Preparation method of electrode of electrolytic cell for directly electrolyzing seawater to produce hydrogen, electrolytic cell and electrolysis method

Abstract

The invention provides a preparation method of an electrode of an electrolytic cell for directly electrolyzing seawater to produce hydrogen. The preparation method comprises the following steps: S1, providing a substrate; and S2, growing a conductive diamond layer on the substrate. Or, the preparation method comprises the following steps: S1, providing conductive diamond powder and additive powder, and dispersing the conductive diamond powder and the additive powder in a binder to obtain a mixed solution; and S2, drying the mixed solution in the atmosphere of nitrogen, hydrogen, argon or oxygen, and carrying out hot press molding to obtain the electrode.

Description

Technical Field

[0001] The present invention relates to the field of electrolysis, and particularly to an electrolytic cell for directly electrolyzing seawater to produce hydrogen. Background Art

[0002] Electrolytic hydrogen production, as a source of green hydrogen, is one of the current hotspots in scientific research in the field of electrochemical energy. The mainstream hydrogen production methods include polymer exchange membrane electrolytic hydrogen production (proton exchange membrane electrolytic water hydrogen production PEMWE, anion exchange membrane electrolytic water hydrogen production AEMWE) and alkaline electrolytic water hydrogen production method (ALK). In recent years, direct electrolysis of seawater to produce hydrogen has been a major research hotspot in recent years. However, to avoid electrode poisoning, corrosion, and aging of the electrolytic cell in the mainstream hydrogen production methods, the characteristic of the mainstream electrolysis method is that the water used needs to undergo pretreatment processes such as deionization and de-organic matter, which is essentially an indirect electrolysis of seawater to produce hydrogen. Such processes are costly and cumbersome, which hinders the large-scale application of seawater electrolysis hydrogen production. Summary of the Invention

[0003] Based on the above-mentioned problems, the present application aims to propose an electrode for an electrolytic cell for directly electrolyzing seawater to produce hydrogen, a preparation method thereof, a direct electrolysis seawater hydrogen production electrolytic cell including the electrode, and an electrolysis method.

[0004] A direct electrolysis seawater hydrogen production electrolytic cell includes a first electrode, a diaphragm, and a second electrode. The first electrode, the diaphragm, and the second electrode are sequentially arranged to form an electrode stack. The diaphragm divides the cavity of the electrolytic cell into an independent first cavity and a second cavity. The electrolytic cell has a first-end water inlet and a first-end outlet communicating with the first cavity, and the electrolytic cell has a second-end water inlet and a second-end outlet communicating with the second cavity;

[0005] The electrode material of the first electrode and / or the second electrode includes conductive diamond.

[0006] In one embodiment, the diaphragm is an alkaline electrolytic water diaphragm.

[0007] In one embodiment, the substrate is in a mesh grid shape, a fibrous shape, a needle array shape, or a column array shape.

[0008] In one embodiment, the substrate has through holes or grooves.

[0009] In one embodiment, the first electrode and / or the second electrode includes a base layer and a catalyst layer. The catalyst layer is formed on the surface of the base layer, and the material of the catalyst layer is conductive diamond.

[0010] In one embodiment, the material of the substrate is silicon, or the material of the substrate is a ceramic such as silicon carbide or silicon nitride, or the material of the substrate is at least one of oxide ceramics, nitride ceramics, and carbide ceramics, or the material of the substrate is a single metal or alloy of one or more of aluminum, antimony, chromium, cobalt, copper, gold, iridium, iron, magnesium, molybdenum, titanium, tungsten, nickel, niobium, palladium, platinum, ruthenium, silver, tantalum, vanadium, and zirconium.

[0011] In one embodiment, the oxide ceramic includes at least one of aluminum oxide, zirconium oxide, chromium oxide, titanium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, niobium oxide, tantalum oxide, tungsten oxide, cerium oxide, silicon oxide, tin oxide, bismuth oxide, and yttrium oxide.

