Method for regulating salinity difference conversion power of conductive polymer film by electric field

Abstract

The invention discloses a method for regulating and controlling salinity difference conversion power of a conductive polymer film through an electric field, and belongs to the technical field of salinity difference power generation. According to the method, the polyaniline film is converted between an oxidation state and a reduction state by utilizing an oxidation reaction and a reduction reaction of the conductive polymer, the surface protonation degree of the polyaniline film is regulated and controlled, the surface charged state of the polyaniline film is influenced, the surface ion selectivity of the polyaniline film is changed, and finally the salinity gradient power generation conversion power is changed. When the prepared polyaniline film is used for salinity gradient power generation, the commercial minimum energy density requirement of 5 W / m < 2 > is met, and the salinity gradient power generation power of the conductive polymer film is autonomously regulated and controlled, so that the capability of converting salinity gradient energy and electric energy of the polymer film is regulated.

Description

Technical Field

[0001] The invention relates to the technical field of salt difference power generation, and in particular to a method for regulating salt difference power conversion of a conductive polymer membrane by electric field. Background Art

[0002] With the rapid growth of social economy, environmental problems are becoming increasingly prominent, forcing people to turn their attention to green and low-carbon energy to replace traditional fossil energy and achieve sustainable development goals. Salinity difference energy mainly exists at the mouth of rivers and seas. It is the energy generated by the mixture of seawater and fresh water or two solutions with different salinities. In the process of salt difference power generation, there is no need to add fuel, no carbon dioxide emissions, and no garbage. Salinity difference energy has the characteristics of high energy density, renewable and pollution-free, and is known as the renewable energy with the highest energy density in the ocean.

[0003] The power system is mainly composed of the power generation side and the power consumption side. The power generation side includes hydropower, thermal power, nuclear power, solar energy, wind power, salinity difference and other power generation methods, and the power consumption side mainly includes factories, enterprises, shopping malls, households, etc. The power generation side and the power consumption side are not necessarily balanced. The loads of factories and enterprises generally use more electricity during the day and less electricity at night; the household load generally uses less electricity during the day and more electricity at night; but generally speaking, there is a peak in electricity consumption during the day and a trough in electricity consumption at night. Hydropower, thermal power and nuclear power are generally large-scale generators. Once the equipment is started, it cannot be stopped at will. New energy sources such as solar energy and wind power generate electricity according to the environment and climate. The power generation is unstable and changes at any time. Therefore, the still developing salinity difference power generation has the opportunity to play a role in it by studying new control technologies. Ion selective membranes are key materials for salinity difference energy conversion. At present, most of the research on ion selective membranes focuses on improving the performance or power generation capacity of ion selective membrane materials. However, so far, the construction of ion selective membranes still cannot achieve power control in the process of salinity difference power generation, and research on autonomous control of salinity difference conversion performance needs to be continued. Summary of the invention

[0004] In view of the above-mentioned prior art, the object of the present invention is to provide a method for regulating the power conversion of salt difference of a conductive polymer membrane by electric field.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention provides a method for electric field regulation of salt difference conversion power of a conductive polymer membrane, comprising the following steps: performing external field regulation on a conductive polymer membrane used for salt difference power generation, changing the ion selectivity of the conductive polymer membrane, and regulating the salt difference power generation conversion power.

[0006] The inventors found that the charged state of the membrane surface can be regulated by the oxidation reaction or reduction reaction of the conductive polymer membrane, and the controllable conversion of salt difference energy and electrical energy can be achieved, thereby completing the present invention. Specifically, the present invention first adopts an electrochemical deposition method to prepare a polyaniline membrane on a porous gold mesh substrate. Then, in an acidic electrolyte, an oxidation potential or a reduction potential is applied to the membrane, and the oxidation reaction or reduction reaction of the polyaniline membrane is used to produce a conductive polymer membrane with different dissociation states (different dissociation constant PKa values), thereby affecting the protonation degree of the polymer membrane in the KCl electrolyte, changing the surface charge state of the conductive polymer membrane, and then affecting the ion selectivity, and regulating the salt difference conversion performance.

