A carbonate-doped, highly active electrocatalytic material for the total hydrolysis of seawater, its preparation method and application

Abstract

This invention provides a carbonate-doped, highly active electrocatalyst for the complete hydrolysis of seawater, its preparation method, and its application. The preparation method includes the following steps: placing a pretreated nickel foam (NF) current collector in a cobalt source aqueous solution for a hydrothermal reaction; after the reaction, cooling, washing, and drying to obtain a Co3O4 / NF precursor composite material; placing the obtained Co3O4 / NF precursor composite material in a mixed solution containing a cobalt source, a molybdenum source, urea, and sodium citrate for a hydrothermal reaction; after the reaction, cooling, washing, and drying to obtain the final product. This invention uses three-dimensional metallic nickel foam as the current collector and prepares a stable electrocatalyst for the complete hydrolysis of seawater with both high activity and chlorine corrosion resistance through a two-step mild hydrothermal reaction. The prepared composite catalyst can drive the complete hydrolysis of seawater for a long period of stable operation at a relatively low potential.

Description

Technical Field

[0001] This invention relates to a carbonate-doped, highly active electrocatalytic material for the complete decomposition of seawater, its preparation method, and its application, belonging to the field of electrocatalytic materials. Background Technology

[0002] The overexploitation and use of fossil fuels has led to a severe energy crisis. While these non-renewable energy sources provide energy for humanity, they inevitably emit large amounts of carbon dioxide, sulfur dioxide, and other gases, contributing to the greenhouse effect and environmental pollution, which is inconsistent with the goals of sustainable development. Hydrogen energy, as a clean, green, and high-energy-density renewable energy source, produces no carbon emissions during combustion, with water as the sole byproduct, and is considered an ideal alternative to fossil fuels. Utilizing electricity generated from abundant renewable energy sources (solar, wind, tidal, etc.) to drive water splitting has become a promising hydrogen production technology, meeting numerous human demands for efficient, low-carbon, economical, and environmentally friendly emerging renewable energy sources.

[0003] In recent decades, hydrogen production technology through water electrolysis has developed rapidly. The electrolyte used in this process primarily comes from freshwater (high-quality pure water or purified deionized water). However, since freshwater accounts for less than 3% of global water resources and is largely covered by glaciers and snow-capped mountains, its large-scale application in water electrolysis is limited. Furthermore, the production of pure / deionized water often requires complex purification processes and additional costs, and generates large amounts of wastewater, which does not meet economic and environmental development requirements. In contrast, seawater resources are abundant, accounting for approximately 96.5% of global water resources, and are virtually inexhaustible. Therefore, direct electrocatalytic decomposition of seawater to produce hydrogen is more economical and feasible, especially for coastal areas rich in renewable resources. Fully utilizing abundant renewable energy sources for efficient and stable electrolysis of seawater to produce hydrogen is of great significance for reducing environmental pollution, optimizing energy structure, alleviating freshwater shortages, and producing high-value-added products.

[0004] However, due to the complex composition of seawater, it contains a variety of ions (mainly Na+). + and Cl - In addition to the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode, the electrolytic oxidation of chloride ions (ClOR) also occurs during seawater electrolysis. The ClOR side reaction generates various toxic, environmentally polluting, and corrosive chlorine-containing byproducts, leading to damage to the catalyst, electrodes, and electrolyzer components, thus affecting the lifespan of the electrocatalyst and becoming a key factor limiting hydrogen production from seawater electrolysis. Therefore, developing a highly active seawater electrocatalyst with high efficiency and resistance to chlorine corrosion is crucial for improving the efficiency and lifespan of seawater electrolysis.

[0005] Although researchers have attempted to prepare various seawater electrocatalysts and made significant improvements in enhancing chlorine resistance, they still fall short of industrial standards. Furthermore, research often focuses on single half-reactions (OER or HER), making it difficult to directly use them as dual electrodes for the complete hydrolysis of seawater. This further limits the practical application of catalysts in the complete hydrolysis of seawater. Therefore, the preparation of highly active electrocatalysts for the complete hydrolysis of seawater using simple and economical methods still requires further exploration. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a carbonate-doped, highly active electrocatalyst for the complete decomposition of seawater, its preparation method, and its applications. Using three-dimensional nickel foam as the current collector, this invention prepares a stable electrocatalyst for the complete decomposition of seawater through a two-step, mild hydrothermal reaction. This composite catalyst possesses both high activity and resistance to chlorine corrosion. The prepared catalyst can drive the complete decomposition of seawater to operate stably for extended periods at relatively low potentials.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a carbonate-doped, highly active electrocatalytic material for the complete decomposition of seawater includes the following steps:

[0009] (1) The pretreated nickel foam (NF) current collector was placed in a cobalt source aqueous solution for hydrothermal reaction; after the reaction was completed, it was cooled, washed and dried to obtain the Co3O4 / NF precursor composite material.