[0012] In one embodiment, the nitride ceramic includes at least one of aluminum nitride, silicon nitride, boron nitride, and titanium nitride.

[0013] In one embodiment, the carbide ceramic includes at least one of boron carbide, tungsten carbide, silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, cobalt carbide, and chromium carbide.

[0014] In one embodiment, the thickness of the catalyst layer is 100 nm - 20 μm.

[0015] In one embodiment, the electrode material of the first electrode and / or the second electrode is a conductive diamond composite additive, and the additive is at least one of polytetrafluoroethylene and polyvinylidene fluoride.

[0016] In one embodiment, the first electrode and / or the second electrode is formed by hot pressing a solution in which conductive diamond powder and additive powder are dispersed in a binder.

[0017] In one embodiment, the ratio of the conductive diamond powder to the additive powder is 1 - 10:1.

[0018] In one embodiment, the binder is one or more of polyimide, polycarbonate, waterborne polyurethane, polyacrylic resin, epoxy resin, and urea-formaldehyde resin.

[0019] The beneficial effects of this application are as follows:

[0020] 1. The cost of the supporting system is low, and the complex and expensive pure chemical process of seawater in the existing system is eliminated.

[0021] 2. The preparation of the conductive diamond electrode material uses elements that are not restricted by resources, and its large-scale production cost is low.

[0022] 3. Diamond has corrosion resistance and oxidation resistance. Therefore, the electrode is not oxidized and corroded by oxidizing substances generated at high potentials, and the electrode has a long service life;

[0023] 4. The electrolytic cell can be directly coupled with renewable energy power without the limitation of the electrode voltage of AEM and PEM electrolytic cells (to prevent the dissolution or oxidation-reduction dissolution of metal electrode materials, etc.), making the power system equipment and control connected to the electrolytic cell simple and easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 SEM diagram of the electrode of the electrolytic cell for directly electrolyzing seawater to produce hydrogen in Embodiment A of the present invention.

[0026] Figure 2 TEM diagram of the electrode of the electrolytic cell for directly electrolyzing seawater to produce hydrogen in Embodiment B of the present invention.

[0027] Figure 3 Raman diagram of the electrode of the electrolytic cell for directly electrolyzing seawater to produce hydrogen in Embodiment A of the present invention.

[0028] Figure 4 Raman diagram of the electrode of the electrolytic cell for directly electrolyzing seawater to produce hydrogen in Embodiment B of the present invention.

[0029] Figure 5 Voltage change curve diagram before and after the accelerated durability test of Embodiment 1, Embodiment 3 and the comparative example of the present invention.

[0030] Figure 6 Test procedure diagram of the accelerated durability test of the present invention.

[0031] Figure 7 Structural schematic diagram of the electrolytic cell for directly electrolyzing seawater to produce hydrogen in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] As Figure 7 shown, its structure includes the direct seawater electrolysis hydrogen production electrolytic cell 3 of an embodiment of the present invention. Specifically, it includes a first electrode 4, a diaphragm 5, and a second electrode 6. The first electrode 4, the diaphragm 5, and the second electrode 6 are arranged in sequence to form an electrode laminate. The diaphragm 5 divides the cavity of the electrolytic cell into a first cavity 7 and a second cavity 12. The electrolytic cell has a first-end water inlet 1 and a first-end outlet 8 communicating with the first cavity, and the electrolytic cell has a second-end water inlet 2 and a second-end outlet 11 communicating with the second cavity 12.

[0034] The electrode material of the first electrode 4 and / or the second electrode 6 includes conductive diamond.

[0035] It should be understood that the first electrode / second electrode can be set as a cathode or an anode according to actual needs. The first-end water inlet and the second-end water inlet are used to introduce seawater. The first-end outlet and the second-end outlet can be a hydrogen-end outlet or an oxygen-end outlet according to the setting of the cathode and anode.

