Preparation method and application of Cu-based material for in-situ preparation of Cu-based graphene catalyst

Abstract

The application relates to the field of catalytic material preparation and electrocatalysis technology, in particular to a preparation method and application of a Cu-based material in-situ preparation of a Cu-based graphene catalyst. The preparation method comprises the following steps: S1, alloy material preparation: mixing a copper oxide precursor, an aluminum source, a tin source and a zinc source in deionized water, ultrasonic dispersion after adding a dispersing agent, drying, calcining in H2 to obtain an alloy material; S2, pretreatment; S3, Cu-based graphene preparation; and S4, Cu-based graphene catalyst preparation. The application provides a preparation method and application of a Cu-based material in-situ preparation of a Cu-based graphene catalyst, so as to solve the problems of high energy consumption and weak interface bonding force in the preparation of a traditional Cu-based graphene catalytic electrode.

Description

Technical Field

[0001] This application relates to the fields of catalytic material preparation and electrocatalysis technology, and in particular to a method for preparing Cu-based graphene catalysts in situ using Cu-based materials and their application. Background Technology

[0002] Ammonia (NH3) is a crucial basic chemical in agriculture and the chemical industry. The traditional Haber-Bosch process for ammonia synthesis is energy-intensive and emits a large amount of carbon. Electrocatalytic nitrate reduction, as a mild and sustainable new route for ammonia synthesis, has attracted widespread attention in recent years. However, the main challenges currently facing electrocatalytic ammonia synthesis are: the lack of highly active, selective, and stable electrocatalysts; low Faraday efficiency; and complex and costly catalyst preparation processes, making large-scale production difficult.

[0003] Graphene due to its sp 2 Hybrid networks offer excellent conductivity, large specific surface area, and tunable electronic structure, making them ideal catalyst supports or active components. Meanwhile, numerous studies have shown that Cu exhibits high ammonia production selectivity, good activity, and stability in the electrocatalytic synthesis of ammonia from nitrates. Therefore, combining these two technologies holds promise for further improving the efficiency and Faradaic efficiency of electrocatalytic ammonia synthesis. However, directly loading metallic Cu onto graphene is difficult to achieve.

[0004] In recent years, studies have found that copper (Cu) exhibits good graphene generation ability in methane cracking due to its unique electronic structure and catalytic properties. However, while graphene can be supported on Cu, methane cracking requires high temperatures (>1250℃), which results in high energy consumption. Furthermore, Cu and graphene are mostly physically adsorbed, resulting in weak interfacial bonding. The interfacial bonding and activity regulation issues often make it difficult to achieve both ammonia production efficiency and Faradaic efficiency, thus restricting the large-scale application of Cu-based graphene catalysts in electrocatalytic ammonia synthesis. Summary of the Invention

[0005] This application provides a method for preparing Cu-based graphene catalysts in situ using Cu-based materials and its application, in order to solve the problems of high energy consumption and weak interfacial bonding in the preparation of traditional Cu-based graphene catalytic electrodes in related technologies.

[0006] In a first aspect, a method for preparing Cu-based graphene catalysts in situ using Cu-based materials is provided, comprising the following steps:

[0007] S1. Alloy material preparation:

[0008] The copper oxide precursor was mixed with aluminum, tin and zinc sources and dispersed in deionized water. After adding a dispersant, it was ultrasonically dispersed for 8-12 hours, dried at 145-185℃ and calcined in H2 for 32-44 hours to obtain the alloy material. The calcination temperature was 850-950℃.

[0009] S2, Pretreatment:

[0010] The alloy material is added to a 0.4-0.5 wt% aqueous solution of activator, dispersed at room temperature for 25-30 min, vacuum filtered, and dried at 58-60℃ for 1.5-2 h to complete the pretreatment.

[0011] The active agent is selected from tea saponin;

[0012] Preparation of S3 and Cu-based graphene:

[0013] The pretreated alloy material is heated to a liquid state, methane is introduced to the bottom of the liquid alloy, and Cu-based graphene is obtained after natural cooling.

