Self-supporting catalytic electrode with heterostructure as well as preparation method and application of self-supporting catalytic electrode

Abstract

The invention provides a self-supporting catalytic electrode with a heterostructure as well as a preparation method and application of the self-supporting catalytic electrode. The self-supporting catalytic electrode comprises carbon cloth and nanosheets vertically loaded on the surface of the carbon cloth, and the nanosheets are cobalt-copper double hydroxide nanosheet arrays modified by copper particles. According to the self-supporting catalytic electrode provided by the invention, cobalt-copper double hydroxides (Cu-coated CoCu LDH / CC) modified by copper particles and having nanosheet morphology are formed on the surface of carbon cloth. Based on the unique composition, morphology and electronic structure, the electrode can serve as a cathode electrocatalyst and an anode electrocatalyst at the same time to be used for efficient electrocatalytic reduction of nitrate into ammonia and electrocatalytic oxidation of polyethylene glycol terephthalate (PET) hydrolysate into formate, and value-added treatment of PET waste plastics and nitrate wastewater is achieved.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalysis technology, and in particular to a self-supporting catalytic electrode with a heterogeneous structure, and a preparation method and application thereof. Background Art

[0002] With the rapid development of industrialization, energy crisis and environmental pollution are becoming increasingly serious. Nitrate in industrial wastewater, as an important nitrogen-containing pollutant, poses a serious threat to the ecological environment and human health. Traditional treatment methods are inefficient and costly. The sustainable electrocatalytic nitric acid reduction reaction (NO3RR) technology can be used to reduce NO3 - Conversion into value-added ammonia (NH3) is an effective strategy to achieve “waste-to-treasure” and eliminate nitrate wastewater. However, the sluggish reaction kinetics of the cathode NO3RR and the anode oxygen evolution reaction (OER) and the complex multi-electron transfer process lead to unsatisfactory energy efficiency of NH3 electrosynthesis. Therefore, it is very necessary to explore thermodynamically favorable small molecule oxidation reactions as alternative half-reactions coupled with NO3RR.

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

[0004] Among various non-precious metal-based materials, copper (Cu) is the most popular due to its low cost and high intrinsic activity (towards NO3 - Co-based electrocatalysts have been shown to be ideal candidates for catalyzing NH3 in NO3RR due to their moderate adsorption capacity, poor hydrogen evolution activity, and fast reduction kinetics. However, simple Cu catalysts are usually severely deactivated by cathode alkaline corrosion. Therefore, a series of copper-based electrocatalysts have been developed through various regulatory strategies, and significant progress has been made. Designing interfacial heterostructures is one of the effective approaches. On the other hand, it has been gradually confirmed that Co-based materials have good EGOR performance, and their high constitutive activity is due to the rapid formation of reconstructed high-valent active cobalt active species. Therefore, constructing heterostructure materials with Co-Cu bimetallic active centers is expected to be used as highly active bifunctional electrocatalysts for co-electrolysis systems. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the shortcomings of the prior art, the present invention provides a self-supporting catalytic electrode with a heterogeneous structure and a preparation method and application thereof. By in-situ growing a layered cobalt-copper double hydroxide nanosheet array modified with copper particles on a carbon cloth, a Cu@CoCu LDH / CC with a heterogeneous structure is obtained, which can simultaneously catalyze NO3 - The reaction of converting into NH3 and hydrolyzing PET to generate formic acid solves the problems raised in the above-mentioned background technology.

[0007] (II) Technical solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions:

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

[0010] Preferably, the length of the nanosheet is 20 to 300 nm, and the width of the nanosheet is 20 to 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 a heterogeneous interface exists between the Cu(200) crystal plane and the CoCu LDH(009) crystal plane.

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

[0013] (1) adding a soluble copper salt and a soluble cobalt salt into water and mixing them uniformly to obtain a salt solution;

[0014] (2) using carbon cloth as a working electrode, a saturated silver / silver chloride electrode as a reference electrode, a platinum sheet electrode or a graphite rod electrode as a counter electrode, and the salt solution of step (1) as an electrolyte to construct an electrolytic cell of a three-electrode system, applying a constant current to the working electrode for electrochemical deposition, and obtaining a preset electrode;

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

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

[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 constant current density applied is -40 to -120 mA cm -2 The constant current is applied for 300 to 600 seconds.

