Silver-loaded and anion-interspersed layered catalyst as well as preparation method and application thereof

Abstract

The invention discloses a silver-loaded and anion-interspersed layered catalyst and a preparation method and application thereof.The preparation method comprises the steps that firstly, a hydrothermal method is adopted for growing oxalate ion-interspersed layered ferrocobalt bimetal hydroxide CoFe-C2O4 < 2->-LDH on foamed nickel, and then the layered ferrocobalt bimetal hydroxide CoFe-C2O4 < 2->-LDH is soaked in an aqueous solution of AgNO3; and reacting to generate the silver-loaded oxalate ion interspersed layered ferrocobalt double metal hydroxide Ag / CoFe-C2O4 < 2->-LDH. The silver-loaded and anion-interspersed layered hydroxide has excellent catalytic activity and stability in seawater electrolysis oxygen evolution reaction. Under the applied voltage, the Ag nanoparticles generate AgCl in situ in the seawater oxygen evolution process, chloride ions can be fixed, and the Ag nanoparticles and C2O4 < 2-> anion groups which are embedded into the CoFe layered double hydroxides and have high electronegativity cooperate to construct a chloride ion erosion resistant barrier, so that the chlorine corrosion resistance of the NiFe layered double hydroxides in seawater electrolysis is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to a silver-supported and anion-intercalated layered catalyst, its preparation method and application, and particularly to a silver-supported and anion-intercalated layered double hydroxide catalyst, its preparation method and its application in seawater electrolysis. Background Technology

[0002] Currently, hydrogen production through water electrolysis largely relies on high-purity ultrapure water, but global freshwater resources are scarce, and water production costs remain high, limiting large-scale deployment. Seawater accounts for 96.5% of the Earth's total water volume, is abundant, and requires no additional purification; therefore, direct seawater electrolysis is considered one of the most feasible ways to achieve large-scale green hydrogen production.

[0003] Seawater is rich in impurity ions (such as Ca). 2+ Mg 2+ Cl - (etc.) and microorganisms pose serious challenges to the seawater electrolysis process. On the anode side, due to Cl... - The presence of [a substance] may lead to chlorine evolution reaction (CER) during oxidation, especially during electrolysis at high current densities, where some Cl [is present]. - It consumes electrons and produces chlorine gas or other chlorine-containing byproducts, thus significantly reducing electrolysis efficiency and selectivity. Theoretically, the potential difference between OER and CER is 480mV, but due to the poor OER activity of existing catalysts, the actual potential difference is further reduced. This significantly increases the difficulty of achieving long-term stable hydrogen production at industrial-grade high current densities. However, on the cathode side, due to Ca… 2+ Mg 2+ The presence of [a substance] consumes H during the hydrogen evolution reaction (HER). + Ions cause a local pH increase, Ca 2+ and Mg 2+ Rapid deposition occurs as Ca(OH)₂ and Mg(OH)₂ precipitates, covering the active sites; in addition, Cl - or ClO - The presence of chloride ions will corrode and damage the catalyst or conductive substrate interface over a long period of time, eventually leading to electrode failure.

[0004] In existing technologies, Cr-containing catalysts are often used to improve their resistance to oxygen evolution by chloride chlorination. However, industrial scale-up will inevitably produce Cr-containing catalysts. 3+ Waste liquid, if left untreated, is easily converted into highly toxic Cr in high-temperature and strong oxidizing environments. 6 + Furthermore, high-potential electrolysis at industrial-grade current densities can easily lead to the in-situ formation of highly toxic CrO4. 2-Cr-containing catalysts rapidly spread through groundwater and accumulate biomass, causing long-term, cumulative damage to aquatic and soil ecosystems that is difficult to repair. Therefore, Cr-containing catalysts are not in line with the development direction of green hydrogen production, and there is an urgent need to develop industrial-grade seawater electrochemical oxygen desorption catalysts that are free of heavy metals, highly chlorine-resistant, and environmentally friendly.

