CN113087950A - Chitosan composite membrane and fuel cell - Google Patents
Chitosan composite membrane and fuel cell Download PDFInfo
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- CN113087950A CN113087950A CN202110195007.3A CN202110195007A CN113087950A CN 113087950 A CN113087950 A CN 113087950A CN 202110195007 A CN202110195007 A CN 202110195007A CN 113087950 A CN113087950 A CN 113087950A
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- 239000000446 fuel Substances 0.000 title claims abstract description 14
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
- C08J5/2212—Natural macromolecular compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2287—After-treatment
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
- H01M8/1025—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon and oxygen, e.g. polyethers, sulfonated polyetheretherketones [S-PEEK], sulfonated polysaccharides, sulfonated celluloses or sulfonated polyesters
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1041—Polymer electrolyte composites, mixtures or blends
- H01M8/1046—Mixtures of at least one polymer and at least one additive
- H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
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- C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
- C08J2305/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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Abstract
The invention discloses a chitosan composite membrane and a fuel cell, and the preparation method comprises the following steps: s10, preparing acidified carbon nanotubes; s20, coating silicon dioxide on the surface of the acidified carbon nano tube to obtain a carbon nano tube coated with the silicon dioxide; s30, performing sulfonation modification on silicon dioxide in the carbon nano tube coated with the silicon dioxide to obtain a carbon nano tube coated with the modified silicon dioxide; and S40, preparing the carbon nano tube coated with the modified silicon dioxide and the chitosan solution into the chitosan composite film. The carbon nano tube and the chitosan are modified in a composite mode, so that the mechanical property and the proton conduction property of the chitosan composite membrane are improved; the surface of the carbon nano tube is coated with silicon dioxide, so that the proton conductivity and the mechanical property are further improved, and in addition, the surface coating avoids the short circuit risk caused by the excellent conductivity of the carbon nano tube; the conductivity and mechanical property are further improved through organic sulfonation treatment, so that the chitosan composite membrane can meet the application requirement of the proton exchange membrane fuel cell.
Description
Technical Field
The invention relates to the technical field of fuel cells, in particular to a fuel cell and a preparation method thereof.
Background
Chitosan (Chitosan, CS) as a natural polymer material has the following characteristics: 1) the source is rich, the price is low, and the environment is friendly; 2) the hydrophilic property is good; 3) the methanol permeability is low, and the film is easy to form; 4) the framework structure is easily chemically modified. These characteristics make it have very good application potentiality in the field of proton exchange membrane. However, the mechanical properties of the pure chitosan film are poor, and due to intramolecular and intermolecular hydrogen bonds which are very easily formed in the structure, a rigid crystalline region with a high proportion exists in the film, so that ions are difficult to migrate in the film, and the conduction performance is unsatisfactory.
Therefore, in order to improve the comprehensive performance of chitosan, researchers have conducted extensive modification studies on chitosan, and among them, organic-inorganic composite modification strategies are favored by researchers, and clay materials, inorganic acid materials, metal oxides and carbon nanomaterials are widely used in the modification studies on chitosan. The one-dimensional Carbon Nano Tube (CNT) has the advantages of great length-diameter ratio, excellent heat conduction and mechanical properties, and can realize the remarkable improvement of the relevant properties of the composite material under the appropriate filling amount without influencing the processing property and the flexibility of the material. However, the carbon nanotubes are insoluble, chemically inert on the surface and extremely large in specific surface area, are easy to agglomerate in an organic polymer matrix, have low bonding strength with the polymer matrix interface and poor dispersibility, and have unsatisfactory compounding effect with the polymer directly, so that the comprehensive performance of the composite membrane serving as the proton exchange membrane is influenced.
Disclosure of Invention
The invention mainly aims to provide a chitosan composite membrane and a fuel cell, and aims to solve the problem that the comprehensive performance of the existing organic-inorganic composite modified material used as a proton exchange membrane is poor.
In order to achieve the above object, the present invention provides a chitosan composite film, comprising the following steps:
s10, preparing acidified carbon nanotubes;
s20, coating silicon dioxide on the surface of the acidified carbon nano tube to obtain a carbon nano tube coated with silicon dioxide;
s30, performing sulfonation modification on the silicon dioxide in the carbon nano tube coated with the silicon dioxide to obtain a carbon nano tube coated with modified silicon dioxide;
and S40, preparing the carbon nano tube coated with the modified silicon dioxide and a chitosan solution into a chitosan composite film.
Optionally, step S10 specifically includes:
adding the carbon nano tube into an acid solution, heating, stirring and refluxing to obtain a mixed solution, diluting the mixed solution, separating a solid product in the mixed solution, washing and drying the solid product to obtain the acidified carbon nano tube.
Optionally, step S20 specifically includes:
and adding the acidified carbon nano tube into the solution, uniformly dispersing to obtain a solution A, adding a silicon source into the solution A, uniformly stirring to obtain a solution B containing a solid, and separating the solid to obtain the carbon nano tube coated by the silicon dioxide.
