CN114361476A - Preparation method and application of gas diffusion electrode - Google Patents
Preparation method and application of gas diffusion electrode Download PDFInfo
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- CN114361476A CN114361476A CN202111487368.1A CN202111487368A CN114361476A CN 114361476 A CN114361476 A CN 114361476A CN 202111487368 A CN202111487368 A CN 202111487368A CN 114361476 A CN114361476 A CN 114361476A
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Abstract
The invention discloses a preparation method of a gas diffusion electrode and application thereof, wherein the preparation method comprises the following steps: s10, coating conductive polymer dispersion liquid on the surface of the current collecting layer raw material to obtain a current collecting layer; s20, coating a hydrophobic breathable layer raw material on one side of the current collecting layer to obtain a hydrophobic breathable layer; s30, coating a catalyst layer raw material on the other side of the current collecting layer to obtain a catalyst layer; s40, carrying out hot pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalyst layer, and then sintering at 200-400 ℃ to obtain the gas diffusion electrode. The conductive polymer is coated on the surface of the raw material of the current collecting layer, and the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalyst layer is subjected to hot pressing treatment, so that the conductive polymer among the catalyst layer, the hydrophobic breathable layer and the current collecting layer is molten and adhered, the interlayer adhesion of the gas diffusion electrode is improved, and the stability of the gas diffusion electrode in a strong corrosive environment and high-current density operation is further enhanced.
Description
Technical Field
The invention relates to the technical field of gas diffusion electrodes, in particular to a preparation method and application of a gas diffusion electrode.
Background
The metal-air battery has the advantages of high energy density, high specific capacity and high use safety, and is a new energy battery with excellent application prospect. The electrochemical oxygen generation/removal technology is a novel technology for transferring oxygen from a cathode end to an anode end of an electrolytic cell through electrochemical reaction, and has wide development space in the industries of food preservation, medical care and the like. In both technologies, the gas diffusion electrode is the core component of the electrolytic cell, and plays a crucial role in promoting the transport of gaseous reactants and providing efficient reactive sites.
Because the electrolytes used in the two technologies are all strong alkaline, the corresponding gas diffusion electrode needs to have good alkali corrosion resistance, so that the electrode can still keep good structural stability in strong alkaline environment and high-current density operation. The current gas diffusion electrode only combines a current collecting layer, a catalyst layer and a waterproof breathable layer through mechanical action, the gas diffusion electrode prepared by the method has poor interlayer adhesion, and the catalyst layer and the hydrophobic breathable layer are easy to peel off or even fall off under a strong corrosive environment and high-current density operation for a long time.
Disclosure of Invention
The invention mainly aims to provide a preparation method of a gas diffusion electrode and application thereof, and aims to solve the problem of poor structural stability of the conventional gas diffusion electrode.
In order to achieve the above object, the present invention provides a method for manufacturing a gas diffusion electrode, comprising the steps of:
s10, coating conductive polymer dispersion liquid on the surface of the current collecting layer raw material, and drying to obtain a current collecting layer;
s20, coating a hydrophobic and breathable layer raw material on one side of the current collecting layer, and drying to obtain a hydrophobic and breathable layer;
s30, coating a catalyst layer raw material on the other side of the flow collecting layer, and drying to obtain a catalyst layer;
s40, carrying out hot pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer at 100-150 ℃, and then sintering at 200-400 ℃ for 1-3 h to obtain the gas diffusion electrode.
Alternatively, in step S10:
the material of the current collecting layer is a metal wire mesh or foam metal; and/or the presence of a gas in the gas,
the conductive polymer in the conductive polymer dispersion liquid comprises at least one of polyaniline, polypyrrole and polyacetylene; and/or the presence of a gas in the gas,
the mass of the conductive polymer loaded on the current collecting layer is 1-2.5 mg/cm2。
Optionally, before step S20, the method further includes the following steps:
crushing and sieving a carbon material, and uniformly mixing the carbon material with a solvent to obtain a mixed solution;
pulping the mixed solution to obtain carbon material slurry with the particle size of less than 15 micrometers;
adding a hydrophobic polymer and a pore-forming agent into the carbon material slurry, and pulping for 2-5 h at 12000-20000 rpm to obtain slurry with the particle size of less than 15 microns;
and baking the slurry at 50-90 ℃ to form paste, thereby obtaining the hydrophobic breathable layer raw material.
Optionally, the carbon material comprises at least one of conductive carbon black, carbon nanotubes, and acetylene black; and/or the presence of a gas in the gas,
the solvent comprises at least one of water, absolute ethyl alcohol, n-propanol and isopropanol; and/or the presence of a gas in the gas,
the hydrophobic polymer comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; and/or the presence of a gas in the gas,
the pore-forming agent comprises at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate.
Optionally, the mass of the hydrophobic polymer is 40-80% of the mass of the carbon material; and/or the presence of a gas in the gas,
the mass of the pore-forming agent is 10-20% of the mass of the carbon material.
Optionally, before step S30, the method further includes the following steps:
crushing and sieving a catalyst and a carbon material, and uniformly mixing the catalyst and the carbon material with a solvent to obtain a first solution;
pulping the first solution to obtain mixed slurry with the particle size of less than 15 mu m;
adding a hydrophobic polymer and a pore-forming agent into the mixed slurry, and pulping for 2-5 hours at 12000-2000 rpm to obtain a catalyst layer slurry with the particle size of less than 15 microns;
and baking the catalyst layer slurry at 50-90 ℃ to form paste, thereby obtaining the catalyst layer raw material.