[0005] In water electrolysis, the OER (Oxygen Evolution Reaction) has a more complex reaction mechanism and a higher reaction energy barrier than the HER (Hydrogen Evolution Reaction). Therefore, improving the activity of OER catalysts is crucial for reducing the overall energy consumption of hydrogen production through water electrolysis. However, designing and developing catalysts that can efficiently catalyze oxygen evolution in seawater at industrial-grade current densities remains a major challenge in the field of hydrogen production through water electrolysis. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a silver-supported and anion-intercalated layered catalyst, its preparation method and application, which can effectively solve the problems of activity, stability and corrosion resistance under high current density, and provide an efficient and durable OER catalyst material for large-scale seawater electrolysis to produce hydrogen.

[0007] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing a catalyst, comprising the following steps: (1) Dissolve soluble iron salt, soluble cobalt salt, oxalate, urea and ammonium salt in water to prepare a mixed solution; then immerse nickel foam in the mixed solution and carry out a hydrothermal reaction to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ions interpenetrating on nickel foam, denoted as CoFe-C2O4. 2– -LDH; (2) The CoFe-C2O4 obtained in step (1) 2– -LDH was immersed in an aqueous solution of AgNO3 to react and prepare a silver-supported, oxalate-intercalated layered cobalt-iron bimetallic hydroxide, denoted as Ag / CoFe-C2O4. 2– -LDH, i.e., the catalyst.

[0008] Specifically, this invention first uses a hydrothermal method to grow a layered cobalt-iron bimetallic hydroxide CoFe-C2O4 with oxalate ion penetration on nickel foam. 2– -LDH, and then soak it in an aqueous solution of AgNO3 to react and generate a silver-loaded, oxalate-intercalated, layered cobalt-iron bimetallic hydroxide Ag / CoFe-C2O4. 2–-LDH. This silver-supported and anion-intercalated layered hydroxide exhibits excellent catalytic activity and stability in the oxygen evolution reaction of seawater electrolysis. Under applied voltage, Ag nanoparticles generate AgCl in situ during seawater oxygen evolution, which can fix chloride ions in the solution and react with highly negatively charged C2O4 embedded in the CoFe layered double hydroxide. 2– The anionic groups synergistically construct a barrier against chloride ion corrosion, thereby effectively enhancing the chloride corrosion resistance of NiFe layered double hydroxides during seawater electrolysis.

[0009] Meanwhile, in the hydrothermal synthesis of layered hydroxides, this invention adds a certain amount of urea and ammonium salts. The urea decomposes during the hydrothermal process to provide OH-. - and CO3 2- This allows for a slow increase in the solution pH and introduces interlayer anions; ammonium salts are introduced through NH4+. + The NH3 buffer system regulates the pH of the solution and inhibits rapid hydrolysis of metals, thereby jointly promoting the uniform and stable formation of nanosheets or nanoflower structures from layered hydroxides.

[0010] In some embodiments of the present invention, in step (1), the soluble cobalt salt is selected from at least one of cobalt chloride, cobalt nitrate, cobalt sulfate, and cobalt oxalate.

[0011] In some embodiments of the present invention, in step (1), the soluble iron salt is selected from at least one of ferric chloride, ferric nitrate, ferric sulfate, and ferric oxalate.

[0012] In some embodiments of the present invention, in step (1), the ammonium salt is selected from at least one of ammonium chloride, ammonium fluoride, and ammonium bromide.

[0013] In some embodiments of the present invention, in step (1), the oxalate is selected from at least one of lithium oxalate, sodium oxalate, and potassium oxalate.

[0014] In some embodiments of the present invention, in step (1), the concentration of the soluble cobalt salt in the mixed solution is 0.01-0.5 mol / L, the concentration of the soluble iron salt is 0.002-0.5 mol / L, the concentration of the ammonium salt is 0.1-0.7 mol / L, the concentration of the oxalate is 0.5-8.5 mmol / L, and the concentration of the urea is 0.1-3.5 mol / L.

[0015] In some embodiments of the present invention, in step (1), the concentration of the soluble cobalt salt in the mixed solution is 0.01-0.1 mol / L, the concentration of the soluble iron salt is 0.01-0.1 mol / L, the concentration of the ammonium salt is 0.1-0.5 mol / L, the concentration of the oxalate is 1-6 mmol / L, and the concentration of the urea is 0.1-2 mol / L.

[0016] In some embodiments of the present invention, in step (1), the total amount of the soluble cobalt salt and the soluble iron salt is in a molar ratio of 1:(1-3) to the ammonium salt.

[0017] In some embodiments of the present invention, in step (1), the molar ratio of the ammonium salt to urea is 1:(1-5).