[0036] In one embodiment, the diaphragm is an alkaline electrolyzed water diaphragm.

[0037] Example A

[0038] The material of the electrode for the direct seawater electrolysis hydrogen production electrolytic cell in the present invention uses conductive diamond, and its electrode can be a conductive diamond layer grown on a base layer to form a conductive diamond electrode.

[0039] The first electrode and / or the second electrode includes a base layer and a catalyst layer. The catalyst layer is formed on the surface of the base layer, and the material of the catalyst layer is conductive diamond. Further, for example, the material of the base layer is silicon, or the material of the substrate is a ceramic such as silicon carbide or silicon nitride, or the material of the substrate is at least one of oxide ceramics, nitride ceramics, and carbide ceramics, or the material of the substrate is one or more of the elemental metals or alloys of aluminum, antimony, chromium, cobalt, copper, gold, iridium, iron, magnesium, molybdenum, titanium, tungsten, nickel, niobium, palladium, platinum, ruthenium, silver, tantalum, vanadium, and zirconium.

[0040] The present invention provides a preparation method for the above electrode, that is, a preparation method for the electrode of a direct seawater electrolysis hydrogen production electrolytic cell. Specifically, it includes the following steps:

[0041] Step S1:

[0042] Provide a substrate;

[0043] The substrate is the above-mentioned base layer. For example, the material of the base layer is silicon, or the material of the substrate is a ceramic such as silicon carbide or silicon nitride, or the material of the substrate is at least one of oxide ceramics, nitride ceramics, and carbide ceramics, or the material of the substrate is a single metal or alloy of one or more of aluminum, antimony, chromium, cobalt, copper, gold, iridium, iron, magnesium, molybdenum, titanium, tungsten, nickel, niobium, palladium, platinum, ruthenium, silver, tantalum, vanadium, and zirconium.

[0044] In one embodiment, the oxide ceramic includes at least one of aluminum oxide, zirconium oxide, chromium oxide, titanium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, niobium oxide, tantalum oxide, tungsten oxide, cerium oxide, silicon oxide, tin oxide, bismuth oxide, and yttrium oxide.

[0045] In one embodiment, the nitride ceramic includes at least one of aluminum nitride, silicon nitride, boron nitride, and titanium nitride.

[0046] In one embodiment, the carbide ceramic includes at least one of boron carbide, tungsten carbide, silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, cobalt carbide, and chromium carbide.

[0047] For example, the thickness of the substrate (base layer) is 0.25 - 1 mm.

[0048] Step S2:

[0049] Grow a conductive diamond layer on the substrate.

[0050] Grow conductive diamond on the above-mentioned substrate (base layer) to obtain an electrode with a substrate composite conductive diamond.

[0051] In a preferred embodiment, the growth parameters of the conductive diamond layer are as follows: the number of hot wires is 10 - 24, the distance between hot wires is 10 - 17 mm, the distance between the hot wire and the pedestal is 5 - 20 mm, the total flow rate of methane, boron source, and hydrogen is 250 - 500 sccm, where the flow rate ratio of methane to hydrogen is 1 / 50 - 1 / 1000, the flow rate ratio of boron source to hydrogen is 1 / 50 - 1 / 1000, the air pressure is 10 - 40 Torr, the hot wire temperature is 1800 - 2400 degrees Celsius, the pedestal temperature is 500 - 900 degrees Celsius, and the growth time is 2 - 20 h.

[0052] In one embodiment, the thickness of the catalyst layer (i.e., the conductive diamond layer) is 100 nm - 20 μm. Preferably, the thickness of the catalyst layer is 200 - 500 nm.

[0053] The electrode obtained by the above method can be used as the first electrode and / or the second electrode in the above-mentioned direct electrolysis of seawater to hydrogen electrolyzer.

