A bifunctional catalytic electrode and a preparation method and application thereof

Abstract

The application provides a bifunctional catalytic electrode and a preparation method and application thereof. The bifunctional catalytic electrode comprises carbon paper and a catalytic material loaded on the surface of the carbon paper, wherein the catalytic material comprises cobalt hydroxide and basic copper salt loaded on the cobalt hydroxide, the crystal form of the cobalt hydroxide is beta type, and the basic copper salt is selected from Cu2(OH)3Cl or Cu2(OH)3NO3. The catalytic electrode of the application adopts cobalt hydroxide catalytic material modified by basic copper salt, has more catalytic active sites and synergistic catalytic effect, has high activity and excellent stability in the reaction process of electrocatalytic synthesis of ammonia and co-production of formate, can realize more than 90% of the faradic efficiency of ammonium and formate in a wide potential window, and has excellent stability in the cyclic test process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic nanomaterials, in particular to a bifunctional catalytic electrode and a preparation method and application thereof. BACKGROUND

[0002] Electrocatalysis technology is an effective means for efficiently treating and utilizing biomass resources to produce high-value-added chemicals. Nitrite is an organic pollutant widely used in various organisms and environments, which is not only an important factor causing environmental pollution, but also has a serious harm to human and animal health. Therefore, it is of great significance to study the nitrite pollution control technology. Glycerol is a representative polyol and is also the main byproduct of the biofuel industry, and is one of the highest-yielding products among hundreds of biomass-derived intermediates. Glycerol can be converted into upgraded products (such as formic acid, etc.), which has good economic benefits. In the past few decades, various metal-based materials have been developed into electroactive catalysts for electrocatalytic nitrate reduction to produce ammonia or electrocatalytic glycerol oxidation to formate. Among these catalysts, cobalt-based materials have attracted widespread attention due to their relatively high activity, low cost and good stability, however, these electrocatalysts often have a too high potential, which cannot meet the actual application. SUMMARY

[0003] (I) Technical problems solved

[0004] In view of the deficiencies in the prior art, the present application provides a bifunctional catalytic electrode and a preparation method and application thereof, which adopts a composite catalytic material formed by an alkaline copper salt and a cobalt hydroxide material to solve the problems raised in the above background technology.

[0005] (II) Technical solutions

[0006] To achieve the above object, the present application is implemented by the following technical solutions:

[0007] According to a first aspect of the present application, a bifunctional catalytic electrode is provided, comprising a carbon paper and a catalytic material loaded on the surface of the carbon paper, the catalytic material comprising a cobalt hydroxide and an alkaline copper salt loaded on the cobalt hydroxide, the crystal form of the cobalt hydroxide being β type, and the alkaline copper salt being selected from Cu2(OH)3Cl or Cu2(OH)3NO3.

[0008] Preferably, the catalytic material is in a sheet-like nanostructure, and the size of the sheet-like nanostructure is 50-200 nm.

[0009] Preferably, the molar ratio of the alkaline copper salt to the cobalt hydroxide is 1:5-15, wherein the molar amount of copper and cobalt is used to calculate the molar amount of the alkaline copper salt and the cobalt hydroxide, respectively.

[0010] The loading amount of the catalytic material on the carbon paper is 2-3 mg / cm 2 .

[0011] According to a second aspect of the present application, a preparation method of a bifunctional catalytic electrode is provided, comprising the following steps:

[0012] Step 1, mixing a cobalt salt, a copper salt, hexamethylene tetramine, ethanol and water to obtain a mixed solution by stirring;

[0013] Step 2, refluxing the mixed solution at 95°C to obtain a solid powder;

[0014] Step 3, dispersing the solid powder in a mixed solution containing ethanol and naphthol, and ultrasonic treatment to obtain a catalyst slurry;

[0015] Step 4, spraying the catalyst slurry on a carbon paper, and naturally drying to obtain the bifunctional catalytic electrode.

[0016] Preferably, in Step 1, the cobalt salt is selected from cobalt chloride hexahydrate or cobalt nitrate hexahydrate;

[0017] The copper salt is selected from copper chloride dihydrate or copper nitrate trihydrate.

[0018] Further preferably, when the cobalt salt is selected from cobalt chloride hexahydrate, the copper salt is selected from copper chloride dihydrate;

[0019] When the cobalt salt is selected from cobalt nitrate hexahydrate, the copper salt is selected from copper nitrate trihydrate.