[0018] In some embodiments of the present invention, in step (1), the temperature of the hydrothermal reaction is 80-180°C; preferably 100-150°C, and more preferably 110-130°C.

[0019] In some embodiments of the present invention, in step (1), the hydrothermal reaction time is 4-16 hours; preferably 4-12 hours.

[0020] In some embodiments of the present invention, in step (2), the concentration of the aqueous solution of AgNO3 is 0.01-0.5 mol / L; preferably 0.01-0.1 mol / L.

[0021] In some embodiments of the present invention, in step (2), the temperature of the reaction is 20-60°C; preferably 40-60°C.

[0022] In some embodiments of the present invention, in step (2), the reaction time is 0.5-12 hours; preferably 6-12 hours.

[0023] In some embodiments of the present invention, step (1) further includes a step of cleaning the nickel foam with hydrochloric acid, anhydrous ethanol and water in sequence before immersing it in the mixed solution, so as to remove oxides on the surface of the nickel foam.

[0024] In some embodiments of the present invention, step (2) further includes washing the reaction product with deionized water and ethanol after the reaction is completed, and then vacuum drying it at 50-80°C for 6-24 hours.

[0025] A second aspect of the present invention provides a catalyst prepared by the above-described preparation method, the catalyst comprising a nickel foam support and a layered cobalt-iron bimetallic hydroxide supported on the nickel foam support, wherein oxalate ions are interspersed between the layers of the layered cobalt-iron bimetallic hydroxide, and silver nanoparticles are loaded on the layered cobalt-iron bimetallic hydroxide.

[0026] A third aspect of the invention provides the application of the above-described catalyst in the electrolysis of seawater.

[0027] In some embodiments of the present invention, the electrolysis of seawater is carried out in a three-electrode system, wherein KOH and seawater are used as electrolytes, the above-mentioned catalyst is used as the working electrode, Hg / HgO is used as the reference electrode, and a carbon rod electrode is used as the counter electrode.

[0028] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) In this invention, a layered cobalt-iron bimetallic hydroxide CoFe-C2O4 with oxalate ion penetration is first grown on nickel foam using a hydrothermal method. 2– -LDH, and then soak it in an aqueous solution of AgNO3 to react and generate a silver-loaded, oxalate-intercalated, layered cobalt-iron bimetallic hydroxide Ag / CoFe-C2O4. 2– -LDH catalyst, which exhibits excellent catalytic activity and stability in the oxygen evolution reaction of seawater electrolysis. On the one hand, through the oxalate anion C2O4 2– Constructing negatively charged interlayer corridors to form electrostatic barriers through electrostatic repulsion, thereby preventing Cl from... - It penetrates into the layered hydroxide, inhibiting Cl- - On the one hand, it addresses the corrosion of the catalyst; on the other hand, by modifying silver nanoparticles, in-situ electrochemical chlorination (Ag→AgCl) is performed during the OER process, acting as a sacrificial chloride ion reservoir to suppress the large amount of electrolyte Cl. - Migration, and the formation of AgCl leads to the free Cl near the electrode-electrolyte interface. - The concentration decreased significantly.

[0029] (2) Compared with traditional C2O4 2- Compared to -LDHs, C2O4 2– Anion intercalation layer makes Cl - The adsorption energy barrier was increased by 1.8 eV, while Ag and free Cl in the electrolyte... - The reaction forms AgCl, which releases free Cl near the electrode-electrolyte interface. - The concentration decreases. These coupling effects result in excellent oxidation performance of alkaline seawater, requiring only a low overpotential of 386 mV to reach 1000 mA cm⁻¹. -2and at 500mA cm -2 It can operate stably for more than 3000 hours at industrial-grade current densities without significant degradation. The Ag / CoFe-C2O4 prepared in this invention... 2- -LDH in alkaline seawater solution at 1000 mA cm -2 It can operate stably for over 1500 hours under high current density. Especially at high Cl... - Under harsh conditions of a concentrated electrolyte (1 mol / L KOH + 1.5 mol / L NaCl), the catalyst at 1000 mA cm⁻¹ -2 It can react stably for more than 220 hours under high current density, demonstrating strong resistance to chlorine corrosion and stability.

