A porous hydrotalcite and its preparation method

Abstract

The present invention relates to a preparation method of porous hydrotalcite, which is carried out according to the following steps: (1) An electro-etching system is constructed with a carbon fiber membrane in-situ loaded with hydrotalcite as the anode, an inert electrode as the cathode, and a sodium chloride solution as the electrolyte solution; (2) The electro-etching system is externally connected to a direct current electric field for electro-etching; (3) After the electro-etching is completed, the anode is taken out, rinsed with deionized water, and dried to obtain the product. The present invention also provides a porous hydrotalcite prepared by the above method. The present invention uses carbon fiber as the carrier of hydrotalcite, ensuring chemical stability and conductivity during the electro-etching process, being easy to recycle, having low cost, and being simple to prepare; at the same time, the prepared porous hydrotalcite has dense and uniform vacancy defects, many exposed active sites, and high intrinsic activity.

Description

Technical Field

[0001] The present invention relates to the field of functional materials, and particularly to a porous hydrotalcite and a preparation method thereof. Background Art

[0002] Layered double hydroxides (LDHs), also known as hydrotalcite, are materials with low cost, high redox activity, and environmental friendliness. Its molecular formula can be expressed as [M 2+ 1-x M 3+ x (OH) 2 x+ (A n- ) x / n ·mH 2 O, which is a kind of unique layered structure material composed of positively charged lamellar and interlayer anions. Due to the layered structure of hydrotalcite and the tunability of the number and type of interlayer anions, it has great application prospects and has good applications in the fields of catalysis, adsorption, biology, energy storage and conversion, etc.

[0003] However, the hydrotalcite powder catalyst has the disadvantages of low catalytic activity, easy agglomeration and difficult recovery, which to a certain extent limits its application. At present, introducing transition metals into the LDH lamellar, optimizing the electronic structure of LDH, or introducing dangling bonds, preparing different types of vacancies to modify the surface of the catalyst, or preparing a catalyst supported on a suitable carrier are all effective ways to improve catalytic activity and selectivity. Among them, modifying the surface of the catalyst by creating different types of vacancy defects has attracted extensive attention. Because the defect sites can serve as active centers to enhance catalytic activity. It can not only regulate the interaction between the catalyst and the reaction molecules, thereby reducing the reaction activation energy, but even change the reaction pathway, thereby regulating the reaction selectivity. The currently common defect types mainly include: oxygen vacancies, metal vacancies, lattice distortion and other types. Designing and regulating the defect type and defect density on the catalyst surface is an important means to adjust its activity.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] In order to solve the existing technical problems, the present invention provides a method for preparing porous hydrotalcite by an electroetching method. The porous hydrotalcite material prepared by this method has good mechanical stability and catalytic activity, and has a large specific surface area and is not easy to agglomerate.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] ​First, the present invention provides a method for preparing porous hydrotalcite, which is carried out according to the following steps:

[0008] (1) Construct an electro-etching system with a carbon fiber membrane in-situ loaded with hydrotalcite as the anode, an inert electrode as the cathode, and a sodium chloride solution as the electrolyte solution;

[0009] (2) Connect the electro-etching system to an external DC electric field for electro-etching;

[0010] (3) After the electro-etching is completed, take out the anode, rinse it with deionized water, and dry it to obtain the product.

[0011] The inert electrode can be any one of graphite, carbon cloth or titanium mesh.

[0012] Preferably or optionally, the hydrotalcite loaded on the carbon fiber membrane in-situ is a layered hydrotalcite material of transition metal elements.

[0013] Preferably or optionally, the layered hydrotalcite material of transition metal elements is any one of nickel-aluminum hydrotalcite, nickel-cobalt hydrotalcite, nickel-manganese hydrotalcite, cobalt-aluminum hydrotalcite.

[0014] Preferably or optionally, the concentration of the sodium chloride solution in step (1) is 0.1 - 5 mol·L -1 .

[0015] Preferably or optionally, the voltage of the external DC electric field in step (2) is 0.1 - 9 V.

[0016] Preferably or optionally, the electro-etching time in step (2) is 0.5 - 5 h.

