CN115995570A - Composite catalyst, preparation method thereof, membrane electrode and fuel cell - Google Patents
Composite catalyst, preparation method thereof, membrane electrode and fuel cell Download PDFInfo
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- CN115995570A CN115995570A CN202310059911.0A CN202310059911A CN115995570A CN 115995570 A CN115995570 A CN 115995570A CN 202310059911 A CN202310059911 A CN 202310059911A CN 115995570 A CN115995570 A CN 115995570A
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- 239000003054 catalyst Substances 0.000 title claims abstract description 235
- 239000012528 membrane Substances 0.000 title claims abstract description 57
- 239000002131 composite material Substances 0.000 title claims abstract description 55
- 239000000446 fuel Substances 0.000 title claims abstract description 52
- 238000002360 preparation method Methods 0.000 title abstract description 21
- 229910052751 metal Inorganic materials 0.000 claims abstract description 105
- 239000002184 metal Substances 0.000 claims abstract description 105
- 239000013110 organic ligand Substances 0.000 claims abstract description 100
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 23
- 229910000510 noble metal Inorganic materials 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 10
- WGOLHUGPTDEKCF-UHFFFAOYSA-N 5-bromopyridin-2-amine Chemical compound NC1=CC=C(Br)C=N1 WGOLHUGPTDEKCF-UHFFFAOYSA-N 0.000 claims description 8
- JPWXLRZTRDTFMR-UHFFFAOYSA-N 5-bromo-1h-pyridine-2-thione Chemical compound SC1=CC=C(Br)C=N1 JPWXLRZTRDTFMR-UHFFFAOYSA-N 0.000 claims description 6
- 238000009792 diffusion process Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
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- 239000000956 alloy Substances 0.000 claims description 5
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- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 3
- 125000001424 substituent group Chemical group 0.000 claims description 2
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 14
- 239000006257 cathode slurry Substances 0.000 description 13
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- 239000000203 mixture Substances 0.000 description 8
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- 238000011156 evaluation Methods 0.000 description 3
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- 238000010023 transfer printing Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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Abstract
A composite catalyst, a preparation method thereof, a membrane electrode and a fuel cell belong to the field of fuel cells. The composite catalyst comprises: the catalyst comprises a first component and a second component, wherein the first component comprises a first metal catalyst and a first organic ligand which is combined on the surface of the first metal catalyst in a removable way, and the coverage of the first organic ligand on the first metal catalyst is more than 50%; the second component comprises a second metal catalyst and optionally a second organic ligand, the second organic ligand can be combined on the surface of the second metal catalyst in a removable way, the coverage of the second organic ligand on the second metal catalyst is not more than 30%, and the arrangement can effectively improve the durability of the composite catalyst and delay the performance attenuation of the fuel cell.
Description
Technical Field
The present application relates to the field of fuel cells, and in particular, to a composite catalyst, a preparation method thereof, a membrane electrode and a fuel cell.
Background
Fuel cells are electrochemical devices that directly convert chemical energy of fuel (and oxidant) into electrical energy under the action of a catalyst. One of the key issues that fuel cells must address in the industrialization process is the life of the fuel cell, and the degradation of the catalyst on the fuel cell membrane electrode is a major factor affecting the durability of the fuel cell.
Disclosure of Invention
The application provides a composite catalyst, a preparation method thereof, a membrane electrode and a fuel cell, which can alleviate the problems of performance attenuation and poor durability of the fuel cell.
Embodiments of the present application are implemented as follows:
in a first aspect, the present examples provide a composite catalyst comprising: a first component and a second component.
Wherein the first component comprises a first metal catalyst and a first organic ligand which is combined on the surface of the first metal catalyst in a removable way, and the coverage of the first organic ligand on the first metal catalyst is more than 50%; the second component comprises a second metal catalyst and optionally a second organic ligand, the second organic ligand being capable of being removably bound to the surface of the second metal catalyst, the coverage of the second organic ligand on the second metal catalyst not exceeding 30%.
According to the composite catalyst, the first organic ligand and the second organic ligand with proper coverage rate are introduced through reasonable matching of the first component and the second component, so that the overall activity of the composite catalyst is less affected, the durability of the composite catalyst can be effectively improved, and further, when the composite catalyst is applied to a fuel cell, the influence on the initial performance of the fuel cell can be reduced, the performance attenuation of the fuel cell is effectively relieved, and the durability of the fuel cell is improved.