[0030] (3) The preparation method of the catalyst of the present invention is simple, the raw material cost is low, the process is controllable, and it can significantly improve Cl - The adsorption and oxidation at the anode effectively protect the anode from corrosion and improve the efficiency of seawater electrolysis. Furthermore, the preparation and electrolysis processes do not use or generate highly toxic and environmentally polluting heavy metal ions such as chromium, meeting the requirements for environmentally friendly, highly active, and highly chlorine-resistant seawater electrolysis catalysts for hydrogen production in industrial-grade seawater development. Attached Figure Description

[0031] Figure 1 The XRD patterns are of the catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention. Figure 2 The Raman spectra of the catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention are shown below. Figure 3 This is a SEM image of the catalyst prepared in Example 1 of the present invention; Figure 4 Here is a SEM image of the catalyst prepared in Comparative Example 1 of this invention; Figure 5 Here is a SEM image of the catalyst prepared in Comparative Example 2 of this invention; Figure 6 The HRTEM and EDX images of the catalyst prepared in Example 1 of this invention are shown. Figure 7 This is a linear voltammetry (LSV) curve of the catalysts prepared in Example 1 and Comparative Examples 1-4 of this invention in alkaline seawater; Figure 8 The corrosion Tafel curves of the catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention in alkaline seawater; Figure 9 The catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention were tested in an alkaline seawater solution at 500 mA cm⁻¹. -2Oxygen evolution stability test graph under current density; Figure 10 The catalyst prepared in Example 1 of this invention was tested in an alkaline seawater solution at 1000 mA cm⁻¹. -2 Oxygen evolution stability test graph under current density; Figure 11 The catalyst prepared in Example 1 of this invention was tested in a high-chlorine alkaline simulated seawater solution at 1000 mA / cm². -2 Oxygen evolution stability test graph under current density; Figure 12 This is a SEM image of the catalyst prepared in Example 1 of the present invention after a stability test in alkaline seawater; Figure 13 The images shown are HRTEM and EDX images of the catalyst prepared in Example 1 of this invention after stability testing in alkaline seawater. Figure 14 This is a diagram illustrating the chlorine corrosion resistance mechanism of the catalyst prepared in Example 1 of this invention during oxygen evolution in alkaline seawater. Detailed Implementation

[0032] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0033] Example 1 A method for preparing a layered double hydroxide catalyst co-modified by silver support and anion intercalation includes the following steps: (1) The foamed nickel carrier was ultrasonically cleaned in hydrochloric acid (concentration of 3 mol / L), anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried in a vacuum oven at 50°C for 12 hours for later use.

[0034] (2) Weigh 2 mmol of cobalt nitrate, 1 mmol of ferric nitrate, 4 mmol of ammonium fluoride, 0.2 mmol of sodium oxalate and 10 mmol of urea and dissolve them in 35 mL of deionized water and stir well to obtain a mixed solution; then place the nickel foam in the mixed solution, transfer it to a reaction vessel, heat it to 125 °C in an oven and carry out a hydrothermal reaction for 6 hours to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ions inserted on the nickel foam; then wash it repeatedly with deionized water and anhydrous ethanol 3 times in sequence, and dry it at 60 °C for 12 hours.

[0035] (3) The oxalate-intercalated layered cobalt-iron bimetallic hydroxide obtained in step (2) was placed in a 0.01 mol / L silver nitrate solution and soaked at 25°C for 6 hours. Then, it was washed three times with deionized water and ethanol in sequence and dried at 60°C for 12 hours to obtain the silver-supported and anion-intercalated modified layered bimetallic hydroxide catalyst of this embodiment, denoted as Ag / CoFe-C2O4. 2- -LDH.

[0036] Example 2 A method for preparing a layered double hydroxide catalyst co-modified by silver support and anion intercalation includes the following steps: (1) The foamed nickel carrier was ultrasonically cleaned in hydrochloric acid (concentration of 3 mol / L), anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried in a vacuum oven at 50°C for 12 hours for later use.

[0037] (2) Weigh 1.5 mmol of cobalt nitrate, 1.5 mmol of ferric nitrate, 4 mmol of ammonium fluoride, 0.3 mmol of sodium oxalate and 10 mmol of urea, dissolve them in 35 mL of deionized water and stir well to obtain a mixed solution; then place the nickel foam in the mixed solution, transfer it to a reaction vessel, heat it to 130 °C in an oven and carry out a hydrothermal reaction for 4 hours to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ions inserted on the nickel foam; then wash it repeatedly with deionized water and anhydrous ethanol 3 times in sequence, and dry it at 60 °C for 12 hours.

