CN107369838A - It is a kind of to exempt from hot pressing combination electrode and preparation method thereof for DMFC - Google Patents

Abstract

The invention discloses a heat-free pressing composite electrode for direct methanol fuel cells and a preparation method thereof. The electrode includes an integrated flow field diffusion layer and a catalytic layer; the integrated flow field diffusion layer includes a substrate and a filling layer; the substrate is a metal fiber or metal powder sintered porous plate with a porosity gradient in the thickness direction; the The filling layer is attached to the side of the substrate with a smaller porosity and part of the internal space; the catalytic layer is attached to the surface of the filling layer; the preparation method of the heat-free pressing composite electrode for direct methanol fuel cells of the present invention comprises the following steps : (1) preparation of substrate; (2) preparation of filling layer; (3) preparation of integrated flow field diffusion layer; (4) preparation of catalytic layer; (5) preparation of composite electrode. The invention proposes the integrated preparation of the flow field and the diffusion layer, which saves the separate processing and flow field preparation process, simplifies the preparation process of the key component of the battery-membrane electrode, and has the characteristics of high efficiency and low cost.

Description

A kind of heat-free pressing composite electrode for direct methanol fuel cell and its preparation method

technical field

The invention relates to the field of fuel cells, in particular to a heat-free pressing composite electrode for direct methanol fuel cells and a preparation method thereof.

Background technique

At present, the energy crisis is becoming more and more serious, and the traditional chemical energy has disadvantages such as large environmental pollution and low energy utilization rate. Energy is continuously converted into electrical energy. Direct methanol fuel cell (DMFC) is a fuel cell that uses methanol and oxygen as raw materials. It has the advantages of relatively simple structure, convenient manufacture, high energy density, easy transportation and storage of fuel, and relatively safe fuel. It is a research hotspot of scientific research institutions and major companies.

The structure of DMFC mainly includes end plate, collector plate, flow field plate and membrane electrode, and the membrane electrode is subdivided into diffusion layer, catalytic layer and proton exchange membrane. In the traditional manufacturing process of each component, most of the flow field plates need to be formed separately on metal or graphite plates through machining, stamping and other processes. For the mainstream processing technology of membrane electrodes, the diffusion layer is generally made of hydrophilic and hydrophobic carbon paper or carbon cloth, and the microporous layer is prepared on the surface; the catalytic layer is either attached to the microporous layer or attached to the proton exchange membrane. on, and then hot-pressed at a certain temperature and pressure to form a membrane-electrode assembly. The separate preparation of the flow field and the diffusion layer and the processing of the components of the membrane electrode by hot pressing make the entire process of DMFC manufacturing more complicated, the processing time is longer, and more manpower, material and financial resources are consumed. During the battery assembly process, the flow field plate and the membrane electrode are separate plate components, which are compressed to a certain extent by the assembly mechanical force to reduce the contact resistance, but the contact resistance still accounts for a large part of the overall resistance. A large part, thus increasing the energy loss of the battery.

Contents of the invention

In order to solve the problem of cumbersome processing or preparation processes for each part of DMFC, thereby simplifying the process steps and reducing the processing and manufacturing costs, the invention provides a heat-free pressing composite electrode for direct methanol fuel cells and a preparation method thereof.

For direct methanol fuel cells, the flow field, diffusion layer and catalytic layer have a great influence on the performance of the cell. The heat-free composite electrode of the present invention first combines the traditional separately separated and mechanically assembled flow field plate and the diffusion layer into one to prepare an integrated flow field diffusion layer. On the basis of the porous and three-dimensional structure of the integrated flow field diffusion layer, the slurry of the catalytic layer is sprayed to form a catalytic layer with a high specific surface area, thereby forming a flow field-diffusion layer-catalytic layer composite electrode, which simplifies the battery structure and significantly reduces zero. While improving the resistance and contact resistance of the components themselves, it can better manage the reactants and products, which is conducive to improving battery performance.

