Preparation method and application of self-supporting cobalt sulfide electrode and self-supporting cobalt sulfide-molybdenum disulfide heterojunction electrode

Abstract

The invention discloses a preparation method and application of a self-supporting cobalt sulfide electrode and a preparation method and application of a self-supporting cobalt sulfide-molybdenum disulfide heterojunction electrode, and belongs to the technical field of electrodes. The self-supporting cobalt sulfide electrode is prepared by compounding CoSx nanoparticles and activated carbon fiber paper together through melamine formaldehyde-polyethyleneimine resin and then performing high-temperature annealing. The self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode is prepared by compounding CoS < x >-coated MoS2 nanoparticles and activated carbon fiber paper together by melamine formaldehyde-polyethyleneimine resin, and then performing high-temperature annealing to obtain the self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode. The two self-supporting electrodes provided by the invention have long service life, high catalytic activity, high stability and relatively strong by-product interference resistance, green and environment-friendly materials and processes are adopted in the preparation process, and compared with a traditional complex multi-step preparation method, the scheme adopts simplified processes such as high-temperature annealing, so that the production energy consumption is remarkably reduced, and the production cost is reduced. The method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the field of electrode technology, and in particular to a preparation method and application of a self-supporting cobalt sulfide electrode and a self-supporting cobalt sulfide-molybdenum disulfide heterojunction electrode. Background Art

[0002] With the acceleration of global energy transformation, hydrogen as a clean energy is gaining more and more attention in energy storage, transportation and industrial applications. Water electrolysis is a very effective way to produce hydrogen, especially when there is an excess of renewable energy (such as wind and solar energy), which can convert excess electricity into hydrogen and store it. However, due to the shortage of water resources and the high cost of water electrolysis, seawater electrolysis has become a promising alternative. Seawater electrolysis has the advantages of abundant seawater resources, efficient energy storage, and reduced carbon emissions, but it also faces the following three technical problems:

[0003] ① Catalysts are prone to deterioration during prolonged storage, especially in high-temperature, high-humidity environments, leading to reduced catalytic activity and thus affecting the efficiency and performance of water electrolysis. Existing catalyst materials often lack stable carriers and support materials, making them prone to structural collapse or surface corrosion during storage, affecting catalytic activity and lifespan.

[0004] ② Existing catalyst materials usually face the problems of reduced catalyst activity and insufficient durability under high load current, resulting in the decline of electrolytic performance during long-term use.

[0005] ③ When electrolyzing seawater, the generation of byproducts is unavoidable, particularly chlorine, which not only pollutes the environment but can also corrode electrode materials. Furthermore, calcium and magnesium ions in seawater can form precipitates, affecting the efficiency of the catalytic electrodes and electrolytic cell.

[0006] Based on this, it is extremely important to effectively improve the service life, catalytic activity, and resistance to by-product interference of the electrode. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method and application of a self-supporting cobalt sulfide electrode and a self-supporting cobalt sulfide-molybdenum disulfide heterojunction electrode, so as to at least effectively improve the service life, catalytic activity, and resistance to by-product interference of the two electrodes.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] Technical solution 1:

[0010] A self-supporting cobalt sulfide electrode, CoS xThe nanoparticles are compounded with activated carbon fiber paper and then annealed at high temperature to obtain the product.

[0011] In the above solution, the activated carbon fiber paper is the conductive substrate, which is obtained by activating commercial carbon paper purchased from the market, and can improve the hydrophilic property.

[0012] Melamine-formaldehyde-polyethyleneimine resin is a functional binder, obtained by mixing melamine-formaldehyde resin oligomers with polyethyleneimine in a specific ratio. The present invention uses melamine-formaldehyde-polyethyleneimine resin as a binder to load functional particles onto a substrate. This method is highly scalable and can be widely applied to various seawater electrolysis hydrogen production technologies by varying the functional particles and substrate materials, paving the way for large-scale industrialization.

[0013] CoS x Nanoparticles are active electrocatalysts.

[0014] The self-supporting CoS provided by the present invention x The electrode is made by combining the active electrocatalyst and the conductive substrate with a functional adhesive and then annealing at high temperature. The electrode has long life, high catalytic activity, high stability and strong resistance to by-product interference, effectively overcoming the technical defects mentioned in the background technology.

[0015] Preferably, the CoS x The preparation method of nanoparticles is as follows: cobalt nitrate hexahydrate and thioacetamide are added to a mixed solution of water and dimethylformamide (DMF), stirred until the materials are dissolved and then fully reacted under certain conditions, and then centrifuged, washed and dried to obtain CoS x Nanoparticles.

