CN109449466B

CN109449466B - Preparation method of membrane electrode and preparation method of anode catalyst layer of membrane electrode

Info

Publication number: CN109449466B
Application number: CN201811237120.8A
Authority: CN
Inventors: 熊子昂; 向华; 徐玉福; 王令兆
Original assignee: Shandong Weiqing Power Technology Co ltd
Current assignee: Shandong Weiqing Power Technology Co ltd
Priority date: 2018-10-23
Filing date: 2018-10-23
Publication date: 2020-11-24
Anticipated expiration: 2038-10-23
Also published as: CN109449466A

Abstract

The invention discloses a preparation method of a membrane electrode and a preparation method of an anode catalyst layer of the membrane electrode, wherein the preparation method comprises the following steps: immersing one side of the proton exchange membrane in a platinum precursor/water solution; mixing carbon carrier metal or metal oxide with perfluorosulfonic acid resin, and uniformly performing ultrasonic treatment in an organic solvent to form black catalyst slurry; putting the prepared anode substrate catalyst layer into an electroplating grinding tool for pulse electrodeposition, introducing saturated nitrogen, and inserting an auxiliary electrode and a reference electrode; setting pulse frequency, on-off time and total pulse deposition time to obtain an in-situ embedded core-shell catalyst of the anode catalyst layer; the preparation method of the membrane electrode and the preparation method of the anode catalyst layer of the membrane electrode can improve the preparation efficiency, improve the controllability and the precision of the preparation process and reduce the cost.

Description

Preparation method of membrane electrode and preparation method of anode catalyst layer of membrane electrode

Technical Field

The invention relates to the technical field of proton exchange membrane fuel cells, in particular to a preparation method of a membrane electrode of a proton exchange membrane fuel cell and a preparation method of an anode catalyst layer of the membrane electrode.

Background

In the past decades, proton exchange membrane fuel cells have been generated with great enthusiasm, and many countries have made great technological investment and progress on their development. At present, proton exchange membrane fuel cells are mature in technology, and part of products are put into the market.

However, there are still some problems in the development of fuel cells, and many technical challenges are faced on the way to commercialization. The most outstanding problem is that the fuel cell uses a large amount of noble metal platinum as a catalyst to accelerate the power generation process, but the cost and the plasticity of the fuel cell are increased greatly, so that the value of the fuel cell is reflected off the life curve of people.

In view of the above, there is an urgent need to design a new preparation method of catalyst to overcome the above-mentioned disadvantages of the existing preparation method.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the preparation method of the membrane electrode and the preparation method of the anode catalyst layer of the membrane electrode are provided, the dosage of Pt can be greatly reduced, the utilization rate of Pt is effectively improved, and the cost is reduced.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method of making a membrane electrode, the method comprising:

(1) preparing a proton exchange membrane with a platinum precursor on the surface by an ion exchange method: firstly, cutting a proton exchange membrane into 2.5 multiplied by 2.5cm, soaking the proton exchange membrane in dilute sulfuric acid and hydrogen peroxide in sequence, and then washing the proton exchange membrane clean by distilled water; the proton exchange membrane is a perfluorosulfonic polymer membrane;

(2) preparing 5 mmol/L-100 mmol/L of platinum precursor aqueous solution, wherein the platinum precursor is platinum tetraamine dichloride;

(3) immersing one surface of the proton exchange membrane treated in the step (1) into the solution obtained in the step (2), standing for 1-60 min to obtain a platinum precursor modified perfluorinated sulfonic acid polymeric membrane, which is recorded as Pt⁺-Nafion, to be used in step (5);

(4) preparing a carbon carrier-supported metal or a carbon carrier-supported metal oxide as a core material: firstly, carrying out oxidation treatment on a carbon carrier to improve the surface hydrophilicity and obtain more defect sites; mixing the treated carbon carrier with a precursor of a corresponding target metal, and reacting to obtain a metal or metal oxide loaded on the carbon carrier as a substrate core material; the metal comprises at least one of Pd, Ru, Ir, Au and Co; the metal oxide includes WO₃，WO_2.7，W₁₁O₄₉，RuO₂，IrO₂，CeO₂，MoO₃At least one of; the loading capacity of the metal or the metal oxide on the carbon carrier is 3% -50%, and the size of the nano particles is 3-20 nm;

wherein, the carbon carrier loaded metal is obtained by adopting a dipping reduction method: firstly, adding citric acid serving as a complexing agent into a precursor aqueous solution of a target metal to be loaded, adding 20-300 mg of treated carbon powder while stirring, placing the mixed solution in a water bath kettle at the temperature of 60-80 ℃, stirring and evaporating, and then placing in a vacuum oven for drying for 6 hours at the temperature of 60-80 ℃; taking out the dried powder, properly grinding, transferring the powder into a tubular furnace, roasting in a hydrogen atmosphere at the temperature of 100-300 ℃ for 2-6 h; then washing the mixture for 1-2 times by using deionized water, and placing the mixture in a vacuum drying oven for vacuum drying for 12 hours at 70 ℃; wherein the molar ratio of the citric acid to the total metal of the precursor is 0.25: 1-4: 1; the metal precursor of the carbon carrier loaded metal is one of ruthenium chloride, palladium chloride, iridium chloride, chloroauric acid or cobalt chloride;

the carbon carrier loaded metal oxide nanoparticles are obtained by a hydrothermal method: firstly, mixing a metal oxide precursor solution to be loaded with a complexing agent sodium citrate, adding 20-300 mg of treated carbon powder under stirring and ultrasonic treatment, placing the mixed solution into a 50ml polytetrafluoroethylene Teflon high-pressure kettle, and then placing the kettle into a drying oven for hydrothermal reaction, wherein the temperature of the drying oven is 150-220 ℃, and the reaction time is 10-18 h; fully washing the mixture for 1-2 times by using deionized water after complete reaction, and putting the collected powder into a drying oven for vacuum drying for 12 hours at 70 ℃; wherein the molar ratio of the sodium citrate to the total metal of the precursor is 0.25: 1-4: 1; the metal oxide precursor of the carbon carrier loaded metal oxide is one of sodium tungstate, ruthenium chloride, iridium chloride, sodium molybdate and cerium carbonate;