In some alternative embodiments, the coverage of the first organic ligand on the first metal catalyst is no more than 60%.
Optionally, the coverage of the second organic ligand on the second metal catalyst is no more than 10%.
Optionally, the coverage of the second organic ligand on the second metal catalyst is 0.
In some alternative embodiments, the mass ratio of the first component to the second component is from 0.1 to 2:10.
Optionally, the mass ratio of the first component to the second component is 0.1-1:10.
In some of the alternative embodiments of the present invention, the first organic ligand and the second organic ligand are respectively provided with-SH, -SSH, -Sac, -CN, -COOH and, -NH 2 、-CH 3 and-NC.
Optionally, the first organic ligand and the second organic ligand each comprise at least one of 5-bromopyridine-2-thiol, 2-amino-5-bromopyridine.
In some alternative embodiments, the first metal catalyst and the second metal catalyst comprise at least one of a carbon supported noble metal catalyst and a noble metal alloy catalyst, respectively.
Optionally, the first metal catalyst is the same as the second metal catalyst.
Optionally, the noble metal comprises platinum.
In a second aspect, the present examples provide a method for preparing a composite catalyst provided in the first aspect of the present application, comprising: dispersing the first metal catalyst in a solution containing a first organic ligand, and drying to obtain a first component, wherein the concentration of the first organic ligand in the solution is more than 300umol/L.
The preparation method of the composite catalyst provided in the first aspect is simple and controllable in preparation mode, effectively reduces preparation cost and is beneficial to industrial production.
Optionally, the concentration of the first organic ligand in the solution is no more than 500umol/L.
In a third aspect, the present examples provide a membrane electrode comprising a proton exchange membrane, a catalyst layer and a gas diffusion layer arranged in that order, the catalyst layer comprising the composite catalyst provided in the first aspect of the present application.
The membrane electrode provided by the application can effectively improve the durability of the membrane electrode by introducing the composite catalyst.
Alternatively, the composite catalyst is used as the membrane electrode based on the metal contained in the composite catalystThe loading on the catalyst is 0.03-0.6mg/cm 2 。
In some alternative embodiments, the catalyst layer includes a first component and a second component that are uniformly mixed.
In some alternative embodiments, the catalyst layer includes first catalyst layers and second catalyst layers alternately arranged in sequence in a thickness direction, the first catalyst layers containing a first component and not containing a second component, and the second catalyst layers containing a second component and not containing the first component.
In a fourth aspect, the present examples provide a fuel cell comprising at least one of the composite catalyst provided in the first aspect of the present application and the membrane electrode provided in the third aspect of the present application.
The fuel cell provided by the application can effectively improve the durability of the fuel cell and delay the performance attenuation of the fuel cell by utilizing the introduction of the composite catalyst.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustration of the present application and should not be construed as limiting the scope of the present application. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The attenuation of the catalyst on the membrane electrode of the fuel cell is a major factor affecting the durability of the fuel cell. In the actual use process, as the use times are increased, the activity of metal particles in the catalyst material is reduced, and the changes such as the loss of metal components and the like can lead to shorter service life of the membrane electrode, thereby leading to the performance attenuation of the fuel cell and shortening the service life.
In view of this, the present application provides a composite catalyst, which utilizes the ligand of the first component and the ligand of the second component, and makes the first metal catalyst inhibit the first metal catalyst from playing a catalytic role in the initial operation stage of the fuel cell by introducing the first organic ligand with high coverage rate, so as to protect the first metal catalyst, and alleviate the loss of the metal component caused by the increase of the number of times of use.
The following specifically describes a composite catalyst, a preparation method thereof, a membrane electrode and a fuel cell according to embodiments of the present application:
the present examples provide a composite catalyst comprising: a first component and a second component.
Wherein the first component comprises a first metal catalyst and a first organic ligand which is combined on the surface of the first metal catalyst in a removable way, and the coverage of the first organic ligand on the first metal catalyst is more than 50%; the second component comprises a second metal catalyst and optionally a second organic ligand, the second organic ligand being capable of being removably bound to the surface of the second metal catalyst, the coverage of the second organic ligand on the second metal catalyst not exceeding 30%.
According to the composite catalyst, the first organic ligand and the second organic ligand with proper coverage rate are introduced through reasonable matching of the first component and the second component, so that the overall activity of the composite catalyst is less affected, the durability of the composite catalyst can be effectively improved, and further, when the composite catalyst is applied to a fuel cell, the influence on the initial performance of the fuel cell can be reduced, the performance attenuation of the fuel cell is effectively relieved, and the durability of the fuel cell is improved.