[0016] Preferably, the mass ratio of cobalt nitrate hexahydrate to thioacetamide is (0.2-2):(1-4); the temperature for fully reacting cobalt nitrate hexahydrate and thioacetamide is 160-220° C., and the time for fully reacting is 12-48 hours.

[0017] Technical solution 2:

[0018] A method for preparing a self-supporting cobalt sulfide electrode comprises the steps of: firstly mixing melamine formaldehyde-polyethyleneimine resin and CoS x The nanoparticles were mixed evenly and then applied to both sides of the activated carbon fiber paper. Finally, after drying and high-temperature annealing, self-supporting cobalt sulfide (CoS x )electrode.

[0019] Technical solution three:

[0020] The water electrolysis process is an electrochemical reaction that decomposes water molecules into hydrogen and oxygen. This process consists of two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). In the actual electrolysis process, these two reactions are independent of each other but closely related. Excellent electrode materials need to have good HER and OER catalytic performance at the same time. Based on this, the present invention proposes a bifunctional heterojunction electrode that exhibits efficient catalytic activity in both reactions, as follows:

[0021] A self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode is prepared by melamine formaldehyde-polyethyleneimine resin to form CoS x @MoS2 nanoparticles are compounded with activated carbon fiber paper and then annealed at high temperature.

[0022] In the above scheme, the activated carbon fiber paper is obtained by activating commercial carbon paper purchased from the market, which can improve the hydrophilicity.

[0023] Melamine formaldehyde-polyethyleneimine resin is a functional adhesive, which is obtained by mixing melamine-formaldehyde resin oligomer and polyethyleneimine in a certain proportion.

[0024] CoS x @MoS2 nanoparticles are active electrocatalysts.

[0025] The self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode provided by the present invention is prepared by combining an active electrocatalyst with a conductive substrate by a functional adhesive and then annealing at high temperature. The electrode has a long life, high catalytic activity, high stability and strong resistance to by-product interference, effectively overcoming the technical defects mentioned in the background technology.

[0026] Preferably, the preparation method of the cobalt sulfide-molybdenum disulfide nanoparticles is as follows:

[0027] A. Add cobalt nitrate hexahydrate and thioacetamide to a mixed solution of water and dimethylformamide, stir until the materials are dissolved, and then react fully at a certain temperature. After centrifugation, washing and drying, CoS x Nanoparticles;

[0028] B. Dissolve glucose in water and stir thoroughly until dissolved, then add CoS x Nanoparticles, sodium molybdate dihydrate and thiourea are fully mixed and reacted under certain conditions, and then centrifuged, washed and dried to obtain CoS x @MoS2 nanoparticles.

[0029] Preferably, CoSx The mass ratio of nanoparticles, sodium molybdate dihydrate and thiourea is (30-100): (0.1-1):

[0030] (0.1~1); CoS x The temperature for fully reacting the nanoparticles, sodium molybdate dihydrate and thiourea is 160-220° C., and the time for fully reacting the nanoparticles is 12-48 hours.

[0031] Technical solution four:

[0032] A method for preparing a self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode, comprising: reacting melamine formaldehyde-polyethyleneimine resin and CoS x The MoS2 nanoparticles were mixed evenly and then applied to both sides of the activated carbon fiber paper. Finally, after drying and high-temperature annealing, a self-supporting cobalt sulfide-molybdenum disulfide (CoS x @MoS2) dual-functional heterojunction electrode.

[0033] Technical solution five:

[0034] Application of a self-supporting cobalt sulfide electrode in seawater electrolysis, wherein the self-supporting cobalt sulfide electrode serves as a cathode material in a seawater electrolysis cell.

[0035] Technical solution six:

[0036] Application of self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode in seawater electrolysis. Self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode as cathode and anode materials in seawater electrolysis cells.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. Self-supporting CoS provided by the present invention x The electrode is made of functional binder to bind CoS x Nanoparticles are compounded with a conductive substrate and then annealed at high temperature to obtain an electrode with long life, high catalytic activity, high stability and strong resistance to by-product interference. x As a catalyst, the simple synthesis method is not only low-cost, but also exhibits excellent electrocatalytic performance, making it a cost-effective option. The entire preparation process utilizes environmentally friendly materials and processes, avoiding the use of harmful chemicals in traditional methods, thereby enhancing the process's environmental friendliness and sustainability. Compared with traditional, complex, multi-step preparation methods, this approach utilizes simplified processes such as high-temperature annealing, significantly reducing production energy consumption and making it suitable for large-scale industrial production.