[0020] Preferably, in step (3), the preset electrode is ultrasonically cleaned alternately with ethanol and distilled water for ≥ 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, there is provided a self-supporting catalytic electrode with a heterogeneous structure for use in simultaneous electrocatalytic reduction of nitrate to produce ammonia and oxidation of polyethylene terephthalate hydrolyzate to produce formate.

[0023] (III) Beneficial effects

[0024] The present invention provides a self-supporting catalytic electrode with a heterogeneous structure and a preparation method and application thereof. It has the following beneficial effects:

[0025] (1) The present invention provides a self-supporting catalytic electrode with a heterogeneous structure, in which a copper particle-modified cobalt-copper double hydroxide with a nanosheet morphology is formed on the surface of a carbon cloth. Due to its unique composition, electronic structure and conductivity, it can not only effectively accelerate the deoxygenation and hydrogenation in the process of nitrate reduction, reduce the energy barrier in the reaction process, and have excellent nitrate transamination catalytic activity and selectivity, but also, in the simultaneous reaction of PET hydrolyzate oxidation to formate, its good CC bond cleavage kinetics promotes hydrogenation to generate products, reduces the reaction energy barrier, and has excellent catalytic activity and selectivity for PET hydrolyzate oxidation to formic acid.

[0026] (2) This scheme provides a method for preparing a self-supporting catalytic electrode with a heterogeneous structure. The preparation method is quick and simple, and the operation is simple. It can be mass-produced with common and cheap chemical raw materials through a simple three-electrode deposition synthesis equipment, and the product is very easy to collect. In addition, the base material carbon cloth used is easy to replace and use, and self-supporting catalytic electrodes of different shapes and sizes can be synthesized, which has better practicality.

[0027] (3) The present invention provides a self-supporting catalytic electrode with a heterogeneous structure for use in the simultaneous electrocatalytic reduction of nitrate to produce ammonia and oxidation of polyethylene terephthalate hydrolyzate to produce formate. The electrode device can be quickly assembled without any conductive material or auxiliary bonding material. In the process of catalytic reduction of nitrate to produce ammonia, the catalyst has an ammonia Faraday efficiency of 96.0% at a potential of -0.3 V vs RHE, and an ammonia yield of 0.394 mmol h -1 cm -2 At the same time, in the process of catalyzing the oxidation of polyethylene terephthalate hydrolyzate to formate, the Faraday efficiency of formic acid reached 93.0% at a potential of 1.3 V vs RHE, and the yield of formic acid reached 0.223 mmol h -1 cm -2 .

[0028] (4) The present invention provides a self-supporting catalytic electrode with a heterogeneous structure for use in the simultaneous electrocatalytic reduction of nitrate to produce ammonia and oxidation of polyethylene terephthalate hydrolyzate to produce formate. After a long period of catalysis, the electrode still maintains high electrocatalytic activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A process flow chart for preparing a self-supporting catalytic electrode with a heterogeneous structure according to the present invention;

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

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

[0032] Figure 4 This is a scanning electron microscope image of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention, wherein Figure a is a SEM image at 5 μm, Figure b is a SEM image at 1 μm, and Figure c is a SEM image at 500 nm;

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

[0034] Figure 6 The transmission electron microscope images of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention, wherein Figure a is a TEM image at 20 nm, Figure b is a high-resolution TEM image at 5 nm, and Figure c is an element mapping image;

[0035] Figure 7 This is the XPS spectrum of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention, wherein Figure a is the XPS spectrum of Co 2p, Figure b is the XPS spectrum of Cu 2p, and Figure c is the XPS spectrum of O1s;

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

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

[0038] Fig.10 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention was prepared by a three-electrode method at -100 mA cm -2 NO3RR chronovoltage curve of 50h electrolysis at constant current density;