(5) mixing the carbon carrier loaded metal or metal oxide obtained in the step (4) with a binder, and uniformly performing ultrasonic treatment in an organic solvent to form black catalyst slurry;

the adhesive comprises at least one of polytetrafluoroethylene emulsion, perfluorosulfonic acid resin emulsion and fluorocarbon resin emulsion, and the usage amount of the adhesive is that the adhesive accounts for 10 to 30 percent of the total catalyst by dry polymer;

the organic solvent comprises ethanol or isopropanol;

spraying ink-shaped composite carrier slurry on the Pt prepared in the step (3)⁺The method comprises the following steps of (1) placing Nafion on one side with a platinum precursor modification in a drying oven at the temperature of 60-90 ℃ for 1-3 hours to ensure that a solvent is completely volatilized, and thus obtaining an anode substrate catalysis layer containing a nuclear material;

(6) putting the anode substrate catalysis layer containing the nuclear material prepared in the step (5) on an electroplating mouldCarrying out pulse electrodeposition, introducing saturated nitrogen, and inserting an auxiliary electrode and a reference electrode; setting pulse frequency, on-off time and total pulse deposition time to obtain an in-situ embedded core-shell catalyst loaded on an anode catalyst layer on one side of a proton exchange membrane; the Pt loading capacity is controlled to be 0.01-0.1 mg^-2To (c) to (d);

wherein, the embedded core-shell catalyst is prepared by adopting a pulse electrodeposition mode, and the communication time t is_on0.5 ms-10 ms, off-time t_off1.5 ms-30 ms, and the total pulse number is 1000-10000; the electroplating solution is 0.1-0.5M H₂SO₄The solution was mixed with 0.3M Na₂SO₄As a supporting electrolyte;

(7) mixing a commercial platinum-carbon catalyst with the mass fraction of 40% of platinum and a perfluorinated sulfonic acid polymer according to the mass ratio of 2.5:1, adding a volatile organic solvent, dispersing into an ink-like solution through ultrasonic oscillation, spraying the ink-like solution on the other side of the proton exchange membrane which is prepared in the step (6) and is loaded with the embedded core-shell catalyst in situ through the anode catalyst layer, wherein the loading amount of Pt is controlled to be 0.05-0.5 mg.cm^-2Then, carrying out heat treatment on the sprayed proton exchange membrane at the temperature of 60-90 ℃ for 20-60 minutes to obtain a membrane electrode cathode catalyst layer;

(8) and (4) respectively attaching two gas diffusion layers to two sides of the proton exchange membrane with the cathode and anode catalyst layers after the treatment in the step (7), so as to obtain the anode catalyst layer membrane electrode with the ultralow platinum loading and self-humidifying property.

A preparation method of a membrane electrode anode catalysis layer comprises the following steps:

(3) soaking one surface of the proton exchange membrane treated in the step (1) in waterStanding the solution obtained in the step (2) for 1-60 min to obtain a platinum precursor modified perfluorinated sulfonic acid polymeric membrane marked as Pt⁺-Nafion, to be used in step (5);

the organic solvent comprises ethanol or isopropanol;

(6) putting the anode substrate catalyst layer containing the nuclear material prepared in the step (5) into an electroplating mould for pulse electrodeposition, introducing saturated nitrogen, and inserting an auxiliary electrode and a reference electrode; setting pulse frequency, on-off time and total pulse deposition time to obtain an in-situ embedded core-shell catalyst loaded on an anode catalyst layer on one side of a proton exchange membrane; the Pt loading capacity is controlled to be 0.01-0.1 mg^-2To (c) to (d);

wherein, the embedded core-shell catalyst is prepared by adopting a pulse electrodeposition mode, and the communication time t is_on0.5 ms-10 ms, off-time t_off1.5 ms-30 ms, and the total pulse number is 1000-10000; the electroplating solution is 0.1-0.5M H₂SO₄The solution was mixed with 0.3M Na₂SO₄As a supporting electrolyte.

A method of making a membrane electrode, the method comprising:

step S1, preparing a proton exchange membrane with a platinum precursor on the surface;

step S2, preparing a carbon carrier loaded with noble metal or metal oxide as a nuclear material;

step S3, mixing the carbon carrier metal or metal oxide obtained in the step S2 with a perfluorosulfonic acid resin solution, and performing ultrasonic homogenization in an organic solvent to form catalyst slurry; spraying the catalyst slurry on one side of the proton exchange membrane prepared in the step S1 to obtain an anode substrate catalyst layer containing the nuclear material;

s4, putting the anode substrate catalyst layer prepared in the step S3 on an electroplating mould for pulse electrodeposition, and setting pulse frequency, on-off time and total pulse deposition time to obtain the in-situ embedded core-shell catalyst loaded on the anode catalyst layer on one side of the proton exchange membrane;

step S5, mixing a platinum-carbon catalyst and a perfluorinated sulfonic acid polymer, adding a volatile organic solvent, dispersing into an ink-like solution through ultrasonic oscillation, spraying the ink-like solution on the second side of the proton exchange membrane, and then performing heat treatment on the sprayed proton exchange membrane to obtain a membrane electrode cathode catalyst layer;

and step S6, obtaining the anode membrane electrode with the embedded core-shell structure catalyst and the ultralow platinum loading capacity.

As an embodiment of the present invention, in step S1, the proton exchange membrane includes a perfluorosulfonic polymer membrane; step S1 includes:

step S11, preparing the proton exchange membrane with the platinum precursor on the surface by an ion exchange method: firstly, cutting a proton exchange membrane into 2.5 multiplied by 2.5cm, soaking the proton exchange membrane in dilute sulfuric acid and hydrogen peroxide in sequence, and then washing the proton exchange membrane clean by distilled water;

step S12, preparing a platinum precursor aqueous solution; the platinum precursor is platinum tetraamine dichloride;

and S13, immersing one surface of the proton exchange membrane treated in the step S11 in the solution obtained in the step S12, and standing for 1-60 min to obtain the Pt precursor modified perfluorinated sulfonic acid polymeric membrane, which is recorded as Pt + -Nafion.