[0039] 2. Self-supporting CoS provided by the present invention x @MoS2 dual-functional heterojunction electrode is made of functional binder to form CoSx @MoS2 nanoparticles are compounded with a conductive substrate and then annealed at high temperature. The electrode has long life, high catalytic activity, high stability and strong resistance to by-product interference. x MoS2 catalysts are simple to synthesize, inexpensive, and exhibit excellent electrocatalytic performance, making them a cost-effective option. The entire preparation process utilizes environmentally friendly materials and processes, avoiding the use of hazardous chemicals in traditional methods and enhancing their environmental sustainability. Compared to traditional, complex, multi-step preparation methods, this approach utilizes simplified processes such as high-temperature annealing, significantly reducing production energy consumption and making it suitable for large-scale industrial production.

[0040] In addition, self-supporting CoS x @MoS2 dual-function heterojunction electrode also has the following beneficial effects:

[0041] ① It has the stability and dual catalytic function of a self-supporting cobalt oxide composite electrode: the electrode exhibits excellent HER and OER dual catalytic performance in alkaline seawater with a pH of 14, and can operate stably for a long time at a high current density, showing excellent durability and stability.

[0042] ② Integrated structural design: This electrode material adopts an integrated design, which has a high specific surface area and good conductivity. This structural design not only improves catalytic activity, but also enhances the material's stability, corrosion resistance, and anti-toxicity.

[0043] ③ Bifunctional catalytic performance: The catalyst has the ability to catalyze HER and OER simultaneously, which simplifies the design of the reaction system, reduces the synthesis cost of the catalyst, and achieves more efficient, sustainable and economical energy conversion.

[0044] ④ Applicable to all pH environments: The material exhibits catalytic activity in both acidic and alkaline environments, demonstrating its broad adaptability. This cross-pH catalytic activity gives the material high application potential and its adaptability to a variety of electrolyte environments. This characteristic significantly improves the flexibility and stability of the electrolysis system, making the material highly competitive in practical applications.

[0045] 3. Both electrodes provided by the present invention can effectively overcome the three technical deficiencies mentioned in the background art, as follows:

[0046] Technical Problem ①: The catalyst materials in the existing technology are prone to deterioration when stored for a long time.

[0047] The present invention uses melamine formaldehyde-polyethyleneimine resin as a binder to form an active electrocatalyst CoS x Nanoparticles or CoS xMoS2 nanoparticles are combined with a conductive substrate of activated carbon fiber paper to form a self-supporting composite electrode material. A high-temperature annealing process strengthens the bonding between the catalyst and the carbon fiber paper, forming a robust composite structure. This design not only enhances the mechanical strength and conductivity of the catalyst material, but also extends its shelf life and stability during storage, reducing the risk of catalyst deterioration.

[0048] Technical problem ②: The catalyst material has poor stability after long-term use.

[0049] The present invention uses high-temperature annealing to achieve a good bond between the active electrocatalyst and the carbon fiber substrate, enhancing the overall stability of the composite electrode. The self-supporting structure makes the electrode less susceptible to deformation under stress, thereby greatly improving the stability of the catalyst.

[0050] After testing, the CoS provided by the present invention x @NC / CP-800 electrode material electrolyzed in alkaline seawater, HER reaction at 500mA / cm 2 The material exhibited excellent electrocatalytic performance in both alkaline seawater and natural seawater, operating stably for long periods of time, demonstrating good practicality and durability, and providing a reliable solution for hydrogen production from seawater electrolysis.

[0051] The CAM@NC / CP-900 electrode material provided by the present invention is electrolyzed in alkaline seawater, and the HER reaction is at 500 mA / cm 2 There is no obvious attenuation after continuous electrolysis for 200 hours at a current density of 1.5 %.

[0052] Technical problem ③: By-products such as chlorine gas and calcium and magnesium ion precipitation are produced during electrolysis.

[0053] This material tightly integrates a self-supporting composite electrode, an active electrocatalyst, and a conductive substrate, effectively reducing the direct effects of chlorine and other byproducts on the electrode surface. The self-supporting structure enhances the electrode's corrosion and interference resistance, enabling it to maintain high catalytic activity and stability in seawater electrolysis.

[0054] After testing, the CoS provided by the present invention x @NC / CP-800 electrode material has no calcium and magnesium ion precipitation on its surface after 300 hours of electrolysis in natural seawater.