Optionally, the catalyst comprises a manganese dioxide catalyst; and/or the presence of a gas in the gas,
the carbon material includes at least one of conductive carbon black, carbon nanotubes, and acetylene black; and/or the presence of a gas in the gas,
the solvent comprises at least one of water, absolute ethyl alcohol, n-propanol and isopropanol; and/or the presence of a gas in the gas,
the hydrophobic polymer comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; and/or the presence of a gas in the gas,
the pore-forming agent comprises at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate; and/or the presence of a gas in the gas,
the mass ratio of the catalyst to the carbon material is 1.5-5: 1; and/or the presence of a gas in the gas,
the mass of the hydrophobic polymer is 20-40% of the total mass of the carbon material and the catalyst; and/or the presence of a gas in the gas,
the mass of the pore-forming agent is 10-20% of the total mass of the carbon material and the catalyst.
Alternatively, in step S40:
in the hot pressing treatment, the hot pressing pressure is 1.5-5 MPa, and the hot pressing time is 5-10 min.
Furthermore, the invention also provides a metal-air battery, which comprises the gas diffusion electrode, wherein the gas diffusion electrode is prepared by the preparation method of the gas diffusion electrode.
The invention also provides an electrochemical oxygen production method, which takes water and carbon dioxide as reaction raw materials and produces O by electrolysis on the anode2While CO is present2Electrochemical reaction is carried out under the action of a cathode catalyst,
wherein the cathode is a gas diffusion electrode, and the gas diffusion electrode is prepared by the preparation method of the gas diffusion electrode.
According to the technical scheme provided by the invention, a conductive polymer is coated on the surface of a raw material of the current collecting layer to obtain the current collecting layer, then the catalyst layer and the hydrophobic breathable layer are respectively arranged on two sides of the current collecting layer, and finally the composite layer material (namely the preliminarily formed gas diffusion electrode) consisting of the hydrophobic breathable layer, the current collecting layer and the catalyst layer is subjected to hot pressing treatment, so that the conductive polymer among the catalyst layer, the hydrophobic breathable layer and the current collecting layer is fused and adhered, thus the interlayer adhesion degree of the prepared gas diffusion electrode is improved, and the structural stability of the gas diffusion electrode in a strong corrosive environment and during high-current density operation is further enhanced.
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 scanning electron micrograph of a hydrophobic gas permeable layer of a gas diffusion electrode prepared according to example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of a cross section of a gas diffusion electrode obtained in example 1 of the present invention;
FIG. 3 is a graph of voltage versus current density for electrochemical oxygen production/removal for examples 1-4 of the present invention and comparative example 1;
FIG. 4 is a graph showing stability tests in electrochemical oxygen production/removal for example 1 of the present invention and comparative example 1.
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 electrolytes used in the metal-air battery and the electrochemical oxygen generation/removal technology are both strong alkaline, the corresponding gas diffusion electrode needs to have good alkali corrosion resistance, so that the electrode can still keep good structural stability when working at high current density in a strong alkaline environment. The current gas diffusion electrode only combines a current collecting layer, a catalyst layer and a waterproof breathable layer through mechanical action, the gas diffusion electrode prepared by the method has poor interlayer adhesion, and the catalyst layer and the hydrophobic breathable layer are easy to peel off or even fall off when the gas diffusion electrode runs at high current density in a long-term strong corrosive environment.
In view of this, the present invention provides a method for preparing a gas diffusion electrode, which aims to provide a gas diffusion electrode with good structural stability, so that the gas diffusion electrode has a long service life when being applied to metal-air batteries and electrochemical oxygen generation technologies. In one embodiment, the method for preparing the gas diffusion electrode comprises the following steps:
and step S10, coating the conductive polymer dispersion liquid on the surface of the current collecting layer raw material, and drying to obtain the current collecting layer.
The current collecting layer is used for conducting current generated in the electrochemical reaction process and supporting the whole gas diffusion electrode, and in this embodiment, the current collecting layer is made of a metal wire mesh or a metal foam. Preferably, the current collecting layer is made of a nickel wire mesh or foam metal, so that the prepared current collecting layer has a good supporting effect and is corrosion-resistant. Preferably, the material of the flow collecting layer is a nickel wire mesh with the mesh number of 20-50.
In order to make the adhesion between the current collecting layer and the catalytic layer and between the current collecting layer and the hydrophobic air-permeable layer good, in this embodiment, the raw material of the current collecting layer is pretreated. Specifically, the pretreatment step includes: carrying out ultrasonic treatment on the current collecting layer raw material in acetone for 10-30 min, carrying out ultrasonic treatment in 1mol/L (mol/L is abbreviated as M) hydrochloric acid for 30s, and finally washing with deionized water. Wherein, the ultrasonic treatment in acetone is used for removing dust and oil stains on the surface of the current collecting layer raw material. The ultrasonic treatment in hydrochloric acid is to remove the oxide layer on the surface of the current collecting layer raw material and increase the surface roughness of the current collecting layer raw material.
In the present embodiment, the conductive polymer in the conductive polymer dispersion includes at least one of polyaniline, polypyrrole, and polyacetylene, that is, the conductive polymer may be polyaniline, polypyrrole, polyethylene, a mixture of polypyrrole and polyacetylene, a mixture of polyaniline and polyacetylene, or the like. In a preferred embodiment, the conductive polymer is polyaniline, so that the prepared gas diffusion electrode has better stability and corrosion resistance. The invention does not limit the addition amount of the conductive polymer dispersion liquid, as long as the mass of the conductive polymer loaded on the finally prepared current collecting layer is 1-2.5 mg/cm2And (4) finishing.
And step S20, coating a hydrophobic breathable layer raw material on one side of the current collecting layer, and drying to obtain the hydrophobic breathable layer.
