CN113754020A - Adsorption enhanced electric Fenton cathode material and preparation method thereof - Google Patents
Adsorption enhanced electric Fenton cathode material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to an adsorption enhanced electric Fenton cathode material and a preparation method thereof. The sandwich-type hierarchical pore composite fiber electrode is designed and prepared by utilizing a layer-by-layer self-assembly method through regulation and control of an electrostatic spinning process and a heat treatment process. The outer layer of the electrode is an iron-based porous carbon fiber composite layer, and the middle layer of the electrode is composed of a gas diffusion layer containing a low-dimensional carbon material and a cerium-based porous carbon fiber composite layer in an alternating mode. The electro-Fenton cathode prepared by the method can effectively avoid the problem that the existing three-dimensional electrode is lack of a catalytic site due to the excessive use of a binder and a conductive agent, and can be used for reducing O2Even not through O2Increase electricity generation H2O2The performance and the activity of electro-Fenton catalysis, and has good adsorption and enrichment effects on pollutants in a water body.
Description
Technical Field
The invention belongs to the technical field of environmental functional materials and electric Fenton water treatment, and particularly relates to a preparation method and application of an adsorption enhanced electric Fenton cathode material.
Background
In recent years, with the progress of society and the development of industry and agriculture, the water environment is seriously polluted, and various emerging pollutants, particularly pollutants difficult to degrade, are widely detected in the water environment. Although many of these contaminant residues in water bodies are still present at trace levels, they can pose serious hazards to the ecosystem and human health through constant accumulation and food chain transmission. Therefore, how to remove the pollutants efficiently, timely and economically has become one of the social hotspots which need to be solved urgently.
At present, the adsorption method has obvious advantages in the aspect of treatment of low-concentration degradation-resistant wastewater due to the advantages of simple and convenient operation, economy, practicability and the like, but the method cannot realize the complete removal of pollutants and has the problems of regeneration of an adsorbent and the like. In addition, the cathodic electro-Fenton method also has great development potential in the aspect of treatment of refractory wastewater due to the advantages of strong oxidizability and non-selectivity, but the strong-oxidizability free radicals (such as. OH) generated by the method have short half-life period, and can be consumed by non-selectively reacting with other substances in a water body before contacting and reacting with target pollutants, so that the utilization rate of the free radicals is low, especially for low-concentration wastewater. If the two methods can be organically combined, a degradation system for adsorbing and enhancing the cathode electro-Fenton is constructed, and the efficient degradation of pollutants can be expected to be realized.
In the cathodic electro-Fenton system, the development of cathode materials is crucial. The electro-Fenton cathode which is currently in great interest mainly comprises a gas diffusion electrode and a three-dimensional porous electrode. A gas diffusion electrode, for example, CN109809531A, "a method for preparing and regenerating an iron-complexing type carbon film gas diffusion electrode applied to an electro-Fenton system", Orlando Garcia-Rodriguez et al (electrochemical Acta 2018, 276, 12-20) and Qianhong Zhu et al (ACS appl. Energy Mater. 2019, 2, 7972-. And because the pore structure is single, the gas diffusion channel is easy to be buried along with the migration of the electrolyte in the use process, and the like, and the expansion application of the porous structure is limited due to the complexity of the structure. The three-dimensional porous electrode also has higher specific surface area and conductivity, and the three-dimensional structure solves the problems of low yield and low rate caused by the two-dimensional electrode structure to a certain extent, and effectively improvesThe mechanical property of the electrode is also more beneficial to realizing the regeneration of the catalyst on the cathode. However, the preparation process is complicated, and the use of binder or conductive agent may cause the deficiency of catalytic sites, such as Hongying Zhao et al (appl. cat. b: environ. 2012, 125, 120-127), patent CN104058484B "three-dimensional porous membrane electrode for generating hydrogen peroxide by electro-Fenton cathode and preparation process thereof", patent CN106219684A "electro-Fenton reactor and reaction method for treating organic wastewater", and patent CN105129925A "apparatus and electrode manufacturing method for treating restaurant wastewater by using oxygen cathode electro-Fenton". Plus O2The mass transfer efficiency in water is low, and the cathode generates H in situ2O2Are subject to limitations, such as Junkun An et al (Water Res. 2019, 164, 114933), Zhangweihao Pan et al (appl. Catal. B: Environ. 2018, 237, 392-. In addition, most of the electric Fenton cathodes, such as the nonacobalt octasulfide/partially graphitized carbon (Co 9S 8/paratly-graphitized carbon, Co9S 8/PGC) composite cathode (electrochemical Acta 2016, 213, 341- "350") prepared by Yuhui Lin et al and the three-dimensional macroporous aerogel cathode (J Hazard Mater, 2018, 341, 128- "137") prepared by Shulong Wen et al, have very limited adsorption performance, which is not favorable for the adsorption and enrichment of trace pollutants in water.
