Method for producing hydrogen by seawater electrolysis based on forward osmosis of ionic liquid

Abstract

The invention discloses a seawater electrolysis hydrogen production method based on ionic liquid forward osmosis, and belongs to the technical field of seawater electrolysis hydrogen production. The seawater electrolysis hydrogen production system comprises a forward osmosis device and an electrolytic bath device, the forward osmosis device comprises a forward osmosis membrane and an ionic liquid cavity; the ionic liquid cavity is used for filling ionic liquid capable of absorbing moisture in seawater; the forward osmosis membrane is used for blocking seawater and liquid phase components in the ionic liquid cavity; and the ionic liquid cavity is communicated with the electrolytic bath device through a pumping device. According to the invention, seawater forward osmosis and electrolytic hydrogen production are combined, so that the problems of high impurity ion concentration and more side reactions in the process of directly producing hydrogen from seawater are solved. The ionic liquid not only can be used as a forward osmosis draw solution, but also can be used as an electrolyte material, can be used for simultaneously realizing seawater forward osmosis and electrolytic hydrogen production, and provides a new research and development direction for realizing seawater electrolytic hydrogen production.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by seawater electrolysis, and in particular to a method for hydrogen production by seawater electrolysis based on ionic liquid forward osmosis. Background Art

[0002] Seawater electrolysis is a technology that uses water molecules in seawater to decompose into hydrogen and oxygen through an electrolysis process. The advantages of this technology are sustainability and low cost. Unlike traditional freshwater hydrogen production, due to the complexity of seawater itself, a complex electrolyte solution containing a large amount of impurities and ions will be generated during the seawater electrolysis process. These impurities and ions will corrode or clog the electrodes during the electrolysis process, affecting the electrolysis efficiency. There are huge challenges in directly electrolyzing seawater to produce hydrogen.

[0003] Combining seawater forward osmosis with electrolytic hydrogen production is a new research and development idea, but the electrolyte of this hydrogen production process usually requires a strongly alkaline sodium hydroxide solution or potassium hydroxide solution (pH>14), and most of the currently commercialized forward osmosis membrane materials are cellulose triacetate film (CTA, pH range of 3-8), polyamide thin layer composite membrane (TFC, pH range of 2-11), etc., which are very unstable in strongly alkaline (pH>14) electrolytes. This still poses great challenges to the combination of seawater forward osmosis and electrolytic hydrogen production, and further improvements are still needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for producing hydrogen by electrolysis of seawater based on forward osmosis of ionic liquids, so as to solve the above-mentioned problems in the background technology. Compared with the existing seawater hydrogen production technology, the present invention combines seawater forward osmosis with electrolysis to produce hydrogen, solving the problems of high concentration of impurity ions and many side reactions in the process of direct hydrogen production from seawater. Ionic liquids can be used as the draw liquid of the forward osmosis in the present invention, and can also exist as electrolyte materials, which can be used to realize forward osmosis of seawater and electrolysis to produce hydrogen at the same time, providing a new research and development direction for realizing hydrogen production by electrolysis of seawater.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a method for producing hydrogen by electrolysis of seawater based on ionic liquid forward osmosis, wherein water in seawater is extracted through ionic liquid and forward osmosis membrane, and diluted ionic liquid obtained through forward osmosis of seawater is used as electrolyte solution to produce hydrogen by electrolysis.

[0007] Preferably, the concentration of the ionic liquid in the ionic liquid dilution solution is 20-40 wt %.

[0008] Preferably, the cations in the ionic liquid include imidazolium cations, pyrrole cations or piperidine cations; the anions in the ionic liquid include but are not limited to [BF 4 ] - (tetrafluoroborate anion), [DEP] - (diethyl phosphite anion), [DMP] - (dimethyl phosphate anion), [EtSO 4 ] - (ethyl sulfate anion) or [AC] - (acetate anion).

[0009] Preferably, the cation in the ionic liquid is an imidazolium cation, and the anion in the ionic liquid is [BF4] - and / or [AC] - .

[0010] Preferably, the ionic liquid is [BMIm]BF 4 、[HMIm]BF 4 or [EMIM][AC].