The present invention is realized through the following technical solutions.

A heat-free and press-free composite electrode for direct methanol fuel cells, including an integrated flow field diffusion layer and a catalytic layer;

The integrated flow field diffusion layer includes a base and a filling layer; the base is a metal fiber or metal powder sintered porous plate with a porosity gradient in the thickness direction; the filling layer is attached to the side of the base with a smaller porosity and part of the internal space;

The catalytic layer is attached to the surface of the filling layer.

Further, when the heat-free press composite electrode is used in a direct methanol fuel cell, the heat-free press composite electrode is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and one side of the catalytic layer close to the exchange membrane.

Further, the thickness of the base is 1-2 mm.

Further, the substrate has a porosity gradient ranging from 60% to 90% in the thickness direction.

Further, the material of the metal fiber or metal powder is preferably copper or stainless steel.

Further, the heat-free pressure-free composite electrode for direct methanol fuel cells includes an anode composite electrode or a cathode composite electrode.

Furthermore, in the anode composite electrode, the substrate is hydrophilic, and the material of the filling layer is a mixture of conductive carbon black and perfluorosulfonic acid (Nafion), and the mass ratio of conductive carbon black and perfluorosulfonic acid is 20 :1~4:1.

Furthermore, in the cathode composite electrode, the substrate is hydrophobic, and the material of the filling layer is a mixture of conductive carbon black and polytetrafluoroethylene (PTFE), and the mass ratio of conductive carbon black and polytetrafluoroethylene is 10: 1~1:1.

Further, the material of the catalytic layer is a mixture of catalyst and perfluorosulfonic acid (Nafion), and the mass ratio of catalyst and perfluorosulfonic acid is 5:1-1:1.

A method for preparing a heat-free pressing composite electrode for a direct methanol fuel cell described in any one of the above, specifically comprising the following steps:

(1) Preparation of substrate: According to the order of porosity gradient, metal fibers or metal powder sintered porous plates with different porosities are aligned and stacked in a pressure mold, and placed in a sintering furnace for heat preservation and sintering to obtain a block of composite sintered fibers or a perforated plate to obtain said substrate;

(2) Preparation of the filling layer: mix the solution mixture of the filling layer material with the dispersant, and disperse evenly to obtain the filling layer slurry, place the base on the heating platform and heat it to a temperature above the boiling point of the dispersant, and fill the filling layer slurry The material is uniformly scraped or sprayed on the side of the substrate with smaller porosity, the dispersant and solvent in the slurry are volatilized, and an attached filling layer is obtained on the substrate;

(3) Preparation of the integrated flow field diffusion layer: heat-insulating and heating the substrate attached with the filling layer to obtain the integrated flow field diffusion layer;

(4) Preparation of the catalytic layer: Mix and disperse the solution mixture of the catalytic layer material and the dispersant evenly to obtain the catalytic layer slurry, place the integrated flow field diffusion layer on the heating platform and heat it to a temperature above the boiling point of the dispersant , uniformly spraying the catalytic layer slurry onto the filled layer, volatilizing the dispersant and solvent in the slurry to obtain the catalytic layer;

(5) Preparation of the composite electrode: the integrated flow field diffusion layer prepared with the catalytic layer was placed in a vacuum drying oven for drying treatment to obtain the heat-free press composite electrode for direct methanol fuel cells.

Further, in step (1), the heat preservation sintering is heat preservation sintering at 300-500° C. for 0.5-2 hours under a hydrogen or argon protective atmosphere.

Further, in step (1), when preparing the base of the anode composite electrode, the obtained bulk composite sintered fiber or porous plate is subjected to hydrophilic treatment, that is, the base of the anode composite electrode is obtained.

Further, in step (1), when preparing the base of the cathode composite electrode, the obtained bulk composite sintered fiber or porous plate is subjected to hydrophobic treatment to obtain the base of the cathode composite electrode.