The electrostatic spinning technology is the only method which can directly and continuously prepare the polymer nano-fiber at present, and is one of the nano-fiber manufacturing technologies with the most industrialization potential. The technology has unique advantages in the aspects of regulation and control of material morphology and pore structure, load modification of nano particles, construction of three-dimensional network structure and the like. In order to overcome the defects of the prior art, the invention prepares an adsorption enhanced electric Fenton cathode material by means of an electrostatic spinning technology and a heat treatment method, and realizes the efficient degradation of refractory wastewater (especially low concentration) by utilizing the adsorption enhanced electric Fenton cathode material.
Disclosure of Invention
The invention aims to solve the problem of H generation of the conventional Fenton cathode2O2Low yield, low electro-Fenton catalytic capability, poor adsorption performance and mechanical performance, easy blockage of micropores and the likeThe method solves the problem that a large amount of binder or conductive agent is used in the preparation process to cause the loss of catalytic sites and the like, and provides the adsorption enhanced electric Fenton cathode material and the preparation method thereof.
The technical scheme adopted by the invention for achieving the purpose is as follows.
A preparation method of a three-dimensional adsorption enhanced electric Fenton cathode material comprises the following steps: the sandwich-type adsorption enhanced electro-Fenton cathode is prepared by adopting an electrostatic spinning technology and a heat treatment method through layer-by-layer self-assembly. At present, most three-dimensional porous electrodes mainly adopt a single-stage pore structure, and the chemical components of all parts are relatively uniform. The electrode breaks through the limitation of single pore structure in the traditional single-stage pore electrode, and rich multi-stage pore structures (including micropores, mesopores and macropores) are regulated and controlled; the whole electrode is in a heterogeneous sandwich structure, and the middle layer is mainly formed by interweaving a gas diffusion layer containing a low-dimensional carbon material and a cerium-based porous carbon fiber composite layer; the outer surface layer is an iron-based porous carbon fiber composite layer. The method specifically comprises the following steps:
step 1: and preparing spinning solutions of the layers.
Outer layer (iron-based fiber layer) spinning solution a: PAN is used as a carbon source, an appropriate amount of iron-based material is mixed, PMMA is added to be used as a pore-forming agent, the mixture is dissolved in DMF solvent in sequence, and the mixture is stirred uniformly to obtain an outer-layer electrostatic spinning precursor solution A;
inner layer (gas diffusion layer containing low-dimensional carbon material) spinning solution B: PAN is used as a carbon source, an appropriate amount of low-dimensional carbon material is mixed, an appropriate amount of PMMA is added to be used as a pore-forming agent, the mixture is sequentially dissolved in a DMF solvent, and the mixture is uniformly stirred to obtain an inner layer electrostatic spinning precursor solution B;
inner layer (cerium-based composite fiber layer) spinning solution C: PAN is used as a carbon source, a proper amount of cerium-based material is mixed, a proper amount of PMMA is added to be used as a pore-forming agent, the materials are sequentially dissolved in DMF solvent, and the mixture is uniformly stirred, so that inner-layer electrostatic spinning precursor liquid C is obtained.
