A self-supporting catalytic electrode with a heterostructure and a preparation method and application thereof

Abstract

The application provides a self-supporting catalytic electrode with a heterogeneous structure and a preparation method and application thereof. The self-supporting catalytic electrode comprises a carbon cloth and nanosheets vertically loaded on the surface of the carbon cloth, and the nanosheets are copper particle modified cobalt copper double hydroxide nanosheet arrays. The self-supporting catalytic electrode provided by the application forms copper particle modified cobalt copper double hydroxide (Cu@CoCu LDH / CC) with a nanosheet morphology on the surface of the carbon cloth. Based on the unique composition, morphology and electronic structure, the electrode can be used as an anode and cathode electrocatalyst to simultaneously realize efficient electrocatalytic reduction of nitrate to ammonia and electrocatalytic oxidation of polyethylene terephthalate (PET) hydrolysis liquid to formate, so that the value-added treatment of PET waste plastics and nitrate wastewater is realized.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a self-supporting catalytic electrode with a heterostructure, its preparation method, and its application. Background Technology

[0002] With rapid industrialization, energy crises and environmental pollution have become increasingly serious problems. Nitrates in industrial wastewater, as a significant nitrogen-containing pollutant, pose a serious threat to the ecological environment and human health. Traditional treatment methods are inefficient and costly. This paper proposes a sustainable electrocatalytic nitrate reduction reaction (NO3RR) technology to remove NO3... - Converting NH3 into ammonia is an effective strategy for turning waste into treasure and eliminating nitrate wastewater. However, the reaction kinetics of the cathode NO3RR and the anode oxygen evolution reaction (OER) are slow, and the multi-electron transfer process is complex, resulting in unsatisfactory energy efficiency of NH3 electrosynthesis. Therefore, it is essential to explore thermodynamically favorable small-molecule oxidation reactions as alternative half-reactions coupled with NO3RR.

[0003] Polyethylene terephthalate (PET), as a common waste plastic, is increasingly attracting attention for its treatment and recycling. Hydrolyzing PET plastic in a strongly alkaline solution is a feasible method to produce ethylene glycol (EG) containing PET hydrolysate, which can then be used for anodic electrocatalytic upgrading and recycling to produce value-added chemicals. Combining NO3RR with the PET-derived EG oxidation reaction (EGOR) to establish a simultaneous and synergistic upgrading and recycling system for waste pollutants is of great significance for the simultaneous energy-efficient production of high-value-added chemicals. However, the severe lack of highly active bifunctional electrodes is a key factor limiting the development of this coupled overall reaction technology.

[0004] Among various non-precious metal-based materials, copper (Cu) is valued for its low cost and high inherent reactivity (especially against NO3). - Co (Cu) has been proven to be an ideal candidate material for NO3RR catalysis of NH3 due to its moderate adsorption capacity, poor hydrogen evolution activity, and fast reduction kinetics. However, simple Cu catalysts are often severely deactivated by alkaline cathode corrosion. Therefore, a series of copper-based electrocatalysts have been developed through various control strategies, and significant progress has been made. Designing interfacial heterostructures is one effective approach. On the other hand, the good EGOR performance of Co-based materials has been gradually confirmed, and their high constitutive activity is due to the rapid formation of reconstructed high-valence active cobalt species. Therefore, constructing heterostructure materials with Co-Cu bimetallic active centers is expected to serve as highly active bifunctional electrocatalysts for co-electrolysis systems. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a self-supporting catalytic electrode with a heterostructure, its preparation method, and its application. By in-situ growing a layered cobalt-copper double hydroxide nanosheet array modified with copper particles on carbon cloth, a Cu@CoCu LDH / CC electrode with a heterostructure is obtained, which can simultaneously catalyze NO3. - The reaction that converts NH3 and PET into formic acid through hydrolysis solves the problems mentioned in the background art.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] According to a first aspect of the present invention, a self-supporting catalytic electrode with a heterostructure is provided, comprising carbon cloth and nanosheets vertically loaded on the surface of the carbon cloth, wherein the nanosheets are an array of cobalt copper double hydroxide nanosheets modified with copper particles.