[0010] (2) The Co3O4 / NF precursor composite material obtained in step (1) was placed in a mixed solution containing cobalt source, molybdenum source, urea and sodium citrate for hydrothermal reaction; after the reaction was completed, it was cooled, washed and dried to obtain CO3. 2- -CoMoO4 / Co3O4 / NF heterocomposite material, namely carbonate-doped high-activity electrocatalytic material for the complete decomposition of seawater.

[0011] According to a preferred embodiment of the present invention, the pretreatment step in step (1) is as follows: the nickel foam current collector is ultrasonically treated in 1 mol / L HCl solution, deionized water and anhydrous ethanol for 30 min respectively, and then vacuum dried at 60°C for later use; the purpose of the pretreatment is to remove oxides and other impurities from the surface of the nickel foam.

[0012] According to a preferred embodiment of the present invention, the thickness of the nickel foam in step (1) is 1.5-2.0 mm.

[0013] According to a preferred embodiment of the present invention, the cobalt source in step (1) is Co(NO3)3·6H2O, and the concentration of the aqueous solution of the cobalt source is 0.02-0.03 mol / L.

[0014] According to the present invention, the volume of the cobalt source aqueous solution in step (1) is sufficient to completely submerge the foamed nickel current collector.

[0015] According to a preferred embodiment of the present invention, the temperature of the hydrothermal reaction in step (1) is 150-180°C and the hydrothermal reaction time is 10-12h.

[0016] According to a preferred embodiment of the present invention, the washing in step (1) is to rinse 3-5 times with deionized water, and the drying is to dry at 60-70°C for 6-8 hours.

[0017] According to a preferred embodiment of the present invention, the cobalt source in step (2) is Co(NO3)3·6H2O, and the molybdenum source is Na2MoO4·2H2O.

[0018] According to a preferred embodiment of the present invention, the concentration of the cobalt source in the mixed solution in step (2) is 0.04-0.06 mol / L.

[0019] According to a preferred embodiment of the present invention, in the mixed solution described in step (2), the molar ratio of molybdenum source to cobalt source is 1:1, the molar ratio of urea to cobalt source is 0.75-1.25:1, and the molar ratio of sodium citrate to cobalt source is 0.2-0.3:1.

[0020] According to the present invention, the volume of the mixed solution in step (2) is sufficient to completely submerge the Co3O4 / NF precursor composite material.

[0021] According to a preferred embodiment of the present invention, the temperature of the hydrothermal reaction in step (2) is 120-140°C, and the time of the hydrothermal reaction is 8-10 hours.

[0022] According to a preferred embodiment of the present invention, the washing in step (2) is to rinse 3-5 times with deionized water, and the drying is to dry at 60-70°C for 6-8 hours.

[0023] This invention also provides a carbonate-doped, highly active electrocatalytic material for the complete decomposition of seawater prepared by the above method. The electrocatalytic material comprises a nickel foam (NF) current collector and a heterogeneous composite material CO3 grown in situ on the nickel foam (NF) current collector. 2- -CoMoO4 / Co3O4; the heterogeneous composite material CO3 2- -The microstructure of CoMoO4 / Co3O4 is a combination of carbonate-doped hydrangea-shaped CoMoO4 nanoflowers and Co3O4 nanoparticles.

[0024] According to the present invention, the above-mentioned carbonate-doped highly active seawater electrocatalytic material is used as a seawater electrocatalyst for the electrocatalytic decomposition of seawater.

[0025] The technical features and beneficial effects of this invention are as follows:

[0026] 1. The carbonate-doped high-activity seawater electrocatalyst of this invention uses inexpensive and readily available raw materials, and has a simple synthesis route. Only two mild hydrothermal reactions are required to prepare a high-activity seawater electrocatalyst with a heterostructure. In the preparation method of this invention, it is crucial to control the concentration of urea. Too low a concentration will result in insufficient carbonate doping, affecting the catalyst's activity and the full expression of its chlorine resistance. Too high a concentration will introduce excessive carbonate, forming partial carbonates, hindering the full expression of active sites and reducing the catalytic performance of seawater electrolysis. Furthermore, the preparation process of this invention is simple, energy-efficient, and requires minimal equipment. The prepared CO3... 2- -CoMoO4 / Co3O4 / NF heterocomposite materials exhibit excellent seawater decomposition performance, providing a feasible solution for the practical industrial application of seawater decomposition.