[0007] Furthermore, the conductive polymer film is at least one of a polyaniline film, a polypyrrole film, a polythiophene film, a polyacetylene film, a poly(p-phenylene vinylene) film or a polyethylene dioxythiophene film.

[0008] Furthermore, the conductive polymer film is a conductive polymer film having external field response characteristics, and the external field is at least one of an electric field, a magnetic field, a thermal field or a light field.

[0009] Furthermore, by applying an electric field to regulate the oxidation reaction or reduction reaction on the surface of the conductive polymer membrane, the charge state of the surface of the conductive polymer membrane is changed, thereby changing its ion selectivity.

[0010] Furthermore, the conductive polymer film is a polyaniline film; the oxidized state of the polyaniline film is shown in Formula I, and the reduced state of the polyaniline film is shown in Formula II, wherein: Formula I, Formula II.

[0011] Furthermore, in the process of electric field regulation, the electrode used is at least one of a platinum electrode, a carbon electrode, a gold electrode, a silver electrode or a nickel electrode; the reference electrode used is at least one of an Ag / AgCl electrode, a standard hydrogen electrode, a saturated calomel electrode, a copper / copper sulfate electrode or a high-purity zinc reference electrode. In some embodiments, the counter electrode is a platinum electrode; and the reference electrode is an Ag / AgCl electrode.

[0012] Furthermore, during the electric field regulation process, the electrolyte used is HCl, H2SO4, HNO3, H3PO3 or HClO with a concentration of 0.01 M to 1 M. In some embodiments, the electrolyte is a 0.5 M H2SO4 aqueous solution.

[0013] Furthermore, during the electric field regulation process, the potential applied to the conductive polymer film is -10 V to 10 V vs. Ag / AgCl. In some embodiments, the oxidation potential is +0.7 V (vs. Ag / AgCl) and the reduction potential is -0.4 V (vs. Ag / AgCl).

[0014] Beneficial effects of the present invention: The present invention utilizes the oxidation reaction and reduction reaction of the conductive polymer to transform the polyaniline membrane between the oxidized state and the reduced state, change the constituent units of the polyaniline membrane, affect the protonation degree of the polyaniline membrane surface, change the ion selectivity of the polyaniline membrane surface, and finally regulate the conversion efficiency of the salt difference power generation. The polyaniline conductive polymer membrane prepared by the present invention reaches 5 W / m when used for salt difference power generation. 2 In order to meet the commercial minimum energy density requirements, the salt difference power generation power of the conductive polymer membrane was autonomously controlled, and the ability of the polymer membrane to convert salt difference energy and electrical energy was regulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The polyaniline film used in the present invention, wherein Figure 1 a in the figure is a reduced polyaniline film. Figure 1 b is an oxidized polyaniline film. Figure 1 Figure c is the protonated polyaniline membrane.

[0016] Figure 2 This is an electron microscope photo of the gold mesh substrate used in the present invention.

[0017] Figure 3 This is an electron microscope photograph of the polyaniline film used in the present invention.

[0018] Figure 4 This is a diagram of the polyaniline film current testing device in the present invention.

[0019] Figure 5 1 is the ionic current-voltage curve of the polyaniline membrane under different redox states in the present invention. DETAILED DESCRIPTION

[0020] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0021] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0022] [Outfield Control] External field regulation refers to the method of changing the properties of a substrate under external conditions such as light, electric field or magnetic field.

[0023] It is impossible to control the power generation by utilizing the material's own characteristics. For example, when a material itself does not change its material state, it can only have one power generation capacity, so it can only be controlled by an external field.

[0024] [Conductive polymer film] The conductive polymer film of the present invention refers to a type of polymer material in which a polymer having conjugated π bonds is chemically or electrochemically "doped" to change it from an insulator to a conductor. The structural feature of the conductive polymer molecule is that it contains a polymer chain structure and a monovalent anion or cation that is non-bonded to the chain. In the conductive polymer molecular structure, in addition to the polymer chain, it also contains a monovalent anion (p-type doping) or a cation (n-type doping) introduced by "doping". As conductive polymer materials, for example, polyaniline, polypyrrole, polythiophene, polyacetylene, polyvinylene, polyethylene dioxythiophene, etc. can be listed, preferably polyaniline.