[0010] Preferably, the length of the nanosheet is 20-300 nm and the width of the nanosheet is 20-500 nm.

[0011] Preferably, the nanosheet has a Cu(200) crystal plane with a stripe spacing of 0.181 nm and a CoCu LDH(009) crystal plane with a stripe spacing of 0.256 nm, wherein there is a heterogeneous interface between the Cu(200) crystal plane and the CoCu LDH(009) crystal plane.

[0012] According to a second aspect of the present invention, a method for preparing a self-supporting catalytic electrode with a heterostructure is provided, comprising the following steps:

[0013] (1) Add soluble copper salt and soluble cobalt salt to water and mix evenly to obtain a salt solution;

[0014] (2) Using carbon cloth as the working electrode, saturated silver / silver chloride electrode as the reference electrode, and platinum sheet electrode or graphite rod electrode as the counter electrode, the salt solution from step (1) is used as the electrolyte to construct an electrolytic cell with a three-electrode system. A constant current is applied to the working electrode to perform electrochemical deposition to obtain a pre-set electrode.

[0015] (3) The pre-placed electrode is ultrasonically cleaned alternately with ethanol and distilled water, and then vacuum dried to obtain the self-supporting catalytic electrode with heterostructure.

[0016] Preferably, in step (1), the molar ratio of the soluble copper salt to the soluble cobalt salt is 1:1 to 5.

[0017] Preferably, in step (1), the soluble copper salt is selected from at least one of copper nitrate, copper chloride, and copper sulfate;

[0018] The soluble cobalt salt is selected from at least one of cobalt nitrate, cobalt chloride, and cobalt sulfate.

[0019] Preferably, in step (2), during the electrochemical deposition process, the applied constant current density is -40 to -120 mA cm⁻¹. -2 The constant current is applied for 300–600 seconds.

[0020] Preferably, in step (3), the pre-placed electrode is ultrasonically cleaned alternately with ethanol and distilled water ≥ 3 times;

[0021] The vacuum drying temperature is 60–80°C, and the vacuum drying time is 30–60 min.

[0022] According to a third aspect of the present invention, a self-supporting catalytic electrode with a heterostructure is provided for use in the simultaneous electrocatalytic reduction of nitrate to ammonia and the oxidation of polyethylene terephthalate hydrolysate to formate.

[0023] (III) Beneficial Effects

[0024] This invention provides a self-supporting catalytic electrode with a heterostructure, its preparation method, and its application. It offers the following advantages:

[0025] (1) The proposed solution provides a self-supporting catalytic electrode with a heterostructure, which forms a cobalt-copper double hydroxide modified with copper particles of nanosheet morphology on the surface of carbon cloth. Based on its unique composition, electronic structure and conductivity, it can not only effectively accelerate the deoxygenation and hydrogenation in the nitrate reduction process and reduce the energy barrier in the reaction process, but also has excellent catalytic activity and selectivity for nitrate transammoniation. In addition, in the simultaneous reaction of PET hydrolysate oxidation to formate, its good C-C bond cleavage kinetics promotes hydrogenation to generate products and reduces the reaction energy barrier, thus exhibiting excellent catalytic activity and selectivity for PET hydrolysate oxidation to formic acid.

[0026] (2) The method provided in this scheme is a preparation method of a self-supporting catalytic electrode with a heterostructure. The preparation method is quick and easy, and the operation is simple. It can be mass-produced with common and inexpensive chemical raw materials through a simple three-electrode deposition synthesis equipment. The product is easy to collect. In addition, the substrate material carbon cloth is easy to replace and can be used to synthesize self-supporting catalytic electrodes of different shapes and sizes, which has better practicality.

