Iron-nickel composite three-dimensional porous electrode, preparation method thereof and application thereof in electro-fenton technology

Abstract

The application discloses a synthesis method of an electro-Fenton iron-nickel composite three-dimensional cathode and application thereof, and belongs to the fields of moldless direct writing technology, porous material preparation, electro-Fenton technology and material forming technology. The method is characterized in that: iron source, nickel source, nitrogen source and carbon source powders are stirred with water to form a slurry with certain fluidity, then the slurry is formed into a three-dimensional structure by using an extrusion type 3D printer, and then high-temperature heat treatment is performed under an ammonia atmosphere to form a Fe3NiN / FeS composite three-dimensional porous electrode; the electro-Fenton method has excellent effect on degradation of organic pollutants rhodamine B and tetracycline hydrochloride. In the three-dimensional electrode constructed by the method, a large amount of Fe 2+ ions participate in the electro-Fenton reaction, and Ni 0 is contained in the Fe3NiN, which can provide an additional reaction path for generation of H2O2 in the electro-Fenton reaction process, thereby improving the efficiency of the electro-Fenton reaction, and has important application value in the fields of electro-oxidation technology and water treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of direct ink writing technology, porous material preparation, electro-Fenton technology and material forming technology, and particularly relates to a Fe-Ni composite three-dimensional porous electrode, a preparation method thereof and application thereof in electro-Fenton technology. BACKGROUND

[0002] Direct ink writing 3D printing technology (DIW) is an additive manufacturing technology that can quickly manufacture objects with complex geometrical shapes. A three-dimensional model is designed by using computer drawing software, and a slurry / ink with shear deformation capability is deposited layer by layer by computer-controlled printing needle movement to form a three-dimensional object. DIW technology can replace printing needles of different sizes, and its accuracy mainly depends on the printing needle and the movement control of the three-dimensional platform, which can accurately control the printing accuracy and speed. Therefore, the geometry and size of the electrode can be controlled according to actual needs by using DIW technology, which can effectively reduce material loss and control experimental cost.

[0003] Iron-based transition metal sulfides and nitrides have attracted widespread attention in the field of catalysis due to their wide range of raw materials, high electrical conductivity, abundant redox active centers, excellent mechanical stability, excellent thermal stability and stable catalytic performance. As an advanced electro-oxidation technology, electro-Fenton technology has achieved outstanding results in water treatment. The core of the technology is that Fe 2+ reacts with H2O2 to generate ·OH, which attacks pollutants in water to degrade them. The performance of bimetallic catalysts in pollutant degradation has important research value. The present application constructs a FeS and Fe3NiN composite electrode material in order to improve the efficiency of electro-Fenton reaction. SUMMARY

[0004] The present application aims to provide a Fe-Ni composite three-dimensional porous electrode and a preparation method thereof and application thereof in electro-Fenton technology. The method prints a three-dimensional structure of a slurry containing an iron source, a nickel source, a nitrogen source and a carbon source, and generates a Fe3NiN / FeS composite three-dimensional porous electrode through a high-temperature heat treatment in an ammonia atmosphere. The three-dimensional porous electrode has good electrical conductivity and chemical stability, and can be applied in the field of water pollution control.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] A preparation method of a Fe-Ni composite three-dimensional porous electrode, the method comprising the following steps:

[0007] (1) Raw material preparation: take iron sulfate powder as the iron source, nickel sulfate as the nickel source, and melamine powder and chitosan powder as the carbon source and the nitrogen source;

[0008] (2) Slurry preparation: iron sulfate powder, nickel sulfate powder, melamine powder, chitosan powder and appropriate amount of deionized water are mixed, stirred until a certain fluidity and no obvious agglomeration to obtain a printing slurry;

[0009] (3) 3D printing: the obtained slurry is loaded into a barrel and a screw extrusion type 3D printer is used for three-dimensional molding to obtain a three-dimensional wood pile structure blank;

[0010] (4) Heat treatment: the three-dimensional wood pile structure blank obtained in step (1) is dried, and the sample after drying is subjected to high temperature heat treatment to cause redox reaction of the raw materials in the three-dimensional wood pile structure, thereby obtaining Fe3NiN / FeS composite three-dimensional structure, which is the iron-nickel composite three-dimensional porous electrode.