[0014] Preparation of S4 and Cu-based graphene catalysts:

[0015] Cu-based graphene prepared by S3 was immersed in a composite modifier at a mass-volume ratio of 1g:10mL and impregnated at 45~50℃ in a nitrogen atmosphere for 2~4h. After vacuum filtration and vacuum drying, it was heated to 200~220℃ in a mixed gas and held for 1~1.5h to obtain Cu-based graphene catalyst.

[0016] Preferably, in S1, the proportions of the copper oxide precursor, aluminum source, tin source, and zinc source, based on atomic number, are: Cu: 45-60 parts, Al: 15-20 parts, Sn: 16-22 parts, Zn: 13-19 parts.

[0017] The aluminum source is selected from aluminum oxide, the tin source is selected from tin dioxide, and the zinc source is selected from metallic zinc.

[0018] Preferably, in step S1, the method for preparing the copper oxide precursor includes the following steps:

[0019] Add copper nitrate and sodium hydroxide to warm water, stir to dissolve quickly, adjust the pH to 8-9, filter after full reaction, and calcine the filter under an argon atmosphere to obtain a pure copper oxide precursor.

[0020] The temperature of the warm water is 60~75℃, and the calcination temperature is 340~450℃.

[0021] Preferably, the molar ratio of copper nitrate to sodium hydroxide is 1:(2.38~2.49).

[0022] Preferably, in step S3, the heating temperature is 650~800℃, and when methane is introduced to the bottom of the liquid alloy, the methane flow rate is 28~30mL / min, and the reaction is maintained at this temperature for 3~4h.

[0023] Preferably, in step S4, the composite modifier comprises a homogenizing agent and a reaction dispersion in a mass ratio of 1:2;

[0024] The homogenizing agent comprises tannic acid, glycyrrhizic acid, and anhydrous ethanol in a mass ratio of 5:(2~3):200;

[0025] The reaction dispersion comprises thioacetamide, melamine phosphate, and deionized water in a mass ratio of 1:(1.5~2):50.

[0026] Preferably, in step S4, after adding the composite modifier, the step further includes the following step:

[0027] Continue adding aluminum ammonium sulfate dodecahydrate, adjust the pH to 6-6.5, heat to 55-60℃ and react for 1-1.5 hours, add linoleic acid, stir for 20-30 minutes, and then perform vacuum filtration.

[0028] Secondly, the application of a catalyst prepared by an in-situ preparation method of Cu-based graphene catalyst based on any of the Cu-based materials described above in the preparation of Cu-based graphene catalytic electrodes is provided.

[0029] Preferably, the preparation method of the Cu-based graphene catalytic electrode includes:

[0030] The Cu-based material was used to prepare a Cu-based graphene catalyst in situ, which was dispersed in anhydrous ethanol. After ultrasonic treatment, a binder was added to obtain a coating solution. The coating solution was shaken well and coated onto conductive carbon paper. The solution was dried at 80~110℃ for 12~18h to obtain a Cu-based graphene catalytic electrode.

[0031] The Cu-based graphene catalytic electrode has a coating area of ​​1*1~2*2 cm on conductive carbon paper. 2 The volume of the coating solution applied to the conductive carbon paper is 60~120μL, and the number of coatings is 3~12 times.

[0032] The beneficial effects of the technical solution provided in this application include:

[0033] This application provides a method for preparing and applying Cu-based graphene catalysts in situ using Cu-based materials. A copper oxide precursor is combined with three low-melting-point metals (Al, Sn, and Zn) to form a eutectic quaternary alloy, effectively reducing the alloy's melting point and enabling methane cracking at 650-800℃ for in-situ preparation of Cu-based graphene. Metallic Cu grows in situ on the graphene surface, forming a tight metal-carbon interface, enhancing electron transport and improving the activity and stability of the electrocatalytic nitrate reduction reaction. Pretreatment with tea saponin achieves green dispersion of the alloy particles, preventing subsequent Cu agglomeration and graphene stacking. A composite modifier strengthens the interfacial chemical bond between Cu and graphene through complexation, inhibiting Cu dissolution and shedding during electrocatalysis. The preparation process is simple, energy-efficient, and effective, providing a good application scenario without the need for impurity removal. It also combines the unique properties of Cu in the electrocatalytic nitrate reduction reaction with the excellent electrical and physical properties of graphene. Therefore, it can solve the problems of high energy consumption and weak interfacial bonding in the preparation of traditional Cu-based graphene catalytic electrodes in related technologies. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart illustrating the in-situ preparation method of Cu-based graphene catalysts from Cu-based materials provided in this application.