As an embodiment of the present invention, in step S2, the carbon support is first subjected to an oxidation treatment to improve the surface hydrophilicity and obtain more defect sites; mixing the treated carbon carrier with a corresponding target metal precursor, and reacting to obtain a metal or metal oxide loaded on the carbon carrier serving as a substrate core material;

the metal comprises at least one of Pd, Ru, Ir, Au and Co; the metal oxide includes WO₃，WO_2.7，W₁₁O₄₉，RuO₂，IrO₂，CeO₂，MoO₃At least one of; the loading capacity of the metal or the metal oxide on the carbon carrier is 3% -50%, and the size of the nano particles is 3-20 nm.

In an embodiment of the present invention, in step S2, the carbon support supported metal is obtained by using a dipping reduction method: firstly, adding citric acid serving as a complexing agent into a precursor aqueous solution of a target metal to be loaded, adding 20-300 mg of treated carbon powder while stirring, placing the mixed solution in a water bath kettle at the temperature of 60-80 ℃, stirring and evaporating, and then placing in a vacuum oven for drying for 6 hours at the temperature of 60-80 ℃; taking out the dried powder, properly grinding, transferring the powder into a tubular furnace, roasting in a hydrogen atmosphere at the temperature of 100-300 ℃ for 2-6 h; then washing the mixture for 1-2 times by using deionized water, and placing the mixture in a vacuum drying oven for vacuum drying for 12 hours at 70 ℃; wherein the molar ratio of the citric acid to the total metal of the precursor is 0.25: 1-4: 1; the metal precursor of the carbon carrier loaded metal is one of ruthenium chloride, palladium chloride, iridium chloride, chloroauric acid or cobalt chloride;

the carbon carrier loaded metal oxide nanoparticles are obtained by a hydrothermal method: firstly, mixing a metal oxide precursor solution to be loaded with a complexing agent sodium citrate, adding 20-300 mg of treated carbon powder under stirring and ultrasonic treatment, placing the mixed solution into a 50ml polytetrafluoroethylene Teflon high-pressure kettle, and then placing the kettle into a drying oven for hydrothermal reaction, wherein the temperature of the drying oven is 150-220 ℃, and the reaction time is 10-18 h; fully washing the mixture for 1-2 times by using deionized water after complete reaction, and putting the collected powder into a drying oven for vacuum drying for 12 hours at 70 ℃; wherein the molar ratio of the sodium citrate to the total metal of the precursor is 0.25: 1-4: 1; the metal oxide precursor of the carbon carrier loaded metal oxide is one of sodium tungstate, ruthenium chloride, iridium chloride, sodium molybdate and cerium carbonate.

In step S3, after the catalyst slurry is sprayed on the first side of the proton exchange membrane, the proton exchange membrane is placed in an oven at 60 to 90 ℃ for 1 to 3 hours to ensure that the solvent is completely volatilized, and thus an anode substrate catalyst layer containing the nuclear material is prepared;

the adhesive comprises at least one of polytetrafluoroethylene emulsion, perfluorosulfonic acid resin emulsion and fluorocarbon resin emulsion, and the usage amount of the adhesive is that the adhesive accounts for 10 to 30 percent of the total catalyst by dry polymer; the organic solvent comprises ethanol or isopropanol.

As an embodiment of the present invention, in step S4, the prepared anode substrate catalyst layer is placed in an electroplating mold for pulse electrodeposition, saturated nitrogen gas is introduced, and an auxiliary electrode and a reference electrode are inserted; the Pt loading capacity is controlled to be 0.01-0.1 mg^-2To (c) to (d);

wherein, the embedded core-shell catalyst is prepared by adopting a pulse electrodeposition mode, and the communication time t is_on0.5 ms-10 ms, off-time t_off1.5 ms-30 ms, and the total pulse number is 1000-10000; the electroplating solution is 0.1-0.5M H₂SO₄Solution with 0.3MNa₂SO₄As a supporting electrolyte.

In step S5, a platinum-carbon catalyst with a platinum content of 40% by mass and a perfluorosulfonic acid polymer are mixed at a mass ratio of 2.5:1, and then a volatile organic solvent is added, and the mixture is dispersed into an ink-like solution by ultrasonic oscillation, and the ink-like solution is sprayed on the other side of the proton exchange membrane of step S3, wherein the loading amount of Pt is controlled to be 0.05-0.5 mg.cm^-2And then, carrying out heat treatment on the sprayed proton exchange membrane at the temperature of 60-90 ℃ for 20-60 minutes to obtain the cathode catalyst layer of the membrane electrode.

step S3, mixing the carbon carrier metal or metal oxide obtained in the step S2 with a perfluorosulfonic acid resin solution, and performing ultrasonic homogenization in an organic solvent to form catalyst slurry; the catalyst slurry is sprayed on one side of the proton exchange membrane prepared in step S1 to obtain the anode-substrate catalytic layer containing the nuclear material.

As an embodiment of the present invention, the preparation method further includes step S4, placing the anode substrate catalyst layer prepared in step S3 on an electroplating mold for pulse electrodeposition, and setting pulse frequency, on-off time, and total pulse deposition time, so as to obtain an in-situ embedded core-shell catalyst loaded on the anode catalyst layer on one side of the proton exchange membrane.