[0027] 2. The carbonate-doped, highly active electrocatalyst for the complete decomposition of seawater, CO3, obtained in this invention 2- -CoMoO4 / Co3O4 / NF possesses a unique hydrangea-like structure, which effectively increases the specific surface area of ​​the catalyst, exposing more active sites. Furthermore, the open structure of the hydrangea-like nanoflower facilitates mass transfer and the migration of gaseous products. In addition, the carbonate ion, as an anionic group with high charge loading, can effectively regulate the charge distribution of the catalytic active centers, and through strong electrostatic repulsion with chloride ions, effectively resists the contact and damage of chloride ions to the catalyst material. Moreover, the formation of a heterojunction between CoMoO4 and Co3O4 improves the tight contact between the catalyst interfaces, enhancing the charge transfer efficiency and structural stability of the catalyst. Through the synergistic effect of carbonate doping and the heterostructure, this electrocatalytic material effectively improves the activity and stability of the catalyst during seawater electrolysis. When electrolyzing real seawater to release hydrogen, an overpotential of only 101 mV is required to achieve 10 mA / cm². 2 The current density, when fully analyzing real seawater, requires only 1.86V to reach 100mA / cm. 2 It can achieve high current density and maintain stable operation for more than 30 hours with almost no performance degradation; it can even reach the industrial requirement of 0.5A / cm² with only 2.18V. 2 The current density.

[0028] 3. The carbonate-doped, highly active seawater electrocatalyst prepared in this invention is an in-situ grown, self-supporting heterostructure composite material. During the electrocatalytic cracking of seawater, it can be directly used as a dual-electrode driven reaction, eliminating the need to coat the catalyst onto an additional conductive current collector. This simplifies the preparation process and avoids problems such as decreased conductivity and catalyst detachment under high current conditions caused by the introduction of binders like Nafion, ensuring high conductivity and durability of the catalyst. This invention provides a new synthetic approach and direction for the rational use of mild hydrothermal synthesis technology to prepare in-situ grown, anion-doped, highly active seawater electrocatalysts through a simple and easy preparation process. Attached Figure Description

[0029] Figure 1 CO3 prepared in Example 1 2- - X-ray diffraction (XRD) pattern of the CoMoO4 / Co3O4 / NF electrocatalytic material.

[0030] Figure 2 CO3 prepared in Example 1 2- - Raman spectrum of CoMoO4 / Co3O4 / NF electrocatalytic material.

[0031] Figure 3 CO3 prepared in Example 1 2- - Scanning electron microscope (SEM) image of the CoMoO4 / Co3O4 / NF electrocatalytic material.

[0032] Figure 4 CO3 prepared in Example 1 2- - Elemental mapping diagram of CoMoO4 / Co3O4 / NF electrocatalytic materials.

[0033] Figure 5 CO3 prepared in Example 1 2- - Polarization curves (LSV) of the CoMoO4 / Co3O4 / NF electrocatalytic material and the electrocatalytic materials prepared in Comparative Examples 1-6 in simulated seawater.

[0034] Figure 6 CO3 prepared in Example 1 2- - Polarization curves (LSV) of the CoMoO4 / Co3O4 / NF electrocatalytic materials and the electrocatalytic materials prepared in Comparative Examples 1-6 in simulated seawater.

[0035] Figure 7 CO3 prepared in Examples 1-5 2-- Polarization curve (LSV) of the CoMoO4 / Co3O4 / NF electrocatalytic material in simulated seawater.

[0036] Figure 8 CO3 prepared in Examples 1-5 2- - Polarization curve (LSV) of the CoMoO4 / Co3O4 / NF electrocatalytic material in simulated seawater.

[0037] Figure 9 CO3 prepared in Example 1 2- - Polarization curve (LSV) of the CoMoO4 / Co3O4 / NF electrocatalytic material in real seawater.

[0038] Figure 10 CO3 prepared in Example 1 2- - Polarization curve (LSV) of CoMoO4 / Co3O4 / NF electrocatalytic material in real seawater electrocatalytic total decomposition performance test.

[0039] Figure 11 CO3 prepared in Example 1 2- - Long-term stability test results of CoMoO4 / Co3O4 / NF electrocatalytic material under constant potential in real seawater electrolysis.

[0040] Figure 12 The image shows a scanning electron microscope (SEM) image of the electrocatalytic material prepared for Comparative Example 4.

[0041] Figure 13 The image shows a scanning electron microscope (SEM) image of the electrocatalytic material prepared for Comparative Example 5.

[0042] Figure 14 The image shows a scanning electron microscope (SEM) image of the electrocatalytic material prepared for Comparative Example 6. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific examples, but the scope of protection of the present invention is not limited thereto.

[0044] Reagents and instruments: All reagents used in this invention are of analytical grade and were used directly after purchase without further purification.