[0036] Figure 2 X-ray diffraction pattern of the Cu-based graphene catalyst of Example 1 provided in this application;

[0037] Figure 3 X-ray diffraction pattern of Cu-based material provided in Example 1 of this application;

[0038] Figure 4 Schematic diagrams of ammonia production efficiency for Examples 1-4 and Comparative Examples 1-4 provided in this application;

[0039] Figure 5 Schematic diagrams of Faraday efficiency for Examples 1-4 and Comparative Examples 1-4 provided in this application. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] See Figures 1-5 As shown, this application provides a method for preparing Cu-based graphene catalysts in situ using Cu-based materials and their application.

[0042] Example 1

[0043] The method for preparing Cu-based graphene catalysts in situ using Cu-based materials provided in this embodiment includes the following steps:

[0044] S101, Alloy Material Preparation:

[0045] 1.72 mol of copper oxide precursor was mixed with 0.14 mol of aluminum oxide, 0.49 mol of tin dioxide, and 0.37 mol of zinc powder and dispersed in 500 mL of deionized water (stirred at 550 r / min). 2 mL of polyethylene glycol was added, and the mixture was ultrasonically dispersed for 8 h. After drying at 185 °C, the mixture was calcined at 930 °C with a heating rate of 5 °C / min. H2 was introduced, and the mixture was reduced for 32 h before cooling to obtain Cu. 60 Al 10 Sn 17 Zn 13 Alloy materials;

[0046] S102, Pretreatment:

[0047] The alloy material was added to a 0.5wt% aqueous solution of tea saponin, stirred and dispersed at 30℃ and 300r / min for 25min, then vacuum filtered (vacuum degree -0.08MPa), and dried at 60℃ for 1.5h to complete the pretreatment.

[0048] The tea saponin aqueous solution is a 500mL deionized water solution containing 2.5g of tea saponin.

[0049] Preparation of S103 and Cu-based graphene:

[0050] Pretreated Cu 60 Al 10 Sn 17 Zn 13The alloy material is heated to 800℃ in a tube furnace at a heating rate of 5℃ / min. At this point, the Cu-based material is in a liquid state. Methane is introduced into the bottom of the liquid alloy (methane flow rate 30mL / min, holding the reaction for 3h). The methane molecules are decomposed into carbon atoms and hydrogen gas. The carbon atoms rearrange in the liquid Cu-based alloy material to obtain Cu-based graphene, which floats to the top of the liquid alloy. After cooling to room temperature, the Cu-based graphene can be removed.

[0051] Preparation of S104 and Cu-based graphene catalysts:

[0052] 20g of Cu-based graphene prepared from S103 was immersed in 200mL of composite modifier and impregnated for 3h at 50℃ under a nitrogen atmosphere.

[0053] Continue adding aluminum ammonium sulfate dodecahydrate, adjust the pH to 6, raise the temperature to 60℃ and react for 1 hour, add 0.2 g linoleic acid, stir for 20 minutes, vacuum filter and vacuum dry, raise the temperature to 220℃ in a mixed gas and keep warm for 1 hour to obtain Cu-based graphene catalyst.

[0054] The method for preparing the copper oxide precursor in S101 is as follows:

[0055] Weigh 1.72 mol copper nitrate and 4.1 mol sodium hydroxide, add 500 mL of hot water (temperature 75℃), stir at 650 r / min to dissolve, adjust the pH to 8, and after complete reaction (no blue precipitate formed), filter through 0.22 μm microporous filter paper. Calcine the filter material at 450℃ under an argon atmosphere at a heating rate of 3℃ / min, hold for 2 h, and then cool to obtain the copper oxide precursor.

