. −1 ​

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of carbon-cobalt catalysts and electro-Fenton degradation of organic pollutants, and particularly relates to a method for preparing a carbon-cobalt core-shell structure catalyst based on waste and application of the carbon-cobalt core-shell structure catalyst in electro-Fenton degradation of organic pollutants. BACKGROUND

[0002] In the electro-Fenton degradation system of organic pollutants, hydrogen peroxide (H2O2) is generated by oxygen reduction at the cathode, which consumes two electrons. This process is a competitive reaction with the four-electron pathway of oxygen molecule reduction to produce H2O. The difference between the two lies in whether the O-O bond is broken in the electrode reaction. Therefore, the research focus of electro-Fenton technology is to improve the electrochemical activity of the cathode material and the selectivity of the two-electron pathway of ORR. In order to improve the electrochemical activity of the cathode material, two different strategies of improving the apparent activity and the intrinsic activity are usually adopted, and both are usually affected by factors such as the structure and morphology of the electrocatalyst. The apparent activity is often dependent on the number of exposed active sites, which can be improved by adjusting the structure of the material to expose more active sites, thereby improving the utilization rate of the active sites. The intrinsic activity is closely related to the electronic structure of the catalyst, which can be adjusted by introducing vacancies or heteroatoms through doping technology to improve the intrinsic activity of each active site of the catalyst. It is generally believed that the two-electron selectivity of the ORR of the cathode material is related to factors such as the adsorption mode and binding energy of oxygen on the electrode surface. Therefore, exploring a catalytic material that can increase the adsorption of oxygen on the electrode surface and reduce the binding energy between them has become the focus of the next research work.

[0003] Biomass materials have attracted great attention from researchers due to their wide sources in nature and environmental friendliness. Based on the natural characteristics of biomass materials, catalytic materials rich in hierarchical porous structures, active defect sites, and oxygen and nitrogen functional groups can be constructed using them as precursors. Therefore, processing waste biomass into high-value-added electro-Fenton catalysts can provide a low-cost, high-catalytic-activity cathode material for the electro-Fenton process. However, biomass nitrogen-doped carbon-based catalysts tend to promote the four-electron ORR to generate H2O, which limits their application in the electro-Fenton system. Recent studies have shown that the introduction of transition metals can cause the rearrangement of nitrogen configurations, thereby selectively triggering ORR to form H2O2. Therefore, based on biomass nitrogen-doped carbon materials, the present application introduces transition metal Co to adjust the nitrogen configuration, improve the intrinsic activity of the active sites of the catalyst, and introduces phosphorus to further improve the specific surface area of the material, thereby showing higher apparent activity, so as to prepare a low-cost, high-activity electro-Fenton catalyst. SUMMARY

[0004] The technical problem solved by the present application is to provide a simple and efficient method for preparing a carbon-cobalt core-shell structure catalyst based on waste, which is prepared by one-pot calcination.

[0005] The present application solves the above technical problems by using the following technical solution, a method for preparing a carbon-cobalt core-shell structure catalyst based on waste, characterized by the following specific process:

[0006] Step S1: clean the waste bamboo shoots, dry them in a blast drying oven, then grind them into powder in a pulverizer to obtain material A;

[0007] Step S2: carbonize material A obtained in step S1 in a hydrothermal reaction kettle to obtain material B;

[0008] Step S3: centrifugally wash material B obtained in step S2 with deionized water, then dry it in a vacuum drying oven, and grind it to obtain material C;

[0009] Step S4: add deionized water, Co(NO3)2·6H2O and triphenylphosphine (PPh3) to material C obtained in step S3 in sequence, stir and mix them uniformly, and then vacuum dry to obtain material D;

[0010] Step S5: place material D obtained in step S4 in a tube furnace, heat it to 750-850℃ under an inert atmosphere, and calcine it to obtain the target product, a carbon-cobalt core-shell structure catalyst.

[0011] Further limitation, the drying temperature in step S1 is 70℃, and the drying time is 24h.

[0012] Further limitation, the carbonization temperature in step S2 is 180℃, and the carbonization time is 5.5h.

[0013] Further limitation, the centrifugal washing speed in step S3 is 10000r / min, the centrifugal washing time is 5min, the centrifugal washing frequency is 5 times, the drying temperature is 70℃, and the drying time is 24h. −1

[0014] ​Further limited, the material C, deionized water, Co(NO3)2.6H2O and triphenylphosphine in step S4 are 0.5g:15mL:0.2mmol:0.05~0.15g, the stirring mixing temperature is 60℃, the stirring mixing time is 2h, the stirring speed is 200r / min −1 , the vacuum drying temperature is 100℃, and the vacuum drying time is 10h.