Optionally, the mass ratio of the acidified nanotube to the silicon source is (1-2): (5-10).
Optionally, step S30 specifically includes:
s31, adding the carbon nano tube coated with the silicon dioxide into a solution, dispersing uniformly to obtain a solution C, adjusting the pH value of the solution C to 9-10, adding a (3-mercaptopropyl) trimethoxysilane solution into the solution C, mixing uniformly, washing, and drying to obtain a product D;
and S32, adding the product D into a hydrogen peroxide solution, reacting at 40-60 ℃, obtaining a mixed solution E containing a precipitate after the reaction is finished, and washing and drying the precipitate to obtain the carbon nano tube coated with the modified silicon dioxide.
Optionally, every 1-1.5 g of the silicon dioxide coated carbon nano tube is added, and 2mL of (3-mercaptopropyl) trimethoxy silane solution is correspondingly added.
Optionally, step S40 specifically includes:
adding the carbon nano tube coated by the modified silicon dioxide into a chitosan solution, uniformly dispersing to obtain a casting solution, preparing the casting solution into a film body by adopting a tape casting method, and performing post-treatment to obtain the chitosan composite film.
Optionally, the mass ratio of the chitosan in the chitosan solution to the modified silica-coated carbon nanotubes is 100: (1-7).
Optionally, the post-processing step comprises:
and adding the membrane body into a sodium hydroxide solution, then crosslinking in a sulfuric acid solution, and finally washing and drying to obtain the chitosan composite membrane.
Furthermore, the invention also provides a fuel cell, which comprises a proton exchange membrane, wherein the proton exchange membrane is the chitosan composite membrane prepared by the preparation method of the chitosan composite membrane.
In the technical scheme provided by the invention, the acidic carbon nano tube is prepared firstly, and the carbon nano tube is more easily dispersed in the chitosan solution through acidification treatment of the carbon nano tube; the carbon nano tube and the chitosan are compositely modified, the mechanical property of the prepared chitosan composite membrane is improved through the excellent mechanical property of the carbon nano tube, and meanwhile, the addition of the carbon nano tube is beneficial to constructing a long-range ordered proton transmission ascending channel, so that the proton conduction property is improved; the surface of the carbon nano tube is coated with the silicon dioxide, so that the dispersity of the carbon nano tube is further improved, the dispersing effect of the carbon nano tube in a chitosan matrix is further improved, and in addition, the surface coating treatment avoids direct contact among the carbon nano tubes, so that the short circuit risk caused by excellent conductivity of the carbon nano tube is avoided; furthermore, the proton conductivity is improved through the organic sulfonation treatment of the silicon dioxide on the surface of the carbon nano tube, and meanwhile, the dispersibility of the carbon nano tube in the chitosan is improved, so that the finally prepared chitosan composite membrane can meet the application requirement of the proton exchange membrane fuel cell.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of an embodiment of a method for preparing a chitosan composite membrane provided by the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Because the carbon nano tube is insoluble, surface chemically inert and large in specific surface area, the carbon nano tube is easy to agglomerate in an organic polymer matrix, low in bonding strength with the polymer matrix interface and poor in dispersibility, and the effect of directly compounding the carbon nano tube with a polymer is unsatisfactory, so that the comprehensive performance of the composite membrane serving as a proton exchange membrane is influenced.
In view of this, the invention provides a preparation method of a chitosan composite membrane, aiming at preparing a proton exchange membrane with excellent conductivity and mechanical properties. Fig. 1 shows an embodiment of a method for preparing a chitosan composite membrane according to the present invention. Referring to fig. 1, in the present embodiment, a method for preparing a chitosan composite membrane includes the following steps:
s10, preparing the acidified carbon nano tube.
In order to improve the dispersibility of the carbon nanotubes and make the carbon nanotubes more easily dispersed in the chitosan solution, in this embodiment, the carbon nanotubes are subjected to an acidification treatment. The acidified carbon nanotube generates carboxyl which has polarity, so that the dispersibility of the carbon nanotube in the solution is improved.
The present invention does not limit the specific steps of the acidification treatment as long as the acidic carbon nanotubes can be prepared, and in this embodiment, step S10 specifically includes: adding the carbon nano tube into an acid solution, heating, stirring and refluxing to obtain a mixed solution, diluting the mixed solution, separating a solid product in the mixed solution, washing and drying the solid product to obtain the acidified carbon nano tube.
