Graphite felt cathode material, preparation method and application thereof

Abstract

The application provides a kind of graphite felt cathode material and its preparation method and application, belong to in-situ electrochemistry technical field. With graphite felt as substrate, with CB as catalyst, PTFE as binder, isopropanol as dispersant, SDS as pore forming agent, by annealing calcination, prepare graphite felt cathode material. In the application, SDS can not only regulate the hydrophobic property and pore structure of graphite felt cathode surface, but also introduce a small amount of S element, improve the electrocatalytic activity area of cathode material. SDS-CB-PTFE cathode material has high electrocatalytic activity, synergistically utilizes anode oxidation and cathode H2O2 oxidation, simultaneously realizes efficient degradation of organic pollutants, provides a new idea for the preparation of oxygen reduction H2O2 cathode material. The constructed electro-fenton system realizes the synchronous efficient degradation of tetracycline hydrochloride, rhodamine B and other organic pollutants by the synergistic effect of high concentration H2O2 generated by cathode and direct oxidation on anode surface.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of in-situ electrochemistry, and particularly relates to a graphite felt cathode material and a preparation method and application thereof. BACKGROUND

[0002] H2O2 is an environmentally friendly multifunctional oxidant, which has been widely used in the synthesis of organic compounds, wastewater treatment and destruction of hazardous organic waste, etc. By electrocatalytic oxygen reduction reaction, H2O2 is synthesized by electricity. In principle, only O2 (air), water and electricity are needed. H2O2 is produced by two-electron reduction of O2. During the electrolysis process, H2O2 is generated on the surface of the cathode, and its concentration continues to accumulate. This reaction is strongly dependent on the physical and chemical properties and electronic structure of the cathode material.

[0003] Carbonaceous materials have become an attractive alternative to previous metals as H2O2 electrocatalysts due to their non-toxicity, high stability, high electrical conductivity and high specific surface area. And the ordered pore structure on the surface of carbonaceous materials is beneficial to the distribution and diffusion of active sites, which can alleviate the mass transfer and diffusion problems of reactant components. However, due to the weak activity of carbonaceous materials themselves, they have little contribution to the in-situ electro-synthesis of H2O2. In order to improve the catalytic activity and selectivity of the two-electron oxygen reduction reaction of carbon-based catalysts, surface treatment and defect site modification of carbonaceous materials are usually required to improve their catalytic activity and achieve efficient in-situ electro-synthesis of H2O2.

[0004] The activation of O2 molecules is based on the active sites of carbonaceous cathodes. The adsorption and diffusion behavior of O2 on the surface of the material is affected by the pore structure of the material, and its electronic structure also changes with the size of the material pore size. When the pore size of the cathode material is large, O2 molecules can freely enter and exit and the concentration does not affect the diffusion. Therefore, how to adjust the pore structure and pore size of carbon-based catalysts is a key factor to improve their catalytic performance, so as to achieve higher H2O2 production capacity. SUMMARY

[0005] The purpose of the present application is to provide a graphite felt cathode material and a preparation method and application thereof to overcome the above-mentioned deficiencies of the prior art. The sodium dodecyl sulfonate modified graphite felt efficiently generates H2O2 cathode in-situ, without additional air or oxygen, but by floating the cathode on the surface of the electrolyte to construct a gas-liquid-solid three-phase interface, directly using the oxygen in the air to produce H2O2 by oxygen reduction reaction, and using solar photovoltaic panels as power supply to realize green and low-consumption in-situ degradation of organic pollutants.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] The first purpose of the present application is to provide a preparation method of a graphite felt cathode material, comprising the following specific steps:

[0008] Step S1, pretreatment of graphite felt; the original graphite felt is cleaned with anhydrous ethanol and deionized water to remove impurities, and dried for standby;

[0009] Step S2, preparation of catalyst solution: a certain amount of carbon black, polytetrafluoroethylene, isopropyl alcohol is added to deionized water, and ultrasonic mixing is uniformly obtained to obtain a first catalyst solution;

[0010] Step S3, adding sodium dodecyl sulfonate to the first catalyst solution obtained in step S2 to obtain a second catalyst solution;

[0011] Step S4, the pretreated graphite felt substrate obtained in step S1 is placed in the second catalyst solution obtained in step S3, and after ultrasonic immersion and drying, a graphite felt electrode is obtained;

[0012] Step S5, annealing and calcining the graphite felt electrode obtained in step S4 at high temperature to obtain a graphite felt cathode material.