Further, in step (2), the preparation of the filling layer slurry specifically includes: uniformly mixing conductive carbon black, dispersant and Nafion solution to make anode filling layer slurry; mixing conductive carbon black, dispersant and PTFE emulsion Mix evenly to make cathode filling layer slurry;

After the dispersant and solvent volatilize, conductive carbon black and Nafion remain on the substrate of the anode composite electrode to form an anode filling layer, and conductive carbon black and PTFE remain on the substrate of the cathode composite electrode to form a cathode filling layer; the solvent includes water.

Further, in step (3), the heat preservation and heating treatment is carried out at 250-300° C. for 0.5-1 hour, and then heated to 350-400° C. for 0.5-1 hour.

Further, in steps (2) and (4), the dispersant includes isopropanol; the function of the dispersant is to disperse the material of the filling layer or the material of the catalytic layer evenly, so as to facilitate scraping or spraying processing.

Further, in step (4), after the dispersant and the solvent are volatilized, the residual catalyst and Nafion form a catalytic layer, and the catalyst is a general-purpose catalyst for direct methanol fuel cells, including platinum series catalysts.

The filling layer and the catalytic layer are prepared by scraping or spraying, in which most of the raw materials of the filling layer enter part of the internal space of the substrate, while the diameters of the residue particles attached to the surface of the filling layer and the catalytic layer are very small, about nanometers. Therefore, the thickness of the filling layer and the catalytic layer is very thin, and the thickness of the overall heat-free composite electrode is basically maintained at the base thickness level.

Further, in step (5), the drying treatment is drying at a temperature above the boiling point of the dispersant for 1-2 hours.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) In the preparation method of the present invention, the integrated preparation of the flow field and the diffusion layer is proposed, and the metal fiber or metal powder sintered porous plate with a porosity gradient is used as the flow field and at the same time as the substrate of the diffusion layer to prepare an integrated The diffusion layer of the flow field eliminates the process steps of separate processing or preparation of the flow field, and simplifies the manufacturing process of the direct methanol fuel cell;

(2) When the heat-free pressing composite electrode of the present invention is used in a direct methanol fuel cell, it is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and is directly compressed with the proton exchange membrane by assembly force, No need for hot pressing, which simplifies the preparation process of the membrane electrode, the key component of the battery, and has the characteristics of high efficiency and low cost;

(3) The present invention uses metal fiber or metal powder sintered porous plate with porosity gradient and hydrophilic/hydrophobic properties as the electrode substrate, which can better treat reactants compared with traditional perforated plate and porous plate with constant pore gradient. and product management.

Description of drawings

Fig. 1 is the schematic diagram of the assembly of the heat-free composite electrode used in the direct methanol fuel cell of the present invention;

Fig. 2 is a cross-sectional schematic diagram of an integrated flow field diffusion layer with three sintered porous plates in the form of gradually changing porosity in Example 1;

FIG. 3 is a comparison chart of the performance of a battery equipped with a traditional hot-pressed electrode and a hot-pressed composite electrode in Example 1. FIG.

detailed description

In order to further understand the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited thereto.

The present invention is a heat-free composite electrode for direct methanol fuel cells, comprising an integrated flow field diffusion layer and a catalytic layer; the integrated flow field diffusion layer includes a base and a filling layer;

The substrate is a metal fiber or metal powder sintered porous plate with a porosity gradient in the thickness direction. The material of the metal fiber or metal powder is copper or stainless steel, and the thickness of the substrate is 1~2mm; the substrate has a thickness of 60 in the thickness direction. Porosity gradients ranging from ~90%;

The filling layer is attached to the side of the substrate with less porosity and part of the internal space;

