Difunctional electrolyzed water / seawater hydrogen production catalyst, preparation method and application

Abstract

The invention discloses a bifunctional electrolyzed water / seawater hydrogen production catalyst as well as a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: S1, pretreating foamed nickel; s2, putting the pretreated foamed nickel into a reaction kettle filled with a mixed solution, putting the reaction kettle into a drying oven, and carrying out heat preservation reaction to obtain NiMn-MOF; s3, putting the obtained NiMn-MOF into a reaction kettle filled with a selenylation solution, putting the reaction kettle into a drying oven, and carrying out heat preservation reaction to obtain a NiMn-Se precursor; and S4, immersing the obtained NiMn-Se precursor into a deposition solution, carrying out deposition preparation by adopting a cathode potentiostatic deposition method under a three-electrode system, taking out foamed nickel after deposition is finished, cleaning, and carrying out vacuum drying to obtain the NiMn-Se-coated CoMn LDH catalyst. The catalyst disclosed by the invention not only has excellent high-current-density seawater electrolysis hydrogen evolution and oxygen evolution catalytic activity, but also has strong corrosion resistance, and can stably operate in seawater for a long time.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis catalyst technology, specifically to a method for preparing and applying a bifunctional water / seawater electrolysis hydrogen production catalyst. Background Technology

[0002] As people begin to seek renewable energy sources to replace traditional fossil fuels, hydrogen energy, as the ultimate energy carrier with zero carbon emissions, is a core direction for the global energy structure transformation. The scarcity, uneven geographical distribution, and high purification / transportation costs of freshwater resources severely restrict the large-scale and economical production of green hydrogen. In contrast, seawater covers 71% of the Earth's surface, with reserves of up to 1.33 billion cubic kilometers, accounting for 97% of global water resources. It is a natural and ideal hydrogen production feedstock for coastal and offshore areas rich in renewable energy. Direct seawater electrolysis for hydrogen production can completely break free from the constraints of freshwater resources, significantly reducing feedstock costs and infrastructure dependence, opening up a new path for the large-scale production of green hydrogen. Therefore, seawater electrolysis for hydrogen production, by utilizing marine resources, provides a localized hydrogen production solution for coastal areas, islands, and offshore facilities, significantly reducing transportation costs and infrastructure limitations.

[0003] Like traditional water electrolysis, seawater electrolysis involves two half-reactions: the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode. Seawater has a complex environment with a large amount of chloride ions, which severely corrode the catalyst electrodes. Furthermore, during the oxygen evolution reaction at the anode, chloride ions compete to form hypochlorous acid, reducing the Faraday efficiency of seawater electrolysis and consequently decreasing the efficiency of hydrogen production from seawater.

[0004] In traditional water electrolysis, Pt-based and Ru-based materials are commonly used as commercial catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, their high cost limits their large-scale application. Therefore, transition metal materials are often considered as alternatives to noble metal catalysts. Transition metal selenium compounds are not only abundant and inexpensive, but also possess excellent electrocatalytic performance and long-term stability. Because selenium's 3d orbitals have energy levels close to the 3s and 3p orbitals of metals, they facilitate bonding with metal atoms and promote electron transport. The LDH structure provides a large specific surface area, abundant active site exposure, and ion exchange capacity, which is beneficial for reactant transport. Co-based compounds are recognized as highly efficient active centers for OER catalysis. Mn has abundant valence states and can undergo redox reactions during catalysis, potentially participating in or promoting the transformation of reaction intermediates. Simultaneously, the introduction of Mn can effectively modulate the electronic structure of adjacent Co sites. 3+ The Jahn-Teller effect can induce lattice distortion and enhance intrinsic activity.

[0005] Patent CN117987846A discloses a method for preparing NiM-LDH-N / FF and its application. The method involves ultrasonically cleaning and then vacuum drying iron foam. The treated iron foam is then placed in a reactor containing nickel salt, another transition metal salt, hexamethylenetetramine, and methanol for a solvothermal reaction to generate a layered bimetallic hydroxide-iron foam composite. This layered bimetallic hydroxide-iron foam composite is then placed in a reactor containing nickel salt, ammonium chloride, and methanol for a secondary solvothermal reaction to generate NiM-LDH-N / FF. While this method loads LDH onto iron foam, its electrocatalytic activity still needs improvement, and it does not address whether its selectivity and stability in seawater can address chlorine resistance.