[0011] Preferably, in step (1), the viscosity of the chitosan is 100-200 mpa.s or 200-400 mpa.s.

[0012] Preferably, in step (2), the weight ratio of the iron sulfate powder, nickel sulfate powder, melamine powder and chitosan powder is (12-18):(1-2):3:1.5.

[0013] Preferably, in step (3), the substrate (base) needs to be preheated before printing, and the printing substrate is a glass plate with transparent tape adhered, and the preheating temperature is 40-50℃.

[0014] Preferably, in step (3), air pressure is applied to the barrel to make the slurry enter the screw extruder, and the slurry is extruded from the nozzle at a constant speed as the screw rotates, and the printer needle moves at a constant speed to print the three-dimensional wood pile structure blank; wherein: the applied air pressure is about 0.2-0.4 MPa, the screw extruder rotation extrusion ratio is 50-60%, and the printer needle moving speed is 800-1500 mm / min.

[0015] Preferably, in step (4), the high temperature heat treatment process is: first, exhaust ammonia for 0.5-1 h, then increase the temperature from room temperature to 750-850℃ at a rate of 3-8℃ / min and keep for 2-5 hours; after the holding period ends, stop the ammonia flow after natural cooling to 150-250℃, and then natural cooling to room temperature to take out the electrode, wash and dry.

[0016] The electrode cleaning process is: the electrode is washed with deionized water and 95vol.% ethanol three times in turn; the drying process is drying in a blast drying oven at 40℃ for 3-5 hours.

[0017] The iron-nickel composite three-dimensional porous electrode is prepared by the above method, is a three-dimensional porous structure composed of FeS and Fe3NiN two phases, and carbon materials (elemental carbon and / or carbon compounds) are uniformly distributed in the inside and surface of the three-dimensional porous structure framework; wherein: FeS is used as the electrode main material to maintain the stability of the three-dimensional structure and provide Fe 2+ ion generation electro-Fenton reaction; the uniform distribution of carbon materials improves the conductivity of the electrode and enhances the mechanical properties of the three-dimensional structure; Fe3NiN is used as an ion conductor to accelerate electron transfer and provide Ni 0 participate in the electro-Fenton reaction.

[0018] The iron-nickel composite three-dimensional porous electrode is used as a cathode in the electro-Fenton technology.

[0019] The design idea of the present application is as follows:

[0020] In the composite material electrode constructed by the present application, FeS is used as the electrode main material to provide Fe 2+ participate in the electro-Fenton reaction; Fe3NiN has excellent electrical conductivity and contains Ni 0 in the system, the following reactions occur: Ni 0 + 2O2→ Ni 2+ + 2·O2 - provide superoxide radicals, increase the yield of H2O2, and thus effectively improve the efficiency of the electro-Fenton reaction.

[0021] Specifically, the redox reaction of iron sulfate, nickel sulfate and ammonia gas forms a Fe3NiN and FeS composite material, and the core of the electro-Fenton technology is Fe 2+ reacts with H2O2 to form ·OH to degrade macromolecular structures into small molecular structures or H2O and CO2, so it has important research value in the field of water treatment. Using iron sulfate, nickel sulfate, melamine and chitosan powder to mix and prepare slurry can provide nitrogen source inside the material, ensure that the inside and outside of the three-dimensional structure can fully react, and after the decomposition of the carbon source, a carbon layer or carbon material framework is formed in the three-dimensional structure, which can strengthen the structural stability and enhance the electrical conductivity of the three-dimensional electrode. And in the reaction process, due to the generation and flow of gas, pores will be formed inside and outside the three-dimensional electrode to form a three-dimensional porous structure connected to each other, which can expose more active sites, increase the reaction area and improve the reaction efficiency.