[0015] Further limited, the inert atmosphere in step S5 is nitrogen, the heating rate is 5℃ / min −1 , and the calcination time is 2h.

[0016] The method for preparing a carbon-cobalt core-shell structure catalyst based on waste according to the application is characterized in that the specific steps are as follows:

[0017] Step S1: clean the waste bamboo shoots, dry them in a blast drying oven at 70℃ for 24h, then grind them into powder in a pulverizer to obtain material A;

[0018] Step S2: take 2g of material A, add 18mL of deionized water, and use a 100mL hydrothermal reactor to carbonize at 180℃ for 5.5h to obtain material B;

[0019] Step S3: use deionized water to centrifuge material B obtained in step S1 for 5 times, each time at a speed of 10000r / min −1 for 5min, collect and dry in a vacuum drying oven at 70℃ for 24h to obtain material C;

[0020] Step S4: add 15mL of deionized water, 0.2mmol of Co(NO3)2.6H2O and 0.05~0.15g of triphenylphosphine (PPh3) into 0.5g of material C obtained in step S3 in sequence, stir at 60℃ for 2h, then place in a vacuum drying oven and dry at 100℃ for 10h to obtain material D;

[0021] Step S5: place material D obtained in step S4 in a tube furnace, heat to 750~850℃ at a heating rate of 5℃ / min −1 , carbonize for 2h, the gas in the tube furnace is flowing nitrogen, and finally obtain the target product carbon-cobalt core-shell structure electro-Fenton catalyst. −1 The structure electro-Fenton catalyst is beneficial to improve the intrinsic activity of biomass carbon material, speed up the mass transfer rate, and provide abundant active sites. The prepared electro-Fenton catalyst can degrade 95% of 10mg / L −1 of methylene blue solution in only 15min, and has excellent electro-Fenton performance.

[0022] The application of the carbon-cobalt core-shell structure catalyst of the present invention in the electro-Fenton degradation of organic pollutants is characterized by: forming a three-electrode system in a single-chamber electrolytic cell, wherein the carbon-cobalt core-shell structure catalyst is the working electrode, the electrolyte is an acidic solution, and the organic pollutants are completely degraded after an external potential is applied.

[0023] Further specifying, in the three-electrode system, the platinum sheet and the saturated calomel electrode serve as the counter electrode and reference electrode, respectively, and the acidic solution is 0.05 mol / L at pH=2. –1 Na2SO4 solution, with an applied potential of -0.6 to -0.9 V.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] 1. This invention utilizes waste bamboo shoots as a carbon precursor, which is widely available, inexpensive, and environmentally friendly, achieving "pollution control with waste" and facilitating large-scale preparation and application.

[0026] 2. This invention employs a one-pot, one-step synthesis method, in which bamboo shoots, deionized water, Co(NO3)2·6H2O, and triphenylphosphine (PPh3) are mixed and calcined in a tube furnace. The synthesis method is simple and efficient, requiring no complicated operating steps.

[0027] 3. The core-shell structured electro-Fenton catalyst prepared by this invention has a stable structure, which is beneficial for long-term operation in acidic environments.

[0028] 4. This invention utilizes Co to regulate the nitrogen configuration, resulting in high two-electron ORR activity. P doping increases the specific surface area of ​​the material, which is beneficial for exposing more active sites.

[0029] 5. The present invention provides a nitrogen- and phosphorus dual-doped carbon-coated Co nanoparticle core-shell structure prepared from waste materials in 0.05 mol / L... –1 In Na2SO4 solution, 10 mg L can be removed in just 15 minutes. −1 It degrades 95% of methylene blue solution and exhibits excellent electro-Fenton properties. Attached Figure Description

[0030] Figure 1 A scanning electron microscope image of the target product E1 prepared in Example 1;

[0031] Figure 2 Transmission electron microscopy image of target product E1 prepared in Example 1;

[0032] Figure 3 The degradation performance diagram of the target product prepared in Example 1;

[0033] Figure 4Degradation rate chart of target products E1-E5 prepared for Examples 2-5;

[0034] Figure 5 Electron transfer number chart of target products E1-E5 prepared for Examples 2-5. DETAILED DESCRIPTION