[0017] Preferably or optionally, the drying process in step (3) is hot air drying.

[0018] Preferably or optionally, the temperature of the hot air drying is 60 - 150 °C, and the drying time is 2 - 12 h.

[0019] On the other hand, the present invention also provides a porous hydrotalcite prepared by the above method for preparing porous hydrotalcite.

[0020] Beneficial effects

[0021] The present invention uses carbon fiber as the carrier of hydrotalcite, which ensures the chemical stability and conductivity during the electro-etching process, is easy to recycle, has low cost and simple preparation; at the same time, the prepared porous hydrotalcite has dense and uniform vacancy defects, many exposed active sites and high intrinsic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is the electron microscope image of nickel-aluminum hydrotalcite in-situ loaded on the carbon fiber membrane as the raw material of Example 5;

[0023] Figure 2 It is the electron microscope image of the porous hydrotalcite product prepared in Example 5;

[0024] Figure 3 It is the result graph of room temperature electron paramagnetic resonance in Effect Example 2;

[0025] Figure 4 It is the scanning electron microscope image of the nickel-aluminum hydrotalcite in-situ loaded on the carbon fiber membrane as the raw material of Example 5;

[0026] Figure 5 It is the scanning electron microscope image of the anodic material after electro-etching during the preparation process of Example 5;

[0027] Figure 6 It is the scanning electron microscope image of the porous hydrotalcite product prepared in Comparative Example 1;

[0028] Figure 7 It is the scanning electron microscope image of the porous hydrotalcite product prepared in Comparative Example 2;

[0029] Figure 8 It is the scanning electron microscope image of the anodic material after electro-etching during the preparation process of Example 12;

[0030] Figure 9 It is the electron microscope image of the porous hydrotalcite product prepared in Comparative Example 3;

[0031] Figure 10 It is the scanning electron microscope image of the porous hydrotalcite product prepared in Comparative Example 4. Detailed implementation manners

[0032] For the convenience of understanding the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the specification drawings and preferred experimental examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all the technical terms used hereinafter have the same meanings as those commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0034] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0035] Among them, the hydrotalcite in-situ loaded carbon fiber membranes used in each embodiment of the present invention are all prepared by the method in Patent CN112316903A.

[0036] Example 1

[0037] This example provides a porous hydrotalcite material.

[0038] The porous hydrotalcite material is prepared by the following method:

[0039] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0040] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 0.5 V, and the electro-etching time is 5 h.

[0041] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 60 °C for 10 h. After drying, a porous hydrotalcite product is obtained.

[0042] Example 2

[0043] This example provides a porous hydrotalcite material.

[0044] The porous hydrotalcite material is prepared by the following method:

[0045] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1.5 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0046] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 1.0 V, and the electro-etching time is 1.5 h.

[0047] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 80 °C for 8 h. After drying, a porous hydrotalcite product is obtained.

[0048] Example 3

[0049] This example provides a porous hydrotalcite material.

[0050] The porous hydrotalcite material is prepared by the following method:

[0051] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 2 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0052] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 1.5 V, and the electro-etching time is 2 h.

[0053] After the electro-etching is completed, take out the anode, wash it several times with deionized water, and dry it in hot air at 80 °C for 10 h. After drying, a porous hydrotalcite product is obtained.

[0054] Example 4

[0055] This example provides a porous hydrotalcite material.

[0056] The porous hydrotalcite material is prepared by the following method:

[0057] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0058] Connect the electro-etching system to an external DC electric field for electro-etching. The DC electric field voltage is 2.0 V, and the electro-etching time is 1 h.

[0059] After the electro-etching is completed, take out the anode, wash it several times with deionized water, and dry it in hot air at 80 °C for 6 h. After drying, a porous hydrotalcite product is obtained.

[0060] Example 5

[0061] This example provides a porous hydrotalcite material.

[0062] The porous hydrotalcite material is prepared by the following method:

[0063] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0064] Connect the electro-etching system to an external DC electric field for electro-etching. The DC electric field voltage is 2.5 V, and the electro-etching time is 1 h.