[0045] Cobalt nitrate hexahydrate (Co(NO3)3·6H2O), sodium molybdate dihydrate (Na2MoO4·2H2O), sodium citrate (C6H5Na3O7), urea (CH4N2O), sodium chloride (NaCl), potassium hydroxide (KOH), hydrochloric acid (HCl 36.0-38.0%), and anhydrous ethanol (C2H6O) are available from Guoyao.

[0046] The nickel foam (NF) was purchased from Lizhiyuan Battery Sales Department in Yingze District, Taiyuan City, and its thickness is 1.5mm.

[0047] Electronic balance (LA203E / A), electric thermostatic drying oven (Jinghong), magnetic stirrer (85-1 type), electrochemical workstation (Jiangsu Donghua, DH7001B).

[0048] Electrochemical testing: Electrochemical testing was conducted using the Jiangsu Donghua DH7001B electrochemical workstation. A three-electrode testing system was used, with the cut electrode material used directly as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum sheet (1cm×1cm) electrode as the counter electrode. The simulated seawater electrolyte was a freshly prepared 1mol / L KOH + 0.5mol / L NaCl mixed solution, while the real seawater electrolyte was seawater from the Qingdao sea area. Unless otherwise mentioned, all test data were 90% IR compensated.

[0049] Example 1

[0050] A method for preparing a carbonate-doped, highly active electrocatalytic material for the complete decomposition of seawater includes the following steps:

[0051] (1) Cut the nickel foam into 2cm×3cm pieces. The cut nickel foam was ultrasonically cleaned for 30min in 1mol / L HCl solution, deionized water and anhydrous ethanol respectively to remove oxides and other impurities on the surface of the nickel foam. It was then vacuum dried at 60℃ for subsequent use. 1.0mmol of Co(NO3)3·6H2O was dissolved in 40mL of deionized water under stirring. The resulting Co(NO3)3 solution was transferred to a 50mL polytetrafluoroethylene liner. The pretreated nickel foam was then inserted into the Co(NO3)3 solution. The liner was sealed and transferred to a stainless steel reactor. The reactor was then sealed. The reaction was carried out at 160℃ for 10h in an electric thermostatic oven and then naturally cooled to room temperature. The reactor was removed and the product was rinsed three times with deionized water and dried at 60℃ for 8h to obtain the Co3O4 / NF precursor composite material.

[0052] (2) Dissolve 2.0 mmol of Co(NO3)3·6H2O, 2.0 mmol of Na2MoO4·2H2O, 2.0 mmol of urea, and 0.5 mmol of sodium citrate in 40 mL of deionized water under stirring. Transfer the resulting homogeneous mixture to a 50 mL polytetrafluoroethylene liner. Insert the Co3O4 / NF precursor composite material obtained in step (1) into the above mixture. Seal the liner and transfer it to a stainless steel reactor. Seal the reactor. React at 120 °C for 8 h in an electrically heated constant temperature oven. After natural cooling to room temperature, remove the reactor. Rinse the resulting product three times with deionized water and dry at 60 °C for 8 h to obtain CO3. 2- -CoMoO4 / Co3O4 / NF heterocomposite material, namely carbonate-doped high-activity electrocatalytic material for the complete decomposition of seawater.

[0053] The CO3 prepared in this embodiment 2- The XRD pattern of the CoMoO4 / Co3O4 / NF composite material is as follows: Figure 1 As shown, from Figure 1 As can be seen, the composite material mainly consists of three phases: NF, Co3O4, and CoMoO4. No carbonate was found, indicating that carbonate ions are uniformly doped throughout the catalyst. Optical characterization of the carbonate ions yielded CO3... 2- The Raman spectrum of the CoMoO4 / Co3O4 / NF composite material is shown below. Figure 2 As shown, in the range of 600-800cm -1 There is obvious CO3 present. 2- The characteristic peaks indicate successful carbonate doping, i.e., CO32-. 2- Successful construction of the CoMoO4 / Co3O4 / NF composite material. SEM image of the material in Example 1 is shown below. Figure 3 As shown, the morphology of the sample is a combination of hydrangea-shaped nanoflowers and nanoparticles (circled), indicating the successful construction of the heterostructure. The nanoparticles are relatively small, with a size of 60-100 nm, while the hydrangea-shaped CoMoO4 nanoflowers are composed of interlaced nanosheets. The diameter of the nanoflowers is 3 ± 0.5 μm, and the thickness of the nanosheets is 10-15 nm. This unique hydrangea-shaped structure increases the specific surface area of ​​the catalyst, facilitating the exposure of more active sites. Simultaneously, the open structure promotes mass transfer and gas transport, accelerating the reaction process. The obtained CO3... 2- The elemental mapping spectra of the CoMoO4 / Co3O4 / NF composite material are as follows: Figure 4 As shown in the figure, it can be clearly seen that the four elements are evenly distributed throughout the hydrangea-like structure, further indicating that carbonate ions are uniformly doped into the entire material.

