Method for electrolytic hydrogen production by adopting seawater electrolytic hydrogen production device

Abstract

The invention relates to a method for electrolytic hydrogen production by adopting a seawater electrolytic hydrogen production device. The method comprises the following steps: electrolyzing seawater in the electrolytic hydrogen production device provided with a modified forward osmosis membrane; the modified forward osmosis membrane comprises a base membrane and a composite layer covering the surface of the base membrane, the composite layer contains hydrophilic organic silicon groups substituted by aromatic hydrocarbon groups; the surface of the base membrane contains active groups, and the active groups comprise one or more of carboxyl, amido, hydroxyl, acetic acid group, acylamino, amino, aldehyde group and carbonyl; the base membrane and the composite layer are connected through a chemical grafting reaction between the modified hydrophilic organic silicon group and the active group. According to the method, the two processes of water separation and water electrolysis are integrated in the same device, the method is simple and easy to implement, the maintenance and operation cost is low, the efficiency of direct electrolysis of seawater for hydrogen production is high, and the energy consumption is low.

Description

Technical Field

[0001] The present disclosure relates to the field of hydrogen production by water electrolysis, and in particular, to a method for producing hydrogen by electrolysis using a seawater electrolysis hydrogen production device. Background Art

[0002] Hydrogen is a substance with a wide range of sources, clean and carbon-free, flexible and efficient, and rich application scenarios. It carries the dual attributes of energy and raw materials. It has a deep application foundation in the industrial field and is rapidly expanding into the fields of electricity, construction, transportation, steel, etc. A large amount of water is required in the process of hydrogen production by electrolysis of water. In order to avoid the occurrence of side reactions during the electrolysis process, pure water is usually required to be supplemented, which further increases the actual water consumption. Therefore, hydrogen production by electrolysis of water from renewable energy is one of the most promising low-carbon and high-purity hydrogen production technology directions.

[0003] Seawater accounts for more than 97% of the earth's water resources, and the calorific value of hydrogen contained in it is 9,000 times the total amount of fossil fuels on the earth. It has a unique advantage in realizing large-scale renewable energy electrolysis of water to produce hydrogen. However, in addition to high energy consumption, seawater electrolysis of hydrogen faces additional huge challenges brought by the complex chemical environment of seawater, such as catalyst contamination and deactivation, anode chlorine oxidation side reactions and corrosion. Traditional seawater electrolysis of hydrogen uses reverse osmosis, forward osmosis and other methods to desalinate seawater and combine it with existing water electrolysis hydrogen production systems.

[0004] Prior art (CN114000163A) discloses a system for producing hydrogen by electrolysis of saline wastewater, including an electrolyzer, a gas-liquid separator, a water preheater, an electrolyte heat exchanger, an electrolyte secondary heat exchanger, and a forward osmosis system. However, the technical system is complex in design, occupies a large area, and has high maintenance and operating costs; in addition, the electrolysis hydrogen production method requires the use of a forward osmosis membrane to desalinate the saline wastewater, and then use the desalinated water as water for the electrolysis system. From a system perspective, it is not possible to achieve direct electrolysis of saline wastewater for hydrogen production, and the system needs to pass through a heat exchanger for heat exchange many times, resulting in large overall energy losses and poor economic efficiency. Therefore, a method suitable for direct electrolysis of seawater for hydrogen production is urgently needed. Summary of the invention

[0005] The purpose of the present disclosure is to provide a method for producing hydrogen by electrolysis using a seawater electrolysis hydrogen production device. The method realizes the integration of the two processes of water separation and water electrolysis in the same device. The method is simple and easy to operate, with low maintenance and operation costs, and the direct seawater electrolysis hydrogen production efficiency is high and the energy consumption is low.

[0006] In order to achieve the above-mentioned purpose, the present disclosure provides a method for producing hydrogen by electrolysis using a seawater electrolysis hydrogen production device, the method comprising: electrolyzing seawater in an electrolysis hydrogen production device provided with a modified forward osmosis membrane; wherein the modified forward osmosis membrane comprises a base membrane and a composite layer covering the surface of the base membrane; the composite layer contains a hydrophilic organosilicon group substituted with an aromatic hydrocarbon group; the surface of the base membrane contains active groups, and the active groups include one or more of a carboxyl group, an amine group, a hydroxyl group, an acetate group, an amide group, an amino group, an aldehyde group and a carbonyl group; the base membrane and the composite layer are connected by a chemical grafting reaction between the modified hydrophilic organosilicon group and the active group.