[0035] The above content of the present application is further illustrated in detail by the following examples, but this should not be understood as the scope of the above subject matter of the present application being limited to the following examples only, and any technology realized based on the above content of the present application falls within the scope of the present application. EXAMPLE

[0036] Step S1: The waste bamboo shoots were cleaned and dried in a blast drying oven at 70°C for 24h, and then ground into powder in a pulverizer to obtain material A1;

[0037] Step S2: 2g of material A1 was added into 18mL of deionized water, and a 100mL hydrothermal reactor was used to react at 180°C for 5.5h to obtain material B1;

[0038] Step S3: The material B1 obtained in step S1 was centrifuged with deionized water for 5 times, each time at a speed of 10000r min −1 for 5min, and then collected and dried in a vacuum drying oven at 70°C for 24h to obtain material C1;

[0039] Step S4: 0.5g of material C1 obtained in step S3 was added into 15mL of deionized water, 0.2mmol of Co(NO3)2·6H2O and 0.1g of triphenylphosphine (PPh3) in sequence, stirred at 60°C for 2h, and then dried in a vacuum drying oven at 100°C for 10h to obtain material D1;

[0040] Step S5: The material D1 obtained in step S4 was placed in a tube furnace and carbonized at 800°C for 2h with a heating rate of 5°C min −1 , and the gas in the tube furnace was flowing nitrogen, to finally obtain the target product electro-Fenton catalyst E1. EXAMPLE

[0041] Step S1: The waste bamboo shoots were cleaned and dried in a blast drying oven at 70°C for 24h, and then ground into powder in a pulverizer to obtain material A2;

[0042] Step S2: 2g of material A2 was added into 18mL of deionized water, and a 100mL hydrothermal reactor was used to react at 180°C for 5.5h to obtain material B2;

[0043] Step S3: The material B2 obtained in step S1 was centrifuged with deionized water for 5 times, each time at a speed of 10000r min−1 Centrifuge at a speed of 5 min, collect and dry in a vacuum drying oven at 70℃ for 24 h to obtain material C2;

[0044] Step S4: Take 0.5g of material C2 obtained in step S3, add 15mL of deionized water, 0.2mmol of Co(NO3)2·6H2O and 0.05g of triphenylphosphine (PPh3) in sequence, stir at 60℃ for 2h, and then place in a vacuum drying oven to dry at 100℃ for 10h to obtain material D2;

[0045] Step S5: Place the material D2 obtained in step S4 into a tube furnace and heat it at 5°C for 5 min. −1 The temperature was increased to 800℃ and carbonized for 2 hours at a rising rate. The gas inside the tubular furnace was flowing nitrogen, and the target product, electro-Fenton catalyst E2, was finally obtained. Example

[0046] Step S1: After cleaning the waste bamboo shoots, dry them in a forced-air drying oven at 70℃ for 24 hours, and then grind them into powder in a pulverizer to obtain material A3;

[0047] Step S2: Take 2g of material A3 and add 18mL of deionized water. React in a 100mL hydrothermal reactor at 180℃ for 5.5h to obtain material B3.

[0048] Step S3: Centrifuge material B3 obtained in step S1 five times with deionized water, each time at 10,000 rpm. −1 Centrifuge at a speed of 5 min, collect and dry in a vacuum drying oven at 70℃ for 24 h to obtain material C3;

[0049] Step S4: Take 0.5g of material C3 obtained in step S3, add 15mL of deionized water, 0.2mmol of Co(NO3)2·6H2O and 0.15g of triphenylphosphine (PPh3) in sequence, stir at 60℃ for 2h, and then place in a vacuum drying oven to dry at 100℃ for 10h to obtain material D3;

[0050] Step S5: Place the material D3 obtained in step S4 into a tube furnace and heat it at 5°C for 5 min. −1 The temperature was increased to 800℃ and carbonized for 2 hours at a rising rate. The gas inside the tubular furnace was flowing nitrogen, and the target product, electro-Fenton catalyst E3, was finally obtained. Example

[0051] Step S1: After cleaning the waste bamboo shoots, dry them in a forced-air drying oven at 70℃ for 24 hours, and then grind them into powder in a pulverizer to obtain material A4;

[0052] Step S2: Take 2g of material A4 and add 18mL of deionized water. React in a 100mL hydrothermal reactor at 180℃ for 5.5h to obtain material B4.