[0013] Further, in step S2, the mass-volume ratio of carbon black, polytetrafluoroethylene, isopropyl alcohol and deionized water is (0.3-1.5) g :(0.5-5) mL :(1-5) mL :(30-150) mL.

[0014] Further, in step S3, the mass ratio of the amount of sodium dodecyl sulfonate added to the mass of the carbon black is (0.1-1) g :(0.3-1.5) g.

[0015] Further, in step S4, the ultrasonic immersion time is 25-30 min; and the drying temperature is 60-80 DEG C.

[0016] Further, in step S5, the annealing and calcining temperature is 340-360 DEG C, and the calcining time is 40-60 min.

[0017] Further, in step S1, the pretreatment process is that the graphite felt raw material is cut into 4-10 cm 2 in size, cleaned with anhydrous ethanol and deionized water, and dried.

[0018] The second object of the present application is to provide a graphite felt cathode material prepared by the above preparation method.

[0019] The third object of the present application is to provide an electro-Fenton system comprising the above graphite felt cathode material.

[0020] The fourth object of the present application is to provide the use of the above graphite felt cathode material in the in-situ degradation of organic pollutants.

[0021] The fifth object of the present application is to provide a method for in-situ degradation of organic pollutants, using the above-mentioned graphite felt cathode material as the cathode, using a ruthenium-iridium electrode as the anode, connecting a solar photovoltaic panel with the electrochemical reaction device, and adding wastewater containing organic pollutants into the cathode chamber and the anode chamber respectively, so as to realize the degradation of the organic pollutants by anodic oxidation and cathode-generated H2O2.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) The present application provides a graphite felt cathode material, a preparation method and application thereof. The SDS-CB-PTFE cathode material is prepared by using graphite felt as the substrate, CB as the catalyst, PTFE as the binder, isopropanol as the dispersant, and SDS as the pore-forming agent, and then annealing and calcining. In the present application, the SDS can not only regulate the hydrophobicity and pore structure of the graphite felt cathode surface, but also introduce a small amount of S element to improve the electrocatalytic activity area of the cathode material. The SDS-CB-PTFE cathode material has high electrocatalytic activity, and can realize the simultaneous efficient degradation of organic pollutants by synergistic utilization of anodic oxidation and cathode-generated H2O2 oxidation. The present application provides a new idea for the preparation of H2O2 cathode material for oxygen reduction. The constructed electro-Fenton system can realize the simultaneous efficient degradation of organic pollutants such as tetracycline hydrochloride and rhodamine B by the synergistic utilization of high-concentration H2O2 generated by the cathode and the direct oxidation on the anode surface.

[0024] (2) The present application applies the SDS-CB-PTFE to in-situ degradation of organic pollutants, uses oxygen in the air as the oxygen source without additional air or oxygen, and uses a clean energy solar photovoltaic panel as the power supply. Under the condition of low power consumption and energy consumption, the present application realizes green, low-energy and efficient in-situ degradation of organic pollutants, and provides a new method for electrocatalytic degradation of pollutants.

[0025] (3) The material used in the present application has low cost and wide source, and the preparation method is simple and easy to operate. While ensuring the catalytic performance, the present application effectively reduces the use cost. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM images of GF, CB-PTFE and SDS-CB-PTFE;

[0027] Figures 2a-2c BET images of GF, CB-PTFE and SDS-CB-PTFE;

[0028] Figures 3a-3b H2O2 generation and current efficiency images of CB-PTFE and SDS-CB-PTFE;

[0029] Figures 4a-4bEffect of different current densities on H2O2 production by SDS-CB-PTFE

[0030] Figures 5a-5b is a SDS-CB-PTFE stability test diagram;

[0031] Figure 6 is an outdoor experimental device diagram;

[0032] Figures 7a-7c is a diagram of a solar photovoltaic panel for powering catalytic degradation of TC and RhB. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application are described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0034] In the present application, graphite felt is abbreviated as GF; carbon black is abbreviated as CB; polytetrafluoroethylene is abbreviated as PTFE; and sodium dodecyl sulfonate is abbreviated as SDS.

[0035] The graphite felt used in the present application is purchased from Tianjin Carbon Factory.

[0036] Example 1

[0037] The present application provides a preparation method of a graphite felt cathode material SDS-CB-PTFE.