[0007] Optionally, the electrolytic hydrogen production device includes an anode reaction unit, a cathode reaction unit and a partition; in the anode reaction unit, an anode catalyst layer, an anode plate, a first electrolyte tank, a first forward osmosis membrane and a first seawater tank are sequentially arranged in a direction away from the first surface of the partition; an oxygen outlet is arranged on the side wall of the first electrolyte tank; in the cathode reaction unit, a cathode catalyst layer, a cathode plate, a second electrolyte tank, a second forward osmosis membrane and a second seawater tank are sequentially arranged in a direction away from the second surface of the partition; a hydrogen outlet is arranged on the side wall of the second electrolyte tank; wherein the first forward osmosis membrane and the second forward osmosis membrane are each independently the modified forward osmosis membrane.

[0008] Optionally, the method includes: S1, connecting the anode plate to the positive electrode of the power supply, and connecting the cathode plate to the negative electrode of the power supply; S2, under the action of the osmotic pressure difference on both sides of the first forward osmosis membrane, water in seawater migrates from the first seawater tank to the first electrolyte tank, and performs a first electrolysis under the catalytic action of the anode catalyst layer; under the action of the osmotic pressure difference on both sides of the second forward osmosis membrane, water in seawater migrates from the second seawater tank to the second electrolyte tank, and performs a second electrolysis under the catalytic action of the cathode catalyst layer.

[0009] Optionally, the electrolysis conditions include: voltage of 1.2-2.3V, electrolysis time of 100-500h, current density of 300-400mA / cm 2 .

[0010] Optionally, the aromatic hydrocarbon group is selected from aromatic hydrocarbon groups having 6 to 12 carbon atoms; the hydrophilic silicone group is selected from one or more of an active polyether silicone group, a polydimethylsiloxane group, a polymethyl hydrogen-(dimethyl)siloxane group, a terminal hydroxyl polydimethylsiloxane group and an aminoethylaminopropyl polysiloxane group;

[0011] Preferably, the aromatic hydrocarbon group is selected from one or more of o-xylyl, m-xylyl, p-xylyl, 1,3,5-triaminophenyl, 1,2,4-triaminophenyl and 2,4-diaminotolyl;

[0012] The base film is selected from cellulose acetate film and / or polyamide film; the thickness of the base film is 0.01-0.1 mm.

[0013] Optionally, the thickness of the first forward osmosis membrane and the second forward osmosis membrane is independently 0.01-0.15 mm; the tolerable pH value of the first forward osmosis membrane and the second forward osmosis membrane is independently 1-14; the tolerable temperature of the first forward osmosis membrane and the second forward osmosis membrane is independently 20-70°C; the contact angle of the first forward osmosis membrane and the second forward osmosis membrane with water is independently 5-60°; the permeability of impurity ions within 72 hours of the first forward osmosis membrane and the second forward osmosis membrane is independently 0.005-0.08‰.

[0014] Optionally, the anode catalyst layer contains an anode catalyst, which is selected from one or more of iron, cobalt, nickel, palladium, platinum, rhodium and ruthenium; the cathode catalyst layer contains a cathode catalyst, which is selected from one or more of tin, platinum, molybdenum, titanium disulfide, molybdenum disulfide and tin oxide.

[0015] Optionally, the anode catalyst layer and the cathode catalyst layer are each independently a porous mesh structure; the thickness of the anode catalyst layer and the cathode catalyst layer are each independently 0.2-5 mm.

[0016] Optionally, the first electrolyte tank and the second electrolyte tank are each independently provided with a through hole for allowing the electrolyte to contact the first forward osmosis membrane and the second forward osmosis membrane respectively; the electrolyte contains one or more of potassium hydroxide, sodium hydroxide and cesium hydroxide, and the concentration of the electrolyte is higher than the concentration of the seawater.

[0017] Optionally, the method comprises: electrolyzing the preheated seawater in an electrolytic hydrogen production device provided with the modified forward osmosis membrane; the temperature of the preheated seawater is 40-60°C.

