CN116314872B - Platinum-cobalt alloy catalyst and preparation method thereof - Google Patents

Platinum-cobalt alloy catalyst and preparation method thereof Download PDF

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CN116314872B
CN116314872B CN202310525009.3A CN202310525009A CN116314872B CN 116314872 B CN116314872 B CN 116314872B CN 202310525009 A CN202310525009 A CN 202310525009A CN 116314872 B CN116314872 B CN 116314872B
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colloid
platinum
cobalt alloy
catalyst
raw material
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CN116314872A (en
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范书琼
周有明
李承亮
仲小丽
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Suzhou Hydrogine Power Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
    • H01M4/8882—Heat treatment, e.g. drying, baking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/921—Alloys or mixtures with metallic elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • 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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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Manufacturing & Machinery (AREA)
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Abstract

A platinum cobalt alloy catalyst and a preparation method thereof, belonging to the technical field of fuel cells; the method comprises the following steps: obtaining a Pt/C raw material catalyst loaded with Pt; depositing a Co precursor and Pt colloid to a Pt/C raw material catalyst loaded with Pt under an alkaline condition to obtain an intermediate; performing heat treatment on the intermediate to obtain a platinum-cobalt alloy catalyst; co precursor and Pt colloid are coprecipitated to Pt/C raw material catalyst loaded with Pt under alkaline condition, in the coprecipitation process, co ion is faster than Pt colloid in alkaline condition, co is closer to inner side and Pt is closer to outer side after precipitation is completed, kinetic energy barrier of ordered rearrangement of atoms in solid phase is overcome through heat treatment, and then platinum-rich alloy catalyst with higher alloying degree is formed, further subsequent elution operation is avoided, preparation flow is shortened, and Co content is controllable.

Description

Platinum-cobalt alloy catalyst and preparation method thereof
Technical Field
The application relates to the technical field of fuel cells, in particular to a platinum-cobalt alloy catalyst and a preparation method thereof.
Background
The fuel cell can directly convert chemical energy into electric energy, and has the advantages of high energy utilization rate, environmental protection and zero emission. In a fuel cell, the catalyst is a core component of the fuel cell, and directly affects the energy efficiency and power of the fuel cell. Among the catalysts, pt-based fuel cell catalysts are the best choice for fuel cell catalysts due to their excellent catalytic activity and stability, and are the only fuel cell catalysts currently in commercial use. However, in the face of the high price and limited earth reserves of Pt, improving the utilization efficiency of Pt is the technological front of current fuel cells. At present, the transition metal elements such as Fe, co, ni and the like and Pt are used for alloying, so that the dosage of Pt can be reduced, the binding energy of Pt and an oxygen-containing intermediate is weakened, and the catalytic activity is improved.
Among the numerous PtM alloy catalysts, ptCo is a relatively promising alloy catalyst. However, the existing PtCo needs to elute Co in the preparation process, which results in complex process and uncontrollable Co content.
Disclosure of Invention
The application provides a platinum-cobalt alloy catalyst and a preparation method thereof, which can avoid elution operation in the preparation process.
In a first aspect, an embodiment of the present application provides a method for preparing a platinum cobalt alloy catalyst, where the method includes:
obtaining a Pt/C raw material catalyst loaded with Pt;
depositing a Co precursor and Pt colloid to a Pt/C raw material catalyst loaded with Pt under an alkaline condition to obtain an intermediate;
and carrying out heat treatment on the intermediate to obtain the platinum-cobalt alloy catalyst.
In the implementation process, the Co precursor and the Pt colloid are coprecipitated to the Pt/C raw material catalyst loaded with Pt under the alkaline condition, in the coprecipitation process, co ions are faster than the Pt colloid in the alkaline condition, so that Co is closer to the inner side and Pt is closer to the outer side after the precipitation is finished, the kinetic energy barrier of ordered rearrangement of atoms in the solid phase is overcome through heat treatment, and the platinum-rich laminated catalyst with higher alloying degree is formed, so that subsequent elution operation is avoided, the preparation flow is shortened, and the Co content is controllable. Meanwhile, as the Pt/C raw material catalyst is loaded with Pt, the Pt can be used as a nucleation point, and Co and Pt can be preferentially deposited on a Pt core of the Pt/C raw material catalyst in the deposition process, so that the particle size is controlled.