[0011] After research, the inventors found that imidazole ionic liquids have the best solubility in the reaction system, which is conducive to the forward osmosis experiment; the anion is [BF 4 ] - or [AC] - When the ionic liquid is used, the stability of the ionic liquid is better and the electrochemical window is higher, which is conducive to hydrogen production by electrolysis. On this basis, the further preferred ionic liquid type is [BMIm]BF 4 、[HMIm]BF 4 、[EMIM][AC].

[0012] Preferably, the forward osmosis membrane comprises a triacetyl cellulose membrane or a polyamide thin layer composite membrane.

[0013] The second technical solution of the present invention is to provide a seawater electrolysis hydrogen production system for the above-mentioned method of producing hydrogen by seawater electrolysis based on ionic liquid forward osmosis, comprising a forward osmosis device and an electrolyzer device;

[0014] The forward osmosis device comprises a forward osmosis membrane and an ionic liquid chamber;

[0015] The ionic liquid chamber is used to fill the ionic liquid capable of absorbing water from seawater; the forward osmosis membrane is used to block the liquid phase components in the seawater and the ionic liquid chamber;

[0016] The ionic liquid chamber and the electrolytic cell device are communicated with each other through a pumping device.

[0017] Preferably, the forward osmosis device further comprises a seawater chamber for containing seawater; the forward osmosis membrane is used to block the liquid phase components in the seawater chamber and the liquid phase components in the ionic liquid chamber.

[0018] Preferably, the electrodes of the electrolytic cell device are configured as a three-electrode system.

[0019] Preferably, in the three-electrode system, Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and a platinum sheet is used as the working electrode.

[0020] The third technical solution of the present invention is to provide a method for using the above-mentioned seawater electrolysis hydrogen production system, comprising the following steps:

[0021] The ionic liquid chamber is filled with ionic liquid as an extraction liquid, so that the ionic liquid is in contact with one side of the forward osmosis membrane, and seawater is introduced into the other side of the forward osmosis membrane for extraction treatment to obtain an ionic liquid dilution liquid;

[0022] The ionic liquid dilution in the ionic liquid chamber is discharged into the electrolyzer device through a pumping device to perform electrolytic hydrogen production treatment to obtain hydrogen gas.

[0023] Preferably, the applied potential of the electrolytic hydrogen production process is 1.5-2.0V.

[0024] Preferably, the draw liquid is an ionic liquid aqueous solution, wherein the mass fraction of the ionic liquid in the ionic liquid aqueous solution is ≥50%.

[0025] The beneficial technical effects of the present invention are as follows:

[0026] Compared with the existing seawater hydrogen production technology, the present invention combines seawater forward osmosis with electrolytic hydrogen production, solving the problems of high impurity ion concentration and many side reactions in the direct seawater hydrogen production process. Ionic liquid can be used as the forward osmosis draw liquid in the present invention, and can also exist as an electrolyte material. It can be used to achieve seawater forward osmosis and electrolytic hydrogen production at the same time, providing a new research and development direction for achieving seawater electrolytic hydrogen production. The osmotic pressure of the ionic liquid is greater than the osmotic pressure on the seawater side, so the water in the seawater will flow through the forward osmosis membrane to the ionic liquid side; at the same time, the ionic liquid diluent is electrolyzed by electricity, and the water in the ionic liquid is decomposed into hydrogen and oxygen by electric current.

[0027] The present invention innovatively uses ionic liquids, which have the functions of both extraction liquid and electrolyte. Compared with the strong alkaline electrolyte commonly used in traditional electrolysis hydrogen production processes (which is corrosive to traditional forward osmosis membranes), it shows affinity for forward osmosis membrane materials, significantly enhances the stability of forward osmosis membranes during long-term operation, and thus effectively extends the service life of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 Schematic diagram of the ionic liquid-based seawater electrolysis hydrogen production system in Examples 1-3 during the electrolysis hydrogen production process. DETAILED DESCRIPTION

[0030] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0031] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0032] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0034] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0035] Example 1

[0036] A seawater electrolysis hydrogen production system based on ionic liquids, consisting of a forward osmosis device and an electrolyzer device;

[0037] The forward osmosis device consists of a forward osmosis membrane (cellulose triacetate membrane, size 6cm*4.5cm), a seawater chamber and an ionic liquid chamber;

[0038] The forward osmosis membrane is used to block the liquid phase components in the seawater chamber and the liquid phase components in the ionic liquid chamber; the ionic liquid chamber and the electrolytic cell device are connected to each other through a pumping device;

[0039] In the electrolytic cell device, a three-electrode system is formed with Ag / AgCl as a reference electrode, a platinum sheet as a counter electrode, and a platinum sheet as a working electrode, and the electrode area is 1 cm×1 cm.