The heat-free composite electrode for direct methanol fuel cells includes an anode composite electrode or a cathode composite electrode; in the anode composite electrode, the substrate is hydrophilic, and the material of the filling layer is a mixture of conductive carbon black and perfluorosulfonic acid, which is conductive The mass ratio of carbon black and perfluorosulfonic acid is 20:1~4:1; in the cathode composite electrode, the substrate is hydrophobic, and the material of the filling layer is a mixture of conductive carbon black and polytetrafluoroethylene, conductive carbon black and The mass ratio of PTFE is 10:1~1:1;

The catalytic layer is attached to the surface of the filling layer, and the material of the catalytic layer is a mixture of catalyst and perfluorosulfonic acid, and the mass ratio of catalyst and perfluorosulfonic acid is 5:1~1:1.

The schematic diagram of the assembly of the heat-free composite electrode of the present invention for direct methanol fuel cells is shown in Fig. Electric plate 3-1, anode polytetrafluoroethylene gasket 4-1, proton exchange membrane 5, cathode polytetrafluoroethylene gasket 4-2, cathode collector plate 3-2, cathode silica gel gasket 2-2 and cathode The extreme plate 6, the heat-free composite electrode is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, wherein the anode composite electrode 7-1 is directly placed on the anode collector plate 3-1 of the direct methanol fuel cell In the stepped through hole in the middle, the cathode composite electrode 7-2 is directly placed in the stepped through hole in the middle of the cathode collector plate 3-2 of the direct methanol fuel cell, and the catalytic layer side of the composite electrode is close to the proton exchange membrane 5 .

Example 1

This embodiment is an integrated flow field diffusion layer with three copper sintered porous plates in the form of gradually changing porosity, and its cross-sectional schematic diagram is shown in FIG. 2 . Among them, the three copper sintered porous plates include porous plate 8, porous plate 9 and porous plate 10 in turn, and the porosity of the three sintered porous plates is 90%, 80% and 70% in turn, forming a porous plate with a thickness of 1 mm. Plate; the filling layer 11 is attached to the side of the perforated plate 10 and part of its internal space.

The material of the cathode filling layer is a mixture of conductive carbon black and polytetrafluoroethylene with a mass ratio of 5:1, and the material of the anode filling layer is a mixture of conductive carbon black and perfluorosulfonic acid with a mass ratio of 10:1;

The material of the catalytic layer is a mixture of catalyst and perfluorosulfonic acid at a mass ratio of 3:1, and the catalytic layer is attached to the surface of the filling layer 11 in FIG. 2, thereby forming a heat-free and press-free composite electrode for direct methanol fuel cells.

The heat-free composite electrode of this embodiment and the traditional heat-pressed electrode are assembled in a direct methanol fuel cell, and the output voltage and power density are tested at a methanol concentration of 4 mol/L at normal temperature and pressure. The test results are as follows: As shown in Figure 3; it can be seen from Figure 3 that the maximum output voltage and maximum power density of the battery assembled by the heat-free composite electrode of this embodiment are close, and the heat-free composite electrode of this embodiment is an integration of the flow field and the diffusion layer , directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and directly compressed with the proton exchange membrane by assembly force, without hot pressing, and can better manage the reactants and products.

Example 2

This embodiment is an integrated flow field diffusion layer with three copper sintered porous plates in the form of gradually changing porosity. Among them, the porosity of the three sintered porous plates is 85%, 75% and 65% in turn, forming a porous plate with a thickness of 1.5 mm. The filling layer is attached to the side of the porous plate with a porosity of 65% and part of its internal space. .

The material of the cathode filling layer is a mixture of conductive carbon black and polytetrafluoroethylene with a mass ratio of 10:1, and the material of the anode filling layer is a mixture of conductive carbon black and perfluorosulfonic acid with a mass ratio of 5:1;

The material of the catalytic layer is a mixture of catalyst and perfluorosulfonic acid with a mass ratio of 1:1, and the catalytic layer is attached to the surface of the filling layer, thereby forming a heat-free and press-free composite electrode for direct methanol fuel cells.