[0018] Through the above technical solution, the present disclosure provides a method for electrolyzing hydrogen using a seawater electrolysis hydrogen production device, in which water is electrolyzed to produce hydrogen in an electrolysis hydrogen production device provided with a modified forward osmosis membrane. By providing the modified forward osmosis membrane, the traditional water separation system and the water electrolysis system can be integrated into the same device, and the structure is more compact and intensive, which greatly improves the efficiency of electrolysis hydrogen production and reduces the energy consumption of the seawater hydrogen production process. In addition, the modified forward osmosis membrane has excellent alkali resistance, heat resistance and rigidity, has a large water flux and can effectively prevent the diffusion of impurity ions.

[0019] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0021] Figure 1 It is a schematic structural diagram of the seawater electrolysis hydrogen production device disclosed in the present invention.

[0022] Description of Reference Numerals

[0023] 1 first seawater tank 2 first forward osmosis membrane 3 first electrolyte tank 4 anode plate

[0024] 5 anode catalyst layer 6 separator 7 cathode catalyst layer 8 cathode plate

[0025] 9 second electrolyte tank 10 second forward osmosis membrane 11 second seawater tank 12 fastening bolt through hole

[0026] 13 Hydrogen outlet 14 Oxygen outlet DETAILED DESCRIPTION

[0027] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0028] The present disclosure provides a method for producing hydrogen by electrolysis using a seawater electrolysis hydrogen production device, the method comprising: electrolyzing seawater in the electrolysis hydrogen production device provided with a modified forward osmosis membrane;

[0029] Wherein, the modified forward osmosis membrane comprises a base membrane and a composite layer covering the surface of the base membrane;

[0030] The composite layer contains hydrophilic organosilicon groups substituted with aromatic hydrocarbon groups; the surface of the base film contains active groups, which include one or more of carboxyl groups, amine groups, hydroxyl groups, acetate groups, amide groups, amino groups, aldehyde groups and carbonyl groups;

[0031] The base film and the composite layer are connected through a chemical grafting reaction between the modified hydrophilic organic silicon group and the active group.

[0032] In the present disclosure, the method of the present disclosure performs water electrolysis to produce hydrogen in an electrolytic hydrogen production device provided with a modified forward osmosis membrane. By providing the modified forward osmosis membrane, the traditional water separation system and the water electrolysis system can be integrated into the same device, and the structure is more compact and intensive, which greatly improves the efficiency of electrolytic hydrogen production and reduces the energy consumption of the seawater hydrogen production process. In addition, the modified forward osmosis membrane has excellent alkali resistance, heat resistance and rigidity, has a large water flux and can effectively prevent the diffusion of impurity ions. In the method of the present disclosure, water in seawater spontaneously migrates to the alkaline electrolyte through the modified forward osmosis membrane, and an electrolysis reaction of water occurs on the alkaline electrolyte side.

[0033] The modified forward osmosis membrane used in the disclosed method has a double-layer structure of a base membrane and a composite layer covering the surface of the base membrane. The hydrophilic organosilicon group substituted by an aromatic hydrocarbon group is connected to the active group on the surface of the base membrane through a chemical grafting reaction, so that it has excellent alkali resistance, heat resistance, and rigidity, and has a large water flux and can effectively prevent the migration of impurity ions. Among them, the aromatic hydrocarbon group can improve the heat resistance and rigidity of the forward osmosis membrane; the bond energy of the silicon oxygen bond in the hydrophilic organosilicon group is large, so that the modified forward osmosis membrane has excellent alkali resistance, the silicon atom has a large volume and a large free volume in the spatial structure, which can make the modified forward osmosis membrane have a large water flux; in addition, the main chain of the hydrophilic organosilicon is an inorganic structure containing a silicon oxygen bond, and the side chain part is mainly an organic group, so it has the dual properties of inorganic and organic substances at the same time, so that the modified forward osmosis membrane can effectively prevent the diffusion and migration of ions.

[0034] In one embodiment of the present disclosure, Figure 1 As shown, the electrolytic hydrogen production device includes an anode reaction unit, a cathode reaction unit and a partition 6; in the anode reaction unit, an anode catalyst layer 5, an anode plate 4, a first electrolyte tank 3, a first forward osmosis membrane 2 and a first seawater tank 1 are sequentially arranged in a direction away from the first surface of the partition 6; an oxygen outlet 14 is arranged on the side wall of the first electrolyte tank 5; in the cathode reaction unit, a cathode catalyst layer 7, a cathode plate 8, a second electrolyte tank 9, a second forward osmosis membrane 10 and a second seawater tank 11 are sequentially arranged in a direction away from the second surface of the partition 6; a hydrogen outlet 13 is arranged on the side wall of the second electrolyte tank 9; wherein, the first forward osmosis membrane and the second forward osmosis membrane are each independently the modified forward osmosis membrane.

