Ag-cu composite metal aerogel, preparation method and application thereof

Abstract

This invention relates to the field of aerogel preparation technology, and discloses an Ag-Cu composite metal aerogel, its preparation method, and its applications. The method includes: contacting Cu(NO3)2·3H2O with a reducing agent in the presence of solvent I to carry out a first reaction, obtaining mixture I; contacting mixture I with AgNO3 in the presence of solvent II to carry out a second reaction, obtaining solid I; washing solid I and then subjecting solid II to solvent replacement and drying sequentially to obtain the Ag-Cu composite metal aerogel. The Ag-Cu composite metal aerogel prepared by the method provided by this invention has the characteristics of fine particles and uniform metal distribution, and also possesses a nanoporous structure.

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology, specifically to an Ag-Cu composite metal aerogel, its preparation method, and its application. Background Technology

[0002] With the acceleration of global industrialization, carbon dioxide (CO2) emissions have increased, exacerbating the greenhouse effect and posing a serious threat to the environment and human society. Electrocatalytic CO2 reduction reaction, as an effective means of converting CO2 into high-value-added chemicals (such as carbon monoxide, formic acid, and methanol) and clean fuels, has attracted widespread attention. This technology can not only reduce CO2 emissions but also achieve the recycling of carbon resources, which has significant economic and environmental implications.

[0003] In the electrocatalytic CO2 production process, the performance of the catalyst plays a crucial role. Currently, common electrocatalysts mainly include noble metal-based catalysts (such as Au, Ag, Pd, etc.), transition metal-based catalysts (such as transition metal oxides, sulfides, nitrides, etc.), and non-metallic catalysts (such as carbon-based materials). However, these catalysts face several unresolved issues. For example, while noble metal-based catalysts exhibit high catalytic activity and selectivity, their high cost and scarcity limit their large-scale application; transition metal-based catalysts, although lower in cost, often suffer from insufficient active sites, poor conductivity, and inadequate stability, resulting in room for improvement in their catalytic performance.

[0004] Aerogels are novel nanomaterials with high specific surface area, low density, and porous structure, showing great application potential in the field of electrocatalysis. Their unique porous structure provides abundant active sites, promoting the transport of reactants and products and improving the efficiency of catalytic reactions. However, currently reported aerogel materials for CO2 electrocatalysis still have some structural and performance defects. On the one hand, existing composite metal aerogels often suffer from large metal particle size and uneven distribution, which leads to insufficient exposure of active sites, affecting the activity and selectivity of the catalyst. On the other hand, many aerogels lack effective cavity structures, which are detrimental to the transport of reactants and electrons, thereby reducing the rate and efficiency of the catalytic reaction.

[0005] Currently, although some research reports have been published on the preparation of composite metal aerogels, specific structural designs and preparation methods for optimizing electrocatalytic CO2 performance still need further exploration. For example, Jiangsu Suopu Company proposed in-situ growth of metal aerogels on porous conductive supports, obtaining self-supporting electrodes through gelation of metal nanoparticle colloidal solutions, solvent exchange, and freeze-drying. However, this method lacks sufficient control over the size and distribution of metal particles, which may lead to limited active site density. In addition, the traditional freeze-drying process may damage the cavity structure of the aerogel, affecting mass transfer efficiency. The Liu Tianxi research group at Jiangnan University controlled the Cu-In metal aerogel interface ratio through salting-out gelation and found that aerogels with high Cu / Cu2In interface abundance exhibited a CO Faradaic efficiency of 94.5% in CO2 reduction. However, the uniformity of metal particles during its preparation process still needs optimization, and the controllability of the cavity structure is not fully realized, which may limit reactant diffusion and active site exposure. Similarly, while the Pt-Ni bundled nanocage aerogel developed by Sun Yat-sen University possesses a three-dimensional porous network, its synthesis relies on the noble metal (Pt), resulting in high costs, and it lacks targeted design for the cavity structure required for CO2 reduction. Therefore, achieving miniaturization and uniform distribution of metal particles through rational material design and fabrication processes, while simultaneously constructing an effective nanoporous structure, is a major challenge in this field.