[0038] (3) The oxalate-intercalated layered cobalt-iron bimetallic hydroxide obtained in step (2) was placed in a 0.05 mol / L silver nitrate solution and soaked at 30°C for 2 hours. Then, it was washed three times with deionized water and ethanol in sequence and dried at 60°C for 12 hours to obtain the silver-supported and anion-intercalated layered bimetallic hydroxide catalyst of this embodiment, denoted as Ag / CoFe-C2O4. 2- -LDH.

[0039] Comparative Example 1 A method for preparing a silver-supported layered double hydroxide catalyst includes the following steps: (1) The foamed nickel carrier was ultrasonically cleaned in hydrochloric acid (concentration of 3 mol / L), anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried in a vacuum oven at 50°C for 12 hours for later use.

[0040] (2) Weigh 2 mmol of cobalt nitrate, 1 mmol of ferric nitrate, 4 mmol of ammonium fluoride and 10 mmol of urea and dissolve them in 35 mL of deionized water and stir evenly to obtain a mixed solution; then place the nickel foam in the mixed solution, transfer it to a reaction vessel, heat it to 125 °C in an oven and carry out a hydrothermal reaction for 6 hours to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ions inserted on the nickel foam; then wash it repeatedly with deionized water and anhydrous ethanol 3 times in sequence, and dry it at 60 °C for 12 hours.

[0041] (3) The oxalate-intercalated layered cobalt-iron bimetallic hydroxide obtained in step (2) was placed in a silver nitrate solution with a concentration of 0.01 mol / L and soaked at 25°C for 6 hours. Then it was washed repeatedly with deionized water and ethanol three times in sequence and dried at 60°C for 12 hours to obtain the silver-supported layered bimetallic hydroxide catalyst of this comparative example, denoted as Ag / CoFe-LDH.

[0042] Comparative Example 2 A method for preparing an anion-intercalated layered double hydroxide catalyst includes the following steps: (1) The foamed nickel carrier was ultrasonically cleaned in hydrochloric acid (concentration of 3 mol / L), anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried in a vacuum oven at 50°C for 12 hours for later use.

[0043] (2) Weigh 2 mmol of cobalt nitrate, 1 mmol of ferric nitrate, 4 mmol of ammonium fluoride, 0.2 mmol of sodium oxalate, and 10 mmol of urea, dissolve them in 35 mL of deionized water, and stir until homogeneous to obtain a mixed solution; then place nickel foam in the mixed solution, transfer it to a reaction vessel, heat it to 125 °C in an oven, and carry out a hydrothermal reaction for 6 hours to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ion interpenetration supported on nickel foam; then wash it repeatedly three times with deionized water and anhydrous ethanol, and dry it at 60 °C for 12 hours to obtain the anion-interpenetrated co-modified layered bimetallic hydroxide catalyst of this comparative example, denoted as CoFe-C2O4. 2- -LDH.

[0044] Comparative Example 3 A method for preparing a layered double hydroxide catalyst includes the following steps: (1) The foamed nickel carrier was ultrasonically cleaned in hydrochloric acid (concentration of 3 mol / L), anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried in a vacuum oven at 50°C for 12 hours for later use.

[0045] (2) Weigh 2 mmol of cobalt nitrate, 1 mmol of ferric nitrate, 4 mmol of ammonium fluoride and 10 mmol of urea and dissolve them in 35 mL of deionized water and stir evenly to obtain a mixed solution; then place nickel foam in the mixed solution, transfer it to a reaction vessel, heat it to 125 °C in an oven and carry out a hydrothermal reaction for 6 hours to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ions inserted on nickel foam; then wash it repeatedly with deionized water and anhydrous ethanol 3 times in sequence, and dry it at 60 °C for 12 hours to obtain the layered bimetallic hydroxide catalyst of this comparative example, denoted as CoFe-LDH.

