Method and application of dual-site MOF-based catalyst electrocatalytic overall seawater splitting

Abstract

The application provides a method for electrocatalytic complete seawater decomposition by a two-site MOF-based catalyst, comprising the following steps: pretreating foamed nickel, quickly adding an aqueous 2-methylimidazole solution into an aqueous cobalt nitrate hexahydrate solution and uniformly mixing to obtain a ZIF-L(Co) solution, putting the pretreated foamed nickel into the ZIF-L(Co) solution, stirring and reacting to obtain foamed nickel on which ZIF-L(Co) precursors grow; immersing the ZIF-L(Co) precursor foamed nickel obtained in step S1 into a sodium tungstate solution, taking out after etching, washing with water and drying to obtain foamed nickel to which a WO4 2‑ / Co(OH)2 intermediate is attached; putting the WO4 2‑ / Co(OH)2 intermediate foamed nickel obtained in step S2 and a phosphorus source into a tube furnace, carrying out high-temperature phosphorization in a protective atmosphere to obtain a two-site MOF-based catalyst; assembling a flow-type electrolytic cell, taking the two-site MOF-based catalyst obtained in step S3 as an anode and a cathode of the flow-type electrolytic cell at the same time, taking an alkaline seawater solution as an electrolyte and carrying out an electrocatalytic reaction.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis technology, and particularly relates to a method and application of electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst. Background Technology

[0002] Currently, water electrolysis for hydrogen production is one of the important ways to achieve the dual-carbon goal. The reaction process includes two key half-reactions: the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). However, the slow kinetics of water splitting greatly limit its industrial application. Therefore, electrocatalysts play a crucial role in energy conversion technology. Noble metal-based catalysts (such as Pt, RuO2, and IrO2) are often used as catalysts in the industrial production of water splitting, but their large-scale promotion is hindered by the limited reserves and high cost of these noble metals.

[0003] To address this issue, developing low-cost, high-efficiency transition metal-based OER and HER electrocatalysts is of significant research value and practical importance. In reality, due to the scarcity of freshwater resources, the abundance of seawater resources makes seawater electrolysis a promising prospect. Seawater electrolysis, like water splitting, mainly involves two half-reactions: the anodic OER and the cathodic HER. However, in the seawater environment, the high concentration of chloride ions, primarily from sodium chloride and potassium chloride, leads to the anodic side reaction, the chlorine evolution reaction (CER), and severe electrode corrosion. The OER is kinetically less reactive than the two-electron-based CER; therefore, the CER in seawater may compete with the anodic OER, reducing the overall efficiency of seawater electrolysis.

[0004] Among developed catalysts, transition metal phosphides have attracted widespread attention due to their high intrinsic activity. Phosphorus in metal phosphides has two functions: firstly, it acts as a basic site to capture protons, thereby promoting hydrogen adsorption; secondly, it modifies the electron density of surrounding (especially metal) atoms by donating electrons, thus adjusting its adsorption performance. Furthermore, by doping phosphides with other metals to form heterostructures, the electronic structure of the metal active sites can be more effectively tuned, thereby enhancing catalytic performance. Doping with Lewis acid layers can also promote OH-... - The adsorption of Cl can enhance mass transfer and achieve repulsion. - The presence of phosphate groups generated by P oxidation can further effectively prevent chlorine corrosion in seawater and extend the long-term stability of the catalyst. MOFs have advantages such as low cost, high specific surface area, and tunable pore size and structure, making them ideal materials or precursors for water splitting electrocatalysts.

