CN115312788A - Gas diffusion electrode capable of realizing phase conversion under normal temperature and light pressure as well as preparation method and application of gas diffusion electrode - Google Patents
Gas diffusion electrode capable of realizing phase conversion under normal temperature and light pressure as well as preparation method and application of gas diffusion electrode Download PDFInfo
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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
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/88—Processes of manufacture
- H01M4/8803—Supports for the deposition of the catalytic active composition
- H01M4/8807—Gas diffusion layers
-
- 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
- H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
- H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
Abstract
A gas diffusion electrode converted under normal temperature and light pressure and a preparation method and application thereof, wherein the gas diffusion layer is formed by crosslinking a hydrophobic gas-permeable membrane so as to enhance the organic solvent resistance and water pressure resistance of the electrode; the catalyst layer is a mixture of cheap activated carbon, carbon black and a high molecular binder. Coating the mixture on a support layer, covering the mixture with a hydrophobic and breathable membrane subjected to cross-linking treatment, and rolling to ensure uniform distribution of the catalyst. And (3) putting the rolled electrode in water for phase inversion and drying to obtain the gas diffusion electrode inverted under normal temperature and light pressure. The gas diffusion electrode disclosed by the invention has the advantages of cheap and easily-obtained raw materials, simple method, easiness in preparation and large-scale production potential. The gas diffusion electrode synthesized by the method can be applied to in-situ electrosynthesis of H 2 O 2 And the field of environmental pollution remediation.
Description
Technical Field
The invention belongs to the technical field of electrochemical synthesis, and particularly relates to a gas diffusion electrode converted under normal temperature and light pressure, and a preparation method and application thereof.
Background
The gas diffusion electrode is a porous membrane electrode with conductivity, water resistance, air permeability and high activity. Due to its low cost and easy production, it has been widely used in the fields of fuel cells, chemical synthesis, and wastewater treatment. The gas diffusion electrode generally comprises a gas diffusion layer, a catalyst layer and a support layer, wherein the gas diffusion layer mainly provides a quick and efficient transmission channel for oxygen participating in electrode reaction, a solid catalyst can be simultaneously contacted with electrolyte and air or oxygen, so that the catalyst layer forms a structure with a stable solid, liquid and gas three-phase interface, and the support layer is used as a support framework of the gas diffusion electrode to enhance the mechanical strength of the gas diffusion electrode. The gas diffusion electrode can be applied to an anode or a cathode, wherein the gas diffusion electrode applied to the cathode can directly utilize oxygen in the air to rapidly act on the active center of the cathode, so that the energy consumption in the electrochemical oxygen reduction reaction process is reduced.
Conventional gas diffusion electrodes are synthesized by applying a paste-like mixture of catalyst and binder directly onto a support layer. In practical application, the traditional direct coating method can cause the electrode catalyst layer to be unevenly distributed, thereby reducing the performance of the electrode. In the prior art 1, in order to solve the problem of uneven electrode preparation by a direct coating method, a roller method is adopted to prepare a gas diffusion electrode, wherein a press device is required to perform high-pressure rolling on the electrode in the preparation process of the traditional roller method, the failure rate is high, and the cost is high; in addition, polytetrafluoroethylene is selected as the binder in the traditional roller method, but the polytetrafluoroethylene needs to be bonded by hot pressing (namely, a high-temperature and high-pressure mode) to form a uniform waterproof gas diffusion layer, and energy consumption is increased due to heating and pressurizing.
Prior art 2 uses polyvinylidene fluoride (PVDF) as a binder to form a gas diffusion layer by phase inversion. However, the method has three disadvantages: firstly, polyvinylidene fluoride is only dissolved in a few organic solvents due to the stable chemical property of the polyvinylidene fluoride, and the organic solvents are released in the phase inversion process to dissolve the gas diffusion layer; secondly, the gas diffusion layer formed by the method is uneven, a gas diffusion channel is hidden due to migration of electrolyte, gas mass transfer is limited, a three-phase interface disappears, and reactive sites are reduced; thirdly, along with the migration of the electrolyte in the reactor, the pressure of the electrolyte on the electrode is not uniform, so that the pressure at the defect part is easily overlarge, and the liquid leakage phenomenon is caused.