Step 2: electrostatic spinning composite fiber
Respectively injecting the prepared electrostatic spinning precursor solution into an injector, and obtaining the sandwich type composite fiber through layer-by-layer self-assembly by adjusting the spinning voltage to be 15-25 kV, the spinning speed to be 0.5-1.5 mL/h and the receiving distance to be 10-20 cm. The middle layer of the three-dimensional fiber material is alternately spun by inner layer electrostatic spinning precursor liquid B and inner layer electrostatic spinning precursor liquid C according to the volume ratio of 1:1, and the thickness of the middle layer is approximately 5.00-7.00 mm; the outer two layers each have a thickness of about 0.15 to 0.20 mm.
And step 3: heat treatment process
Pre-oxidizing the three-dimensional composite fiber material at 200-250 ℃ for 1-2 h in the air atmosphere, then heating to 700-1000 ℃ at the heating rate of 5-10 ℃/min in the nitrogen or argon atmosphere, preserving the heat for 1-2 h, and naturally cooling to room temperature to obtain the sandwich-type adsorption enhanced electric Fenton cathode.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the invention, by means of an electrostatic spinning technology and a heat treatment method, PAN-based porous carbon fiber is used as a carrier, and iron-based nano particles, cerium-based nano particles, a low-dimensional carbon material and the like are respectively loaded on porous carbon fibers of each layer, so that no binder or conductive agent is required to be added in the whole preparation process, the preparation method is more environment-friendly and rapid, and industrialization is easy to realize.
The cerium-based material doped in the invention has certain storage and release of O due to lattice oxygen defects2Function of relieving O caused by increase in thickness of the electrode2Insufficient concentration, and improved electricity generation2O2The performance of (c). The presence of oxygen vacancy defects also contributes to improved electro-Fenton catalytic activity.
The addition of the PMMA, the low-dimensional carbon material and other pore-forming agents enables the cathode material to have a larger specific surface area and a rich and developed hierarchical pore structure, and provides more adsorption and catalytic active sites. The outer layer of the electrode is mainly macroporous and mesoporous, which is beneficial to O2And the migration of the electrolyte and oxidant; the middle layer is distributed with a large amount of mesopores and micropores mainly comprising O due to the addition of the cerium-based material and the low-dimensional carbon material2The reduction reaction of (2) provides a reaction site, etc. In addition, the addition of the low-dimensional carbon material also effectively improves the mechanical property and the conductivity of the electrode.
The structure of the electrode in the present invention has heterogeneity (packet)Including outer and intermediate layers) between which the advantages of each component can be integrated to provide a synergistic enhancement effect, thereby enhancing the electrogenesis H2O2Yield and electro-Fenton catalytic performance. The middle layer is a gas diffusion layer which is beneficial to promoting O22 electron reduction reaction to generate H2O2(ii) a The outer surface layer is an iron-based porous carbon fiber composite layer, has excellent electro-Fenton catalytic characteristic and can immediately catalyze H generated by in-situ online electricity2O2Generating strong oxidizing free radicals such as OH, improving the utilization efficiency of the free radicals and accelerating the degradation process of pollutants.
The electric Fenton cathode prepared by the invention can realize enrichment and concentration of pollutants in a water body by virtue of adsorption performance, then degrade and mineralize the enriched pollutants by virtue of free radicals generated in situ in a system, and meanwhile, the regeneration of adsorption active sites is realized, so that the aim of recycling for many times is fulfilled.
Drawings
Fig. 1 is a schematic structural diagram of a three-dimensional adsorption enhanced electro-Fenton cathode material of the present invention.
Fig. 2 is a schematic diagram of a process for manufacturing a three-dimensional adsorption enhanced electro-Fenton cathode material according to the present invention.
Fig. 3 is an SEM cross-sectional view of the electro-Fenton cathode material prepared in example 1.
Fig. 4 is an SEM cross-sectional view of the base fiber in the electrode material prepared in example 1.
FIG. 5 shows N of the electro-Fenton cathode material prepared in example 12Adsorption and desorption isotherms.