[0056] The composite modifier in S104 is a mixture of a homogenizing agent and a reaction dispersion in a mass ratio of 1:2.

[0057] The homogenizing agent is prepared by adding 5g of tannic acid and 3g of glycyrrhizic acid to 200g of anhydrous ethanol and stirring at 40℃ and 500r / min for 1h to obtain the homogenizing agent.

[0058] The reaction dispersion was prepared by dissolving 1g of thioacetamide and 2g of melamine phosphate in 50mL of deionized water and stirring at 50℃ for 20min to obtain the reaction dispersion.

[0059] Example 2

[0060] The method for preparing Cu-based graphene catalysts in situ using Cu-based materials provided in this embodiment includes the following steps:

[0061] S201, Alloy Material Preparation:

[0062] 1.57 mol of copper oxide precursor was mixed with 0.14 mol of aluminum oxide, 0.46 mol of tin dioxide, and 0.54 mol of zinc powder and dispersed in 400 mL of deionized water (stirred at 500 r / min). 2 mL of polyethylene glycol was added, and the mixture was ultrasonically dispersed for 12 h. After drying at 175 °C, the mixture was calcined at 910 °C with a heating rate of 5 °C / min, and H2 was introduced. After reduction for 36 h, the mixture was cooled to obtain Cu. 55 Al 10 Sn 16 Zn 19 Alloy materials;

[0063] S202, Pretreatment:

[0064] The alloy material was added to a 0.4 wt% aqueous solution of tea saponin, stirred and dispersed at 30℃ and 300 r / min for 30 min, then vacuum filtered (vacuum degree -0.08 MPa), and dried at 58℃ for 2 h to complete the pretreatment.

[0065] The tea saponin aqueous solution is a 500mL deionized water solution containing 2g of tea saponin.

[0066] Preparation of S2O3 and Cu-based graphene:

[0067] Pretreated Cu 55 Al 10 Sn 16 Zn 19 The alloy material is heated to 750°C in a tube furnace at a heating rate of 4°C / min. At this point, the Cu-based material is in a liquid state. Methane is introduced into the bottom of the liquid alloy (methane flow rate 28 mL / min, holding the reaction for 4 hours). The methane molecules are decomposed into carbon atoms and hydrogen gas. The carbon atoms rearrange in the liquid Cu-based alloy material to obtain Cu-based graphene, which floats to the top of the liquid alloy. After cooling to room temperature, the Cu-based graphene can be removed.

[0068] Preparation of S2O4 and Cu-based graphene catalysts:

[0069] 20g of Cu-based graphene prepared from S203 was immersed in 200mL of composite modifier and impregnated for 4h at 45℃ under a nitrogen atmosphere.

[0070] Continue adding aluminum ammonium sulfate dodecahydrate, adjust the pH to 6.5, raise the temperature to 55℃ and react for 1.5h, add 0.2g linoleic acid, stir for 30min, vacuum filter and vacuum dry, raise the temperature to 200℃ in a mixed gas and keep it at that temperature for 1.5h to obtain Cu-based graphene catalyst.

[0071] The method for preparing the copper oxide precursor in S201 is as follows:

[0072] Weigh 1.57 mol copper nitrate and 3.78 mol sodium hydroxide, add 500 mL of hot water (temperature 70℃), stir at 600 r / min to dissolve, adjust the pH to 9, and after complete reaction (no blue precipitate formed), filter through 0.45 μm microporous filter paper. Calcine the filter material at 410℃ under an argon atmosphere at a heating rate of 4℃ / min, hold for 3 h, and then cool to obtain the copper oxide precursor.

[0073] The composite modifier in S204 is a mixture of a homogenizing agent and a reaction dispersion in a mass ratio of 1:2.

[0074] The homogenizing agent is prepared by adding 5g tannic acid and 2g glycyrrhizic acid to 200g anhydrous ethanol and stirring at 40℃ and 500r / min for 1h to obtain the homogenizing agent.