[0046] Comparative Example 4 A method for preparing a RuO2 catalyst includes the following steps: 5 mg of RuO2 powder and 50 μL of 5 wt% Nafion solution were dispersed in 950 μL of anhydrous ethanol and sonicated for 15 min to obtain a homogeneous mixture; then 160 μL of the mixture was dropped onto a surface with an area of ​​0.3 cm². 2 The RuO2 catalyst of this comparative example was prepared by drying the RuO2 on nickel foam in a vacuum drying oven at 50°C.

[0047] Performance testing 1. Microstructure Figure 1 The Ag / CoFe-C2O4 prepared in Example 1 and Comparative Examples 1-3 2- -LDH, Ag / CoFe-LDH, CoFe-C2O4 2- XRD patterns of -LDH and CoFe-LDH catalysts, with the horizontal axis 2Theta representing the diffraction angle 2θ and the vertical axis Intensity representing the intensity of the diffraction peaks. From Figure 1 It can be observed that the prepared samples are consistent with the CoFe-LDH standard card (PDF#50-0235), and no new phase is found. Moreover, no standard peak of Ag is found in the XRD pattern, which may be due to the small size and relatively low content of Ag nanoparticles.

[0048] Figure 2 The Ag / CoFe-C2O4 prepared in Example 1 and Comparative Examples 1-3 2- -LDH, Ag / CoFe-LDH, CoFe-C2O4 2- Raman spectra of -LDH and CoFe-LDH catalysts, with the horizontal axis representing Raman shift and the vertical axis representing spectral intensity. Figure 2 It can be seen that Ag / CoFe-C2O4 2- -LDH and CoFe-C2O4 2--LDH's Raman spectrum at 917 cm⁻¹ -1 (ν1 symmetrical stretching) and 1478cm -1 Intercalated C2O4 was detected at (ν3 asymmetric stretching). 2- The characteristic peaks confirm that C2O4 2- Successfully inserted into the original CoFe-LDH interlayer.

[0049] Figure 3-5 Ag / CoFe-C2O4 prepared in Example 1, Comparative Example 1, and Comparative Example 2, respectively. 2- -LDH, Ag / CoFe-LDH and CoFe-C2O4 2- SEM images of the -LDH catalysts show that all three catalysts have nanosheet structures.

[0050] Figure 6 Ag / CoFe-C2O4 prepared for the example 2- The high-resolution transmission electron microscopy (HRTEM) image of -LDH reveals Ag / CoFe-C2O4 2- The -LDH composite material has a nanosheet structure, showing that metallic Ag nanocrystals are uniformly distributed on the LDH support. Lattice fringe analysis measured interplanar spacings of 0.271 nm and 0.235 nm, respectively, corresponding to the (101) crystal plane of CoFe-LDH. Figure 6 c) and the (111) crystal plane of face-centered cubic Ag ( Figure 6 d). Energy dispersive X-ray spectroscopy (EDX) elemental mapping further confirmed that Ag and C elements were uniformly distributed throughout the composite structure.

[0051] 2. Electrochemical properties, corrosion resistance, and reaction mechanism The catalysts prepared in the above examples and comparative examples were directly used as working electrodes in the electrocatalytic oxygen evolution reaction. The specific testing process was as follows: An alkaline seawater solution of 1 mol / L KOH and 0.5 mol / L NaCl was prepared as the electrolyte for electrocatalysis. Nitrogen gas was bubbled through the solution at a rate of 10 mL / min for 30 min to achieve nitrogen saturation. A three-electrode system was assembled using the catalysts prepared in the above examples and comparative examples as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod electrode as the counter electrode. Electrochemical performance was then tested on an electrochemical workstation.

[0052] Figure 7 Ag / CoFe-C2O4 prepared for Example 1 and Comparative Examples 1-4 2- -LDH, Ag / CoFe-LDH, CoFe-C2O4 2-Linear current-voltage (LSV) curves of -LDH, CoFe-LDH, and RuO2 catalysts in alkaline seawater, with the horizontal axis representing potential voltage and the vertical axis representing current density. Figure 7 It can be seen that the Ag / CoFe-C2O4 prepared in Example 1 2- -LDH catalysts exhibit excellent OER performance, requiring only low overpotentials of 238mV, 260mV, 332mV, and 386mV to achieve 10mA cm⁻¹. -2 100mA cm -2 500mA cm -2 and 1000mA cm -2 The current density is significantly better than that of Ag / CoFe-LDH and CoFe-C2O4 prepared in Comparative Examples 1-4. 2- -LDH, CoFe-LDH and RuO2 catalysts, indicating that Ag support and oxalate intercalation can significantly improve the oxygen evolution catalytic activity of layered hydroxides.