[0022] The advantages and beneficial effects of the present application are as follows:

[0023] 1. The present invention mixes iron source, nickel source, nitrogen source and carbon source powders in a ball mill, adds an appropriate amount of water and stirs them into a slurry that can be three-dimensionally formed, constructs a three-dimensional structure using a 3D printer, and performs high-temperature heat treatment under an ammonia atmosphere to cause the material to undergo an oxidation-reduction reaction to generate an Fe3NiN / FeS composite three-dimensional porous electrode. The three-dimensional porous electrode has good electrical conductivity and chemical stability and can be applied to the field of water pollution control, specifically as an electro-Fenton cathode material to remove pollutants. In addition, since the carbon material is widely and evenly present in the three-dimensional structure, the conductivity and stability of the three-dimensional electrode can be improved.

[0024] 2. The preparation method of the three-dimensional porous electrode of the present invention is simple, and the raw materials used are widely available and inexpensive, which can effectively reduce material costs in practical applications.

[0025] 3. The raw material powder used in the present invention will generate gas when reacting in an ammonia atmosphere, and pores will be formed inside and outside the three-dimensional structure to form a three-dimensional porous structure. Therefore, it can effectively increase the reaction area of ​​the material and expose more active sites. Compared with the two-dimensional planar electrode, it has a significant improvement. Therefore, the method of the present invention can be widely used in the preparation of electrode materials such as catalysis and energy storage.

[0026] 4. The three-dimensional porous electrode of the present invention has a significant removal effect on common water pollutants. The reaction process is: O2+2H + +2e - →H2O2;Fe 2+ +H2O2→Fe 3+ +·OH+OH - ; RH+·OH→R+H2O, where RH macromolecules contain pollutants and R is a small molecule substance or CO2. The electro-Fenton reaction does not produce secondary pollutants, and the content of iron and nickel ions in the water body during the reaction is extremely low. It is an environmentally friendly electrode material with important potential and wide application value.

[0027] 5. The slurry preparation method of the present invention allows for the selection of suitable materials to synthesize a three-dimensional electrode. This, combined with a heat treatment process, creates pores on the surface and interior of the three-dimensional electrode, thereby producing a three-dimensional porous electrode with both a macroscopic three-dimensional structure and a microscopic three-dimensional porous structure. The three-dimensional electrode synthesized in this manner has a larger specific surface area and higher porosity, effectively shortening the ion transport distance to increase reaction rate and reduce energy consumption. Furthermore, it has more active sites, contributing to improved performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the XRD result of the Fe3NiN / FeS composite electrode prepared after high-temperature heat treatment in ammonia in step (3) of Example 1-2.

[0029] Figure 2 These are optical photographs of the three-dimensional structure blanks printed with slurries containing different amounts of nickel sulfate in Examples 1-2 before and after heat treatment; wherein: (a) Example 1 blank before heat treatment; (b) Example 1 blank after heat treatment; (c) Example 2 blank before heat treatment; (d) Example 2 blank after heat treatment.

[0030] Figure 3 Field emission scanning electron microscope morphology and energy spectrum scanning photographs of the Fe3NiN / FeS composite three-dimensional porous electrode prepared in Examples 1-2; wherein: (a) Example 1; (b) Example 2.

[0031] Figure 4 These are the light absorption curves of the degradation experiment of 5 ppm RhB (Rhodamine B) using the two Fe3NiN / FeS composite three-dimensional porous electrodes prepared in Examples 1-2 using the electro-Fenton technique.

[0032] Figure 5 These are the experimental results of the degradation of 15 ppm TC-HCl in different water environments using the Fe3NiN / FeS composite three-dimensional porous electrode prepared in Example 3 and the electro-Fenton method.