[0075] The reaction dispersion was prepared by dissolving 1g of thioacetamide and 1.5g of melamine phosphate in 50mL of deionized water and stirring at 50℃ for 20min to obtain the reaction dispersion.

[0076] Example 3

[0077] The method for preparing Cu-based graphene catalysts in situ using Cu-based materials provided in this embodiment includes the following steps:

[0078] S301, Alloy Material Preparation:

[0079] 1.35 mol of copper oxide precursor was mixed with 0.2 mol of aluminum oxide, 0.59 mol of tin dioxide, and 0.59 mol of zinc powder and dispersed in 500 mL of deionized water (stirred at 500 r / min). 2 mL of polyethylene glycol was added, and the mixture was ultrasonically dispersed for 10 h. After drying at 165 °C, the mixture was calcined at 890 °C with a heating rate of 3 °C / min. H2 was introduced, and the mixture was reduced for 40 h before cooling to obtain Cu. 50 Al 15 Sn 22 Zn 13 Alloy materials;

[0080] S302, Pretreatment:

[0081] The alloy material was added to a 0.5wt% aqueous solution of tea saponin, stirred and dispersed at 30℃ and 300r / min for 30min, then vacuum filtered (vacuum degree -0.08MPa), and dried at 60℃ for 1.5h to complete the pretreatment.

[0082] The tea saponin aqueous solution is a 500mL deionized water solution containing 2.5g of tea saponin.

[0083] Preparation of S303 and Cu-based graphene:

[0084] Pretreated Cu 50 Al 15 Sn 22 Zn 13 The alloy material is heated to 700℃ in a tube furnace at a heating rate of 4℃ / min. At this point, the Cu-based material is in a liquid state. Methane is introduced into the bottom of the liquid alloy (methane flow rate 28mL / min, holding reaction for 3h). Methane molecules are decomposed into carbon atoms and hydrogen gas. The carbon atoms rearrange in the liquid Cu-based alloy material to obtain Cu-based graphene, which floats to the top of the liquid alloy. After cooling to room temperature, the Cu-based graphene can be removed.

[0085] Preparation of S304 and Cu-based graphene catalysts:

[0086] 20g of Cu-based graphene prepared from S303 was immersed in 200mL of composite modifier and impregnated for 2h in a nitrogen atmosphere at 50℃. After vacuum filtration and vacuum drying, the temperature was raised to 210℃ in a mixed gas and held for 1.5h to obtain Cu-based graphene catalyst.

[0087] The preparation method of the copper oxide precursor in S301 is as follows:

[0088] Weigh 1.35 mol copper nitrate and 3.26 mol sodium hydroxide, add 400 mL of hot water (temperature 65℃), stir at 550 r / min to dissolve, adjust the pH to 8, and after complete reaction (no blue precipitate formed), filter through 0.22 μm microporous filter paper. Calcine the filter material at 380℃ under an argon atmosphere at a heating rate of 5℃ / min, hold for 4 h, and then cool to obtain the copper oxide precursor.

[0089] The composite modifier in S304 is a mixture of a homogenizing agent and a reaction dispersion in a mass ratio of 1:2.

[0090] The homogenizing agent is prepared by adding 5g of tannic acid and 3g of glycyrrhizic acid to 200g of anhydrous ethanol and stirring at 40℃ and 500r / min for 1h to obtain the homogenizing agent.

[0091] The reaction dispersion was prepared by dissolving 1g of thioacetamide and 2g of melamine phosphate in 50mL of deionized water and stirring at 50℃ for 20min to obtain the reaction dispersion.

[0092] Example 4

[0093] The method for preparing Cu-based graphene catalysts in situ using Cu-based materials provided in this embodiment includes the following steps:

[0094] S401, Alloy Material Preparation:

[0095] 1.21 mol of copper oxide precursor was mixed with 0.27 mol of aluminum oxide, 0.54 mol of tin dioxide, and 0.4 mol of zinc powder and dispersed in 400 mL of deionized water (stirred at 500 r / min). 2 mL of polyethylene glycol was added, and the mixture was ultrasonically dispersed for 12 h. After drying at 145 °C, the mixture was calcined at 850 °C with a heating rate of 5 °C / min. H2 was introduced, and the mixture was reduced for 44 h before cooling to obtain Cu. 45 Al 20 Sn 20 Zn 15 Alloy materials;

[0096] S402, Pretreatment:

[0097] The alloy material was added to a 0.4 wt% aqueous solution of tea saponin, stirred and dispersed at 30℃ and 300 r / min for 25 min, then vacuum filtered (vacuum degree -0.08 MPa), and dried at 60℃ for 2 h to complete the pretreatment.