[0038] The specific steps are as follows:

[0039] Step S1, the original graphite felt with a thickness of 2 mm and a size of 2*4 cm is cleaned with anhydrous ethanol and deionized water and dried to remove impurities;

[0040] Step S2, a catalyst solution is prepared: CB is 0.3 g, PTFE is 0.955 mL, isopropyl alcohol is 1.5 mL, deionized water is 30 mL, and ultrasonic mixing is performed for 10 min to obtain a first catalyst solution;

[0041] Step S3, 0.5 g of SDS is added to the first catalyst solution and mixed to obtain a second catalyst solution;

[0042] Step S4, the pretreated graphite felt substrate obtained in step S1 is placed in the second catalyst solution, ultrasonic immersion is performed for 30 min, and then drying is performed at 60 DEG C to obtain a graphite felt electrode;

[0043] Step S5, the graphite felt electrode is placed into a muffle furnace for annealing calcination at 350 DEG C for 40 min to obtain the graphite felt cathode material SDS-CB-PTFE.

[0044] Example 2

[0045] The application provides a preparation method of a graphite felt cathode material SDS-CB-PTFE.

[0046] The specific steps are as follows:

[0047] Step S1, the original graphite felt with a thickness of 2 mm and a size of 2*4 cm is cleaned with anhydrous ethanol and deionized water and dried to remove impurities;

[0048] Step S2, a catalyst solution is prepared: CB is 0.9 g, PTFE is 0.5 mL, isopropyl alcohol is 1 mL, deionized water is 30 mL, and ultrasonic mixing is performed for 10 min to obtain a first catalyst solution;

[0049] Step S3, 0.1 g of SDS is added to the first catalyst solution and uniformly mixed to obtain a second catalyst solution;

[0050] Step S4, the pretreated graphite felt substrate obtained in step S1 is placed into the second catalyst solution, ultrasonic immersion is performed for 25 min, and drying is performed at 75 DEG C to obtain a graphite felt electrode;

[0051] Step S5, the graphite felt electrode is placed into a muffle furnace for annealing calcination at 340 DEG C for 60 min to obtain the graphite felt cathode material SDS-CB-PTFE.

[0052] Example 3

[0053] The application provides a preparation method of a graphite felt cathode material SDS-CB-PTFE.

[0054] The specific steps are as follows:

[0055] Step S1, the original graphite felt with a thickness of 2 mm and a size of 2*4 cm is cleaned with anhydrous ethanol and deionized water and dried to remove impurities;

[0056] Step S2, a catalyst solution is prepared: CB is 0.9 g, PTFE is 0.5 mL, isopropyl alcohol is 1 mL, deionized water is 30 mL, and ultrasonic mixing is performed for 10 min to obtain a first catalyst solution;

[0057] Step S3, 0.1 g of SDS is added to the first catalyst solution and uniformly mixed to obtain a second catalyst solution;

[0058] Step S4, the pretreated graphite felt substrate obtained in step S1 was put into the second catalyst solution, and after ultrasonic immersion for 25 min, it was dried at 80℃ to obtain a graphite felt electrode;

[0059] Step S5, the graphite felt electrode was put into a muffle furnace and annealed and calcined at 360℃ for 50 min to obtain a graphite felt cathode material SDS-CB-PTFE.

[0060] Comparative Example 1

[0061] The application provides a preparation method of a graphite felt cathode material CB-PTFE.

[0062] The specific steps are as follows:

[0063] Step S1, the original graphite felt with a thickness of 2 mm and a size of 2*4 cm was cleaned with anhydrous ethanol and deionized water and dried to remove impurities;

[0064] Step S2, a catalyst solution was prepared: CB was 0.3 g, PTFE was 0.955 mL, isopropyl alcohol was 1.5 mL, deionized water was 30 mL, and ultrasonic mixing was performed for 10 min to obtain a first catalyst solution;

[0065] Step S3, the pretreated graphite felt substrate obtained in step S1 was put into the first catalyst solution, and after ultrasonic immersion for 30 min, it was dried at 60℃ to obtain a graphite felt electrode;

[0066] Step S4, the graphite felt electrode was put into a muffle furnace and annealed and calcined at 350℃ for 40 min to obtain a graphite felt cathode material CB-PTFE.

[0067] The graphite felt cathode materials prepared in Examples 1-3 have similar microstructures and chemical properties. Taking Example 1 as an example for description.

[0068] 1, Micro-morphology characterization

[0069] Field emission scanning electron microscopy (SEM) was used to characterize the morphology of GF, CB-PTFE and SDS-CB-PTFE.

[0070] Reference Figure 1 GF presents a three-dimensional network structure composed of carbon fibers, and the surface is clean, smooth and free of impurities. The surface of the modified GF becomes rough, and a large amount of blocky substances are embedded in the fiber pores. Compared with CB-PTFE, the surface of the SDS-CB-PTFE cathode with pore-forming agent has a large number of pores and defects, which provides more active sites for the reduction reaction of O2 on the surface of the cathode.

