Copper-doped cobalt-tetroxide electrode material, preparation method and application thereof

Abstract

This invention belongs to the field of new energy electroreduction of CO2 and NO3. ‑ This invention relates to the field of urea electrode material technology, and discloses a copper-doped cobalt tetroxide electrode material, its preparation method, and its applications. The method includes: S1, pretreatment of copper foam by sequentially immersing it in hydrochloric acid, acetone, ethanol, and water to obtain copper foam with a clean surface; S2, dispersing a cobalt source and organic ligand in a solvent and stirring to obtain a mixed solution; S3, reacting the pretreated copper foam and the mixed solution in a high-pressure reactor, cooling to room temperature, washing with deionized water, and vacuum drying to obtain the copper-doped cobalt tetroxide electrode material. Applications include the electrochemical co-reduction of CO2 and NO3. ‑ Applications in urea production.

Description

Technical Field

[0001] This invention relates to the electroreduction of CO2 and NO3 using new energy sources. - This invention relates to the field of coupling production of urea electrode materials, specifically to a copper-doped cobalt tetroxide electrode material, its preparation method, and its application. Background Technology

[0002] With the acceleration of global industrialization, the greenhouse effect caused by excessive CO2 emissions and NO3 in wastewater have become increasingly prominent. - Pollution-induced ecological imbalance has become a major challenge facing human society. However, traditional carbon capture and wastewater denitrification technologies often suffer from high energy consumption, low efficiency, and secondary pollution, necessitating the development of green and sustainable resource conversion pathways. In recent years, electrochemical catalysis technology has attracted considerable attention due to its unique advantage of converting waste molecules into high-value-added products under mild conditions. Among these, electrochemical coupling of CO2 reduction and NO3... - The direct synthesis of urea through reduction reactions not only provides an innovative approach to the synergistic management of carbon and nitrogen cycles, but also opens up a new green chemistry strategy of "turning waste into treasure".

[0003] Electrochemical co-reduction of CO2 and NO3 - Urea production is a complex gas-liquid-solid three-phase interfacial reaction. As the world's largest producer of nitrogen fertilizer and chemical raw materials, urea's traditional synthesis relies on the energy-intensive Haber-Bosch process and subsequent synthesis steps. However, an electrochemical in-situ coupling strategy promises to achieve low-energy, low-carbon urea production in a one-step process. Nevertheless, this process involves complex multi-proton-electron transfer and CN coupling mechanisms, thus placing extremely high demands on catalyst design, microenvironmental control at the reaction interface, and reaction pathway selectivity.

[0004] Previous research has shown that transition metals, with their abundant resources and low cost, are attractive catalysts for the conversion of CO2 and nitrates into urea (Ge R, Huo J, Lu P, et al. Multifunctional strategies of advanced electrocatalysts for efficient urea synthesis[J]. Advanced Materials, 2024, 36(49): 2412031.). Furthermore, for the standalone electrochemical CO2 reduction reaction and the electrochemical NO3... - In reduction reactions, Cu-based catalysts exhibit high reactivity in ECO2RR, converting CO2 to CO and possessing suitable adsorption energies for CO, which facilitates further reactions. Co-based catalysts, on the other hand, are widely used in electrochemical NO3 reduction. -In the reduction reaction, it is used to adsorb and activate NO3. - It is then converted into a key intermediate of *NH2. Previous studies have confirmed that cobalt-based and copper-based catalysts exhibit preliminary catalytic activity in urea electrosynthesis. However, existing systems still face the significant challenge of low urea selectivity. Therefore, how to controllably design transition metal oxides to achieve highly efficient catalytic activity is a problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention aims to provide a copper-doped cobalt tetroxide electrode material, its preparation method, and its applications. The copper-doped cobalt tetroxide electrode material, prepared in situ on copper foam using a simple and efficient method, is effective for the electrochemical co-reduction of CO2 and NO3. - Urea production exhibits excellent electrocatalytic activity and stability, thus addressing the aforementioned issues.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a copper-doped cobalt tetroxide electrode material, comprising the following steps: S1. Cut the copper foam into rectangular sheets and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand, and then remove it to remove the oxide layer on the surface of the copper foam. Then immerse it in acetone, ethanol, and water in sequence, and sonicate it to further remove impurities from the surface of the copper foam, so as to obtain copper foam with a clean surface. S2. Disperse the cobalt source and organic ligand sequentially in a solvent, and stir until fully dissolved to obtain a mixed solution; S3. Transfer the foamed copper obtained in step S1 and the mixed solution obtained in step S2 to a high-pressure reactor for reaction. After the reaction is completed, cool to room temperature, wash with deionized water, and then vacuum dry to obtain the desired copper-doped cobalt tetroxide electrode material.