A preparation method of an embedded core-shell structure catalyst built in situ by an anode catalyst layer comprises the following steps:

(1) preparation of Pt by ion exchange⁺-Nafion；

(A) Taking a Nafion212 proton exchange membrane of 2.5cm multiplied by 2.5cm, putting the membrane into a hydrogen peroxide solution with the concentration of 5 percent for treatment for 3 hours under the treatment condition of 80 ℃, washing the membrane by deionized water, continuing the treatment for 3 hours at 80 ℃ in a sulfuric acid solution of 0.5M, finally washing the membrane by the deionized water, and putting the membrane into a beaker for storage for later use;

(B) gently paving the Nafion membrane treated in the step (A) on the surface of a 5mM platinum tetraamine dichloride solution to ensure that one side of the membrane is fully contacted with the solution, standing for 5min, taking out the Nafion membrane and cleaning to obtain Pt⁺-Nafion；

(2) Preparing a Ru/C substrate catalytic layer;

(A) carbon powder XC-72R pretreatment:

adding 10g of Vulcan XC-72R carbon powder into a 1L beaker, then adding 600mL of acetone, stirring for 5h at room temperature, then washing with deionized water, taking out and drying in an oven at 80 ℃; putting the dried powder into a tubular furnace, and roasting for 6 hours at 450 ℃ under the protection of nitrogen; then the carbon powder is oxidized to obtainThe collected powder is put into a 300mL three-neck flask, and 100mL 10% HNO is added₃And 50mL of 30% H₂O₂Heating and refluxing for 12h at 80 ℃, filtering, washing with secondary water to neutrality, and drying in an oven at 80 ℃ overnight;

(B) preparing Ru/C by an immersion method;

adding 287mg of citric acid into a 20ml beaker, then adding 49.7mg of ruthenium trichloride and 10ml of ethanol solution, stirring and ultrasonically treating, simultaneously adding 120mg of carbon powder, uniformly mixing, then putting the mixture into a water bath kettle at 80 ℃, stirring and evaporating, completely drying, taking out powder, putting the powder into a tubular furnace, heating to 180 ℃ in a hydrogen atmosphere, and reacting for 3 hours; then taking out the catalyst, washing the catalyst by using deionized water to remove impurities, and drying the obtained powder in an oven at 80 ℃;

(3) weighing and mixing Ru/C1.5mg prepared in the step (2) with perfluorosulfonic acid resin, wherein the mass ratio is 2.5:1, adding an isopropanol solvent into the mixture to prepare black slurry, and carrying out ultrasonic treatment for 30 min; then spraying ink-shaped composite carrier slurry on the Pt prepared in the step (1)⁺The surface of Nafion is placed in an oven at 70 ℃ for 3 hours to ensure that the solvent is completely volatilized, and the membrane electrode containing the anode substrate catalyst layer Ru/C and the Pt precursor is prepared;

(4) preparing a Ru @ Pt/C anode film electrode by adopting a constant current pulse method:

and (4) taking the membrane electrode prepared in the step (3) as a working electrode, putting the working electrode into an electroplating device, fixing the membrane electrode firmly by adopting a clamp, fully exposing one side with the catalysis layer in the electrolyte, and conducting electricity by adopting platinum sheets around the catalysis layer to ensure that the working electrode has a good electronic channel. And introducing nitrogen into the electrolyte to ensure that the solution does not contain oxygen. The composition of the electrolyte was 0.2M sulfuric acid and 0.2M sodium sulfate. The counter electrode is a platinum wire, and the reference electrode is an Ag/AgCl electrode; according to a preset constant current pulse deposition program, the peak current density is 20mA/cm²The conduction time is 1ms, the turn-off time is 5ms, the pulse number is 300, the electrodeposition temperature is room temperature, and the membrane electrode with the Ru @ Pt/C anode catalytic layer is obtained, wherein the platinum loading capacity is 0.01mg/cm²(ii) a The membrane electrode was placed in a 0.5M sulfuric acid solutionSoaking for 5H to exchange H + on the proton exchange membrane;

(5) preparing a cathode catalyst layer;

mixing a commercial platinum-carbon catalyst with the platinum mass fraction of 40% and a perfluorinated sulfonic acid polymer according to the mass ratio of 2.5:1, adding a volatile organic solvent, dispersing into an ink-like solution through ultrasonic oscillation, and spraying the ink-like solution on the other side of the proton exchange membrane in the step (4), wherein the loading amount of Pt is 0.2mg^-2Then, the sprayed proton exchange membrane is thermally treated for 30 minutes at 70 ℃ to prepare a membrane electrode cathode catalyst layer;

(6) and (3) respectively attaching two gas diffusion layers to two sides of the proton exchange membrane treated in the step (5) to obtain the anode membrane electrode with the embedded core-shell structure catalyst and the ultralow platinum loading capacity.

The invention has the beneficial effects that: according to the preparation method of the catalyst with the embedded core-shell structure in-situ construction of the anode catalyst layer, the Pt loading capacity in the anode membrane electrode of the fuel cell can be as low as 0.01mg/cm2, and the thickness of the Pt shell layer is controlled within 5 Pt single sub-layers, so that the use amount of Pt can be greatly reduced, the utilization rate of Pt is effectively improved, and the cost is reduced.

The ion exchange-pulse electrodeposition technology used in the invention can accurately construct the core-shell structure catalyst in situ at the three-phase site, and compared with the prior art, the method saves the process of preparing the catalyst, and is simple and convenient to operate and suitable for large-scale industrial production.

The ion exchange and pulse electrodeposition processes are completely independent, so that only an acidic solution is used as an electrolyte in pulse electrodeposition without intervention of a Pt precursor, recovery and treatment of the electroplating solution become simple and easy, and difficulty and energy consumption of industrial production are greatly reduced.

The anodic film electrode prepared by the invention shows excellent discharge performance, and when the Pt loading is one tenth of that of the commercial electrode, the activity per unit Pt mass is 10 times that of the commercial electrode. The anode catalyst layer in the invention has very thin thickness, which is beneficial to the transmission of protons, electrons, gas and water. The embedded core-shell structure catalyst in the anode catalytic layer has excellent stability.