Wherein the acid solution is concentrated sulfuric acid solution or concentrated nitric acid solution, preferably concentrated nitric acid solution. Further, the heating, stirring and refluxing temperature is 115-125 ℃, and the time is 4-6 hours. Thus, in this embodiment, step S10 is: adding a carbon nano tube into a concentrated nitric acid solution, stirring and carrying out reflux reaction for 4-6 hours at the temperature of 115-125 ℃ to obtain a mixed solution, adding the mixed solution into deionized water for dilution, then filtering to separate out a solid product in the mixed solution, washing the solid product to be neutral by using the deionized water, and then drying for 12-24 hours at the temperature of 90-110 ℃ to obtain the acidified carbon nano tube.
And S20, coating silicon dioxide on the surface of the acidified carbon nano tube to obtain the carbon nano tube coated with the silicon dioxide.
In the embodiment, the surface of the acidified carbon nanotube is coated with silicon dioxide, and the surface coating treatment effectively promotes the interaction force between the carbon nanotube and the polymer matrix, so that the compatibility and the dispersibility of the carbon nanotube and the polymer matrix are improved, and meanwhile, the construction of a new proton transmission channel is facilitated, and the proton transmission performance is improved; in addition, the surface coating treatment can effectively avoid direct contact between the carbon nanotubes, thereby shielding the electron transmission of the carbon nanotubes and further avoiding the short circuit risk caused by the excellent conductivity of the carbon nanotubes.
The present invention does not limit the specific step of coating the surface of the acidified carbon nanotube with silica as long as the silica-coated carbon nanotube can be obtained. In this embodiment, step S20 specifically includes: and adding the acidified carbon nano tube into the solution, uniformly dispersing to obtain a solution A, adding a silicon source into the solution A, uniformly stirring to obtain a solution B containing a solid, and separating the solid to obtain the carbon nano tube coated by the silicon dioxide.
Wherein the mass ratio of the acidified nanotube to the silicon source is (1-2): (5-10). The silicon source may be methyl orthosilicate or ethyl orthosilicate, and in this embodiment, the silicon source is ethyl orthosilicate. In order to facilitate uniform dispersion of the acidified carbon nanotubes in the solution, in this embodiment, the step of adding the acidified carbon nanotubes into the solution to obtain the solution a after uniform dispersion includes: and adding the acidified carbon nano tube into a mixed solution of ethanol and deionized water, and performing ultrasonic treatment at room temperature for 30-50 min to obtain a solution A. Preferably, the volume of the ethanol and the deionized water in the mixed solution is 3: 1. It is understood that after the solid is separated, the solid is washed to remove impurities, and in order to achieve a better cleaning effect, in this embodiment, the solid is washed with deionized water and ethanol in sequence to obtain silica-coated carbon nanotubes.
In specific implementation, step S20 includes: adding 1-2 parts by mass of the acidified carbon nano tube into a mixed solution of ethanol and deionized water, performing ultrasonic treatment at room temperature for 30-50 min, dispersing uniformly to obtain a solution A, adding 5-10 parts by mass of ethyl orthosilicate into the solution A, stirring for 10-14 h to obtain a solution B containing solids, centrifuging to separate out the solids, and washing with deionized water and ethanol in sequence to obtain the carbon nano tube coated with silicon dioxide. Wherein the volume of the deionized water for washing is 1-3 times of that of the solid, and the volume of the ethanol for washing is 2-4 times of that of the solid.
S30, performing sulfonation modification on the silicon dioxide in the carbon nano tube coated with the silicon dioxide to obtain the carbon nano tube coated with the modified silicon dioxide.
In order to further improve the interaction force, the compatibility and the dispersibility between the carbon nanotube and the chitosan matrix and furthest exert the specific performance advantages of the carbon nanotube, in the embodiment, the surface area of the silicon dioxide is further subjected to organic sulfonation treatment on the basis of coating the surface of the carbon nanotube with the silicon dioxide, and in addition, the introduction of the sulfonic acid group provides richer proton action sites, and the introduction of the sulfonic acid group is combined with the specific one-dimensional rod-shaped morphology characteristics of the carbon nanotube, so that the construction of a long-range ordered proton transmission channel is facilitated, and the conductivity of the prepared chitosan composite membrane is improved.
The invention is not limited to the specific step of performing sulfonation modification on the silica in the silica-coated carbon nanotube, and in this embodiment, the step S30 specifically includes:
s31, adding the carbon nano tube coated with the silicon dioxide into the solution, dispersing uniformly to obtain a solution C, adjusting the pH value of the solution C to 9-10, adding a (3-mercaptopropyl) trimethoxysilane solution into the solution C, mixing uniformly, washing, and drying to obtain a product D.
And adjusting the pH value of the solution C to 9-10 to provide proper reaction conditions for subsequent reaction, so that the reaction is facilitated. The (3-mercaptopropyl) trimethoxysilane can be used as a silane coupling agent, improves the dispersibility of the carbon nano tube coated by the silicon dioxide in a solution, and provides sulfydryl so as to carry out organic sulfonation treatment on the silicon dioxide.