[0006] When transition metal materials are used as catalysts, they often exhibit only single hydrogen evolution or oxygen evolution catalytic activity. This leads to different tolerances of the two different anode and cathode water electrolysis catalysts to the electrolyte. Therefore, the preparation of bifunctional water electrolysis catalysts is of great significance.

[0007] CN120006340A discloses the preparation and application of a highly efficient self-supporting bifunctional catalyst for electrolyzing alkaline seawater. The catalyst is a nanosheet-structured FeOOH-NiAl-LDH supported on a nickel foam framework to form a self-supporting and stable structure. The method includes: using a hydrothermal growth method, NiAl-LDH is grown in situ on a nickel foam substrate; then, a room-temperature immersion etching method is used to form a purple-red FeOOH colloid with a mixed solution of sodium hydroxide, water, and potassium ferrate; the prepared NiAl-LDH electrode is immersed and etched in the colloid to obtain the FeOOH-NiAl-LDH electrode. The highly efficient bifunctional catalyst for water electrolysis prepared by this method exhibits good water electrolysis performance and can stably electrolyze alkaline seawater for a long time. However, the electrocatalytic hydrogen evolution and oxygen evolution performance of this method can be further improved, and the influence of chloride ions on the catalyst in various seawater solutions is not discussed, and the corrosion resistance is lacking.

[0008] Therefore, developing low-cost water electrolysis catalysts with excellent catalytic activity and stability, which are inexpensive and easy to prepare, and shifting the electrocatalytic target to abundant seawater resources to reduce freshwater pressure and environmental limitations, is of great significance for the development of water electrolysis / seawater hydrogen production technology. Furthermore, combining hydrogen and oxygen evolution through seawater electrolysis and improving the catalytic activity, selectivity, and stability of the seawater electrolysis system through different active site designs are also crucial. Summary of the Invention

[0009] In view of this, the purpose of this invention is to overcome the problems of high cost of existing precious metal catalysts for water / seawater electrolysis and the limited selectivity and insufficient stability of transition metal catalysts, and to provide a method for preparing a bifunctional water / seawater electrolysis hydrogen production catalyst and its application. The bifunctional water / seawater electrolysis hydrogen production catalyst prepared by this invention can catalyze hydrogen reduction and oxygen oxidation, exhibits high catalytic activity and good stability, and has low preparation cost and simple method, which is conducive to realizing industrial-scale production.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The first objective of this invention is to provide a method for preparing a bifunctional water / seawater electrolysis hydrogen production catalyst, which includes the following steps:

[0012] Step S1. The nickel foam is sequentially immersed in hydrochloric acid, ethanol and water for ultrasonic cleaning, and then vacuum dried to obtain the pretreated nickel foam.

[0013] Step S2. Dissolve nickel nitrate hexahydrate, manganese sulfate monohydrate, and p-phenylenediamine in a mixed solvent of water, ethanol, and N,N-dimethylformamide. After stirring, transfer the solution to a reaction vessel. Place the pretreated nickel foam obtained in step S1 into the reaction vessel, then place the reaction vessel in an oven for heat preservation and reaction. After the reaction is completed, allow it to cool naturally to room temperature. Then wash with ethanol and deionized water, and vacuum dry to obtain nickel-manganese MOF.

[0014] Step S3. Dissolve sodium borohydride, the reducing agent, in deionized water, then mix selenium powder in the solution and stir. Add ethanol solution and stir again to obtain a selenized solution. Transfer the solution to a reaction vessel. The entire preparation process is carried out under a protective atmosphere. Place the nickel-manganese MOF obtained in step S2 into the reaction vessel, then place the reaction vessel in an oven for heat preservation reaction. After the reaction is completed, allow it to cool naturally to room temperature. Then wash with ethanol and deionized water and vacuum dry to obtain the nickel-manganese selenide precursor.

[0015] Step S4. Cobalt nitrate hexahydrate, manganese sulfate monohydrate and ammonium fluoride are dissolved in deionized water and stirred to obtain a deposition solution. The nickel manganese selenide precursor obtained in step S3 is immersed in the deposition solution as a cathode. The deposition is prepared by constant potential deposition under a three-electrode system. The foamed nickel after deposition is taken out, washed with ethanol and water, and then vacuum dried to obtain a bifunctional water electrolysis / seawater hydrogen production catalyst.