Disclosure of Invention
The invention aims to overcome the defects of low mechanical strength, uneven distribution of a catalyst layer, complex preparation process and high energy consumption of the gas diffusion layer of the conventional gas diffusion electrode, and provides a preparation method of a gas diffusion electrode converted under normal temperature and light pressure. The electrode can be prepared in large scale at normal temperature and normal pressure, the mechanical property of the gas diffusion layer is improved, the catalyst layer is uniformly distributed, and the capability of generating hydrogen peroxide in situ is realized; and the adopted raw materials are economical and easy to obtain, the process operation is convenient, the mass production is easy, and the method is suitable for industrial application.
The invention provides a preparation method of a gas diffusion electrode converted under normal temperature and light pressure, which comprises the following steps:
the hydrophobic porous polymer film is subjected to crosslinking reaction in the presence of a crosslinking agent to obtain an organic solvent-resistant hydrophobic breathable film;
mixing a binder with a carbon material to obtain a paste mixture;
coating the pasty mixture on a support, then covering the support with the hydrophobic breathable film resistant to the organic solvent, and uniformly rolling the support with a rolling shaft at low pressure to obtain a primary gas diffusion electrode;
and (3) soaking the primary gas diffusion electrode in deionized water to induce phase inversion, and drying to obtain the gas diffusion electrode inverted under normal temperature and light pressure.
Optionally, the hydrophobic porous polymer membrane is one of a PVDF membrane or a PTFE membrane.
Optionally, the crosslinking agent is one or more of ethylenediamine, bisphenol, peroxide and mercaptan.
Optionally, the reaction temperature of the crosslinking reaction is 40-100 ℃, and the reaction time is 5-180 s.
Optionally, the carbon material comprises activated carbon and carbon black, and the mass ratio of the activated carbon to the carbon black is 1-50: 1.
optionally, the binder is one or more of a PVDF solution, a PSF solution and a PES solution, the concentration of PVDF in the PVDF solution is 5-30% (w/v), and the mass ratio of the activated carbon to the PVDF is 1-10: 1.
optionally, the phase inversion time is 10-60 min.
Optionally, the support body is one or more of a stainless steel net, a titanium net, carbon cloth, a carbon felt and carbon paper.
The second aspect of the invention provides a normal-temperature light-pressure inversion gas diffusion electrode prepared by the preparation method of the first aspect.
The third aspect of the invention provides an application of the normal-temperature light-pressure phase-inversion gas diffusion electrode prepared by the preparation method of the first aspect as a cathode in preparation of hydrogen peroxide.
Compared with the prior art, the invention has the beneficial effects that:
(1) The method for preparing the gas diffusion electrode at normal temperature and under light pressure adopts cheap and easily-obtained carbon materials as raw materials, has simple preparation process, is easy to operate and control, and is beneficial to large-scale production.
(2) The gas diffusion electrode is prepared by a rolling shaft method, the catalyst layer is uniformly distributed, a stable solid-liquid-gas three-phase interface is formed, and the problem of electrode liquid leakage caused by uneven coating of the catalyst by a coating method is solved.
(3) The invention treats the hydrophobic porous gas diffusion layer in advance through a crosslinking reaction, enhances the mechanical strength of the gas diffusion layer and enables the gas diffusion layer to resist organic solvents, so that the gas diffusion electrode can still keep stable in the phase inversion process.
(4) The normal-temperature light-pressure phase-inversion gas diffusion electrode synthesized by the method can generate hydrogen peroxide in situ, no additional reagent is needed, hydrogen peroxide with higher concentration can be generated at lower current density only by active mass transfer of oxygen in the air, the raw materials and the product are environment-friendly, and the reaction cost is reduced.
In conclusion, the invention optimizes the electrode composition, such as the materials of the gas diffusion layer and the catalyst layer, and improves the preparation process, and develops the gas diffusion electrode which is resistant to organic solvents, low in cost, simple and convenient in process and excellent in performance, so that the gas diffusion electrode can achieve the capability of efficiently and stably producing hydrogen peroxide. The invention synthesizes the normal-temperature light-pressure phase inversion gas diffusion electrode, and the gas diffusion electrode is used for in-situ hydrogen peroxide production, so that a high-efficiency and stable electrode material is obtained, and research ideas and theoretical supports are provided for developing electrochemical synthesis with development prospects.