And step S30, coating a catalyst layer raw material on the other side of the flow collecting layer, and drying to obtain the catalyst layer.
It should be noted that the present invention does not limit the sequence between step S20 and step S30, and the operation of step S20 may be performed first, or step S30 may be performed first.
And S40, carrying out hot pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer at 100-150 ℃, and then sintering at 200-400 ℃ for 1-3 h to obtain the gas diffusion electrode.
In the embodiment, in the hot-pressing treatment, the hot-pressing pressure is 1.5 to 5MPa, the hot-pressing time is 5 to 10min, and under the hot-pressing condition, the adhesion among the catalyst layer, the hydrophobic breathable layer and the current collecting layer is good.
In addition, in the embodiment, the thickness of the finally prepared gas diffusion electrode after sintering is 0.3-0.6 mm. In another embodiment, in the finally prepared gas diffusion electrode, the thickness of the hydrophobic breathable layer is 0.2-0.3 mm. In another embodiment, in the finally prepared gas diffusion electrode, the thickness of the catalytic layer is 0.05-0.15 mm.
In step S10, step S20, and step S30, the temperature of the drying is 50 to 90 ℃. It is understood that, in the above steps, the drying temperatures are selected independently, and may be the same or different. For ease of operation, the same is preferred.
According to the technical scheme provided by the invention, a conductive polymer is coated on the surface of a raw material of the current collecting layer to obtain the current collecting layer, then the catalyst layer and the hydrophobic breathable layer are respectively arranged on two sides of the current collecting layer, and finally the composite layer material (namely the preliminarily formed gas diffusion electrode) consisting of the hydrophobic breathable layer, the current collecting layer and the catalyst layer is subjected to hot pressing treatment, so that the conductive polymer among the catalyst layer, the hydrophobic breathable layer and the current collecting layer is fused and adhered, thus the interlayer adhesion degree of the prepared gas diffusion electrode is improved, and the structural stability of the gas diffusion electrode in a strong corrosive environment and during high-current density operation is further enhanced.
In the gas diffusion electrode, the hydrophobic breathable layer plays roles of oxygen diffusion, oxygen reduction, electrolyte leakage prevention and the like, and taking the gas diffusion electrode as an example when applied to a metal-air battery, when the humidity of air is higher than the equilibrium humidity of electrolyte, moisture diffuses from air to the electrolyte side, so that the electrolyte is diluted, the volume is increased, and the battery shell is gradually burst, so that the electrolyte leakage is caused; when the air humidity is lower than the equilibrium humidity of the electrolyte, the moisture diffuses from the electrolyte to the air side, so that the moisture of the electrolyte is lost and gradually dried, and the metal-air battery is disabled. In addition, the strongly basic electrolyte absorbs carbon dioxide in the air to cause carbonation, and crystalline particles of carbonate or bicarbonate formed therein easily block the micropores of the gas diffusion electrode, thereby shortening the service life of the gas diffusion electrode. In order to solve the above problems, methods of reducing the pore diameter of the microporous channel in the hydrophobic gas-permeable layer and increasing the thickness of the hydrophobic gas-permeable layer are mainly used at present, but these methods may negatively affect the gas transport of the gas diffusion electrode, thereby reducing the battery performance; meanwhile, the microporous pore channels are more easily blocked by the carbonic acid crystallization caused by the carbon dioxide, so that the service life of the gas diffusion electrode is further shortened.
In view of the above, the invention also provides a preparation method of the hydrophobic breathable layer raw material and the catalyst layer raw material, by selecting the materials in the hydrophobic breathable layer raw material and the catalyst layer raw material, proportioning the materials and designing the preparation process, the pore diameter and distribution of micropores of the hydrophobic breathable layer are optimized, and the number of the interconnected pores is increased, so that on the premise of ensuring the electrolyte permeation prevention capability of the gas diffusion electrode, the gas transmission performance of the gas diffusion electrode is further improved, and the negative influence of the carbonation problem caused by carbon dioxide on the service life of the gas diffusion electrode is effectively alleviated.
Therefore, in the present embodiment, before step S20, the following steps are further included:
and step A1, crushing and sieving the carbon material, and uniformly mixing the crushed carbon material with the solvent to obtain a mixed solution.
And (2) crushing the carbon material, sieving the crushed carbon material with a 1000-6000-mesh sieve, mixing the crushed carbon material with a solvent, and carrying out ultrasonic oscillation for 30-60 min to fully mix the crushed carbon material and the solvent uniformly to obtain a mixed solution.
The carbon material includes at least one of conductive carbon black, carbon nanotubes and acetylene black, that is, the carbon material may be conductive carbon black, carbon nanotubes, acetylene black, a mixture of conductive carbon black and carbon nanotubes, or the like. Further, the conductive carbon Black is specifically Vulcan XC-72, BP-2000 or Ketjen-Black. The solvent includes at least one of water, absolute ethanol, n-propanol, and isopropanol.
And A2, pulping the mixed solution to obtain carbon material slurry with the particle size of less than 15 mu m.
And (3) pulping the mixed solution by using a high-speed shearing machine, and pulping for 30-60 min at 8000-12000 rpm until a uniform paste is formed, wherein the particle size of solid particles in the paste is less than 15 mu m, so that the carbon material slurry is obtained.
And A3, adding a hydrophobic polymer and a pore-forming agent into the carbon material slurry, and pulping for 2-5 h at 12000-2000 rpm to obtain the slurry with the particle size of less than 15 microns.