[0033] Figure 6 The leakage of iron and nickel ions from the three-difficulty electrode in the electro-Fenton reaction of Example 3. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0035] The present invention comprises the following steps: uniformly mixing iron source, nitrogen source and carbon source powders in a ball mill and then taking them out; dissolving a nickel source in a mortar by adding an appropriate amount of deionized water; then adding the ball-milled powder and stirring to form a three-dimensionally formed slurry; and performing three-dimensional molding using an extrusion-type 3D printer to construct different three-dimensional structures; and then performing high-temperature heat treatment under an ammonia atmosphere. After the raw materials react, a two-phase composite electrode of Fe3NiN and FeS is generated. In addition, due to the participation and generation of gas in the reaction process, pores are formed inside and outside the three-dimensional electrode to form a three-dimensional porous electrode, exposing more reaction active sites and increasing the reaction area.

[0036] The iron source used is ferric sulfate powder, the nickel source is nickel sulfate powder, the nitrogen source is melamine powder, and the carbon source is chitosan powder. The viscosity of the chitosan powder is 100-200 mPa.s or 200-400 mPa.s, and all the chemicals used are analytically pure.

[0037] The cleaning and drying process in the following examples is as follows: the three-dimensional electrode is rinsed with deionized water and then with 95 vol.% ethanol three times in sequence; and the drying process is carried out in a forced air drying oven at 50° C. for 3-5 hours.

[0038] Example 1-2:

[0039] This example is to prepare a Fe3NiN / FeS three-dimensional porous electrode and use the electrode to degrade 5ppm RhB (Rhodamine B dye) using the electro-Fenton method. The specific process is as follows:

[0040] (1) 15 g of ferric sulfate powder, 3 g of melamine powder, and 1.5 g of chitosan powder were mixed in a ball mill for 4 hours and then taken out. 1 g or 2 g of nickel sulfate was placed in a mortar and an appropriate amount of deionized water was added and stirred to dissolve. Then, the ball-milled powder was added and stirred to form a slurry with a certain fluidity. The slurry was loaded into a barrel and prepared for printing. The composition of each raw material powder in the slurry is shown in Table 1.

[0041] Table 1

[0042] sample Ferric sulfate Nickel sulfate Melamine Chitosan Example 1 15g 1g 3g 1.5g Example 2 15g 2g 3g 1.5g

[0043] (2) The substrate was preheated to 50°C before printing, and the printing base was a glass plate with transparent tape attached. During printing, 0.4 MPa air pressure was applied to the barrel to allow the slurry to enter the screw extruder at a constant speed. As the screw rotated, the slurry was extruded from the nozzle at a constant speed, and the printer needle moved at a constant speed to print the three-dimensional wood pile structure blank; the screw extruder rotation extrusion ratio was set to 50%, and the printer needle movement speed was set to 1200 mm / min; the printed size of the three-dimensional wood pile structure was 1.2×1.2×0.6 cm.

[0044] (3) After printing, the obtained three-dimensional wood pile structure blank was placed in an oven and dried at 40°C for 4 hours, then placed in a tubular furnace and connected to ammonia, and the air was exhausted for 30 minutes, and then heated to 800°C at a heating rate of 5°C / min and kept warm for 3 hours. When it was naturally cooled to 200°C, the introduction of ammonia was stopped, and it was naturally cooled to room temperature and taken out. The three-dimensional electrode was rinsed with deionized water and 95vol.% ethanol three times in sequence, and placed in an oven and dried at 40°C for 5 hours to obtain an iron-nickel composite three-dimensional porous electrode (Fe3NiN / FeS composite electrode). The electrode size obtained after heat treatment was approximately 0.6×0.6×0.3cm.

[0045] The prepared electrode was used as cathode and platinum electrode as anode, and 5 ppm RhB (Rhodamine B dye) was degraded by electro-Fenton method.