[0005] To address the aforementioned technical problems, this invention presents a method and application for the electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst. Summary of the Invention

[0006] This invention provides a method and application for the electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst, aiming to solve the technical problems of high overpotential, poor stability, and poor resistance to seawater corrosion of existing transition metal catalysts. This invention uses ZIF-L with a large specific surface area as a sacrificial template, giving the catalyst more active sites. A flow electrolyzer is assembled, and the prepared electrocatalyst is used simultaneously as both the anode and cathode to carry out the electrocatalytic total hydrolysis of seawater in alkaline seawater, exhibiting high catalytic efficiency and stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for the electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst, comprising the following steps:

[0008] S1. Pre-treat the nickel foam by rapidly adding an aqueous solution of 2-methylimidazole to an aqueous solution of cobalt nitrate hexahydrate and mixing them evenly to obtain a ZIF-L(Co) solution. Place the pre-treated nickel foam into the ZIF-L(Co) solution, stir and react. After removing it, rinse off the unreacted ZIF-L(Co) residue and place it in a vacuum drying oven to dry, thus obtaining nickel foam with a ZIF-L(Co) precursor grown on it.

[0009] S2, deionized water and anhydrous ethanol are mixed to form a mixed solvent. Sodium tungstate is dissolved in the mixed solvent to obtain a sodium tungstate solution. The ZIF-L(Co) precursor nickel foam obtained in step S1 is immersed in the sodium tungstate solution, etched, removed, rinsed with water, and dried in a vacuum drying oven to obtain a product coated with WO4. 2- / Co(OH)2 intermediate foamed nickel;

[0010] S3, the WO4 obtained in step S2 2- / Co(OH)2 intermediate foamed nickel and phosphorus source are placed in a tube furnace and subjected to high-temperature phosphating in a protective atmosphere. After holding at the temperature for a period of time, the mixture is naturally cooled to room temperature to obtain a dual-site MOF-based catalyst.

[0011] S4. Assemble a flow electrolyzer. Use the dual-site MOF-based catalyst obtained in step S3 as both the anode and cathode of the flow electrolyzer. Use an alkaline seawater solution as the electrolyte. Apply voltage to the electrolyzer to carry out an electrocatalytic reaction. The anode undergoes an oxygen evolution reaction to produce oxygen, and the cathode undergoes a hydrogen evolution reaction to produce hydrogen.

[0012] Based on the above technical solution, the step S1 of pretreatment of nickel foam includes: placing the nickel foam in hydrochloric acid solution, deionized water and ethanol solution in sequence for ultrasonic treatment, and then placing it in a vacuum drying oven for drying to obtain pretreated nickel foam.

[0013] Based on the above technical solution, the size of the nickel foam is 30mm*20mm*1.6mm, and the concentration of the hydrochloric acid solution is 2-3 mol·L⁻¹. -1 The sonication time for hydrochloric acid is 15–20 min, for deionized water it is 10–15 min, and for ethanol solution it is 5–10 min.

[0014] Based on the above technical solution, in step S1, the concentration of the 2-methylimidazole aqueous solution is 0.4 mol·L⁻¹. -1 The concentration of the cobalt nitrate hexahydrate aqueous solution is 0.05 mol·L⁻¹. -1 The volume ratio of 2-methylimidazole aqueous solution and cobalt nitrate hexahydrate aqueous solution was 1:1, and the stirring reaction time was 3-4 hours.

[0015] Based on the above technical solution, in step S2, the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 4:1, and the concentration of sodium tungstate solution is 0.02 mol·L⁻¹. -1 The etching time is 10-15 minutes and the etching temperature is 85℃.

[0016] Based on the above technical solution, in step S3, the phosphorus source is sodium hypophosphite powder, the mass ratio of sodium hypophosphite is 0.3-0.4g, the sodium hypophosphite and the intermediate nickel foam are placed in two separate ceramic boats, with the sodium hypophosphite placed on the upstream side and the catalyst placed on the downstream side. The protective atmosphere is nitrogen or argon, the high-temperature phosphating temperature is 300-350℃, and the heating rate of the tube furnace is 2-3℃·min. -1 The heat preservation time is 2 to 3 hours.

[0017] Based on the above technical solution, in S1 and S2, the vacuum drying temperature is 60-80℃ and the drying time is 5-12h.