[0040] Hydrogen production by forward osmosis seawater electrolysis:

[0041] The ionic liquid chamber was filled with 500 g of ionic liquid aqueous solution with a mass concentration of 60 wt% (the type of ionic liquid was [BMIM] BF 4 ), as the extraction liquid; the seawater chamber is filled with 500ml of Bohai seawater with a TDS of 32g / L after ultrafiltration treatment, as the forward osmosis raw material liquid; the extraction treatment is performed to obtain a 30wt% ionic liquid dilution liquid;

[0042] The ionic liquid dilution in the ionic liquid chamber is completely discharged into the electrolyzer device through a pumping device and used as an electrolyte. Under the condition of an applied potential of 1.8V, electrolysis and hydrogen production are carried out, and hydrogen is produced at the cathode and oxygen is produced at the anode of the electrolyzer. It is measured that the current density (the current density is proportional to the hydrogen production rate) during this period is 0.126A / cm 2 When the mass of the electrolyte in the electrolytic cell device reaches the initial mass of the ionic liquid aqueous solution (500 g), the electrolyte is completely discharged into the ionic liquid chamber through the pumping device again, and the cycle is repeated.

[0043] Example 2

[0044] A seawater electrolysis hydrogen production system based on ionic liquids, consisting of a forward osmosis device and an electrolyzer device;

[0045] The forward osmosis device consists of a forward osmosis membrane (cellulose triacetate membrane, size 6cm*4.5cm), a seawater chamber and an ionic liquid chamber;

[0046] The forward osmosis membrane is used to block the liquid phase components in the seawater chamber and the liquid phase components in the ionic liquid chamber; the ionic liquid chamber and the electrolytic cell device are connected to each other through a pumping device;

[0047] In the electrolytic cell device, a three-electrode system is formed with Ag / AgCl as a reference electrode, a platinum sheet as a counter electrode, and a platinum sheet as a working electrode, and the electrode area is 1 cm×1 cm.

[0048] Hydrogen production by forward osmosis seawater electrolysis:

[0049] The ionic liquid chamber was filled with 500 g of 50 wt% ionic liquid aqueous solution (the type of ionic liquid was [HMIm]BF 4), as the extraction liquid; the seawater chamber is filled with 500ml of Bohai seawater with a TDS of 32g / L after ultrafiltration treatment, as the forward osmosis raw material liquid; the extraction treatment is performed to obtain an ionic liquid dilution liquid with a mass concentration of 25wt%;

[0050] The ionic liquid dilution in the ionic liquid chamber is completely discharged into the electrolytic cell device through a pumping device and used as an electrolyte. Under the condition of an applied potential of 1.6V, electrolysis and hydrogen production are carried out, and hydrogen is produced at the cathode and oxygen is produced at the anode of the electrolytic cell respectively. It is measured that the current density during this period is 0.118A / cm 2 When the mass of the electrolyte in the electrolytic cell device reaches the initial mass of the ionic liquid aqueous solution (500 g), the electrolyte is completely discharged into the ionic liquid chamber through the pumping device again, and the cycle is repeated.

[0051] Example 3

[0052] A seawater electrolysis hydrogen production system based on ionic liquids, consisting of a forward osmosis device and an electrolyzer device;

[0053] The forward osmosis device consists of a forward osmosis membrane (cellulose triacetate membrane, size 6cm*4.5cm), a seawater chamber and an ionic liquid chamber;

[0054] The forward osmosis membrane is used to block the liquid phase components in the seawater chamber and the liquid phase components in the ionic liquid chamber; the ionic liquid chamber and the electrolytic cell device are connected to each other through a pumping device;

[0055] In the electrolytic cell device, a three-electrode system is formed with Ag / AgCl as a reference electrode, a platinum sheet as a counter electrode, and a platinum sheet as a working electrode, and the electrode area is 1 cm×1 cm.