Wherein, every time 1-1.5 g of the carbon nano tube coated by the silicon dioxide is added, 2mL of (3-mercaptopropyl) trimethoxy silane solution is correspondingly added. The (3-mercaptopropyl) trimethoxysilane solution, i.e. MPTMS, is hereinafter referred to as MPTMS for convenience of description. In order to uniformly disperse the carbon nanotubes coated with the silicon dioxide in the solution, in this embodiment, the carbon nanotubes coated with the silicon dioxide are added into a mixed solution of ethanol and water, and the mixture is subjected to ultrasound for 30 to 50min at room temperature. Preferably, the volume ratio of the ethanol to the deionized water in the mixed solution is 1: 1.
In specific implementation, step S31 is: adding 1-1.5 g of the silicon dioxide coated carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of the ethanol to the deionized water is 1:1), performing ultrasonic treatment at room temperature for 30-50 min, dispersing uniformly to obtain a solution C, adjusting the pH of the solution C to 9-10, dropwise adding 2mL of (3-mercaptopropyl) trimethoxysilane solution into the solution C, stirring for 10-14 h, washing with deionized water and ethanol in sequence, and then heating and drying to obtain a product D.
And S32, adding the product D into a hydrogen peroxide solution, reacting at 40-60 ℃, obtaining a mixed solution E containing a precipitate after the reaction is finished, and washing and drying the precipitate to obtain the carbon nano tube coated with the modified silicon dioxide.
Wherein the mass concentration of the hydrogen peroxide solution is 10%. In a preferred embodiment, the step S32 is: and adding the product D into a hydrogen peroxide solution with the mass concentration of 10%, reacting for 5-8 h at 50 ℃ to obtain a mixed solution E containing a precipitate, washing the precipitate with deionized water, and heating and drying to obtain the carbon nano tube coated with the modified silicon dioxide. The volume of the deionized water for washing is 1-3 times of that of the precipitate.
And S40, preparing the carbon nano tube coated with the modified silicon dioxide and a chitosan solution into a chitosan composite film.
The carbon nano tube and the chitosan are modified in a composite mode, the mechanical property of the prepared chitosan composite membrane is improved through the excellent mechanical property of the carbon nano tube, and meanwhile, the proton conduction performance is favorably improved due to the addition of the carbon nano tube. In this embodiment, step S40 specifically includes: adding the carbon nano tube coated by the modified silicon dioxide into a chitosan solution, uniformly dispersing to obtain a casting solution, preparing the casting solution into a film body by adopting a tape casting method, and performing post-treatment to obtain the chitosan composite film.
In this example, the chitosan solution was formulated as: and dissolving chitosan in the acetic acid solution to obtain a chitosan solution. Wherein the mass ratio of the chitosan in the chitosan solution to the carbon nano tube coated by the modified silicon dioxide is 100: (1-7). The sodium hydroxide concentration was 5 wt.%, the sulfuric acid concentration was 2M-furthermore, in this example, the post-treatment step included: and adding the membrane body into a sodium hydroxide solution, then crosslinking in a sulfuric acid solution, and finally washing and drying to obtain the chitosan composite membrane. The membrane body can be doped by soaking the membrane body in an alkaline solution containing hydroxide ions, so that the alkaline chitosan composite membrane with excellent comprehensive performance is finally obtained, and the alkaline chitosan composite membrane serving as a proton exchange membrane is applied to a fuel cell, so that the running time of the cell in an alkaline environment can be prolonged.
In specific implementation, step S40 is: adding 0.01-0.07 g of the carbon nano tube coated by the modified silicon dioxide into an ethanol solution, then performing ultrasonic dispersion uniformly, adding the mixture into a chitosan solution (wherein the mass of chitosan is 1g), stirring for 2-3 h to uniformly mix the mixture to obtain a casting solution, casting the casting solution on a clean glass plate to prepare a membrane (namely preparing the membrane by a casting method), drying at 50-70 ℃ to obtain a membrane body, adding the membrane body into a sodium hydroxide solution, then performing crosslinking in a sulfuric acid solution, finally washing with deionized water, and drying to obtain a chitosan composite membrane, namely the organic sulfonic acid modified carbon nano tube/chitosan composite proton exchange membrane.
The invention further provides a fuel cell which comprises a proton exchange membrane, wherein the proton exchange membrane is a chitosan composite membrane prepared by the preparation method of the chitosan composite membrane. The specific preparation method of the chitosan composite membrane refers to the above embodiments, and since the fuel cell of the present invention adopts all the technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.
The technical solutions of the present invention are further described in detail below with reference to specific examples and drawings, it should be understood that the following examples are merely illustrative of the present invention and are not intended to limit the present invention.
In the following examples, the source information of the raw materials used is as follows: deionized water is self-made in a laboratory; absolute ethyl alcohol is analytically pure, and is a group of Chinese medicines; MPTMS is analytically pure, Aladdin reagent Co., Ltd; chitosan Mw 1000kda, degree of deacetylation 92.5%, Zhejiang gold Chitosan Biochemical Co., Ltd; acetic acid was analytically pure, a group of national drugs.