In order to achieve better beating shear and mixing, in a preferred embodiment, step a3 includes: and (3) dropwise adding the hydrophobic polymer and the pore-forming agent into the carbon material slurry under the condition of pulping at 8000-12000 rpm, and continuously alternatively pulping for 2-5 hours at 12000, 16000 and 20000rpm to obtain the slurry with the particle size of less than 15 microns.
Wherein the hydrophobic polymer comprises at least one of Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), Polytrifluoroethylene (PTFS), and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA). Preferably, the hydrophobic polymer is polytetrafluoroethylene. It will be appreciated that to facilitate dispersion of the hydrophobic polymer, a hydrophobic polymer dispersion is added.
The pore-forming agent comprises at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate. In order to facilitate the dispersion of the pore-forming agent in the carbon material slurry, the pore-forming agent is preferably crushed, sieved by a 1000-3000-mesh sieve, dispersed in a solvent incapable of dissolving the pore-forming agent to form a uniform dispersion liquid, and then added into the carbon material slurry.
It can be understood that, according to different use types of the hydrophobic polymer, the pore-forming agent and the carbon material, the addition amounts thereof are different correspondingly, and the specific addition amounts of the hydrophobic polymer, the pore-forming agent and the carbon material are not limited in the present invention, and in this embodiment, the mass of the hydrophobic polymer is 40-80% of the mass of the carbon material; and/or the mass of the pore-forming agent is 10-20% of the mass of the carbon material.
And A4, baking the slurry at 50-90 ℃ to form a paste, and obtaining the hydrophobic breathable layer raw material.
In this embodiment, before step S30, the method further includes the following steps:
and step B1, crushing and sieving the catalyst and the carbon material, and uniformly mixing the crushed catalyst and the carbon material with the solvent to obtain a first solution.
In this example, the catalyst comprises manganese dioxide catalyst. The carbon material includes at least one of conductive carbon black, carbon nanotubes, and acetylene black. Specifically, the conductive carbon Black is Vulcan XC-72, BP-2000 or Ketjen-Black. Further, the mass ratio of the catalyst to the carbon material is 1.5 to 5: 1. wherein the solvent comprises at least one of water, absolute ethyl alcohol, n-propanol and isopropanol.
And step B2, pulping the first solution to obtain mixed slurry with the particle size of less than 15 mu m.
And (3) pulping the first solution by using a high-speed shearing machine, and pulping for 30-60 min at 8000-12000 rpm until a uniform paste is formed, wherein the particle size of solid particles in the paste is less than 15 mu m, so that the mixed slurry is obtained.
And step B3, adding a hydrophobic polymer and a pore-forming agent into the mixed slurry, and pulping for 2-5 hours at 12000-2000 rpm to obtain the catalytic layer slurry with the particle size of less than 15 microns.
Specifically, the hydrophobic polymer and the pore-forming agent are added into the mixed slurry drop by drop under the condition of beating at 8000-12000 rpm, and beating is continued for 2-5 hours alternately at the rotating speeds of 12000, 16000 and 20000rpm, so as to obtain the catalytic layer slurry with the particle size of less than 15 microns. Wherein the hydrophobic polymer comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; and/or the pore-forming agent comprises at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate.
In the embodiment, the mass of the hydrophobic polymer is 20-40% of the total mass of the carbon material and the catalyst. In another embodiment, the mass of the pore-forming agent is 10-20% of the total mass of the carbon material and the catalyst.
It should be noted that, when the conductive polymer in step S10 is polyaniline, the hydrophobic polymer in step A3 and step B3 is Polytetrafluoroethylene (PTFE), and the sintering temperature of the composite layer material is 340-400 ℃, the stability and corrosion resistance of the prepared gas diffusion electrode are better. The selection of the specific materials of the carbon material, the solvent, the hydrophobic polymer and the pore-forming agent in steps a1 and A3 and steps B1 and B3 are independent of each other, may be the same or different, and are preferably the same for convenience of operation.
And step B4, baking the catalyst layer slurry to paste at 50-90 ℃ to obtain the catalyst layer raw material.
An example of the method for producing a gas diffusion electrode according to the present invention is given below:
(1) crushing a carbon material (at least one of conductive carbon black, carbon nano tubes and acetylene black), sieving the crushed carbon material with a 1000-6000-mesh sieve, mixing the crushed carbon material with a solvent (at least one of water, absolute ethyl alcohol, n-propyl alcohol and isopropyl alcohol), carrying out ultrasonic oscillation for 30-60 min to fully mix the mixture to obtain a mixed solution, carrying out pulping treatment on the mixed solution by using a high-speed shearing machine, pulping for 30-60 min at 8000-12000 rpm to obtain carbon material slurry with the particle size of less than 15 mu m, adding a hydrophobic polymer (at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyfluortetraethylene and tetrafluoroethylene-perfluoroalkylvinylether copolymer) and a pore-forming agent (at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate) into the carbon material slurry (wherein the mass of the hydrophobic polymer is 40-80% of the mass of the carbon material) dropwise under the condition of pulping at 8000-12000 rpm, the mass of the pore-forming agent is 10-20% of that of the carbon material), continuously and alternately pulping for 2-5 h at the rotating speeds of 12000, 16000 and 20000rpm to obtain slurry with the particle size of less than 15 mu m, and baking the slurry to paste at 50-90 ℃ to obtain the hydrophobic breathable layer raw material.