[0006] In view of this, it is necessary to provide a composite metal aerogel that combines the advantages of high activity, high stability and low cost, so as to provide a new solution for the industrial application of electrocatalytic CO2 reduction. Summary of the Invention

[0007] The purpose of this invention is to provide a composite metal aerogel with fine particles, uniform metal distribution, and a nanoporous structure.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing Ag-Cu composite metal aerogels, the method comprising:

[0009] (1) In the presence of solvent I, Cu(NO3)2·3H2O is contacted with a reducing agent to carry out a first reaction to obtain mixture I; the conditions for the first reaction are at least: temperature of 5-50℃ and time of 1-5min.

[0010] (2) In the presence of solvent II, the mixture I is contacted with AgNO3 to carry out a second reaction to obtain solid I;

[0011] (3) Solid I was washed and then solid II was subjected to solvent replacement and drying in sequence to obtain the Ag-Cu composite metal aerogel;

[0012] The molar ratio of Cu(NO3)2·3H2O, AgNO3, and the reducing agent is 1:0.50-0.75:1.5-5.

[0013] A second aspect of the present invention provides an Ag-Cu composite metal aerogel prepared by the method described in the first aspect above.

[0014] A third aspect of the present invention provides an application of the Ag-Cu composite metal aerogel described in the second aspect above in the electrocatalytic reduction of CO2.

[0015] This invention synthesizes a composite metal aerogel with fine particles, uniform metal distribution, and a cavity structure by controlling the contact sequence of the reaction raw materials to generate an appropriate micro-perturbation effect, while controlling the ratio of the two metals and combining it with other technical features. Attached Figure Description

[0016] Figure 1 This is a SEM image of Ag-Cu composite metal aerogel J1 prepared in Example 1 of this invention;

[0017] Figure 2 This is a SEM image of Ag-Cu composite metal aerogel J2 prepared in Example 2 of this invention;

[0018] Figure 3 This is a SEM image of the Ag-Cu composite metal aerogel DJ1 prepared in Comparative Example 1 of this invention;

[0019] Figure 4 This is a SEM image of the Ag-Cu composite metal aerogel DJ2 prepared in Comparative Example 2 of this invention;

[0020] Figure 5 This is a SEM image of the final product DJ3 prepared in Comparative Example 3 of this invention.

[0021] Figure 6 This is an SEM image of the final product DJ4 prepared in Comparative Example 4 of this invention.

[0022] Figure 7 This is a SEM image of the Cu metal aerogel DJ7 prepared in Comparative Example 7 of this invention.

[0023] Figure 8 This is a SEM image of the Ag metal aerogel DJ8 prepared in Comparative Example 8 of this invention.

[0024] Figure 9 This is a TEM image of the intermediate product mixture I prepared in Example 1 of the present invention;

[0025] Figure 10This is a TEM image of the intermediate product mixture I prepared in Comparative Example 5 of the present invention;

[0026] Figure 11 This is a TEM image of the intermediate product mixture I prepared in Comparative Example 6 of the present invention;

[0027] Figure 12 This is a TEM image of Ag-Cu composite metal aerogel J1 prepared in Example 1 of this invention;

[0028] Figure 13 This is a TEM image of Ag-Cu composite metal aerogel J2 prepared in Example 2 of this invention;

[0029] Figure 14 This is a distribution map of Ag and Cu elements in Ag-Cu composite metal aerogel J1 prepared in Example 1 of this invention;

[0030] Figure 15 This is a distribution diagram of Ag and Cu elements in Ag-Cu composite metal aerogel J2 prepared in Example 2 of the present invention. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] As previously described, a first aspect of the present invention provides a method for preparing Ag-Cu composite metal aerogels, the method comprising:

[0033] (1) In the presence of solvent I, Cu(NO3)2·3H2O is contacted with a reducing agent to carry out a first reaction to obtain mixture I; the conditions for the first reaction are at least: temperature of 5-50℃ and time of 1-5min.

[0034] (2) In the presence of solvent II, the mixture I is contacted with AgNO3 to carry out a second reaction to obtain solid I;

[0035] (3) Solid I was washed and then solid II was subjected to solvent replacement and drying in sequence to obtain the Ag-Cu composite metal aerogel;

[0036] The molar ratio of Cu(NO3)2·3H2O, AgNO3, and the reducing agent is 1:0.50-0.75:1.5-5.