[0027] (3) The self-supporting catalytic electrode with a heterostructure provided in this scheme can be rapidly assembled into an electrode device without the need for any conductive materials or auxiliary binders. In the process of catalytic reduction of nitrate to ammonia, the catalyst achieves an ammonia faradaic efficiency of 96.0% and an ammonia yield of 0.394 mmol / h at a potential of -0.3 V vs RHE. -1 cm -2 Meanwhile, in the catalytic oxidation of polyethylene terephthalate (PET) hydrolysate to formate, the formate Faradaic efficiency reached 93.0% at a potential of 1.3 V vs RHE, and the formate yield reached 0.223 mmol / L. -1 cm -2 .

[0028] (4) The application of a self-supporting catalytic electrode with a heterostructure provided in this scheme in the simultaneous electrocatalytic reduction of nitrate to ammonia and oxidation of polyethylene terephthalate hydrolysate to formate, still maintains high electrocatalytic activity and stability after long-term catalysis. Attached Figure Description

[0029] Figure 1 This is a process flow diagram for preparing a self-supporting catalytic electrode with a heterostructure according to the present invention.

[0030] Figure 2 The X-ray diffraction pattern of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention;

[0031] Figure 3 X-ray diffraction patterns of the catalytic electrodes prepared in Comparative Examples 1 to 3 of this invention;

[0032] Figure 4 The images shown are scanning electron microscope (SEM) images of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention. Image a is a SEM image at 5 μm, image b is a SEM image at 1 μm, and image c is a SEM image at 500 nm.

[0033] Figure 5 The images shown are scanning electron microscope (SEM) images of the catalytic electrodes prepared in Comparative Examples 1 and 2 of this invention. In the images, a is the SEM image of Co(OH)2 / CC at 5 μm, b is the SEM image of Co(OH)2 / CC at 1 μm, c is the SEM image of Co(OH)2 / CC at 500 nm, d is the SEM image of Cu2O / CC at 5 μm, e is the SEM image of Cu2O / CC at 1 μm, and f is the SEM image of Cu2O / CC at 500 nm.

[0034] Figure 6 The images shown are transmission electron microscope (TEM) images of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention. Image a is a TEM image at 20 nm, image b is a high-resolution TEM image at 5 nm, and image c is an elemental mapping image.

[0035] Figure 7 The XPS spectra of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention are shown in Figure a, where Figure a is the XPS spectra of Co 2p, Figure b is the XPS spectra of Cu 2p, and Figure c is the XPS spectra of O1s.

[0036] Figure 8 Linear voltammetric curves were obtained by testing the performance of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Examples 1 to 3 of the present invention and the catalytic electrode prepared in Comparative Examples 1 to 3 in a mixed solution containing 0.1M KNO3 and 1M KOH to measure the nitrate reduction reaction (NO3RR).

[0037] Figure 9 The ammonia Faradaic efficiency and ammonia yield of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention at different reaction potentials;

[0038] Figure 10 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention was subjected to a three-electrode method at -100 mA cm⁻¹. -2 The chronovoltage curve of NO3 after electrolysis for 50 hours at a constant current density;

[0039] Figure 11 Linear voltammetric curves of the oxidation reaction (EGOR) of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention and the catalytic electrodes prepared in Comparative Examples 1 to 3 were tested in PET hydrolysate.

[0040] Figure 12 The formic acid Faradaic efficiency and yield at different reaction potentials were obtained by EGOR synthesis of formic acid using the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention.

[0041] Figure 13 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of this invention was subjected to a three-electrode method at -100 mA cm⁻¹. -2 Timing voltage curve of EGOR after 50 hours of electrolysis at constant current density;

[0042] Figure 14This invention uses the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 as the cathode and anode. The two electrodes are constructed by separating the cathode electrolyte (0.1M KNO3 and 1M KOH) and the anode electrolyte (PET hydrolysate) with anion exchange membrane Fumasep FAA-3-PK-50. The comparison chart shows the anode formate faradaic efficiency, cathode ammonia faradaic efficiency, and yield under different test voltages. Detailed Implementation

[0043] To better illustrate the content of this invention, the following description is provided in conjunction with specific embodiments.