As an alternative implementation mode, in the Pt/C raw material catalyst loaded with Pt, the loading amount of Pt is 5% -20% by mass.
In the implementation process, the loading of Pt is controlled so that sufficient nucleation sites are formed on the Pt/C raw material catalyst, and meanwhile, the amount of Pt which is deposited later as a shell is not influenced, so that Co is not easy to remove.
As an alternative embodiment, the pH of the Pt colloid is 10-13.
In the process of the embodiment, the Pt colloid is made to be alkaline, so that alkaline conditions required by Co deposition can be derived from the Pt colloid, and in the preparation process, the Co-deposition can be realized by dripping and mixing the Pt colloid, so that the Co-deposition and the Co-deposition are realized at a proper speed, and a structure that Co is close to the inner side and Pt is close to the outer side is formed.
As an alternative embodiment, the Pt colloid has a particle size of less than 2nm.
In the implementation process, controlling the particle size of the Pt colloid is beneficial to forming a denser shell layer later.
As an alternative embodiment, the molar ratio of Pt and Co in the intermediate is (3-5): 1.
in the implementation process, controlling the mole ratio of Pt and Co on the intermediate is beneficial to improving the alloying degree of Co.
As an alternative embodiment, depositing a Co precursor and Pt colloid under alkaline conditions to a Pt/C feedstock catalyst loaded with Pt, resulting in an intermediate comprising:
dispersing a Co precursor and a Pt/C raw material catalyst loaded with Pt in a solvent to obtain a dispersion liquid;
and (3) dropwise adding alkaline Pt colloid into the dispersion liquid to realize the deposition of the Co precursor and the Pt colloid on the Pt/C raw material catalyst loaded with Pt, so as to obtain an intermediate.
In the implementation process, the Co-deposition is realized by adopting a mode of dropwise adding and mixing Pt colloid, so that the deposition of the Pt colloid and the Pt colloid at a proper speed is realized, and a structure that Co is close to the inner side and Pt is close to the outer side is formed.
As an alternative implementation, the dropping speed of the Pt colloid is 5-10 ml/min.
In the implementation process, the deposition speed is controlled by controlling the dropping speed of the Pt colloid, so that a structure that Co is close to the inner side and Pt is close to the outer side is formed.
As an alternative embodiment, the temperature of the heat treatment is 600-850 ℃; and/or
The atmosphere of the heat treatment is a reducing atmosphere; and/or
The ratio of the reducing gas in the reducing atmosphere is 1/21-1/4; and/or
The reducing atmosphere is a mixture of hydrogen and nitrogen.
In the implementation process, the temperature of the heat treatment process and the ratio of the reducing gas in the reducing atmosphere are controlled, so that the alloying degree is improved.
As an alternative embodiment, the preparation method of the Pt/C raw material catalyst loaded with Pt includes a microwave method and an impregnation method.
As an alternative embodiment, obtaining a Pt/C feedstock catalyst loaded with Pt includes:
mixing a carbon carrier and a Pt precursor in a solvent, and then carrying out solid-liquid separation to obtain powder;
and (3) carrying out reduction treatment on the powder to obtain the Pt/C raw material catalyst loaded with Pt.
As an alternative embodiment, the carbon support comprises carbon black; and/or
The Pt precursor comprises at least one of chloroplatinic acid, platinum tetrachloride and platinum acetylacetonate; and/or
The solid-liquid separation mode is freeze-drying; and/or
The temperature of the reduction treatment is 100-200 ℃; and/or
The reduction treatment time is 2-4 hours.