Fig. 6 is a BJH pore size distribution diagram of the electro-Fenton cathode material prepared in example 1.
FIG. 7 shows N of the electro-Fenton cathode material prepared in example 22Adsorption and desorption isotherms.
Fig. 8 is a BJH pore size distribution plot of the electro-Fenton cathode material prepared in example 2.
Fig. 9 shows the damaged cerium-based porous carbon fiber electrode.
Detailed Description
The following will explain in detail a new method for three-dimensionally adsorbing and enhancing an electric Fenton cathode material (FIG. 1) according to the present invention with reference to specific embodiments.
Example 1 was carried out:
using PAN, PMMA, CNTs, Fe (NO)3)3And cerium acetate as raw materials, and preparing the three-dimensional adsorption enhanced electric Fenton electrode material by an electrostatic spinning technology and a heat treatment method (as shown in figure 2):
(1) preparing spinning solution of each layer
Outer layer spinning solution A: 7% PAN as carbon source, 1% Fe (NO) was mixed3)3Adding 6% of PMMA as a pore-forming agent, dissolving in DMF solvent in sequence, and stirring uniformly to obtain an electrostatic spinning precursor solution A;
the inner layer spinning solution B: mixing 1% CNTs with 7% PAN as a carbon source, adding 6% PMMA as a pore-forming agent, sequentially dissolving in a DMF solvent, and uniformly stirring to obtain an inner layer electrostatic spinning precursor solution B;
inner layer spinning solution C: and (3) taking 7% PAN as a carbon source, mixing 2% cerium acetate, adding 6% PMMA as a pore-forming agent, dissolving in DMF solvent in sequence, and stirring uniformly to obtain an inner layer electrostatic spinning precursor solution C.
(2) Electrostatic spinning composite fiber
Respectively injecting the prepared electrostatic spinning precursor liquid into an injector, and preparing the sandwich type composite fiber material by regulating the spinning voltage to be 18 kV, the spinning speed to be 1.5 mL/h and the receiving distance to be 13 cm through a layer-by-layer self-assembly technology. The middle layer of the three-dimensional fiber material is formed by alternately spinning an inner layer electrostatic spinning precursor solution B and an inner layer electrostatic spinning precursor solution C according to the volume ratio of 1:1, and the thickness of the middle layer is approximately 5.00 mm; the outer two layers each have a thickness of about 0.15 mm.
(3) Heat treatment process
Pre-oxidizing the three-dimensional composite fiber material at 250 ℃ for 2 h in the air atmosphere, then heating to 1000 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, preserving the heat for 1.5 h, and naturally cooling to room temperature to obtain the sandwich-type adsorption enhanced electro-Fenton cathode material.
Three-dimensional products made by the method of the inventionThe adsorption enhanced electro-Fenton electrode has a special structure of a hollow multi-stage hole, and the SEM of the obtained sample is shown in figures 3-4. By N2The results of the adsorption and desorption tests are shown in fig. 5, and the specific surface area of the electrode obtained by the analysis by the BET method is about 456 m/g. Combining BJH pore size analysis (FIG. 6) and SEM image, the electrode material has abundant pore structure including micropores (<2nm, mesopores (2-50 nm) and macropores (2-50 nm)>50 nm). Wherein the volume of the micro-pores is 0.217 cm3Per g, the mesoporous volume is 0.478 cm3(ii)/g, average pore size of about 7.45 nm; the macropores are from the hollow pipe structure in the fiber and the gaps existing between the fibers, and are mainly distributed on the outer layer of the electrode.