[0018] Based on the above technical solution, in step S4, the area of ​​the MOF-based catalyst used for the assembled flow electrolytic cell anode and cathode is 1×1 cm². 2 The concentration of potassium hydroxide in the alkaline seawater electrolyte is 1 mol·L⁻¹. -1 The applied voltage range is 1V to 2V.

[0019] In a second aspect, the present invention provides a dual-site MOF-based catalyst, which is prepared by the method of electrocatalytic total hydrolysis of seawater according to any one of the above embodiments.

[0020] Thirdly, the present invention provides an application of the method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to any one of the above embodiments in the electrocatalytic total hydrolysis of seawater.

[0021] Compared with related technologies, the beneficial effects of the present invention are as follows:

[0022] The present invention provides a method for the electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst. The synthesized catalyst has a two-dimensional nanosheet morphology and can be uniformly loaded on a conductive nickel foam substrate. The catalyst grows in situ and bonds firmly to the substrate, avoiding problems such as weak conductivity caused by drop-coating with binders. The doping of [WO] groups can provide a Lewis acid layer, enhancing resistance to OH groups. - The adsorption of [a substance] promotes the OER reaction and repels Cl. - On the other hand, the heterostructure formed with CoP can regulate the electronic structure of the Co active site, while W is hydrophilic and can more effectively capture water molecules, serving as the active site for HER. The presence of phosphate groups generated by the oxidation of P in CoP can further effectively avoid chlorine corrosion in seawater and extend the long-term stability of the catalyst. When used as a working electrode, the dual-site MOF-based catalyst exhibits high catalytic efficiency and cycle stability for both HER and OER in the electrocatalytic total hydrolysis of seawater. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other embodiments can be derived from the provided drawings without creative effort.

[0024] Figure 1 This is a flowchart of the method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst provided by the present invention;

[0025] Figure 2 This is a scanning electron microscope image of the 0.6WO-CoP@NF catalyst prepared in Example 1 of this invention;

[0026] Figure 3 This is a transmission electron microscope (TEM) image of 0.6WO-CoP grown on the 0.6WO-CoP@NF catalyst prepared in Example 1 of this invention.

[0027] Figure 4 This is the energy dispersive X-ray spectrum of the 0.6WO-CoP@NF catalyst prepared in Example 1 of this invention;

[0028] Figure 5These are the X-ray diffraction patterns of the 0.6WO-CoP@NF catalyst in Example 1 and the CoP@NF catalyst in Comparative Example 1 of the present invention;

[0029] Figure 6 These are the X-ray photoelectron spectra of the 0.6WO-CoP@NF catalyst in Example 1 and the CoP@NF in Comparative Example 1 of this invention;

[0030] Figure 7 These are test graphs of the oxygen evolution reaction performance of comparative examples 1-3 of this invention;

[0031] Figure 8 These are the hydrogen evolution reaction performance test graphs of Comparative Examples 1-3 of this invention;

[0032] Figure 9 This is a scatter plot of the oxygen evolution reaction stability of Comparative Examples 1 and 3 of the present invention.

[0033] Figure 10 These are polarization scatter plots of total water splitting measured in Examples 1 and 2 of this invention;

[0034] Figure 11 This is a scatter plot of the total solution seawater stability measured in Example 1 of the present invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and examples:

[0036] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0040] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0041] This invention provides a method for the electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst, comprising the following steps:

[0042] S1. Pre-treat the nickel foam by rapidly adding an aqueous solution of 2-methylimidazole to an aqueous solution of cobalt nitrate hexahydrate and mixing them evenly to obtain a ZIF-L(Co) solution. Place the pre-treated nickel foam into the ZIF-L(Co) solution, stir and react. After removing it, rinse off the unreacted ZIF-L(Co) residue and place it in a vacuum drying oven to dry, thus obtaining nickel foam with a ZIF-L(Co) precursor grown on it.