[0007] Furthermore, in S1, the length * width * height of the copper foam slice is 3 cm × 2 cm × 0.3 cm.

[0008] Furthermore, in S1, the standing time in concentrated hydrochloric acid is 1 minute.

[0009] Furthermore, the ultrasound time is 15-30 minutes. Furthermore, in S2, the cobalt source is one of nitrate, halide, acetate, or acetylacetone salt.

[0010] Furthermore, in S2, the organic ligand is one of terephthalic acid, dimethylimidazole, or diaminoterephthalic acid.

[0011] Furthermore, in S2, the solvent is analytical grade ethanolamine, diethanolamine, triethanolamine, or N,N-diethanolamine diluted with deionized water. One of dimethylformamide, ethylenediamine, an alkaline soluble solvent, and an aqueous solution.

[0012] Furthermore, in S2, the molar ratio of the added cobalt source to the organic ligand is 1:0.1 to 1.

[0013] Furthermore, in S3, the reaction temperature in the high-pressure reactor is 120–200°C, and the reaction time is 24–36 h.

[0014] The present invention also provides a copper-doped cobalt tetroxide electrode material, which is prepared by the above-mentioned method for preparing a copper-doped cobalt tetroxide electrode material.

[0015] Furthermore, the copper-doped cobalt tetroxide electrode material is a copper-doped cobalt tetroxide electrode material grown in situ on a three-dimensional network of copper foam.

[0016] This invention also provides the above-mentioned copper-doped cobalt tetroxide electrode material for the electrochemical co-reduction of CO2 and NO3. - Applications in urea production.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs a hydrothermal synthesis method to synthesize copper-doped cobalt tetroxide electrode materials. The foamed copper substrate not only provides a large loading area for the Co-based MOF, enhancing electrode conductivity, but also, the introduction of Cu modulates the electronic structure regulation between Co and Cu, lowering the reaction energy barrier and thus improving the selectivity of urea in the electrochemical process. This invention's copper-doped cobalt tetroxide electrode material successfully constructs uniformly loaded Cu-doped Co3O4 nanoparticles on a three-dimensional network of foamed copper substrates, enabling efficient electrochemical co-reduction of CO2 and NO3. - Urea production is a simple, efficient, and low-cost method suitable for large-scale application.

[0018] 2. The copper-doped cobalt tetroxide electrode material of this invention has a nanosheet morphology, and the nanosheets are interconnected to form a network structure. This structure can promote electron transport and enhance the conductivity of the material; at the same time, the network nanosheets facilitate the exposure of more active sites, which is beneficial for the interaction of the catalyst with CO2 and NO3 in the electrolyte. - Molecular contact promotes coupled electrolytic reactions.

[0019] 3. The copper-doped cobalt tetroxide electrode material of this invention, due to its three-dimensional network structure, ultra-small nanoparticles, and Cu atom doping, is suitable for the electrochemical co-reduction of CO2 and NO3. - The urea production process constructs an efficient gas-liquid-solid three-phase reaction interface, and the use of copper foam as a substrate is beneficial to further enhance the mechanical stability of the electrode material. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation of copper-doped cobalt tetroxide electrode material according to the present invention.