[0025] [Regulating the salt difference conversion power of conductive polymer membranes] The salt difference conversion power of the conductive polymer membrane of the present invention refers to applying an electric field to the membrane to cause an oxidation reaction or a reduction reaction of the conductive polymer membrane, changing the constituent units of the polymer membrane, and realizing the selective transport of ions. The protonation degree of the conductive polymer membrane is different under different redox states, causing proton doping on the membrane surface, affecting the surface charge of the polymer membrane, changing the ion selectivity of the polymer membrane, and realizing the salt difference power generation power conversion regulated by the redox state. Based on the redox characteristics of the polyaniline membrane, the present invention prepares a polyaniline conductive polymer membrane for the study of salt difference power generation performance.

[0026] When the conductive polymer film is a polyaniline film, the redox reaction is an oxidation reaction or a reduction reaction between an oxidized molecule represented by the following formula I and a reduced molecule represented by the following formula II.

[0027] Formula I Formula II The molecule shown in Formula I is in an oxidized state. The oxidized polyaniline is mainly composed of a quinone ring structure. The N element in the formula has a high degree of protonation in a neutral electrolyte, and the polyaniline membrane can be positively charged through the protonation process.

[0028] The molecule shown in Formula II is in a reduced state. The reduced polyaniline is mainly composed of a benzene ring structure. The N element in the formula has a low degree of protonation in a neutral electrolyte, and the surface of the polyaniline membrane is almost uncharged.

[0029] The modification of polyaniline mainly includes two processes, one is oxidation-reduction and the other is protonation.

[0030] The redox process is carried out by applying a redox potential to the membrane in 0.5 M sulfuric acid, and the PKa value of polyaniline can be changed through the redox process. The degree of protonation is mainly measured by the relationship between the PKa value of polyaniline and the pH value of the solution. Compared with the pH value of the solution, the larger the PKa, the higher the degree of protonation.

[0031] When performing salt difference power generation, the electrolyte used is KCl, so the pH of the electrolyte is 7. When a potential of 0.7 V is applied in a 0.5 M sulfuric acid electrolyte, an oxidized polyaniline membrane is obtained, and the PKa value of the oxidized polyaniline is greater than 8. At this time, the polyaniline can be considered to be completely protonated in the KCl electrolyte with a pH of 7, and the polyaniline membrane surface carries the most charge, has high ion selectivity, and has high power generation efficiency; when a -0.4 V potential is applied to polyaniline in a 0.5 M sulfuric acid electrolyte, polyaniline can be completely reduced, and the reduced polyaniline is composed of benzene ring units, and its Pka value is 1. At this time, the polyaniline has a small degree of protonation in the KCl electrolyte with a pH of 7, resulting in no charge on the polyaniline membrane surface, low ion selectivity, and low power generation efficiency.

[0032] In addition, the use of polyaniline membranes for salt difference power generation has significant advantages, mainly reflected in the following aspects: 1. High ion selectivity: The polyaniline membrane has good ion selectivity, which means that it can more effectively separate different types of ions, thereby improving the conversion efficiency of salt difference energy. This high selectivity helps to reduce energy loss and improve power generation efficiency. 2. Excellent chemical stability: The polyaniline material itself has good chemical stability and can maintain stable performance under a variety of complex environmental conditions. This is crucial for salt difference energy power generation systems, as the system needs to operate for a long time under different solution pH, temperature and other conditions. 3. Good conductivity: Polyaniline is a conductive polymer whose conductive properties can be regulated by doping and other methods. This allows the polyaniline membrane to more effectively transport electrons during salt difference power generation, thereby increasing the output of electrical energy. 4. Easy preparation and processing: The preparation and processing of polyaniline membranes are relatively simple and low cost. This helps to reduce the manufacturing cost of salt difference energy power generation systems and improve their economic feasibility. 5. Environmentally friendly: As an organic material, polyaniline is environmentally friendly and does not produce harmful byproducts. This is in line with the current trend of green energy development. 6. Long-term stability: The polyaniline membrane exhibits good long-term stability in continuous operation mode. This is of great significance for the long-term operation and maintenance of the salt gradient energy power generation system.