(2) Crushing and sieving a catalyst (manganese dioxide catalyst), a carbon material (at least one of conductive carbon black, carbon nano tubes and acetylene black), uniformly mixing the crushed and sieved carbon material with a solvent (at least one of water, absolute ethyl alcohol, n-propanol and isopropanol) to obtain a first solution (wherein the mass ratio of the catalyst to the carbon material is 1.5-5: 1), pulping the first solution by using a high-speed shearing machine, pulping at 8000-12000 rpm for 30-60 min to obtain a mixed slurry with the particle size of less than 15 mu m, dropwise adding a hydrophobic polymer (at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyfluortetraethylene and tetrafluoroethylene-perfluoroalkylvinylether copolymer) and a pore-forming agent (at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate) into the mixed slurry under the condition of pulping at 8000-12000 rpm, and continuously pulping for 2-5 h alternately at the rotating speeds of 12000, 16000 and 20000rpm to obtain catalyst layer slurry with the particle size of less than 15 microns (wherein the mass of the hydrophobic polymer is 20-40% of the total mass of the carbon material and the catalyst, and the mass of the pore-forming agent is 10-20% of the total mass of the carbon material and the catalyst), and baking the catalyst layer slurry to paste at the temperature of 50-90 ℃ to obtain the catalyst layer raw material.
(3) Carrying out ultrasonic treatment on a current collecting layer raw material (a metal wire mesh or foam metal) in acetone for 10-30 min, carrying out ultrasonic treatment in 1mol/L hydrochloric acid for 30s, finally washing the current collecting layer raw material with deionized water, soaking the washed current collecting layer raw material in a conductive polymer dispersion liquid (conductive polymer comprises at least one of polyaniline, polypyrrole and polyacetylene), and drying the current collecting layer raw material at 50-90 ℃ to obtain a current collecting layer (the mass of the conductive polymer loaded on the current collecting layer is 1-2.5 mg/cm)2)。
(4) And coating a hydrophobic breathable layer raw material on one side of the current collecting layer, and drying at 50-90 ℃ to obtain the hydrophobic breathable layer.
(5) Coating a catalyst layer raw material on the other side of the flow collecting layer, and drying at 50-90 ℃ to obtain the catalyst layer.
(6) And carrying out hot-pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalyst layer for 5-10 min at 100-150 ℃ and 1.5-5 MPa, and then sintering at 200-400 ℃ for 1-3 h to obtain the gas diffusion electrode with the thickness of 0.3-0.6 mm, wherein the thickness of the hydrophobic breathable layer is 0.2-0.3 mm, and the thickness of the catalyst layer is 0.05-0.15 mm.
Further, the invention also provides a metal-air battery, which comprises a gas diffusion electrode, wherein the gas diffusion electrode is prepared by the preparation method of the gas diffusion electrode. The gas diffusion electrode has good structural stability in a strong corrosive environment and during high-current density operation, good electrolyte permeability and gas transmission resistance, and can effectively reduce the negative influence of carbonation caused by carbon dioxide on the service life of the gas diffusion electrode, so that the metal air battery prepared from the gas diffusion electrode has long service life and good battery performance.
In addition, the invention also provides an electrochemical oxygen production method, which takes water and carbon dioxide as reaction raw materials and produces O by electrolysis on an anode2While CO is present2The electrochemical reaction is carried out under the action of a cathode catalyst, wherein the cathode is a gas diffusion electrode, and the gas diffusion electrode is prepared by the preparation method of the gas diffusion electrode. The gas diffusion electrode has good structural stability in a strong corrosive environment and during high-current density operation, good electrolyte permeability and gas transmission resistance, and can effectively reduce the negative influence of carbonation problem caused by carbon dioxide on the service life of the gas diffusion electrode, so that the gas diffusion electrode has long service life and better performance when being used as a cathode for electrochemical oxygen generation.
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.
Example 1
(1) 4.8g of acetylene black and 8g of Vulcan XC-72 are ground and crushed and then sieved by a sieve of 1000 to 3000 meshes, then mixing the mixed solution with 400mL of isopropanol, carrying out ultrasonic oscillation for 60min to fully and uniformly mix the mixed solution to obtain a mixed solution, carrying out pulping treatment on the mixed solution by using a high-speed shearing machine, pulping at 12000rpm for 45min to obtain carbon material slurry with particle diameter less than 15 μm, adding 25g of 30 wt% polytetrafluoroethylene dispersion and 12.5g of 20 wt% ammonium oxalate ethanol dispersion into the carbon material slurry (i.e. the mass of the hydrophobic polymer is 58.6% of the mass of the carbon material, and the mass of the pore-forming agent is 19.5% of the mass of the carbon material) dropwise under the condition of pulping at 12000rpm, and continuously beating for 2.5h alternately at the rotating speeds of 12000, 16000 and 20000rpm to obtain pulp with the particle size of less than 15 μm, and baking the pulp at 90 ℃ to obtain a paste to obtain the hydrophobic breathable layer raw material.
(2) Crushing 10g of manganese dioxide catalyst, 1.2g of acetylene black and 2g of Vulcan XC-72, sieving the crushed materials with a sieve of 1000-3000, uniformly mixing the crushed materials with 400mL of isopropanol to obtain a first solution (namely, the mass ratio of the catalyst to the carbon material is 3.125: 1), pulping the first solution by using a high-speed shearing machine for 45min at 12000rpm to obtain a mixed slurry with the particle size of less than 15 mu m, dropwise adding 16g of 30 wt% polytetrafluoroethylene dispersion and 12.5g of 20 wt% ammonium oxalate ethanol dispersion into the mixed slurry under the condition of pulping at 12000rpm, and continuously and alternately pulping for 4h at 12000, 16000 and 20000rpm to obtain a slurry with the particle size of less than 15 mu m (namely, the mass of the hydrophobic polymer is 36% of the total mass of the carbon material and the catalyst, and the mass of the pore-forming agent is 18.9% of the total mass of the carbon material and the catalyst), and baking the catalyst layer slurry at 90 ℃ to form paste to obtain the catalyst layer raw material.