Wherein the second component utilizes a second organic ligand with optionally low coverage rate to enable the second metal catalyst to play a catalytic role in the initial operation stage of the fuel cell; the first component utilizes the first organic ligand with high coverage rate to inhibit the first metal catalyst from playing a catalytic role in the initial operation stage of the fuel cell so as to protect the first metal catalyst, and the first organic ligand is combined on the surface of the first metal catalyst in a removable way, so that the first metal catalyst which is originally covered can be exposed in a mode of removing the first organic ligand after the durable catalyst is operated, and the first metal catalyst plays a catalytic role after being compared with the second metal catalyst, thereby improving the activity of the composite catalyst, compensating the performance reduction caused by the aging of the second metal catalyst, improving the durability of the composite catalyst as a whole, and further improving the durability of the membrane electrode and the fuel cell.
The coverage of the first organic ligand on the first metal catalyst is, for example, any one of or between any two of 51%, 55%, 60%, 65%, 70%.
In some alternative embodiments, the coverage of the first organic ligand on the first metal catalyst is no more than 60%.
That is, 50% < coverage of the first organic ligand on the first metal catalyst less than or equal to 60%, the activity of the first metal catalyst can be effectively inhibited within the coverage, and the preparation is convenient and the manufacturing cost is low.
It is understood that the coverage of the second organic ligand on the second metal catalyst is not more than 30% means that the coverage of the second organic ligand on the second metal catalyst is not more than 30%, and illustratively, the coverage of the second organic ligand on the second metal catalyst is, for example, any one value or between any two values of 30%, 25%, 20%, 18%, 15%, 12%, 10%, 7%, 5%, 3%, 0.
In some alternative embodiments, the coverage of the second organic ligand on the second metal catalyst is no more than 10%.
In the coverage range, the influence of the second organic ligand on the activity of the second metal catalyst is reduced by reducing the coverage, so that the influence on the initial performance of the fuel cell is reduced when the composite catalyst is applied to the fuel cell.
In some alternative embodiments, the coverage of the second organic ligand on the second metal catalyst is 0.
A coverage of the second organic ligand on the second metal catalyst of 0 means that the second component does not contain the second organic ligand, thereby further reducing the impact on the initial performance of the fuel cell when the durable catalyst is applied to the fuel cell.
In some alternative embodiments, the mass ratio of the first component to the second component is from 0.1 to 2:10.
The reasonable proportion is adopted to achieve proper ligand coverage rate, so that the durability of the composite catalyst is improved, the overall activity of the composite catalyst is less influenced, and the influence on the performance of the membrane electrode is further reduced.
Illustratively, the mass ratio of the first component to the second component is any one of, or between, 0.1:10, 0.3:10, 0.5:10, 0.7:10, 1:10, 1.2:10, 1.5:10, 1.7:10, 2:10.
Optionally, the mass ratio of the first component to the second component is 0.1-1:10.
The first organic ligand and the second organic ligand are both compounds capable of spontaneously binding to the surface of the metal catalyst during the reaction (e.g. by impregnation), which may be compounds having a strong chemical composition at the carbon chain ends.
In some of the alternative embodiments of the present invention, the first organic ligand and the second organic ligand are respectively provided with-SH, -SSH, -Sac, -CN, -COOH and, -NH 2 、-CH 3 and-NC.
The existence of the substituent groups can be utilized to enable the organic ligand to be spontaneously combined on the surface of the corresponding metal catalyst, and the subsequent removal is convenient.
The first organic ligand and the second organic ligand (hereinafter referred to as organic ligand) are both combined on the surfaces of the corresponding first metal catalyst and second metal catalyst (hereinafter referred to as metal catalyst) in a removable manner, and the composite catalyst is mainly applied to the fuel cell, so that ideal desorption conditions are as follows: the organic ligand selected may be slowly desorbed at the fuel cell operating potential, i.e., the surface of the metal catalyst covered by the organic ligand, which gradually desorbs during fuel cell operation; the metal catalyst surface covered by the organic ligand can be desorbed under the potential higher than the operation potential of the fuel cell, and the organic ligand is desorbed by additionally applying the potential after a period of time in the operation of the fuel cell.