[0021] Figure 2 The following is a schematic diagram of the apparatus for testing the electrosynthetic performance of urea using copper-doped cobalt tetroxide electrode material according to the present invention: (a) is an electrochemical workstation; (b) is an H-type dual-chamber electrolytic cell; (c) is the cathode; (d) is the anode; and (e) is a proton exchange membrane.

[0022] Figure 3 The images show the XRD patterns of Co3O4-Cu / CF in Example 1, Co3O4 in Comparative Example 1, CF-Ar in Comparative Example 2, and Co3O4-CF in Comparative Example 3 of the present invention.

[0023] Figure 4 The following are TEM images, selected area electron diffraction (SED) patterns, and EDS patterns of Co3O4-Cu / CF in Example 1 of the present invention: a and b are TEM images of Co3O4-Cu / CF in Example 1; c is the selected area electron diffraction (SED) pattern of Co3O4-Cu / CF in Example 1; dh is the EDS pattern of Co3O4-Cu / CF in Example 1.

[0024] Figure 5 XPS images of the electrode materials prepared in Example 1 and Comparative Examples 1-3 of the present invention are shown below: a is the XPS full spectrum of Example 1 and Comparative Examples 1-3; b is the Co 2p XPS image of Example 1 and Comparative Examples 1 and 3; c is the Cu 2p XPS image of Example 1 and Comparative Examples 2 and 3; d is the Cu LMM XPS image of Example 1 and Comparative Examples 2 and 3.

[0025] Figure 6 The following are electrochemical performance graphs of the electrode materials prepared in Example 1 and Comparative Examples 1-3 of this invention: a) Linear sweep voltammetry curves of Example 1 and Comparative Examples 1-3 in electrolytes saturated with Ar gas; b) Linear sweep voltammetry curves of Example 1 and Comparative Examples 1-3 in electrolytes saturated with CO2 gas; c) Urea Faradaic efficiency graphs of Example 1 and Comparative Examples 1-3; d) Urea yield graph of Co3O4-Cu / CF in Example 1.

[0026] Figure 7 The electrochemical co-reduction of CO2 and NO3 assembled by Co3O4-Cu / CF in Example 1 of this invention - The figure shows the results of the urea electrosynthesis stability test of the urea production unit under the cycle stability test.

[0027] Figure 8 This is the in-situ infrared spectrum of Co3O4-Cu / CF in Example 1 of the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments: Example 1: like Figure 1 As shown, a method for preparing a copper-doped cobalt tetroxide electrode material includes the following steps: 1) Preparation of impurity-free copper foam: First, cut the copper foam into rectangular sheets of 2.0 cm × 3.0 cm × 0.3 cm and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand for 1 minute, and then remove it to remove the oxide layer on the surface of the copper foam. Then, immerse it in acetone, ethanol, and water in sequence, and sonicate for 15 minutes each to further remove impurities from the surface of the copper foam. Finally, place the pre-treated copper foam in a vacuum oven at 60℃ for drying to obtain copper foam with an impurity-free surface. 2) Prepare cobalt source and organic ligand: Add 0.525 mmol Co(NO3)2·6H2O and 0.525 mmol terephthalic acid to 50 mL of deN,N-dimethylformamide and stir to dissolve into a homogeneous mixed solution; 3) In-situ growth of Co-based MOF on copper foam: The homogeneous mixed solution and a piece of copper foam were transferred to a stainless steel autoclave with a 100 mL polytetrafluoroethylene liner, then sealed and heated at 120 °C for 24 h; after cooling to room temperature, the sample was taken out, washed several times with deionized water, and then dried at 60 °C for 12 h to obtain Co-based MOF material.

