Electrode for direct electrolysis of seawater and synthesis method therefor

Abstract

The present disclosure relates to the technical field of preparing hydrogen by electrolyzing seawater, and provides an electrode for direct electrolysis of seawater and a synthesis method therefor. The synthesis method comprises: providing a nickel-based electrode substrate; performing surface oxide layer treatment on the nickel-based electrode substrate; electrically depositing iron ions and nickel ions on the treated nickel-based electrode substrate; and performing high-temperature calcination on the nickel-based electrode substrate on which the iron ions and the nickel ions are deposited and phosphate under an inert atmosphere to obtain an electrode for direct electrolysis of seawater. A metal material and a non-metal material are deposited step by step, thereby respectively depositing iron, nickel and phosphorus products on the electrode, and being conductive to promoting an oxygen evolution reaction; moreover, the potential of the electrode can also be adjusted, so that the potential of the electrode is close to chloride ions in seawater to generate a common ion effect, and thus the chloride ions in the seawater are far away from the electrode, thereby avoiding a chlorine evolution reaction, reducing corrosion to the electrode, prolonging the service life of the electrode and improving the stability of the electrode, improving the operation efficiency of a reactor and reducing the unit energy consumption of hydrogen production.

Description

Electrode for direct electrolysis of seawater and synthesis method thereof Technical Field

[0001] The present disclosure belongs to the technical field of hydrogen production by electrolysis of seawater, and particularly relates to an electrode for direct electrolysis of seawater and a synthesis method thereof. Background Art

[0002] Hydrogen production from water electrolysis is a green hydrogen production method, but high energy consumption and freshwater resource depletion are objectively problematic. As renewable energy sources such as wind power are increasingly deployed offshore, the scale of offshore wind power installations is rapidly expanding. However, the challenges of accommodating offshore wind power and the high cost of deep-sea transmission present unprecedented challenges for its development. To address this, coupling wind power with seawater hydrogen production is an ideal path to transition from fossil fuels to green, clean energy. This method can both promote the absorption of renewable energy and alleviate resource allocation issues caused by the massive consumption of freshwater.

[0003] Currently, seawater hydrogen production technologies primarily include indirect seawater hydrogen production and direct seawater hydrogen production. Indirect seawater hydrogen production involves first desalinating seawater to produce high-purity fresh water before producing hydrogen. Essentially, it involves combining seawater desalination with other hydrolysis technologies, such as electrolysis, photolysis, and pyrolysis. However, this method is complex and time-consuming. Direct seawater hydrogen production primarily involves electrolysis or photolysis of water, but this method is technically challenging and remains largely in the experimental stage.

[0004] In addition, the most widely used technology in the field of electrolysis of seawater for hydrogen production is alkaline water electrolysis technology. The electrodes used in this technology are mainly nickel-based metal electrodes. When faced with a complex seawater environment, the high concentration of chloride ions in seawater will cause a chlorine evolution reaction, which in turn causes severe corrosion to the nickel-based metal electrodes, causing electrode inactivation; secondly, the calcium and magnesium ions in seawater are prone to scaling during the electrolysis process. Technical issues

[0005] To address the above problems, a catalytic layer and a scale-inhibiting layer are currently formed on the electrode surface to effectively prevent the deposition of scaling ions in seawater, while catalyzing the hydrogen and oxygen production reactions. However, chlorine evolution reaction still exists, causing corrosion to the electrode, greatly shortening the service life of the electrode, and hindering the promotion and application of direct seawater electrolysis hydrogen production technology. Technical Solutions

[0006] The present disclosure aims to solve at least one of the technical problems existing in the prior art and provide an electrode for direct electrolysis of seawater and a synthesis method thereof.

[0007] In one aspect of the present disclosure, a method for synthesizing an electrode for direct electrolysis of seawater is provided, the method comprising:

[0008] Providing a nickel-based electrode substrate;

[0009] Performing surface oxide layer treatment on the nickel-based electrode substrate;

[0010] Electrodepositing iron ions and nickel ions on the treated nickel-based electrode substrate;

[0011] A nickel-based electrode substrate on which iron ions and nickel ions are deposited and phosphate are calcined at high temperature in an inert atmosphere to obtain an electrode for direct electrolysis of seawater.