[0065] After the electro-etching is completed, take out the anode, wash it several times with deionized water, and dry it in hot air at 80 °C for 6 h. After drying, a porous hydrotalcite product is obtained.

[0066] Effect Example 1

[0067] Take the nickel-aluminum hydrotalcite on the nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane used as the raw material in Example 5 and the porous hydrotalcite product prepared in Example 5 and observe them under an electron microscope respectively. The results are as Figure 1 and Figure 2 shown.

[0068] From Figure 1 and Figure 2It can be seen by comparison that after electroetching using the method of the present invention, pore-like structures with a diameter of about 2-4 nm are uniformly distributed on the hydrotalcite nanosheets. The above results indicate that the method provided by the present invention can prepare porous hydrotalcite materials.

[0069] Effect Example 2

[0070] Room temperature electron paramagnetic resonance (EPR) was used to study the paramagnetic defects of nickel-aluminum hydrotalcite in situ loaded on carbon fiber membranes as raw materials for Examples 4 and 5 and the porous hydrotalcite products prepared in Examples 4 and 5. The results are as Figure 3 shown.

[0071] It can be Figure 3 seen that although the g-factor values of the three materials are all 2.003, the signal intensities from high to low are Example 5, Example 4, and the hydrotalcite as the raw material. The above results indicate that on the premise that other factors are the same, the concentration of paramagnetic defects in the product increases with the increase of the electroetching voltage.

[0072] Effect Example 3

[0073] The nickel-aluminum hydrotalcite in situ loaded on the carbon fiber membrane as the raw material for Example 5 and the anodic material after electroetching in the preparation process of Example 5 were respectively placed under a scanning electron microscope (SEM) for observation. The results are as Figure 4 and Figure 5 shown.

[0074] It can be Figure 4 and Figure 5 seen that through the method provided by the present invention, after electroetching, the nickel-aluminum hydrotalcite nanosheets are still densely distributed on the surface of the carbon fiber and no peeling phenomenon occurs.

[0075] Example 6

[0076] This example provides a porous hydrotalcite material.

[0077] The porous hydrotalcite material is prepared by the following method:

[0078] Using a nickel-manganese hydrotalcite in situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 2.5 mol / L sodium chloride solution as the electrolyte solution, an electroetching system is constructed.

[0079] The electroetching system is externally connected to a direct current electric field for electroetching. The direct current electric field voltage is 2.5 V, and the electroetching time is 0.5 h.

[0080] After electroetching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 100 °C for 4 h. After drying is completed, a porous hydrotalcite product is obtained.

[0081] Example 7

[0082] This example provides a porous hydrotalcite material.

[0083] The porous hydrotalcite material is prepared by the following method:

[0084] Using a nickel-cobalt hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 0.5 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0085] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 2.5 V, and the electro-etching time is 1.5 h.

[0086] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 80 °C for 12 h. After drying, a porous hydrotalcite product is obtained.

[0087] Example 8

[0088] This example provides a porous hydrotalcite material.

[0089] The porous hydrotalcite material is prepared by the following method:

[0090] Using a cobalt-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 2.5 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0091] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 3.0 V, and the electro-etching time is 1 h.

[0092] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 130 °C for 2 h. After drying, a porous hydrotalcite product is obtained.

[0093] Example 9

[0094] This example provides a porous hydrotalcite material.

[0095] The porous hydrotalcite material is prepared by the following method:

[0096] Using a nickel hydroxide hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 3 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0097] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 2.5 V, and the electro-etching time is 3 h.

[0098] After the electro-etching is completed, take out the anode, wash it several times with deionized water, and dry it in hot air at 70 °C for 12 h. After drying, a porous hydrotalcite product is obtained.

[0099] Example 10

[0100] This example provides a porous hydrotalcite material.

[0101] The porous hydrotalcite material is prepared by the following method:

[0102] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 0.1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0103] Connect the electro-etching system to an external DC electric field for electro-etching. The DC electric field voltage is 4 V, and the electro-etching time is 0.5 h.

[0104] After the electro-etching is completed, take out the anode, wash it several times with deionized water, and dry it in hot air at 80 °C for 12 h. After drying, a porous hydrotalcite product is obtained.