[0039] Fig.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 tested in PET hydrolyzate;

[0040] Fig.12 The Faradaic efficiency and yield of formic acid synthesized by the oxidation reaction (EGOR) of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention at different reaction potentials;

[0041] Fig.13 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention was prepared by a three-electrode method at -100 mA cm -2 EGOR timing voltage curve of electrolysis for 50h at a constant current density;

[0042] Fig.14The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 of the present invention is used as the cathode and anode. The cathode 0.1M KNO3 and 1M KOH electrolyte and the anode PET hydrolyzate are separated by an anion exchange membrane Fumasep FAA-3-PK-50 to construct a two-electrode test condition. The anode formate Faraday efficiency and the cathode ammonia Faraday efficiency and yield comparison diagram at different test voltages. DETAILED DESCRIPTION

[0043] In order to better illustrate the content of the present invention, a detailed description is given below in conjunction with specific embodiments.

[0044] Example 1

[0045] This embodiment prepares a self-supporting catalytic electrode with a heterogeneous structure. 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 into 50 ml of distilled water to prepare a light red electrolyte;

[0047] Step 2, select a 1×2cm 2 The carbon cloth was used as the working electrode, the saturated silver / silver chloride electrode was used as the reference electrode, and the platinum sheet electrode or graphite rod electrode was used as the counter electrode. -80 mA cm was applied to the working electrode. -2 At a constant current density of , the dark green catalyst grows rapidly on the surface of the carbon cloth. After 300 s of continuous application, the dark green Cu@CoCu LDH / CC tightly and evenly covers the surface of the carbon cloth to obtain a preset electrode.

[0048] Step 3, the prepared pre-prepared electrode was ultrasonically cleaned three times with ethanol and distilled water alternately for 5 min each time to remove the residue on the electrode surface, and then placed in a vacuum oven and dried at 80 ° C for 30 min to obtain a self-supporting catalytic electrode with a heterogeneous structure, 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 of this embodiment is the same as that of embodiment 1, except that in step 2, the constant current density applied during electrodeposition is -40 mA cm -2 , named Cu1@CoCu LDH / CC.

[0051] Example 3

[0052] The preparation method of this embodiment is the same as that of embodiment 1, except that in step 2, the constant current density applied during electrodeposition is -120 mA cm -2 , 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 comprises the following steps:

[0055] Step 1, add 5 mmol of Co(NO3)2·6H2O into 50 mL of distilled water to prepare a light red electrolyte;

[0056] Step 2: Place a 1×2cm 2 The carbon cloth was used as the working electrode, the saturated silver / silver chloride electrode was used as the reference electrode, and the platinum sheet electrode or graphite rod electrode was used as the counter electrode. -80 mA cm was applied to the working electrode. -2 At a constant current density of , the green catalyst quickly grew on the surface of the carbon cloth. After 300 seconds of continuous application, the green Co(OH)2 catalyst tightly covered the surface of the carbon cloth to obtain a preset electrode.

[0057] Step 3, the prepared pre-set electrode was ultrasonically cleaned alternately with ethanol and distilled water for 5 minutes, and after repeating three times, it was taken out and placed in a vacuum oven and dried at 80° C. for 30 minutes 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 synthesized by copper nitrate electrodeposition:

[0060] Step 1, add 1.25 mmol of Cu(NO3)2·3H2O into 50 mL of distilled water to prepare a light blue electrolyte;

[0061] Step 2: Place a 1×2cm 2 The carbon cloth was used as the working electrode, the saturated silver / silver chloride electrode was used as the reference electrode, and the platinum sheet electrode or graphite rod electrode was used as the counter electrode. -80 mA cm was applied to the working electrode. -2 At a constant current density of , a sub-red catalyst will quickly appear on the surface of the carbon cloth. After applying the constant current for 300 seconds, the sub-red Cu2O catalyst will tightly cover the surface of the carbon cloth to obtain a preset electrode.