[0020] Preferably, in Step 1, the molar ratio of the cobalt salt to the copper salt is 5-15:1;

[0021] The molar ratio of the cobalt salt to the hexamethylene tetramine is 1:1-3;

[0022] The mass ratio of the cobalt salt to the ethanol is 1g:10-20 mL;

[0023] The mass ratio of the cobalt salt to the water is 1g:120-160 mL.

[0024] Further preferably, the molar ratio of the cobalt salt to the copper salt is 10:1;

[0025] The molar ratio of the cobalt salt to the hexamethylene tetramine is 1:2.

[0026] Further preferably, when the cobalt salt is selected from cobalt chloride hexahydrate, the mass ratio of the cobalt chloride hexahydrate to the ethanol is 1g:15-20 mL, and the mass ratio of the cobalt chloride hexahydrate to the water is 1g:150-160 mL;

[0027] When the cobalt salt is selected from cobalt nitrate hexahydrate, the mass of cobalt nitrate hexahydrate to the volume of ethanol is 1 g: 10-15 mL, and the mass of cobalt nitrate hexahydrate to the volume of water is 1 g: 120-130 mL.

[0028] Further preferably, the volume ratio of the ethanol to the water is 1:9.

[0029] Preferably, in step 1, the stirring time is 15-30 min.

[0030] Preferably, in step 2, the refluxing time is 1-1.5 h.

[0031] Preferably, in step 3, the volume ratio of the solid powder to ethanol is 1 g: 100-200 mL.

[0032] The volume ratio of the ethanol to naphthol is 200:7.

[0033] According to a third aspect of the present application, there is provided a use of the bifunctional catalytic electrode or the bifunctional catalytic electrode obtained by the above preparation method in the electro-synthesis of ammonia co-production of formate.

[0034] (III) Beneficial Effects

[0035] The present application provides a bifunctional catalytic electrode, a preparation method and a use thereof. The present application has the following beneficial effects:

[0036] (1) The bifunctional catalytic electrode provided by the present application can induce the simultaneous synthesis of β-type cobalt hydroxide and basic copper salt by introducing copper salt, and the one-step synthesized composite material can help to expose more catalytically active sites and improve the electro-catalytic reaction kinetics, thereby significantly improving the catalytic activity of the material.

[0037] (2) The preparation method of the bifunctional catalytic electrode provided by the present application can direct synthesis of the composite catalytic material of β-Co(OH)2 and different basic copper salts (Cu2(OH)3Cl or Cu2(OH)3NO3) by heating and condensing reflux, and the preparation method is simple, the raw materials are common, easy to control and low in cost. The reflux device can realize rapid batch production of the electro-catalyst, and the production efficiency is high and the environment is friendly.

[0038] (3) The bifunctional catalytic electrode provided by the present application has high activity and excellent stability in the reaction process of electro-catalytic synthesis of ammonia co-production of formate, and in a wide potential window, the catalytic electrode can realize a faradic efficiency of more than 90% for ammonium and formate, and has excellent stability in the cyclic test process. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1X-ray diffraction patterns of the β-Co(OH)2 / Cu2(OH)3Cl catalytic material prepared in Example 1 of the present application and the β-Co(OH)2 / Cu2(OH)3NO3 catalytic material prepared in Example 2, wherein a is the X-ray diffraction pattern of the β-Co(OH)2 / Cu2(OH)3Cl catalytic material, and b is the X-ray diffraction pattern of the β-Co(OH)2 / Cu2(OH)3NO3 catalytic material;

[0040] Figure 2 Transmission electron microscope morphology images of the β-Co(OH)2 / Cu2(OH)3Cl catalytic material prepared in Example 1 of the present application, wherein a is the transmission electron microscope image of the β-Co(OH)2 / Cu2(OH)3Cl at 200 nm, and b is the high-resolution electron microscope image of the β-Co(OH)2 / Cu2(OH)3Cl at 5 nm;

[0041] Figure 3 X-ray photoelectron spectrograms of the β-Co(OH)2 / Cu2(OH)3Cl catalytic material prepared in Example 1 of the present application, wherein a is the XPS spectrum of Co 2p, and b is the XPS spectrum of Cu 2p;