[0053] Figure 8 Ag / CoFe-C2O4 prepared in Example 1 and Comparative Examples 1-3, respectively. 2- -LDH, Ag / CoFe-LDH, CoFe-C2O4 2- Corrosion curves of LDH and CoFe-LDH catalysts in alkaline seawater for Tafe1. Figure 8 It can be seen that the Ag / CoFe-C2O4 prepared in Example 1 2- -LDH catalyst has the highest corrosion voltage (-29mV) vs. Hg / HgO) and the lowest corrosion current density (0.43×10) -4 mA cm -2 This indicates that Ag loading and oxalate intercalation can significantly improve the chlorine corrosion resistance of layered hydroxides in alkaline seawater.

[0054] Figure 9 Ag / CoFe-C2O4 prepared for Example 1 and Comparative Examples 1-3 2- -LDH, Ag / CoFe-LDH, CoFe-C2O4 2- -LDH and CoFe-LDH catalysts in alkaline seawater solution at 500 mA cm⁻¹ -2 Results of oxygen evolution stability tests at current densities. Specifically, CoFe-LDH in an alkaline seawater solution at 500 mA cm⁻¹ -2 Current density stability testing showed a significant decay after 100 hours of operation; Ag or C2O4 2-The stability of the modified CoFe-LDH was improved to some extent. However, Ag and C2O4... 2- Co-modified Ag / CoFe-C2O4 2- -LDH exhibits excellent stability at 500 mA cm⁻¹ -2 It operates stably for over 3000 hours at industrial-grade current densities. This is attributed to the electrochemical conversion of silver nanoparticles to AgCl during the oxygen evolution reaction (OER), which immobilizes Cl₂. - And the inserted C2O4 2- A Cl was constructed - The repellent layer synergistically mitigates the corrosion of the anode by chloride ions in seawater.

[0055] like Figure 10 As shown, the Ag / CoFe-C2O4 prepared in Example 1 was used... 2- -LDH catalyst in alkaline seawater solution at 1000 mA cm⁻¹ -2 It can operate stably for over 1500 hours under high current density. Especially at current densities higher than seawater Cl... - The catalyst prepared under harsh conditions of an electrolyte solution with a concentration three times that of 1 mol / L KOH + 1.5 mol / L NaCl, at a speed of 1000 mA cm⁻¹ -2 It can maintain a stable reaction for more than 220 hours under high current density (e.g.) Figure 11 It exhibits strong resistance to chlorine corrosion.

[0056] Figure 12 Ag / CoFe-C2O4 prepared in Example 1 2- -LDH catalyst in alkaline seawater at 500 mA cm⁻¹ -2 SEM images at different scales after 3000 hours of operation reveal Ag / CoFe-C2O4. 2- The stability of the -LDH catalyst nanosheet structure effectively resists chlorine corrosion in seawater.

[0057] Figure 13 Ag / CoFe-C2O4 prepared in Example 1 2- HRTEM image of the -LDH catalyst after alkaline seawater stability test, revealing Ag / CoFe-C2O4 2- -LDH catalyst in alkaline seawater at 500 mA cm⁻¹ -2 After 3000 hours of operation, the nanosheet structure was still maintained, demonstrating its structural stability. Furthermore, it was shown that the metallic nanoparticles of Ag were uniformly distributed on the LDH. Analysis of the lattice fringes using HRTEM images revealed interplanar spacings of 0.322 nm and 0.272 nm, corresponding to the (111) crystal plane of AgCl, respectively. Figure 13b) and the (111) crystal plane of face-centered cubic Ag₂O ( Figure 13 (c) This reveals that during the OER reaction, Ag nanoparticles are converted into AgCl, and a small portion of Ag particles are oxidized into Ag₂O. Energy dispersive X-ray spectroscopy (EDX) elemental mapping further confirms that Ag and C elements remain uniformly distributed throughout the composite structure.