[0012] Optionally, the nickel-based electrode substrate has a porous structure.

[0013] Optionally, the nickel-based electrode substrate is made of nickel foam or nickel mesh.

[0014] Optionally, the surface oxide layer treatment of the nickel-based electrode substrate comprises:

[0015] Pickling the nickel-based electrode substrate; or

[0016] The nickel-based electrode substrate is annealed.

[0017] Optionally, the electrodeposition of iron ions and nickel ions on the treated nickel-based electrode substrate comprises:

[0018] The treated nickel-based electrode substrate is used as the working electrode, the platinum plate electrode is used as the auxiliary electrode, and the aqueous solution of iron salt and nickel salt is used as the electrolyte. Current is passed through the electrolyte to deposit the iron ions and nickel ions in the electrolyte on the nickel-based electrode substrate.

[0019] Optionally, when the nickel-based electrode substrate has a pore structure, the iron ions and nickel ions are deposited in the pore structure of the nickel-based electrode substrate.

[0020] Optionally, during the electrodeposition process, the temperature of the electrolyte is 55-65°C and the current density is 30-60 mA / cm 2 and / or,

[0021] The iron salt is ferric nitrate or ferric chloride; and / or,

[0022] The nickel salt is nickel nitrate or nickel chloride.

[0023] Optionally, the phosphate is orthophosphate or acid phosphate.

[0024] Optionally, the high-temperature calcination temperature is 300-350°C, the time is 2-3 hours, and the inert atmosphere is N2.

[0025] In another aspect of the present disclosure, an electrode for direct electrolysis of seawater is provided, wherein the electrode is manufactured using the method described above. Beneficial effects

[0026] The present disclosure provides an electrode for direct electrolysis of seawater and a synthesis method thereof. The synthesis method comprises: providing a nickel-based electrode substrate; treating the surface of the nickel-based electrode substrate with an oxide layer; electro-depositing iron ions and nickel ions on the treated nickel-based electrode substrate; and calcining the nickel-based electrode substrate with the iron ions and nickel ions and phosphate at high temperature under an inert atmosphere to obtain an electrode for direct electrolysis of seawater. By depositing metal materials and non-metallic materials in steps, iron, nickel, and phosphorus products are deposited on the electrode respectively, which is conducive to promoting the oxygen evolution reaction. At the same time, the electrode potential can be adjusted so that the potential of the synthesized nickel-based electrode matches the chloride ions in seawater, generating a common ion effect, so that the chloride ions in the seawater are away from the electrode, avoiding the occurrence of the chlorine evolution reaction, further reducing corrosion to the electrode, and improving the operating life and stability of the electrode in the direct electrolysis of seawater reactor device, thereby improving the operating efficiency of the reactor and reducing key parameters such as the unit energy consumption of hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a flowchart of a method for synthesizing an electrode for direct electrolysis of seawater according to an embodiment of the present disclosure. Modes for Carrying Out the Invention

[0028] To help those skilled in the art better understand the technical solutions of the present disclosure, the present disclosure is further described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a portion of the embodiments of the present disclosure, not all of them. Based on the described embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without the need for creative work are within the scope of protection of the present disclosure.

[0029] As shown in FIG1 , one aspect of the present disclosure provides a method S100 for synthesizing an electrode for direct electrolysis of seawater, comprising the following specific steps S110 to S140:

[0030] S110. Provide a nickel-based electrode substrate.

[0031] It should be noted that the nickel-based electrode substrate of this embodiment can be an electrode substrate with a pore structure, which has a larger comparative area and is conducive to the deposition of metal and non-metal materials.

[0032] In some preferred embodiments, the nickel-based electrode substrate is made of foamed nickel, which has a large number of three-dimensional reticular pore structures, a high specific surface area, good electrical conductivity, and strong corrosion resistance.