[0042] Figure 4 Electrocatalytic nitrite reduction performance test diagrams of the catalytic materials prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present application, wherein a is the nitrite reduction linear voltammetry curve diagram in a mixed solution of 0.1M NaNO2 and 1M KOH, and b is the faradic efficiency comparison diagram of the ammonium product;

[0043] Figure 5 Electrocatalytic glycerol oxidation performance test diagrams of the catalytic materials prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present application, wherein a is the glycerol oxidation linear voltammetry curve diagram in a mixed solution of 0.1M glycerol and 1M KOH, and b is the formate faradic efficiency comparison diagram;

[0044] Figure 6 TEM images of the β-Co(OH)2 / Cu2(OH)3Cl catalytic material prepared in Example 1 of the present application before and after the electrocatalytic glycerol reaction 1 H NMR spectrograms;

[0045] Figure 7A chronoamperogram of a β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared in Example 1 of the present application, wherein a graph a is a chronoamperogram of NO2RR by a three-electrode method in a mixed solution of 0.1M NaNO2 and 1M KOH, and a graph b is a chronoamperogram of glycerol oxidation by a three-electrode method in a mixed solution of 0.1M glycerol and 1M KOH;

[0046] Figure 8 A linear voltammetry graph of a β-Co(OH)2 / Cu2(OH)3Cl catalytic material prepared in Example 1 of the present application measured in a membrane electrode assembly assembled in a mixed solution of 0.1M NaNO2 and 1M KOH and in a mixed solution of 0.1M glycerol and 1M KOH;

[0047] Figure 9 An electrolytic stability graph of a β-Co(OH)2 / Cu2(OH)3Cl catalytic material prepared in Example 1 of the present application measured in a membrane electrode assembly assembled in a mixed solution of 0.1M NaNO2 and 1M KOH and in a mixed solution of 0.1M glycerol and 1M KOH;

[0048] Figure 10 A performance comparison graph of catalytic materials with different Co / Cu molar ratios prepared in Example 1 to Example 6 and Comparative Example 1 and Comparative Example 2 of the present application for electrocatalytic glycerol oxidation. DETAILED DESCRIPTION

[0049] In order to better illustrate the content of the present application, the following specific examples are described.

[0050] Example 1

[0051] A preparation method of a bifunctional catalytic electrode, comprising the following steps:

[0052] Step 1, 476mg of cobalt chloride hexahydrate, 35mg of copper chloride dihydrate and 561mg of hexamethylene tetramine were dissolved in 8mL of anhydrous ethanol and 72mL of deionized water to mix, and stirred for 30min to obtain a pink mixed solution;

[0053] Step 2, the pink mixed solution was placed in a round-bottom flask, heated and condensed in a refluxing water bath at 95℃ for 1h, the product was centrifuged, washed and dried to obtain a β-Co(OH)2 / Cu2(OH)3Cl powder;

[0054] Step 3, 5 mg of β-Co(OH)2 / Cu2(OH)3Cl powder was dispersed in 1 mL of anhydrous ethanol and 35 μL of a 5 wt% naphthol solution to form a uniform catalyst slurry by ultrasonic treatment for 30 min;

[0055] Step 4, 500 μL of the catalyst slurry was uniformly sprayed on a 1 x 1 cm 2 hydrophilic carbon paper, and a catalytic electrode was obtained after natural drying, which was recorded as β-Co(OH)2 / Cu2(OH)3Cl, with a copper / cobalt molar ratio of 10%.

[0056] Example 2

[0057] The preparation method of this example was the same as that of Example 1, except that the mixed solution in Step 1 contained 582 mg of cobalt nitrate hexahydrate, 48 mg of copper nitrate trihydrate, 561 mg of hexamethylenetetramine, 8 mL of anhydrous ethanol, and 72 mL of deionized water, and the prepared catalytic electrode was recorded as β-Co(OH)2 / Cu2(OH)3NO3, with a copper / cobalt molar ratio of 10%.

[0058] Example 3

[0059] The preparation method of this example was the same as that of Example 1, except that the mixed solution in Step 1 contained 476 mg of cobalt chloride hexahydrate, 17.5 mg of copper chloride dihydrate, 561 mg of hexamethylenetetramine, 8 mL of anhydrous ethanol, and 72 mL of deionized water, and the prepared catalytic electrode was recorded as β-Co(OH)2 / Cu2(OH)3Cl, with a copper / cobalt molar ratio of 5%.