[0033] The experimental materials used in the examples of the present invention but not specifically described are all conventional experimental materials in the art and can be purchased through commercial channels.

[0034] Example 1: Preparation of polyaniline film The polyaniline film was prepared on a porous gold mesh conductive substrate by constant potential polymerization. A three-electrode working system was used, with a 2000 mesh gold mesh as the working electrode (area 7.0 mm 2 ), platinum sheet is used as counter electrode. Ag / AgCl electrode is used as reference electrode. The electrolyte contains 0.1 M aniline, 0.1 M sulfuric acid and 0.1% sodium polystyrene sulfonate solution. Using an electrochemical workstation, a +0.7 V potential is applied to the gold mesh working electrode to perform electrochemical polymerization in the electrolyte, and a green polyaniline film can be generated on the surface of the gold mesh.

[0035] The morphology of the obtained polyaniline film was observed. The electron microscope image of the porous gold mesh substrate used in the preparation process is shown in Figure 2 The obtained polyaniline film electron microscopy image is shown in Figure 3 shown.

[0036] The salt difference power generation performance of the polyaniline membrane was determined by the current-voltage curve. The device used was as follows Figure 4 shown.

[0037] At room temperature, the polyaniline membrane was installed in the middle of a double-chamber electrochemical cell, and 0.5 mM and 0.01 mM KCl electrolytes were injected into the chambers on both sides of the electrochemical cell to form a concentration cell. A transmembrane voltage was applied to the membrane, and the current was monitored by a pair of Ag / AgCl electrodes connected to a picoammeter. The measured current-voltage curve is shown as the solid line in Figure 5.

[0038] According to the salt difference power generation power density calculation formula P=I sc V oc / 4S, where I sc It refers to the short-circuit current of the IV curve (i.e. the intersection of this line and the V=0 line), V oc It refers to the open circuit voltage (the intersection value of this line with I=0), and S is the effective power generation area of ​​the membrane. The effective area of ​​the polyaniline membrane salt difference power generation in this patent is 3*10 -8 m 2 The output power density of the polyaniline film can be calculated as P = 0.093*8.44x10 -6 / 4*3*10 -8 ≈6.5 W / m 2 .

[0039] Example 2 In order to control the ion selectivity of the polyaniline membrane, the inventors placed the polyaniline membrane in an acidic environment, changed the surface oxidation state or reduction state of the polyaniline, affected its protonation degree, and changed the surface charge of the polyaniline membrane. The specific operation is as follows: in a 0.5 M H2SO4 solution, a -0.4 V potential was applied to the polyaniline membrane. After electrochemical reduction for 10 min, the polyaniline chain was mainly composed of benzene ring structures, and a reduced polyaniline membrane ( Figure 1 (a) The pKa value of reduced polyaniline is 1. In a neutral KCl electrolyte, the protonation degree is low, resulting in no charge on the surface of the reduced polyaniline membrane and reduced ion selectivity.

[0040] The reduced polyaniline membrane was mounted on the same double-chamber electrolytic cell as used in Example 1, and the current-voltage curves in 0.5 mM and 0.01 mM KCl electrolytes were measured. The results are shown in the dot-dash lines in FIG5 .

[0041] According to the salt difference power generation power density calculation formula P=I sc V oc / 4S, the output power density of the polyaniline film can be calculated as P=0.08*8.72*10 -7 / 4*3*10 -8 ≈0.6 W / m 2 .