[0054] The CO3 prepared in this embodiment 2- - The CoMoO4 / Co3O4 / NF composite material was directly used as an electrode in simulated and real seawater electrolysis performance testing. The specific steps are as follows:

[0055] Electrochemical performance testing was conducted using a Jiangsu Donghua DH7001B electrochemical workstation. A three-electrode testing system was used, with the prepared electrocatalyst serving as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet (1cm×1cm) electrode as the counter electrode. The simulated seawater electrolyte was a freshly prepared 1mol / L KOH + 0.5mol / L NaCl mixed solution, while the real seawater electrolyte was seawater from the Qingdao sea area. All test data underwent 90% IR compensation, and all potentials were converted to reversible hydrogen potentials.

[0056] The CO3 prepared in this embodiment 2- The hydrogen evolution performance of the CoMoO4 / Co3O4 / NF composite material was tested in simulated seawater (1 mol / L KOH + 0.5 mol / L NaCl) solution at a linear scan rate of 5 mV / s. Figure 5 ) and oxygen evolution performance test ( Figure 6 As shown in the figure, the electrocatalytic material prepared in this embodiment achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is only 219 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The required overpotential of only 310 mV for the current density is significantly better than that of Comparative Examples 1-6 and Examples 2-5, as well as most reported oxide electrocatalysts, indicating that this material has excellent seawater electrolysis performance. Based on this, it was further tested by direct electrolysis of real seawater, and it was found that the material can achieve 10 mA / cm² at an overpotential of only 101 mV when testing the hydrogen production performance of real seawater electrolysis. 2 current density ( Figure 9 When analyzing real seawater, a potential of only 1.86V is required to achieve 100mA / cm. 2 current density ( Figure 10 It can maintain a stable response for more than 30 hours with almost no performance degradation. Figure 11 It can even achieve the industrial requirement of 0.5A / cm with only a potential of 2.18V. 2 current density ( Figure 10 The above results all demonstrate that the material of Example 1 has excellent seawater decomposition performance.

[0057] Example 2

[0058] A method for preparing a carbonate-doped, highly active electrocatalytic seawater decomposition material is described in Example 1, except that the amount of urea added in step (2) is 1.5 mmol.

[0059] The electrocatalytic material prepared in this embodiment was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0060] The electrocatalytic material prepared in this embodiment achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 264 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The required current density is 363mV overpotential. In this example, the overpotential values ​​of hydrogen evolution and oxygen evolution reactions of the catalyst electrolysis of seawater are higher than those in Example 1, indicating that the catalytic performance of this example is slightly lower than that of Example 1.

[0061] Example 3

[0062] A method for preparing a carbonate-doped, highly active electrocatalytic seawater decomposition material is described in Example 1, except that the amount of urea added in step (2) is 1.75 mmol.

[0063] The electrocatalytic material prepared in this embodiment was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0064] The electrocatalytic material prepared in this embodiment achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 239 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The required current density is 360mV overpotential. In this embodiment, the overpotential values ​​for hydrogen evolution and oxygen evolution reactions are higher than those in Example 1, indicating that the catalytic performance of this embodiment is slightly lower than that of Example 1.

[0065] Example 4

[0066] The preparation method of a carbonate-doped, highly active, total seawater electrocatalytic material is as described in Example 1, except that the amount of urea added in step (2) is 2.25 mmol.

[0067] The electrocatalytic material prepared in this embodiment was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0068] The electrocatalytic material prepared in this embodiment achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2The required current density is 227 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The required current density is 347mV overpotential. In this embodiment, the overpotential values ​​for hydrogen evolution and oxygen evolution reactions are slightly higher than those in Example 1, indicating that the excessive introduction of carbonate ions will hinder the full expression of catalytic activity and reduce catalytic performance, making the catalytic performance of this embodiment slightly lower than that of Example 1.

[0069] Example 5

[0070] A method for preparing a carbonate-doped, highly active electrocatalytic seawater decomposition material is described in Example 1, except that the amount of urea added in step (2) is 2.5 mmol.

[0071] The electrocatalytic material prepared in this embodiment was applied to simulated seawater solution for electrocatalytic cracking of seawater. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0072] The electrocatalytic material prepared in this embodiment achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 248 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The required current density is 358 mV overpotential, which is higher than that of Example 1. This may be due to the introduction of too much carbonate, which further hinders the expression of catalytic activity, resulting in the catalytic performance of this example being lower than that of Example 1.

[0073] Comparative Example 1

[0074] Pretreated nickel foam was used directly as the electrocatalytic material for the complete decomposition of seawater. The pretreatment process was as described in Example 1.