[0098] The tea saponin aqueous solution is a 500mL deionized water solution containing 2g of tea saponin.

[0099] Preparation of S403 and Cu-based graphene:

[0100] Pretreated Cu 45 Al 20 Sn 20 Zn 15 The alloy material is heated to 650°C in a tube furnace at a heating rate of 5°C / min. At this point, the Cu-based material is in a liquid state. Methane is introduced into the bottom of the liquid alloy (methane flow rate 30 mL / min, holding the reaction for 4 hours). The methane molecules are decomposed into carbon atoms and hydrogen gas. The carbon atoms rearrange in the liquid Cu-based alloy material to obtain Cu-based graphene, which floats to the top of the liquid alloy. After cooling to room temperature, the Cu-based graphene can be removed.

[0101] Preparation of S404 and Cu-based graphene catalysts:

[0102] 20g of Cu-based graphene prepared from S403 was immersed in 200mL of composite modifier and impregnated for 3h in a nitrogen atmosphere at 45℃. After vacuum filtration and vacuum drying, the temperature was raised to 220℃ in a mixed gas and held for 1h to obtain Cu-based graphene catalyst.

[0103] The method for preparing the copper oxide precursor in S401 is as follows:

[0104] Weigh 1.21 mol of copper nitrate and 3.02 mol of sodium hydroxide, add 400 mL of hot water (temperature 60℃), stir at 450 r / min to dissolve, adjust the pH to 9, and after complete reaction (no blue precipitate is formed), filter through 0.45 μm microporous filter paper. Calcine the filter material at 340℃ under an argon atmosphere at a heating rate of 3℃ / min, hold for 4 h, and then cool to obtain the copper oxide precursor.

[0105] The composite modifier in S404 is a mixture of a homogenizing agent and a reaction dispersion in a mass ratio of 1:2.

[0106] The homogenizing agent is prepared by adding 5g of tannic acid and 3g of glycyrrhizic acid to 200g of anhydrous ethanol and stirring at 40℃ and 500r / min for 1h to obtain the homogenizing agent.

[0107] The reaction dispersion was prepared by dissolving 1g of thioacetamide and 2g of melamine phosphate in 50mL of deionized water and stirring at 50℃ for 20min to obtain the reaction dispersion.

[0108] Comparative Example 1

[0109] This comparative example uses commercial graphene as a catalyst.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that the pretreatment in step S102 is not performed, and step S104 is not performed. The Cu-based graphene obtained after the original treatment in S103 is used as the Cu-based graphene catalyst.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 1 is that the pretreatment in step S102 is not performed, and the composite modifier in step S104 is replaced with an equal amount of homogenizing agent.

[0114] See Figure 2 and Figure 3 As shown, these are the X-ray diffraction patterns and X-ray diffraction patterns of the Cu-based graphene catalyst prepared in Example 1, respectively.

[0115] Figure 2 The Cu-based graphene catalyst prepared by Example 1 is shown, which has obvious and sharp graphene characteristic peaks (approximately 26.5°) and Cu characteristic peaks (approximately 43.2°), indicating that it has a high content and high crystallinity. The diffraction peaks of other elements are small, indicating that their content is low. This shows that the graphene catalyst mainly composed of Cu was successfully prepared. Figure 3 The Cu-based material (Cu) of Example 1 is shown. 60Al 10 Sn 17 Zn 13 The diffraction peaks of Cu, Al, Sn and Zn all indicate that Cu-based materials were successfully prepared.