The heat-free composite electrode of this embodiment is applied to direct methanol combustion cells, and is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and is directly compressed with the proton exchange membrane by assembly force without hot pressing. Better management of reactants and products.

Example 3

This embodiment is an integrated flow field diffusion layer with two copper sintered porous plates in the form of gradually changing porosity. The porosity of the three sintered porous plates is 80%, 70% and 60% in turn, forming a porous plate with a thickness of 2 mm. The filling layer is attached to the side and part of the internal space of the porous plate with a porosity of 60%.

The material of the cathode filling layer is a mixture of conductive carbon black and polytetrafluoroethylene with a mass ratio of 20:1, and the material of the anode filling layer is a mixture of conductive carbon black and perfluorosulfonic acid with a mass ratio of 1:1;

The material of the catalytic layer is a mixture of catalyst and perfluorosulfonic acid with a mass ratio of 5:1, and the catalytic layer is attached to the surface of the filling layer, thereby forming a heat-free press composite electrode for direct methanol fuel cells.

The heat-free composite electrode of this embodiment is applied to direct methanol combustion cells, and is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and is directly compressed with the proton exchange membrane by assembly force without hot pressing. Better management of reactants and products.

Example 4

A method for preparing a heat-free pressing composite electrode for a direct methanol fuel cell, comprising the steps of:

(1) Substrate preparation: According to the order of porosity gradient, three copper sintered porous plates with a thickness of 0.5 mm and a porosity of 60%, 70% and 80% were aligned and stacked in the pressure mold in sequence, and the mold Put it into a sintering furnace with gas atmosphere protection and keep it warm at 300°C for 0.5h to obtain a composite porous plate;

After cleaning the block composite porous plate, soak it in the deionized aqueous solution of NaOH (concentration: 3mol/L) and K ₂ S ₂ O ₈ (concentration: 0.2mol/L) for 5min, carry out hydrophilic treatment, take it out, deionize Rinse with water, air-dry to obtain the anode substrate;

After cleaning the block composite porous plate, soak it in the deionized aqueous solution of NaOH (concentration: 3mol/L) and K ₂ S ₂ O ₈ (concentration: 0.2mol/L) for 5min, take it out, wash it with deionized water, and air dry; Then keep it in a resistance furnace with hydrogen protection at 500°C for 2 hours, take it out and soak it in 0.01mol/L stearic acid ethanol solution for 3 days, perform hydrophobic treatment, take it out, clean it with acetone, and air-dry it to obtain the cathode substrate;

(2) Filling layer preparation: uniformly mix conductive carbon black, isopropanol dispersant and 5% Nafion solution at a mass ratio of 1:20:1 to make an anode slurry;

Conductive carbon black, isopropanol dispersant and PTFE emulsion with a mass fraction of 40% are evenly mixed according to the mass ratio of 4:80:1 to make a cathode slurry;

Put the substrate on the heating platform and heat it to 85°C, spray the slurry evenly on the side with smaller porosity of the substrate, and the dispersant and solvent in the slurry will volatilize;

After the dispersant and solvent are volatilized, conductive carbon black and Nafion remain on the anode substrate to form an anode filling layer, and conductive carbon black and PTFE remain on the cathode substrate to form a cathode filling layer;

(3) Preparation of the integrated flow field diffusion layer: the substrate with the filling layer attached is kept at 250°C for 0.5h in a hydrogen protective atmosphere, and then heated to 350°C for 0.5h to obtain an integrated flow field diffusion layer;

(4) Catalytic layer preparation: Mix the catalyst, isopropanol and 5% Nafion solution in a mass ratio of 1:20:4 to make an ink-like slurry, and place the integrated flow field diffusion layer on the heating platform Heating to 85°C, spraying the slurry evenly on the filling layer, the isopropanol and solvent in the slurry volatilize, leaving the catalyst and Nafion to obtain the catalytic layer;

(5) Preparation of composite electrodes: Put the integrated flow field diffusion layer prepared with the catalytic layer into a vacuum drying oven, and dry at 85°C for 1 hour to obtain an anode composite electrode and a cathode composite electrode, respectively.