[0075] The electrocatalytic material obtained in this comparative example was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0076] When the electrocatalytic material prepared in this comparative example was used in simulated seawater electrocatalytic decomposition tests, within the selected test voltage range, it failed to reach 100 mA / cm² for both hydrogen evolution reaction and oxygen evolution reaction tests. 2 The current density indicates that the electrocatalyst material in this comparative example exhibits very poor activity during the electrolysis reaction, and its electrocatalytic performance is far lower than that of the examples and comparative examples.

[0077] Comparative Example 2

[0078] A method for preparing a seawater electrocatalytic material for total hydrolysis includes the following steps:

[0079] Nickel foam was cut into 2cm × 3cm pieces. The cut nickel foam was then ultrasonically cleaned for 30 min each in 1 mol / L HCl solution, deionized water, and anhydrous ethanol for 30 min each, as a pretreatment to remove oxides and other impurities from the surface of the nickel foam. It was then vacuum dried at 60℃ for subsequent use. 1.0 mmol of Co(NO3)3·6H2O was dissolved in 40 mL of deionized water under stirring. The resulting Co(NO3)3 solution was transferred to a 50 mL polytetrafluoroethylene liner. The pretreated nickel foam was then inserted into the Co(NO3)3 solution. The liner was sealed and the solution was transferred to a stainless steel reactor and sealed. The reactor was then reacted at 160℃ for 10 h in an electrically heated constant-temperature oven, and then naturally cooled to room temperature. The reactor was removed, and the resulting product was rinsed three times with deionized water and dried at 60℃ for 8 h to obtain the Co3O4 / NF precursor composite material, which is the electrocatalytic material for the complete decomposition of seawater.

[0080] The electrocatalytic material obtained in this comparative example was applied to the electrocatalytic cracking of seawater in a simulated seawater solution, and the hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0081] The electrocatalytic material prepared in this comparative example achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 415 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The current density required an overpotential of 452 mV, and the overpotential values ​​were all significantly higher than those in Example 1, indicating that the catalytic performance of this comparative example was significantly lower than that of Example 1.

[0082] Comparative Example 3

[0083] A method for preparing a seawater electrocatalytic material for total hydrolysis includes the following steps:

[0084] (1) Cut nickel foam into 2cm×3cm pieces. The cut nickel foam was then ultrasonically cleaned for 30min each in 1mol / L HCl solution, deionized water, and anhydrous ethanol for 30min each, pre-treating to remove oxides and other impurities from the surface of the nickel foam. It was then vacuum-dried at 60℃ for subsequent use. 2.0mmol of Co(NO3)3·6H2O and 2.0mmol of Na2MoO4·2H2O were dissolved in 40mL of deionized water under stirring. The resulting homogeneous solution was transferred to a 50mL polytetrafluoroethylene (PTFE) liner. The pre-treated nickel foam was inserted into the solution, and the liner was sealed before being transferred to a stainless steel reactor. The reactor was then sealed. The reaction was carried out at 120℃ for 8h in an electrically heated constant-temperature oven, followed by natural cooling to room temperature. Finally, the reactor was removed, and the resulting product was rinsed three times with deionized water and dried at 60℃ for 8h to obtain the CoMoO4 / NF composite material, which is the electrocatalytic material for the complete decomposition of seawater.

[0085] The electrocatalytic material obtained in this comparative example was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0086] The electrocatalytic material prepared in this comparative example achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 442 mV overpotential; during the electrocatalytic oxygen evolution reaction test, it reached 100 mA / cm². 2 The current density required an overpotential of 415 mV, and the overpotential values ​​were all significantly higher than those in Example 1, indicating that the catalytic performance of this comparative example was lower than that of Example 1.

[0087] Comparative Example 4

[0088] A method for preparing a seawater electrocatalytic material for total hydrolysis includes the following steps:

[0089] (1) Cut the nickel foam into 2cm×3cm pieces. The cut nickel foam was ultrasonically cleaned for 30min in 1mol / L HCl solution, deionized water and anhydrous ethanol respectively to remove oxides and other impurities on the surface of the nickel foam. It was then vacuum dried at 60℃ for subsequent use. 1.0mmol of Co(NO3)3·6H2O was dissolved in 40mL of deionized water under stirring. The resulting Co(NO3)3 solution was transferred to a 50mL polytetrafluoroethylene liner. The pretreated nickel foam was then inserted into the Co(NO3)3 solution. The liner was sealed and transferred to a stainless steel reactor. The reactor was then sealed. The reaction was carried out at 160℃ for 10h in an electric thermostatic oven and then naturally cooled to room temperature. The reactor was removed and the product was rinsed three times with deionized water and dried at 60℃ for 8h to obtain the Co3O4 / NF precursor composite material.