[0029] 3) Prepare Co-based MOF material as copper-doped cobalt tetroxide electrode material: Calcine the dried Co-based MOF material at 500℃ for 4 h in Ar atmosphere to obtain copper-doped cobalt tetroxide electrode material, denoted as Co3O4-Cu / CF.

[0030] Example 2: A method for preparing a copper-doped cobalt tetroxide electrode material includes the following steps: 1) Preparation of impurity-free copper foam: First, cut the copper foam into rectangular sheets of 2.0 cm × 3.0 cm × 0.3 cm and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand for 1 minute, and then remove it to remove the oxide layer on the surface of the copper foam. Then immerse it in acetone, ethanol, and water in sequence, and sonicate for 30 minutes each to further remove impurities on the surface of the copper foam. Finally, place the pre-treated copper foam in a vacuum oven at 60℃ for drying to obtain copper foam with an impurity-free surface. 2) Prepare cobalt source and organic ligand: Add 0.525 mmol Co(NO3)2·6H2O and 0.525 mmol terephthalic acid to 50 mL of deN,N-dimethylformamide and stir to dissolve into a homogeneous mixed solution; 3) In-situ growth of Co-based MOF on copper foam: The homogeneous mixed solution and a piece of copper foam were transferred to a stainless steel autoclave with a 100 mL polytetrafluoroethylene liner, then sealed and heated at 120 °C for 24 h; after cooling to room temperature, the sample was taken out, washed several times with deionized water, and then dried at 60 °C for 12 h to obtain Co-based MOF material.

[0031] 3) Prepare Co-based MOF material as copper-doped cobalt tetroxide electrode material: Calcine the dried Co-based MOF material at 500℃ for 4 h in Ar atmosphere to obtain copper-doped cobalt tetroxide electrode material, denoted as Co3O4-Cu / CF.

[0032] Example 3 A method for preparing a copper-doped cobalt tetroxide electrode material includes the following steps: 1) Preparation of impurity-free copper foam: First, cut the copper foam into rectangular sheets of 2.0 cm × 3.0 cm × 0.3 cm and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand for 1 minute, and then remove it to remove the oxide layer on the surface of the copper foam. Then, immerse it in acetone, ethanol, and water in sequence, and sonicate for 15 minutes each to further remove impurities from the surface of the copper foam. Finally, place the pre-treated copper foam in a vacuum oven at 60℃ for drying to obtain copper foam with an impurity-free surface. 2) Prepare cobalt source and organic ligand: Add 0.525 mmol Co(NO3)2·6H2O and 0.0525 mmol terephthalic acid to 50 mL of deN,N-dimethylformamide and stir to dissolve into a homogeneous mixed solution; 3) In-situ growth of Co-based MOF on copper foam: The homogeneous mixed solution and a piece of copper foam were transferred to a stainless steel autoclave with a 100 mL polytetrafluoroethylene liner, then sealed and heated at 120 °C for 24 h; after cooling to room temperature, the sample was taken out, washed several times with deionized water, and then dried at 60 °C for 12 h to obtain Co-based MOF material.

[0033] 3) Prepare Co-based MOF material as copper-doped cobalt tetroxide electrode material: Calcine the dried Co-based MOF material at 500℃ for 4 h in Ar atmosphere to obtain copper-doped cobalt tetroxide electrode material, denoted as Co3O4-Cu / CF.

[0034] Example 4 A method for preparing a copper-doped cobalt tetroxide electrode material includes the following steps: 1) Preparation of impurity-free copper foam: First, cut the copper foam into rectangular sheets of 2.0 cm × 3.0 cm × 0.3 cm and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand for 1 minute, and then remove it to remove the oxide layer on the surface of the copper foam. Then, immerse it in acetone, ethanol, and water in sequence, and sonicate for 15 minutes each to further remove impurities from the surface of the copper foam. Finally, place the pre-treated copper foam in a vacuum oven at 60℃ for drying to obtain copper foam with an impurity-free surface. 2) Prepare cobalt source and organic ligand: Add 0.525 mmol Co(NO3)2·6H2O and 0.525 mmol terephthalic acid to 50 mL of deN,N-dimethylformamide and stir to dissolve into a homogeneous mixed solution; 3) In-situ growth of Co-based MOF on copper foam: The homogeneous mixed solution and a piece of copper foam were transferred to a stainless steel autoclave with a 100 mL polytetrafluoroethylene liner, then sealed and heated at 200 °C for 36 h; after cooling to room temperature, the sample was taken out, washed several times with deionized water, and then dried at 60 °C for 12 h to obtain Co-based MOF material.