The prepared heat-free composite electrode is applied to the direct methanol combustion cell, and is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and is directly compressed with the proton exchange membrane by assembly force, without hot pressing, and can be more Good management of reactants and products.

Example 5

A method for preparing a heat-free pressing composite electrode for a direct methanol fuel cell, comprising the steps of:

(1) Substrate preparation: According to the order of porosity gradient, three copper sintered porous plates with a thickness of 0.5mm and a porosity of 60%, 70% and 80% were aligned and stacked in the pressure mold in sequence, and the mold Put it into a sintering furnace with gas atmosphere protection and keep it warm at 400 ° C for 1 hour to obtain a composite porous plate;

After cleaning the bulk composite porous plate, soak it in the deionized aqueous solution of NaOH (concentration: 1mol/L) and K ₂ S ₂ O ₈ (concentration: 0.05mol/L) for 30min, carry out hydrophilic treatment, take it out, deionize Rinse with water, air-dry to obtain the anode substrate;

After cleaning the block composite porous plate, soak it in the deionized aqueous solution of NaOH (concentration: 1mol/L) and K ₂ S ₂ O ₈ (concentration: 0.05mol/L) for 30min, take it out, wash it with deionized water, and air dry; Then keep warm at 300°C for 0.5h in a hydrogen-protected resistance furnace, take it out, soak it in 0.01mol/L stearic acid ethanol solution for 1 day, perform hydrophobic treatment, take it out, clean it with acetone, and air-dry it to obtain the cathode substrate;

(2) Filling layer preparation: uniformly mix conductive carbon black, isopropanol dispersant and 5% Nafion solution at a mass ratio of 1:20:2 to make an anode slurry;

Conductive carbon black, isopropanol dispersant and PTFE emulsion with a mass fraction of 40% are evenly mixed according to the mass ratio of 2:40:1 to make a cathode slurry;

Put the substrate on the heating platform and heat it to 85°C, spray the slurry evenly on the side with smaller porosity of the substrate, and the dispersant and solvent in the slurry will volatilize;

After the dispersant and solvent are volatilized, conductive carbon black and Nafion remain on the anode substrate to form an anode filling layer, and conductive carbon black and PTFE remain on the cathode substrate to form a cathode filling layer;

(3) Preparation of the integrated flow field diffusion layer: the substrate with the filling layer attached is kept at 275°C for 0.75h in a hydrogen protective atmosphere, and then heated to 375°C for 0.75h to obtain an integrated flow field diffusion layer;

(4) Catalytic layer preparation: Mix the catalyst, isopropanol and 5% Nafion solution in a mass ratio of 1:20:8 to make an ink-like slurry, and place the integrated flow field diffusion layer on the heating platform Heating to 85°C, spraying the slurry evenly on the filling layer, the isopropanol and solvent in the slurry volatilize, leaving the catalyst and Nafion to obtain the catalytic layer;

(5) Preparation of composite electrodes: Put the integrated flow field diffusion layer prepared with the catalytic layer into a vacuum drying oven, and dry at 85°C for 1 hour to obtain an anode composite electrode and a cathode composite electrode, respectively.

The prepared heat-free composite electrode is applied to the direct methanol combustion cell, and is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and is directly compressed with the proton exchange membrane by assembly force, without hot pressing, and can be more Good management of reactants and products.