[0116] Furthermore, this paper provides an application of Cu-based graphene catalyst prepared in situ using Cu-based materials in Cu-based graphene catalytic electrodes, specifically applied to the electrocatalytic reduction of nitrate to ammonia.

[0117] The Cu-based materials prepared in the above examples and comparative examples were used to prepare Cu-based graphene catalysts (hereinafter referred to as catalysts) in situ as Cu-based graphene catalytic electrodes:

[0118] x mg of catalyst was mixed with y mL of anhydrous ethanol and sonicated for 45 min to disperse it evenly. z μL of Nafion solution was added as a binder. n μL of the solution was evenly coated on conductive carbon paper (1*1.5 cm / 2*2.5 cm) in 6 portions, with a corresponding coating area of ​​1*1 or 2*2 cm. After drying for a certain period of time, Cu-based graphene catalytic electrode was obtained. The specific values ​​of x, y, z, n and related parameters are shown in Table 1.

[0119] Table 1

[0120]

[0121] The Cu-based graphene catalytic electrode prepared according to Table 1 was fixed on an electrode clamp. An H-type electrolytic cell was used, and 1 M KOH and 0.1 M KNO3 electrolyte (40 mL) were added to the anode and cathode of the electrolytic cell, respectively. The working electrode, counter electrode (platinum sheet) and reference electrode (Hg / HgO electrode) were inserted. A constant potential activity test was performed for 1 h at a potential of -0.5 V vs. RHE. After the test, the ammonia production efficiency and faradaic efficiency were calculated to evaluate the catalytic performance of the Cu-based graphene catalyst.

[0122] See Figure 3 and Figure 4The figures show the ammonia production efficiency and Faraday efficiency of Examples 1-4 and Comparative Examples 1-4, respectively. It can be seen that as the reduction calcination temperature decreases, both the ammonia production efficiency and Faraday efficiency first increase and then decrease. In Example 2, 910℃ is the optimal calcination temperature, resulting in moderate Cu active site grain size and the best dispersibility. Furthermore, the Zn content in the alloy is increased to 19%, which can regulate the electron cloud density of Cu, lower the N≡N bond dissociation barrier, and promote ammonia formation. Excessive temperature leads to alloy grain growth and Cu site agglomeration, while insufficient temperature leads to incomplete alloy reduction and a decrease in the number of active sites, both of which reduce ammonia production efficiency. Increasing the Al content enhances the alloy's corrosion resistance and reduces Cu dissolution during electrocatalysis; therefore, the Faraday efficiency in Example 4 remains at a high level.

[0123] Comparative Example 3 replaced the composite modifier with a single homogenizing agent. The homogenizing agent can improve the interfacial bonding force to a certain extent, thus the ammonia production efficiency and Faraday efficiency are at a relatively high level. Comparative Example 4 is pure Cu powder, which lacks the conductive and dispersive support of graphene. The Cu sites are prone to agglomeration, and the hydrogen evolution side reaction is serious. The commercial graphene in Comparative Example 1 has no catalytic effect of Cu active sites, and its effect on nitrate (NO3) is relatively poor. - The activation ability of the two is extremely poor, and their performance is far lower than that of the example.

[0124] Tea saponin, as a natural surfactant, reduces the surface tension of alloy particles and prevents agglomeration. Thioacetamide and melamine phosphate in the reaction dispersion introduce S, N, and P doping sites, increasing the number of defect sites in graphene, improving the ammonia production rate, and preserving the conductivity of graphene itself. In the homogenizing agent, the phenolic hydroxyl and carboxyl groups of tannic acid and glycyrrhizic acid can form hydrogen bonds with the hydroxyl groups on the graphene surface, while the phenolic hydroxyl groups of tannic acid can form complex bonds with Cu sites. Glycyrrhizic acid can inhibit graphene sheet stacking. Ammonium sulfate (ammonium aluminum sulfate dodecahydrate) provides Al doping auxiliary sites, forming multi-component doping with S, N, and P to construct abundant defects. The unsaturated bonds of linoleic acid can undergo addition reactions with the double bonds at the graphene edge, further inhibiting sheet stacking and improving ammonia production efficiency and Faraday efficiency.