[0090] (2) Dissolve 2.0 mmol of Co(NO3)3·6H2O and 2.0 mmol of Na2MoO4·2H2O in 40 mL of deionized water under stirring. Transfer the resulting homogeneous mixture to a 50 mL polytetrafluoroethylene liner. Insert the Co3O4 / NF precursor composite material obtained in step (1) into the above mixture. Seal the liner and transfer it to a stainless steel reactor. Seal the reactor. React at 120°C for 8 h in an electrically heated constant temperature oven. Allow it to cool naturally to room temperature. Finally, remove the reactor, rinse the resulting product three times with deionized water, and dry it at 60°C for 8 h to obtain the CoMoO4 / Co3O4 / NF composite material, which is the seawater electrocatalytic material.

[0091] The electrocatalytic material obtained in this comparative example was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0092] The SEM image of this comparative sample is shown below. Figure 12 As shown, the sample exhibits a nanorod-like structure with a length of 8-10 μm and a width of 300-400 nm. This structure can increase the exposed active surface area to some extent. The electrocatalytic material prepared in this comparative example achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 354 mV overpotential; during the electrocatalytic oxygen evolution reaction test, it reached 100 mA / cm². 2 The current density required an overpotential of 391 mV, and the overpotential values ​​were all higher than those in Example 1, indicating that the catalytic performance of this comparative example was lower than that of Example 1.

[0093] Comparative Example 5

[0094] A method for preparing a carbonate-doped electrocatalytic material for the complete decomposition of seawater includes the following steps:

[0095] (1) Cut the nickel foam into 2cm×3cm pieces. The cut nickel foam was ultrasonically cleaned for 30min in 1mol / L HCl solution, deionized water and anhydrous ethanol respectively to remove oxides and other impurities on the surface of the nickel foam. It was then vacuum dried at 60℃ for subsequent use. 1.0mmol of Co(NO3)3·6H2O was dissolved in 40mL of deionized water under stirring. The resulting Co(NO3)3 solution was transferred to a 50mL polytetrafluoroethylene liner. The pretreated nickel foam was then inserted into the Co(NO3)3 solution. The liner was sealed and transferred to a stainless steel reactor. The reactor was then sealed. The reaction was carried out at 160℃ for 10h in an electric thermostatic oven and then naturally cooled to room temperature. The reactor was removed and the product was rinsed three times with deionized water and dried at 60℃ for 8h to obtain the Co3O4 / NF precursor composite material.

[0096] (2) Dissolve 2.0 mmol of urea and 0.5 mmol of sodium citrate in 40 mL of deionized water under stirring. Transfer the resulting homogeneous solution to a 50 mL polytetrafluoroethylene liner. Insert the Co3O4 / NF precursor composite material obtained in step (1) into the above solution. Seal the liner and transfer it to a stainless steel reactor. Seal the reactor. React at 120°C for 8 h in an electrically heated constant temperature oven. Allow it to cool naturally to room temperature. Finally, remove the reactor, rinse the resulting product three times with deionized water, and dry it at 60°C for 8 h to obtain CO3. 2- -Co3O4 / NF composite material is a carbonate-doped electrocatalytic material for the complete decomposition of seawater.

[0097] The electrocatalytic material obtained in this comparative example was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0098] The SEM image of this comparative sample is shown below. Figure 13 As shown, the sample exhibits a nanoparticle structure with a size of 80-100 nm. The formation of nanoparticles increases the surface roughness of the current collector, thereby enhancing its catalytic performance to some extent. The electrocatalytic material prepared in this comparative example achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 395 mV overpotential; when testing the electrocatalytic oxygen evolution reaction, it reaches 100 mA / cm². 2 The current density required an overpotential of 465mV, and the overpotential values ​​were all significantly higher than those in Example 1, indicating that the catalytic performance of this comparative example was far lower than that of Example 1.

[0099] Comparative Example 6

[0100] A method for preparing a carbonate-doped electrocatalytic material for the complete decomposition of seawater includes the following steps:

[0101] (1) Cut nickel foam into 2cm×3cm pieces. The cut nickel foam was then ultrasonically cleaned for 30min each in 1mol / L HCl solution, deionized water, and anhydrous ethanol for 30min each, pre-treating to remove oxides and other impurities from the surface of the nickel foam. It was then vacuum-dried at 60℃ for later use. 2.0mmol of Co(NO3)3·6H2O, 2.0mmol of Na2MoO4·2H2O, 2.0mmol of urea, and 0.5mmol of sodium citrate were dissolved in 40mL of deionized water under stirring. The resulting homogeneous mixture was transferred to a 50mL polytetrafluoroethylene liner. The pre-treated nickel foam was then inserted into the mixture. The liner was sealed, and the mixture was transferred to a stainless steel reactor and sealed. The reactor was reacted at 120℃ for 8h in an electrically heated constant-temperature oven, then naturally cooled to room temperature. Finally, the reactor was removed, and the resulting product was rinsed three times with deionized water and dried at 60℃ for 8h to obtain CO3. 2- -CoMoO4 / NF composite material is a carbonate-doped electrocatalytic material for the complete decomposition of seawater.