[0035] 3) Prepare Co-based MOF material as copper-doped cobalt tetroxide electrode material: Calcine the dried Co-based MOF material at 500℃ for 4 h in Ar atmosphere to obtain copper-doped cobalt tetroxide electrode material, denoted as Co3O4-Cu / CF.

[0036] Comparative Example 1: A method for preparing powdered cobalt tetroxide electrode material includes the following steps: 1) Prepare cobalt source and organic ligand: Add 0.525 mmol Co(NO3)2·6H2O and 0.525 mmol terephthalic acid to 50 mL of deN,N-dimethylformamide and stir to dissolve into a homogeneous mixed solution; 2) Preparation of Co-based MOF powder material: The homogeneous mixed solution was transferred to a stainless steel autoclave with a 100 mL polytetrafluoroethylene liner, then sealed and heated at 120 °C for 24 h; after cooling to room temperature, the sample was taken out, centrifuged with deionized water at 10000 rpm for 1 minute, repeated several times, and then dried at 60 °C for 12 h to obtain Co-based MOF powder material; 3) Preparation of Co-based MOF powder as cobalt tetroxide electrode material: The dried Co-based MOF powder was calcined at 500℃ for 4 h under an Ar atmosphere to obtain cobalt tetroxide powder. Subsequently, 1 mg of cobalt tetroxide powder catalyst was dispersed in 95 μL of isopropanol solution, and 5 μL of Nafion solution was added. The mixture was sonicated for 1 h to obtain a uniformly dispersed catalyst ink. A certain amount of ink was uniformly dropped onto 1.0 cm × 1.5 cm carbon paper (loading capacity of 0.2 mg / cm²). -2 Cobalt tetroxide electrode material was obtained, denoted as Co3O4.

[0037] Comparative Example 2: A method for preparing a foamed copper electrode material includes the following steps: 1) Preparation of impurity-free copper foam: First, cut the copper foam into rectangular sheets of 1.0 cm × 1.5 cm × 0.3 cm and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand for 1 minute, and then remove it to remove the oxide layer on the surface of the copper foam. Then immerse it in acetone, ethanol, and water in sequence, and sonicate for 15 minutes each to further remove impurities on the surface of the copper foam. Finally, place the pre-treated copper foam in a vacuum oven at 60℃ for drying to obtain impurity-free copper foam. 2) Preparation of foamed copper electrode material: The dried foamed copper was calcined at 500℃ for 4 h in Ar atmosphere to obtain foamed copper electrode material, denoted as CF-Ar.