[0035] In the present disclosure, the device for electrolyzing hydrogen adopts a symmetrical structure, and a partition is used to separate the anode reaction unit and the cathode reaction unit, and at the same time, the hydrogen and oxygen generated by the electrolysis of water can be separated well. In the present disclosure, the partition can be made of conventional materials in the art, specifically, it can be a flexible plastic, for example, it can be one of polyethylene, polyvinyl chloride and polypropylene.

[0036] In one embodiment of the present disclosure, the method comprises:

[0037] S1, connecting the anode plate 4 to the positive electrode of the power supply, and connecting the cathode plate 8 to the negative electrode of the power supply;

[0038] S2. Under the action of the osmotic pressure difference on both sides of the first forward osmosis membrane, water in the seawater migrates from the first seawater tank 1 to the first electrolyte tank 3, and performs a first electrolysis under the catalytic action of the anode catalyst layer 5;

[0039] Under the action of the osmotic pressure difference on both sides of the second forward osmosis membrane, the water in the seawater migrates from the second seawater tank 11 to the second electrolyte tank 9, and the second electrolysis is carried out under the catalytic action of the cathode catalyst layer 7. In the above embodiment, the material of the anode plate and the cathode plate can be a conductive material conventionally used by technicians in this field, such as stainless steel, and through holes for electrolyte diffusion are respectively provided on the anode plate and the cathode plate to further promote the electrolysis of water. The present invention does not impose a specific restriction on the number of through holes, as long as the electrolyte can be fully diffused between the first electrolyte tank and the anode catalyst layer, and between the second electrolyte tank and the cathode catalyst layer. For example, it can be 1-500 / m 2 .

[0040] In one embodiment of the present disclosure, the first electrolyte tank 3 and the second electrolyte tank 9 are each independently provided with a through hole for allowing the electrolyte to contact the first forward osmosis membrane and the second forward osmosis membrane respectively; in the above embodiment, the through hole helps the electrolyte to fully contact the modified forward osmosis membrane to generate an osmotic pressure difference on both sides of the modified osmosis membrane to achieve spontaneous migration of water. According to the present invention, the electrolyte is an alkaline electrolyte, which may contain an inorganic base. In one embodiment of the present disclosure, the electrolyte contains one or more of potassium hydroxide, sodium hydroxide and cesium hydroxide, and the concentration of the electrolyte is higher than the concentration of the seawater. In the above embodiment, the concentration of the electrolyte is higher than the concentration of seawater, which further promotes the migration of water in the seawater to the first electrolytic tank through the first forward osmosis membrane, or to the second electrolytic tank through the second forward osmosis membrane.

[0041] In this disclosure, Figure 1 As shown, along the direction from the first seawater tank 1 to the second seawater tank 11, fastening bolt through holes 12 are provided on the first seawater tank 1, the first electrolyte tank 3, the second electrolyte tank 9 and the second seawater tank 11, and the fastening bolt through holes are used to pass bolts to fasten the whole device. The number of fastening bolt through holes can be an even number, such as 2, 4, or 6.

[0042] According to the present disclosure, the catalyst contained in the anode catalyst layer 5 is an anode catalyst well known to those skilled in the art. In a preferred embodiment of the present disclosure, the anode catalyst is selected from one or more of iron, cobalt, nickel, palladium, platinum, rhodium and ruthenium.

[0043] According to the present disclosure, the catalyst contained in the cathode catalyst layer 7 is a cathode catalyst well known to those skilled in the art, and the cathode catalyst layer 7 contains a cathode catalyst, and the cathode catalyst is selected from one or more of tin, platinum, molybdenum, titanium disulfide, molybdenum disulfide and tin oxide. In the above embodiment, the anode catalyst layer 5 and the cathode catalyst layer 7 can each independently be a porous mesh structure; the thickness of the anode catalyst layer 5 and the cathode catalyst layer 7 is each independently 0.2-5mm, preferably 0.5-2mm.