In the implementation process, the higher the reduction temperature is, the larger the generated Pt particle size is, the larger the Pt particle size is, the fewer sites are provided for PtCo deposition in the later period, the larger the synthesized PtCo particle size is, and the performance of the catalyst is finally influenced; conversely, the lower the reduction temperature, the more sites are provided for PtCo deposition in the later stage, so that more sites are formed and Co deposition is not performed, and the final synthesized catalyst is loaded with more Pt particles and partial PtCo alloy on a carrier, and can influence the overall performance of the catalyst. By controlling the reduction temperature, the deposition sites are controlled in a suitable range, which is advantageous for the performance of the final catalyst.
As an alternative embodiment, the preparation method of the Pt colloid includes:
alcohol and Pt precursor are mixed in alkali solution and then reduced by microwave to obtain Pt colloid.
As an alternative embodiment, the mass ratio of the alcohol, pt precursor and alkali solution is: (100-150): (0.75-1): (0.5-0.7); and/or
The alcohol comprises at least one of ethylene glycol, glycerol and methanol; and/or
The Pt precursor comprises at least one of chloroplatinic acid, platinum tetrachloride and platinum acetylacetonate; and/or
The alkali solution comprises NaOH solution and Na solution 2 CO 3 At least one of a solution and a KOH solution; and/or
The power of microwave reduction is 800-3000W; and/or
The microwave reduction time is 0.5-10 min.
In a second aspect, an embodiment of the present application provides a platinum-cobalt alloy catalyst, which is prepared by using the preparation method of the platinum-cobalt alloy catalyst provided in the first aspect.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a flow chart of a method provided by an embodiment of the present application;
FIG. 2 is a transmission electron microscope FIG. 1 of a platinum cobalt alloy catalyst according to example 3 of the present application;
FIG. 3 is a transmission electron microscope FIG. 2 of the platinum cobalt alloy catalyst provided in example 3 of the present application;
FIG. 4 is an XRD pattern of a platinum cobalt alloy catalyst according to example 3 of the present application;
FIG. 5 is an XRD pattern of a platinum cobalt alloy catalyst according to comparative example 1 of the present application;
fig. 6 is an XRD pattern of the platinum cobalt alloy catalyst provided in comparative example 2 of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.
Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; accordingly, the description of a range should be considered to have specifically disclosed all possible sub-ranges as well as single numerical values within that range. For example, it should be considered that a description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, wherever the range applies. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.
In the present application, unless otherwise specified, terms such as "upper" and "lower" are used specifically to refer to the orientation of the drawing in the figures. In addition, in the description of the present specification, the terms "include", "comprising" and the like mean "including but not limited to". Relational terms such as "first" and "second", and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Herein, "and/or" describing an association relationship of an association object means that there may be three relationships, for example, a and/or B, may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. Herein, "at least one" means one or more, and "a plurality" means two or more. "at least one", "at least one" or the like refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.
PtCo is an alloy catalyst with relatively good development prospect. However, the existing PtCo needs to elute Co in the preparation process, which results in complex process and uncontrollable Co content.
The inventor aims to solve the problems that the preparation of PtCo is complex and the Co content is uncontrollable at present. And a Co precursor and Pt colloid are deposited on a Pt/C raw material catalyst loaded with Pt by adopting a coprecipitation method under an alkaline condition, then a dynamic energy barrier of ordered rearrangement of atoms in a solid phase is overcome by adopting heat treatment, so that a platinum-rich alloy catalyst with higher alloying degree is formed, elution is not needed in the preparation process, and the problems of complex preparation of PtCo and uncontrollable Co content at present are solved.
Referring to fig. 1, an embodiment of the present application provides a method for preparing a platinum cobalt alloy catalyst, including:
s1, obtaining the Pt/C raw material catalyst loaded with Pt.
The Pt/C raw material catalyst loaded with Pt can be obtained by a commercially available and prepared method, and the preparation method of the Pt/C raw material catalyst loaded with Pt includes a microwave method and an impregnation method.
The following is a specific explanation of the impregnation method: mixing a carbon carrier and a Pt precursor in a solvent, and then carrying out solid-liquid separation to obtain powder; and (3) carrying out reduction treatment on the powder to obtain the Pt/C raw material catalyst loaded with Pt.