[0016] Further, in step S1, the size of the nickel foam is 1-20 × 1-20 cm. 2 The thickness is 0.02-0.2 cm.

[0017] Further, in step S2, the molar concentration ratio of nickel nitrate hexahydrate, manganese sulfate monohydrate and terephthalic acid is 20:(1-50):(1-50):(1-50); the volume ratio of water, ethanol and N,N-dimethylformamide in the mixed solvent is 5:(1-20):(1-30).

[0018] Furthermore, in step S2, the temperature of the reactor is maintained at 100-300℃ for 6-24 hours.

[0019] Furthermore, in step S3, the molar concentration ratio of sodium borohydride to selenium powder is (1-50):20.

[0020] Further, in step S3, the first stirring time is 1-60 min, the second stirring time is 1-60 min, the reactor temperature is 100-300℃, and the holding time is 12-24 h; the protective gas is argon, nitrogen, or an argon-hydrogen mixture.

[0021] Further, in step S4, the molar concentration ratio of cobalt nitrate hexahydrate, manganese sulfate monohydrate and ammonium fluoride is 10:(1-50):(1-50).

[0022] Furthermore, in step S4, the constant potential deposition method uses a saturated calomel electrode as the reference electrode and a platinum sheet as the counter electrode, applies a voltage of -2 to 0.5 V, and has an electrodeposition time of 1 to 10 min.

[0023] The second objective of this invention is to provide a bifunctional water / seawater electrolysis hydrogen production catalyst, which is prepared using the preparation method described in any of the above schemes.

[0024] A third objective of this invention is to provide the application of the aforementioned bifunctional water / seawater electrolysis hydrogen production catalyst in the construction of an electrolyzer for water / seawater electrolysis.

[0025] Compared with existing technologies, the present invention has the following beneficial effects:

[0026] (1) The bifunctional water / seawater electrolysis hydrogen production catalyst of the present invention uses NiMn-MOF stacked sheet structure as the substrate to composite CoMn LDH nanosheets to form a composite structure of large and small sheets, providing abundant exposure of active sites, promoting electrolyte diffusion and bubble desorption, and reducing polarization loss.

[0027] (2) The bifunctional water / seawater electrolysis hydrogen production catalyst of the present invention undergoes surface changes during both hydrogen evolution and oxygen evolution processes. During the hydrogen evolution process under negative voltage, surface selenium is precipitated and reduced, significantly improving the hydrogen evolution catalytic performance and stability of the catalyst; during the oxygen evolution oxidation process under positive voltage, surface oxidation occurs, CoMn LDH is oxidized to CoOOH and Mn3O4, and a large amount of internal Se is precipitated and oxidized to SeO4. 2- Electrostatic adsorption occurs on the catalyst surface, forming a double barrier layer of Mn-O and Se-O, constructing a crucial barrier against chloride ion corrosion and protecting the internal active metals in high-Cl seawater environments. - It maintains stability in the environment while optimizing the electronic properties of the substrate.

[0028] (3) The bifunctional water / seawater electrolysis hydrogen production catalyst of the present invention achieves functional partitioning and close contact through a core-shell structure, promoting interfacial electron transfer and synergistically enhancing overall activity and durability in seawater. The electron-rich properties of Se enhance HER activity, and the composite CoMn LDH optimizes the OER intermediate and lowers the reaction energy barrier. This catalyst exhibits excellent catalytic activity for hydrogen evolution and oxygen evolution in seawater electrolysis. In alkaline seawater, the HER current densities are 10 and 500 mA·cm⁻¹. -2 The overpotentials were only 100.9 and 357.5 mV, and the OER current densities were 10 and 500 mA·cm⁻¹. -2 The overpotentials were 257.7 and 438.5 mV. The current density for the full electrolysis of alkaline seawater was 10 mA·cm⁻¹. -2 With an overpotential of 1.49 mV, it can stably electrolyze for 100 h, showing potential for large-scale industrial application. Attached Figure Description

[0029] Figure 1 The X-ray electron diffraction pattern of the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst in Example 2 is shown below.