[0055] After electrolysis in seawater, no calcium or magnesium ions are precipitated or attached to the surface of the CAM@NC / CP-900 electrode material provided by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 :CoS x@NC / CP-T self-supporting catalytic electrode preparation process;

[0057] Figure 2 :(a)CoS x , (b,c)CoS x SEM images of @NC / CP-800, (d, e) CoS x , (f)CoS x @NC / CP-

[0058] TEM image of 800, (g)CoS x , (h)CoS x @NC / CP-800 element distribution mapping diagram, (i) CoS x ,CP,CoS x XRD pattern of @NC / CP-T;

[0059] Figure 3 :CoS x HER performance test and Tafel curve of @NC / CP-T material in alkaline electrolyte.

[0060] (a) LSV curve and (b) Tafel curve of HER tested in 1 M KOH. (c) LSV curve and (d) Tafel curve of HER tested in alkaline seawater.

[0061] Figure 4 :CoS x HER performance test and Tafel curve of @NC / CP-T material in neutral electrolyte. (a) HER LSV curve and (b) Tafel curve tested in 1M PBS solution. (c) HER LSV curve and (d) Tafel curve tested in natural seawater.

[0062] Figure 5 :CoS x @NC / CP-800 300-hour three-electrode stability test in alkaline seawater;

[0063] Figure 6 :CoS x 300-hour three-electrode stability test of NC / CP-800 in 1M KOH;

[0064] Figure 7 :CoS x @NC / CP-800 300-hour three-electrode stability test in natural seawater;

[0065] Figure 8:(a,b) SEM images of CAM, (ce) TEM images of CAM, (f) EDX spectrum of CAM;

[0066] Figure 9 :(a,b)CAM@NC / CP-700;(c,d)CAM@NC / CP-800;(e,f)SEM images of CAM@NC / CP-900;

[0067] Figure 10 : LSV curves of (a) HER and (b) OER of CAM@NC / CP-T materials tested in 1 M KOH; LSV curves of (c) HER and (d) OER tested in alkaline seawater;

[0068] Figure 11 : LSV curves of (a) HER and (b) OER of CAM@NC / CP-T materials tested in 0.5 M H2SO4; LSV curves of (c) HER and (d) OER tested in acidic seawater;

[0069] Figure 12 : HER three-electrode stability test of CAM@NC / CP-900 in alkaline seawater;

[0070] Figure 13 :OER three-electrode stability test of CAM@NC / CP-900 in alkaline seawater;

[0071] Figure 14 : Stability test of two electrodes of CAM@NC / CP-900 in alkaline seawater. DETAILED DESCRIPTION

[0072] Example 1: Self-Supported CoS x Electrode CoS x Preparation of @NC / CP-600 (preparation process as Figure 1 shown).

[0073] S1. Raw material preparation:

[0074] Preparation of activated carbon fiber paper: Commercially available carbon fiber paper was cut into 1 cm × 2 cm pieces, mixed with 50 mL of 1 mol / L HNO3, and placed in a 95°C oven to react for 12 hours. The mixture was washed with deionized water until neutral, mixed with 50 mL of 1 mol / L NaOH, and placed in a 95°C oven to react for 12 hours. The mixture was washed with deionized water until neutral, and dried to obtain activated carbon fiber paper.

[0075] Synthesis of melamine-formaldehyde-polyethyleneimine resin: 3.0 g of melamine, 5.4 mL of deionized water, and 6.9 mL of formaldehyde were mixed and stirred in an 80°C water bath with magnetic stirring until clear to obtain oligomeric melamine-formaldehyde resin. The resulting oligomeric melamine-formaldehyde resin was mixed with polyethyleneimine in a 1:1 mass ratio and thoroughly ground to obtain melamine-formaldehyde-polyethyleneimine resin (MP).

[0076] CoS x Nanoparticle synthesis: 1g of cobalt nitrate hexahydrate and 1.6g of thioacetamide were dissolved in a mixture of 14mL of water and 14mL of DMF, stirred thoroughly until dissolved, and magnetically stirred at medium speed for 30min. The mixture was placed in a reactor and reacted at 200°C for 24h. After the reaction was completed, the mixture was centrifuged at 9000rpm for 3min, washed three times with water and once with ethanol, and dried in an oven at 65°C to obtain CoS x Nanoparticles.

[0077] S2. Preparation of composite electrodes:

[0078] Weigh 20 mg of CoS x The activated carbon fiber paper was mixed with MP in a mass ratio of 1:5, and then applied to the surface of the activated carbon fiber paper after being evenly mixed. After being dried in an oven, the reverse side was applied in the same way. After drying and curing, the paper was placed in a tube furnace, maintained in a N2 atmosphere, and heated to 600°C at a heating rate of 5°C / min. After being kept at this temperature for 2 hours, the temperature was naturally lowered to obtain CoS x @NC / CP-600.