[0044] In the present disclosure, the voltage and time of the electrolysis can vary within a wide range. In one embodiment of the present disclosure, the conditions of the electrolysis include: a voltage of 1.2-2.3 V, preferably 1.5-2.0 V; an electrolysis time of 100-500 h, preferably 168-386 h; a current density of 300-400 mA / cm 2 , preferably 350-380mA / cm 2 In the present disclosure, the electrolysis rate of water in the anode reaction unit and the cathode reaction unit and the rate of water migration from the seawater side to the electrolyte side can be controlled to be equal by controlling the magnitude of the current density. When the voltage, time and current density of the electrolysis are within the range of the above-mentioned embodiment, the electrolysis reaction rate is appropriate, the electrolysis reaction process is stable, and the hydrogen production is high.

[0045] In the present disclosure, the number of carbon atoms of the aromatic hydrocarbon group can vary within a wide range. In one embodiment of the present disclosure, the aromatic hydrocarbon group is selected from aromatic hydrocarbon groups with 6-12 carbon atoms, preferably aromatic hydrocarbon groups with 6-9 carbon atoms; the hydrophilic silicone group is well known to those skilled in the art, preferably selected from one or more of an active polyether silicone group, a polydimethylsiloxane group, a polymethyl hydrogen-(dimethyl)siloxane group, a terminal hydroxyl polydimethylsiloxane group and an aminoethyl iminopropyl polysiloxane group. In a preferred embodiment of the present disclosure, the aromatic hydrocarbon group is selected from one or more of o-xylyl, m-xylyl, p-xylyl, 1,3,5-triaminophenyl, 1,2,4-triaminophenyl and 2,4-diaminotolyl.

[0046] In one embodiment of the present disclosure, the base film is selected from one of cellulose acetate film and / or polyamide film. In the above embodiment, after the base film is activated, the chemical bonds on the surface of the base film are broken to form active groups, for example, one or more of carboxyl groups, amine groups, hydroxyl groups and acetate groups. The base film can also be a composite film, which is made of two or more materials. The composite film includes a separation layer and a porous support layer. The material of the separation layer is selected from one or more of aromatic polyamide, piperazine amide, propylene-alkyl polyamide, condensed urea, furfuryl alcohol, trihydroxyethyl isocyanate and metaphenylenediamine, and the material of the porous support layer is one or more of non-woven fabrics, polysulfone, polypropylene and polyacrylonitrile.

[0047] In a specific embodiment of the present disclosure, the composite layer is covered on at least one main surface of the base film. Preferably, the composite layer includes a first composite layer and a second composite layer. The first composite layer is covered on the first main surface of the base film, and the second composite layer is covered on the second main surface of the base film. The first main surface and the second main surface refer to two opposite surfaces in the thickness direction of the base film.

[0048] In the present disclosure, the thickness of the base film can vary within a wide range. In one embodiment of the present disclosure, the thickness of the base film can be 0.01-0.1 mm, preferably 0.01-0.05 mm; when the thickness of the base film is within the range of the present disclosure, the thickness is appropriate.

[0049] In the present disclosure, the thickness of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 can vary within a wide range. In one embodiment of the present disclosure, the thickness of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 are independently 0.01-0.15 mm, preferably 0.02-0.1 mm; when the thickness of the first forward osmosis membrane and the second forward osmosis membrane is within the range of the present disclosure, the electrolysis reaction of water can be further promoted.

[0050] In the present disclosure, the pH tolerance, temperature tolerance, and water migration rate of the first forward osmosis membrane and the second forward osmosis membrane can vary within a large range. In one embodiment of the present disclosure, the pH tolerance of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 is independently 1-14, the temperature tolerance of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 is independently 20-70°C, the water migration rate of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 is independently 0.01-0.5gH2O / g KOH / min, the contact angle of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 with water is independently 5-60°, and the permeability of impurity ions within 72h of the first forward osmosis membrane 2 and the second forward osmosis membrane 10 is independently 0.005-0.08‰.