Example 1
(1) Adding 2g of carbon nano tube into 120mL of concentrated nitric acid solution, stirring and refluxing for reaction for 4h at 120 ℃ to obtain a mixed solution, pouring the mixed solution into a proper amount of deionized water, performing suction filtration by using a cellulose ester membrane (the aperture is 0.22 mu m) to separate a solid product in the mixed solution, repeatedly washing the solid product by using deionized water until the filtrate is neutral, and drying for 12h at 100 ℃ to obtain the acidified carbon nano tube.
(2) Adding 1g of acidified carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of ethanol to deionized water is 3:1), performing ultrasonic treatment for 30min at room temperature, uniformly dispersing to obtain a solution A, adding 10g of tetraethoxysilane into the solution A, stirring for 12h at room temperature to obtain a solution B containing solids, centrifuging to separate out the solids, and washing with deionized water and ethanol in sequence to obtain the carbon nano tube coated with silicon dioxide.
(3) Adding 1g of silicon dioxide coated carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of the ethanol to the deionized water is 1:1), carrying out ultrasonic treatment for 30min at room temperature, uniformly dispersing to obtain a solution C, adjusting the pH of the solution C to 9, dropwise adding 2mL of (3-mercaptopropyl) trimethoxysilane solution into the solution C, stirring for 12h at room temperature, washing with deionized water and ethanol respectively, and drying for 12h at 80 ℃ to obtain a product D.
(4) And adding 1g of the product D into a hydrogen peroxide solution with the mass concentration of 10%, reacting for 8 hours at 50 ℃ to obtain a mixed solution E containing precipitates, washing the precipitates with deionized water, and drying for 12 hours at 80 ℃ to obtain the modified silicon dioxide coated carbon nanotube.
(5) Adding 0.01g of the carbon nano tube coated by the modified silicon dioxide into 10-15 mL of ethanol solution, then ultrasonic treatment is carried out for 20min to ensure that the solution is uniformly dispersed to obtain solution F, 1.0g of chitosan solid is added into another clean 100ml beaker, then adding 25ml of 2 vol.% acetic acid solution, ultrasonically stirring and dissolving to obtain chitosan solution, mixing the solution F and the chitosan solution, stirring for 2h at room temperature, performing ultrasonic treatment for 30min, standing for defoaming to obtain a membrane casting solution, casting the membrane casting solution on a clean glass plate to prepare a membrane (namely preparing the membrane by a casting method), drying for 24h at 60 ℃ to obtain a membrane body, soaking the membrane body in 5 wt.% of sodium hydroxide solution for 3h, removing residual acetic acid in the membrane, cleaning with deionized water, and then crosslinking the chitosan composite membrane in a 2M sulfuric acid solution for 24 hours, finally washing the chitosan composite membrane to be neutral by using deionized water, and drying the chitosan composite membrane for 24 hours at the temperature of 40 ℃ to obtain the chitosan composite membrane.
Example 2
The same procedure as in example 1 was repeated except that 0.03g of the modified silica-coated carbon nanotubes (i.e., the mass ratio of chitosan to modified silica-coated carbon nanotubes was 100:3) was used in step (5).
Example 3
The same procedure as in example 1 was repeated except that 0.05g of the modified silica-coated carbon nanotubes (i.e., the mass ratio of chitosan to modified silica-coated carbon nanotubes was 100:5) was used in step (5).
Example 4
The same procedure as in example 1 was repeated, except that 0.07g of the modified silica-coated carbon nanotubes (i.e., the mass ratio of chitosan to modified silica-coated carbon nanotubes was 100:7) was used in step (5).
Example 5
(1) Adding 2g of carbon nano tube into 120mL of concentrated nitric acid solution, stirring and refluxing for reaction for 6h at 115 ℃ to obtain a mixed solution, pouring the mixed solution into a proper amount of deionized water, performing suction filtration by using a cellulose ester membrane (the aperture is 0.22 mu m) to separate a solid product in the mixed solution, repeatedly washing the solid product by using deionized water until the filtrate is neutral, and drying for 24h at 90 ℃ to obtain the acidified carbon nano tube.
(2) Adding 2g of acidified carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of ethanol to deionized water is 3:1), performing ultrasonic treatment at room temperature for 40min, dispersing uniformly to obtain a solution A, adding 10g of tetraethoxysilane into the solution A, stirring at room temperature for 10h to obtain a solution B containing solids, centrifuging to separate out the solids, and washing with deionized water and ethanol in sequence to obtain the carbon nano tube coated with silicon dioxide.