[0030] Figure 2 (a) Low-magnification scanning electron microscope image; (b) High-magnification scanning electron microscope image of the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst in Example 2;

[0031] Figure 3 This is a transmission electron microscope image of the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst in Example 2;

[0032] Figure 4 The bifunctional water / seawater electrolysis catalyst in Examples 1-4 was used for the electrolysis of 1.0 mol·L⁻¹ water / seawater. -1 Polarization curve of hydrogen evolution reaction in KOH solution;

[0033] Figure 5 The bifunctional water / seawater electrolysis catalyst in Examples 1-4 was used for the electrolysis of 1.0 mol·L⁻¹ water / seawater. -1 Polarization curve of oxygen evolution reaction in KOH solution;

[0034] Figure 6 The NiMnSe@CoMn LDH-2 water / seawater electrolysis catalyst used in Example 2 was used for electrolysis of 1.0 mol·L⁻¹. -1 KOH, 1.0 mol·L -1 KOH + 0.5 mol·L -1 NaCl and 1.0 mol·L -1 Polarization curve of hydrogen and oxygen evolution reaction in KOH + seawater solution;

[0035] Figure 7 Using the NiMnSe@CoMn LDH-2 water / seawater electrolysis catalyst from Example 2 as the anode and cathode, a total electrolysis of 1.0 mol·L⁻¹ was performed in a two-electrode system. -1 Linear voltammetric curves of KOH + seawater solution;

[0036] Figure 8 Using the NiMnSe@CoMn LDH-2 water / seawater electrolysis catalyst from Example 2 as the anode and cathode, an electrolysis was performed in a two-electrode system at 10 mA·cm⁻¹. -2 Current density for total electrolysis: 1.0 mol·L⁻¹ -1 Chronopotential curve of KOH + seawater solution; Detailed Implementation

[0037] The present invention will be described in detail below through specific embodiments. However, the uses and purposes of these exemplary embodiments are only for illustrating the present invention and do not constitute any limitation on the actual protection scope of the present invention, nor are they intended to limit the protection scope of the present invention to this.

[0038] Example 1

[0039] This embodiment provides a method for preparing NiMn-Se@CoMn LDH-1 water / seawater electrolysis catalyst, the specific steps of which are as follows:

[0040] Step S1. Pre-treat commercially available nickel foam: Cut the purchased 0.1 cm thick nickel foam into 4.0 × 2.0 cm pieces. 2 Then soak in 1 mol·L⁻¹ water. -1 The nickel foam was ultrasonically treated with hydrochloric acid solution, ethanol solution and deionized water for 30 min, and then vacuum dried to obtain pretreated nickel foam, and the oxide layer on the surface of the nickel foam was removed.

[0041] Step S2. Dissolve nickel nitrate hexahydrate, manganese sulfate monohydrate, and terephthalic acid in a molar ratio of 3 mmol:3 mmol:0.45 mmol in a mixed solvent of 10 mL deionized water, 5 mL ethanol, and 15 mL N,N-dimethylformamide. Stir for 2 h to obtain a uniform light green solution and transfer the solution to a 50 mL reaction vessel. Place the pretreated nickel foam obtained in step S1 into the reaction vessel, then place the reaction vessel in an oven and keep it at 150 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash it with ethanol and deionized water, and finally vacuum dry it at 60 °C for 6 h to obtain NiMn-MOF.

[0042] Step S3. Dissolve 100 mg of sodium borohydride reducing agent in 10 mL of deionized water, then mix in 151 mg of selenium powder and stir for 5 min. Then quickly add 30 mL of ethanol solution and stir again for 10 min until the solution turns milky white. Quickly transfer the solution to a 50 mL reaction vessel. The preparation of the selenized solution is carried out under a nitrogen atmosphere. Place the nickel-manganese MOF obtained in step S2 into the aforementioned 50 mL reaction vessel, then place the 50 mL reaction vessel in an oven and keep it at 140 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash with isopropanol and deionized water, and vacuum dry at 60 °C for 6 h to obtain the NiMn-Se precursor.

[0043] Step S4. Dissolve cobalt nitrate hexahydrate and manganese sulfate monohydrate in a molar ratio of 1 mmol:1 mmol:5 mmol in deionized water and stir for 30 min to obtain a deposition solution. Immerse the NiMn-Se precursor obtained in step S3 into the deposition solution as the cathode. In a three-electrode system, using a saturated calomel electrode as the reference electrode and a platinum sheet as the counter electrode, use a constant potential deposition method to prepare the catalyst. The deposition potential is -1.2 V and the deposition time is 1 min. After deposition, the catalyst is taken out and washed with ethanol and water, and then placed in a vacuum drying oven at 60℃ for 6 h to obtain the NiMn-Se@CoMn LDH-1 bifunctional water / seawater electrolysis hydrogen production catalyst.