[0053] Step S3: Centrifuge material B4 obtained in step S1 five times with deionized water, each time at 10,000 rpm. −1 Centrifuge at a speed of 5 min, collect and dry in a vacuum drying oven at 70℃ for 24 h to obtain material C4;

[0054] Step S4: Take 0.5g of material C4 obtained in step S3, add 15mL of deionized water, 0.2mmol of Co(NO3)2·6H2O and 0.1g of triphenylphosphine (PPh3) in sequence, stir at 60℃ for 2h, and then place in a vacuum drying oven to dry at 100℃ for 10h to obtain material D4;

[0055] Step S5: Place the material D4 obtained in step S4 into a tube furnace and heat it at 5°C for 5 min. −1 The temperature was increased to 750℃ and carbonized for 2 hours at a rising rate. The gas inside the tubular furnace was flowing nitrogen, and the target product, electro-Fenton catalyst E4, was finally obtained. Example

[0056] Step S1: After cleaning the waste bamboo shoots, dry them in a forced-air drying oven at 70℃ for 24 hours, and then grind them into powder in a pulverizer to obtain material A5;

[0057] Step S2: Take 2g of material A5 and add 18mL of deionized water. React in a 100mL hydrothermal reactor at 180℃ for 5.5h to obtain material B5.

[0058] Step S3: Centrifuge material B5 obtained in step S1 five times with deionized water, each time at 10,000 rpm. −1 Centrifuge at a speed of 5 min, collect and dry in a vacuum drying oven at 70℃ for 24 h to obtain material C5;

[0059] Step S4: Take 0.5g of material C5 obtained in step S3, add 15mL of deionized water, 0.2mmol of Co(NO3)2·6H2O and 0.1g of triphenylphosphine (PPh3) in sequence, stir at 60℃ for 2h, and then place in a vacuum drying oven to dry at 100℃ for 10h to obtain material D5;

[0060] Step S5: Place the material D5 obtained in step S4 into a tube furnace and heat it at 5°C for 5 min. −1 The temperature was increased to 850℃ and carbonized for 2 hours. The gas inside the tubular furnace was flowing nitrogen, and the target product, electro-Fenton catalyst E5, was finally obtained.

[0061] Physical characterization of the catalyst prepared:

[0062] Figure 1 The scanning electron microscope image of the target product E1 prepared in Example 1 shows that it has a nanoparticle morphology, and the particle size is determined by Figure 2 The transmission electron microscope image shows a clear core-shell structure, which indicates that the experimental scheme can prepare the waste bamboo shoots into an electro-Fenton catalyst with a specific structure.

[0063] Degradation performance and electrochemical performance test:

[0064] Methylene blue was used as a representative pollutant, and the degradation reaction was driven by an electrochemical workstation in a single-chamber electrolytic cell. The electrolyte was a Na2SO4 solution containing Fenton reagent FeSO4 (pH = 2.0, 0.05 mol L −1 ). The stainless steel mesh (1 cm 2 ) coated with the sample, platinum sheet, and mercury electrode were used as the working electrode, counter electrode, and reference electrode, respectively. Finally, the absorbance of the methylene blue solution was determined by UV-vis to confirm the change in its concentration. Figure 3 The pollutant concentration change graph of the target product E1 prepared in Example 1 during the degradation process shows that the pollutant concentration decreases by 95% after 15 min. Figure 4 The degradation performance graph of the target products E1-E5 prepared in all examples shows that the time required to degrade 97% of the pollutants is 20 min, 30 min, 35 min, 40 min, and 60 min, respectively.

[0065] Linear sweep voltammetry (LSV) test was completed in a three-electrode system. The rotating ring-disk electrode (RRDE) coated with a catalyst coating and having a diameter of 5 mm, platinum sheet (1 cm 2 ), and saturated mercury-mercury chloride electrode (Hg / HgCl2, SCE) were used as the working electrode, counter electrode, and reference electrode, respectively. The reaction electrolyte was 0.05 mol L −1 Na2SO4 solution saturated with O2 (pH = 2.0). Figure 5 The electron transfer number graph of the target products E1-E5 prepared in all examples shows good oxygen reduction activity.

[0066] The above examples describe the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples. The above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application.