[0054] Example B

[0055] In another embodiment, the material of the electrode for the electrolyzer for directly electrolyzing seawater to produce hydrogen in the present invention is conductive diamond, and the electrode can be an electrode formed by combining conductive diamond with other materials. For example, the electrode material of the first electrode and / or the second electrode is conductive diamond composite additive. Specifically, for example, the first electrode and / or the second electrode are formed by hot pressing a solution in which conductive diamond powder and additive powder are dispersed in a binder.

[0056] The present invention provides a preparation method for the above electrode, that is, a preparation method for the electrode of an electrolyzer for directly electrolyzing seawater to produce hydrogen. Specifically, it includes the following steps:

[0057] Step S1:

[0058] Provide conductive diamond powder and additive powder, disperse them in a binder to obtain a mixed solution.

[0059] For example, the size of the conductive diamond powder is 5nm - 10μm.

[0060] For example, the additive is at least one of polytetrafluoroethylene or polyvinylidene fluoride. The size of the additive powder is 5nm - 10μm.

[0061] In one embodiment, the ratio of the conductive diamond powder to the additive powder is 10 - 1:1. In the above ratio, the conductive diamond powder and the additive powder are dispersed in a binder.

[0062] For example, the binder is one or more of polyimide, polycarbonate, and waterborne polyurethane. In one embodiment, the binder is a 30% waterborne polyurethane solution with a pH of 8.5.

[0063] Step S2:

[0064] Dry the mixed solution in an atmosphere of nitrogen or hydrogen or argon or oxygen, and hot press it into shape to obtain the electrode.

[0065] Preferably, step S2 includes the following steps: dry the mixed solution in an atmosphere of nitrogen or hydrogen or argon or oxygen, and use the heating film pressing method to hot press for 0.2 - 2h at 350 - 500°C and 0.6 - 20Mpa to form the electrode.

[0066] In one embodiment, the thickness of the electrode prepared in this step is 4 - 500μm.

[0067] The electrode obtained in this step is an electrode with a conductive diamond composite additive, which is formed by bonding with an adhesive and hot pressing. The electrode obtained by the above method can be used as the first electrode and / or the second electrode in the direct electrolysis of seawater to hydrogen electrolyzer described above.

[0068] To achieve the drainage and gas conduction functions of the electrode, for example, the electrode (i.e., the first electrode and / or the second electrode) for the direct electrolysis of seawater to hydrogen electrolyzer is a grid-shaped electrode, a fibrous electrode, a needle-like array electrode, a columnar array electrode, a grooved electrode or a perforated electrode.

[0069] Through the preparation method of the above Example A and the obtained electrode, in one embodiment, the electrode is a grid-shaped electrode. For example, a grid-shaped, fibrous, needle-like array, or columnar array substrate is provided, and a conductive diamond catalyst layer is formed on the substrate to obtain a grid-shaped, fibrous, needle-like array, or columnar array electrode with a conductive diamond layer. In another embodiment, the electrode is a grooved electrode. For example, a substrate with grooves is provided, and a conductive diamond catalyst layer is formed on the substrate to obtain a grooved electrode with a conductive diamond layer. In yet another embodiment, the electrode is a perforated electrode. For example, a substrate with through holes is provided, and a conductive diamond catalyst layer is formed on the substrate to obtain a perforated electrode with a conductive diamond layer.

[0070] Among them, the shape of the through hole can be circular, square, V-shaped, irregular, etc.

[0071] To achieve the drainage and gas conduction functions of the electrode, further, the grid porosity of the grid-shaped substrate is 2-80%.

[0072] To achieve the drainage and gas conduction functions of the electrode, further, the number of grooves opened on the substrate with grooves is several, and the grooved area ratio is 2-80%.

[0073] To achieve the drainage and gas conduction functions of the electrode, further, the number of through holes opened on the substrate with through holes is several, and the perforated area ratio is 2-80%. Preferably, the hole pitch of the through hole is 1-5 mm.