(3) Cutting a 20-mesh nickel screen to a size of 10cm multiplied by 10cm, carrying out ultrasonic treatment in acetone for 20min, carrying out ultrasonic treatment in 1mol/L hydrochloric acid for 30s, finally washing the cleaned current collecting layer by deionized water, soaking the washed current collecting layer raw material in a polyaniline solution, and drying the polyaniline solution at 80 ℃ to obtain a current collecting layer (the mass of a conductive polymer loaded on the current collecting layer is 1.3 mg/cm)2)。
(4) And coating a hydrophobic breathable layer raw material on one side of the current collecting layer, and drying at 60 ℃ to obtain the hydrophobic breathable layer.
(5) And coating a catalyst layer raw material on the other side of the flow collecting layer, and drying at 60 ℃ to obtain the catalyst layer.
(6) And carrying out hot-pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer for 10min at 150 ℃ and 3MPa, and then sintering the composite layer material for 2h at 350 ℃ to obtain the gas diffusion electrode with the thickness of 0.4mm, wherein the thickness of the hydrophobic breathable layer is 0.27mm, and the thickness of the catalytic layer is 0.05 mm.
Example 2
(1) 4.5g of carbon nano tube and 7.5g of BP-2000 are ground and crushed and then sieved by a 3000-6000 mesh sieve, then mixing the mixed solution with 400mL of absolute ethyl alcohol, carrying out ultrasonic oscillation for 30min to fully and uniformly mix the mixed solution to obtain a mixed solution, carrying out pulping treatment on the mixed solution by using a high-speed shearing machine, pulping at 8000rpm for 60min to obtain carbon material slurry with particle diameter less than 15 μm, adding 40g 12 wt% polyvinylidene fluoride dispersion and 12g 10 wt% ammonium bicarbonate ethanol dispersion into carbon material slurry (i.e. hydrophobic polymer 40% by mass and pore-forming agent 10% by mass) dropwise under the condition of pulping at 8000rpm, and continuously beating for 5 hours alternately at the rotating speeds of 12000, 16000 and 20000rpm to obtain pulp with the particle size of less than 15 μm, and baking the pulp at 50 ℃ to obtain a paste to obtain the hydrophobic and breathable layer raw material.
(2) Crushing 9g of manganese dioxide catalyst, 1.5g of acetylene black and 4.5g of BP-2000, sieving the crushed materials with a 1000-3000 sieve, uniformly mixing the crushed materials with 400mL of absolute ethyl alcohol to obtain a first solution (namely, the mass ratio of the catalyst to the carbon material is 1.5: 1), pulping the first solution by using a high-speed shearing machine, pulping the first solution at 800rpm for 45min to obtain a mixed slurry with the particle size of less than 15 mu m, dropwise adding 15g of 40 wt% polyvinylidene fluoride dispersion liquid and 15g of 50 wt% ammonium bicarbonate ethanol dispersion liquid into the mixed slurry under the condition of pulping at 8000rpm, and continuously and alternately pulping at 12000, 16000 and 20000rpm for 5h to obtain a catalytic layer slurry with the particle size of less than 15 mu m (namely, the mass of a hydrophobic polymer is 40% of the total mass of the carbon material and the catalyst, and the mass of the pore-forming agent is 20,20% of the total mass of the carbon material and the catalyst), and baking the catalyst layer slurry at 50 ℃ to obtain paste, thus obtaining the catalyst layer raw material.
(3) Cutting 30 mesh steel wire mesh to 10cm × 10cm, ultrasonic treating in acetone for 20min, ultrasonic treating in 1mol/L hydrochloric acid for 30s, and washing with deionized waterCleaning, soaking the cleaned current collecting layer raw material in polyaniline solution, and drying at 90 deg.C to obtain current collecting layer (the mass of conductive polymer loaded on the current collecting layer is 1 mg/cm)2)。
(4) And coating a hydrophobic breathable layer raw material on one side of the current collecting layer, and drying at 90 ℃ to obtain the hydrophobic breathable layer.
(5) Coating a catalyst layer raw material on the other side of the flow collecting layer, and drying at 90 ℃ to obtain the catalyst layer.
(6) And carrying out hot-pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer for 5min at 100 ℃ and 5MPa, and then sintering for 3h at 200 ℃ to obtain the gas diffusion electrode with the thickness of 0.3mm, wherein the thickness of the hydrophobic breathable layer is 0.2mm, and the thickness of the catalytic layer is 0.06 mm.
Example 3
(1) 4g of carbon nano tube and 8g of acetylene black are ground and crushed and then sieved by a sieve of 1000-3000 meshes, then mixing the mixed solution with 400mL of n-propanol, carrying out ultrasonic oscillation for 50min to fully and uniformly mix the mixed solution to obtain a mixed solution, carrying out pulping treatment on the mixed solution by using a high-speed shearing machine, pulping at 10000rpm for 30min to obtain carbon material slurry with the particle size of less than 15 μm, dropwise adding 20g of 48 wt% polytrifluorostyrene dispersion liquid and 12g of 20 wt% sodium sulfate ethanol dispersion liquid into the carbon material slurry (namely, the mass of the hydrophobic polymer is 80% of the mass of the carbon material, and the mass of the pore-forming agent is 20% of the mass of the carbon material) under the condition of pulping at 10000rpm, and continuously beating for 2h alternately according to the rotating speeds of 12000, 16000 and 20000rpm to obtain pulp with the particle size of less than 15 μm, and baking the pulp at 60 ℃ to obtain a paste to obtain the hydrophobic and breathable layer raw material.