Drawings
In fig. 1, a is an SEM characterization result of the PVDF film provided in the embodiment of the present invention, and B is an SEM characterization result of the PVDF film after the cross-linking reaction;
in fig. 2, a is an SEM characterization result of the PVDF membrane provided in the embodiment of the present invention with respect to the tolerance to the organic solvent, and B is an SEM characterization result of the PVDF membrane after the cross-linking reaction with respect to the tolerance to the organic solvent;
FIG. 3 is a comparison graph of XPS characterization results of PVDF films before and after the cross-linking reaction provided by the examples of the present invention;
FIG. 4 is a schematic diagram of the change in current density concentration and the change in current density current efficiency for hydrogen peroxide generation using a gas diffusion electrode as a cathode according to an embodiment of the present invention;
fig. 5 is a schematic structural view of a gas diffusion electrode prepared in an embodiment of the present invention.
Detailed Description
The present application is further described below with reference to the accompanying drawings. The following examples are only used to illustrate the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.
The embodiment of the invention provides a preparation method of a gas diffusion electrode converted under normal temperature and light pressure, which comprises a step S1 to a step S4.
S1, carrying out a crosslinking reaction on the hydrophobic porous polymer film in the presence of a crosslinking agent to obtain the organic solvent-resistant hydrophobic breathable film.
According to the embodiment of the invention, the hydrophobic porous gas diffusion layer is pretreated through a crosslinking reaction, so that the mechanical strength of the gas diffusion layer is enhanced, and the gas diffusion layer is resistant to an organic solvent, so that the gas diffusion electrode can still keep stable in a phase inversion process. The hydrophobic porous polymer membrane is one of PVDF membrane or PTFE membrane, the cross-linking agent is one or the combination of at least two of ethylenediamine, bisphenol, peroxide and mercaptan, the reaction temperature of the cross-linking reaction is 40-100 ℃, and the reaction time is 5-180 s.
In some preferred embodiments, after the crosslinking reaction, the film is washed three times with deionized water and then dried in an oven to yield an organic solvent resistant hydrophobic breathable film.
And S2, mixing the binder with the carbon material to obtain a pasty mixture.
The binder is one or more of PVDF solution, polysulfone (PSF) solution and Polyethersulfone (PES) solution, the carbon material comprises activated carbon and carbon black,
in some preferred embodiments, the binder is a PVDF solution, the concentration of PVDF in the PVDF solution is 5-30% (w/v), and the mass ratio of activated carbon to carbon black in the carbon material is 1-50: 1, the mass ratio of the activated carbon to the PVDF solute in the PVDF solution is 1-10: 1. the PVDF solution and the carbon material are thoroughly stirred to form a paste-like mixture.
And S3, coating the pasty mixture on a support, then covering the support with the organic solvent-resistant hydrophobic breathable film, and uniformly rolling by using a rolling shaft at low pressure to obtain a primary gas diffusion electrode.
Pouring the pasty mixture on a support, covering a hydrophobic porous polymer film after cross-linking reaction, namely an organic solvent-resistant hydrophobic breathable film, and slightly pressing and flattening the hydrophobic porous polymer film by using a rolling shaft to obtain a primary gas diffusion electrode with a three-layer structure. The support body is one or the combination of at least two of a stainless steel net, a titanium net, carbon cloth, a carbon felt and carbon paper.
It should be noted that, the binder adopted in the conventional system roller method must be melted at high temperature and fixed at high pressure to fix the gas-liquid-solid three-phase interface together, and the binder and the gas diffusion layer (hydrophobic porous polymer film) adopted in the embodiment of the present application can be directly adhered together through subsequent phase transformation, so that the method is different from the conventional roller method in that a press device is required to perform high-pressure rolling on the electrode in the preparation process.
And S4, soaking the primary gas diffusion electrode in deionized water to induce phase inversion, and drying to obtain the normal-temperature light-pressure phase inversion gas diffusion electrode.
And (3) placing the primary gas diffusion electrode in deionized water at room temperature for phase conversion for 10-60 min, and then drying to obtain the normal-temperature light-pressure phase conversion gas diffusion electrode.
Unlike suspension such as PTFE, the binder of these suspensions requires high temperature and high pressure to process the electrode and bind it, and the binder of the embodiment of the present application, such as PVDF solution, is a viscous fluid and can be formed by phase inversion after being slightly pressed by a roller, so that the electrode can directly obtain a stable gas-liquid-solid three-phase interface.
The embodiment of the invention also provides an application of the normal-temperature light-pressure conversion gas diffusion electrode prepared by the preparation method as a cathode in preparation of hydrogen peroxide, and the application method comprises the following steps:
(1) An electrolyte solution was added to the gas diffusion electrode as a cathode.