[0074] Through the preparation method of the above Example B and the obtained electrode, the conductive diamond powder and the additive powder are dispersed in the binder to obtain a mixed solution, and the mixed solution is injected into a mold and hot pressed. Through the setting of the mold, a grid-shaped, fibrous, needle-like array, or columnar array electrode with a conductive diamond composite additive can be hot pressed, or an electrode with a conductive diamond composite additive having grooves or through holes can be hot pressed.

[0075] The hydrogen production electrolyzer for directly electrolyzing seawater provided by the present invention includes an anode and a cathode, and the anode and / or the cathode is prepared by the preparation method of the electrode for the hydrogen production electrolyzer for directly electrolyzing seawater described in any one of the above.

[0076] The beneficial effects of the hydrogen production electrolyzer for directly electrolyzing seawater of the present invention are as follows:

[0077] 1. The cost of the supporting system is low, and the complex and expensive seawater purification process in the existing system is eliminated.

[0078] 2. The preparation of the conductive diamond electrode material selects elements not restricted by resources, and its large-scale production cost is low.

[0079] 3. Diamond has corrosion resistance and oxidation resistance. Therefore, the electrode is not oxidized and corroded by the oxidizing substances generated at high potentials, and the electrode has a long service life;

[0080] 4. The electrolyzer can be directly coupled with renewable energy power, without the limitation of the electrode voltage of AEM and PEM electrolyzers (to prevent the dissolution or oxidation-reduction dissolution of metal electrode materials, etc.), making the power system equipment and control connected to the electrolyzer simple and easy.

[0081] The hydrogen production electrolyzer for directly electrolyzing seawater can be directly coupled with intermittent renewable energy power, maximizing the utilization of intermittent energy and eliminating the energy consumption and cost of its integration into the grid. At the same time, seawater with extremely large reserves on the earth is used for electrolysis, without threatening fresh water resources. Compared with the above-mentioned indirect electrolysis of seawater to produce hydrogen, direct electrolysis of seawater to produce hydrogen is the most sustainable development direction of green hydrogen.

[0082] The method of directly electrolyzing seawater to produce hydrogen has extremely high requirements for the electrode material of its electrolyzer, which requires it to: couple the instability of intermittent energy to maximize the energy utilization rate of the system; the electrode and other electrolyzer components can withstand the corrosion and degradation of salts and alkalis such as Cl - , OH - , OCl - etc.; the electrode is not poisoned and inactivated by microorganisms and organic substances in seawater, etc. This makes the suitable electrode material should have the important characteristics of electrochemical corrosion resistance, being able to withstand frequent start-stop, and being able to directly oxidize and treat microorganisms and organic substances.

[0083] As one of the most corrosion-resistant materials, conductive diamond has no water quality selectivity in its related electrochemical applications. Compared with the application characteristics of noble metal-coated electrodes and high-entropy alloy electrodes, its application characteristics are that there are no problems of metal corrosion, metal dissolution, and re-dissolution of metal chlorides. At the same time, the lack of chemical adsorption characteristics makes it not poisoned by the adsorption of organic substances / microorganisms, etc. It can be oxidized at a relatively high potential and reduced at a relatively low potential. Such an artificial electrode material that can be applied under a wide range of potential fluctuations can be directly coupled with intermittent renewable energy with a wide range of power, so it is very suitable for directly electrolyzing seawater to produce hydrogen.

[0084] The present invention provides an electrolysis method for an electrolytic cell for directly electrolyzing seawater to produce hydrogen:

[0085] There is provided an electrolytic cell for directly electrolyzing seawater to produce hydrogen, wherein the material of the anode of the electrolytic cell for directly electrolyzing seawater to produce hydrogen is conductive diamond.

[0086] Specifically, the electrolytic cell includes an anode, a diaphragm, and a cathode. The anode, the diaphragm, and the cathode are sequentially arranged to form an electrode laminate. The diaphragm divides the cavity of the electrolytic cell into a first cavity 7 and a second cavity 12. The electrolytic cell has a first-end water inlet 1 and a first-end outlet 8 communicating with the first cavity, and the electrolytic cell has a second-end water inlet 2 and a second-end outlet 11 communicating with the second cavity 12.