Example 2 was carried out:
using PAN, PMMA, CNTs, Fe2O3And CeO2The three-dimensional adsorption enhanced electric Fenton electrode material is prepared by an electrostatic spinning technology and a heat treatment method as raw materials:
(1) preparing spinning solution of each layer
Outer layer spinning solution A: dissolving 8% PAN as a carbon source and 4% PMMA as a pore-forming agent in a DMF solvent; taking 0.6 percent of Fe2O3Ultrasonically dispersing in a DMF solvent, mixing the two and uniformly stirring to obtain an electrostatic spinning precursor solution A;
the inner layer spinning solution B: mixing 1% CNTs with 8% PAN as a carbon source, adding 4% PMMA as a pore-forming agent, dissolving in DMF solvent in sequence, and stirring uniformly to obtain an inner layer electrostatic spinning precursor solution B;
inner layer spinning solution C: dissolving 8% PAN as a carbon source and 4% PMMA as a pore-forming agent in a DMF solvent; taking 1% CeO2And ultrasonically dispersing the nano particles in a DMF solvent, mixing the nano particles and the DMF solvent, and uniformly stirring to obtain the inner-layer electrostatic spinning precursor solution C.
(2) Electrostatic spinning composite fiber
Respectively injecting the prepared electrostatic spinning precursor solution into an injector, and adjusting the spinning voltage to be 18 kV, the spinning speed to be 1.5 mL/h and the receiving distance to be 13 cm, so as to obtain the sandwich-type composite fiber material by a layer-by-layer self-assembly technology. The middle layer of the three-dimensional fiber material is alternately spun by inner layer electrostatic spinning precursor liquid B and inner layer electrostatic spinning precursor liquid C according to the volume ratio of 1:1, and the thickness of the middle layer is approximately 5.60 mm; the outer two layers each have a thickness of about 0.17 mm.
(3) Heat treatment process
Pre-oxidizing the three-dimensional composite fiber material at 250 ℃ for 1.5 h in the air atmosphere, then heating to 800 ℃ at a heating rate of 5 ℃/min in the nitrogen atmosphere, preserving heat for 2 h, and naturally cooling to room temperature to obtain the sandwich-type adsorption enhanced electro-Fenton cathode material.
The three-dimensional adsorption enhanced electric Fenton electrode prepared by the method is composed of N2The absorption-desorption analysis (figure 7) and the BJH pore size analysis (figure 8) show that the electrode material has a special structure of multi-level pores and micropores (<2nm, mesopores (2-50 nm) and macropores (2-50 nm)>50 nm), the specific surface area is about 438 m/g. Wherein the micropore volume is 0.141 cm3(g) the mesoporous volume is 0.317 cm3(ii)/g, average pore size of about 12.5 nm; the macropores are from the hollow pipe structure in the fiber and the gaps existing between the fibers, and are mainly distributed on the outer layer of the electrode.
Example 3 of implementation:
in order to evaluate the adsorption of the electrode in cooperation with the oxidation performance of the electro-Fenton, graphite is used as an anode, a three-dimensional adsorption enhanced electro-Fenton cathode material (example 1) is used as a cathode, the distance between polar plates is 3 cm, the oxygen passing rate of the cathode is 0.02L/min, and 0.05M Na is added2SO4The solution is used as electrolyte, an electric Fenton reactor is constructed and used for degrading the beta-lactam antibiotic wastewater. The whole degradation process adopts an intermittent operation mode, namely, the antibiotics wastewater is pre-adsorbed for a period of time under the condition that a power supply is not switched on, and then the power supply is switched on to start the electric Fenton reaction to remove the antibiotics wastewater. And compared to the degradation effect in the pure adsorption case and in the direct start electro-Fenton reaction.
The experimental results show that: the electrode material has a good adsorption effect on antibiotics in a water body, adsorption saturation is achieved within 60min, and the maximum adsorption capacity is about 297 mg/g. When the pH value is 4-5, the current density j is 4 mA/cm2Then, pre-adsorbing for 20 min under the condition of not switching on the power supply, and then switching onThe power supply starts the electro-Fenton reaction and degrades the beta-lactam antibiotic wastewater, and the removal rate of TOC in the wastewater exceeds 95.0 percent after 120 min of reaction. The removal efficiency of the system is obviously higher than that of a pure Fenton degradation system.
Example 4 of implementation:
in order to evaluate the mechanical properties and recyclability of the three-dimensional adsorption enhanced electric Fenton cathode material, the material was compared with an un-layered blended carbon fiber electrode and a pure cerium-based porous carbon fiber electrode.