(3) Adding 1.2g of silicon dioxide coated carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of the ethanol to the deionized water is 1:1), carrying out ultrasonic treatment for 50min at room temperature, uniformly dispersing to obtain a solution C, adjusting the pH value of the solution C to 10, dropwise adding 2mL of (3-mercaptopropyl) trimethoxysilane solution into the solution C, stirring for 14h at room temperature, washing with deionized water and ethanol respectively, and drying for 12h at 80 ℃ to obtain a product D.
(4) And adding 1g of the product D into a hydrogen peroxide solution with the mass concentration of 10%, reacting for 7h at 40 ℃ to obtain a mixed solution E containing precipitates, washing the precipitates with deionized water, and drying for 12h at 80 ℃ to obtain the modified silicon dioxide coated carbon nanotube.
(5) Adding 0.01g of the carbon nano tube coated by the modified silicon dioxide into 10-15 mL of ethanol solution, then ultrasonic treatment is carried out for 20min to ensure that the solution is uniformly dispersed to obtain solution F, 1.0g of chitosan solid is added into another clean 100ml beaker, then adding 25ml of 2 vol.% acetic acid solution, ultrasonically stirring and dissolving to obtain chitosan solution, mixing the solution F and the chitosan solution, stirring for 2h at room temperature, performing ultrasonic treatment for 30min, standing for defoaming to obtain a membrane casting solution, casting the membrane casting solution on a clean glass plate to prepare a membrane (namely preparing the membrane by a casting method), drying for 24h at 60 ℃ to obtain a membrane body, soaking the membrane body in 5 wt.% of sodium hydroxide solution for 3h, removing residual acetic acid in the membrane, cleaning with deionized water, and then crosslinking the chitosan composite membrane in a 2M sulfuric acid solution for 24 hours, finally washing the chitosan composite membrane to be neutral by using deionized water, and drying the chitosan composite membrane for 24 hours at the temperature of 40 ℃ to obtain the chitosan composite membrane.
Example 6
(1) Adding 2g of carbon nano tube into 120mL of concentrated nitric acid solution, stirring and refluxing for 5h at 125 ℃ to obtain a mixed solution, pouring the mixed solution into a proper amount of deionized water, performing suction filtration by using a cellulose ester membrane (the aperture is 0.22 mu m) to separate a solid product in the mixed solution, repeatedly washing the solid product by using deionized water until the filtrate is neutral, and drying for 15h at 110 ℃ to obtain the acidified carbon nano tube.
(2) Adding 1.2g of acidified carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of ethanol to deionized water is 3:1), performing ultrasonic treatment for 30min at room temperature, uniformly dispersing to obtain a solution A, adding 8g of tetraethoxysilane into the solution A, stirring for 12h at room temperature to obtain a solution B containing solids, centrifuging to separate out the solids, and washing with deionized water and ethanol in sequence to obtain the carbon nano tube coated with silicon dioxide.
(3) Adding 1.5g of silicon dioxide coated carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of the ethanol to the deionized water is 1:1), carrying out ultrasonic treatment for 30min at room temperature, uniformly dispersing to obtain a solution C, adjusting the pH value of the solution C to 9, dropwise adding 2mL (3-mercaptopropyl) trimethoxysilane solution into the solution C, stirring for 12h at room temperature, washing with deionized water and ethanol respectively, and drying for 12h at 80 ℃ to obtain a product D.
(4) And adding 1g of the product D into a hydrogen peroxide solution with the mass concentration of 10%, reacting for 5h at 60 ℃ to obtain a mixed solution E containing precipitates, washing the precipitates with deionized water, and drying for 12h at 80 ℃ to obtain the modified silicon dioxide coated carbon nanotube.
(5) Adding 0.01g of the carbon nano tube coated by the modified silicon dioxide into 10-15 mL of ethanol solution, then ultrasonic treatment is carried out for 20min to ensure that the solution is uniformly dispersed to obtain solution F, 1.0g of chitosan solid is added into another clean 100ml beaker, then adding 25ml of 2 vol.% acetic acid solution, ultrasonically stirring and dissolving to obtain chitosan solution, mixing the solution F and the chitosan solution, stirring for 2h at room temperature, performing ultrasonic treatment for 30min, standing for defoaming to obtain a membrane casting solution, casting the membrane casting solution on a clean glass plate to prepare a membrane (namely preparing the membrane by a casting method), drying for 24h at 60 ℃ to obtain a membrane body, soaking the membrane body in 5 wt.% of sodium hydroxide solution for 3h, removing residual acetic acid in the membrane, cleaning with deionized water, and then crosslinking the chitosan composite membrane in a 2M sulfuric acid solution for 24 hours, finally washing the chitosan composite membrane to be neutral by using deionized water, and drying the chitosan composite membrane for 24 hours at the temperature of 40 ℃ to obtain the chitosan composite membrane.