[0033] In other preferred embodiments, the nickel-based electrode substrate adopts a nickel mesh having a network structure composed of dense holes, which is conducive to the deposition of metals and non-metals, and has high conductivity and good electrode reaction characteristics.

[0034] It should be further noted that the present embodiment does not impose any specific restrictions on the size of the nickel-based electrode substrate, and can be set according to actual needs. For example, the thickness of the nickel foam or nickel mesh can be set to 0.3 mm to 3.0 mm, and the width can be set to 3 cm to 10 cm.

[0035] S120, performing surface oxide layer treatment on the nickel-based electrode substrate.

[0036] It should be noted that, in this embodiment, the method for treating the oxide layer on the electrode surface is not specifically limited. For example, methods such as pickling, heat treatment, and electrolysis are used to remove the oxide on the electrode surface.

[0037] It should be further explained that after removing the surface oxide layer of the electrode, the treated nickel-based electrode substrate should be cleaned and dried.

[0038] In some preferred embodiments, the nickel-based electrode substrate is pickled, for example, using an acidic solution such as hydrochloric acid or sulfuric acid, wherein the concentration of the acidic solution is preferably 4-6 mol / L.

[0039] In other preferred embodiments, the nickel-based electrode substrate is annealed, for example, in a tube furnace using an atmosphere (90% argon, 10% hydrogen) at a heating rate of 5°C / min to 500°C, and annealing is performed after reaching 500°C.

[0040] S130, electro-depositing iron ions and nickel ions on the treated nickel-based electrode substrate.

[0041] Specifically, a two-electrode system is adopted, the treated nickel-based electrode substrate is used as the working electrode, and the nickel-based electrode substrate is clamped by a platinum wire electrode, and the platinum plate electrode is used as the auxiliary (counter) electrode. Deionized water is added to the reactor, and an appropriate amount of iron salt and nickel salt are added and stirred evenly to form an electrolyte. During the electrodeposition process, the temperature of the reaction liquid is maintained at 55-65°C, and an electric current is passed with a current density of 30-60mA / cm2 so that the iron ions and nickel ions in the electrolyte are deposited on the nickel-based electrode substrate, and the nickel-based electrode substrate with the iron ions and nickel ions deposited is thoroughly washed with deionized water and dried.

[0042] It should be noted that, in this embodiment, there is no specific limitation on nickel salts and iron salts. For example, in some preferred embodiments, the iron salt may be ferric nitrate or ferric chloride; the nickel salt may be nickel nitrate or nickel chloride.

[0043] It should be understood that when the nickel-based electrode substrate has a porous structure, for example, when the nickel-based electrode substrate uses nickel foam or nickel mesh, during the electrodeposition process, iron ions and nickel ions are deposited in the porous structure of the nickel-based electrode substrate.

[0044] In this embodiment, iron ions and nickel ions are deposited on a nickel-based electrode substrate by an electrodeposition method to form a catalyst for the oxygen evolution reaction, thereby promoting the occurrence of the oxygen evolution reaction.

[0045] S140. The nickel-based electrode substrate on which the iron ions and nickel ions are deposited and the phosphate are calcined at a high temperature under an inert atmosphere to obtain an electrode for electrolyzing seawater.

[0046] Specifically, an appropriate amount of phosphate is weighed, and the weighed phosphate and the nickel-based electrode substrate obtained in step S130 are placed in a crucible, and the crucible is placed in a tubular furnace. High-temperature calcination is performed in an inert gas N2 atmosphere, with a heating rate of 5-10°C·min-1, a calcination temperature of 300-350°C, and a calcination time of 2-3h. After the calcination is completed, the electrode can be obtained.

[0047] It should be noted that, in step S140, the phosphate and the nickel-based electrode substrate may be placed in different crucibles, or may be placed in the same crucible, which is not specifically limited.

[0048] It should be further noted that the present embodiment does not specifically limit the type of phosphate, for example, orthophosphate or acid phosphate.

[0049] In some preferred embodiments, the phosphate is orthophosphate, for example, sodium phosphate, potassium phosphate, magnesium phosphate, calcium phosphate, and the like.