[0044] Example 1

[0045] This embodiment prepares a self-supporting catalytic electrode with a heterostructure, and the preparation process is as follows: Figure 1 As shown:

[0046] Step 1: Add 5 mmol of Co(NO3)2·6H2O and 1.25 mmol of Cu(NO3)2·3H2O to 50 ml of distilled water to prepare a light red electrolyte.

[0047] Step 2, select a 1×2cm piece 2 Carbon cloth was used as the working electrode, a saturated silver / silver chloride electrode as the reference electrode, and a platinum sheet electrode or a graphite rod electrode as the counter electrode. A -80 mA cm⁻¹ was applied to the working electrode. -2 With a constant current density, the dark green catalyst grows rapidly on the carbon cloth surface. After continuous application for 300 seconds, the dark green Cu@CoCu LDH / CC tightly and uniformly covers the carbon cloth surface, resulting in a pre-placed electrode.

[0048] Step 3: The prepared pre-placed electrode was ultrasonically cleaned three times with alternating ethanol and distilled water for 5 minutes each time to remove residues on the electrode surface. Then, it was placed in a vacuum oven and dried at 80°C for 30 minutes to obtain a self-supporting catalytic electrode with a heterostructure, named Cu2@CoCu LDH / CC. Subsequent performance studies confirmed that Cu2@CoCu LDH / CC was the optimal condition, which was simplified to Cu@CoCu LDH / CC without further specification.

[0049] Example 2

[0050] The preparation method in this embodiment is the same as that in Example 1, except that in step 2, the constant current density applied during electrodeposition is -40 mA cm⁻¹. -2 It is named Cu1@CoCu LDH / CC.

[0051] Example 3

[0052] The preparation method in this embodiment is the same as that in Example 1, except that in step 2, the constant current density applied during electrodeposition is -120 mA cm⁻¹. -2 It is named Cu3@CoCu LDH / CC.

[0053] Comparative Example 1

[0054] A method for preparing a cobalt hydroxide / carbon cloth (Co(OH)2 / CC) catalytic electrode synthesized by cobalt nitrate electrodeposition includes the following steps:

[0055] Step 1: Add 5 mmol of Co(NO3)2·6H2O to 50 mL of distilled water to prepare a light red electrolyte.

[0056] Step 2, place a 1×2cm piece 2 A carbon cloth electrode is used as the working electrode, a saturated silver / silver chloride electrode as the reference electrode, and a platinum sheet electrode or a graphite rod electrode as the counter electrode. A -80 mA cm⁻¹ is applied to the working electrode. -2 With a constant current density, a green catalyst rapidly grows on the surface of the carbon cloth. After continuous application for 300 seconds, the green Co(OH)2 catalyst tightly covers the surface of the carbon cloth, resulting in a pre-placed electrode.

[0057] Step 3: The prepared pre-electrode is ultrasonically cleaned alternately with ethanol and distilled water for 5 min, and repeated three times. Then it is taken out and placed in a vacuum oven to dry at 80℃ for 30 min to obtain a self-supporting Co(OH)2 / CC catalytic electrode.

[0058] Comparative Example 2

[0059] A method for preparing a cuprous oxide / carbon cloth (Cu2O / CC) catalytic electrode by copper nitrate electrodeposition:

[0060] Step 1: Add 1.25 mmol of Cu(NO3)2·3H2O to 50 mL of distilled water to prepare a light blue electrolyte.

[0061] Step 2, place a 1×2cm piece 2 A carbon cloth electrode is used as the working electrode, a saturated silver / silver chloride electrode as the reference electrode, and a platinum sheet electrode or a graphite rod electrode as the counter electrode. A -80 mA cm⁻¹ is applied to the working electrode. -2 With a constant current density, a sub-red catalyst will quickly appear on the surface of the carbon cloth. After a constant current is applied for 300 seconds, the sub-red Cu2O catalyst will tightly cover the surface of the carbon cloth, thus obtaining the pre-placed electrode.