(1) Non-layered blended carbon fiber electrode
7% PAN as carbon source, 1% Fe (NO) was mixed3)3Adding 6% of PMMA (polymethyl methacrylate) as a pore-forming agent into 1% of CNTs and 2% of cerium acetate, dissolving the mixture in a DMF (dimethyl formamide) solvent in sequence, and uniformly stirring to obtain an electrostatic spinning precursor solution; and injecting the prepared electrostatic spinning precursor solution into an injector, and performing electrostatic blending by adjusting the spinning voltage to be 18 kV, the spinning speed to be 1.5 mL/h and the receiving distance to be 13 cm to obtain the composite fiber material. Pre-oxidizing the obtained composite fiber material at 250 ℃ for 2 h in the air atmosphere, then heating to 1000 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, preserving the heat for 1.5 h, and naturally cooling to room temperature to obtain the carbon fiber electrode which is not subjected to layered blending.
During the spinning process, PAN and Fe (NO) are found3)3The CNTs, the cerium acetate and the PMMA are mixed together for spinning, so that a needle head is easily blocked, the three-dimensional composite fiber material is difficult to obtain, and the specific surface area of the material after heat treatment is obviously reduced.
(2) Cerium-based porous carbon fiber electrode
Mixing 7% PAN (polyacrylonitrile) serving as a carbon source with 2% cerium acetate, adding 6% PMMA serving as a pore-forming agent, dissolving in DMF (dimethyl formamide) solvent in sequence, and stirring uniformly to obtain an electrostatic spinning precursor solution; and injecting the prepared electrostatic spinning precursor solution into an injector, and performing electrostatic spinning to obtain the cerium-based porous carbon fiber material with the thickness of about 5.30mm by adjusting the spinning voltage to be 18 kV, the spinning speed to be 1.5 mL/h and the receiving distance to be 13 cm. Pre-oxidizing the obtained cerium-based porous carbon fiber material at 250 ℃ for 2 h in the air atmosphere, then heating to 1000 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, preserving the temperature for 1.5 h, and naturally cooling to room temperature to obtain the cerium-based porous carbon fiber electrode.
Graphite is taken as an anode, a three-dimensional adsorption enhanced electric Fenton cathode material (example 1) and a pure cerium-based porous carbon fiber electrode are respectively taken as cathodes, the distance between the polar plates is 3 cm, the oxygen introduction of the cathode is 0.02L/min, and 0.05M Na is added2SO4The solution is used as electrolyte, an electro-Fenton reactor is constructed and is used for repeated degradation experiments of the beta-lactam antibiotic wastewater. The whole degradation process adopts an intermittent operation mode, namely, the antibiotics wastewater is pre-adsorbed for a period of time under the condition that a power supply is not switched on, and then the power supply is switched on to start the electric Fenton reaction to remove the antibiotics wastewater. Under the same condition, after 120 min of reaction, the removal rates of the three-dimensional adsorption enhanced electric Fenton cathode material and the pure cerium-based porous carbon fiber electrode on TOC in the wastewater are respectively 95.0% and 67%. The removal capability of the three-dimensional adsorption enhanced electro-Fenton cathode material is stronger, and after 6 times of recycling, the TOC removal rate of the antibiotic wastewater is basically kept unchanged, the elution amount of iron ions in a water body is far lower than the limit value specified in the water quality standard of drinking water, and the elution amount of cobalt is even lower than the detection limit of an instrument. The cerium-based porous carbon fiber electrode has significantly poor mechanical properties (see fig. 9 for details), and is broken during the 2 nd recycling process.
Example 5:
to evaluate the doping of cerium oxide for increasing the electrical generation of H2O2The yield is influenced, and the gas diffusion electrode containing the low-dimensional carbon material and the gas diffusion electrode doped with the cerium oxide are used for generating H under the same condition2O2The amounts of (c) were compared.