Optionally, the first organic ligand and the second organic ligand each comprise at least one of 5-bromopyridine-2-thiol, 2-amino-5-bromopyridine. The organic ligands can be slowly desorbed by adjusting the potential of the fuel cell, and the operation is convenient.
It will be appreciated that the first organic ligand and the second organic ligand may be the same or may be different, alternatively the first organic ligand and the second organic ligand may be the same.
The first metal catalyst and the second metal catalyst each include at least one of a carbon-supported noble metal catalyst and a noble metal alloy catalyst. For example, the first metal catalyst and the second metal catalyst are both noble metal alloy catalysts, or both are carbon-supported noble metal catalysts, or one of them is a carbon-supported noble metal catalyst and the other is a noble metal alloy catalyst.
Optionally, the noble metal comprises at least one of ruthenium, rhodium, iridium, and platinum. Alternatively, the noble metal is platinum.
The first metal catalyst and the second metal catalyst may be the same or different, and in order to improve the performance of the composite catalyst, the first metal catalyst and the second metal catalyst may be the same.
The application provides a preparation method of the composite catalyst, which comprises the following steps:
s1, dispersing a first metal catalyst in a solution containing a first organic ligand, and drying to obtain a first component; wherein the concentration of the first organic ligand in the solution is greater than 300umol/L.
The first component is prepared by adopting an impregnation method, the operation is simple and controllable, and the coverage of the first organic ligand on the first metal catalyst is more than 50% by utilizing the concentration of the first organic ligand in the solution of more than 300umol/L.
Optionally, the concentration of the first organic ligand in the solution is no more than 500umol/L. By controlling the concentration of the first organic ligand in the solution, a coverage of the first organic ligand on the first metal catalyst of no more than 60% is achieved.
In order to sufficiently disperse the first metal catalyst in the solution containing the first organic ligand, it is possible to disperse the first metal catalyst in the dispersion, then continue to add the dispersion of the first organic ligand, and then disperse it uniformly by stirring or ultrasonic dispersion for, for example, 30 to 60 minutes.
The drying temperature is 60-100deg.C, and the drying can be carried out in, for example, a forced air drying oven or the like.
S2, obtaining a second component.
It should be noted that, when the surface of the second metal catalyst in the second component is bound with the second organic ligand, the second metal catalyst may be prepared by referring to the preparation method of the first organic ligand, and when the surface of the second metal catalyst has no second organic ligand, the second metal catalyst is directly used as the second component.
The application example provides a membrane electrode, and it includes proton exchange membrane, catalyst layer and the gas diffusion layer that arranges in proper order, and the catalyst layer includes the composite catalyst that this application provided.
The membrane electrode provided by the application can effectively improve the durability of the membrane electrode by introducing the composite catalyst.
In some alternative embodiments, the catalyst layer includes a first component and a second component that are uniformly mixed.
In some alternative embodiments, the catalyst layer includes first catalyst layers and second catalyst layers alternately arranged in sequence along a thickness direction thereof, the first catalyst layers containing a first component and not containing a second component, and the second catalyst layers containing a second component and not containing the first component.
Wherein, the arrangement direction of the proton exchange membrane, the catalyst layer and the gas diffusion layer is taken as the thickness direction of the catalyst layer. The first catalyst layer may be on a side of the second catalyst layer close to the proton exchange membrane, or on a side of the second catalyst layer away from the proton exchange membrane, which may be selected by those skilled in the art according to actual requirements, and is not limited herein.
Alternatively, in the membrane electrode, the metal (where metal refers to the total metal provided by the first metal catalyst and the second metal catalyst) loading provided by the composite catalyst is 0.03-0.6mg/cm 2 That is, the loading of the composite catalyst on the membrane electrode is 0.03-0.6mg/cm based on the metal contained in the composite catalyst 2 。
The catalyst layer of the membrane electrode can be prepared by dispersing a composite catalyst and an ionomer in a dispersion liquid to prepare catalyst slurry, then coating the catalyst slurry on a proton membrane to obtain a catalyst layer and proton membrane combination, or coating the catalyst slurry on a transfer membrane, and transferring the catalyst layer from the transfer membrane to the proton membrane by hot pressing to obtain the catalyst layer and proton membrane combination; finally, the catalyst layer, the proton membrane combination body and the gas diffusion layer are packaged to obtain the membrane electrode. Wherein the temperature of the transfer printing hot pressing is 100-180 ℃, the pressure of the transfer printing hot pressing is 0-3MPa, and the time of the transfer printing hot pressing is 60-240s.