[0058] Figure 14 Ag / CoFe-C2O4 prepared in Example 1 2- The mechanism of resistance to chlorine corrosion of LDH catalyst during oxygen evolution in alkaline seawater is illustrated in the diagram. This invention designs an Ag / CoFe-C2O4 catalyst resistant to chlorine corrosion. 2- -LDH electrocatalyst, through synergistic steric confinement and dynamic chloride removal (Excluding Cl) - The dual modification strategy includes: 1) inserting oxalate anion (C2O4). 2- ), constructing negatively charged interlayer corridors, forming an electrostatic barrier through electrostatic repulsion, preventing Cl - 1) It penetrates into the layered hydroxide lattice through the interlayer spacing and reacts with metal ions, thereby corroding the catalyst layer; 2) It modifies silver nanoparticles to perform in-situ electrochemical chlorination (Ag→AgCl) during the OER process, serving as a sacrificial chloride ion reservoir to fix free Cl in seawater. - Inhibited Cl - The dynamic migration. Experimental and computational analyses show that, compared to traditional CO3... 2- Compared to -LDHs, C2O4 2- Repulsion layer makes Cl - The adsorption energy barrier was increased by 1.8 eV, while the formation of AgCl increased the free Cl near the electrode-electrolyte interface. - The concentration has decreased.

[0059] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method for preparing a catalyst, characterized in that, Includes the following steps: (1) Dissolve soluble iron salt, soluble cobalt salt, oxalate, urea and ammonium salt in water to prepare a mixed solution; then immerse nickel foam in the mixed solution and carry out a hydrothermal reaction to obtain a layered cobalt-iron bimetallic hydroxide with oxalate ions interpenetrating on nickel foam, denoted as CoFe-C2O4. 2– -LDH; (2) The CoFe-C2O4 obtained in step (1) 2– -LDH was immersed in an aqueous solution of AgNO3 to react and prepare a silver-supported, oxalate-intercalated layered cobalt-iron bimetallic hydroxide, denoted as Ag / CoFe-C2O4. 2– -LDH, i.e., the catalyst.

2. The method for preparing the catalyst according to claim 1, characterized in that, In step (1), the soluble cobalt salt is selected from at least one of cobalt chloride, cobalt nitrate, cobalt sulfate, and cobalt oxalate; And / or, the soluble iron salt is selected from at least one of ferric chloride, ferric nitrate, ferric sulfate, and ferric oxalate; And / or, the ammonium salt is selected from at least one of ammonium chloride, ammonium fluoride, and ammonium bromide; And / or, the oxalate is selected from at least one of lithium oxalate, sodium oxalate, and potassium oxalate.

3. The method for preparing the catalyst according to claim 1 or 2, characterized in that, In step (1), the concentration of the soluble cobalt salt in the mixed solution is 0.01-0.5 mol / L, the concentration of the soluble iron salt is 0.002-0.5 mol / L, the concentration of the ammonium salt is 0.1-0.7 mol / L, the concentration of the oxalate is 0.5-8.5 mmol / L, and the concentration of the urea is 0.1-3.5 mol / L.

4. The method for preparing the catalyst according to claim 3, characterized in that, In step (1), the total amount of the soluble cobalt salt and soluble iron salt is in a molar ratio of 1:(1-3) to the ammonium salt; and / or, the molar ratio of the ammonium salt to urea is 1:(1-5).

5. The method for preparing the catalyst according to claim 1, characterized in that, In step (1), the temperature of the hydrothermal reaction is 80-180℃, and the time of the hydrothermal reaction is 4-16 hours.

6. The method for preparing the catalyst according to claim 1, characterized in that, In step (2), the concentration of the aqueous solution of AgNO3 is 0.01-0.5 mol / L.

7. The method for preparing the catalyst according to claim 1, characterized in that, In step (2), the reaction temperature is 20-60℃ and the reaction time is 0.5-12 hours.

8. The method for preparing the catalyst according to claim 1, characterized in that, In step (1), the nickel foam is further cleaned with ethanol, hydrochloric acid and water in sequence before being immersed in the mixed solution.

9. A catalyst, characterized in that, The catalyst is prepared by any one of claims 1-8, wherein the catalyst comprises a nickel foam support and a layered cobalt-iron bimetallic hydroxide supported on the nickel foam support, wherein oxalate ions are interspersed between the layers of the layered cobalt-iron bimetallic hydroxide, and silver nanoparticles are loaded on the layered cobalt-iron bimetallic hydroxide.

10. The application of the catalyst according to claim 9 in the electrolysis of seawater.

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