(2) Crushing 10g of manganese dioxide catalyst, 1g of carbon nanotube and 1g of acetylene black, sieving the crushed materials with a 1000-3000 sieve, uniformly mixing the crushed materials with 400mL of n-propanol to obtain a first solution (namely, the mass ratio of the catalyst to the carbon material is 5: 1), pulping the first solution by using a high-speed shearing machine, pulping the first solution at 10000rpm for 45min to obtain a mixed slurry with the particle size of less than 15 mu m, gradually adding 12g of 20 wt% polytrifluoroethylene dispersion and 12g of 10 wt% sodium sulfate ethanol dispersion into the mixed slurry under the condition of pulping at 10000rpm, and continuously and alternately pulping at 12000, 16000 and 20000rpm for 2h to obtain a catalytic layer slurry with the particle size of less than 15 mu m (namely, the mass of the hydrophobic polymer is 20% of the total mass of the carbon material and the catalyst, and the mass of the pore-forming agent is 10% of the total mass of the carbon material and the catalyst), and baking the catalyst layer slurry at 70 ℃ to form paste to obtain the catalyst layer raw material.
(3) Cutting nickel foam metal to 10cm multiplied by 10cm, carrying out ultrasonic treatment in acetone for 20min, carrying out ultrasonic treatment in 1mol/L hydrochloric acid for 30s, finally washing with deionized water, soaking the washed current collecting layer raw material in polyaniline solution, and drying at 50 ℃ to obtain a current collecting layer (the mass of the conductive polymer loaded on the current collecting layer is 2.5 mg/cm)2)。
(4) And coating a hydrophobic breathable layer raw material on one side of the current collecting layer, and drying at 50 ℃ to obtain the hydrophobic breathable layer.
(5) Coating the other side of the flow collection layer with a catalyst layer raw material, and drying at 50 ℃ to obtain the catalyst layer.
(6) And carrying out hot-pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer for 7min at the temperature of 120 ℃ and under the pressure of 1.5MPa, and then sintering the composite layer material for 1h at the temperature of 400 ℃ to obtain the gas diffusion electrode with the thickness of 0.6mm, wherein the thickness of the hydrophobic breathable layer is 0.3mm, and the thickness of the catalytic layer is 0.15 mm.
Example 4
(1) Cutting a 20-mesh nickel screen to a size of 10cm multiplied by 10cm, carrying out ultrasonic treatment in acetone for 20min, carrying out ultrasonic treatment in 1mol/L hydrochloric acid for 30s, finally washing the cleaned current collecting layer by deionized water, soaking the washed current collecting layer raw material in a polyaniline solution, and drying the polyaniline solution at 80 ℃ to obtain a current collecting layer (the mass of a conductive polymer loaded on the current collecting layer is 1.3 mg/cm)2)。
(2) And coating a hydrophobic and breathable layer raw material (a mixture of a carbon material, a hydrophobic polymer, isopropanol and a pore-forming agent) on one side of the current collecting layer, and drying at 60 ℃ to obtain the hydrophobic and breathable layer.
(3) And coating the other side of the current collection layer with a catalyst layer raw material (a mixture of a catalyst, a carbon material, a hydrophobic polymer, isopropanol and a pore-forming agent), and drying at 60 ℃ to obtain the catalyst layer.
(4) And carrying out hot-pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer for 10min at 150 ℃ and 3MPa, and then sintering the composite layer material for 2h at 350 ℃ to obtain the gas diffusion electrode with the thickness of 0.4mm, wherein the thickness of the hydrophobic breathable layer is 0.3mm, and the thickness of the catalytic layer is 0.1 mm.
Comparative example 1
The same procedure as in example 1 was followed except that the step (3) was replaced with a 20 mesh nickel mesh screen cut to a size of 10cm × 10cm, then sonicated in acetone for 20min, then sonicated in 1mol/L hydrochloric acid for 30s, finally rinsed with deionized water, and then dried at 80 ℃ to obtain a current collecting layer (i.e., the surface of the current collecting layer was not coated with a conductive polymer).
FIG. 1 is a scanning electron micrograph of a hydrophobic gas permeable layer of a gas diffusion electrode prepared according to example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of a cross section of a gas diffusion electrode prepared in example 1 of the present invention. As can be seen from fig. 1 and 2, the gas diffusion electrode prepared by the preparation method of the present invention has a large number of micropores on the surface, and the hydrophobic binder existing in the pores is distributed among the carbon material particles in a filamentous manner, so that the mechanical strength and the hydrophobicity of the surface of the hydrophobic gas permeable layer of the gas diffusion electrode are well maintained.
FIG. 3 is a graph of voltage versus current density for electrochemical oxygen production/removal for examples 1-4 of the present invention and comparative example 1. As can be seen from FIG. 3, the gas diffusion electrode prepared by the preparation method of the invention has excellent performance in electrochemical oxygen generation/deoxidization, and the reaction current density can reach 300mA cm at a voltage of 1.2V-2. Comparing examples 1-3 with example 4 shows that the gas diffusion electrode prepared by the gas diffusion layer and catalytic layer manufacturing process according to the present invention has a larger current density in the actual electrochemical oxygen generation/removal test, and that the gas diffusion electrode prepared according to the present invention has a more excellent hydrophobic air permeability, which can ensure electrochemical oxygen generation/removalThe reaction gas is fully contacted with the interface of the catalytic layer in the process. By comparing example 1 with comparative example 1, it is shown that the addition of the conductive polymer also improves the performance of the conductive polymer in the electrochemical oxygen generation/removal process, and the increase amplitude of the current density is correspondingly increased along with the increase of the voltage.