[0043] S2, deionized water and anhydrous ethanol are mixed to form a mixed solvent. Sodium tungstate is dissolved in the mixed solvent to obtain a sodium tungstate solution. The ZIF-L(Co) precursor nickel foam obtained in step S1 is immersed in the sodium tungstate solution, etched, removed, rinsed with water, and dried in a vacuum drying oven to obtain a product coated with WO4. 2- / Co(OH)2 intermediate foamed nickel;

[0044] S3, the WO4 obtained in step S2 2- / Co(OH)2 intermediate foamed nickel and phosphorus source are placed in a tube furnace and subjected to high-temperature phosphating in a protective atmosphere. After holding at the temperature for a period of time, the mixture is naturally cooled to room temperature to obtain a dual-site MOF-based catalyst.

[0045] S4. Assemble a flow electrolyzer. Use the dual-site MOF-based catalyst obtained in step S3 as both the anode and cathode of the flow electrolyzer. Use an alkaline seawater solution as the electrolyte. Apply voltage to the electrolyzer to carry out an electrocatalytic reaction. The anode undergoes an oxygen evolution reaction to produce oxygen, and the cathode undergoes a hydrogen evolution reaction to produce hydrogen.

[0046] Based on the above technical solution, the step S1 of pretreatment of nickel foam includes: placing the nickel foam in hydrochloric acid solution, deionized water and ethanol solution in sequence for ultrasonic treatment, and then placing it in a vacuum drying oven for drying to obtain pretreated nickel foam.

[0047] Based on the above technical solution, the size of the nickel foam is 30mm*20mm*1.6mm, and the concentration of the hydrochloric acid solution is 2-3 mol·L⁻¹. -1 The sonication time for hydrochloric acid is 15–20 min, for deionized water it is 10–15 min, and for ethanol solution it is 5–10 min. Preferably, the concentration of the hydrochloric acid solution is 3 mol·L⁻¹. -1 The sonication time for hydrochloric acid was 15 min, for deionized water it was 10 min, and for ethanol solution it was 5 min.

[0048] Based on the above technical solution, in step S1, the concentration of the 2-methylimidazole aqueous solution is 0.4 mol·L⁻¹. -1 The concentration of the cobalt nitrate hexahydrate aqueous solution is 0.05 mol·L⁻¹. -1 The volume ratio of 2-methylimidazole aqueous solution and cobalt nitrate hexahydrate aqueous solution is 1:1, and the reaction time is 3-4 hours. Preferably, the reaction time is 4 hours.

[0049] Based on the above technical solution, in step S2, the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 4:1, and the concentration of sodium tungstate solution is 0.02 mol·L⁻¹. -1 The etching time is 10-15 minutes, and the etching temperature is 85°C. Preferably, the etching time is 15 minutes.

[0050] Based on the above technical solution, in step S3, the phosphorus source is sodium hypophosphite powder, the mass ratio of sodium hypophosphite is 0.3-0.4g, the sodium hypophosphite and the intermediate nickel foam are placed in two separate ceramic boats, with the sodium hypophosphite placed on the upstream side and the catalyst placed on the downstream side. The protective atmosphere is nitrogen or argon, the high-temperature phosphating temperature is 300-350℃, and the heating rate of the tube furnace is 2-3℃·min. -1 The holding time is 2-3 hours. Preferably, the mass ratio of sodium hypophosphite is 0.4g, the high-temperature phosphating temperature is 350℃, and the heating rate of the tube furnace is 2℃·min. -1 The heat preservation time is 2 hours.

[0051] Based on the above technical solution, in steps S1 and S2, the vacuum drying temperature is 60–80°C, and the drying time is 5–12 hours. Preferably, the vacuum drying temperature is 60°C, and the drying time is 6 hours.

[0052] Based on the above technical solution, in step S4, the area of ​​the MOF-based catalyst used for the assembled flow electrolytic cell anode and cathode is 1×1 cm². 2 The concentration of potassium hydroxide in the alkaline seawater electrolyte is 1 mol·L⁻¹. -1 The applied voltage range is 1V to 2V.

[0053] In a second aspect, the present invention provides a dual-site MOF-based catalyst, which is prepared by the method of electrocatalytic total hydrolysis of seawater according to any one of the above embodiments.