[0046] Figure 1The XRD results for the Fe3NiN / FeS composite electrode prepared after high-temperature heat treatment in ammonia in step (3) are shown. The XRD results show that Examples 1-2, with varying amounts of nickel sulfate added, all form a two-phase structure of Fe3NiN and FeS (corresponding to the standard PDF card). The carbon source decomposes at 800°C to form a single carbon element uniformly distributed throughout the three-dimensional electrode skeleton, further enhancing the stability of the three-dimensional electrode structure and its conductivity.

[0047] Figure 2 The optical photos of the three-dimensional structure blank printed using nickel-iron sulfate slurry in step (3) before and after heat treatment reaction are shown. It can be seen that the three-dimensional structure after heat treatment maintains the original design structure and has good mechanical stability.

[0048] Figure 3 Field emission scanning electron microscope photos of Fe3NiN / FeS composite three-dimensional porous electrodes prepared by printing and heat treatment of slurries with different amounts of nickel sulfate added show that the electrodes are clearly distributed with extensive pores, which are caused by the generation of gas during the reaction and the reaction inside the material. The three-dimensional electrode maintains the original printed structure and has good structural stability.

[0049] Figure 4 This is the light absorption curve of the 5 ppm RhB degradation experiment using the electro-Fenton method. It can be seen that the two Fe3NiN / FeS electrodes prepared in Examples 1-2 have obvious degradation effects on RhB and do not produce other pollutants during the degradation process.

[0050] Example 3

[0051] This example is to prepare a Fe3NiN / FeS composite three-dimensional porous electrode and use the electro-Fenton method to degrade 15 ppm TC-HCl, i.e., tetracycline hydrochloride, an antibiotic. The specific process is as follows:

[0052] 1) 15 g of ferric sulfate powder, 5 g of melamine powder, and 1.5 g of chitosan powder were mixed in a ball mill for 4 hours. After removal, 1 g of nickel sulfate and an appropriate amount of deionized water were added to a mortar to dissolve the powder. The ball-milled powder was then added and stirred to form a slurry with a certain fluidity. The slurry was then loaded into a barrel for printing.

[0053] (2) Preheat the substrate to 45-50°C before printing. The printing base is glass with transparent tape attached. The air pressure is set to 0.4 MPa during printing so that the slurry enters the screw at a uniform speed. Set the printing speed and base rate for printing.

[0054] (3) After printing, the sample was placed in an oven and dried at 40°C for 4 hours, then placed in a tube furnace and infused with ammonia, evacuated for 30 minutes, and then heated to 800°C at a heating rate of 5°C / min and kept warm for 3 hours. When the temperature naturally cooled to 200°C, the introduction of ammonia was stopped, and the sample was taken out after natural cooling to room temperature. The three-dimensional electrode was rinsed with deionized water and 95 vol.% ethanol three times in sequence, and placed in an oven and dried at 40°C for 5 hours to obtain a Fe3NiN / FeS composite three-dimensional porous electrode.

[0055] (4) The prepared electrode was used as the cathode and the platinum electrode as the anode to degrade tetracycline hydrochloride (TC-HCl) in the water environment using the electro-Fenton method.

[0056] Figure 5 The results of the degradation experiment of 15ppm TC-HCI in different water environments (deionized water and tap water) using the electro-Fenton method are shown. It can be clearly seen that the TC-HCI concentration gradually decreases as the experiment progresses, and good degradation effects are achieved in different water environments. Fe3NiN / FeS, as the cathode material in the electro-Fenton method, has a wide range of degradation effects on common pollutants and has practical application value.

[0057] Figure 6 This is the leakage amount of iron and nickel ions of the electrode material in Example 3 during the electro-Fenton reaction. It can be seen that the content of iron and nickel ions in the water body is extremely low during the degradation reaction.

[0058] The present invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement made under the spirit and principle of the present invention shall be deemed to be within the protection scope of the present invention.

