Metal-doped modified foam carbon material as well as preparation method and application thereof

Abstract

The invention discloses a metal-doped modified foam carbon material, and a preparation method and application thereof, and belongs to the field of electrochemistry, during preparation, firstly, a fusible biomass material, a Fenton metal oxide and a foaming material are uniformly mixed in a molten state of the fusible biomass material to obtain a uniform melt; the uniform melt is placed in a drying oven to be dried for a period of time, foaming and solidification are carried out, organic foam is obtained, and the drying temperature is lower than the melting point temperature of the fusible biomass material; carrying out high-temperature dehydration treatment on the organic foam; the metal-doped modified foam carbon material is obtained by carbonizing organic foam subjected to high-temperature dehydration, when the metal-doped modified foam carbon material is used as a heterogeneous E-Fenton cathode, the limitation of traditional E-Fenton can be broken through, the 30-min removal rate of organic dye (RhB) under the neutral condition reaches 100%, the metal-doped modified foam carbon material has the advantages of high reaction activity, good treatment effect and the like, addition of Fe ions and hydrogen peroxide is not needed, and the metal-doped modified foam carbon material is suitable for industrial production. No iron mud is generated in the reaction, and no foam carbon falls off.

Description

Technical Field

[0001] The invention belongs to the field of electrochemistry and relates to a technology for preparing an electrochemical electrode material, and specifically relates to a metal-doped modified carbon foam material, a preparation method and an application thereof; the metal-doped modified carbon foam material can be used to prepare a heterogeneous E-Fenton cathode. Background Art

[0002] Carbon foam is a new type of three-dimensional porous carbon material composed of pores and interconnected pore walls. It is a typical material with low density, high electrical conductivity, high thermal conductivity, easy processing, high mechanical strength, etc. It has good application prospects in the fields of electrocatalysis and so on.

[0003] The modification preparation method of the existing foam carbon is to achieve the modification by coating the surface of the existing foam carbon. Patent CN117479519A applies silver nanoparticles to the surface of the foam carbon material prepared with melamine as the substrate by impregnation, and prepares the silver nanoparticle modified foam carbon material. Patent CN118345414A cuts, washes and dries the polyurethane foam to obtain the polyurethane foam; adds coal liquefaction asphalt and graphene to the tetrahydrofuran solution and stirs; immerses the polyurethane foam into the tetrahydrofuran mixed solution and dries after immersion; oxidizes and solidifies the polyurethane foam loaded with asphalt and graphene to obtain a composite foam; carbonizes the composite foam under an inert gas atmosphere to obtain foam carbon; immerses the foam carbon in a DMF solution of nickel acetylacetonate to obtain a foam carbon intermediate loaded with a nickel source; places the foam carbon intermediate loaded with a nickel source and melamine together in a corundum boat, and co-pyrolyzes them under an inert atmosphere to obtain the target material. Ridha Djellabi prepared aerogels using polyvinyl alcohol, polyvinylidene fluoride and polyvinyl acetate as raw materials, and then used the impregnation method to 2 Self-floating biomass carbon / TiO was prepared by loading on aerogel 2 Aerogel composite foam carbon material. Huang Baoxuan et al. used polyurethane foam carbon as a carrier and prepared polyurethane foam carbon loaded with TiO by impregnation method. 2 Modified foam carbon materials [Huang Baoxuan, Zhang Hongqing, Meng Zhendong, et al. Preparation and characterization of functional foam carbon for photocatalytic degradation of formaldehyde. Functional Materials, 2016, 47(1): 1213-1217]. Qian et al. used phenolic resin foam carbon as a carrier to transform mesoporous TiO 2 TiO was prepared by thin film deposition on carbon foam 2 / Foam carbon material.

[0004] However, it is not difficult to find from the above research that in previous cases, the synthetic modified carbon foam materials were mostly fixed on large-sized porous carriers by impregnation. However, this type of loading method usually relies on simple physical action, and there are problems such as powder materials easily falling off, weak adsorption, and easy leaching. In addition, when the existing modified carbon foam materials are used as the cathode of the electro-Fenton (E-Fenton), the reaction process requires the addition of homogeneous Fe 2+ If under neutral or alkaline conditions, the Fe 3+ Iron sludge precipitation is inevitable, which makes the H generated on the surface of the cathode material 2 O 2 It is difficult to react with Fe in solution 2+ The catalytic reaction occurs to form •OH, resulting in a narrow pH range for this process (usually the most suitable pH ≈ 3).