[0087] The electrode material of the first electrode 4 and / or the second electrode 6 includes conductive diamond.

[0088] Seawater is introduced into the first cavity 7 and the second cavity 12 of the electrolytic cell for directly electrolyzing seawater to produce hydrogen, and seawater is electrolyzed with a voltage of 1.6 - 2.3V to degrade trace organic substances and microorganisms in the system, and the voltage is intermittently adjusted to 4 - 9V to achieve the purpose of removing the adhesion of organic matter on the electrode surface.

[0089] Specifically, for example, the single-cell electrolysis voltage is increased to 8V within 1 minute, maintained for 20 minutes, decreased to 5V within 1 minute, maintained for 3 minutes, and decreased to the rated working voltage within 1 minute, and then switched to the rated working condition.

[0090] In a preferred embodiment, before directly electrolyzing seawater, alkali is pre-added to precipitate insoluble trace metal hydroxides in seawater, and the pH value of seawater is adjusted to 8 - 14. After seawater is added with alkali to adjust the pH, it is then introduced into the electrolytic cell for electrolysis.

[0091] The following table shows the relationship between the hydrogen production efficiency of the hydrogen production electrolyzer for directly electrolyzing seawater of the present invention and the average voltage of the rated average current. Among them, Example 1 is the result of the hydrogen production electrolyzer for directly electrolyzing seawater using the conductive diamond electrode sheet prepared in Example A under the operating conditions of pH = 10.7. In this example, the dosage of conductive diamond is 4 mg / cm 2 . Example 2 is the result of the hydrogen production electrolyzer for directly electrolyzing seawater using the conductive diamond electrode sheet prepared in Example A under the operating conditions of pH = 11. In this example, the dosage of conductive diamond is 4.08 mg / cm 2 . Example 3 is the result of the hydrogen production electrolyzer for directly electrolyzing seawater using the powder electrode of the conductive diamond composite additive prepared in Example B under the operating conditions of pH = 11.

[0092] In this example, the dosage of conductive diamond is 2.1 mg / cm 2 .

[0093]

[0094] Table 1

[0095] * Calculate the energy efficiency using the thermal neutral voltage of the electrolyzer

[0096] This application provides a comparative example, which is a hydrogen production electrolyzer for directly electrolyzing seawater with an iridium oxide electrode with an iridium loading of 4 mg / cm 2 as the anode, and the rest of the structure is the same as that of Example 1.

[0097] Figure 5 Figure shows the voltage change curves before and after the accelerated durability test at the same current density for Example 1, Example 3 and the comparative example.

[0098] Figure 6 The test procedure for the accelerated durability test is as follows: Record the electrolyzer voltage at a current density of 0.5 A / cm 2 for 0 - 500 - 1000 - 5000 - 10000 - 30000 - 60000 - 100000 times of rapid voltage regulation. The test conditions are: 3.3 V - 10 s, 0.7 V - 20 s, and the regulation time is 3 s.

[0099] As shown Figure 5 by the voltage change curve, although the initial power consumption of the electrolyzer with the iridium oxide electrode in the comparative example is low, serious corrosion inactivation occurs after the voltage cycle of seawater ion poisoning and coupling with renewable energy power. Therefore, under the same conditions, the electrolyzer with the conductive diamond electrode in this application has higher electrolysis stability in directly electrolyzing seawater than the electrolyzer with the iridium oxide electrode.

[0100] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0101] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen, characterized in that: The steps include: S1: Provide substrate; S2: growing a conductive diamond layer on the substrate.

2. The method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to claim 1, characterized in that: The substrate is in a grid shape, a fiber shape, a needle array or a column array.