The membrane electrode with low platinum loading capacity can be realized by directly depositing nano Pt active particles on the surface of a proton exchange membrane, so that platinum active sites can be fully exposed, the capability of a catalyst participating in chemical reaction is greatly improved, and the high-efficiency utilization of noble metal platinum is realized. The traditional preparation process does not show great advantages in practical application. The reason for this is that the platinum nanoparticles deposited on the surface of the proton exchange membrane often have a large particle size, usually over 100 nm, which greatly reduces the utilization rate of Pt, and thus the intended purpose is not achieved.

Drawings

FIG. 1 is a flow chart of a membrane electrode preparation method of the present invention.

FIG. 2 is a Transmission Electron Microscope (TEM) image of the core-shell structure catalyst Ru @ Pt/C in the anode catalytic layer prepared in example 1.

FIG. 3 is a graph of the membrane electrode discharge performance of the Ru @ Pt/C prepared in example 1.

FIG. 4 is a graph showing the discharge performance of the membrane electrode of comparative example 1 Pt/C.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

The description in this section is for several exemplary embodiments only, and the present invention is not limited only to the scope of the embodiments described. It is within the scope of the present disclosure and protection that the same or similar prior art means and some features of the embodiments may be interchanged.

The meaning of the platinum precursor is a precursor of the supported platinum catalyst.

In a proton exchange membrane fuel cell system, the three-dimensional structure of the catalyst layer and the distribution of the nano catalyst are reasonably designed, so that the active component can fully exert the self effect, and the method has very important significance for improving the market competitiveness of the whole fuel cell and promoting the whole hydrogen energy economy.

Referring to fig. 1, fig. 1 shows a flow chart of a method for preparing a membrane electrode (which may be a membrane electrode of a pem fuel cell) according to an embodiment of the present invention, and referring to fig. 1, in an embodiment of the present invention, the method for preparing a membrane electrode includes the following steps:

the organic solvent comprises ethanol or isopropanol;

(6) the step (A) is5) Putting the prepared anode substrate catalyst layer containing the nuclear material into an electroplating mould for pulse electrodeposition, introducing saturated nitrogen, and inserting an auxiliary electrode and a reference electrode; setting pulse frequency, on-off time and total pulse deposition time to obtain an in-situ embedded core-shell catalyst loaded on an anode catalyst layer on one side of a proton exchange membrane; the Pt loading capacity is controlled to be 0.01-0.1 mg^-2To (c) to (d);

The invention also discloses a preparation method of the membrane electrode anode catalyst layer, and in one embodiment of the invention, the preparation method of the membrane electrode anode catalyst layer comprises the following steps:

the organic solvent comprises ethanol or isopropanol;

wherein, the embedded core-shell catalyst is prepared by adopting a pulse electrodeposition mode, and the communication time t is_on0.5 ms-10 ms, off-time t_off1.5 ms-30 ms, and the total pulse number is 1000-10000; the electroplating solution is 0.1-0.5M H₂SO₄Solution with 0.3MNa₂SO₄As supporting electricityAnd (4) decomposing the materials.

In one embodiment of the present invention, a method of preparing a membrane electrode includes:

In one embodiment of the invention, the preparation method of the membrane electrode anode catalyst layer comprises the following steps:

The preparation method further comprises the step S4 of placing the anode substrate catalyst layer prepared in the step S3 on an electroplating mould for pulse electrodeposition, and setting the pulse frequency, the on-off time and the total pulse deposition time to obtain the in-situ embedded core-shell catalyst loaded on the anode catalyst layer on one side of the proton exchange membrane.

Example 1: ru @ Pt/C catalyst embedded in anode catalytic layer

(1) Preparation of Pt by ion exchange⁺-Nafion

(A) The Nafion212 proton exchange membrane of 2.5cm multiplied by 2.5cm is taken and put into 5 percent hydrogen peroxide solution for treatment for 3 hours under the condition of 80 ℃, after being washed by deionized water, the membrane is continuously treated for 3 hours under the condition of 80 ℃ in 0.5M sulfuric acid solution, and finally washed by deionized water and put into a beaker for storage for standby.

(B) Gently paving the Nafion membrane treated in the step (A) on the surface of a 5mM platinum tetraamine dichloride solution to ensure that one side of the membrane is fully contacted with the solution, standing for 5min, taking out the Nafion membrane and cleaning to obtain Pt⁺-Nafion。

(2) Preparation of Ru/C base catalytic layer

(A) Carbon powder XC-72R pretreatment:

adding 10g of Vulcan XC-72R carbon powder into a 1L beaker, then adding 600mL of acetone, stirring for 5h at room temperature, then washing with deionized water, taking out and drying in an oven at 80 ℃; putting the dried powder into a tubular furnace, and roasting for 6 hours at 450 ℃ under the protection of nitrogen; then carrying out oxidation treatment on carbon powder, putting the collected powder into a 300mL three-neck flask, and adding 100mL 10% HNO₃And 50mL of 30% H₂O₂Heated to reflux at 80 ℃ for 12h, filtered and washed twice with water to neutrality and dried in an oven at 80 ℃ overnight.

(B) Preparation of Ru/C by impregnation method

287mg of citric acid is added into a 20ml beaker, then 49.7mg of ruthenium trichloride and 10ml of ethanol solution are added for stirring and ultrasonic treatment, 120mg of carbon powder is added simultaneously, after uniform mixing, the mixture is placed into a water bath kettle at 80 ℃ for stirring and evaporation, after complete drying, the powder is taken out and placed into a tube furnace, heated to 180 ℃ in hydrogen atmosphere, and reacted for 3 hours. And then taking out the catalyst, washing the catalyst by using deionized water to remove impurities, and drying the obtained powder in an oven at 80 ℃.