[0005] Based on the above problems, it is necessary to further study the foam carbon modification process to solve the problem that the modified foam carbon material in the prior art is not effective when used as an electro-Fenton cathode. Summary of the invention

[0006] In response to the above problems, one of the objects of the present invention is to provide a method for preparing a metal-doped modified carbon foam material, which utilizes a new process path to modify the carbon foam by doping it with metal. No water solvent is required during the modification process, thereby making the metal-doped modified carbon foam material low-cost and the metal doping more uniform.

[0007] Another object of the present invention is to use the metal-doped modified carbon foam material prepared by the above preparation method as an electro-Fenton cathode. When used as an electro-Fenton cathode, the material has stable performance and a wide pH range. During the electro-Fenton reaction, no H is required to be added. 2 O 2 , Fe ions, only a certain concentration of electrolyte needs to be added. No iron sludge is produced and foam carbon falls off during the reaction, and the solution is very clear and transparent after the reaction.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: In one aspect, the present invention provides a method for preparing a metal-doped modified carbon foam material, comprising the following steps: S1, mixing the fusible biomass material, the Fenton-type metal oxide and the foaming material in a molten state of the fusible biomass material to obtain a uniform melt; S2, placing the uniform melt into an oven for drying for a period of time to foam and solidify to obtain an organic foam, wherein the drying temperature is lower than the melting point of the fusible biomass material; S3, subjecting the organic foam to high temperature dehydration treatment; S4, carbonizing the organic foam after high-temperature dehydration to obtain a metal-doped modified foam carbon material.

[0009] The present invention uniformly mixes a fusible biomass material, a Fenton-type metal oxide and a foaming material in a molten state of the fusible biomass material to obtain a uniform melt, and then dries the uniform melt at a temperature slightly below the melting point, so that foaming and solidification are performed simultaneously to obtain an organic foam. The present invention selects to perform foaming and solidification by drying at a temperature slightly below the melting point, because when the temperature is slightly below the melting point, the uniform melt is in a semi-solid state, and can be shaped and foamed with a foaming agent to form a porous material; if the temperature is too low, not only the dehydration speed is slow, but also the foaming is difficult, and the porous material cannot be formed, and even the crystalline water cannot be removed. The slow dehydration speed will result in a long dehydration time or incomplete solidification, and the foam form of the product cannot be maintained during subsequent high-temperature dehydration; after sufficient drying and dehydration, the organic foam can withstand subsequent high-temperature deep dehydration. After drying, it can be decided whether to cut the organic foam into pieces according to needs to adapt to the final product form. Then, the organic foam or the cut organic foam is subjected to high-temperature deep dehydration to further reduce the water content (mainly bound water, such as crystal water) in the fusible biomass material to prepare for high-temperature carbonization. Then, the organic foam after high-temperature dehydration is carbonized to obtain a metal-doped modified foam carbon material; the doped metal is evenly loaded and has good load firmness.

[0010] Furthermore, in step S1, there are two methods for uniformly mixing the fusible biomass material, the Fenton-type metal oxide and the foaming material in the molten state of the fusible biomass material, respectively: The first method comprises mixing the fusible biomass material, the Fenton-type metal oxide and the foaming material, grinding the mixture into a uniform mixed powder, and heating the mixed powder until it is melted to obtain a uniform melt; The second method is to mix the fusible biomass material and the Fenton-type metal oxide, grind them into a uniform mixed powder, heat the mixed powder until it is melted, and add the foaming material to stir and mix them evenly to obtain a uniform melt.

[0011] Since the foaming temperature of the foaming agent is mostly similar to that of the fusible biomass material, the first mixing method has the best uniformity effect, but the foaming agent is lost prematurely during melting, and the bubbles generated in the melting stage are harmful to the subsequent micropore formation of the foamed carbon. Therefore, the heating rate during melting should be controlled to avoid excessive and rapid decomposition and foaming of the foaming agent; the second mixing method has slightly insufficient uniformity, but fewer bubbles are generated when a melt is formed, which can avoid premature loss of the foaming agent.

[0012] Furthermore, in step S1, the grinding method is ball milling, the ball milling speed is 50-400 rpm, and the ball milling time is 5-30 min; ball milling can better improve the grinding fineness and uniformity, and reduce the difficulty of later melting.

[0013] Furthermore, in step S1, when heating and melting, the heating temperature does not exceed 2°C of the melting point of the fusible biomass material; and during the heating process, the melt needs to be observed. When there are many bubbles, the heating temperature needs to be lowered to reduce the heating rate and avoid premature foaming of the foaming agent, which affects the subsequent foaming effect.

[0014] Furthermore, in step S1, constant temperature heating is adopted during heating and melting, and the temperature of the constant temperature heating is 150-190°C.