[0042] Example 3 In order to further control the ion selectivity of the polyaniline membrane, the inventors further treated the polyaniline membrane. Specifically, in a 0.5 M H2SO4 solution, a +0.7 V potential was applied to the polyaniline membrane. After electrochemical oxidation for 10 min, the benzene ring structure of the polyaniline chain was converted into a quinone ring structure, and an oxidized polyaniline membrane ( Figure 1 (b)

[0043] The pKa value of the oxidized polyaniline membrane is greater than 8. In a neutral KCl electrolyte, the nitrogen atoms on the polyaniline can be completely protonated ( Figure 1 In (c), this protonation causes holes to appear in the valence band of the doped segment on the polyaniline chain, i.e., P-type doping, forming a stable delocalized polyemeraldine atom group. The positive charge carried by the imine nitrogen atom can be transferred to the neighboring atoms along the polyaniline molecular chain through conjugation, thereby increasing the stability of the system and making the polyaniline membrane have higher ion selectivity.

[0044] The oxidized polyaniline membrane was mounted on the same dual-chamber electrolytic cell as used in Example 1, and the current-voltage curves in 0.5 mM and 0.01 mM KCl electrolytes were measured. The results are shown in the dotted lines in FIG5 .

[0045] According to the salt difference power generation power density calculation formula P=I sc V oc / 4S, the output power density of the polyaniline film can be calculated as P=0.088*8.43*10 -6 / 4*3*10 -8 ≈6.2 W / m 2 .

[0046] It can be seen that, compared with the reduced polyaniline membrane prepared in Example 2, the oxidized polyaniline membrane prepared in Example 3 has higher ion selectivity and enhanced salt difference conversion power.

[0047] In summary, the salt difference power generation performance of the polyaniline membrane can be adjusted by changing the polyaniline membrane between the oxidized state and the reduced state and regulating its ion selectivity. When it is used for salt difference power generation, it reaches 5 W / m 2 The minimum energy density requirement for commercialization.

[0048] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for converting power by controlling salt difference of a conductive polymer membrane by electric field, characterized in that: The method comprises the following steps: performing external field regulation on a conductive polymer membrane used for salt difference power generation, changing the ion selectivity of the conductive polymer membrane, and regulating the conversion power of salt difference power generation.

2. The method for converting power by electric field regulation of conductive polymer membrane salt difference according to claim 1, characterized in that: The conductive polymer film is at least one of a polyaniline film, a polypyrrole film, a polythiophene film, a polyacetylene film, a poly(p-phenylene vinylene) film or a polyethylene dioxythiophene film.

3. The method for converting power by electric field regulation of conductive polymer membrane salt difference according to claim 2, characterized in that: The conductive polymer film is a conductive polymer film having external field response characteristics, and the external field is at least one of an electric field, a magnetic field, a thermal field or a light field.

4. The method for converting power by electric field regulation of conductive polymer membrane salt difference according to claim 3, characterized in that: By applying an electric field, the oxidation state or reduction state of the conductive polymer membrane is regulated, the constituent units of the conductive polymer membrane are changed, the charge state of the membrane surface is affected, and its ion selectivity is changed.

5. The method for converting power by electric field regulation of conductive polymer membrane salt difference according to claim 4, characterized in that: The conductive polymer film is a polyaniline film; the oxidized state of the polyaniline film is shown in Formula I, and the reduced state of the polyaniline film is shown in Formula II, wherein: Formula I, Formula II.

6. The method for converting power by electric field regulation of conductive polymer membrane salt difference according to claim 4, characterized in that the electric field During the regulation process, the electrode used is at least one of a platinum electrode, a carbon electrode, a gold electrode, a silver electrode or a nickel electrode; the reference electrode used is at least one of an Ag / AgCl electrode, a standard hydrogen electrode, a saturated calomel electrode, a copper / copper sulfate electrode or a high-purity zinc reference electrode.

7. The method for converting power by electric field regulation of salt difference of a conductive polymer membrane according to claim 4, characterized in that the electric field During the regulation process, the electrolyte used is HCl, H2SO4, HNO3, H3PO3 or HClO with a concentration of 0.01 M~1 M.

8. The method for converting power by electric field regulation of salt difference of a conductive polymer membrane according to claim 4, characterized in that: During the electric field control process, the potential applied to the conductive polymer film was -10 V~10 V vs. Ag / AgCl.

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