It will be appreciated that when the catalyst layer comprises a first component and a second component that are uniformly mixed, the first component, the second component, and the ionomer may be directly co-dispersed in a dispersion to prepare a catalyst slurry, where the mass fraction of the catalyst in the catalyst slurry is, for example, 10 to 60wt%, and the mass fraction of the ionomer is, for example, 5 to 20wt%, and the dispersion includes, but is not limited to, stirring, ultrasonic, ball milling, sand milling, and the like, and may also be in the form of emulsion shearing, and the like.
When the catalyst layer includes a first catalyst layer and a second catalyst layer, the first component and the ionomer may be co-dispersed in the dispersion to prepare a first catalyst layer slurry, and the second component and the ionomer may be co-dispersed in the dispersion to prepare a second catalyst layer slurry, which is then layered.
The present examples provide a fuel cell comprising at least one of the above membrane electrode and the above composite catalyst.
The composite catalyst, the method for preparing the same, the membrane electrode and the fuel cell of the present application are described in further detail below with reference to examples.
Example 1
(1) Preparation of cathode slurry:
preparation of cathode slurry a:
50g of 5-bromopyridine-2-thiol and 10g of water are weighed in a beaker, and uniformly dispersed by ultrasound to obtain an organic ligand dispersion. 10g of cathode Pt/C catalyst and 20g of water were weighed and stirred in a beaker to be uniformly dispersed, thereby obtaining a first metal catalyst dispersion. 10g of an organic ligand dispersion was weighed and added to the first metal catalyst dispersion, and subjected to ultrasonic dispersion for 10 minutes, followed by stirring at a stirring rate of 500rpm for 30 minutes, and the obtained mixture was centrifuged and then dried in an oven at a temperature of 80℃to obtain a first component.
2g of the first component, 4g of Nafion solution, 25g of water and 15g of ethanol are weighed, and then the mixture is sheared and dispersed to obtain cathode slurry A.
Preparation of cathode slurry B:
the cathode Pt/C catalyst without organic ligand is taken as a second component (which is different from the first component in that the catalyst does not contain organic ligand), and 20g of the second component, 40g of Nafion solution, 200g of water and 150g of ethanol are weighed, mixed and then sheared and dispersed to obtain cathode slurry B.
(2) Preparation of anode slurry:
10g of anode Pt/C catalyst, 20g of Nafion solution, 100g of water and 75g of ethanol are weighed, mixed and then subjected to ultrasonic dispersion to obtain anode slurry.
(3) Preparing a catalytic layer and proton membrane combination:
coating cathode slurry A on the front surface of a proton membrane, drying, and coating cathode slurry B on the surface of the proton membrane, and drying to form a cathode catalyst layer, wherein the total Pt loading of the cathode catalyst layer is 0.3mg/cm 2 。
Anode is provided withThe slurry is coated on the back of the proton membrane, and dried to form an anode catalyst layer, and the Pt coating load of the anode catalyst layer is 0.05mg/cm 2 。
(4) And packaging the catalytic layer and proton membrane combination body and the gas diffusion layer to prepare the membrane electrode.
Example 2
It differs from example 1 only in that:
in the preparation process of the first component in the step (1), 5-bromopyridine-2-thiol is replaced by: 2-amino-5-bromopyridine.
Example 3
It differs from example 2 only in step (1):
preparation of cathode slurry a:
50g of 2-amino-5-bromopyridine and 10g of water are weighed in a beaker, and uniformly dispersed by ultrasound to obtain an organic ligand dispersion liquid. 20g of cathode Pt/C catalyst and 40g of water were weighed and stirred in a beaker to be uniformly dispersed, thereby obtaining a first metal catalyst dispersion. 20g of an organic ligand dispersion was weighed and added to the first metal catalyst dispersion, and subjected to ultrasonic dispersion for 10 minutes, then stirred at a stirring rate of 500rpm for 30 minutes, and the obtained mixture was centrifuged and then dried in an oven at a temperature of 80℃to obtain a first component.
2g of a first component (ligand-containing cathode Pt/C catalyst), 4g of Nafion solution, 25g of water and 15g of ethanol were weighed, and mixed, followed by shearing and dispersion to obtain cathode slurry A.