Example 6

A method for preparing a heat-free pressing composite electrode for a direct methanol fuel cell, comprising the steps of:

(1) Substrate preparation: According to the order of porosity gradient, three copper sintered porous plates with a thickness of 0.5mm and a porosity of 60%, 70% and 80% were aligned and stacked in the pressure mold in sequence, and the mold Put it into a sintering furnace with gas atmosphere protection and keep it warm at 500 ° C for 2 hours to obtain a composite porous plate;

After cleaning the block composite porous plate, soak it in the deionized aqueous solution of NaOH (concentration: 2mol/L) and K ₂ S ₂ O ₈ (concentration: 0.1mol/L) for 60min, carry out hydrophilic treatment, take it out, deionize Rinse with water, air-dry to obtain the anode substrate;

After cleaning the block composite porous plate, soak it in the deionized aqueous solution of NaOH (concentration: 2mol/L) and K ₂ S ₂ O ₈ (concentration: 0.1mol/L) for 60min, take it out, wash it with deionized water, and air dry; Then keep warm at 400°C for 1 hour in a resistance furnace with hydrogen protection, take it out and soak it in 0.005mol/L stearic acid ethanol solution for 2 days, perform hydrophobic treatment, take it out, wash it with acetone, and air-dry it to obtain the cathode substrate;

(2) Filling layer preparation: uniformly mix conductive carbon black, isopropanol dispersant and 5% Nafion solution at a mass ratio of 1:20:5 to make an anode slurry;

Conductive carbon black, isopropanol dispersant and PTFE emulsion with a mass fraction of 40% are evenly mixed according to the mass ratio of 2:40:5 to make a cathode slurry;

Put the substrate on the heating platform and heat it to 85°C, spray the slurry evenly on the side with smaller porosity of the substrate, and the dispersant and solvent in the slurry will volatilize;

After the dispersant and solvent are volatilized, conductive carbon black and Nafion remain on the anode substrate to form an anode filling layer, and conductive carbon black and PTFE remain on the cathode substrate to form a cathode filling layer;

(3) Preparation of the integrated flow field diffusion layer: the substrate with the filling layer attached is kept at 300°C for 1 hour in a hydrogen protective atmosphere, and then heated to 400°C for 1 hour to obtain an integrated flow field diffusion layer;

(4) Catalytic layer preparation: Mix the catalyst, isopropanol and 5% Nafion solution in a mass ratio of 1:20:20 to make an ink-like slurry, and place the integrated flow field diffusion layer on the heating platform Heating to 85°C, spraying the slurry evenly on the filled layer, the isopropanol in the slurry volatilizes, leaving the catalyst and Nafion to obtain the catalytic layer;

(5) Composite electrode preparation: put the integrated flow field diffusion layer prepared with the catalytic layer into a vacuum drying oven, and dry at 85°C for 2 hours to obtain an anode composite electrode and a cathode composite electrode, respectively.