[0050] In other preferred embodiments, the phosphate is an acid phosphate, for example, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, sodium monohydrogen phosphate, and the like.

[0051] In this embodiment, through the synergistic effect of gas phase and thermal deposition, phosphate reacts with the nickel-based electrode substrate of step S130 in a high-temperature atmosphere and forms phosphate-related products on the surface of the nickel-based electrode substrate formed in step S130. The phosphate-related products are thermally deposited in the pore structure of the nickel-based electrode. When the nickel-based electrode is used for direct electrolysis of seawater, when the surface of the electrode is close to the chloride ions in the seawater, a common ion effect is generated, which makes the chloride ions in the seawater stay away from the electrode, avoiding the occurrence of chlorine evolution reaction, and promoting oxygen evolution reaction, thereby avoiding corrosion of the electrode; in addition, since the chloride ions are away from the electrode, it can also prevent the electrode from being oxidized by chlorine oxides, thereby increasing the service life of the electrode, which is conducive to the promotion and application of direct water electrolysis hydrogen production technology.

[0052] In another aspect of the present disclosure, an electrode for direct electrolysis of seawater is proposed, which is synthesized using the method described above. Please refer to the above description for the specific process, which will not be repeated here.

[0053] The electrode potential in this embodiment matches the chloride ion potential in seawater. When used for direct electrolysis of seawater, the electrode and the chloride ions in seawater produce a common ion effect, which can keep the chloride ions in seawater away from the electrode, thereby reducing the chlorine evolution reaction, avoiding corrosion to the electrode, and improving the operating life and stability of the electrode in the direct electrolysis of seawater reactor device; in addition, the electrode in this embodiment is also beneficial to promoting the oxygen evolution reaction, improving the efficiency of seawater electrolysis, and further improving the hydrogen production yield of direct seawater electrolysis, thereby improving the operating efficiency of the reactor and reducing the unit energy consumption of hydrogen production.

[0054] The following is a further explanation of the synthesis method of the electrode for direct electrolysis of seawater with reference to several specific examples:

[0055] Example 1

[0056] The synthesis method of the electrode in this example includes the following steps:

[0057] S1. Provide nickel-based electrode substrate:

[0058] A nickel foam roll with a thickness of 0.3 mm was taken and cut into strips with a width of 3 cm using scissors to form a nickel foam sheet, which was used as a nickel-based electrode substrate.

[0059] S2. Treat the surface oxide layer of the nickel-based electrode substrate:

[0060] Add an appropriate amount of 5M hydrochloric acid solution to a beaker, add the nickel foam sheet obtained in step S1, gently stir the nickel foam sheet in the beaker to prevent the nickel foams from sticking to each other, seal the beaker with sealing film, let it stand for a while, and then take it out.

[0061] S3. Electrodepositing iron ions and nickel ions on the treated nickel-based electrode substrate:

[0062] A two-electrode system is used, the working electrode is nickel foam (the working electrode can be clamped by a platinum wire electrode), the auxiliary (counter) electrode is a platinum plate electrode, deionized water is added to the reactor, and after adding appropriate amounts of ferric nitrate and nickel nitrate, it is stirred evenly. During the electrodeposition process, the reaction liquid temperature is maintained at 60°C, and the DC power supply current density is 30mA / cm2. After electrodeposition treatment, iron ions and nickel ions are deposited in the pore structure of the nickel foam electrode matrix, and the deposited nickel-based electrode matrix is ​​thoroughly washed with deionized water and dried.

[0063] S4. The nickel-based electrode substrate on which the iron ions and nickel ions are deposited and the phosphate are calcined at high temperature under an inert atmosphere to obtain an electrode for direct electrolysis of seawater:

[0064] Take two suitable crucibles, weigh an appropriate amount of NaH2PO2·H2O and the nickel-based electrode substrate treated in step S3, and place them in the two crucibles respectively. Put the above two crucibles into a tubular furnace, and calcine the nickel-based electrode substrate and NaH2PO2·H2O in the crucible at high temperature in an inert gas N2 atmosphere. During the calcination stage, maintain a heating rate of 5°C·min-1, a calcination temperature of 300°C, and a calcination time of 2h. After the calcination is completed, the phosphorus product treated in the high-temperature atmosphere is thermally deposited in the pore structure of the foam nickel electrode substrate, and an electrode for direct electrolysis of seawater is obtained.