[0054] Thirdly, the present invention provides an application of the method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to any one of the above embodiments in the electrocatalytic total hydrolysis of seawater.

[0055] Example 1

[0056] Combination Figure 1 As shown in the embodiments of this disclosure, a method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst is provided, comprising the following steps:

[0057] S1. Place nickel foam with dimensions of 30mm*20mm*1.6mm sequentially into a 3mol·L⁻¹ solution. -1 The nickel foam was ultrasonically treated with hydrochloric acid solution for 15 min, deionized water for 10 min, and anhydrous ethanol solution for 5 min, and then dried in a vacuum drying oven at 60℃ for 6 h to obtain pretreated nickel foam; 40 ml of 0.4 mol·L⁻¹ -1 The 2-methylimidazole aqueous solution was rapidly added to 40 ml of 0.05 mol·L cobalt nitrate hexahydrate aqueous solution and mixed evenly to obtain ZIF-L(Co) solution. The pretreated nickel foam was placed into the ZIF-L(Co) solution and stirred for 4 h. After removal, the unreacted ZIF-L(Co) residue was washed away with deionized water and placed in a vacuum drying oven at 60 °C for 6 h to obtain nickel foam with ZIF-L(Co) precursor grown on it.

[0058] S2. Mix 80 mL of deionized water and 20 mL of anhydrous ethanol to form a mixed solvent. Dissolve 0.6 g of sodium tungstate in the mixed solvent to obtain a sodium tungstate solution. Immerse the ZIF-L(Co) precursor nickel foam obtained in step S1 into the sodium tungstate solution. Etch at 85°C for 15 min, then remove and rinse repeatedly with deionized water. Place in a vacuum drying oven and dry at 60°C for 6 h to obtain a product coated with WO4. 2- Nickel foam is an intermediate of / Co(OH)2.

[0059] S3, Take the WO4 obtained in step S2 2- / Co(OH)2 intermediate nickel foam and 0.4g sodium hypophosphite were placed in a tube furnace, with the sodium hypophosphite on the upstream side and the intermediate on the downstream side. The tube furnace was heated at 2℃·min under a nitrogen atmosphere. -1 The heating rate was increased to 350℃ for high-temperature phosphating, and after holding at that temperature for 2 hours, it was naturally cooled to room temperature to obtain the dual-site MOF-based catalyst 0.6WO-CoP@NF.

[0060] S4. Assemble a flow electrolyzer. Use the dual-site MOF-based catalyst obtained in step S3 as both the anode and cathode of the flow electrolyzer. Add 1 mol of potassium hydroxide to 1 L of natural seawater to dissolve it and obtain alkaline seawater. Use alkaline seawater as the electrolyte and apply a voltage from 1V to 2V to the electrolyzer to carry out the electrocatalytic reaction. The anode undergoes an oxygen evolution reaction to produce oxygen, and the cathode undergoes a hydrogen evolution reaction to produce hydrogen.

[0061] Example 2

[0062] This embodiment uses the same method as Embodiment 1, with the identical parts omitted. The difference from Embodiment 1 is that in this embodiment, 1 mol·L⁻¹ is used. -1 The potassium hydroxide solution is used as the electrolyte.

[0063] Comparative Example 1

[0064] The method in this embodiment is the same as that in Example 1, with the same parts omitted. The difference from Example 1 is that in this embodiment, a three-electrode system is used, with a two-site MOF-based catalyst as the working electrode, a high-purity graphite rod as the counter electrode, and Ag / AgCl as the reference electrode. The electrocatalytic reaction is carried out in the electrolyte, and the mass of sodium tungstate is 0, 0.3, 0.6, and 0.9 g, respectively.

[0065] Comparative Example 2

[0066] This embodiment uses the same method as Comparative Example 1, with the identical parts omitted. The difference from Comparative Example 1 is that in this embodiment, 1 mol of potassium hydroxide and 0.5 mol of sodium chloride are added to 1 L of deionized water to dissolve and obtain simulated seawater, which is then used as the electrolyte.