[0038] Comparative Example 3: A method for preparing a copper foam physical composite Co3O4 powder electrode material includes the following steps: 1) Preparation of impurity-free copper foam: First, cut the copper foam into rectangular sheets of 1.0 cm × 1.5 cm × 0.3 cm and pre-treat them. Immerse the cut copper foam in 36% (v / v) concentrated hydrochloric acid, let it stand for 1 minute, and then remove it to remove the oxide layer on the surface of the copper foam. Then immerse it in acetone, ethanol, and water in sequence, and sonicate for 15 minutes each to further remove impurities on the surface of the copper foam. Finally, place the pre-treated copper foam in a vacuum oven at 60℃ for drying to obtain impurity-free copper foam. 2) Preparation of Cobalt Tetraoxide Powder Electrode Material: 0.525 mmol Co(NO3)2·6H2O and 0.525 mmol terephthalic acid were added to 50 mL of des-N,N-dimethylformamide and stirred to dissolve into a homogeneous mixture. The homogeneous mixture was transferred to a stainless steel autoclave with a 100 mL polytetrafluoroethylene liner, sealed, and heated at 120 °C for 24 h. After cooling to room temperature, the sample was removed, centrifuged with deionized water at 10,000 rpm for 1 minute, repeated several times, and then dried at 60 °C for 12 h to obtain Co-based MOF powder material. The dried Co-based MOF powder material was calcined at 500 °C for 4 h under Ar atmosphere to obtain Cobalt Tetraoxide powder material. 3) Preparation of copper foam physically composite Co3O4 powder electrode material: 1 mg of catalyst was dispersed in 95 μL of isopropanol solution, and 5 μL of Nafion solution was added. The mixture was sonicated for 1 h to obtain a uniformly dispersed catalyst ink. A certain amount of the ink was uniformly dropped onto a 1.0 cm × 1.5 cm copper foam (loading amount of 0.2 mg / cm²). -2 A copper foam physical composite Co3O4 powder electrode material was obtained, denoted as Co3O4-CF.

[0039] Performance testing: The electrode materials prepared in Examples 1 and Comparative Examples 1 to 3 of the present invention were characterized: X-ray diffraction (XRD) was used to analyze the crystal structure and possible phase composition of the synthesized catalyst samples; high-resolution transmission electron microscopy (TEM) was used to observe the microstructure and morphology of the electrode materials and characterize the internal structure of the electrode materials; energy dispersive X-ray spectroscopy (EDS) was used to study the elemental composition of the electrode materials; and X-ray photoelectron spectroscopy (XPS) was used to study the elemental state and electronic structure of the electrode materials.

[0040] The electrochemical performance testing of the co-reduction of CO2 and NO3- to urea was conducted using a standard three-electrode system. The three-electrode system used in the electrochemical performance testing corresponding to Example 1 is as follows: Figure 2As shown, (a) is the electrochemical workstation; (b) is the H-type dual-chamber electrolyzer; (c) is the cathode; (d) is the anode; and (e) is the proton exchange membrane. In the three-electrode test system, the working electrode is a copper-doped cobalt tetroxide electrode material (working area 10 mm × 10 mm) fixed by a platinum electrode clamp. The counter electrode is a platinum sheet electrode (working area 10 mm × 10 mm) that does not affect catalytic activity under long-term test conditions. The reference electrode is an Ag / AgCl electrode with good stability. The cathode is used for electrochemical urea synthesis, and the anode is used for the electrochemical oxidation of oxygen molecules in the oxygen evolution reaction (OER). The three-electrode system used for the electrochemical performance tests of Test Examples 1-3 is the same as above, except that the working electrode is adjusted to the electrode material prepared in Test Examples 1-3 corresponding to the platinum electrode clamp.

[0041] The electrolyte solution system used in the above electrochemical test process was a mixed solution of 0.1 M KHCO3 + 0.1 M KNO3 (pH≈5.6); the test was performed by chronoamperometry without current impedance (IR) compensation.

[0042] Depend on Figure 3 As shown in Figure a, due to the excessive intensity of the diffraction peaks on the copper foam substrate and the low loading of Co-MOF on the surface, the sample almost only exhibits the diffraction peaks of Cu. For the Co-MOF / CF precursor, diffraction peaks corresponding to the (300), (001) and (103) crystal planes of Co-MOF were observed in Co-MOF / CF, indicating that Co-BDC has been successfully loaded onto the surface of the copper foam.