[0015] Furthermore, the fusible biomass material is any one of sucrose, glucose and lignin, or a mixture of several of them.

[0016] Furthermore, the Fenton-type metal oxide is at least one of iron oxide, nickel oxide, aluminum oxide, copper oxide, and cobalt oxide.

[0017] Furthermore, the foaming material is boric acid or nitrate of Fenton metals.

[0018] The nitrates of the Fenton metals include aluminum nitrate, cobalt nitrate, nickel nitrate, copper nitrate, manganese nitrate and iron nitrate.

[0019] Further, the foaming material is 1%-10% of the total mass of the fusible biomass material and the Fenton-type metal oxide; The mass ratio of the fusible biomass material to the Fenton-type metal oxide is 120:1~20:1.

[0020] Furthermore, in step S2, the drying temperature of the uniform melt is 5-30°C lower than the melting point of the fusible biomass material, and the drying time is 36-54h.

[0021] Furthermore, in step S2, the drying temperature is 115-145°C, and the drying time is 36-54h.

[0022] Furthermore, in step S2, for different Fenton-type metal oxides, the drying and foaming temperature is different. For iron oxide, the drying and foaming temperature is 120-140°C; for titanium oxide, the drying and foaming temperature is 120-145°C; for cobalt oxide, the drying and foaming temperature is 115-130°C; for nickel oxide, the drying and foaming temperature is 115-130°C.

[0023] Furthermore, in step S3, the high temperature dehydration temperature is 250-300°C, and the dehydration time is 12-24h; a porous organic foam is formed by sufficient high temperature dehydration, which provides a basis for the subsequent carbonization to form foamed carbon.

[0024] Furthermore, in step S3, high temperature dehydration is performed in a muffle furnace, which is an aerobic environment.

[0025] Furthermore, in step S3, the temperature rise gradient of high temperature dehydration is set to: 2-5°C / min from room temperature to 150°C, and 1-2°C / min from 150°C to 250°C.

[0026] Furthermore, in step S4, the carbonization temperature is 700-900° C., and the carbonization time is 1-3 h.

[0027] Furthermore, in step S4, the temperature rise gradient of the carbonization temperature is: the temperature rise gradient from room temperature to carbonization temperature is 2-5°C / min.

[0028] On the other hand, the present invention provides a metal-doped modified carbon foam material prepared by the above-mentioned preparation method.

[0029] On the other hand, a metal-doped modified carbon foam material is used to prepare an electro-Fenton cathode, which has stable performance, a wide pH range, and can efficiently produce •OH in situ without adding H 2 O 2 , Fe 2+ ions, no iron sludge is produced and foam carbon falls off during the reaction.

[0030] The applicant found during the experiment that although the melting points of different types of fusible biomass materials are different, such as sucrose at about 186°C and glucose at about 146°C; however, after adding a foaming agent such as boric acid or a salt, the material can be maintained in a viscous state at a temperature far below the melting point of the fusible biomass material, such as in the range of 110-155°C, indicating that the addition of the foaming agent changes the melting point, and the change to a viscous state is also an ideal state for foaming; and according to the comparison of experimental results, when boric acid is used as a foaming agent, when it is close to the melting point, the organic foam expands excessively because the foaming speed of the foaming agent is too fast, and ultimately the foaming fails; at about 120-130°C, the foaming speed of the foaming agent decreases, and a relatively long time is required, but the foaming effect is better, the foaming is dense and uniform, and the Fenton reaction effect of the obtained metal-doped modified foam carbon material is good.

[0031] Compared with the prior art in which the modified carbon foam material is fixed on a large-sized porous carrier by an impregnation method, the present invention has the following beneficial effects: The present invention adopts a brand-new process path. Instead of using an impregnation method, the Fenton-type metal oxide, a foaming agent and a fusible biomass material in a molten state are directly mixed evenly, and then dried at a temperature slightly below the melting point to remove the crystal water in the fusible biomass material while foaming and solidifying. After further high-temperature dehydration, a foamed carbon precursor is obtained. The foamed carbon precursor is subjected to high-temperature carbonization to obtain a metal-doped modified foamed carbon material. The metal material in the present invention is wrapped inside the foamed carbon, rather than on the surface of a porous structure, and has technical advantages such as firm loading and not easy to leaching. When the metal-doped modified foamed carbon material is used as an electro-Fenton cathode, its performance temperature and pH application range are wide (the E-Fenton reaction can be carried out efficiently and stably under neutral conditions), and OH can be produced in situ efficiently, and the reaction does not require the addition of H 2 O 2 , Fe 2+ ions, no iron sludge is produced and foam carbon falls off during the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a flow chart for preparing the metal-doped modified carbon foam material.