[0065] Example 2

[0066] The synthesis method of the electrode in this example includes the following steps:

[0067] S1. Provide nickel-based electrode substrate:

[0068] A nickel mesh with a thickness of 1 mm was taken and cut into strips with a width of 5 cm using scissors to form a nickel mesh sheet, which was used as a nickel-based electrode substrate.

[0069] S2. Treat the surface oxide layer of the nickel-based electrode substrate:

[0070] Annealing treatment was performed in a tube furnace using an atmosphere (90% argon, 10% hydrogen) at a heating rate of 5°C / min until the temperature reached 500°C. The treated nickel mesh was cleaned with deionized water and anhydrous ethanol and fully dried.

[0071] S3. Electrodepositing iron ions and nickel ions on the treated nickel-based electrode substrate:

[0072] A two-electrode system is used, with a nickel mesh (clamped by a platinum wire electrode) as the working electrode and a platinum plate electrode as the auxiliary (counter) electrode. Deionized water is added to the reactor, and appropriate amounts of ferric chloride and nickel chloride are added and stirred evenly. During the electrodeposition process, the reaction liquid temperature is maintained at 60°C and the DC power supply current density is 50mA / cm2. Iron ions and nickel ions are deposited in the pore structure of the nickel mesh electrode substrate, and the deposited nickel-based electrode substrate is thoroughly washed with deionized water and dried.

[0073] S4. The nickel-based electrode substrate on which the iron ions and nickel ions are deposited and the phosphate are calcined at high temperature under an inert atmosphere to obtain an electrode for direct electrolysis of seawater:

[0074] Take a suitable crucible, weigh an appropriate amount of Mg₃(PO₄)₂ and the nickel mesh treated in step S3, and place them in a crucible. Place the crucible in a tubular furnace, and calcine the nickel-based electrode substrate and Mg₃(PO₄)₂ in the crucible at high temperature in an inert gas N2 atmosphere. During the calcination stage, maintain a heating rate of 7°C·min-1, a calcination temperature of 320°C, and a calcination time of 2.5h. After the calcination is completed, the phosphorus product treated in the high-temperature atmosphere is thermally deposited in the pore structure of the nickel mesh electrode substrate, thereby obtaining an electrode for direct electrolysis of seawater.

[0075] Example 3

[0076] The synthesis method of the electrode in this example includes the following steps:

[0077] S1. Provide nickel-based electrode substrate:

[0078] A nickel mesh with a thickness of 3 mm was taken and cut into strips with a width of 10 cm using scissors to form a nickel mesh sheet, which was used as a nickel-based electrode substrate.

[0079] S2. Treat the surface oxide layer of the nickel-based electrode substrate:

[0080] Add an appropriate amount of 5M hydrochloric acid solution to a beaker, put in the nickel mesh obtained in step S1, gently stir the nickel mesh in the beaker to prevent the nickel mesh from sticking to each other, seal the beaker with sealing film, let it stand for treatment, and then take it out.

[0081] S3. Electrodepositing iron ions and nickel ions on the treated nickel-based electrode substrate:

[0082] A two-electrode system is used, with a nickel mesh (clamped by a platinum wire electrode) as the working electrode and a platinum plate electrode as the auxiliary (counter) electrode. Deionized water is added to the reactor, and appropriate amounts of ferric nitrate and nickel chloride are added and stirred evenly. During the electrodeposition process, the reaction liquid temperature is maintained at 60°C and the DC power supply current density is 60mA / cm2. Iron ions and nickel ions are deposited in the pore structure of the nickel mesh electrode substrate, and the deposited nickel-based electrode substrate is thoroughly washed with deionized water and dried.