[0062] Step 3: The prepared pre-electrode is ultrasonically cleaned alternately with ethanol and distilled water for 5 min, and repeated three times. Then it is taken out and placed in a vacuum oven to dry at 80℃ for 30 min to obtain a self-supporting Cu2O / CC catalytic electrode.

[0063] Comparative Example 3

[0064] A method for preparing a cobalt copper hydroxide / carbon cloth (CoCu LDH / CC) catalytic electrode using a hydrothermal method and a spray coating method:

[0065] Step 1: Add 5 mmol of Co(NO3)2·6H2O and 1.25 mmol of Cu(NO3)2·3H2O to 50 mL of distilled water to prepare a light red solution A; add 2.5 mmol of Na2CO3 and 10 mmol of NaOH to 50 mL of distilled water and mix well to obtain solution B.

[0066] Step 2: Gradually add solution B to solution A until the pH value of the solution reaches 10. Stir the mixed solution at 90°C for 8 hours. Centrifuge the obtained powder and then dry it overnight in a vacuum oven at 60°C to obtain CoCu LDH powder.

[0067] Step 3: Mix 5 mg of CoCu LDH powder with 40 μL of Nafion solution in 1 mL of ethanol solution until homogeneous, and then spray the solution evenly onto carbon cloth to obtain a self-supporting CoCu LDH / CC catalytic electrode.

[0068] Performance testing

[0069] XRD analysis was performed on the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1, as follows: Figure 2 As shown, the XRD results of the prepared Cu@CoCu LDH / CC self-supporting catalytic electrode are consistent with those of the standard CoCu LDH structure. The remaining diffraction peaks correspond one-to-one with the characteristic peaks of Cu elemental (JCPDS 04-0836), indicating that the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in this embodiment is a cobalt copper double hydroxide nanosheet modified with copper particles.

[0070] Combination Figure 3 As shown in Figures a to c, the catalytic electrodes prepared in Comparative Examples 1 to 3 are not copper particle-modified cobalt copper double hydroxide nanosheets.

[0071] SEM analysis was performed on Example 1, Comparative Example 1, and Comparative Example 2, combined with... Figure 4 and Figure 5As can be seen from the comparison, the CoCu-based double hydroxide material modified by copper nanoparticles electrodeposited by the bimetallic source in Example 1 has a uniform and tightly packed nanosheet morphology, and the abundant nanosheets grow uniformly on the surface of the carbon cloth substrate, which is conducive to sufficient contact with the substrate during the reaction process, thereby exposing more catalytic active sites and promoting the occurrence of catalytic reaction.

[0072] Example 1 involved TEM and elemental composition analysis, combined with Figure 6 As can be seen, the transmission electron microscopy (TEM) images further reveal the nanosheet structure. In the high-resolution TEM images, lattice fringes with interplanar spacings of 0.181 nm and 0.256 nm can be observed, corresponding to the crystal planes of Cu(200) and CoCu LDH(009), respectively. Simultaneously, the energy dispersive spectroscopy (EDS) spectrum of Cu@CoCu LDH shows that Co, Cu, and O elements are uniformly distributed throughout the heterogeneous nanosheet.

[0073] X-ray photoelectron spectroscopy was performed on the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1. Figure 7 As shown in Figure a, the XPS spectrum data of Co 2p is displayed. Two peaks can be observed in Figure a, located at 797.14 eV and 781.08 eV respectively. These peaks correspond to Co... 2+ Co 2p 1 / 2 and Co 2p 3 / 2 Meanwhile, the peaks at 802.6 eV and 786.5 eV in the Co 2p spectrum are its corresponding satellite peaks. Figure b shows the XPS spectrum data for Cu 2p, with the peaks at 954.3 eV and 934.2 eV attributed to Cu. 2+ Cu 2p 1 / 2 and Cu 2p 3 / 2 The peaks at 762.1 eV and 741.9 eV correspond to satellite peaks. Figure c shows the XPS spectrum data for O1s, with the peak at 531.3 eV indicating the presence of hydroxyl oxygen. The binding energy between the metal and oxygen was observed at 530.6 eV, and a signal due to hydroxyl (-OH) was found at 532.5 eV, which may originate from surface-adsorbed water molecules.