Comparative example 1
Weighing 1.0g of chitosan, adding 25mL of 2 vol.% acetic acid solution, performing ultrasonic treatment and stirring until the chitosan is completely dissolved to form a uniform solution, standing and defoaming for 1h, then uniformly distributing the mixed solution on a clean glass plate for casting film, drying at 80 ℃, cooling to room temperature, demolding, soaking the film in 5 wt.% sodium hydroxide solution for 3h, removing residual acetic acid in the film, and then cleaning with deionized water. And then putting the obtained membrane into 2M sulfuric acid solution, crosslinking for 24h, washing with deionized water to be neutral, and finally drying at 40 ℃ for 24h to obtain the pure chitosan membrane.
Comparative example 2
(1) Adding 2g of carbon nano tube into 120mL of concentrated nitric acid solution, stirring and refluxing for reaction for 4h at 120 ℃ to obtain a mixed solution, pouring the mixed solution into a proper amount of deionized water, performing suction filtration by using a cellulose ester membrane (the aperture is 0.22 mu m) to separate a solid product in the mixed solution, repeatedly washing the solid product by using deionized water until the filtrate is neutral, and drying for 12h at 100 ℃ to obtain the acidified carbon nano tube.
(2) Adding 0.01g of the acidified carbon nanotube into 10-15 mL of ethanol solution, then ultrasonic treatment is carried out for 20min to ensure that the solution is uniformly dispersed to obtain solution F, 1.0g of chitosan solid is added into another clean 100ml beaker, then adding 25ml of 2 vol.% acetic acid solution, ultrasonically stirring and dissolving to obtain chitosan solution, mixing the solution F and the chitosan solution, stirring for 2h at room temperature, performing ultrasonic treatment for 30min, standing for defoaming to obtain a membrane casting solution, casting the membrane casting solution on a clean glass plate to prepare a membrane (namely preparing the membrane by a casting method), drying for 24h at 60 ℃ to obtain a membrane body, soaking the membrane body in 5 wt.% of sodium hydroxide solution for 3h, removing residual acetic acid in the membrane, cleaning with deionized water, and then crosslinking the composite membrane in a 2M sulfuric acid solution for 24 hours, finally washing the composite membrane to be neutral by using deionized water, and drying the composite membrane for 24 hours at the temperature of 40 ℃ to obtain the carbon nanotube/chitosan composite membrane.
Comparative example 3
(1) Adding 2g of carbon nano tube into 120mL of concentrated nitric acid solution, stirring and refluxing for reaction for 4h at 120 ℃ to obtain a mixed solution, pouring the mixed solution into a proper amount of deionized water, performing suction filtration by using a cellulose ester membrane (the aperture is 0.22m) to separate a solid product in the mixed solution, repeatedly washing the solid product by using deionized water until the filtrate is neutral, and drying for 12h at 100 ℃ to obtain the acidified carbon nano tube.
(2) Adding 1g of acidified carbon nano tube into a mixed solution of ethanol and deionized water (the volume ratio of ethanol to deionized water is 3:1), performing ultrasonic treatment for 30min at room temperature, uniformly dispersing to obtain a solution A, adding 10g of tetraethoxysilane into the solution A, stirring for 12h at room temperature to obtain a solution B containing solids, centrifuging to separate out the solids, and washing with deionized water and ethanol in sequence to obtain the carbon nano tube coated with silicon dioxide.
(3) Adding 0.01g of the carbon nano tube coated by the silicon dioxide into 10-15 mL of ethanol solution, then ultrasonic treatment is carried out for 20min to ensure that the solution is uniformly dispersed to obtain solution F, 1.0g of chitosan solid is added into another clean 100ml beaker, then adding 25ml of 2 vol.% acetic acid solution, ultrasonically stirring and dissolving to obtain chitosan solution, mixing the solution F and the chitosan solution, stirring for 2h at room temperature, performing ultrasonic treatment for 30min, standing for defoaming to obtain a membrane casting solution, casting the membrane casting solution on a clean glass plate to prepare a membrane (namely preparing the membrane by a casting method), drying for 24h at 60 ℃ to obtain a membrane body, soaking the membrane body in 5 wt.% of sodium hydroxide solution for 3h, removing residual acetic acid in the membrane, cleaning with deionized water, and then crosslinking the carbon nanotube/chitosan composite membrane in a 2M sulfuric acid solution for 24 hours, finally washing the carbon nanotube/chitosan composite membrane to be neutral by deionized water, and drying the carbon nanotube/chitosan composite membrane for 24 hours at the temperature of 40 ℃ to obtain the carbon nanotube/chitosan composite membrane coated by silicon dioxide.
The chitosan composite membrane prepared by the embodiment and the comparative ratio is subjected to performance test, and the test method comprises the following steps:
(1) proton conductivity: the resistance of the film was tested on a frequency response analyzer using an ac impedance method with a frequency sweep range of 1-106Hz and an ac signal amplitude of 100 mV. The proton conductivity σ (S/cm) of the cut membrane (1.5cm × 2.5cm) was calculated by the following formula:
in the formula, L and A are respectively the distance (cm) between two electrodes and the effective cross-sectional area (cm2) of the film to be tested between the two electrodes, R is the resistance (omega) of the film, and the data obtained by the alternating current impedance test are calculated.