[0037] The inventors of this invention discovered that when AgNO3 is reacted with a reducing agent in the first reaction and then reacted with Cu(NO3)2·3H2O in the second reaction, the nanoparticles adhere to the micron-sized blocks and cannot form a three-dimensional network cavity structure; when AgNO3 is reacted with Cu(NO3)2·3H2O in the first reaction and then reacted with a reducing agent in the second reaction, the sample exhibits a flocculent structure and also cannot form a three-dimensional network cavity structure.

[0038] Furthermore, the inventors of this invention also discovered that when the molar ratio of Cu(NO3)2·3H2O to AgNO3 is less than 1:0.50 or greater than 1:0.75, the particle size increases significantly. Additionally, when the initial reaction time is greater than 5 minutes, the particle size gradually increases with increasing reaction time.

[0039] In a preferred embodiment, the reducing agent is selected from at least one of NaBH4, KBH4, hydrazine hydrate, methanol, ethyl acetate, and n-hexane.

[0040] According to a preferred embodiment, in step (2), the conditions for the second reaction are at least: a temperature of 10-35°C and a time of 0.2-3h.

[0041] According to another preferred embodiment, in step (3), the conditions for solvent replacement are at least: an organic solvent is used, the number of replacements is 2-4, the interval is 1-3 hours, and the temperature is 15-40°C.

[0042] More preferably, the organic solvent is selected from at least one of ethanol, methanol, ethyl acetate, and n-hexane.

[0043] According to a particularly preferred embodiment, the drying conditions at least satisfy the following: temperature of 70-90°C and time of 2-4 hours.

[0044] According to another particularly preferred embodiment, both solvent I and solvent II are deionized water.

[0045] As previously stated, a second aspect of the present invention provides an Ag-Cu composite metal aerogel prepared by the method described in the first aspect.

[0046] As previously stated, a third aspect of the present invention provides an application of the Ag-Cu composite metal aerogel described in the second aspect above in the electrocatalytic reduction of CO2.

[0047] Preferably, the Faraday efficiency of CO obtained by electrocatalytic reduction of CO2 is at least 90%.

[0048] The present invention will be described in detail below through examples.

[0049] In the following examples, unless otherwise specified, all raw materials used were commercially purchased.

[0050] Example 1

[0051] (1) In the presence of deionized water (solvent I), Cu(NO3)2·3H2O is contacted with NaBH4 (reducing agent) to carry out the first reaction, and mixture I is obtained;

[0052] The conditions for the first reaction are: temperature 25℃, time 1 min;

[0053] (2) In the presence of deionized water (solvent II), mixture I is reacted with AgNO3 in a second reaction, and solid-liquid separation is performed to obtain solid I;

[0054] The conditions for the second reaction are: temperature 25℃ and time 12h;

[0055] The molar ratio of Cu(NO3)2·3H2O, AgNO3, and reducing agent is 1:0.50:1.25;

[0056] (3) Solid I was washed five times with deionized water and solid-liquid separation was performed to obtain solid II; solid II was then subjected to solvent replacement and drying in sequence.

[0057] The solvent replacement conditions were: anhydrous ethanol was used, the number of replacements was 3, the interval was 2 hours, and the temperature was 30℃.

[0058] The drying conditions were: temperature 80℃, time 3 hours;

[0059] Ag-Cu composite metal aerogel J1 was prepared.

[0060] Example 2

[0061] This embodiment uses a method similar to that of Embodiment 1, except that:

[0062] In step (1), the amount of AgNO3 was adjusted so that the molar ratio of Cu(NO3)2·3H2O, AgNO3 and reducing agent was 1:0.75:1.25. All other conditions were the same as in Example 1, and Ag-Cu composite metal aerogel J2 was prepared.

[0063] Comparative Example 1

[0064] This comparative example was conducted using a method similar to that of Example 1, except that:

[0065] In step (1), the amount of AgNO3 was adjusted so that the molar ratio of Cu(NO3)2·3H2O, AgNO3 and reducing agent was 1:1:1.25. All other conditions were the same as in Example 1, and Ag-Cu composite metal aerogel DJ1 was prepared.