[0074] Application Example 1

[0075] Using the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 as the cathode and anode, a two-electrode test system was constructed by separating the cathode electrolyte (0.1M KNO3 and 1M KOH) and the anode electrolyte (PET hydrolysate) with an anion exchange membrane (Fumasep FAA-3-PK-50). After electrolysis for 2 hours with a voltage of 1.2V applied, the cathode and anode electrolytes were collected for product (ammonia and formate) detection.

[0076] Application Example 2

[0077] This application example uses the same method as Application Example 1, except that the applied potential is 1.3V.

[0078] Application Example 3

[0079] This application example uses the same method as Application Example 1, except that the applied potential is 1.4V.

[0080] Application Example 4

[0081] This application example uses the same method as Application Example 1, except that the applied potential is 1.5V.

[0082] Application Example 5

[0083] This application example uses the same method as Application Example 1, except that the applied potential is 1.6V.

[0084] Performance testing

[0085] Examples 1 to 3, and Comparative Examples 1 to 3, show the NO3RR linear voltammetric curves obtained by the three-electrode method for the catalytic electrodes prepared in 1 M KOH solution containing 0.1 M KNO3, as shown below. Figure 8 As shown, the Cu@CoCu LDH / CC self-supporting catalytic electrode exhibits excellent nitrate reduction catalytic performance, reaching -100 mA cm⁻¹ at a potential of -234 mV. -2 The current density indicates that the catalytic electrode is significantly superior to the catalytic electrodes prepared in Examples 2 and 3, and Comparative Examples 1 to 3.

[0086] The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was tested using a three-electrode method in a 1M KOH solution containing 0.1M KNO3 to determine the ammonia Faradaic efficiency and electro-ammonia yield at different reaction potentials. Figure 9 As shown, at a potential of -0.3V, the ammonia faradaic efficiency can reach 96.0%, and the yield reaches 0.394 mmol / L. -1 cm -2 It has better application potential.

[0087] according to Figure 10 As shown, the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was used in a 1M KOH solution containing 0.1M KNO3 via a three-electrode method at -100mA cm⁻¹. -2 The chronovolt-response (CR) curve of NO3 after 50 hours of electrolysis at a constant current density is shown. This test mainly evaluates the long-term stability of the Cu@CoCu LDH / CC self-supporting catalytic electrode. The results demonstrate that the self-supporting electrode prepared in this invention has good stability and can be applied to actual industrial production.

[0088] Figure 11 Linear voltammetric curves of the oxidation reaction (EGOR) of the catalytic electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were obtained by using the three-electrode method in PET hydrolysate. Figure 11 As shown, the Cu@CoCu LDH / CC self-supporting catalytic electrode exhibits excellent catalytic performance for ethylene glycol oxidation, achieving a 50 mA cm⁻¹ at a potential of 1.25 V. -2 The current density demonstrates that the catalytic electrode prepared in this invention has significantly better catalytic performance than other catalytic electrodes.

[0089] Figure 12 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was used to test the formate Faradaic efficiency and yield at different reaction potentials in PET hydrolysate using a three-electrode method. The results showed that at a potential of 1.3 V, a formate Faradaic efficiency of 93.0% and a yield of 0.223 mmol / L were achieved. -1 cm -2 The formate yield has good potential for industrial applications.