The prepared heat-free composite electrode is applied to the direct methanol combustion cell, and is directly placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and is directly compressed with the proton exchange membrane by assembly force, without hot pressing, and can be more Good management of reactants and products.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A heat-free pressure-free composite electrode for direct methanol fuel cells, characterized in that it includes an integrated flow field diffusion layer and a catalytic layer; The integrated flow field diffusion layer includes a base and a filling layer; the base is a metal fiber or metal powder sintered porous plate with a porosity gradient in the thickness direction; the filling layer is attached to the side of the base with a smaller porosity and part of the internal space; The catalytic layer is attached to the surface of the filling layer; The heat-free pressing composite electrode for direct methanol fuel cells includes an anode composite electrode or a cathode composite electrode. 2. A kind of heat-free pressing composite electrode for direct methanol fuel cell according to claim 1, it is characterized in that, when described heat-free pressing composite electrode is used for direct methanol fuel cell, directly described heat-free pressing The composite electrode is placed in the stepped through hole in the middle of the collector plate of the direct methanol fuel cell, and one side of the catalytic layer is close to the proton exchange membrane. 3. A kind of heat-free pressing composite electrode for direct methanol fuel cell according to claim 1, it is characterized in that, the thickness of described base is 1～2mm; The porosity gradient varies in the range of 90%; the material of the metal fiber or metal powder is copper or stainless steel. 4. a kind of heat-free composite electrode for direct methanol fuel cell according to claim 1, is characterized in that, in described anode composite electrode, substrate has hydrophilicity, and the material of filling layer is conductive carbon black A mixture of conductive carbon black and perfluorosulfonic acid, the mass ratio of conductive carbon black to perfluorosulfonic acid is 20:1~4:1. 5. a kind of heat-free pressure-free composite electrode for direct methanol fuel cell according to claim 1, is characterized in that, in described cathode composite electrode, substrate has hydrophobicity, and the material of filling layer is conductive carbon black and The mixture of polytetrafluoroethylene, the mass ratio of conductive carbon black and polytetrafluoroethylene is 10:1~1:1. 6. A kind of heat-free pressing composite electrode for direct methanol fuel cell according to claim 1, is characterized in that, the material of described catalytic layer is the mixture of catalyst and perfluorosulfonic acid, and catalyst and perfluorosulfonic acid The mass ratio of acid is 5:1~1:1. 7. The method for preparing a kind of heat-free composite electrode for direct methanol fuel cell described in any one of claims 1 to 6, is characterized in that, specifically comprises the following steps: (1) Preparation of substrate: According to the order of porosity gradient, metal fibers or metal powder sintered porous plates with different porosities are aligned and stacked in a pressure mold, and placed in a sintering furnace for heat preservation and sintering to obtain a block of composite sintered fibers or a perforated plate to obtain the substrate; (2) Preparation of the filling layer: mix the solution mixture of the filling layer material with the dispersant, and disperse evenly to obtain the filling layer slurry, place the base on the heating platform and heat it to a temperature above the boiling point of the dispersant, and mix the filling layer slurry Evenly scrape or spray on the side with smaller porosity of the substrate, the dispersant and solvent in the slurry will volatilize, and an attached filling layer will be obtained on the substrate; (3) Preparation of the integrated flow field diffusion layer: heat-insulating and heating the substrate attached with the filling layer to obtain the integrated flow field diffusion layer; (4) Preparation of the catalytic layer: Mix and disperse the solution mixture of the catalytic layer material and the dispersant evenly to obtain the catalytic layer slurry, place the integrated flow field diffusion layer on the heating platform and heat it to a temperature above the boiling point of the dispersant, uniformly spraying the catalytic layer slurry onto the filled layer, volatilizing the dispersant and solvent in the slurry to obtain the catalytic layer; (5) Preparation of the composite electrode: the integrated flow field diffusion layer prepared with the catalytic layer was placed in a vacuum drying oven for drying treatment to obtain the heat-free press composite electrode for direct methanol fuel cells. 8. A method for preparing a heat-free composite electrode for a direct methanol fuel cell according to claim 7, characterized in that, in step (1), the heat preservation and sintering is carried out under a hydrogen or argon protective atmosphere Heat preservation and sintering at 300~500°C for 0.5~2h; when preparing the substrate of the anode composite electrode, perform hydrophilic treatment on the obtained block composite sintered fiber or porous plate to obtain the substrate of the anode composite electrode; when preparing the substrate of the cathode composite electrode, Hydrophobic treatment is carried out on the obtained bulk composite sintered fiber or porous plate to obtain the base of the cathode composite electrode. 9. A method for preparing a heat-free composite electrode for direct methanol fuel cells according to claim 7, characterized in that, in step (3), the heat preservation heat treatment is heat preservation at 250~300°C After 0.5~1h, raise the temperature to 350~400℃ and keep it warm for 0.5~1h. 10. A method for preparing a heat-free press-free composite electrode for direct methanol fuel cells according to claim 7, characterized in that, in steps (2) and (4), the dispersant includes isopropanol; In step (5), the drying treatment is drying at a temperature above the boiling point of the dispersant for 1-2 hours.