[0079] To evaluate CoS x The electrocatalytic performance of the NC / CP-600 composite electrode material in different environments was tested in 1M KOH solution, alkaline seawater, 1M PBS (simulated seawater) and natural seawater (e.g. Figure 3 , 4). In 1M KOH solution, the electrode is at 100mA / cm 2 The HER reaction overpotential at the current density is 0.643V, and the Tafel slope is 704.8mV / dec. In alkaline seawater, the HER overpotential is reduced to 0.470V, and the Tafel slope is also significantly reduced to 355.8mV / dec. In 1M PBS, when the current density is 10mA / cm 2 When the HER overpotential is 0.378 V, the Tafel slope is 244 mV / dec; while in natural seawater, the HER overpotential is 0.427 V, and the Tafel slope is 636.5 mV / dec.

[0080] Example 2: Self-Supported CoS x Electrode CoS xPreparation of @NC / CP-700.

[0081] Compared with Example 1, only the temperature in step S2 is changed from 600° C. to 700° C., and the remaining steps and parameters are all the same as those in Example 1.

[0082] To evaluate CoS x The electrocatalytic performance of the NC / CP-700 composite electrode material in different environments was tested in 1M KOH solution, alkaline seawater, 1M PBS and natural seawater (e.g. Figure 3 , 4). In 1M KOH solution, the electrode is at 100 mA / cm 2 The HER reaction overpotential at the current density is 0.508V, and the Tafel slope is 643.1mV / dec. In alkaline seawater, the HER overpotential is reduced to 0.398V, and the Tafel slope is also significantly reduced to 299.8mV / dec. In 1M PBS, when the current density is 10mA / cm 2 When the HER overpotential is 0.322 V, the Tafel slope is 220.9 mV / dec; while in natural seawater, the HER overpotential is 0.422 V, and the Tafel slope is 423.8 mV / dec.

[0083] Example 3: Self-Supported CoS x Electrode CoS x Preparation of @NC / CP-800.

[0084] Compared with Example 1, only the temperature in step S2 is changed from 600° C. to 800° C., and the remaining steps and parameters are all the same as those in Example 1.

[0085] Obtained CoS x @NC / CP-800 composite electrode material SEM photos, TEM photos, element distribution mapping and XRD patterns, etc. Figure 2 shown.

[0086] To evaluate CoS x The electrocatalytic performance of the NC / CP-800 composite electrode material in different environments was tested in 1M KOH solution, alkaline seawater, 1M PBS and natural seawater (e.g. Figure 3 , 4). In 1M KOH solution, the electrode is at 100 mA / cm 2 The HER reaction overpotential at the current density is 0.349V, and the Tafel slope is 500.9mV / dec. In alkaline seawater, the HER overpotential is reduced to 0.258V, and the Tafel slope is also significantly reduced to 262.0mV / dec. In 1M PBS, when the current density is 10mA / cm 2When the HER overpotential is 0.222 V, the Tafel slope is 206.2 mV / dec; while in natural seawater, the HER overpotential is 0.288 V, and the Tafel slope is 273.9 mV / dec.

[0087] In addition, the prepared CoS x The following experiments were conducted on the NC / CP-800 composite electrode material:

[0088] Experiment 1: Self-Supported CoS x Electrode CoS x @NC / CP-800 produces hydrogen by electrolysis of water in alkaline seawater at pH=14 (such as Figure 5 shown).

[0089] The present invention uses the composite electrode material CoS x @NC / CP-800, graphite electrode, silver / silver chloride electrode and alkaline seawater with pH=14 constitute the electrolytic cell system.

[0090] pass Figure 5 It can be seen that when compared with commercial Pt / C catalysts, the composite electrode material CoS x @NC / CP-800 shows good stability and anti-interference ability. It can still maintain 100% current density after 300 hours of stable operation. At the same time, there is no obvious calcium and magnesium ion precipitation on the surface. The composite electrode material CoS x @NC / CP-800 demonstrated good stability and anti-interference capabilities, and its catalytic performance was not affected.

[0091] Experiment 2: Self-Supported CoS x Electrode CoS x @NC / CP-800 produces hydrogen by electrolysis of water in 1M KOH (such as Figure 6 shown).

[0092] The present invention simulates the real industrial electrolysis water hydrogen production environment and combines the composite electrode material CoS x @NC / CP-800, graphite electrode, silver / silver chloride electrode and 1M KOH form the electrolytic cell system.