[0090] Figure 13 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was used in PET hydrolysate with a three-electrode configuration at 100 mA cm⁻¹. -2 The chronovolt-chronometry curves obtained by electrolysis at a constant current density for 50 hours show that the Cu@CoCu LDH / CC self-supporting catalytic electrode provided by this invention has good catalytic stability.

[0091] Figure 14 The performance of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 as both cathode and anode was studied in a two-electrode setup. The cathode electrolyte (0.1 M KNO3 and 1 M KOH) and the anode electrolyte (PET hydrolysate) were separated by an anion exchange membrane, Fumasep FAA-3-PK-50. After electrolysis at different voltages for 2 hours, the cathode and anode electrolytes were collected for product (ammonia and formate) analysis. The results showed that at 1.3 V, a formate faradaic efficiency of 98.1% and an ammonia faradaic efficiency of 98.6% were achieved at the anode, providing an excellent electrode system for the co-electrochemical synthesis of value-added chemicals from the upgraded recycling of nitrate wastewater and waste plastics.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A self-supporting catalytic electrode with a heterostructure, characterized in that: It includes carbon cloth and nanosheets vertically loaded on the surface of the carbon cloth, wherein the nanosheets are an array of cobalt copper double hydroxide nanosheets modified with copper particles; The nanosheet has a Cu (200) crystal plane with a stripe spacing of 0.181 nm and a CoCu LDH (009) crystal plane with a stripe spacing of 0.256 nm, wherein there is a heterogeneous interface between the Cu (200) crystal plane and the CoCu LDH (009) crystal plane.

2. The self-supporting catalytic electrode with a heterostructure according to claim 1, characterized in that: The length of the nanosheet is 20~300nm, and the width of the nanosheet is 20~500nm.

3. A method for preparing a self-supporting catalytic electrode with a heterostructure as described in any one of claims 1 to 2, characterized in that: Includes the following steps: (1) Add soluble copper salt and soluble cobalt salt to water and mix evenly to obtain a salt solution; (2) Using carbon cloth as the working electrode, saturated silver / silver chloride electrode as the reference electrode, and platinum sheet electrode or graphite rod electrode as the counter electrode, the salt solution from step (1) is used as the electrolyte to construct an electrolytic cell with a three-electrode system. A constant current is applied to the working electrode to perform electrochemical deposition to obtain a pre-set electrode. (3) The pre-placed electrode is ultrasonically cleaned alternately with ethanol and distilled water, and then vacuum dried to obtain the self-supporting catalytic electrode with heterostructure.

4. The method for preparing a self-supporting catalytic electrode with a heterostructure according to claim 3, characterized in that: In step (1), the molar ratio of the soluble copper salt to the soluble cobalt salt is 1:1~5.

5. The method for preparing a self-supporting catalytic electrode with a heterostructure according to claim 3, characterized in that: In step (1), the soluble copper salt is selected from at least one of copper nitrate, copper chloride, and copper sulfate; The soluble cobalt salt is selected from at least one of cobalt nitrate, cobalt chloride, and cobalt sulfate.

6. The method for preparing a self-supporting catalytic electrode with a heterostructure according to claim 3, characterized in that: In step (2), during the electrochemical deposition process, a constant current density of -40 to -120 mA cm⁻¹ is applied. -2 The constant current is applied for 300~600 s.

7. The method for preparing a self-supporting catalytic electrode with a heterostructure according to claim 3, characterized in that: In step (3), the pre-placed electrode is ultrasonically cleaned alternately with ethanol and distilled water ≥ 3 times.

8. The method for preparing a self-supporting catalytic electrode with a heterostructure according to claim 3, characterized in that: The vacuum drying temperature is 60~80 ℃, and the vacuum drying time is 30~60 min.

9. The application of a self-supporting catalytic electrode with a heterostructure as described in any one of claims 1 to 2, or a self-supporting catalytic electrode with a heterostructure obtained by the preparation method according to any one of claims 3 to 8, in the simultaneous electrocatalytic reduction of nitrate to ammonia and oxidation of polyethylene terephthalate hydrolysate to formate.

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