[0033] Figure 2 Characterization of the Fe-doped modified carbon foam material prepared in Example 3 of the present invention, wherein: Figure 1 (a) is a SEM (scanning electron microscope) image. Figure 1 (b) is the element distribution diagram. Figure 1 (c) is the C element distribution diagram in the element distribution diagram. Figure 1 (d) is the Fe element distribution diagram.

[0034] Figure 3 The Fe-doped modified carbon foam material was used as the electro-Fenton cathode for RhB degradation process.

[0035] Figure 4 The Fe-doped modified carbon foam material was used as an electro-Fenton cathode to degrade RhB. Figure 4 (a) is a SEM (scanning electron microscope) image. Figure 1 (b) is the element distribution diagram. Figure 1 (c) is the C element distribution diagram in the element distribution diagram. Figure 1 (d) is the Na element distribution diagram in the element distribution diagram. Figure 1 (e) is the Fe element distribution diagram in the element distribution diagram. DETAILED DESCRIPTION

[0036] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0037] like Figure 1 As shown, the present invention provides a method for preparing a metal-doped modified carbon foam material, comprising the following steps: S1, mixing the fusible biomass material, the Fenton-type metal oxide and the foaming material in a molten state of the fusible biomass material to obtain a uniform melt; S2, placing the uniform melt into an oven for drying for a period of time to foam and solidify to obtain an organic foam, wherein the drying temperature is lower than the melting point of the fusible biomass material; S3, subjecting the organic foam to high temperature dehydration treatment; S4, carbonizing the organic foam after high temperature dehydration to obtain Fe-doped modified foam carbon.

[0038] Example 1 1) Mix 30 g sucrose, 0.25 g iron oxide, and 2% boric acid, and ball-mill them on a ball mill at 400 rpm for 30 min to obtain a ball-milled mixture; put the ball-milled mixture into a borosilicate glass tray, put a digital temperature-controlled electric heating jacket into the glass tray, and heat at 155 °C until a uniform melt is formed, and control the heating temperature to avoid generating a large number of bubbles.

[0039] 2) After cooling the uniform melt, place it in an oven at 145°C for 48 hours for foaming and solidification to obtain an organic foam.

[0040] 3) The organic foam was cut into rectangular blocks and dehydrated in a muffle furnace at 250 °C for 20 h. The dehydration rate was 5 °C / min from room temperature to 150 °C and 1 °C / min from 150 °C to 250 °C.

[0041] 4) The dehydrated organic foam was carbonized in a tubular furnace at 900 °C for 2 h. The temperature gradient from room temperature to 900 °C was 5 °C / min. The entire process of carbonization from heating to cooling was completed in a high-purity N2 atmosphere with a N2 flow rate of 180 ml / min. -1 After cooling, a metal-doped modified carbon foam material is obtained.

[0042] A series of examples were obtained by replacing iron oxide with cobalt oxide, nickel oxide, and titanium oxide, changing the foaming temperature in the oven, and keeping other conditions and parameters unchanged. The foaming effects of the organic foams were observed as shown in Tables 1 and 2.

[0043] Table 1 Foaming effect of organic foams in Examples 1-16

[0044] Table 2 Foaming effect of organic foams in Examples 17-32

[0045] High-quality foaming of organic foam is the basis for carbonization preparation of electro-Fenton cathode. According to experimental observations, the final expansion multiple during the foaming process of organic foam has a great influence on the electro-Fenton reaction effect of foam carbon. Generally speaking, the final expansion multiple of organic foam is less than 2, which means insufficient foaming, small micropores, and low electro-Fenton reaction efficiency; the expansion multiple is about 2-5 times, which is a suitable multiple, and it is excessive foaming when it exceeds 5 times, resulting in insufficient strength of organic foam, and easy to produce large local bubbles inside, easy to collapse in the subsequent carbonization process, easy to peel off during the use of electro-Fenton, and poor conductivity, and poor use effect; It can be seen from Table 1 that iron oxide and titanium oxide have the best foaming effect under the condition of 130°. It can be seen from Table 2 that nickel oxide and cobalt oxide have the best foaming effect at a temperature of 120°.

[0046] Material Characterization: The surface morphology of the iron-doped modified carbon foam material sample prepared in Example 3 was imaged using a SEM5000 scanning electron microscope (Guoyi Quantum Technology Co., Ltd.). Figure 2 .