[0051] In the present disclosure, the pH value of the forward osmosis membrane tolerance is measured by the following experimental method: the forward osmosis membrane is immersed in a sodium hydroxide / hydrochloric acid solution with different pH values ​​for 24 hours, and then rinsed with pure water. The water migration rate of the forward osmosis membrane before and after immersion is measured. If the change in the water migration rate of the forward osmosis membrane before and after immersion exceeds 5%, it means that the forward osmosis membrane is intolerant to the pH value membrane. The temperature tolerance of the forward osmosis membrane is measured by the following experimental method: the forward osmosis membrane is immersed in an aqueous solution at different temperatures for 72 hours, and then taken out. The water migration rate of the forward osmosis membrane before and after immersion is measured. If the change in the water migration rate of the forward osmosis membrane before and after immersion exceeds 2%, it means that the forward osmosis membrane is intolerant to the temperature. The water migration rate of the forward osmosis membrane is measured by the following experimental method: the water migration rate of the forward osmosis membrane is measured by measuring the weight change of the electrolyte solution at 25°C, and a certain amount of 2mol / L KOH solution and 0.5mol / L NaCl solution are placed on both sides of the forward osmosis membrane. The change in the mass of KOH is recorded at intervals, and the water migration rate of the forward osmosis membrane can be obtained. The contact angle with water was measured by a contact angle meter. The permeability of impurity ions within 72 hours was measured by the following experimental method: The permeability of impurity ions of the forward osmosis membrane was tested on a laboratory seawater electrolysis hydrogen production device. The forward osmosis membrane was fixed between the anode and cathode plates, with the electrolyte solution on one side and seawater on the other side. The permeability was 400 mA / cm 2 The test was run continuously for 72 h at a current density of , and the content of impurity ions in the electrolyte solution was determined.

[0052] In one embodiment of the present disclosure, the method comprises: electrolyzing the preheated seawater in an electrolytic hydrogen production device provided with a modified forward osmosis membrane; the temperature of the preheated seawater is 40-60° C. In the above embodiment, by preheating the seawater to 40-60° C., the seawater transfers heat to the electrolyte after water migration, which promotes the electrolysis reaction of water, avoids the problem of concentration polarization, and improves the efficiency of electrolytic hydrogen production using the seawater electrolytic hydrogen production device.

[0053] In the present disclosure, seawater preheating adopts conventional preheating devices and methods in the art, such as plate heat exchangers, heating rods, etc., which will not be described in detail here.

[0054] In the present disclosure, the volume of the seawater electrolysis hydrogen production device can be 0.2-100m 3 The concentrated seawater in the first seawater tank 1 and the second seawater tank 11 can be intermittently discharged and supplemented with new seawater to ensure that the first forward osmosis membrane and the second forward osmosis membrane can continue to pass water, thereby ensuring that the electrolysis reaction continues.

[0055] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0056] Unless otherwise specified, the materials used in this example are all commercially available products.

[0057] Example 1

[0058] like Figure 1 As shown, the electrolytic hydrogen production device includes an anode reaction unit, a cathode reaction unit and a partition 6; in the anode reaction unit, an anode catalyst layer 5, an anode plate 4, a first electrolyte tank 3, a first forward osmosis membrane 2 and a first seawater tank 1 are sequentially arranged in a direction away from the first surface of the partition 6; an oxygen outlet 14 is arranged on the side wall of the first electrolyte tank 5; in the cathode reaction unit, a cathode catalyst layer 7, a cathode plate 8, a second electrolyte tank 9, a second forward osmosis membrane 10 and a second seawater tank 11 are sequentially arranged in a direction away from the second surface of the partition 6; a hydrogen outlet 13 is arranged on the side wall of the second electrolyte tank 9.

[0059] The first forward osmosis membrane and the second forward osmosis membrane are modified cellulose acetate membranes; the modified cellulose acetate membrane includes a cellulose acetate base membrane and a composite layer covering the surface of the cellulose acetate base membrane, the composite layer contains carboxyl-substituted silicone groups (active polyether silicone); the surface of the cellulose acetate base membrane contains active groups hydroxyl and acetate groups, and the cellulose acetate base membrane and the composite layer are connected by a chemical grafting reaction between the carboxyl-substituted silicone groups and the active groups. The modified cellulose acetate membrane has a thickness of 0.05 mm, a tolerable pH value of 1-14, a tolerable temperature of 70°C, a water migration rate of 0.3 g H2O / gKOH / min, a water contact angle of 20°, and a permeability of impurity ions of 0.005‰ within 72 hours.

[0060] Specific methods for producing hydrogen by electrolysis include:

[0061] (1) Use a heating rod to preheat the seawater to 50°C.