(1) Gas diffusion electrode containing low-dimensional carbon material
Mixing 1% CNTs with 7% PAN as a carbon source, adding 6% PMMA as a pore-forming agent, dissolving in DMF solvent in sequence, and stirring uniformly to obtain an electrostatic spinning precursor solution; and injecting the prepared electrostatic spinning precursor solution into an injector, and obtaining the composite fiber material with the thickness of about 5.30mm after electrostatic blending by adjusting the spinning voltage to be 18 kV, the spinning speed to be 1.5 mL/h and the receiving distance to be 13 cm. Pre-oxidizing the obtained composite fiber material at 250 ℃ for 2 h in the air atmosphere, then heating to 1000 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, preserving the heat for 1.5 h, and naturally cooling to room temperature to obtain the gas diffusion electrode containing the low-dimensional carbon material.
(2) Gas diffusion electrode doped with cerium oxide
Preparing spinning solutions A and B respectively, injecting the prepared electrostatic spinning precursor solution into an injector respectively, and alternately spinning the electrostatic spinning precursor solution A and the electrostatic spinning precursor solution B according to the volume ratio of 1:1 by adjusting the spinning voltage to be 18 kV, the spinning speed to be 1.5 mL/h and the receiving distance to be 13 cm, wherein the spinning thickness is about 5.30 mm. Pre-oxidizing the obtained composite fiber material at 250 ℃ for 2 h in the air atmosphere, then heating to 1000 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, preserving the heat for 1.5 h, and naturally cooling to room temperature to obtain the cerium oxide doped gas diffusion electrode.
Spinning solution A: mixing 1% CNTs with 7% PAN as a carbon source, adding 6% PMMA as a pore-forming agent, dissolving in DMF solvent in sequence, and stirring uniformly to obtain an electrostatic spinning precursor solution A;
spinning solution B: and (3) taking 7% PAN as a carbon source, mixing 2% cerium acetate, adding 6% PMMA as a pore-forming agent, dissolving in DMF solvent in sequence, and stirring uniformly to obtain an electrostatic spinning precursor solution B.
Graphite is used as an anode, a gas diffusion electrode containing a low-dimensional carbon material and a gas diffusion electrode doped with cerium oxide are used as cathodes, the distance between the electrode plates is 3 cm, oxygen is introduced into the cathodes at 0.02L/min, and 0.05M Na is added2SO4The solution is used as electrolyte, an electric Fenton reactor is constructed, and H generated by adding cerium oxide to an electrode is researched2O2The influence of (c). The experimental result shows that H generated by the cerium oxide-doped gas diffusion electrode is generated after electrolysis for 120 min under the same condition2O2The concentration is significantly greater, about 340 mg/L, which is 20 mg/L higher than that of the undoped cerium oxide-containing low-vitamin carbon gas diffusion electrode.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A preparation method of a three-dimensional adsorption enhanced electric Fenton cathode material is characterized in that the three-dimensional adsorption enhanced electric Fenton cathode is different from an electrode material with a conventional homogeneous structure, is of a heterogeneous sandwich structure and comprises an outer layer and an intermediate layer, and the advantages of the layers are complementary and synergistic; the outer two layers are iron-based porous carbon fiber composite layers; the intermediate layer is formed by interweaving a gas diffusion layer containing a low-dimensional carbon material and a cerium-based porous carbon fiber composite layer.
2. The preparation method of the three-dimensional adsorption enhanced electric Fenton cathode material according to claim 1, characterized in that the electrode material has a hierarchical pore structure comprising micropores, mesopores and macropores; the pore diameters of the micropores are mainly distributed in the range of 0.8-1.5 nm, the pore diameters of the mesopores are mainly distributed in the range of 6-15 nm, and the approximate volume ratio of the micropores to the mesopores is 1: 4-1: 2; the micropores and mesopores are O2The electron reduction reaction providing site of (3); the macropore is mainly positioned on the outer layer of the electrode and is O2And the migration of the electrolyte and oxidant provides a pathway.