[0067] Comparative Example 3

[0068] This embodiment uses the same method as Comparative Example 1, with the identical parts omitted. The difference from Comparative Example 1 is that in this embodiment, 1 mol of potassium hydroxide is added to 1 L of natural seawater to dissolve and obtain alkaline seawater, which is then used as the electrolyte.

[0069] Figure 2This is a scanning electron microscope image of the 0.6WO-CoP@NF catalyst prepared in Example 1 of this invention. It can be seen that it exhibits a nanosheet morphology. The nanosheets have more lateral dimensions and abundant unsaturated metal active sites, which is conducive to the binding of water molecules and improves electrocatalytic performance.

[0070] Figure 3 The transmission electron microscope (TEM) image of 0.6WO-CoP grown on the 0.6WO-CoP@NF catalyst prepared in Example 1 of this invention shows that the interplanar spacing of CoP decreased by approximately 0.003 nm, which can be attributed to the generation of lattice stress caused by the doping of [WO] groups. The reduction in interplanar spacing indicates the successful doping of [WO] groups.

[0071] Figure 4 The image shows the energy dispersive X-ray spectrum of the 0.6WO-CoP@NF catalyst prepared in Example 1 of this invention. It can be seen that the P, Co, O, W and C elements are evenly distributed in the 0.6WO-CoP catalyst.

[0072] Figure 5 The X-ray diffraction patterns of the 0.6WO-CoP@NF catalyst in Example 1 and the CoP@NF catalyst in Comparative Example 1 are shown. It can be seen that the crystal structures of the two samples correspond well with the diffraction peaks of the standard CoP card (CoP#65-2593), indicating that the main crystal phase of the catalyst is CoP, which is consistent with the results of transmission electron microscopy.

[0073] Figure 6 These are the X-ray photoelectron spectra of the 0.6WO-CoP@NF catalyst in Example 1 and the CoP@NF in Comparative Example 1 of this invention. Figure 6 As can be seen in a, the high-resolution Co 2p spectrum shows that they belong to Co 2p. 3 / 2 and Co 2p 1 / 2 The binding energies of the Co-P bonds are characterized by peaks of 778.61 eV and 793.59 eV, and belong to Co 2p. 3 / 2 and Co 2p 1 / 2 The binding energies of the Co-O bonds are characterized by peaks at 782.19 eV and 798.21 eV, while peaks at 786.13 eV and 802.77 eV correspond to two satellite peaks. Furthermore, compared to CoP@NF, the Co 2p spectrum of 0.6WO-CoP@NF shows a slight positive shift, a slight increase in the oxidation state of Co, and electron transfer from Co, indicating successful doping of the [WO] group. Figure 6 b is the high-resolution w 4f spectrum, where w 4f 7 / 2 and w4f 5 / 2 These are 36.12 eV and 38.4 eV respectively, corresponding to the WO bond. From Figure 6 The X-ray photoelectron spectrum of c at p 2p shows that the peaks at 129.6 eV and 130.4 eV belong to 2p. 3 / 2 and 2p 1 / 2 The peak at 134.20 eV is from the oxidation state of P, while the Co-P bond is from the peak at 134.20 eV.