[0062] (2) The preheated seawater is introduced into the first seawater tank 1 and the second seawater tank 11, and the salt concentration in the seawater is measured to be 3.5 wt %; a potassium hydroxide solution with a mass concentration of 60 wt % is introduced into the first electrolyte tank 3 and the second electrolyte tank 9.

[0063] (3) Connect the anode plate 4 to the positive pole of the power supply, and the cathode plate 8 to the negative pole of the power supply; turn on the power supply, the voltage is 2.5V, and the current density is 400mA / cm 2Under the action of the osmotic pressure difference on both sides of the first forward osmosis membrane, the water in the seawater migrates from the first seawater tank 1 to the first electrolyte tank 3, and the first electrolysis is carried out under the catalytic action of the anode catalyst layer 5; under the action of the osmotic pressure difference on both sides of the second forward osmosis membrane, the water in the seawater migrates from the second seawater tank 11 to the second electrolyte tank 9, and the second electrolysis is carried out under the catalytic action of the cathode catalyst layer 7. The first electrolysis and the second electrolysis were carried out for 168 hours.

[0064] The produced hydrogen is collected at the hydrogen outlet 13, and the amount of hydrogen collected per unit time is listed in Table 1.

[0065] Example 2

[0066] The same electrolytic hydrogen production method as in Example 1 was used, except that the electrolysis voltage was 1.2 V, the electrolysis time was 100 h, and the current density was 250 mA / cm 2 .

[0067] The amount of hydrogen collected per unit time is listed in Table 1.

[0068] Example 3

[0069] The same method of producing hydrogen by electrolysis as in Example 1 is adopted, except that the seawater is not preheated.

[0070] The amount of hydrogen collected per unit time is listed in Table 1.

[0071] Comparative Example 1

[0072] The same method of producing hydrogen by electrolysis as in Example 1 was used, except that both the first forward osmosis membrane and the second forward osmosis membrane were unmodified cellulose acetate membranes. The unmodified cellulose acetate membrane had a thickness of 0.2 mm, a tolerance pH of 2-13, a water migration rate of 0.02 g H2O / g KOH / min, and a water contact angle of 75°.

[0073] The amount of hydrogen collected per unit time is listed in Table 1.

[0074] Table 1

[0075] Hydrogen collection volume (mL / h) Example 1 500 Example 2 320 Example 3 330 Comparative Example 1 52

[0076] It can be seen from the data in Table 1 that compared with Comparative Example 1, the hourly hydrogen collection amount of Examples 1-3 is much higher than that of Comparative Example 1, which proves that the use of modified forward osmosis membranes and the method disclosed in the present invention to electrolyze seawater to produce hydrogen has a higher hydrogen production efficiency.

[0077] In Examples 1-3:

[0078] Compared with Example 2, Example 1 has an electrolysis condition that is not within the scope of the present disclosure, and the amount of hydrogen collected per hour in Example 1 is less than that in Example 2, indicating that controlling the electrolysis condition within the scope of the present disclosure is beneficial to improving the hydrogen production efficiency.

[0079] Compared with Example 3, Example 1 does not preheat the seawater in Example 2, and the amount of hydrogen collected per hour in Example 1 is less than that in Example 3, indicating that controlling the temperature of seawater preheating within the scope of the present disclosure is beneficial to improving hydrogen production efficiency.

[0080] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0081] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0082] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for producing hydrogen by electrolysis using a seawater electrolysis hydrogen production device, characterized in that: The method comprises: electrolyzing seawater in an electrolytic hydrogen production device provided with a modified forward osmosis membrane; Wherein, the modified forward osmosis membrane comprises a base membrane and a composite layer covering the surface of the base membrane; The composite layer contains hydrophilic organosilicon groups substituted with aromatic hydrocarbon groups; the surface of the base film contains active groups, which include one or more of carboxyl groups, amine groups, hydroxyl groups, acetate groups, amide groups, amino groups, aldehyde groups and carbonyl groups; The base film and the composite layer are connected through a chemical grafting reaction between the hydrophilic organic silicon group substituted by the aromatic hydrocarbon group and the active group.