[0093] pass Figure 6 It can be seen that when compared with commercial Pt / C catalysts, the composite electrode material CoS x @NC / CP-800 shows good stability and anti-interference ability. It can still maintain 100% current density after 300 hours of stable operation, and the current density drops to 60% after only 70 hours of operation. x @NC / CP-800 demonstrated good stability and anti-interference capabilities, and its catalytic performance was not affected.

[0094] Experiment 3: Self-Supported CoS x Electrode CoS x @NC / CP-800 produces hydrogen by electrolysis of water in natural seawater (such as Figure 7 shown).

[0095] The present invention uses the composite electrode material CoS in a natural seawater environment. x @NC / CP-800, graphite electrodes, silver / silver chloride electrodes and natural seawater form an electrolytic cell system.

[0096] pass Figure 7 It can be seen that when compared with commercial Pt / C catalysts, the composite electrode material CoS x @NC / CP-800 demonstrated excellent stability and anti-interference capabilities, maintaining a current density of 63% after 300 hours of stable operation. At the same time, there was no obvious calcium and magnesium ion precipitate attached to the electrode material surface. However, the electrode material prepared with commercial Pt / C catalyst had a large amount of precipitate attached to the surface after the test, which seriously hindered the reaction and reduced the current density to 60% after only 70 hours of operation. x @NC / CP-800 demonstrates good stability and anti-interference capabilities.

[0097] Example 4: Preparation of self-supporting CAM@NC / CP-700 electrodes.

[0098] S1. Raw material preparation:

[0099] Preparation of activated carbon fiber paper: Commercially available carbon fiber paper was cut into 1 cm × 2 cm pieces, mixed with 50 mL of 1 mol / L HNO3, and placed in a 95°C oven to react for 12 hours. The mixture was washed with deionized water until neutral, mixed with 50 mL of 1 mol / L NaOH, and placed in a 95°C oven to react for 12 hours. The mixture was washed with deionized water until neutral, and dried to obtain activated carbon fiber paper.

[0100] Synthesis of melamine-formaldehyde-polyethyleneimine resin: 3.0 g of melamine, 5.4 mL of deionized water, and 6.9 mL of formaldehyde were mixed and stirred in an 80°C water bath with magnetic stirring until the mixture became clear, thereby obtaining an oligomeric melamine-formaldehyde resin. The resulting oligomeric melamine-formaldehyde resin was then mixed with polyethyleneimine in a 1:1 mass ratio and thoroughly ground to obtain a melamine-formaldehyde-polyethyleneimine resin.

[0101] CoS xNanoparticle synthesis: 1g of cobalt nitrate hexahydrate and 1.6g of thioacetamide were dissolved in a mixture of 14mL of water and 14mL of DMF, stirred thoroughly until dissolved, and magnetically stirred at medium speed for 30min. The mixture was placed in a reactor and reacted at 200°C for 24h. After the reaction was completed, the mixture was centrifuged at 9000rpm for 3min, washed three times with water and once with ethanol, and dried in an oven at 65°C to obtain CoS x Nanoparticles.

[0102] S2.CoS x @MoS2 nanoparticles (CAM nanoparticles) synthesis:

[0103] Dissolve 0.225g glucose in 25mL water and stir thoroughly until dissolved, then add 70mg CoS x Nanoparticles, 0.2g sodium molybdate dihydrate, 0.6g thiourea, medium speed magnetic stirring for 30min. Place in a reactor and react at 200℃ for 24h. After the reaction is completed, centrifuge at 9000rpm for 3min to separate, wash three times with ethanol, and place in a 65℃ oven to dry to obtain CAM nanoparticles. Its SEM images (a-b), TEM images (c-e) and EDX spectrum (f) are as follows Figure 8 shown.

[0104] S3. Preparation of self-supporting CAM@NC / CP-700 electrodes:

[0105] 20 mg of CAM was weighed and mixed with MP at a mass ratio of 1:5. After mixing evenly, it was applied to the surface of the activated carbon fiber paper. After drying in an oven, the reverse side was applied in the same way. After curing, the paper was placed in a tube furnace, maintained in a N2 atmosphere, and heated to 700°C at a rate of 5°C / min. After keeping the temperature for 2 hours, the paper was cooled naturally to obtain CAM@NC / CP-700.