The power supply mode of the electrode is external power supply, the electrolyte solution is selected from any one or the combination of at least two of sodium sulfate, sodium chloride, sodium perchlorate, PBS, sulfuric acid and sodium hydroxide, and the concentration of the electrolyte solution is 10-2000 mM.
(2) At 3-50mA/cm 2 Reacting for 5-480 min under current density to obtain hydrogen peroxide solution.
The following examples further illustrate the invention.
Example 1
A commercial PVDF membrane having a diameter of 3.8cm was immersed in a 100% ethylenediamine solution and subjected to a crosslinking reaction at 80 ℃ for 1min. And after the crosslinking reaction is finished, washing the film by deionized water for 3 times, and then drying the film to obtain the organic solvent-resistant hydrophobic breathable film. To 1mL of a 10% (w/v) PVDF solution, 300mg of activated carbon and 30mg of carbon black were added, and the mixture was thoroughly stirred to form a paste-like mixture. And pouring the pasty mixture on a stainless steel net, covering a PVDF film after the crosslinking reaction, and flattening the mixture by using a rolling shaft to obtain the primary gas diffusion electrode with a three-layer structure. And immersing the primary gas diffusion electrode into deionized water at room temperature for phase conversion for 15min, and then drying at room temperature for 6h to obtain the normal-temperature light-pressure converted gas diffusion electrode.
Comparative example 1
Commercial PVDF membranes having a diameter of 3.8cm were washed 3 times with deionized water and then dried. 300mg of activated carbon and 30mg of carbon black were added to 1mL of 10% (w/v) PVDF solution, and sufficiently stirred to form a paste-like mixture, which was poured onto a stainless steel net, covered with a PVDF film, and the mixture was flattened by a roller to obtain a preliminary electrode having a three-layer structure. The electrode was immersed in deionized water at room temperature for phase inversion for 15min, and then dried at room temperature for 6h to obtain the gas diffusion electrode of comparative example 1.
Example 2
At 50mM Na 2 SO 4 In the solution, the gas diffusion electrode prepared in example 1 was used as a cathode, an external power source was used to supply power to the gas diffusion electrode system, a constant current mode was used, the constant currents were 35, 70, 105, 140, and 175mA, the reaction time was 1H, and H was measured by titanium potassium oxalate spectrophotometry 2 O 2 And (4) concentration.
The experimental results and analyses were as follows:
referring to fig. 1, in fig. 1, a is an SEM characterization result of the PVDF membrane provided in comparative example 1 of the present invention, and B is an SEM characterization result of the PVDF membrane subjected to the crosslinking reaction in example 1 of the present invention, and as can be seen in fig. 1, the surface of the PVDF membrane is in a net shape and has a porous structure, and the surface characteristics of the PVDF membrane after the crosslinking reaction are not significantly changed compared with those before crosslinking, and has a porous surface and a continuous net structure.
Referring to fig. 2, a is an SEM characterization result of the PVDF membrane provided in comparative example 1 of the invention for the resistance to the organic solvent, and B is an SEM characterization result of the PVDF membrane subjected to the crosslinking reaction in example 1 of the invention for the resistance to the organic solvent, it can be seen that the PVDF membrane in comparative example 1 is dissolved by the organic solvent and forms irregular holes, while the PVDF membrane after the crosslinking reaction in example 1 can resist the corrosion of the organic solvent.
Referring to fig. 3, the dotted line is the XPS characterization result of the PVDF film provided in comparative example 1 of the present invention, and the solid line is the XPS characterization result of the PVDF film after the crosslinking reaction provided in example 1 of the present invention, and it can be seen that the nitrogen peak of the PVDF film appears after the crosslinking reaction, and the fluorine peak intensity is reduced, which proves that the PVDF film is successfully crosslinked.
Referring to FIG. 4, the graph of current density-concentration change of hydrogen peroxide generated by the gas diffusion electrode provided in example 2 is shown in the column portion, and the graph of current density-current efficiency change of hydrogen peroxide generated by the gas diffusion electrode provided in example 2 is shown in the broken line portion, and it can be seen from the graph that the current density is 25mA/cm 2 In the case of (3), the amount of hydrogen peroxide produced was 420.4mg/L; at a current density of 15mA/cm 2 In the case of (3), the efficiency of the reaction for oxidizing two electrons to produce hydrogen peroxide was 46.6%. This demonstrates that the gas diffusion electrode can be applied in the field of electrochemical synthesis of hydrogen peroxide.