[0071] 2. BET test

[0072] N2 adsorption-desorption test was performed on GF, CB-PTFE and SDS-CB-PTFE by N2 adsorption-desorption instrument, and specific surface area and pore size distribution analysis were performed.

[0073] Reference Figures 2a-2c From the N2 adsorption-desorption curve, it can be seen that the unmodified GF hardly adsorbs N2, the inflection point of the CB-PTFE curve is closer to the high pressure end, indicating that there are a large number of small pores in the material; the inflection point of the SDS-CB-PTFE curve is closer to the low pressure end, indicating that there are a large number of large pores in the material. The addition of pore-forming agent effectively increases the number of large pores, resulting in a decrease in specific surface area. Larger three-dimensional mesoporous structure is more conducive to the diffusion of O2 in the pore and the combination with the active sites on the surface of the catalyst, thereby promoting the occurrence of the reaction of electrocatalytic generation of H2O2 in the cathode.

[0074] 3. Experiment of electrocatalytic generation of H2O2

[0075] Reference Figures 3a-3b By comparing the H2O2 production of CB-PTFE and SDS-CB-PTFE cathodes, it is found that the H2O2 production of the modified electrode with pore-forming agent SDS is significantly improved, and the H2O2 production is as high as 1200 mg / L at 60 min. At the same time, the use of organic pore-forming agent SDS can significantly improve the current efficiency (CE) and improve the utilization rate of electric energy.

[0076] 4. Effect of different current densities on H2O2 production of SDS-CB-PTFE

[0077] Reference Figures 4a-4b When the current density is 6.25 mA / cm 2 , 12.50 mA / cm 2 , 18.75 mA / cm 2 , and 25.00 mA / cm 2 , the H2O2 production is 319 mg / L, 615 mg / L, 1149 mg / L, and 1195 mg / L, respectively. With the increase of current density, the H2O2 production also increases. By fitting analysis of the relationship between H2O2 production and current density, it is found that when the current density increases from 6.25 mA / cm 2 to 18.75 mA / cm 2、 , the H2O2 production increases significantly, and when the current density increases from 18.75 mA / cm 2 to 25.00 mA / cm 2 , the H2O2 production increases less. It is indicated that when the current density increases to a certain extent, it is no longer the main factor limiting the increase of H2O2 production.

[0078] 5. SDS-CB-PTFE H2O2 production at long time operation and SDS-CB-PTFE reusability

[0079] Reference Figures 5a-5b The long time continuous power running performance of SDS-CB-PTFE cathode was tested. At the current density of 25.00 mA / cm 2 Under the condition, it was found that the SDS-CB-PTFE cathode produced H2O2 accumulation of up to 3571 mg / L within 270 min without any additional air or oxygen. The H2O2 accumulation did not show significant decrease in 350 min continuous operation. Moreover, it was reported that the use of SDS-CB-PTFE in long time continuous power running, the pore structure of which can effectively maintain the combination of electrode surface and air, so as to realize the continuous generation of high concentration H2O2.

[0080] The continuous reusability test of SDS-CB-PTFE cathode found that the H2O2 production of SDS-CB-PTFE cathode would decrease slightly in continuous reuse. But after simple and rapid drying treatment, the H2O2 production of SDS-CB-PTFE cathode can be effectively restored to the original level, and after 20 times of continuous repeated operation, the SDS-CB-PTFE cathode still stably maintains the original high H2O2 production.

[0081] The H2O2 production of SDS-CB-PTFE cathode of the present application and the similar material reported in the prior art at the current density of 25.00 mA / cm 2 Under the condition, the comparison of H2O2 production is shown in Table 1:

[0082] Table 1.

[0083]

[0084] Document 1: Polymethylhydrosiloxane-modified gas-diffusion cathode for more efficient and durable H2O2 electrosynthesis in the context of water treatment, Pan Xia, Lele Zhao, Xi Chen, Zhihong Ye. DOI: 10.1016 / j.apcatb.2023.123467.

[0085] As shown in Table 1, the SDS-CB-PTFE graphite felt cathode material provided by the present application realizes the improvement of H2O2 production capacity.

[0086] In order to better illustrate the application effect of the graphite felt cathode material of the present application, the present inventors have conducted the following research:

[0087] Example 4

[0088] The present embodiment provides an electro-Fenton system.