3. The preparation method of the three-dimensional adsorption enhanced electric Fenton cathode material according to claim 1, wherein the electrode material has adsorption enrichment and self-cleaning properties, under the condition that a power supply is not connected, pollutants in a water body can be enriched and concentrated by virtue of the adsorption, then the enriched pollutants are degraded and mineralized by starting an electric Fenton reaction through the power supply, and meanwhile, the adsorption and catalytic active sites on the electrode are regenerated, so that the purpose of recycling for many times is achieved.
4. The method for preparing a three-dimensional adsorption enhanced electric Fenton cathode material according to claim 1, wherein the mass fraction of cerium oxide in the electrode material is approximately 4-8%, which can relieve O caused by the increase of the thickness of the electrode to a certain extent2Insufficient concentration, and increased electricity generation H2O2In turn, yield ofAvoid the reduction of the mechanical property of the electrode caused by the excessive doping of the cerium-based material.
5. The preparation method of the three-dimensional adsorption enhanced electric Fenton cathode material according to claim 1, wherein the mass fraction of iron contained in the electrode material is only 0.1-0.5%, and the iron is uniformly fixed on the porous carbon fiber and arranged on the outer layer of the electrode, so that the problem of iron ion loss is effectively avoided while the electric Fenton catalytic efficiency is ensured.
6. The preparation method of the three-dimensional adsorption enhanced electric Fenton cathode material according to claim 1, wherein the electrode material is prepared by cross-mixing and electrospinning polymers by means of an electrospinning technology to realize close and alternate lamination between fibers, and no binder is added in the whole preparation process, and the preparation method specifically comprises the following steps:
(1) preparing a series of electrostatic spinning precursor solutions, and preparing a sandwich-type composite fiber material by layer-by-layer self-assembly by adopting an electrostatic spinning method;
(2) and (3) carrying out heat treatment on the sandwich type composite fiber material to prepare the three-dimensional adsorption enhanced electric Fenton cathode.
7. The preparation method of the three-dimensional adsorption enhanced electric Fenton cathode material according to claim 1, wherein the layer-by-layer self-assembly refers to a spinning sequence of: firstly, an outer layer electrostatic spinning precursor solution A, then an intermediate layer is alternately spun by an inner layer electrostatic spinning precursor solution B and an inner layer electrostatic spinning precursor solution C according to the volume ratio of 1:1, then the outer layer electrostatic spinning precursor solution A is still used, and finally a sandwich-type composite fiber material is obtained, wherein in the three-dimensional fiber material, the thicknesses of the outer two layers are respectively about 0.15-0.20 mm, and the thickness of the intermediate layer is about 5.00-7.00 mm;
the outer layer electrostatic spinning precursor solution A: polyacrylonitrile (PAN) is used as a carbon source, Polymethacrylate (PMMA) is used as a pore-forming agent, a proper amount of iron-based material is mixed, and N, N-Dimethylformamide (DMF) is used as a solvent;
the inner layer electrostatic spinning precursor solution B: PAN is used as a carbon source, PMMA is used as a pore-forming agent, a proper amount of novel low-dimensional carbon material is mixed, and DMF is used as a solvent;
the inner layer electrostatic spinning precursor solution C: PAN is used as a carbon source, PMMA is used as a pore-forming agent, a proper amount of cerium-based material is mixed, and DMF is used as a solvent.
8. The electrospinning precursor solution of claim 7, wherein the iron-based material is iron-based nanoparticles, preferably elemental iron, iron oxide, ferroferric oxide, copper ferrite and manganese ferrite, and various iron salts, preferably ferric chloride, ferrous chloride, ferric nitrate, ferric acetate or ferric sulfate.
9. The electrospinning precursor solution of claim 7, wherein the novel low-dimensional carbon material comprises graphene and carbon nanotubes.
10. The electrospinning precursor of claim 7, wherein the cerium-based material is a cerium-zirconium solid solution, cerium oxide nanoparticles, and various cerium salts, preferably cerium carbonate, cerium acetate, cerium nitrate, cerylamine nitrate, cerium sulfate, or cerium ammonium sulfate.
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