[0125] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing Cu-based material in-situ into Cu-based graphene catalyst, characterized in that, It comprises the following steps: S1, alloy material preparation: Mix copper oxide precursor, aluminum source, tin source and zinc source in deionized water, add dispersant and ultrasonic dispersion for 8-12h, dry at 145-185℃, calcine in H2for 32-44h to obtain alloy material, the calcination temperature is 850-950℃; S2, pretreatment: Add the alloy material to 0.4-0.5wt% active agent aqueous solution, disperse at room temperature for 25-30min, vacuum filter, dry at 58-60℃ for 1.5-2h to complete the pretreatment; The active agent is selected from tea saponin; S3, Cu-based graphene preparation: Heat the pretreated alloy material to liquid state, introduce methane into the bottom of the liquid alloy, and obtain Cu-based graphene after natural cooling; S4, Cu-based graphene catalyst preparation: Immerse the Cu-based graphene prepared in S3 in the composite modifier at a mass-volume ratio of 1g:10mL, immerse in a nitrogen atmosphere at 45-50℃ for 2-4h, vacuum filter and vacuum dry, heat to 200-220℃ in a mixed gas, and keep warm for 1-1.5h to obtain Cu-based graphene catalyst.

2. The preparation method of claim 1, wherein: In S1, the atomic ratio of copper oxide precursor, aluminum source, tin source and zinc source is: Cu:45-60 parts, Al:15-20 parts, Sn:16-22 parts, Zn:13-19 parts; The aluminum source is selected from aluminum oxide, the tin source is selected from tin dioxide, and the zinc source is selected from metallic zinc.

3. The preparation method of claim 1, wherein: In S1, the preparation method of copper oxide precursor comprises the following steps: Add copper nitrate and sodium hydroxide to warm water, stir to dissolve quickly, adjust the pH value to 8-9, filter after sufficient reaction, and calcine the filtrate in an argon atmosphere to obtain pure copper oxide precursor; The temperature of the warm water is 60-75℃, and the calcination temperature is 340-450℃.

4. The preparation method of claim 3, wherein: The molar ratio of copper nitrate to sodium hydroxide is 1:(2.38-2.49).

5. The preparation method of claim 1, wherein: In S3, the heating temperature is 650-800℃, when methane is introduced into the bottom of the liquid alloy, the flow rate of methane is 28-30mL / min, and the heat preservation reaction time is 3-4h.

6. The preparation method of claim 1, wherein: In S4, the composite modifier includes a homogeneous agent and a reaction dispersion liquid at a mass ratio of 1:2; The homogeneous agent includes tannic acid, glycyrrhizic acid and anhydrous ethanol at a mass ratio of 5:(2-3):

200. The reaction dispersion liquid comprises thioacetamide, melamine phosphate and deionized water in a mass ratio of 1:(1.5-2):

50.

7. The method according to claim 1 or 6, wherein the Cu-based material is prepared in situ to obtain the Cu-based graphene catalyst. In the S4, after adding the composite modifier, the following steps are further included: Continue to add aluminum ammonium sulfate dodecahydrate, adjust the pH to 6-6.5, and react at 55-60°C for 1-1.5h, then add linoleic acid, stir for 20-30min, and perform vacuum filtration.

8. The application of the catalyst prepared by the method according to any one of claims 1-7 in the preparation of a Cu-based graphene catalytic electrode.

9. Use according to claim 8, wherein the compound is ###0006### The method for preparing the Cu-based graphene catalytic electrode comprises: The Cu-based material is prepared in situ to obtain the Cu-based graphene catalyst, which is dispersed in anhydrous ethanol, and a binder is added after ultrasonic treatment to obtain a coating solution, which is coated on a conductive carbon paper after being shaken, and is dried at 80-110°C for 12-18h to obtain the Cu-based graphene catalytic electrode. The coating area of the Cu-based graphene catalytic electrode on the conductive carbon paper is 1*1~2*2 cm 2 The volume of the coating solution coated on the conductive carbon paper is 60~120 μL, and the coating times are 3~12 times.

Images