[0105] Example 11

[0106] This example provides a porous hydrotalcite material.

[0107] The porous hydrotalcite material is prepared by the following method:

[0108] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 0.5 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0109] Connect the electro-etching system to an external DC electric field for electro-etching. The DC electric field voltage is 8 V, and the electro-etching time is 0.5 h.

[0110] After the electro-etching is completed, take out the anode, wash it several times with deionized water, and dry it in hot air at 140 °C for 2 h. After drying, a porous hydrotalcite product is obtained.

[0111] Example 12

[0112] This example provides a porous hydrotalcite material.

[0113] The porous hydrotalcite material is prepared by the following method:

[0114] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 5 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0115] The electro-etching system is externally connected to a DC electric field for electro-etching. The voltage of the DC electric field is 2.5 V, and the electro-etching time is 1 h.

[0116] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 80 °C for 5 h. After drying is completed, a porous hydrotalcite product is obtained.

[0117] Example 13

[0118] This example provides a porous hydrotalcite material.

[0119] The porous hydrotalcite material is prepared by the following method:

[0120] An electro-etching system is constructed with a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a carbon cloth electrode as the cathode, and a 5 mol / L sodium chloride solution as the electrolyte solution.

[0121] The electro-etching system is externally connected to a DC electric field for electro-etching. The voltage of the DC electric field is 9 V, and the electro-etching time is 0.5 h.

[0122] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 60 °C for 12 h. After drying is completed, a porous hydrotalcite product is obtained.

[0123] Example 14

[0124] This example provides a porous hydrotalcite material.

[0125] The porous hydrotalcite material is prepared by the following method:

[0126] An electro-etching system is constructed with a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 2 mol / L sodium chloride solution as the electrolyte solution.

[0127] The electro-etching system is externally connected to a DC electric field for electro-etching. The voltage of the DC electric field is 4 V, and the electro-etching time is 0.5 h.

[0128] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 120 °C for 4 h. After drying is completed, a porous hydrotalcite product is obtained.

[0129] Example 15

[0130] This example provides a porous hydrotalcite material.

[0131] The porous hydrotalcite material is prepared by the following method:

[0132] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system was constructed.

[0133] The electro-etching system was externally connected to a DC electric field for electro-etching. The DC electric field voltage was 2.5 V, and the electro-etching time was 2.5 h.

[0134] After the electro-etching was completed, the anode was taken out, washed several times with deionized water, and dried in hot air at 150 °C for 2 h. After drying, a porous hydrotalcite product was obtained.

[0135] Effect Example 4

[0136] The anodic material after electro-etching in the preparation process of Example 12 was taken and observed under a scanning electron microscope (SEM). The results are as Figure 8 shown.

[0137] From Figure 8 it can be seen that by the method provided by the present invention, after electro-etching, the nickel-aluminum hydrotalcite nanosheets are still densely distributed on the surface of the carbon fiber without falling off. The sodium chloride solution serves as the starting supporting electrolyte, and the ions therein play a role in maintaining the charge balance of each part and maintaining the electrical neutrality of the solution through directional movement. Its concentration fluctuates within a certain range and has no influence on the etching effect.

[0138] Comparative Example 1

[0139] This comparative example provides a porous hydrotalcite material.

[0140] The porous hydrotalcite material was prepared by the following method:

[0141] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system was constructed.

[0142] The electro-etching system was externally connected to a DC electric field for electro-etching. The DC electric field voltage was 2.5 V, and the electro-etching time was 10 h.

[0143] After the electro-etching was completed, the anode was taken out, washed several times with deionized water, and dried in hot air at 80 °C for 12 h. After drying, a porous hydrotalcite product was obtained.

[0144] The porous hydrotalcite product prepared in this comparative example was placed under a scanning electron microscope for observation. The results are as Figure 6 shown.

[0145] From Figure 6 it can be seen that if the etching time is too long, too much substance on the hydrotalcite lamella will dissolve out, resulting in serious damage to the hydrotalcite lamella, so that the interpenetration between the nanosheets becomes loose and falls off.