[0044] Example 2

[0045] This embodiment provides a method for preparing NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst, the specific steps of which are as follows:

[0046] Step S1. Pre-treat commercially available nickel foam: Cut the purchased 0.1 cm thick nickel foam into 4.0 × 2.0 cm pieces. 2 Then soak in 1 mol·L⁻¹ water. -1The nickel foam was ultrasonically treated with hydrochloric acid solution, ethanol solution and deionized water for 30 min, and then vacuum dried to obtain pretreated nickel foam, and the oxide layer on the surface of the nickel foam was removed.

[0047] Step S2. Dissolve nickel nitrate hexahydrate, manganese sulfate monohydrate, and terephthalic acid in a molar ratio of 3 mmol:3 mmol:0.45 mmol in a mixed solvent of 10 mL deionized water, 5 mL ethanol, and 15 mL N,N-dimethylformamide. Stir for 2 h to obtain a uniform light green solution and transfer the solution to a 50 mL reaction vessel. Place the pretreated nickel foam obtained in step S1 into the reaction vessel, then place the reaction vessel in an oven and keep it at 150 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash it with ethanol and deionized water, and finally vacuum dry it at 60 °C for 6 h to obtain NiMn-MOF.

[0048] Step S3. Dissolve 100 mg of sodium borohydride reducing agent in 10 mL of deionized water, then mix in 151 mg of selenium powder and stir for 5 min. Then quickly add 30 mL of ethanol solution and stir again for 10 min until the solution turns milky white. Quickly transfer the solution to a 50 mL reaction vessel. The preparation of the selenized solution is carried out under a nitrogen atmosphere. Place the nickel-manganese MOF obtained in step S2 into the aforementioned 50 mL reaction vessel, then place the 50 mL reaction vessel in an oven and keep it at 140 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash with isopropanol and deionized water, and vacuum dry at 60 °C for 6 h to obtain the NiMn-Se precursor.

[0049] Step S4. Dissolve cobalt nitrate hexahydrate and manganese sulfate monohydrate in a molar ratio of 1 mmol:1 mmol:5 mmol in deionized water and stir for 30 min to obtain a deposition solution. Immerse the NiMn-Se precursor obtained in step S3 into the deposition solution as the cathode. In a three-electrode system, using a saturated calomel electrode as the reference electrode and a platinum sheet as the counter electrode, perform a potentiostatic deposition method to prepare the catalyst. The deposition potential is -1.2 V and the deposition time is 1.5 min. After deposition, remove the catalyst, wash it with ethanol and water, and then dry it in a vacuum drying oven at 60 °C for 6 h to obtain the NiMn-Se@CoMn LDH-2 bifunctional water / seawater electrolysis hydrogen production catalyst.

[0050] Example 3

[0051] This embodiment provides a method for preparing NiMn-Se@CoMn LDH-3 water / seawater electrolysis catalyst, the specific steps of which are as follows:

[0052] Step S1. Pre-treat commercially available nickel foam: Cut the purchased 0.1 cm thick nickel foam into 4.0 × 2.0 cm pieces. 2 Then soak in 1 mol·L⁻¹ water. -1 The nickel foam was ultrasonically treated with hydrochloric acid solution, ethanol solution and deionized water for 30 min, and then vacuum dried to obtain pretreated nickel foam, and the oxide layer on the surface of the nickel foam was removed.

[0053] Step S2. Dissolve nickel nitrate hexahydrate, manganese sulfate monohydrate, and terephthalic acid in a molar ratio of 3 mmol:3 mmol:0.45 mmol in a mixed solvent of 10 mL deionized water, 5 mL ethanol, and 15 mL N,N-dimethylformamide. Stir for 2 h to obtain a uniform light green solution and transfer the solution to a 50 mL reaction vessel. Place the pretreated nickel foam obtained in step S1 into the reaction vessel, then place the reaction vessel in an oven and keep it at 150 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash it with ethanol and deionized water, and finally vacuum dry it at 60 °C for 6 h to obtain NiMn-MOF.