[0083] S4. The nickel-based electrode substrate on which the iron ions and nickel ions are deposited and the phosphate are calcined at high temperature under an inert atmosphere to obtain an electrode for direct electrolysis of seawater:

[0084] Take two suitable crucibles, weigh and place an appropriate amount of KH₂PO₄ and the nickel mesh treated in step S3, and place them in the two crucibles respectively. Place the above two crucibles in a tubular furnace, and in an inert gas N2 atmosphere, calcine the nickel-based electrode substrate and KH₂PO₄ in the crucible at a high temperature. The heating rate is 10°C·min-1, the calcination temperature is 350°C, and the calcination time is 3h. After the calcination is completed, the phosphorus product treated in the high-temperature atmosphere is thermally deposited in the pore structure of the nickel mesh electrode substrate, and an electrode for direct electrolysis of seawater is obtained.

[0085] The present disclosure proposes an electrode for direct electrolysis of seawater and a synthesis method thereof, which has the following beneficial effects compared to the existing technology: the present disclosure deposits metal materials and non-metallic materials in steps to achieve the deposition of iron, nickel and phosphorus products on the electrode respectively, thereby promoting the oxygen evolution reaction; at the same time, it also adopts a gas phase method and a synergistic effect of thermal deposition to make phosphate react and deposit phosphorus products on the electrode, so as to adjust the potential of the electrode, so that the potential of the synthesized nickel-based electrode is close to that of chloride ions in seawater, thereby avoiding the occurrence of chlorine evolution reaction, further reducing corrosion to the electrode, and improving the operating life and stability of the electrode in the direct electrolysis of seawater reactor device, thereby improving the operating efficiency of the reactor operation, reducing key parameters such as the unit energy consumption of hydrogen production, and facilitating the promotion of direct electrolysis of seawater hydrogen production technology.

[0086] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A method for synthesizing an electrode for direct electrolysis of seawater, characterized in that: The synthesis method comprises: Providing a nickel-based electrode substrate; Performing surface oxidation layer treatment on the nickel-based electrode substrate; Electrodepositing iron ions and nickel ions on the treated nickel-based electrode substrate; A nickel-based electrode substrate on which iron ions and nickel ions are deposited and phosphate are calcined at high temperature in an inert atmosphere to obtain an electrode for direct electrolysis of seawater.

2. The synthesis method according to claim 1, characterized in that The nickel-based electrode substrate has a porous structure.

3. The synthesis method according to claim 2, characterized in that The nickel-based electrode substrate is made of foam nickel or nickel mesh.

4. The synthesis method according to any one of claims 1 to 3, characterized in that The step of performing surface oxide layer treatment on the nickel-based electrode substrate comprises: Pickling the nickel-based electrode substrate; or The nickel-based electrode substrate is annealed.

5. The synthesis method according to any one of claims 1 to 3, characterized in that The electro-depositing of iron ions and nickel ions on the treated nickel-based electrode substrate comprises: The treated nickel-based electrode substrate is used as the working electrode, the platinum plate electrode is used as the auxiliary electrode, and the aqueous solution of iron salt and nickel salt is used as the electrolyte. Current is passed through the electrolyte to deposit the iron ions and nickel ions in the electrolyte on the nickel-based electrode substrate.

6. The synthesis method according to claim 5, characterized in that When the nickel-based electrode substrate has a pore structure, iron ions and nickel ions are deposited in the pore structure of the nickel-based electrode substrate.

7. The synthesis method according to claim 5, characterized in that During the electrodeposition process, the temperature of the electrolyte is 55-65°C and the current density is 30-60 mA / cm 2 and / or, The iron salt is ferric nitrate or ferric chloride; and / or, The nickel salt is nickel nitrate or nickel chloride.

8. The synthesis method according to any one of claims 1 to 3, characterized in that The phosphate is orthophosphate or acid phosphate.

9. The synthesis method according to any one of claims 1 to 3, characterized in that The high temperature calcination temperature is 300-350°C, the time is 2-3 hours, and the inert atmosphere is N2.

10. An electrode for direct electrolysis of seawater, characterized in that: The electrode is prepared by the synthesis method according to any one of claims 1 to 9.

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