Claims

1. A method for preparing a carbon-cobalt core-shell structure catalyst based on waste, characterized by The specific process is as follows: Step S1: the waste bamboo shoots are cleaned and dried in a blast drying oven, and then ground into powder in a grinder to obtain material A; Step S2: the material A obtained in step S1 is carbonized in a hydrothermal reaction kettle to obtain material B; Step S3: the material B obtained in step S2 is washed by centrifugation with deionized water, and then dried in a vacuum drying oven. After grinding, material C is obtained; Step S4: deionized water, Co(NO3)2·6H2O and triphenylphosphine are sequentially added to the material C obtained in step S3, and the mixture is stirred and mixed uniformly, and then vacuum dried to obtain material D; Step S5: the material D obtained in step S4 is placed in a tube furnace and calcined at 750-850℃ under inert atmosphere, and finally the target product carbon-cobalt core-shell structure catalyst is obtained; The carbon-cobalt core-shell structure catalyst is used for electro-Fenton degradation of organic pollutants, and the catalyst has excellent H2O2 selectivity, and the specific process is as follows: a three-electrode system is composed in a single-chamber electrolytic cell, the carbon-cobalt core-shell structure catalyst is used as a working electrode, an electrolyte is an acidic solution, after an external potential is applied, the organic pollutants are completely degraded, a platinum sheet and a saturated calomel electrode are used as a counter electrode and a reference electrode respectively in the three-electrode system, the acidic solution is 0.05 mol / L –1 Na2SO4 solution, and the applied external potential is-0.6 to-0.9 V.

2. The method of claim 1, wherein the carbon-cobalt core-shell structure catalyst is prepared based on waste. The drying temperature in step S1 is 70℃, and the drying time is 24h.

3. The method of claim 1, wherein the waste-based preparation of carbon-cobalt core-shell structure catalyst is characterized by: The carbonization temperature in step S2 is 180℃, and the carbonization time is 5.5h.

4. The method of claim 1, wherein the waste-based preparation of carbon-cobalt core-shell structure catalyst is characterized by: The centrifugal washing rotation speed in step S3 is 10000 r / min -1 The centrifugal washing time is 5 min, the centrifugal washing times is 5 times, the drying temperature is 70℃, and the drying time is 24 h.

5. The method of claim 1, wherein the waste-based preparation of carbon-cobalt core-shell structure catalyst is characterized by: In step S4, the feeding ratio of material C, deionized water, Co(NO3)2·6H2O, and triphenylphosphine is 0.5g:15mL:0.2mmol:0.05~0.15g. The mixing temperature is 60℃, the mixing time is 2h, and the stirring speed is 200r / min. -1 The vacuum drying temperature is 100℃ and the vacuum drying time is 10h.

6. The method of claim 1, wherein the waste-based preparation of carbon-cobalt core-shell structure catalyst is characterized by: The inert atmosphere in step S5 is nitrogen, the temperature increase rate is 5°C / min -1 , and the calcination time is 2 h.

7. The method of claim 1, wherein the waste-based preparation of carbon-cobalt core-shell structure catalyst is characterized by The specific steps are as follows: Step S1: the waste bamboo shoots are cleaned and dried in a blast drying oven at 70℃ for 24h, and then ground into powder in a grinder to obtain material A; Step S2: 2g of material A is added to 18mL of deionized water, and a 100mL hydrothermal reaction kettle is used for carbonization reaction at 180℃ for 5.5h to obtain material B; Step S3: Centrifuge material B obtained in step S1 five times with deionized water, each time at 10,000 rpm. -1 Centrifuge at a speed of 5 min, collect and dry in a vacuum drying oven at 70℃ for 24 h to obtain material C; Step S4: 15mL of deionized water, 0.2mmol of Co(NO3)2·6H2O and 0.05-0.15g of triphenylphosphine (PPh3) are sequentially added to 0.5g of material C obtained in step S3, and stirred at 60℃ for 2h, and then placed in a vacuum drying oven and dried at 100℃ for 10h to obtain material D; Step S5: The material D obtained in step S4 is placed in a tube furnace to carbonize at 750-850℃ for 2h at a heating rate of 5℃min -1 , with flowing nitrogen gas in the tube furnace, to obtain the target product carbon-cobalt core-shell structure electro-Fenton catalyst. This structure is beneficial to improve the intrinsic activity of biomass carbon material, accelerate the mass transfer rate, and provide abundant active sites. The prepared electro-Fenton catalyst can degrade 95% of 10mg / L -1 methylene blue solution in only 15min, showing excellent electro-Fenton performance.

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