[0054] Step S3. Dissolve 100 mg of sodium borohydride reducing agent in 10 mL of deionized water, then mix 151 mg of selenium powder in the solution and stir for 5 min. Then quickly add 30 mL of ethanol solution and stir again for 10 min until the solution turns milky white. Quickly transfer the solution to a 50 mL reaction vessel. The entire process of preparing the selenized solution is carried out under a nitrogen atmosphere. Place the NiMn-MOF obtained in step S2 into the aforementioned 50 mL reaction vessel, then place the 50 mL reaction vessel in an oven and keep it at 140 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash with isopropanol and deionized water, and finally vacuum dry at 60 °C for 6 h to obtain the NiMn-Se precursor.

[0055] Step S4. Dissolve cobalt nitrate hexahydrate and manganese sulfate monohydrate in a molar ratio of 1 mmol:1 mmol:5 mmol in deionized water and stir for 30 min to obtain a deposition solution. Immerse the NiMn-Se precursor obtained in step S3 into the deposition solution as the cathode. In a three-electrode system, using a saturated calomel electrode as the reference electrode and a platinum sheet as the counter electrode, perform a potentiostatic deposition method to prepare the catalyst. The deposition potential is -1.2 V and the deposition time is 2 min. After deposition, remove the catalyst, wash it with ethanol and water, and then dry it in a vacuum drying oven at 60 °C for 6 h to obtain the NiMn-Se@CoMn LDH-3 bifunctional water / seawater electrolysis hydrogen production catalyst.

[0056] Example 4

[0057] This embodiment provides a method for preparing a NiMn-MOF water / seawater electrolysis catalyst, the specific steps of which are as follows:

[0058] Step S1. Pre-treat commercially available nickel foam: Cut the purchased 0.1 cm thick nickel foam into 4.0 × 2.0 cm pieces. 2 Then soak in 1 mol·L⁻¹ water. -1 The nickel foam was ultrasonically treated with hydrochloric acid solution, ethanol solution and deionized water for 30 min, and then vacuum dried to obtain pretreated nickel foam, and the oxide layer on the surface of the nickel foam was removed.

[0059] Step S2. Dissolve nickel nitrate hexahydrate, manganese sulfate monohydrate, and terephthalic acid in a molar ratio of 3 mmol:3 mmol:0.45 mmol in a mixed solvent of 10 mL deionized water, 5 mL ethanol, and 15 mL N,N-dimethylformamide. Stir for 2 h to obtain a uniform light green solution and transfer the solution to a 50 mL reaction vessel. Place the pretreated nickel foam obtained in step S1 into the reaction vessel, then place the reaction vessel in an oven and keep it at 150 °C for 12 h. After the reaction is completed, allow it to cool naturally to room temperature, then wash it with ethanol and deionized water, and dry it under vacuum at 60 °C for 6 h to obtain the NiMn-MOF catalyst.

[0060] Structural testing:

[0061] The crystal structure of Example 2 was analyzed using X-ray electron diffraction, and the results are as follows: Figure 1 As shown, the diffraction angle 2θ at 33.1°, 44.8°, 50.1°, and 60.4° corresponds to Ni. 0.4 Mn 0.6 In the standard PDF card 70-2851 for Se, corresponding to the (101), (102), (110), and (103) crystal planes, diffraction peaks of CoMn LDH appear at 25.7°, 34.1°, 58.5°, and 61.4°, indicating that the catalyst grown on nickel foam is mainly composed of a large amount of Ni. 0.4 Mn 0.6 It is composed of Se and a small amount of CoMn LDH.

[0062] The morphology of the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst prepared in Example 2 was observed by scanning electron microscopy, and the results are as follows: Figure 2 As shown, the catalyst uses three-dimensional network nickel foam as a support to grow in situ a composite structure of NiMn-Se stacked sheets and hydrotalcite nanosheets, forming a large number of nanopores, which is conducive to the formation of dense microbubbles and improves bubble desorption kinetics.

[0063] The microstructure of the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst prepared in Example 2 was observed by transmission electron microscopy, and the results are as follows: Figure 3 As shown, the catalyst body has a large sheet structure with small-sized disordered nanosheets on top. This structure increases the specific surface area, exposes more active sites, increases electron transport, and improves electrocatalytic activity.