[0089] Reference Figure 6 The electro-Fenton system of the present embodiment includes an electrochemical system and a solar photovoltaic panel. Commercially purchased solar photovoltaic panels are used as the driving force, 4 solar photovoltaic panels are electrically connected in series, and then electrically connected in series with the electrochemical system. The cathode chamber of the electrochemical system is provided with a graphite felt cathode material electrode prepared in Example 1, and the anode chamber is provided with a ruthenium-iridium electrode. With the solar photovoltaic panel as the power supply, it is placed in a place directly exposed to sunlight, and air is used as the oxygen source, so that the cathode can continuously produce H2O2.

[0090] Example 5

[0091] Research on the catalytic degradation of tetracycline hydrochloride and rhodamine B by using the electro-Fenton system provided in Example 4.

[0092] Wastewater containing 30 mg / L of organic pollutants tetracycline hydrochloride (TC) is added to the cathode chamber and the anode chamber of the electro-Fenton system, respectively, to investigate the degradation effect.

[0093] Reference Figures 7a-7b Commercially purchased solar photovoltaic panels are used as the driving force, 4 photovoltaic panels are connected in series, and the current reaches a maximum of 100 mA when the natural light intensity is 108273 LUX. Under this condition, the TC degradation rate in the anode chamber can reach 74% and the TC degradation rate in the cathode chamber can reach 93% after running for 180 min.

[0094] After the cathode catalyst material is used for 6 cycles, the degradation rate of TC is still as high as 88%.

[0095] Wastewater containing 50 mg / L of organic pollutants rhodamine B (RhB) is added to the cathode chamber of the electro-Fenton system to investigate the degradation effect.

[0096] Reference Figure 7c Commercially purchased solar photovoltaic panels are used as the driving force, 4 photovoltaic panels are connected in series, and the current reaches a maximum of 100 mA when the natural light intensity is 108273 LUX. Under this condition, it is found that RhB is rapidly degraded to 99% within 60 min.

[0097] The above-mentioned aspects not covered by the present application are applicable to the prior art.

[0098] Although some specific embodiments of the present application have been described in detail by way of example with reference to the drawings, it is to be understood that the above examples are intended to be illustrative only and are not intended to limit the scope of the present application, and that various modifications and changes can be made by those skilled in the art to the particular embodiments described without departing from the spirit and scope of the present application. It is intended that the scope of the present application be limited only by the broadest interpretation of the appended claims to be accorded under 35 U.S.C. § 112.

Claims

1. A method of producing a graphite felt cathode material, characterized by, Comprise the following specific steps: S1, pretreatment of graphite felt; the original graphite felt is cleaned with anhydrous ethanol and deionized water to remove impurities, and dried for standby; S2, preparation of catalyst solution: a certain amount of carbon black, polytetrafluoroethylene, isopropyl alcohol is added to deionized water, and ultrasonic mixing is uniformly obtained to obtain a first catalyst solution; the mass volume ratio of carbon black, polytetrafluoroethylene, isopropyl alcohol and deionized water is (0.3~1.5) g : (0.5~5) mL : (1~5) mL : (30~150) mL; S3, adding sodium dodecyl sulfonate to the first catalyst solution obtained in step S2 to obtain a second catalyst solution; The adding amount of sodium dodecyl sulfonate is (0.1~1) g : (0.3~1.5) g in mass ratio of carbon black; S4, the pretreated graphite felt substrate obtained in step S1 is put into the second catalyst solution obtained in step S3, ultrasonic immersion and drying to obtain a graphite felt electrode; S5, the graphite felt electrode obtained in step S4 is annealed and calcined at high temperature to obtain a graphite felt cathode material, and the annealing and calcining temperature is 340~360 ℃, and the calcining time is 40~60 min.

2. The production method according to claim 1, characterized by, In step S4, the ultrasonic immersion time is 25~30 min; the drying temperature is 60~80 ℃.

3. The production method according to any one of claims 1 to 2, characterized by, In step S1, the pretreatment process is: cutting the graphite felt raw material into 4~10 cm2 size, cleaning with anhydrous ethanol and deionized water and drying.

4. A graphite felt cathode material, characterized by, The preparation method is prepared by using any one of claims 1-3.

5. The electro-Fenton system comprising the graphite felt cathode material of claim 4.

6. The application of the graphite felt cathode material of claim 4 in situ degradation of organic pollutants.

7. A method for degrading an organic contaminant in situ, characterized by, The graphite felt cathode material of claim 4 is used as the cathode, the ruthenium iridium electrode is used as the anode, the solar photovoltaic panel is connected with the electrochemical reaction device, the wastewater containing organic pollutants is added into the cathode chamber and the anode chamber respectively, and the degradation of the organic pollutants is realized by anode oxidation and cathode generated H2O2.

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