[0056] Hydrogen production by forward osmosis seawater electrolysis:

[0057] The ionic liquid chamber is filled with 500 g of an ionic liquid aqueous solution (the type of ionic liquid is [EMIM][AC]) with a mass concentration of 55 wt% as an extraction liquid; the seawater chamber is filled with 500 ml of Bohai seawater with a TDS of 32 g / L after ultrafiltration treatment as a forward osmosis raw material liquid; the extraction treatment is performed to obtain an ionic liquid dilution liquid with a mass concentration of 30 wt%;

[0058] The ionic liquid dilution in the ionic liquid chamber is completely discharged into the electrolytic cell device through a pumping device and used as an electrolyte. Under the condition of an applied potential of 2.0V, electrolysis and hydrogen production are carried out, and hydrogen is produced at the cathode and oxygen is produced at the anode of the electrolytic cell respectively. It is measured that the current density during this period is 0.135A / cm 2When the mass of the electrolyte in the electrolytic cell device reaches the initial mass of the ionic liquid aqueous solution (500 g), the electrolyte is completely discharged into the ionic liquid chamber through the pumping device again, and the cycle is repeated.

[0059] Figure 1 Schematic diagram of the ionic liquid-based seawater electrolysis hydrogen production system in Examples 1-3 during the electrolysis hydrogen production process.

[0060] Comparative Example 1

[0061] The only difference from Example 3 is that the type of ionic liquid is replaced by an ionic liquid of equal mass [P 4444 ]C 8 H 10 O 3 It was measured that after 50 min of electrolysis to produce hydrogen at an applied potential of 2.0 V, the electrolyte in the electrolyzer device became turbid and no hydrogen was generated.

[0062] Comparative Example 2

[0063] The only difference from Example 3 is that the type of ionic liquid is replaced by an ionic liquid of equal mass [N 4444 ][EtSO 4 ]. It was measured that the current density was 0.062A / cm 2 .

[0064] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing hydrogen by electrolysis of seawater based on ionic liquid forward osmosis, characterized in that: Water is extracted from seawater through ionic liquid and forward osmosis membrane, and the ionic liquid diluted with seawater obtained by forward osmosis through the forward osmosis membrane is used as the electrolyte solution for electrolysis to produce hydrogen.

2. The method according to claim 1, characterized in that The concentration of the ionic liquid in the ionic liquid dilution solution is 20-40 wt %.

3. The method according to claim 1, characterized in that The cations in the ionic liquid include imidazolium cations, pyrrole cations or piperidine cations; the anions in the ionic liquid include [BF4] - , [DEP] - , [DMP] - , [EtSO4] - or [AC] - .

4. The method according to claim 1, characterized in that: The ionic liquid is [BMIm]BF4, [HMIm]BF4 or [EMIM][AC].

5. The method according to claim 1, characterized in that: The forward osmosis membrane comprises a triacetyl cellulose membrane or a polyamide thin layer composite membrane.

6. A seawater electrolysis hydrogen production system for the method for producing hydrogen by ionic liquid forward osmosis seawater electrolysis according to any one of claims 1 to 5, characterized in that: Includes a forward osmosis device and an electrolyzer device; The forward osmosis device comprises a forward osmosis membrane and an ionic liquid chamber; The ionic liquid chamber is used to fill the ionic liquid capable of absorbing moisture from seawater; The forward osmosis membrane is used to block the liquid components in the seawater and ionic liquid chamber; The ionic liquid chamber and the electrolytic cell device are communicated with each other through a pumping device.

7. The seawater electrolysis hydrogen production system according to claim 6, characterized in that: The forward osmosis device also comprises a seawater cavity for containing seawater; the forward osmosis membrane is used to block the liquid phase components in the seawater cavity and the liquid phase components in the ionic liquid cavity.

8. The seawater electrolysis hydrogen production system according to claim 6, characterized in that: The electrodes of the electrolytic cell device are configured as a three-electrode system.

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