[0062] Step 3, the prepared pre-set electrode was ultrasonically cleaned alternately with ethanol and distilled water for 5 minutes, and after repeating three times, it was taken out and placed in a vacuum oven and dried at 80° C. for 30 minutes 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 prepared by a hydrothermal method and a spraying 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 a solution B;

[0066] Step 2, gradually adding solution B to solution A until the pH value of the solution reaches 10, stirring the mixed solution at 90° C. for 8 h, centrifuging the obtained powder, and then drying it in a vacuum oven at 60° C. overnight to obtain CoCu LDH powder;

[0067] Step 3, 5 mg of CoCu LDH powder and 40 μL of Nafion solution were mixed evenly in 1 mL of ethanol solution, and then the solution was evenly sprayed on the carbon cloth to obtain a self-supporting CoCu LDH / CC catalytic electrode.

[0068] Performance Testing

[0069] The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was subjected to XRD analysis. Figure 2 As shown, the prepared Cu@CoCu LDH / CC self-supporting catalytic electrode is consistent with the XRD card results of the standard CoCu LDH structure fitting, and the remaining diffraction peaks correspond one to one with the characteristic peaks of Cu element (JCPDS 04-0836), indicating that the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in this example 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 cobalt-copper double hydroxide nanosheets modified with copper particles.

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

[0072] Example 1 TEM and elemental composition analysis were performed, combined with Figure 6 It can be seen that the transmission electron microscope image further shows the structure of the nanosheet. In the high-resolution transmission image, lattice fringes with a surface spacing of 0.181nm and 0.256nm can be observed, corresponding to the crystal planes of Cu(200) and CoCu LDH(009), respectively. At the same time, the energy spectrum of Cu@CoCu LDH shows that Co, Cu and O elements are evenly distributed throughout the heterogeneous nanosheet.

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

[0074] Application Example 1

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

[0076] Application Example 2

[0077] The method of this application example is the same as that of application example 1, except that the potential applied in the step is 1.3V.

[0078] Application Example 3

[0079] The method of this application example is the same as that of application example 1, except that the potential applied in the step is 1.4V.

[0080] Application Example 4

[0081] The method of this application example is the same as that of application example 1, except that the potential applied in the step is 1.5V.

[0082] Application Example 5

[0083] The method of this application example is the same as that of application example 1, except that the potential applied in the step is 1.6V.

[0084] Performance Testing

[0085] The NO3RR linear voltammetric curves of the catalytic electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured by the three-electrode method in a 1M KOH solution containing 0.1M KNO3. Figure 8 The Cu@CoCu LDH / CC self-supporting catalytic electrode has excellent nitrate reduction catalytic performance, which reaches -100 mA cm at a potential of -234 mV. -2 The current density shows that the catalytic electrode is significantly better than 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 for ammonia Faraday efficiency and electroammonia yield at different reaction potentials using a three-electrode method in a 1M KOH solution containing 0.1M KNO3. Fig. 9 As shown in Figure 2, at a potential of -0.3 V, the ammonia Faraday efficiency can reach 96.0% and the yield can reach 0.394 mmol h -1 cm -2 , with better application potential.

[0087] according to Fig.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 using a three-electrode method at -100mA cm -2 The NO3RR chronovoltage curve of 50h electrolysis at a constant current density. This test mainly evaluates the stability of the Cu@CoCu LDH / CC self-supporting catalytic electrode over a long period of time. The results show that the self-supporting electrode prepared by the present invention has good stability and can be applied to actual industrial production.

[0088] Fig.11 The 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 tested in PET hydrolyzate using the three-electrode method. Fig.11 As shown in Figure 2, the Cu@CoCu LDH / CC self-supporting catalytic electrode exhibits excellent catalytic performance for ethylene glycol oxidation, which reaches 50 mA cm at a potential of 1.25 V. -2 The current density of 2.5 Å proves that the catalytic electrode prepared by the present invention has a catalytic performance that is significantly better than other catalytic electrodes.