[0064] Performance testing:

[0065] I. Electrochemical performance testing:

[0066] (1) Add 1 mol·L to real seawater -1 KOH was used to remove the resulting white precipitate by filtration, yielding a clear alkaline seawater electrolyte with a concentration of 1.0 mol·L⁻¹. -1 KOH + seawater solution;

[0067] (2) The electrochemical workstation used was a CHI 660e (Shanghai Chenhua Instrument Co., Ltd.). In the three-electrode system, a carbon rod was used as the counter electrode, saturated calomel was used as the reference electrode, and Examples 1-5 were used as the working electrodes. The electrolyte was 1.0 mol·L⁻¹. -1 KOH, 1.0 mol·L -1 KOH + 0.5 mol·L -1 NaCl and 1.0 mol·L -1 KOH + seawater was first activated using cyclic voltammetry, and then the electrochemical performance of hydrogen evolution and oxygen evolution was tested using linear sweep voltammetry at a scan rate of 2 mV·s. -1 .

[0068] Figure 4 The water / seawater electrolysis catalysts of Examples 1-4 were prepared at 1.0 mol·L⁻¹. -1 Linear voltammetric curves of the hydrogen evolution reaction in KOH, and the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst at 10, 100, and 500 mA·cm⁻¹. -2 It has the lowest hydrogen evolution reaction overpotential at current densities, with required overpotentials of 99.5, 222.4, and 394.5 mV, respectively.

[0069] Figure 5 The water / seawater electrolysis catalysts of Examples 1-4 were prepared at 1.0 mol·L⁻¹. -1 Linear voltammetric curves of the oxygen evolution reaction in KOH, and NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst at 10, 100, and 500 mA·cm⁻¹. -2The lowest oxygen evolution reaction overpotentials are found at current densities of 238.9, 307.5, and 416.1 mV, respectively.

[0070] Figure 6 The above are the mixed linear voltammetric curves of the NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst in Example 2 for the hydrogen evolution and oxygen evolution reactions in three electrolytes, compared to 1.0 mol·L⁻¹. -1 KOH, at 1.0 mol·L -1 In KOH + seawater electrolysis, the NiMn-Se@CoMn LDH-2 catalyst exhibited no degradation in hydrogen and oxygen evolution performance, demonstrating high catalytic selectivity and excellent corrosion resistance. During hydrogen evolution, the performance remained stable at 500 mA·cm⁻¹. -2 The required overpotential at the current density is 357.5 mV, and the oxygen evolution process is carried out at 500 mA·cm⁻¹. -2 The required overpotential at the current density is 438.5 mV.

[0071] Table 1. Examples 1-4: Bifunctional water / seawater electrolysis catalyst electrolysis at 1.0 mol·L⁻¹ -1 Comparison of overpotentials in the hydrogen evolution reaction of KOH

[0072] catalyst <![CDATA[10 mA cm -2 Overpotential η 10 (mV) <![CDATA[100 mA cm -2 Overpotential η 100 (mV) <![CDATA[500 mA cm -2 Overpotential η 500 (mV) NiMn-Se@CoMn LDH-1 99.5 222.4 394.5 NiMn-Se@CoMn LDH-2 100.6 218.1 373.6 NiMn-Se@CoMn LDH-3 143.9 269.1 415.7 NiMn-MOF 215.5 319.5 452.5

[0073] Table 2. Examples 1-4: Bifunctional water / seawater electrolysis catalyst electrolysis at 1.0 mol·L⁻¹ -1 Comparison of overpotentials in the oxygen evolution reaction of KOH

[0074] catalyst <![CDATA[10 mA cm -2 Overpotential η 10 (mV) <![CDATA[100 mA cm -2 Overpotential η 100 (mV) <![CDATA[500 mA cm -2 Overpotential η 500 (mV) NiMn-Se@CoMn LDH-1 256.2 354.2 462.4 NiMn-Se@CoMn LDH-2 238.9 307.5 416.1 NiMn-Se@CoMn LDH-3 291.1 375.8 483.3 NiMn-MOF 257.6 344.5 459.3

[0075] Table 3. Comparison of hydrogen evolution and oxygen evolution reaction overpotentials in three different electrolytes for NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst in Example 2.

[0076]

[0077] II. Full Electrolysis of Alkaline Seawater Test:

[0078] In the electrolysis of alkaline seawater test, a two-electrode system was used. The NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst from Example 2 served as both the cathode and anode. The full electrolysis test was conducted using linear sweep voltammetry at a scan rate of 2 mV·s. -1 The stability of the material was tested using a full electrolytic chronopotential test.