[0060] Example 4

[0061] The preparation method of this example was the same as that of Example 1, except that the mixed solution in Step 1 contained 476 mg of cobalt chloride hexahydrate, 52.5 mg of copper chloride dihydrate, 561 mg of hexamethylenetetramine, 8 mL of anhydrous ethanol, and 72 mL of deionized water, and the prepared catalytic electrode was recorded as β-Co(OH)2 / Cu2(OH)3Cl, with a copper / cobalt molar ratio of 15%.

[0062] Example 5

[0063] The preparation method of this example was the same as that of Example 1, except that the mixed solution in Step 1 contained 582 mg of cobalt nitrate hexahydrate, 24 mg of copper nitrate trihydrate, 561 mg of hexamethylenetetramine, 8 mL of anhydrous ethanol, and 72 mL of deionized water, and the prepared catalytic electrode was recorded as β-Co(OH)2 / Cu2(OH)3NO3, with a copper / cobalt molar ratio of 5%.

[0064] Example 6

[0065] The preparation method of this example is the same as that of Example 1, except that the mixed solution in Step 1 contains 582 mg of cobalt nitrate hexahydrate, 72 mg of copper nitrate trihydrate, 561 mg of hexamethylene tetramine, 8 mL of anhydrous ethanol and 72 mL of deionized water, and the prepared catalytic electrode is denoted as β-Co(OH)2 / Cu2(OH)3NO3, with a copper / cobalt molar ratio of 15%.

[0066] Comparative Example 1

[0067] The preparation method of the α-Co(OH)2catalytic electrode comprises the following steps:

[0068] Step 1, 476 mg of cobalt chloride hexahydrate and 561 mg of hexamethylene tetramine were dissolved in a mixed solution of 8 mL of anhydrous ethanol and 72 mL of deionized water, and stirred for 30 min to obtain a pink mixed solution;

[0069] Step 2, the pink mixed solution was placed in a round-bottom flask and heated in a water bath at 95°C for 1 h under reflux condensation, and the product was centrifuged, washed and dried to obtain α-Co(OH)2powder;

[0070] Step 3, 5 mg of α-Co(OH)2powder was dispersed in a mixed solution of 1 mL of anhydrous ethanol and 35 μL of naphthol with a mass concentration of 5 wt%, and ultrasonically treated for 30 min to form a uniform slurry;

[0071] Step 4, 500 μL of the uniform slurry was sprayed on a 1×1 cm 2 hydrophilic carbon paper, and a catalytic electrode was obtained after natural drying, denoted as α-Co(OH)2.

[0072] Comparative Example 2

[0073] The preparation method of this comparative example is the same as that of Example 1, except that the mixed solution in Step 1 contains 582 mg of cobalt nitrate hexahydrate, 561 mg of hexamethylene tetramine, 8 mL of anhydrous ethanol and 72 mL of deionized water, and the prepared catalytic electrode is denoted as β-Co(OH)2.

[0074] Performance test

[0075] The catalytic electrodes prepared in Example 1 and Example 2 were subjected to XRD analysis, as shown in Figure 1As shown in Figure a, the prepared β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode consists of two phases, β-Co(OH)2 and Cu2(OH)3Cl, which matches the standard sample (PDF#86-1391) in Figure a. Figure b shows that the synthesized β-Co(OH)2 / Cu2(OH)3NO3 catalytic electrode consists of two phases, β-Co(OH)2 and Cu2(OH)3NO3, which matches the standard sample (PDF#84-0599) in Figure b. This proves that the catalyst on the catalytic electrode prepared in this invention includes two phases, cobalt hydroxide and basic copper salt, and the cobalt hydroxide contains β-type.

[0076] TEM analysis was performed on the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared in Example 1, as follows: Figure 2 As shown, according to Figure 2 As shown in Figures a and b, the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode exhibits a sheet-like nanostructure, with a small amount of Cu₂(OH)₃Cl particles ranging in size from 5 to 200 nm supported on the β-Co(OH)₂. This supported nanosheet electrocatalyst helps to expose more catalytic active sites and improves electrocatalytic performance.