[0047] from Figure 2 (a) It can be seen that the prepared Fe-doped modified foam carbon has good porosity and uniform distribution. Figure 2 (bd) It can be seen that the iron element is evenly distributed on the foam carbon material, and the iron and carbon materials are evenly mixed, rather than the iron being loaded on the surface of the foam carbon material.

[0048] Embodiment 31: The Fe-doped modified foam carbon prepared in Example 3 was used for electro-Fenton cathode degradation of rhodamine (RhB) The DC voltage was 8 V, the anode was a platinum sheet (1 cm × 2 cm), the cathode was Fe-doped modified carbon foam material (1 cm × 2 cm), the cathode and anode were placed in parallel, the electrode spacing was 2 cm, and the initial RhB concentration was c 0 The oxygen filling rate of the reactor was 0.1 L / min, and the electrolyte Na 2 SO 4 The concentration was 0.35 mol / L, the pH of the reaction solution was neutral, and the reaction time was 30 min. The experimental results are shown in Table 3. Figure 2 .

[0049] Table 3 and Figure 3It can be seen that Fe-doped modified foam carbon has a good effect on degrading RhB as an electro-Fenton cathode, and the RhB removal rate reaches 100% in 30 minutes. In addition, it was observed that there was no slag falling off the surface of the cathode material during the entire reaction process, and the solution was almost colorless and transparent after the degradation was completed, indicating that Fe-doped modified foam carbon material has excellent performance in degrading RhB as an electro-Fenton cathode, and the removal rate did not change significantly during the two reaction processes. There was no iron ion leaching during the reaction, and no foam carbon material fell off.

[0050] Table 3 Fe-doped modified carbon foam used as electro-Fenton cathode for degradation of RhB

[0051] In the table, c t Test concentration for RhB.

[0052] Post-reaction material characterization Because the electrolyte used is Na 2 SO 4 After the reaction, no cleaning was performed, so Na ions were attached to the Fe-doped modified carbon foam after it was used as an electro-Fenton cathode to degrade RhB. The Fe-doped modified carbon foam was characterized after it was used as an electro-Fenton cathode to degrade RhB, such as Figure 4 As shown; Figure 2 , 4 Comparative observations show that before and after the Fe-doped modified carbon foam material was used as the electro-Fenton cathode to degrade RhB, the structure of the modified carbon foam material was intact and there was no pore collapse; there was no obvious change in the iron ions in the modified carbon foam, which further confirmed the reaction stability of the Fe-doped modified carbon foam material.

[0053] The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a metal-doped modified carbon foam material, characterized in that: The following steps are involved: The fusible biomass material, the Fenton-type metal oxide and the foaming material are uniformly mixed in a molten state of the fusible biomass material to obtain a uniform melt; After cooling the uniform melt, place it in an oven for drying for a period of time to foam and solidify it to obtain an organic foam, and the drying temperature is lower than the melting point of the fusible biomass material; subjecting the organic foam to high temperature dehydration treatment; The organic foam after high-temperature dehydration is carbonized to obtain a metal-doped modified foam carbon material.

2. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The method for uniformly mixing the fusible biomass material, the Fenton-type metal oxide and the foaming material in the molten state of the fusible biomass material is as follows: The fusible biomass material, the Fenton-type metal oxide and the foaming material are mixed, ground into a uniform mixed powder, and the mixed powder is heated to melt to obtain a uniform melt; or The fusible biomass material and the Fenton-type metal oxide are mixed and ground into a uniform mixed powder, the mixed powder is heated to melt, and the foaming material is added and stirred to obtain a uniform melt.

3. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The fusible biomass material includes sucrose, glucose and lignin.

4. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The Fenton-type metal oxide is at least one of iron oxide, nickel oxide, aluminum oxide, copper oxide and cobalt oxide.

5. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The foaming material is boric acid or nitrate of Fenton metals.

6. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The foaming material is 1%-10% of the total mass of fusible biomass material and Fenton-type metal oxide; The mass ratio of the fusible biomass material to the Fenton-type metal oxide is 120:1~20:

1.

7. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The drying temperature of the uniform melt is 10-70° C. lower than the melting point of the fusible biomass material, and the drying time is 36-54 hours.

8. The method for preparing the metal-doped modified carbon foam material according to claim 1, characterized in that: The high temperature dehydration temperature is 250-300℃ and the dehydration time is 12-24h.

9. A metal-doped modified carbon foam material, characterized in that: The product is prepared by the preparation method according to any one of claims 1 to 8.

10. A use of the metal-doped modified carbon foam material according to claim 9, characterized in that: Used to prepare electro-Fenton cathode.

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