[0106] In order to test the electrocatalytic performance of the CAM@NC / CP-700 composite electrode material in alkaline seawater environment, the present invention carried out electrochemical tests in 0.5M H2SO4 solution, acidic seawater, 1M KOH solution and alkaline seawater respectively ( Figure 10 , 11). In 0.5M H2SO4 solution, when the current density is 100mA / cm 2 When the HER overpotential is 0.602V, at 50mA / cm 2 The OER reaction overpotential at the current density is 0.582V; in acidic seawater, when the current density is 100mA / cm 2 When the HER overpotential is 0.700 V, at 50 mA / cm 2The OER reaction overpotential at the current density is 0.566V; in 1M KOH solution, the electrode is at 100mA / cm 2 The HER reaction overpotential at the current density is 0.616V, and at 50mA / cm 2 The OER reaction overpotential at the current density is 0.513 V; in alkaline seawater, when the current density is 100 mA / cm 2 When the HER overpotential is 0.646V, at 50mA / cm 2 The OER reaction overpotential at this current density is 0.539 V.

[0107] Example 5: Preparation of self-supporting CAM@NC / CP-800 electrodes.

[0108] Compared with Example 1, only the temperature in step S3 is changed from 700° C. to 800° C., and the remaining steps and parameters are all the same as those in Example 1.

[0109] In order to test the electrocatalytic performance of the CAM@NC / CP-800 composite electrode material in alkaline seawater environment, the present invention carried out electrochemical tests in 0.5M H2SO4 solution, acidic seawater, 1M KOH solution and alkaline seawater respectively ( Figure 10 , 11). In 0.5M H2SO4 solution, when the current density is 100mA / cm 2 When the HER overpotential is 0.557V, at 50mA / cm 2 The OER reaction overpotential at the current density is 0.528V; in acidic seawater, when the current density is 100mA / cm 2 When the HER overpotential is 0.537V, at 50mA / cm 2 The OER reaction overpotential at the current density is 0.543V; in 1M KOH solution, the electrode is at 100mA / cm 2 The HER reaction overpotential at the current density is 0.471V, and at 50mA / cm 2 The OER reaction overpotential at the current density is 0.431V; in alkaline seawater, when the current density is 100mA / cm 2 When the HER overpotential is 0.393V, at 50mA / cm 2 The OER reaction overpotential at this current density is 0.352 V.

[0110] Example 6: Preparation of self-supporting CAM@NC / CP-900 electrodes.

[0111] Compared with Example 1, only the temperature in step S3 is changed from 700° C. to 900° C., and the remaining steps and parameters are all the same as those in Example 1.

[0112] In order to test the electrocatalytic performance of CAM@NC / CP-900 composite electrode material in alkaline seawater environment, the present invention carried out electrochemical tests in 0.5M H2SO4 solution, acidic seawater, 1M KOH solution and alkaline seawater respectively ( Figure 10 , 11). In 0.5M H2SO4 solution, when the current density is 100mA / cm 2 When the HER overpotential is 0.459V, at 50mA / cm 2 The OER reaction overpotential at the current density is 0.411 V; in acidic seawater, when the current density is 100 mA / cm 2 When the HER overpotential is 0.445V, at 50mA / cm 2 The OER reaction overpotential at the current density is 0.370 V; in 1 M KOH solution, the electrode is at 100 mA / cm 2 The HER reaction overpotential at the current density is 0.369 V, and at 50 mA / cm 2 The OER reaction overpotential at the current density is 0.369 V; in alkaline seawater, when the current density is 100 mA / cm 2 When the HER overpotential is 0.341V, at 50mA / cm 2 The OER reaction overpotential at this current density is 0.351 V.

[0113] The SEM images of CAM@NC / CP-700, CAM@NC / CP-800 and CAM@NC / CP-900 prepared in Examples 4-6 are shown in FIG. Figure 9 As shown in a~b, c~d and e~f.

[0114] In addition, the self-supporting CAM@NC / CP-900 electrode was subjected to the following experiments:

[0115] Experiment 4: Three-electrode HER reaction stability test in alkaline seawater at pH = 14 (as Figure 12 shown).

[0116] The present invention simulates a real industrial water electrolysis hydrogen production environment, and combines composite electrode material CAM@NC / CP-900, graphite electrode, silver / silver chloride electrode and alkaline seawater with pH=14 to form an electrolytic cell system.

[0117] pass Figure 12 It can be seen that after 200 hours of continuous operation, the composite electrode material CAM@NC / CP-900 showed good stability and anti-interference ability, and the catalytic performance was not affected.

[0118] Experiment 5: Three-electrode OER reaction stability test of the self-supporting CAM@NC / CP-900 electrode in alkaline seawater at pH = 14 (e.g. Figure 13 shown).

[0119] An electrolytic cell system is composed of composite electrode material CAM@NC / CP-900, graphite electrode, silver / silver chloride electrode and alkaline seawater with pH=14.