[0066] Comparative Example 2

[0067] This comparative example was conducted using a method similar to that of Example 1, except that:

[0068] In step (1), the amount of AgNO3 was adjusted so that the molar ratio of Cu(NO3)2·3H2O, AgNO3 and reducing agent was 1:0.05:1.25. All other conditions were the same as in Example 1, and Ag-Cu composite metal aerogel DJ2 was prepared.

[0069] Comparative Example 3

[0070] This comparative example was conducted using a method similar to that of Example 1, except that:

[0071] The reaction order of Cu(NO3)2·3H2O and AgNO3 was adjusted, while all other conditions remained the same as in Example 1, to prepare the product DJ3.

[0072] Comparative Example 4

[0073] This comparative example was conducted using a method similar to that of Example 1, except that:

[0074] The reaction order of AgNO3 and the reducing agent was adjusted, while all other conditions remained the same as in Example 1, to prepare product DJ4.

[0075] Comparative Example 5

[0076] This comparative example was conducted using a method similar to that of Example 1, except that:

[0077] In step (1), the time of the first reaction was adjusted to 10 min, and the other conditions were the same as in Example 1, to obtain Ag-Cu composite metal aerogel DJ5.

[0078] Comparative Example 6

[0079] This comparative example was conducted using a method similar to that of Example 1, except that:

[0080] In step (1), the time of the first reaction was adjusted to 30 min, and the other conditions were the same as in Example 1, to obtain Ag-Cu composite metal aerogel DJ6.

[0081] Comparative Example 7

[0082] This comparative example was conducted using a method similar to that of Example 1, except that:

[0083] Without performing step (2), all other conditions were the same as in Example 1, and Cu metal aerogel DJ7 was obtained.

[0084] Comparative Example 8

[0085] This comparative example was conducted using a method similar to that of Example 1, except that:

[0086] Step (2) was omitted, and Cu(NO3)2·3H2O was replaced with an equimolar amount of AgNO3. All other conditions were the same as in Example 1, and Ag metal aerogel DJ8 was obtained.

[0087] Comparative Example 9

[0088] This comparative example was conducted using a method similar to that of Example 1, except that:

[0089] When Cu(NO3)2·3H2O was replaced with an equimolar amount of CuCl2, and all other conditions were the same as in Example 1, AgCl precipitate was formed.

[0090] Test case

[0091] The aerogels prepared in the examples and comparative examples were tested for catalytic performance using the following methods:

[0092] The CO2 electrocatalytic reduction reaction is carried out in an H-type electrolytic cell using a three-electrode system. In this system, the working electrode (cathode) is hydrophobic carbon paper loaded with a catalyst, a mercury-mercury oxide standard electrode serves as the reference electrode, and a graphite rod electrode serves as the counter electrode (anode). The cathode electrolyte is 28 mL of CO2-saturated 0.5 M KHCO3, and the anolyte is 23 mL of 0.25 M K2CO3. The anode and cathode halves of the H-type electrolytic cell are separated by a Nafion proton exchange membrane. Specifically, as follows:

[0093] First, a cyclic voltammetry scan was performed at a scan rate of 100 mV·s. -1 The voltage range was 0.1V to 1.2V (vs. RHE). A linear voltammetric scan was then performed at a scan rate of 100mV·s. -1The voltage range is from 0 to -1.1V (vs. RHE). After three scans alternating between the two, the H-type electrolytic cell is sealed and its airtightness is checked. Only after these preparations are completed can the chronoamperometry test be performed. After each potential test, CO2 gas is introduced into the cathode chamber for 10 minutes under stirring at 500 rpm to remove the reduction products generated at the previous potential and to resaturate the electrolyte with CO2. After the chronoamperometry test runs for at least 30 minutes, the yield of gaseous products (mainly H2 and CO) is quantitatively detected using a flame ionization detector (FID) and thermal conductivity detector (TCD) of a gas chromatograph, using high-purity argon as the carrier gas.