Fig. 4 is a stability test chart of electrochemical oxygen generation/removal of example 1 and comparative example 1 of the present invention, and it can be seen from fig. 4 that the current densities of the gas diffusion electrodes manufactured according to the methods of example 1 and comparative example 1 are attenuated to some extent in the constant voltage long-time electrochemical oxygen generation/removal test at a voltage of 1.2V, wherein the performance attenuation of the gas diffusion electrode in example 1 is only 7% in the 500h continuous test, while the attenuation of the gas diffusion electrode in comparative example 1 reaches 15%, which illustrates that the stability of the gas diffusion electrode is significantly improved by the treatment process of coating the conductive polymer on the surface of the current collecting layer.
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. A method for preparing a gas diffusion electrode, comprising the steps of:
s10, coating conductive polymer dispersion liquid on the surface of the current collecting layer raw material, and drying to obtain a current collecting layer;
s20, coating a hydrophobic and breathable layer raw material on one side of the current collecting layer, and drying to obtain a hydrophobic and breathable layer;
s30, coating a catalyst layer raw material on the other side of the flow collecting layer, and drying to obtain a catalyst layer;
s40, carrying out hot pressing treatment on the composite layer material consisting of the hydrophobic breathable layer, the current collecting layer and the catalytic layer at 100-150 ℃, and then sintering at 200-400 ℃ for 1-3 h to obtain the gas diffusion electrode.
2. The method for producing a gas diffusion electrode according to claim 1, wherein in step S10:
the material of the current collecting layer is a metal wire mesh or foam metal; and/or the presence of a gas in the gas,
the conductive polymer in the conductive polymer dispersion liquid comprises at least one of polyaniline, polypyrrole and polyacetylene; and/or the presence of a gas in the gas,
the mass of the conductive polymer loaded on the current collecting layer is 1-2.5 mg/cm2。
3. The method of manufacturing a gas diffusion electrode according to claim 1, further comprising, before step S20, the steps of:
crushing and sieving a carbon material, and uniformly mixing the carbon material with a solvent to obtain a mixed solution;
pulping the mixed solution to obtain carbon material slurry with the particle size of less than 15 micrometers;
adding a hydrophobic polymer and a pore-forming agent into the carbon material slurry, and pulping for 2-5 h at 12000-20000 rpm to obtain slurry with the particle size of less than 15 microns;
and baking the slurry at 50-90 ℃ to form paste, thereby obtaining the hydrophobic breathable layer raw material.
4. The method of preparing a gas diffusion electrode of claim 3, wherein the carbon material comprises at least one of conductive carbon black, carbon nanotubes, and acetylene black; and/or the presence of a gas in the gas,
the solvent comprises at least one of water, absolute ethyl alcohol, n-propanol and isopropanol; and/or the presence of a gas in the gas,
the hydrophobic polymer comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; and/or the presence of a gas in the gas,
the pore-forming agent comprises at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate.
5. The method for producing a gas diffusion electrode according to claim 3, wherein the mass of the hydrophobic polymer is 40 to 80% of the mass of the carbon material; and/or the presence of a gas in the gas,
the mass of the pore-forming agent is 10-20% of the mass of the carbon material.
6. The method of manufacturing a gas diffusion electrode according to claim 1, further comprising, before step S30, the steps of:
crushing and sieving a catalyst and a carbon material, and uniformly mixing the catalyst and the carbon material with a solvent to obtain a first solution;
pulping the first solution to obtain mixed slurry with the particle size of less than 15 mu m;
adding a hydrophobic polymer and a pore-forming agent into the mixed slurry, and pulping for 2-5 h at 12000-20000 rpm to obtain a catalyst layer slurry with the particle size of less than 15 microns;
and baking the catalyst layer slurry at 50-90 ℃ to form paste, thereby obtaining the catalyst layer raw material.
7. The method of making a gas diffusion electrode of claim 6, wherein said catalyst comprises a manganese dioxide catalyst; and/or the presence of a gas in the gas,
the carbon material includes at least one of conductive carbon black, carbon nanotubes, and acetylene black; and/or the presence of a gas in the gas,
the solvent comprises at least one of water, absolute ethyl alcohol, n-propanol and isopropanol; and/or the presence of a gas in the gas,
the hydrophobic polymer comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; and/or the presence of a gas in the gas,
the pore-forming agent comprises at least one of sodium sulfate, ammonium oxalate, ammonium bicarbonate and lithium carbonate; and/or the presence of a gas in the gas,
the mass ratio of the catalyst to the carbon material is 1.5-5: 1; and/or the presence of a gas in the gas,
the mass of the hydrophobic polymer is 20-40% of the total mass of the carbon material and the catalyst; and/or the presence of a gas in the gas,
the mass of the pore-forming agent is 10-20% of the total mass of the carbon material and the catalyst.
8. The method for producing a gas diffusion electrode according to claim 1, wherein in step S40:
in the hot pressing treatment, the hot pressing pressure is 1.5-5 MPa, and the hot pressing time is 5-10 min.
9. A metal-air battery comprising a gas diffusion electrode produced by the method of producing a gas diffusion electrode according to any one of claims 1 to 8.
10. The electrochemical oxygen producing process features that water and carbon dioxide are used as reaction material and electrolysis is performed on the anode to produce O2While CO is present2Electrochemical reaction is carried out under the action of a cathode catalyst,
wherein the cathode is a gas diffusion electrode prepared by the method of manufacturing a gas diffusion electrode according to any one of claims 1 to 8.
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| CN109888299A (en) * | 2017-12-06 | 2019-06-14 | 中国科学院大连化学物理研究所 | A kind of metal air battery cathodes and preparation method thereof |
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