[0102] The electrocatalytic material prepared in this comparative example was applied to the electrocatalytic cracking of seawater in a simulated seawater solution. The hydrogen evolution performance and oxygen evolution performance were tested as described in Example 1.

[0103] The SEM image of this comparative sample is shown below. Figure 14 As shown, the morphology of the sample is a hydrangea-like nanoflower structure, similar to that of Example 1, with the diameter of the hydrangea-like CoMoO4 nanoflowers being 3±1 μm. The electrocatalytic material prepared in this comparative example achieved an efficiency of 100 mA / cm² during the electrocatalytic hydrogen evolution reaction test. 2 The required current density is 404 mV overpotential; during the electrocatalytic oxygen evolution reaction test, it reached 100 mA / cm². 2 The required current density is 418mV overpotential, and the overpotential values ​​are all higher than those in Example 1, indicating that the catalytic performance of this example is lower than that of Example 1.

Claims

1. A method for preparing a carbonate-doped, highly active electrocatalytic material for the complete decomposition of seawater, comprising the following steps: (1) The pretreated nickel foam NF current collector is placed in a cobalt source aqueous solution for hydrothermal reaction; after the reaction is completed, it is cooled, washed and dried to obtain Co3O4 / NF precursor composite material; the cobalt source is Co(NO3)3·6H2O, and the concentration of the cobalt source aqueous solution is 0.02-0.03mol / L; the temperature of the hydrothermal reaction is 150-180℃, and the hydrothermal reaction time is 10-12h; (2) The Co3O4 / NF precursor composite material obtained in step (1) was placed in a mixed solution containing cobalt source, molybdenum source, urea and sodium citrate for hydrothermal reaction; after the reaction was completed, it was cooled, washed and dried to obtain CO3. 2- -CoMoO4 / Co3O4 / NF heterocomposite material, namely carbonate-doped highly active electrocatalytic material for the complete decomposition of seawater; the concentration of cobalt source in the mixed solution is 0.04-0.06 mol / L; the molar ratio of molybdenum source to cobalt source in the mixed solution is 1:1, the molar ratio of urea to cobalt source is 0.75-1.25:1, and the molar ratio of sodium citrate to cobalt source is 0.2-0.3:1; the hydrothermal reaction temperature is 120-140℃, and the hydrothermal reaction time is 8-10 h.

2. The preparation method of the carbonate-doped, highly active, total seawater electrocatalytic material according to claim 1, characterized in that, The pretreatment step in step (1) is as follows: the nickel foam current collector is ultrasonically treated in 1 mol / L HCl solution, deionized water and anhydrous ethanol for 30 min respectively, and then vacuum dried at 60℃ for later use; the thickness of the nickel foam is 1.5-2.0 mm.

3. The method for preparing the carbonate-doped, highly active, total seawater electrocatalytic material according to claim 1, characterized in that, The washing in step (1) involves rinsing with deionized water 3-5 times, and the drying involves drying at 60-70℃ for 6-8 hours.

4. The method for preparing the carbonate-doped, highly active electrocatalytic seawater decomposition material according to claim 1, characterized in that, The cobalt source mentioned in step (2) is Co(NO3)3·6H2O, and the molybdenum source is Na2MoO4·2H2O.

5. The method for preparing the carbonate-doped, highly active, total seawater electrocatalytic material according to claim 1, characterized in that, The washing in step (2) involves rinsing with deionized water 3-5 times, and the drying involves drying at 60-70℃ for 6-8 hours.

6. A carbonate-doped, highly active electrocatalytic seawater electrolysis material prepared by the preparation method according to any one of claims 1-5, characterized in that, The electrocatalytic material includes a nickel foam current collector and a heterogeneous composite material CO3 grown in situ on the nickel foam current collector. 2- -CoMoO4 / Co3O4; the heterogeneous composite material CO3 2- -The microstructure of CoMoO4 / Co3O4 is a combination of carbonate-doped hydrangea-shaped CoMoO4 nanoflowers and Co3O4 nanoparticles.

7. The application of the carbonate-doped, highly active, total seawater electrocatalytic material according to claim 6, characterized in that, It is used as an electrocatalyst for the electrocatalytic complete hydrolysis of seawater.

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