[0094] Table 1

[0095]

[0096]

[0097] As can be seen from the results in Table 1, the Ag-Cu composite metal aerogel prepared by the method provided in this invention has good electrocatalytic reduction activity for CO2 and CO selectivity (high Faraday efficiency).

[0098] Figures 1-4 , Figure 7 and Figure 8 These are SEM images of the metal aerogels prepared in Examples 1, 2, 1, 2, 7, and 8 of this invention. Figure 5 and Figure 6 These are SEM images of the final products prepared in Comparative Examples 3 and 4 of this invention, respectively. Figure 1 and Figure 2 As can be seen, the Ag-Cu composite metal aerogel prepared by the method provided in this invention has fine particles, with sizes of 41.0 nm and 27.7 nm, respectively; from Figure 3 and Figure 4 It can be seen that when the molar ratio of Cu(NO3)2·3H2O to AgNO3 is outside the range required by this invention, the Ag-Cu composite metal aerogel particles are relatively large, at 472.3 nm and 299.6 nm, respectively; from Figure 7 and Figure 8 As can be seen, the synthesized Cu metal aerogels or Ag metal aerogels also have relatively large particle sizes, at 65.6 nm and 77.0 nm, respectively; from Figure 5 and Figure 6 As can be seen, when the contact sequence of Cu(NO3)2·3H2O, AgNO3 and reducing agent is not performed in accordance with the requirements of this invention, the expected aerogel structure cannot be obtained.

[0099] Figures 9-11 These are TEM images of intermediate product mixture I prepared in Examples 1, 5, and 6 of this invention. As can be seen from the images, the particle size of mixture I gradually increases with the extension of the first reaction time, reaching 2.2 nm, 5.7 nm, and 6.1 nm, respectively.

[0100] Figure 12 and Figure 13 The images show TEM images of the metal aerogels prepared in Examples 1 and 2 of this invention, respectively. As can be seen from the images, the nanoparticles contain many small pores, which gives the prepared aerogels better catalytic performance.

[0101] Figure 14 and Figure 15 These are elemental distribution diagrams of the metal aerogels prepared in Examples 1 and 2 of this invention, respectively. As can be seen from the diagrams, Ag and Cu elements are uniformly distributed in the aerogels.

[0102] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing Ag-Cu composite metal aerogel, characterized in that, The method includes: (1) In the presence of solvent I, The mixture is brought into contact with a reducing agent to carry out a first reaction, yielding mixture I; the conditions for the first reaction are at least: temperature of 5-50°C and time of 1-5 min. (2) In the presence of solvent II, the mixture I is contacted with AgNO3 to carry out a second reaction to obtain solid I; the conditions for the second reaction are at least: temperature of 10-35℃ and time of 0.2-3h; (3) Solid I was washed and then solid II was subjected to solvent replacement and drying in sequence to obtain the Ag-Cu composite metal aerogel; The molar ratio of Cu(NO3)2∙3H2O, AgNO3, and the reducing agent is 1:0.50-0.75:1.5-5.

2. The method according to claim 1, wherein, In step (1), the reducing agent is selected from at least one of NaBH4, KBH4, hydrazine hydrate, glucose, and hydrogen peroxide.

3. The method according to claim 1 or 2, wherein, In step (3), the conditions for solvent replacement must at least be met: an organic solvent is used, the number of replacements is 2-4, the interval is 1-3 hours, and the temperature is 15-40℃.

4. The method according to claim 3, wherein, In step (3), the organic solvent is selected from at least one of ethanol, methanol, ethyl acetate, and n-hexane.

5. The method according to claim 1 or 2, wherein, In step (3), the drying conditions must at least meet the following requirements: temperature of 70-90℃ and time of 2-4h.

6. The method according to claim 1 or 2, wherein, In steps (1) and (2), both solvent I and solvent II are deionized water.

7. Ag-Cu composite metal aerogel prepared by the method according to any one of claims 1-6.

8. The application of the Ag-Cu composite metal aerogel according to claim 7 in the electrocatalytic reduction of CO2.

9. The application according to claim 8, wherein, The Faraday efficiency of CO obtained by electrocatalytic reduction of CO2 is at least 90%.

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