(3) Weighing and mixing Ru/C1.5mg prepared in the step (2) with perfluorosulfonic acid resin, wherein the mass ratio is 2.5:1, adding an isopropanol solvent into the mixture to prepare black slurry, and carrying out ultrasonic treatment for 30 min. Then spraying ink-shaped composite carrier slurry on the Pt prepared in the step (1)⁺The surface of Nafion is placed in an oven at 70 ℃ for 3 hours to ensure that the solvent is completely volatilized, and the membrane electrode containing the anode substrate catalyst layer Ru/C and the Pt precursor is prepared;

and (4) taking the membrane electrode prepared in the step (3) as a working electrode, putting the working electrode into an electroplating device, fixing the membrane electrode firmly by adopting a clamp, fully exposing one side with the catalysis layer in the electrolyte, and conducting electricity by adopting platinum sheets around the catalysis layer to ensure that the working electrode has a good electronic channel. And introducing nitrogen into the electrolyte to ensure that the solution does not contain oxygen. The composition of the electrolyte was 0.2M sulfuric acid and 0.2M sodium sulfate. The counter electrode is a platinum wire, and the reference electrode is an Ag/AgCl electrode. According to a preset constant current pulse deposition program (the peak current density is 20 mA/cm)²The on-time is 1ms, the off-time is 5ms, the pulse number is 300, and the electrodeposition temperature is room temperature) to obtain a membrane electrode with a Ru @ Pt/C anode catalytic layer, wherein the platinum loading is 0.01mg/cm². And (3) putting the membrane electrode into a 0.5M sulfuric acid solution, soaking for 5 hours, and exchanging H & lt + & gt on the proton exchange membrane.

(5) Preparation of cathode catalyst layer

(7) Structure representation and performance test of anode embedded core-shell structure catalyst

(A) Structural characterization of the Ru @ Pt/C catalyst:

firstly, separating the catalyst in the anode membrane electrode catalyst layer from a Nafion membrane, ultrasonically mixing the peeled catalyst powder and an ethanol solution, dropping a small amount of the catalyst powder on the surface of a copper mesh by using a dropper, drying, and observing the particle size and the distribution of the catalyst by using a Transmission Electron Microscope (TEM).

FIG. 2 is a Transmission Electron Microscope (TEM) image of the catalyst Ru @ Pt/C with core-shell structure in the anode catalytic layer prepared in example 1, from which it can be seen that the catalyst is uniformly distributed on the carbon support, and through measurement and calculation, the average particle diameter of the catalyst is about 4 nm.

(B) The method comprises the following steps Single cell discharge test and stability test

And (3) putting the membrane electrode with the Ru @ Pt/C catalyst on the anode into a test cell, wherein the temperature of the cell is 70 ℃, 100% humidified gas is introduced into the cathode and the anode, and constant-current discharge is carried out on the electrode for 5 hours. Hydrogen was fed to the anode and compressed air to the cathode at 30psi on both sides. After the activation of the electrode is finished, a discharge polarization curve spectrogram of the electrode is obtained through testing, and a discharge performance graph of the Ru @ Pt/C membrane electrode prepared in the embodiment 1 is shown in a figure 3; as shown in fig. 3. As can be seen from FIG. 3, the membrane electrode shows excellent discharge performance, and the current density can reach 700mAcm at a voltage of 0.7V^-2. After 100-hour stability test, the electrode discharges in a constant current mode, and the current density does not obviously attenuate, which indicates that the electrode has good stability.

The performance and test method of the membrane electrode are the same as the above test method except for special description.

Comparative example 1: membrane electrode preparation Using commercial JM4100Pt/C as anode catalyst

(1) Commercial JM4100Pt/C catalystPreparing a membrane electrode by using a catalyst as an anode catalyst: the Pt loading capacity of the anode removing electrode is 0.1mgcm^-2Otherwise, the operation procedure was the same as in the (5) th step in example 1.

(2) Preparing a cathode catalytic layer: the same as described in step (4) of example 1.

(3) And (3) testing the membrane electrode performance: the method is as described in example 1, and the cell discharge performance is shown in fig. three. As can be seen from the figure, the discharge curve of the battery is similar to that of example 1, but the loading amount is indeed more than 10 times that of example 1. The current density obtained at a voltage of 0.7V is only 520mAcm^-2The current density was 70% of that at 0.7V in example 1. This phenomenon indicates that although the Pt loading of the electrode is high, due to the complexity in the catalytic layer and the uncontrollable property in the preparation process, most of Pt nanoparticles cannot play the due role, and the performance of the electrode is greatly limited to play and improve.

Comparing the discharge performance diagrams of fig. 3 and 4, it can be seen that the performance of the membrane electrode prepared by the method of embodiment 1 of the present invention is greatly improved. The membrane electrode prepared by the method of the embodiment 1 of the invention has the output current of about 1.15A/cm at 0.6V²(ii) a The current of the membrane electrode prepared by the common method is only 0.85A/cm at 0.6V²。

Example 2 intercalation of Pd @ Pt/C catalyst into the Anode catalyst layer

The preparation method is the same as that of example 1 except that

(1) Palladium chloride is used instead of ruthenium trichloride.

(2) Palladium chloride requires its dissolution using concentrated hydrochloric acid.

(3) The hydrogen reduction temperature is 120 ℃ and 3 h.

(4) The membrane electrode performance test and characterization were the same as in (7) of example 1. The single cell discharge performance of the electrode meter is very excellent, and the current density of the electrode meter can reach 700mAcm at the battery temperature of 70 ℃ and the voltage of 0.7V under the condition that the cathode and the anode are respectively humidified by 100 percent^-2。

Example 3 intercalation of Ir @ Pt/C catalyst into the Anode catalyst layer

The preparation method is the same as that of example 1 except that

(1) Iridium trichloride is used instead of ruthenium trichloride.