[0074] Figure 7 These are test graphs of the oxygen evolution reaction performance of comparative examples 1-3 of this invention. Figure 7 a represents the OER polarization curves of catalysts with different tungsten contents in Comparative Example 1, from... Figure 7 As can be seen from a, the 0.6WO-CoP@NF has the smallest overpotential, which is within 100 mA·cm⁻¹. -2 At the given current density, the overpotential is 335mV. Figure 7 b is the Tafel slope plot for catalysts with different tungsten contents in Comparative Example 1. It can be seen that 0.6WO-CoP@NF has the smallest Tafel slope of 106.4 mV·dec. -1 This indicates that 0.6WO-CoP@NF has relatively fast OER kinetics. Figure 7 c shows the electrochemical impedance spectroscopy of catalysts with different tungsten contents in Comparative Example 1. It can be seen that the 0.6WO-CoP@NF catalyst has a smaller charge transfer resistance, which proves that it has higher conductivity and faster charge transfer rate in the OER process. Figure 7 d shows the OER polarization curves of the 0.6WO-CoP@NF catalyst in Examples 1-3, from which it can be seen that 0.6WO-CoP@NF reacts in simulated seawater and at 1 mol·L⁻¹. -1 The OER activity in potassium hydroxide solution showed almost no difference. However, in alkaline seawater, electrode poisoning caused by natural seawater pollutants led to some activity loss; even under these conditions, the 0.6WO-CoP@NF catalyst could still provide 100 mA·cm⁻¹ at 370 mV. -2 The current density indicates that the 0.6WO-CoP@NF catalyst has excellent chlorine removal capability.

[0075] Figure 8 These are the hydrogen evolution reaction performance test diagrams for comparative examples 1-3 of this invention. Figure 8 a represents the HER polarization curves of catalysts with different tungsten contents in Comparative Example 1, from... Figure 8 As can be seen from a, the 0.6WO-CoP@NF has the smallest overpotential, which is within 10 mA·cm⁻¹. -2 At the current density, the overpotential is 66mV. Figure 8b summarizes the overpotentials of catalyst electrodes with different tungsten contents at different currents in HER, and shows that 0.6WO-CoP@NF has the best reactivity in HER. Figure 8 c is the Tafel slope plot for catalysts with different tungsten contents in Comparative Example 1. It can be seen that 0.6WO-CoP@NF has the smallest Tafel slope of 74.4 mV·dec. -1 This indicates that 0.6WO-CoP@NF has relatively fast hydrogen evolution kinetics. Figure 8 Figure d shows the HER polarization curves of the 0.6WO-CoP@NF catalyst in Examples 1-3, which demonstrates the HER polarization of the 0.6WO-CoP@NF catalyst in simulated seawater and at 1 mol·L⁻¹. -1 The HER in potassium hydroxide solution showed almost no difference. However, in alkaline seawater, some loss of activity occurred due to electrode poisoning caused by natural seawater pollutants. Even under these conditions, the 0.6WO-CoP@NF catalyst could still provide 100 mA·cm⁻¹ at 185 mV. -2 The current density indicates that the 0.6WO-CoP@NF catalyst has excellent chlorine removal capability.

[0076] Figure 9 This is a scatter plot of the OER stability of the 0.6WO-CoP@NF catalyst measured by chronopotentiometric method in Comparative Examples 1 and 3 of this invention. It can be seen that at 100 mA·cm⁻¹... -2 0.6WO-CoP@NF catalyst at a current density of 1 mol·L -1 It can remain stable for 100 hours in potassium hydroxide solution and alkaline seawater, proving that it has good stability.

[0077] Figure 10 These are the polarization curves of total water splitting measured in Examples 1 and 2 of this invention. It can be seen that at 60℃, 1 mol·L⁻¹ -1 In potassium hydroxide electrolyte, only 1.59V is required to achieve 100mA·cm. -2 The current density was measured, and the polarization curves in alkaline seawater showed that the catalyst still had good performance.

[0078] Figure 11 This is a scatter plot of the stability of alkaline seawater obtained by the chronopotential method in Example 1 of this invention. It can be seen that at 100 mA·cm -2 It can operate stably for 250 hours at a current density without significant activity decay.