(2) Tensile strength: the film was cut into a rectangular specimen having a length of 30mm and a width of 10mm, and the specimen was tested on an electronic tensile machine at a tensile speed of 2 mm/min.
The test results are shown in table 1 below.
Table 1 results of performance testing
| Performance index (Room temperature test) | Proton conductivity (mS. cm)-1) | Tensile Strength (MPa) |
| Example 1 | 15.7 | 22.4 |
| Example 2 | 20.3 | 29.3 |
| Example 3 | 31.2 | 35.9 |
| Example 4 | 28.5 | 30.6 |
| Comparative example 1 | 13.1 | 15.2 |
| Comparative example 2 | 15.2 | 20.1 |
| Comparative example 3 | 20.3 | 23.2 |
As can be seen from table 1, the proton conductivity and tensile strength of the chitosan composite membrane prepared in the embodiment of the present invention are superior to those of the comparative example, that is, when the chitosan composite membrane prepared by the preparation method of the chitosan composite membrane provided by the present invention is applied to a fuel cell, the mechanical properties and proton conductivity of the chitosan composite membrane are excellent, so that the market competitiveness of the chitosan composite membrane is improved.
Since the ratio of chitosan to the modified carbon nanotubes in examples 5 and 6 is 100:1, the chitosan composite films prepared from the chitosan composite films and the chitosan composite film in example 1 have similar performance, and both the mechanical performance and the proton transmission performance are better than those of the comparative example, which is not described herein again.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (10)
1. The preparation method of the chitosan composite film is characterized by comprising the following steps:
s10, preparing acidified carbon nanotubes;
s20, coating silicon dioxide on the surface of the acidified carbon nano tube to obtain a carbon nano tube coated with silicon dioxide;
s30, performing sulfonation modification on the silicon dioxide in the carbon nano tube coated with the silicon dioxide to obtain a carbon nano tube coated with modified silicon dioxide;
and S40, preparing the carbon nano tube coated with the modified silicon dioxide and a chitosan solution into a chitosan composite film.
2. The method for preparing the chitosan composite membrane according to claim 1, wherein the step S10 specifically comprises:
adding the carbon nano tube into an acid solution, heating, stirring and refluxing to obtain a mixed solution, diluting the mixed solution, separating a solid product in the mixed solution, washing and drying the solid product to obtain the acidified carbon nano tube.
3. The method for preparing the chitosan composite membrane according to claim 1, wherein the step S20 specifically comprises:
and adding the acidified carbon nano tube into the solution, uniformly dispersing to obtain a solution A, adding a silicon source into the solution A, uniformly stirring to obtain a solution B containing a solid, and separating the solid to obtain the carbon nano tube coated by the silicon dioxide.
4. The preparation method of the chitosan composite film according to claim 3, wherein the mass ratio of the acidified nanotube to the silicon source is (1-2): (5-10).
5. The method for preparing the chitosan composite membrane according to claim 1, wherein the step S30 specifically comprises:
s31, adding the carbon nano tube coated with the silicon dioxide into a solution, dispersing uniformly to obtain a solution C, adjusting the pH value of the solution C to 9-10, adding a (3-mercaptopropyl) trimethoxysilane solution into the solution C, mixing uniformly, washing, and drying to obtain a product D;
and S32, adding the product D into a hydrogen peroxide solution, reacting at 40-60 ℃, obtaining a mixed solution E containing a precipitate after the reaction is finished, and washing and drying the precipitate to obtain the carbon nano tube coated with the modified silicon dioxide.
6. The method for preparing the chitosan composite membrane according to claim 5, wherein 2mL of (3-mercaptopropyl) trimethoxysilane solution is added for every 1-1.5 g of the silica-coated carbon nanotubes.
7. The method for preparing the chitosan composite membrane according to claim 1, wherein the step S40 specifically comprises:
adding the carbon nano tube coated by the modified silicon dioxide into a chitosan solution, uniformly dispersing to obtain a casting solution, preparing the casting solution into a film body by adopting a tape casting method, and performing post-treatment to obtain the chitosan composite film.
8. The method for preparing the chitosan composite membrane according to claim 7, wherein the mass ratio of the chitosan in the chitosan solution to the modified silica-coated carbon nanotubes is 100: (1-7).
9. The method of preparing a chitosan composite membrane according to claim 7, wherein the post-treatment step comprises:
and adding the membrane body into a sodium hydroxide solution, then crosslinking in a sulfuric acid solution, and finally washing and drying to obtain the chitosan composite membrane.
10. A fuel cell comprising a proton exchange membrane, wherein the proton exchange membrane is a chitosan composite membrane produced by the method for producing a chitosan composite membrane according to any one of claims 1 to 9.
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