[0079] Figure 7Example 2: NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst, dual-electrode full electrolysis, 1.0 mol·L⁻¹ -1 Linear voltammetry curves of KOH + seawater at 10 and 100 mA·cm⁻¹ -2 The required potentials for the current densities are 1.49 V and 1.95 V, respectively.

[0080] Figure 8 Example 2: NiMn-Se@CoMn LDH-2 water / seawater electrolysis catalyst, dual-electrode full electrolysis, 1.0 mol·L⁻¹ -1 The chronopotential curve of KOH + seawater at 10 mA·cm -2 It can operate stably for 100 hours at current density.

[0081] It should be noted that the term "electrolyzed water" generally refers to electrolyzed fresh water. Therefore, "electrolyzed water / seawater" in the instruction manual refers to electrolyzed fresh water or seawater.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made to the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a bifunctional water / seawater electrolysis hydrogen production catalyst, characterized in that, Includes the following steps: Step S1. The nickel foam is sequentially immersed in hydrochloric acid, ethanol and water for ultrasonic cleaning, and then vacuum dried to obtain the pretreated nickel foam. Step S2. Dissolve nickel nitrate hexahydrate, manganese sulfate monohydrate, and p-phenylenediamine in a mixed solvent of water, ethanol, and N,N-dimethylformamide. After stirring, transfer the solution to a reaction vessel. Place the pretreated nickel foam obtained in step S1 into the reaction vessel, then place the reaction vessel in an oven for heat preservation and reaction. After the reaction is completed, allow it to cool naturally to room temperature. Then wash with ethanol and deionized water, and vacuum dry to obtain nickel-manganese MOF. Step S3. Dissolve sodium borohydride, the reducing agent, in deionized water, then mix selenium powder in the solution and stir. Add ethanol solution and stir again to obtain a selenized solution. Transfer the solution to a reaction vessel. The entire preparation process is carried out under a protective atmosphere. Place the nickel-manganese MOF obtained in step S2 into the reaction vessel, then place the reaction vessel in an oven for heat preservation reaction. After the reaction is completed, allow it to cool naturally to room temperature. Then wash with ethanol and deionized water and vacuum dry to obtain the nickel-manganese selenide precursor. Step S4. Cobalt nitrate hexahydrate, manganese sulfate monohydrate and ammonium fluoride are dissolved in deionized water and stirred to obtain a deposition solution. The nickel manganese selenide precursor obtained in step S3 is immersed in the deposition solution as a cathode. The deposition is prepared by constant potential deposition under a three-electrode system. The foamed nickel after deposition is taken out, washed with ethanol and water, and then vacuum dried to obtain a bifunctional water electrolysis / seawater hydrogen production catalyst.

2. The preparation method of the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, The size of the nickel foam mentioned in step S1 is 1-20 × 1-20 cm. 2 The thickness is 0.02-0.2 cm.

3. The preparation method of the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S2, the molar concentration ratio of nickel nitrate hexahydrate, manganese sulfate monohydrate and terephthalic acid is 20:(1-50):(1-50):(1-50); the volume ratio of water, ethanol and N,N-dimethylformamide in the mixed solvent is 5:(1-20):(1-30).

4. The preparation method of the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S2, the temperature of the reactor is maintained at 100-300℃ for 6-24 hours.

5. The preparation method of the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S3, the molar concentration ratio of sodium borohydride to selenium powder is (1-50):

20.

6. The method for preparing the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S3, the first stirring time is 1-60 min, the second stirring time is 1-60 min, the reactor temperature is 100-300℃, and the holding time is 12-24 h; the protective gas is argon, nitrogen, or an argon-hydrogen mixture.

7. The preparation method of the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S4, the molar concentration ratio of cobalt nitrate hexahydrate, manganese sulfate monohydrate and ammonium fluoride is 10:(1-50):(1-50).

8. The method for preparing the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 1, characterized in that, In step S4, the constant potential deposition method uses a saturated calomel electrode as the reference electrode and a platinum sheet as the counter electrode, applies a voltage of -2 to 0.5 V, and performs electrodeposition for 1 to 10 minutes.

9. A bifunctional catalyst for hydrogen production via water / seawater electrolysis, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the bifunctional water / seawater electrolysis hydrogen production catalyst according to claim 9 in the construction of an electrolyzer for water / seawater electrolysis.

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