The beneficial effects of the invention are that compared with the prior art:
(1) The gas diffusion electrode is prepared at normal temperature and under light pressure, the cheap and easily-obtained carbon material is used as the raw material, the preparation process is simple, the operation is easy, the control is convenient, and the large-scale production is facilitated.
(2) The gas diffusion electrode is prepared by a rolling shaft method, the catalyst layer is uniformly distributed, a stable solid-liquid-gas three-phase interface is formed, and the problem of electrode liquid leakage caused by uneven coating of the catalyst by a coating method is solved.
(3) The invention treats the hydrophobic porous gas diffusion layer in advance through a crosslinking reaction, enhances the mechanical strength of the gas diffusion layer and enables the gas diffusion layer to resist organic solvents, so that the gas diffusion electrode can still keep stable in the phase inversion process.
(4) The normal-temperature light-pressure phase-inversion gas diffusion electrode synthesized by the method can generate hydrogen peroxide in situ, no additional reagent is needed, hydrogen peroxide with higher concentration can be generated at lower current density only by active mass transfer of oxygen in the air, the raw materials and the product are environment-friendly, and the reaction cost is reduced.
In summary, in the embodiments of the present invention, on one hand, the electrode composition, such as the materials of the gas diffusion layer and the catalyst layer, is optimized, and on the other hand, the preparation process is improved, and a gas diffusion electrode that is resistant to organic solvents, low in cost, simple and convenient in process, and excellent in performance is developed, so that the capability of efficiently and stably producing hydrogen peroxide can be achieved. The invention synthesizes the normal-temperature light-pressure phase-inversion gas diffusion electrode, and the gas diffusion electrode is used for in-situ hydrogen peroxide generation, so that a high-efficiency and stable electrode material is obtained, and research ideas and theoretical supports are provided for developing electrochemical synthesis with development prospects.
The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are only preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for the purpose of limiting the scope of the present invention, and on the contrary, any modifications or modifications based on the spirit of the present invention should fall within the scope of the present invention.
Claims (10)
1. A preparation method of a gas diffusion electrode capable of realizing phase conversion under normal temperature and light pressure is characterized by comprising the following steps:
the hydrophobic porous polymer film is subjected to crosslinking reaction in the presence of a crosslinking agent to obtain an organic solvent-resistant hydrophobic breathable film;
mixing a binder with a carbon material to obtain a paste mixture;
coating the pasty mixture on a support, then covering the organic solvent-resistant hydrophobic breathable film, and lightly pressing and uniformly rolling by using a rolling shaft to obtain a primary gas diffusion electrode;
and (3) soaking the primary gas diffusion electrode in deionized water to induce phase inversion, and drying to obtain the gas diffusion electrode inverted under normal temperature and light pressure.
2. The method for preparing an atmospheric-temperature light-pressure phase-inversion gas diffusion electrode as claimed in claim 1, wherein the hydrophobic porous polymer membrane is one of a PVDF membrane or a PTFE membrane.
3. The method for preparing the gas diffusion electrode capable of being converted under normal temperature and light pressure as claimed in claim 1, wherein the cross-linking agent is one or more of ethylenediamine, bisphenol, peroxide and mercaptan.
4. The method for preparing a gas diffusion electrode capable of being converted under normal temperature and light pressure as claimed in claim 1, wherein the reaction temperature of the crosslinking reaction is 40-100 ℃ and the reaction time is 5-180 s.
5. The method for preparing the gas diffusion electrode capable of being converted under normal temperature and light pressure as claimed in claim 1, wherein the carbon material comprises activated carbon and carbon black, and the mass ratio of the activated carbon to the carbon black is 1-50: 1.
6. the method for preparing the gas diffusion electrode converted under the normal temperature and the light pressure according to claim 5, wherein the binder is one or more of a PVDF solution, a PSF solution and a PES solution, the concentration of the binder in the binder solution is 5-30% (w/v), and the mass ratio of the activated carbon to the binder is 1-10: 1.
7. the method as claimed in claim 1, wherein the phase inversion time is 10-60 min.
8. The method for preparing the gas diffusion electrode converted under normal temperature and light pressure according to claim 1, wherein the support is one or more of a stainless steel mesh, a titanium mesh, carbon cloth, a carbon felt and carbon paper.
9. The gas diffusion electrode prepared by the preparation method of any one of claim 1 to claim 8.
10. Use of an ambient light pressure phase inversion gas diffusion electrode prepared by the preparation method of any one of claims 1 to 8 as a cathode in the preparation of hydrogen peroxide.
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