[0089] Fig.12 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was used to test the formate Faraday efficiency and yield at different reaction potentials in PET hydrolyzate using a three-electrode method. The results showed that at a potential of 1.3 V, a formic acid Faraday efficiency of 93.0% and a yield of 0.223 mmol h-1 were achieved. -1 cm -2 The formate yield is high and has good industrial application potential.

[0090] Fig.13 The Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was used in PET hydrolyzate using three electrodes at 100 mA cm -2 The chronovoltage curve of electrolysis for 50 h at a constant current density is shown in FIG. 1 . The results show that the Cu@CoCu LDH / CC self-supporting catalytic electrode provided by the present invention has good catalytic stability.

[0091] Fig.14 The performance of the Cu@CoCu LDH / CC self-supporting catalytic electrode prepared in Example 1 was studied as the cathode and anode in a two-electrode device. Among them, the cathode 0.1M KNO3 and 1M KOH electrolyte and the anode PET hydrolyzate were separated by an anion exchange membrane Fumasep FAA-3-PK-50. Subsequently, after applying different voltages to the system for continuous electrolysis for 2 hours, the cathode and anode electrolytes were collected for product (ammonia and formate) detection. The results show that at a potential of 1.3V, a formate Faraday efficiency of 98.1% at the anode and an ammonia Faraday efficiency of 98.6% at the cathode can be achieved, providing an excellent electrode system for the development of co-electrosynthesis of value-added chemicals from the upgrading and recycling of nitrate wastewater and waste plastics.

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

Claims

1. A self-supporting catalytic electrode with a heterogeneous structure, Features: The invention comprises a carbon cloth and a nanosheet vertically loaded on the surface of the carbon cloth, wherein the nanosheet is a cobalt-copper double hydroxide nanosheet array modified by copper particles.

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

3. A self-supporting catalytic electrode with a heterogeneous structure according to claim 1, Features: 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 a heterogeneous interface exists between the Cu(200) crystal plane and the CoCu LDH(009) crystal plane.

4. A method for preparing a self-supporting catalytic electrode with a heterogeneous structure according to any one of claims 1 to 3, Features: The following steps are involved: (1) adding a soluble copper salt and a soluble cobalt salt into water and mixing them uniformly to obtain a salt solution; (2) using carbon cloth as a working electrode, a saturated silver / silver chloride electrode as a reference electrode, a platinum sheet electrode or a graphite rod electrode as a counter electrode, and the salt solution of step (1) as an electrolyte to construct an electrolytic cell of a three-electrode system, applying a constant current to the working electrode for electrochemical deposition, and obtaining a preset electrode; (3) The pre-set electrode is ultrasonically cleaned alternately with ethanol and distilled water, and vacuum dried to obtain the self-supporting catalytic electrode with a heterogeneous structure.

5. A method for preparing a self-supporting catalytic electrode with a heterogeneous structure according to claim 4, Features: In step (1), the molar ratio of the soluble copper salt to the soluble cobalt salt is 1:1-5.

6. A method for preparing a self-supporting catalytic electrode with a heterogeneous structure according to claim 4, Features: 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.

7. A method for preparing a self-supporting catalytic electrode with a heterogeneous structure according to claim 4, Features: In step (2), during the electrochemical deposition, the constant current density applied is -40 to -120 mA cm -2 The constant current is applied for 300 to 600 seconds.

8. The method for preparing a self-supporting catalytic electrode with a heterogeneous structure according to claim 4, Features: In step (3), the preset electrode is ultrasonically cleaned alternately with ethanol and distilled water for ≥ 3 times.

9. The method for preparing a self-supporting catalytic electrode with a heterogeneous structure according to claim 4, Features: The vacuum drying temperature is 60-80° C., and the vacuum drying time is 30-60 min.

10. Use of a self-supporting catalytic electrode with a heterogeneous structure as claimed in any one of claims 1 to 3 or a self-supporting catalytic electrode with a heterogeneous structure obtained by the preparation method according to any one of claims 4 to 9 in simultaneous electrocatalytic reduction of nitrate to produce ammonia and oxidation of polyethylene terephthalate hydrolyzate to produce formate.

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