(2) The hydrogen reduction temperature is 300 ℃ for 2h

(3) The membrane electrode performance test and characterization were the same as in (7) of example 1. The discharge performance of the electrode is similar to that of example 1, and the current density of the electrode at the voltage of 0.7V can reach 720mAcm under the conditions that the cathode and the anode are respectively humidified by 100 percent and the temperature of the battery is 70 DEG C^-2。

Example 4 IrO Embedded in the Anode catalyst layer₂@ Pt/C catalyst

(1) Preparation of Pt by ion exchange method⁺-Nafion: the preparation procedure was the same as in example 1

(2) IrO2/C substrate catalytic layer: unlike example (1), the carbon-supported metal oxide nanoparticles mainly employed a hydrothermal method, otherwise: firstly, mixing a precursor iridium trichloride solution and a complexing agent sodium citrate with the mass ratio of 1:2.5, adding 50mg of treated carbon powder under stirring and ultrasonic treatment, placing the mixed solution into a 50ml polytetrafluoroethylene Teflon high-pressure kettle, and then placing the kettle into an oven for hydrothermal reaction, wherein the temperature of the oven is 180 ℃, and the reaction time is 12 hours. Fully washing the mixture for 1 to 2 times by using deionized water after complete reaction, and putting the collected powder into a drying box for vacuum drying for 12 hours at 70 ℃; the other steps were the same as in example (1).

(3) The anode contains IrO₂Preparation of the @ Pt/C catalytic layer: the preparation method is the same as that of example (1)

(4)IrO₂Preparation of @ Pt/C Membrane electrode: the preparation method is the same as that of example (1)

(5) The membrane electrode performance test and characterization were the same as in (7) of example 1. The electrode shows good anode hydrogen oxidation performance, and the current density of the electrode at 0.7V voltage can reach 730mAcm under the conditions that the cathode and the anode are respectively humidified by 100 percent and the temperature of the battery is 70 DEG C^-2。

Example 5 Implantation of RuO in the anodic catalytic layer₂@ Pt/C catalyst

The preparation method was the same as in example 4 except that the following points were different

(1) Preparation of RuO₂the/C precursor is ruthenium trichloride instead of iridium trichloride

(2) The hydrothermal temperature is 150 ℃, and the reaction time is 18h

(3) The membrane electrode performance test and characterization were the same as in (7) of example 1. The electrode has good discharge performance, and the current density of the electrode at 0.7V voltage can reach 650mAcm under the conditions that the cathode and the anode are respectively 100% humidified and the temperature of the battery is 70 DEG C^-2。

Example 6 intercalation of WO into the Anode catalyst layer₃@ Pt/C catalyst

(1) Preparation of WO₃the/C precursor is Na₂WO₃

(2) The hydrothermal temperature is 170 ℃, and the reaction time is 22h

(3) The membrane electrode performance test and characterization were the same as in (7) of example 1. The single cell performance of the electrode is general, and the current density of the electrode can reach 500mAcm under the conditions that the cathode and the anode are respectively humidified by 100 percent, the temperature of the battery is 70 ℃, and the voltage of the battery is 0.7V^-2。

Example 7 intercalation of MoO into the Anode catalyst layer₃@ Pt/C catalyst

(1) Preparation of MoO₃the/C precursor is Na₂MoO₃

(2) The hydrothermal temperature is 150 ℃, and the reaction time is 6h

(3) The membrane electrode performance test and characterization were the same as in (7) of example 1. The discharge performance of the electrode is that the current density of the electrode can reach 550mAcm under the conditions that the cathode and the anode are respectively humidified by 100 percent, the temperature of the battery is 70 ℃, and the voltage of the battery is 0.7V^-2。

In conclusion, the preparation method for the anode catalyst layer in-situ built embedded core-shell structure catalyst provided by the invention can improve the preparation efficiency, improve the controllability and precision of the preparation process and reduce the cost.

(1) The Pt loading capacity in the anode membrane electrode of the fuel cell can be as low as 0.01mg/cm2, and the thickness of the Pt shell layer is controlled within 5 Pt single sub-layers, so that the use amount of Pt can be greatly reduced, and the utilization rate of Pt is effectively improved.

(2) The ion exchange-pulse electrodeposition technology used in the invention can accurately construct the core-shell structure catalyst in situ at the three-phase site, and compared with the prior art, the method saves the process of preparing the catalyst, and is simple and convenient to operate and suitable for large-scale industrial production.

(3) The ion exchange and pulse electrodeposition processes are completely independent, so that only an acidic solution is used as an electrolyte in pulse electrodeposition without intervention of a Pt precursor, recovery and treatment of the electroplating solution become simple and easy, and difficulty and energy consumption of industrial production are greatly reduced.

(4) The anodic film electrode prepared by the invention shows excellent discharge performance, and when the Pt loading is one tenth of that of the commercial electrode, the activity per unit Pt mass is 10 times that of the commercial electrode.

(5) The anode catalyst layer in the invention has very thin thickness, which is beneficial to the transmission of protons, electrons, gas and water.

(6) The embedded core-shell structure catalyst in the anode catalytic layer has excellent stability.

The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

Claims

1. A method of making a membrane electrode, the method comprising:

(5) mixing the carbon carrier loaded metal or metal oxide obtained in the step (4) with an adhesive, and uniformly performing ultrasonic treatment in an organic solvent to form black catalyst slurry;

the organic solvent comprises ethanol or isopropanol;

spraying black catalyst slurry on the Pt prepared in the step (3)⁺The method comprises the following steps of (1) placing Nafion on one side with a platinum precursor modification in a drying oven at the temperature of 60-90 ℃ for 1-3 hours to ensure that a solvent is completely volatilized, and thus obtaining an anode substrate catalysis layer containing a nuclear material;

(6) putting the anode substrate catalyst layer containing the nuclear material prepared in the step (5) into an electroplating mould for pulse electrodeposition, introducing saturated nitrogen, and inserting an auxiliary electrode and a reference electrode; setting pulse frequency, on-off time and total pulse deposition time to obtain an in-situ embedded core-shell catalyst loaded on an anode catalyst layer on one side of a proton exchange membrane; the Pt loading capacity is controlled to be 0.01-0.1mg.cm^-2To (c) to (d);