2. The method according to claim 1, characterized in that The electrolytic hydrogen production device comprises an anode reaction unit, a cathode reaction unit and a separator (6); In the anode reaction unit, an anode catalyst layer (5), an anode plate (4), a first electrolyte tank (3), a first forward osmosis membrane (2) and a first seawater tank (1) are sequentially arranged in a direction away from the first surface of the separator (6); an oxygen outlet (14) is arranged on the side wall of the first electrolyte tank (5); In the cathode reaction unit, a cathode catalyst layer (7), a cathode plate (8), a second electrolyte tank (9), a second forward osmosis membrane (10) and a second seawater tank (11) are sequentially arranged in a direction away from the second surface of the separator (6); a hydrogen outlet (13) is arranged on the side wall of the second electrolyte tank (9); Wherein, the first forward osmosis membrane and the second forward osmosis membrane are each independently the modified forward osmosis membrane.

3. The method according to claim 2, characterized in that The method comprises: S1, connecting the anode plate (4) to the positive electrode of a power source, and connecting the cathode plate (8) to the negative electrode of a power source; S2. Under the action of the osmotic pressure difference between the two sides of the first forward osmosis membrane, water in the seawater migrates from the first seawater tank (1) to the first electrolyte tank (3), and a first electrolysis is performed under the catalytic action of the anode catalyst layer (5); Under the action of the osmotic pressure difference on both sides of the second forward osmosis membrane, water in the seawater migrates from the second seawater tank (11) to the second electrolyte tank (9), and the second electrolysis is carried out under the catalytic action of the cathode catalyst layer (7).

4. The method according to claim 1, characterized in that The electrolysis conditions include: voltage of 1.2-2.5V, electrolysis time of 100-500h, current density of 300-400mA / cm 2 .

5. The method according to claim 1, characterized in that The aromatic hydrocarbon group is selected from aromatic hydrocarbon groups having 6 to 12 carbon atoms; the hydrophilic silicone group is selected from one or more of an active polyether silicone group, a polydimethylsiloxane group, a polymethyl hydrogen-(dimethyl)siloxane group, a terminal hydroxyl polydimethylsiloxane group and an aminoethyliminopropyl polysiloxane group; Preferably, the aromatic hydrocarbon group is selected from one or more of o-xylyl, m-xylyl, p-xylyl, 1,3,5-triaminophenyl, 1,2,4-triaminophenyl and 2,4-diaminotolyl; The base film is selected from cellulose acetate film and / or polyamide film; the thickness of the base film is 0.01-0.1 mm.

6. The method according to claim 2, characterized in that The thickness of the first forward osmosis membrane (2) and the second forward osmosis membrane (10) are independently 0.01-0.15 mm; The tolerable pH values ​​of the first forward osmosis membrane (2) and the second forward osmosis membrane (10) are independently 1-14; The first forward osmosis membrane (2) and the second forward osmosis membrane (10) have a tolerance temperature of 20-70° C., respectively, independently; The water migration rates of the first forward osmosis membrane (2) and the second forward osmosis membrane (10) are each independently 0.01-0.5 gH2O / g KOH / min; The contact angles of the first forward osmosis membrane (2) and the second forward osmosis membrane (10) with water are independently 5-60°; The impurity ion permeability of the first forward osmosis membrane (2) and the second forward osmosis membrane (10) within 72 hours is independently 0.005-0.08‰.

7. The method according to claim 2, characterized in that The anode catalyst layer (5) contains an anode catalyst, and the anode catalyst is selected from one or more of iron, cobalt, nickel, palladium, platinum, rhodium and ruthenium; The cathode catalyst layer (7) contains a cathode catalyst, and the cathode catalyst is selected from one or more of tin, platinum, molybdenum, titanium disulfide, molybdenum disulfide and tin oxide.

8. The method according to claim 2, characterized in that: The anode catalyst layer (5) and the cathode catalyst layer (7) are each independently a porous mesh structure; The thickness of the anode catalyst layer (5) and the cathode catalyst layer (7) are independently 0.2-5 mm.

9. The method according to claim 2, characterized in that: The first electrolyte tank (3) and the second electrolyte tank (9) are each independently provided with a through hole for allowing the electrolyte to contact the first forward osmosis membrane and the second forward osmosis membrane respectively; The electrolyte contains one or more of potassium hydroxide, sodium hydroxide and cesium hydroxide, and the concentration of the electrolyte is higher than that of the seawater.

10. The method according to claim 1, characterized in that The method comprises: electrolyzing the preheated seawater in an electrolytic hydrogen production device provided with the modified forward osmosis membrane; the temperature of the preheated seawater is 40-60°C.

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