Preparation of cathode slurry B:
50g of 2-amino-5-bromopyridine and 10g of water are weighed in a beaker, and uniformly dispersed by ultrasound to obtain an organic ligand dispersion liquid. Weighing 20g of cathode Pt/C catalyst and 40g of water in a beaker, stirring to uniformly disperse the cathode Pt/C catalyst and the 40g of water to obtain a second metal catalyst dispersion, weighing 2g of organic ligand dispersion, adding the second metal catalyst dispersion into the second metal catalyst dispersion, carrying out ultrasonic treatment for 10min, stirring at 500rpm for 30min, centrifuging the obtained mixture, putting the mixture into a drying oven, drying the mixture, and setting the temperature of the drying oven to 80 ℃ to obtain a second component.
10g of a second component, 20g of Nafion solution, 100g of water and 75g of ethanol are weighed, mixed and sheared and dispersed to obtain cathode slurry B.
Comparative example 1
It differs from example 1 only in that:
the step (1) is replaced by: 25g of cathode Pt/C catalyst, 50g of Nafion solution, 250g of water and 187.5g of ethanol were weighed and mixed, followed by shearing and dispersing to obtain a cathode slurry.
Comparative example 2
It differs from example 1 only in that:
the step (1) is replaced by: 50g of 2-amino-5-bromopyridine and 10g of water are weighed in a beaker, and uniformly dispersed by ultrasound to obtain an organic ligand dispersion liquid. 20g of cathode Pt/C catalyst and 40g of water were weighed and stirred in a beaker to be uniformly dispersed, thereby obtaining a first metal catalyst dispersion. 2g of an organic ligand dispersion was weighed and added to the first metal catalyst dispersion, and subjected to ultrasonic dispersion for 10 minutes, followed by stirring at a stirring rate of 500rpm for 30 minutes, and the obtained mixture was centrifuged and then dried in an oven at a temperature of 80℃to obtain a first component.
12g of a first component (ligand-containing cathode Pt/C catalyst), 12g of Nafion solution, 120g of water and 90g of ethanol are weighed, mixed and then sheared and dispersed to obtain cathode slurry.
Test example 1
Ligand coverage and electrochemical active area (ECSA) of the first and second components prepared in examples 1 to 3 and comparative examples 1 to 2 were measured, and the results are shown in Table 1.
The ligand coverage rate evaluation mode is as follows: ligand coverage= [ ECSA (Pt) -ECSA (modified Pt) ]/ECSA (Pt) ×100 (%), ECSA of the first and second components were evaluated by half-cell Cyclic Voltammetry (CV), and were determined from the integral of hydrogen region of the CV curve.
TABLE 1 ligand coverage of the first and second Components
50cm of the preparation of examples 1-3 and comparative examples 1-2 2 The membrane electrode is placed in a single cell, oxygen (2 slm) is introduced into the cathode, the stack pressure is 70kPa, RH is 100%, hydrogen (1.5 slm) is introduced into the anode, the stack pressure is 80kPa, RH is 100%, the current 120A or the maximum value is kept to run for 1h until the voltage output is not increased any more, activation is completed, and then the single cell is subjected to catalyst durability evaluation.
The catalyst durability evaluation measurement mode is as follows: introducing hydrogen (0.2 slm) into the anode, introducing nitrogen (0.075 slm) into the cathode, introducing normal pressure, 100% RH, and square wave circulating for 40000 circles at a stack temperature of 80deg.C in a mode of maintaining a voltage of 0.6V for 3s and maintaining a voltage of 1V for 3s, determining ECSA and VI curves after circulating for 0, 10000, 20000, 30000 and 40000 circles, and recording the ECSA and VI curves at 0.8A/cm 2 Actual voltage at current density.
In the durability evaluation process, example 1 was subjected to cyclic voltammetric scanning in a potential range of 0.1 to 1.23V after 10000 cycles to remove 5-bromopyridine-2 thiol ligand adsorbed on the catalyst surface; examples 2, 3 and comparative example 1 did not treat during cycling and the 2-amino-5-bromopyridine ligands on the catalyst surface slowly desorbed during fuel cell operation.
The durability measurement results are shown in tables 2 and 3.
Table 2 durability measurement results
TABLE 3 durability measurement results
The actual voltage in Table 2 is 0.8A +.cm 2 At current density, the measured actual voltage after the target number of cycles is cycled, voltage decay value= (between the measured actual voltage after the target number of cycles and the actual voltage with the cycle number of 0) ×1000.