[0077] X-ray photoelectron spectroscopy analysis was performed on the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared in Example 1, combined with... Figure 3 Figures a through c show that the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode contains Co, Cu, and O elements. In the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode, Cu mainly exists in the +2 oxidation state, while Co exists in the +2 and +3 oxidation states. This is mainly because the introduction of Cu₂(OH)₃Cl increases the oxidation state of some elements. In the O1s, M-OH and MO bonds were observed. The above test results prove the successful preparation of the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode.

[0078] The catalytic electrodes prepared in Examples 1, 2, Comparative Examples 1 and 2 were tested using linear sweep voltammetry. The electrolyte was a mixed solution of 0.1 M NaNO₂ and 1 M KOH. Figure 4 As shown; Figure a is the linear voltammetric scan of electrocatalytic nitrite reduction, and Figure b is a comparison of the Faradaic efficiency of ammonium products; according to Figure 4As shown in Figure a, the prepared β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode exhibits superior catalytic performance. Compared to the Co(OH)2 samples prepared in Comparative Examples 1 and 2, the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode demonstrates better current density and potential performance. Furthermore, at a potential of -0.2V vs. RHE, the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode can achieve an ammonium Faraday efficiency of 90.3%, proving that the introduction of Cu2(OH)3Cl can significantly improve the cathodic electrocatalytic performance of the Co(OH)2 catalyst.

[0079] The catalytic electrodes prepared in Examples 1, 2, and Comparative Examples 1 and 2 were tested using linear sweep voltammetry. The electrolyte was a mixed solution of 0.1 M glycerol and 1 M KOH. Figure 5 As shown in the figure; where Figure a is the linear voltammetric scan of electrocatalytic glycerol oxidation, and Figure b is a comparison of the Faradaic efficiency of formate products; compared with the Co(OH)2 samples prepared in Comparative Examples 1 to 2, the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode has better current density and potential performance. It can be seen that the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared in Example 1 of this invention has the best glycerol oxidation activity, and at a potential of 1.45V vs. RHE, the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode can achieve a formate Faradaic efficiency of 93.8%, proving that the introduction of Cu2(OH)3Cl can significantly improve the anodic electrocatalytic performance of Co(OH)2 catalyst.

[0080] The solutions of the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared in Example 1 of this invention before and after the electrocatalytic glycerol reaction were analyzed. 1 H NMR testing, the test results are as follows Figure 6 As shown, after a constant potential reaction for 1 hour, the glycerol... 1 The 1H NMR signal weakens, and a formic acid signal peak appears at 8.3 ppm, indicating that the β-Co(OH)2 / Cu2(OH)3Cl electrocatalyst prepared in Example 1 can effectively electrocatalyze the oxidation of glycerol to formate.

[0081] To evaluate the stability of the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode under long-term cycling tests, the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode prepared in Example 1 was subjected to NO₂RR chronocurrent curve testing using a three-electrode method in a mixed solution of 0.1M NaNO₂ and 1M KOH. Figure 7 As shown in figure a, the electrode is at -40 mA cm -2It can stably electrolyze for more than 24 hours at current density; such as Figure 7 As shown in b, the GOR chronoamperometry curve was measured using a three-electrode method in a mixed solution of 0.1M glycerol and 1M KOH. The electrode was at 20mA cm⁻¹. -2 The β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared by the method provided in this invention can be stably electrolyzed for more than 24 hours at the current density, which shows that it has excellent bifunctional catalytic activity and high cycle stability, demonstrating great market application prospects.

[0082] The performance of the β-Co(OH)₂ / Cu₂(OH)₃Cl catalytic electrode prepared in Example 1 was tested using a flowing membrane electrode assembly (MEA) method under the conditions of a mixed solution of 0.1 M NaNO₂ and 1 M KOH and a mixed solution of 0.1 M glycerol and 1 M KOH. Figure 8 As shown, compared to traditional water electrolysis cells, the electrolysis cell coupling nitrite reduction and glycerol oxidation operates at 50 mA cm⁻¹. -2 At the current density, the required voltage was significantly reduced by 300mV, indicating that the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode can serve as a bifunctional catalytic electrode for the oxidation of glycerol coupled with the reduction of nitrite to synthesize ammonia.