[0146] Comparative Example 2

[0147] This comparative example provides a porous hydrotalcite material.

[0148] The porous hydrotalcite material is prepared by the following method:

[0149] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0150] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 10 V, and the electro-etching time is 5 h.

[0151] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 80 °C for 12 h. After drying, a porous hydrotalcite product is obtained.

[0152] The porous hydrotalcite product prepared in this comparative example is placed under a scanning electron microscope for observation. The results are as Figure 7 shown.

[0153] From Figure 7 it can be seen that if the etching voltage is too high, the bonds with stronger bond energy on the hydrotalcite lamellar will also break, resulting in serious damage to the hydrotalcite lamellar, and thus the interpenetration between the nanosheets becomes loose and falls off.

[0154] Comparative Example 3

[0155] This comparative example provides a porous hydrotalcite material.

[0156] The porous hydrotalcite material is prepared by the following method:

[0157] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 0.001 mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0158] The electro-etching system is externally connected to a DC electric field for electro-etching. The DC electric field voltage is 2.5 V, and the electro-etching time is 1 h.

[0159] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, and dried in hot air at 80 °C for 12 h. The product obtained after drying is placed under an electron microscope for observation. The results are as Figure 9 shown. From Figure 9 it can be seen that no porous structure is formed on the hydrotalcite nanosheets, which indicates that due to the too low concentration of the sodium chloride solution, the efficiency of the directional movement of the ions therein is too low, resulting in the failure of the preparation of the porous hydrotalcite.

[0160] Comparative Example 4

[0161] This comparative example provides a porous hydrotalcite material.

[0162] The porous hydrotalcite material is prepared by the following method:

[0163] Using a nickel-aluminum hydrotalcite in-situ loaded carbon fiber membrane as the anode, a graphite electrode as the cathode, and a 1mol / L sodium chloride solution as the electrolyte solution, an electro-etching system is constructed.

[0164] The electro-etching system is externally connected to a DC electric field for electro-etching. The voltage of the DC electric field is 2.5V, and the electro-etching time is 1h.

[0165] After the electro-etching is completed, the anode is taken out, washed several times with deionized water, dried in hot air at 200°C for 2h, and the product obtained after drying is observed under a scanning electron microscope. The results are as Figure 10 shown. As Figure 10 can be seen, the array composite structure in which nickel-aluminum hydrotalcite nanosheets are densely and evenly distributed on the carbon fiber surface is damaged. This is because at too high a temperature, the carbon fiber and the hydrotalcite molecules undergo a thermal decomposition process, and the carbon fiber and the hydrotalcite layer structure are damaged, resulting in the failure of the preparation of the porous hydrotalcite.

[0166] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of porous hydrotalcite, characterized in that, it is carried out according to the following steps: (1) An electro-etching system is constructed with a hydrotalcite in-situ supported carbon fiber membrane as the anode, an inert electrode as the cathode, and a sodium chloride solution as the electrolyte solution; among them, the concentration of the sodium chloride solution is 0.1 - 5 mol·L -1 ; (2) Perform electro-etching on the electro-etching system by connecting an external DC electric field; wherein, the voltage of the externally connected DC electric field is 0.1 - 9V; the electro-etching time is 0.5 - 5h; (3) After the electro-etching is completed, take out the anode, rinse it with deionized water, and dry it with hot air to obtain it; wherein, the temperature of the hot air drying is 60 - 150°C, and the drying time is 2 - 12h.

2. The preparation method of porous hydrotalcite according to claim 1, characterized in that, the hydrotalcite loaded on the carbon fiber membrane in situ is a layered hydrotalcite material of transition metal elements.

3. The preparation method of porous hydrotalcite according to claim 2, characterized in that, the layered hydrotalcite material of transition metal elements is any one of nickel-aluminum hydrotalcite, nickel-cobalt hydrotalcite, nickel-manganese hydrotalcite, and cobalt-aluminum hydrotalcite.

4. A porous hydrotalcite, characterized in that, it is prepared by using the preparation method of porous hydrotalcite according to any one of claims 1 - 3.

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