[0043] Depend on Figure 3 As shown in Figure b, after pyrolysis of the material, the high-intensity Cu masks the diffraction peaks of Co3O4, making it impossible to observe the Co3O4 diffraction peaks in the XRD pattern. The same result also appears in Co3O4-CF and CF-Ar. Furthermore, for the Co3O4 powder sample, its diffraction peaks match the crystal planes of Co3O4, with corresponding lower peak intensities and slightly wider widths. This is because the Co-MOF forms an amorphous carbon framework during pyrolysis, leading to a certain degree of amorphization in Co3O4.

[0044] Figure 4 The TEM image, selected area electron diffraction pattern and EDS image of Co3O4-Cu / CF in Example 1 of the present invention are shown, wherein a and b are TEM images of Co3O4-Cu / CF in Example 1, c is the selected area electron diffraction pattern of Co3O4-Cu / CF in Example 1, and dh is the EDS image of Co3O4-Cu / CF in Example 1.

[0045] Depend on Figure 4As can be seen from a, a large number of Co3O4 nanoparticles are uniformly dispersed on the Co3O4-Cu / CF nanosheets, and the particle size of the nanoparticles is observed to be about 5 nm. Depend on Figure 4 As can be seen from b, the lattice spacing of the Co3O4 (220) crystal plane is 0.285 nm; Depend on Figure 4 As can be seen from c, Co3O4-Cu / CF contains the (200), (511), and (311) crystal planes of Co3O4; Depend on Figure 4 As can be seen from dh, the uniform distribution of C, Co, Cu and O in Co3O4-Cu / CF proves the successful introduction of Cu.

[0046] Figure 5 XPS images of the electrode materials prepared in Example 1 and Comparative Examples 1-3 of the present invention are shown, where a is the XPS full spectrum of Example 1 and Comparative Examples 1-3, b is the Co 2p XPS image of Example 1 and Comparative Examples 1 and 3, c is the Cu 2p XPS image of Example 1 and Comparative Examples 2 and 3, and d is the Cu LMM XPS image of Example 1 and Comparative Examples 2 and 3.

[0047] Depend on Figure 5 As can be seen from a, Co3O4-Cu / CF contains C, Co, Cu and O elements; Depend on Figure 5 As can be seen from b, the Co in Co3O4-Cu / CF exists in the state of Co3O4; Depend on Figure 5 As can be seen from the cd, Cu exists in the state of Cu2O in Co3O4-Cu / CF, and there is electronic restructuring between Cu and Co.

[0048] Figure 6 Electrochemical performance graphs of the electrode materials prepared in Example 1 and Comparative Examples 1-3 of the present invention are shown, where a is the linear sweep voltammetry curve of Example 1 and Comparative Examples 1-3 in an electrolyte saturated with Ar gas, b is the linear sweep voltammetry curve of Example 1 and Comparative Examples 1-3 in an electrolyte saturated with CO2 gas, c is the urea Faradaic efficiency graph of Example 1 and Comparative Examples 1-3, and d is the urea yield graph of Co3O4-Cu / CF in Example 1.

[0049] Depend on Figure 6 As can be seen from a, Co3O4-Cu / CF has excellent nitrate electroreduction activity; Depend on Figure 6 As shown in b, Co3O4-Cu / CF exhibits excellent electrochemical co-reduction properties for CO2 and NO3. -It inhibits urea production, and the presence of CO2 can effectively suppress nitrate electroreduction activity; Depend on Figure 6 As shown in c, Co3O4-Cu / CF has the best urea Faradaic efficiency (30.6%), which is significantly better than Co3O4 (16.6%), Co3O4-CF (9.0%), and CF-Ar (2.1%). Depend on Figure 6 As can be seen from d, Co3O4-Cu / CF has the optimal urea yield (approximately 17 mmol / h). -1 g -1 ).

[0050] Depend on Figure 7 It can be seen that after 6 hours of cyclic operation, the electrochemical co-reduction of CO2 and NO3 by the Co3O4-Cu / CF self-assembled system is achieved. - The urea production unit showed no significant performance degradation and demonstrated excellent stability.