2. A preparation method of a membrane electrode anode catalyst layer is characterized by comprising the following steps:

(4) preparation of carbon Supported Metal orThe carbon carrier supports metal oxide as a core material: firstly, carrying out oxidation treatment on a carbon carrier to improve the surface hydrophilicity and obtain more defect sites; mixing the treated carbon carrier with a precursor of a corresponding target metal, and reacting to obtain a metal or metal oxide loaded on the carbon carrier as a substrate core material; the metal comprises at least one of Pd, Ru, Ir, Au and Co; the metal oxide includes WO₃，WO_2.7，W₁₁O₄₉，RuO₂，IrO₂，CeO₂，MoO₃At least one of; the loading capacity of the metal or the metal oxide on the carbon carrier is 3% -50%, and the size of the nano particles is 3-20 nm;

the organic solvent comprises ethanol or isopropanol;

3. A method of making a membrane electrode, the method comprising:

4. The method of producing a membrane electrode according to claim 3, characterized in that:

in step S1, the proton exchange membrane includes a perfluorosulfonic polymer membrane; step S1 includes:

5. The method of producing a membrane electrode according to claim 3, characterized in that:

in step S2, the carbon support is first oxidized to improve the surface hydrophilicity and obtain more defect sites; mixing the treated carbon carrier with a corresponding target metal precursor, and reacting to obtain a metal or metal oxide loaded on the carbon carrier serving as a substrate core material;

the metal comprises at least one of Pd, Ru, Ir, Au and Co; the metal oxide includes WO₃，WO_2.7，W₁₁O₄₉，RuO₂，IrO₂，CeO₂，MoO₃At least one of; the loading capacity of the metal or the metal oxide on the carbon carrier is 3% -50%, and the size of the nano particles is 3-20 nm;

in step S2, the carbon carrier supported metal is obtained by a dipping reduction method: firstly, adding citric acid serving as a complexing agent into a precursor aqueous solution of a target metal to be loaded, adding 20-300 mg of treated carbon powder while stirring, placing the mixed solution in a water bath kettle at the temperature of 60-80 ℃, stirring and evaporating, and then placing in a vacuum oven for drying for 6 hours at the temperature of 60-80 ℃; taking out the dried powder, properly grinding, transferring the powder into a tubular furnace, roasting in a hydrogen atmosphere at the temperature of 100-300 ℃ for 2-6 h; then washing the mixture for 1-2 times by using deionized water, and placing the mixture in a vacuum drying oven for vacuum drying for 12 hours at 70 ℃; wherein the molar ratio of the citric acid to the total metal of the precursor is 0.25: 1-4: 1; the metal precursor of the carbon carrier loaded metal is one of ruthenium chloride, palladium chloride, iridium chloride, chloroauric acid or cobalt chloride;

6. The method of producing a membrane electrode according to claim 3, characterized in that:

in the step S3, after the catalyst slurry is sprayed on the first side of the proton exchange membrane, the proton exchange membrane is placed in an oven at the temperature of 60-90 ℃ for 1-3 h to ensure that the solvent is completely volatilized, and then the anode substrate catalyst layer containing the nuclear material is prepared;

the organic solvent comprises ethanol or isopropanol; in the step S4, the prepared anode substrate catalyst layer is put into an electroplating mold for pulse electrodeposition, saturated nitrogen is introduced, and an auxiliary electrode and a reference electrode are inserted; the Pt loading capacity is controlled to be 0.01-0.1 mg^-2To (c) to (d);

7. The method of producing a membrane electrode according to claim 3, characterized in that:

in the step S5, a platinum-carbon catalyst with platinum content of 40% by mass and a perfluorosulfonic acid polymer are mixed according to a mass ratio of 2.5:1, a volatile organic solvent is added, ultrasonic oscillation is carried out to disperse the mixture into an ink-like solution, the ink-like solution is sprayed on the other side of the proton exchange membrane in the step S3, and the loading amount of Pt is controlled to be 0.05-0.5 mg.cm^-2And then, carrying out heat treatment on the sprayed proton exchange membrane at the temperature of 60-90 ℃ for 20-60 minutes to obtain the cathode catalyst layer of the membrane electrode.

8. A method of making a membrane electrode, the method comprising:

(1) preparation of Pt by ion exchange⁺-Nafion；

(2) Preparing a Ru/C substrate catalytic layer;

(A) carbon powder XC-72R pretreatment:

adding 10g of Vulcan XC-72R carbon powder into a 1L beaker, then adding 600mL of acetone, stirring for 5h at room temperature, then washing with deionized water, taking out and drying in an oven at 80 ℃; putting the dried powder into a tubular furnace, and roasting for 6 hours at 450 ℃ under the protection of nitrogen; then carrying out oxidation treatment on carbon powder, putting the collected powder into a 300mL three-neck flask, and adding 100mL 10% HNO₃And 50mL of 30% H₂O₂Heating and refluxing for 12h at 80 ℃, filtering, washing with secondary water to neutrality, and drying in an oven at 80 ℃ overnight;

(B) preparing Ru/C by an immersion method;

taking the membrane electrode prepared in the step (3) as a working electrode, putting the working electrode into an electroplating device, fixing the membrane electrode firmly by adopting a clamp, fully exposing one side with a catalyst layer in electrolyte, and conducting electricity by adopting platinum sheets around the catalyst layer to ensure that the working electrode has a good electronic channel; introducing nitrogen into the electrolyte to ensure that the solution does not contain oxygen; the electrolyte composition was 0.2M sulfuric acid and 0.2M sodium sulfate; the counter electrode is a platinum wire, and the reference electrode is an Ag/AgCl electrode; according to a preset constant current pulse deposition program, the peak current density is 20mA/cm²The conduction time is 1ms, the turn-off time is 5ms, the pulse number is 300, the electrodeposition temperature is room temperature, and the membrane electrode with the Ru @ Pt/C anode catalytic layer is obtained, wherein the platinum loading capacity is 0.01mg/cm²(ii) a The membrane electrode is put into 0.5M sulfuric acid solution to be soaked for 5 hours for H on the proton exchange membrane⁺Exchange of (2);

(5) preparing a cathode catalyst layer;