3. The method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to claim 1, characterized in that: The substrate has a through hole or a groove.

4. The method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to claim 1, characterized in that: The material of the substrate is silicon, or the material of the substrate is ceramics such as silicon carbide and silicon nitride, or the material of the substrate is at least one of oxide ceramics, nitride ceramics, and carbide ceramics, or the material of the substrate is one or more single metals or alloys of aluminum, antimony, chromium, cobalt, copper, gold, iridium, iron, magnesium, molybdenum, titanium, tungsten, nickel, niobium, palladium, platinum, ruthenium, silver, tantalum, vanadium, and zirconium.

5. The electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 4, characterized in that: The oxide ceramic includes at least one of aluminum oxide, zirconium oxide, chromium oxide, titanium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, niobium oxide, tantalum oxide, tungsten oxide, cerium oxide, silicon oxide, tin oxide, bismuth oxide, and yttrium oxide.

6. The electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 4, characterized in that: The nitride ceramic includes at least one of aluminum nitride, silicon nitride, boron nitride and titanium nitride.

7. The electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 4, characterized in that: The carbide ceramic includes at least one of boron carbide, tungsten carbide, silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, cobalt carbide and chromium carbide.

8. The electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 1, characterized in that: The thickness of the conductive diamond layer is 100 nm-20 μm.

9. A method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen, characterized in that: The steps include: S1: providing conductive diamond powder and additive powder, dispersing them in a binder to obtain a mixed solution; S2: drying the mixed solution in an atmosphere of nitrogen, hydrogen, argon or oxygen, and hot pressing to form the mixed solution to obtain the electrode.

10. The method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to claim 1, characterized in that: The S2 comprises: drying the mixed solution in a N2 atmosphere, and using a heated film pressing method to hot press for 0.2-2h under the conditions of 350-500°C and 0.6-20Mpa to obtain the electrode.

11. The method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to claim 1, characterized in that: The thickness of the electrode is 4-500 μm.

12. The method for preparing an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to claim 9, characterized in that: The additive is at least one of polytetrafluoroethylene and polyvinylidene fluoride.

13. The method for preparing an electrode for an electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 9, characterized in that: The ratio of the conductive diamond powder to the additive powder is 1-10:

1.

14. The method for preparing an electrode for an electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 9, characterized in that: The adhesive is one or more of polyimide, polycarbonate, waterborne polyurethane, polyacrylic resin, epoxy resin, and urea-formaldehyde resin.

15. The method for preparing an electrode for an electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 9, characterized in that: The conductive diamond powder has a size of 5nm-10μm.

16. The method for preparing an electrode for an electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 9, characterized in that: The size of the additive powder is 5nm-10μm.

17. A hydrogen production electrolyzer for direct electrolysis of seawater, characterized in that: It comprises an anode and a cathode, and the anode and / or cathode are prepared by the preparation method of an electrode for an electrolytic cell for direct electrolysis of seawater to produce hydrogen according to any one of claims 1 to 16.

18. An electrolysis method for directly electrolyzing seawater to produce hydrogen in an electrolytic cell, characterized in that: Provided is an electrolyzer for producing hydrogen by direct electrolysis of seawater as described in claim 17, further comprising a diaphragm, wherein the anode, the diaphragm and the cathode are arranged in sequence, and the diaphragm divides the cavity of the electrolyzer into a first cavity and a second cavity, and seawater is passed into the first cavity and the second cavity of the electrolyzer for producing hydrogen by direct electrolysis of seawater, and the seawater is electrolyzed at a voltage of 1.6-2.3V, and the voltage is intermittently adjusted to 4-9V.

19. The electrolysis method of the electrolytic cell for producing hydrogen by direct electrolysis of seawater according to claim 18, characterized in that: Before electrolyzing seawater, alkali is pre-added to precipitate insoluble trace metal hydroxides in the seawater and adjust the pH value of the seawater to 8-14.

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