[0120] pass Figure 13 It can be seen that after 100 hours of continuous operation, the composite electrode material CAM@NC / CP-900 can still maintain half of its catalytic activity, and has certain stability and anti-interference ability.

[0121] Experiment 6: Stability test of the two electrodes of the self-supporting CAM@NC / CP-900 electrode in alkaline seawater with pH = 14 (e.g. Figure 14 shown).

[0122] The composite electrode material CAM@NC / CP-900 was used as the cathode and anode of the reaction, and an electrolytic cell system was formed with alkaline seawater with a pH of 14.

[0123] pass Figure 14 It can be seen that after 150 hours of continuous operation, the composite electrode material CAM@NC / CP-900 can still maintain half of its catalytic activity, and has certain stability and anti-interference ability.

[0124] It's worth noting that the alkaline seawater with a pH of 14 in Experiments 4-6 was prepared by adding KOH to natural seawater to adjust the pH to 14. This step causes the calcium and magnesium ions in the natural seawater to form hydroxide precipitates, resulting in a low residual calcium and magnesium ion content. After Experiments 4-6, no calcium or magnesium hydroxides adhered to the electrode material surfaces.

Claims

1. A self-supporting cobalt sulfide electrode, characterized in that: CoS was synthesized by melamine formaldehyde-polyethyleneimine resin x The nanoparticles are compounded with activated carbon fiber paper and then annealed at high temperature to obtain the product.

2. A self-supporting cobalt sulfide electrode according to claim 1, characterized in that: The CoS x The preparation method of nanoparticles is as follows: adding cobalt nitrate hexahydrate and thioacetamide to a mixed solution of water and dimethylformamide, stirring until the materials are dissolved and then fully reacting under certain conditions, and then centrifuging, washing and drying to obtain CoS x Nanoparticles.

3. A self-supporting cobalt sulfide electrode according to claim 2, characterized in that: The mass ratio of cobalt nitrate hexahydrate to thioacetamide is (0.2-2):(1-4); the temperature for fully reacting cobalt nitrate hexahydrate and thioacetamide is 160-220° C., and the time for fully reacting is 12-48 hours.

4. The method for preparing a self-supporting cobalt sulfide electrode according to any one of claims 1 to 3, characterized in that: First, melamine formaldehyde-polyethyleneimine resin and CoS x The nanoparticles are mixed evenly and then applied to both sides of activated carbon fiber paper. Finally, a self-supporting cobalt sulfide electrode is obtained after drying and high-temperature annealing.

5. A self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode, characterized in that: CoS was synthesized by melamine formaldehyde-polyethyleneimine resin x @MoS2 nanoparticles are compounded with activated carbon fiber paper and then annealed at high temperature.

6. The self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode according to claim 5, characterized in that: The CoS x The preparation method of @MoS2 nanoparticles is as follows: A. Add cobalt nitrate hexahydrate and thioacetamide to a mixed solution of water and dimethylformamide, stir until the materials are dissolved, and then react fully at a certain temperature. After centrifugation, washing and drying, CoS x Nanoparticles; B. Dissolve glucose in water and stir thoroughly until dissolved, then add CoS x Nanoparticles, sodium molybdate dihydrate and thiourea are fully mixed and reacted under certain conditions, and then centrifuged, washed and dried to obtain CoS x @MoS2 nanoparticles.

7. The method for preparing a self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode according to claim 6, characterized in that: CoS x The mass ratio of nanoparticles, sodium molybdate dihydrate and thiourea is (30-100): (0.1-1): (0.1~1); CoS x The temperature for fully reacting the nanoparticles, sodium molybdate dihydrate and thiourea is 160-220° C., and the time for fully reacting the nanoparticles is 12-48 hours.

8. The method for preparing a self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode according to any one of claims 5 to 7, characterized in that: Melamine formaldehyde-polyethyleneimine resin and CoS x The @MoS2 nanoparticles are mixed evenly and then coated on both sides of activated carbon fiber paper. Finally, after drying and high-temperature annealing, a self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode is obtained.

9. Use of the self-supporting cobalt sulfide electrode according to any one of claims 1 to 3 in seawater electrolysis, characterized in that: The self-supporting cobalt sulfide electrode is used as a cathode material in a seawater electrolysis cell.

10. Use of the self-supporting cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrode according to any one of claims 5 to 7 in seawater electrolysis, characterized in that: Self-supported cobalt sulfide-molybdenum disulfide bifunctional heterojunction electrodes as cathode and anode materials in seawater electrolysis cells.

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