[0083] The electrolytic stability of the MEA prepared in Example 1 was further tested under the conditions of a mixed solution of 0.1 M NaNO2 and 1 M KOH and a mixed solution of 0.1 M glycerol and 1 M KOH. Figure 9 As shown, the assembled electrolytic cell can continuously electrolyze for more than 17 hours at a potential of 1.5V vs. RHE, and can maintain stable voltage and current density during continuous electrolysis, indicating that the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode of the present invention has excellent catalytic stability for the co-production of formate and ammonium salts.

[0084] GOR tests were performed on the catalytic electrodes prepared in Examples 1 to 6 and Comparative Examples 1 to 2 under different Co / Cu molar ratios, respectively. Figure 10 As shown in Figures a and b, a comparison reveals that the optimal Co / Cu molar ratio for the β-Co(OH)2 / Cu2(OH)3Cl catalytic electrode prepared in this invention is 10:1. The catalytic electrode with this ratio exhibits better GOR catalytic performance.

[0085] It can be known through the performance test that the bifunctional catalytic electrode, the preparation method and the application thereof have the following advantages. The catalytic electrode prepared by the synthesis method provided by the application has a sheet-shaped nano structure, has good crystallinity and stability, and has high activity and excellent stability in the reaction of electrocatalytic synthesis of ammonia and co-production of formate. In a wide potential window, the catalytic electrode can realize more than 90% of the ammonium and formate faradic efficiency, and shows good stability in the cycle test.

[0086] Although embodiments of the application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bifunctional catalytic electrode, characterized in that: The material includes carbon paper and a catalytic material supported on the surface of the carbon paper. The catalytic material includes cobalt hydroxide and a basic copper salt supported on the cobalt hydroxide. The cobalt hydroxide has a β-type crystal form, and the basic copper salt is selected from Cu2(OH)3Cl or Cu2(OH)3NO3. The molar ratio of the basic copper salt to cobalt hydroxide is 1:5 to 15, wherein the basic copper salt and cobalt hydroxide are expressed in molar amounts of copper and cobalt, respectively.

2. The bifunctional catalytic electrode according to claim 1, characterized in that: The catalytic material has a sheet-like nanostructure with a size of 50~200 nm.

3. The bifunctional catalytic electrode according to claim 1, characterized in that: The loading of the catalyst material on the carbon paper is 2~3 mg / cm³. 2 .

4. A method for preparing a bifunctional catalytic electrode according to any one of claims 1 to 3, characterized in that: Includes the following steps: Step 1: Mix cobalt salt, copper salt, hexamethylenetetramungsten, ethanol and water, and stir to obtain a mixed solution; Step 2: Reflux the mixed solution at 95°C to obtain a solid powder; Step 3: Disperse the solid powder in a mixed solution containing ethanol and naphthol, and ultrasonically treat it to obtain a catalyst slurry; Step 4: Spray the catalyst slurry onto carbon paper and allow it to dry naturally to obtain the bifunctional catalytic electrode.

5. The method for preparing a bifunctional catalytic electrode according to claim 4, characterized in that: In step 1, the cobalt salt is selected from cobalt chloride hexahydrate or cobalt nitrate hexahydrate; The copper salt is selected from copper chloride dihydrate or copper nitrate trihydrate.

6. The method for preparing a bifunctional catalytic electrode according to claim 4, characterized in that: In step 1, the molar ratio of the cobalt salt to the copper salt is 5~15:1; The molar ratio of the cobalt salt to the hexamethylenetetraammonium is 1:1~3; The mass ratio of the cobalt salt to the volume ratio of the ethanol is 1g:10~20mL; The mass ratio of the cobalt salt to the volume of the water is 1g:120~160mL.

7. The method for preparing a bifunctional catalytic electrode according to claim 4, characterized in that: In step 1, the stirring time is 15-30 minutes.

8. The method for preparing a bifunctional catalytic electrode according to claim 4, characterized in that: In step 2, the reflux process takes 1 to 1.5 hours.

9. The method for preparing a bifunctional catalytic electrode according to claim 4, characterized in that: In step 3, the volume ratio of the solid powder to ethanol is 1g:100~200mL; The volume ratio of ethanol to naphthol is 200:

7.

10. The application of a bifunctional catalytic electrode according to any one of claims 1 to 3 or a bifunctional catalytic electrode obtained by the preparation method according to any one of claims 4 to 9 in the electrosynthesis of ammonia and co-production of formate.

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