[0051] Depend on Figure 8 It can be seen that the effects of Co3O4-Cu / CF on the electrochemical co-reduction of CO2 and NO3 were detected using in-situ infrared spectroscopy. - The intermediates in the urea production process were detected, and key intermediates such as *NH2CO were successfully identified, proving the successful synthesis of urea.

[0052] In summary, compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs a hydrothermal synthesis method to synthesize copper-doped cobalt tetroxide electrode materials. The foamed copper substrate not only provides a large loading area for the Co-based MOF, enhancing electrode conductivity, but also, the introduction of Cu modulates the electronic structure regulation between Co and Cu, lowering the reaction energy barrier and thus improving the selectivity of urea in the electrochemical process. This invention's copper-doped cobalt tetroxide electrode material successfully constructs uniformly loaded Cu-doped Co3O4 nanoparticles on a three-dimensional network of foamed copper substrates, enabling efficient electrochemical co-reduction of CO2 and NO3. - Urea production is a simple, efficient, and low-cost method suitable for large-scale application.

[0053] 2. The copper-doped cobalt tetroxide electrode material of this invention has a nanosheet morphology, and the nanosheets are interconnected to form a network structure. This structure can promote electron transport and enhance the conductivity of the material; at the same time, the network nanosheets facilitate the exposure of more active sites, which is beneficial for the interaction of the catalyst with CO2 and NO3 in the electrolyte. - Molecular contact promotes coupled electrolytic reactions.

[0054] 3. The copper-doped cobalt tetroxide electrode material of this invention, due to its three-dimensional network structure, ultra-small nanoparticles, and Cu atom doping, is suitable for the electrochemical co-reduction of CO2 and NO3. - The urea production process constructs an efficient gas-liquid-solid three-phase reaction interface, and the use of copper foam as a substrate is beneficial to further enhance the mechanical stability of the electrode material.

[0055] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a copper-doped cobalt tetroxide electrode material, characterized in that, Includes the following steps: S1. Cut the foamed copper into rectangular pieces and pre-treat them. Immerse the cut foamed copper in 36% volume fraction concentrated hydrochloric acid, let it stand, and then take it out to remove the oxide layer on the surface of the foamed copper. Then immerse it in acetone, ethanol and water in sequence, and sonicate it to further remove impurities on the surface of the foamed copper, so as to obtain foamed copper with no impurities on the surface. S2. Disperse the cobalt source and terephthalic acid sequentially in a solvent, and stir until fully dissolved to obtain a mixed solution; S3. The foamed copper obtained in step S1 and the mixed solution obtained in step S2 are transferred to a high-pressure reactor for reaction. After the reaction is completed, the mixture is cooled to room temperature, washed with deionized water, and then vacuum dried to obtain Co-based MOF material. Then, it is calcined to obtain copper-doped cobalt tetroxide electrode material grown in situ on three-dimensional network foamed copper.

2. The method for preparing a copper-doped cobalt tetroxide electrode material according to claim 1, characterized in that, In S1, the ultrasound time is 15-30 min.

3. The method for preparing a copper-doped cobalt tetroxide electrode material according to claim 1, characterized in that, In S2, the cobalt source is either nitrate or acetate.

4. The method for preparing a copper-doped cobalt tetroxide electrode material according to claim 1, characterized in that, In S2, the molar ratio of the added cobalt source to terephthalic acid is 1:0.1 to 1.

5. The method for preparing a copper-doped cobalt tetroxide electrode material according to claim 1, characterized in that, In S3, the reaction temperature in the high-pressure reactor is 120–200℃, and the reaction time is 24–36 h.

6. A copper-doped cobalt tetroxide electrode material, prepared by the preparation method of the copper-doped cobalt tetroxide electrode material according to any one of claims 1 to 5.

7. The copper-doped cobalt tetroxide electrode material according to claim 6 in the electrochemical co-reduction of CO2 and NO3 - Applications in urea preparation.

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