[0079] The present invention has been described above by way of example, but the present invention is not limited to the specific embodiments described above. Any modifications or variations made based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for the electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst, characterized in that, Includes the following steps: S1. Pre-treat the nickel foam by rapidly adding an aqueous solution of 2-methylimidazole to an aqueous solution of cobalt nitrate hexahydrate and mixing them evenly to obtain a ZIF-L(Co) solution. Place the pre-treated nickel foam into the ZIF-L(Co) solution, stir and react. After removing it, rinse off the unreacted ZIF-L(Co) residue and place it in a vacuum drying oven to dry, thus obtaining nickel foam with a ZIF-L(Co) precursor grown on it. S2, deionized water and anhydrous ethanol are mixed to form a mixed solvent. Sodium tungstate is dissolved in the mixed solvent to obtain a sodium tungstate solution. The ZIF-L(Co) precursor nickel foam obtained in step S1 is immersed in the sodium tungstate solution, etched, removed, rinsed with water, and dried in a vacuum drying oven to obtain a product coated with WO4. 2- / Co(OH)2 intermediate foamed nickel; S3, the WO4 obtained in step S2 2- / Co(OH)2 intermediate foamed nickel and phosphorus source are placed in a tube furnace and subjected to high-temperature phosphating in a protective atmosphere. After holding at the temperature for a period of time, the mixture is naturally cooled to room temperature to obtain a dual-site MOF-based catalyst. S4. Assemble a flow electrolyzer. Use the dual-site MOF-based catalyst obtained in step S3 as both the anode and cathode of the flow electrolyzer. Use an alkaline seawater solution as the electrolyte. Apply voltage to the electrolyzer to carry out an electrocatalytic reaction. The anode undergoes an oxygen evolution reaction to produce oxygen, and the cathode undergoes a hydrogen evolution reaction to produce hydrogen.

2. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 1, characterized in that, In step S1, the pretreatment of nickel foam includes: placing the nickel foam in hydrochloric acid solution, deionized water and ethanol solution in sequence for ultrasonic treatment, and then drying it in a vacuum drying oven to obtain pretreated nickel foam.

3. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 2, characterized in that, The dimensions of the nickel foam are 30mm*20mm*1.6mm, and the concentration of the hydrochloric acid solution is 2-3 mol·L⁻¹. -1 The sonication time for hydrochloric acid is 15–20 min, for deionized water it is 10–15 min, and for ethanol solution it is 5–10 min.

4. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 1, characterized in that, In step S1, the concentration of the 2-methylimidazole aqueous solution is 0.4 mol·L⁻¹. -1 The concentration of the cobalt nitrate hexahydrate aqueous solution is 0.05 mol·L⁻¹. -1 The volume ratio of 2-methylimidazole aqueous solution and cobalt nitrate hexahydrate aqueous solution was 1:1, and the stirring reaction time was 3-4 hours.

5. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 1, characterized in that, In step S2, the volume ratio of deionized water to anhydrous ethanol in the mixed solvent is 4:1, and the concentration of the sodium tungstate solution is 0.02 mol·L⁻¹. -1 The etching time is 10-15 minutes and the etching temperature is 85℃.

6. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 1, characterized in that, In step S3, the phosphorus source is sodium hypophosphite powder, with a mass ratio of 0.3–0.4 g. The sodium hypophosphite and the intermediate nickel foam are placed in two separate ceramic boats, with the sodium hypophosphite on the upstream side and the catalyst on the downstream side. The protective atmosphere is nitrogen or argon. The high-temperature phosphating temperature is 300–350 °C, and the heating rate of the tube furnace is 2–3 °C / min. -1 The heat preservation time is 2 to 3 hours.

7. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 1, characterized in that, In S1 and S2, the vacuum drying temperature is 60-80℃ and the drying time is 5-12h.

8. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to claim 1, characterized in that, In step S4, the area of ​​the MOF-based catalyst used for the assembled flow electrolytic cell anode and cathode is 1×1 cm². 2 The concentration of potassium hydroxide in the alkaline seawater electrolyte is 1 mol·L⁻¹. -1 The applied voltage range is 1V to 2V.

9. A dual-site MOF-based catalyst, characterized in that, The method for preparing the two-site MOF-based catalyst for the electrocatalytic total hydrolysis of seawater according to any one of claims 1 to 8.

10. The method for electrocatalytic total hydrolysis of seawater using a dual-site MOF-based catalyst according to any one of claims 1 to 8, applied to the electrocatalytic total hydrolysis of seawater.

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