As can be seen from tables 2 and 3, the battery performance degradation of each of examples 1 and 2 was lower than that of comparative example 1, indicating that the durability of the membrane electrode was improved in examples 1 and 2. The reason for this is that the ligand on the catalyst partially covered with the ligand is desorbed and new catalytically active sites are exposed to improve the durability of the membrane electrode.
The decline in cell performance of example 3 was lower than that of comparative example 2, indicating that the durability of the membrane electrode of example 3 was improved, i.e., the durability of the membrane electrode with partially high ligand coverage and partially low ligand coverage was higher than that of the membrane electrode with overall low ligand coverage.
In summary, the composite catalyst, the preparation method thereof, the membrane electrode and the fuel cell can effectively improve the durability of the composite catalyst and the membrane electrode, alleviate the performance attenuation of the membrane electrode and the fuel cell and prolong the service life of the fuel cell.
The foregoing is merely a specific embodiment of the present application and is not intended to limit the application, and various modifications and variations may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims (10)
1. A composite catalyst, comprising:
a first component and a second component;
wherein the first component comprises a first metal catalyst and a first organic ligand which is combined on the surface of the first metal catalyst in a removable way, and the coverage of the first organic ligand on the first metal catalyst is more than 50%;
the second component comprises a second metal catalyst and optionally a second organic ligand, the second organic ligand being capable of being removably bound to the surface of the second metal catalyst, the coverage of the second organic ligand on the second metal catalyst not exceeding 30%.
2. The composite catalyst of claim 1, wherein the coverage of the first organic ligand on the first metal catalyst is no more than 60%;
optionally, the coverage of the second organic ligand on the second metal catalyst is no more than 10%;
optionally, the coverage of the second organic ligand on the second metal catalyst is 0.
3. The composite catalyst according to claim 1, wherein the mass ratio of the first component to the second component is 0.1-2:10;
optionally, the mass ratio of the first component to the second component is 0.1-1:10.
4. A composite catalyst according to any one of claims 1 to 3, wherein the first and second organic ligands have the respective groups-SH, -SSH, -Sac, -CN, -COOH, -NH 2 、-CH 3 And-at least one substituent in NC;
optionally, the first organic ligand and the second organic ligand each comprise at least one of 5-bromopyridine-2-thiol, 2-amino-5-bromopyridine.
5. The composite catalyst according to any one of claims 1 to 3, wherein the first metal catalyst and the second metal catalyst each comprise at least one of a carbon-supported noble metal catalyst and a noble metal alloy catalyst;
optionally, the first metal catalyst is the same as the second metal catalyst;
optionally, the noble metal comprises platinum.
6. The method for preparing a composite catalyst according to any one of claims 1 to 5, comprising:
dispersing a first metal catalyst in a solution containing the first organic ligand, and drying to obtain a first component;
wherein the concentration of the first organic ligand in the solution is greater than 300umol/L;
optionally, the concentration of the first organic ligand in the solution is no more than 500umol/L.
7. A membrane electrode, characterized by comprising a proton exchange membrane, a catalyst layer and a gas diffusion layer which are sequentially arranged, wherein the catalyst layer comprises the composite catalyst as claimed in any one of claims 1 to 5;
alternatively, the composite catalyst has a loading of 0.03-0.6mg/cm on the membrane electrode based on the metal contained in the composite catalyst 2 。
8. The membrane electrode of claim 7, wherein the catalyst layer comprises the first component and the second component mixed uniformly.
9. The membrane electrode according to claim 7, wherein the catalyst layer includes first catalyst layers and second catalyst layers alternately arranged in order in a thickness direction, the first catalyst layers containing the first component and not containing the second component, and the second catalyst layers containing the second component and not containing the first component.
10. A fuel cell comprising at least one of the composite catalyst according to any one of claims 1 to 5 and the membrane electrode according to any one of claims 8 to 9.
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| CN115377465A (en) * | 2021-05-17 | 2022-11-22 | 博隆能源股份有限公司 | Catalyst ink composition and method for forming hydrogen pump proton exchange membrane electrochemical cells |
| CN115441023A (en) * | 2022-08-24 | 2022-12-06 | 浙江天能氢能源科技有限公司 | Membrane electrode for fuel cell and preparation method thereof |
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| CN115188972A (en) * | 2022-08-19 | 2022-10-14 | 苏州安斯迪克氢能源科技有限公司 | Catalyst slurry, preparation method and application thereof, membrane electrode and fuel cell |
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