Claims

1. A method for preparing an iron-nickel composite three-dimensional porous electrode, characterized in that: The method comprises the following steps: (1) Raw material preparation: iron sulfate powder as the iron source, nickel sulfate as the nickel source, melamine powder and chitosan powder as the carbon source and nitrogen source; (2) Slurry preparation: Mix the iron sulfate powder, melamine powder and chitosan powder in a ball mill and take them out. Dissolve the nickel sulfate powder in a mortar with an appropriate amount of deionized water. Then add the ball-milled powder and stir until it has a certain fluidity and no obvious agglomeration to obtain the printing slurry. (3) 3D printing: the obtained slurry is loaded into a barrel and three-dimensionally formed using a screw extrusion 3D printer to obtain a three-dimensional wood pile structure blank; (4) Heat treatment: The three-dimensional wood pile structure blank obtained in step (1) is dried, and the dried sample is subjected to high-temperature heat treatment in an ammonia atmosphere to cause the raw materials in the three-dimensional structure to undergo an oxidation-reduction reaction, thereby obtaining the iron-nickel composite three-dimensional porous electrode.

2. The method for preparing the iron-nickel composite three-dimensional porous electrode according to claim 1, characterized in that: In step (1), the viscosity of the chitosan is 100-200 mPa∙s or 200-400 mPa∙s.

3. The method for preparing the iron-nickel composite three-dimensional porous electrode according to claim 1, characterized in that: In step (2), the weight ratio of the iron sulfate powder, nickel sulfate powder, melamine powder and chitosan powder is (12-18): (0.5-2.5): (2.5-6.5): (1-3).

4. The method for preparing the iron-nickel composite three-dimensional porous electrode according to claim 1, characterized in that: In step (3), the printing substrate needs to be preheated before printing. The printing substrate is a glass plate with transparent tape attached, and the preheating temperature is 40~50℃.

5. The method for preparing the iron-nickel composite three-dimensional porous electrode according to claim 1, wherein: In step (3), during printing, air pressure is applied to the barrel to allow the slurry to enter the screw extruder. As the screw rotates, the slurry is extruded from the nozzle at a constant speed, and the printer needle moves at a constant speed to print the three-dimensional wood pile structure blank; wherein: the applied air pressure is 0.2-0.4MPa, the screw extruder rotation extrusion ratio is 50-60%, and the printer needle movement speed is 800-1500 mm / min.

6. The method for preparing the iron-nickel composite three-dimensional porous electrode according to claim 1, characterized in that: In step (4), the high temperature heat treatment process is as follows: first, ammonia gas is exhausted for 0.5-1 h, then the temperature is raised from room temperature to 750-850°C at a heating rate of 3-8°C / min and kept at this temperature for 2-5 hours; After the insulation is completed, the electrode is naturally cooled to 150-250°C and then the introduction of ammonia is stopped. The electrode is then naturally cooled to room temperature and the electrode is taken out for cleaning and drying.

7. An iron-nickel composite three-dimensional porous electrode prepared by the method according to any one of claims 1 to 6.

8. The iron-nickel composite three-dimensional porous electrode according to claim 7, characterized in that: The iron-nickel composite three-dimensional porous electrode is a three-dimensional porous structure composed of FeS and Fe3NiN. Carbon material is evenly distributed inside and on the surface of the three-dimensional porous structure skeleton. The carbon material is elemental carbon and / or carbon compound. FeS is used as the main material of the electrode to maintain the stability of the three-dimensional structure and provide Fe 2+ The ions undergo electro-Fenton reaction; the uniform distribution of carbon materials improves the electrode conductivity and enhances the mechanical properties of the three-dimensional structure; Fe3NiN acts as an ion conductor to accelerate electron transfer and provide Ni 0 Participate in the electro-Fenton reaction.

9. Application of the iron-nickel composite three-dimensional porous electrode in electro-Fenton technology according to claim 7, characterized in that: The iron-nickel composite three-dimensional porous electrode is used as a cathode in the electro-Fenton technology.

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