Among these, the carbon supports include carbon blacks such as the high ratio carbon blacks of EC300J, EC600J, BP 2000. The Pt precursor includes at least one of chloroplatinic acid, platinum tetrachloride, and platinum acetylacetonate. Ball milling is generally used during mixing so as to be more uniform, and the rotational speed of the ball milling can be 500-800 rpm and the duration of the ball milling can be 2-4 hours. The solid-liquid separation mode is freeze-drying, and compared with the vacuum drying mode, the freeze-drying mode can avoid the phenomenon that Pt precursors are separated out along with evaporation of water in a material phase, so that the Pt particle size distribution on a carrier is uneven; illustratively, the lyophilization process includes: and (3) quickly transferring the mixed materials into a glass surface dish for quick pre-freezing, and then transferring the pre-frozen materials into a freeze dryer for freeze drying, wherein the pre-freezing mode can be low-temperature refrigerator pre-freezing, dry ice pre-freezing or liquid nitrogen pre-freezing and the like. The temperature of the reduction treatment is 100-200 ℃; the reduction treatment time is 2-4 hours, the reduction atmosphere is a mixed gas of nitrogen and hydrogen, the volume ratio of the hydrogen to the nitrogen in the mixed gas is 10/200-100/300, the higher the reduction temperature is, the higher the hydrogen concentration is, the larger the generated Pt particle size is, the larger the Pt particles are, the fewer sites provided for PtCo deposition are at the later stage, the larger the synthesized PtCo particle size is, and the performance of the catalyst is finally influenced; conversely, the lower the reduction temperature, the lower the hydrogen concentration, the more sites are provided for PtCo deposition in the later stage, so that more sites are provided for Co deposition, the Co deposition is avoided, and the final synthesized catalyst is loaded with more Pt particles and partial PtCo alloy on a carrier, and can influence the overall performance of the catalyst. By controlling the reduction temperature, the deposition sites are controlled in a suitable range, which is advantageous for the performance of the final catalyst.
In some embodiments, the Pt loading is 5% -20% by mass of the Pt/C feedstock catalyst loaded with Pt. The control of the Pt loading can enable the Pt/C raw material catalyst to have sufficient nucleation sites, and meanwhile, the amount of Pt which is deposited later as a shell is not affected, so that Co is not easy to remove.
S2, depositing a Co precursor and Pt colloid to a Pt/C raw material catalyst loaded with Pt under an alkaline condition to obtain an intermediate.
The Pt colloid may be obtained commercially or prepared, and in some embodiments, the pH of the Pt colloid is 10-13. The Pt colloid is made to be alkaline, so that alkaline conditions required by Co deposition come from the Pt colloid, and in the preparation process, the Co-deposition can be realized by adopting a mode of dropwise adding and mixing the Pt colloid, so that the deposition of the Pt colloid and the Pt colloid at a proper speed is realized, and the formation of a structure that Co is close to the inner side and Pt is close to the outer side is facilitated. The particle size of the Pt colloid is less than 2nm. Controlling the particle size of the Pt colloid facilitates the subsequent formation of a denser shell.
The Pt colloid described above was obtained in the manner of preparation as follows for illustration: the preparation method of the Pt colloid comprises the following steps: alcohol and Pt precursor are mixed in alkali solution and then reduced by microwave to obtain Pt colloid.
Wherein, the mass ratio of the alcohol, the Pt precursor and the alkali solution is as follows: (100-150): (0.75-1): (0.5-0.7); the alcohol comprises at least one of ethylene glycol, glycerol and methanol; the Pt precursor comprises at least one of chloroplatinic acid, platinum tetrachloride and platinum acetylacetonate; the alkali solution comprises NaOH solution and Na solution 2 CO 3 At least one of a solution and a KOH solution; the power of microwave reduction is 800-3000W; the microwave reduction time is 0.5-10 min.
In some embodiments, depositing a Co precursor and a Pt colloid to a Pt/C feedstock catalyst loaded with Pt under alkaline conditions, resulting in an intermediate comprising: s2.1, dispersing a Co precursor and a Pt/C raw material catalyst loaded with Pt in a solvent to obtain a dispersion liquid; s2.2, dropwise adding alkaline Pt colloid into the dispersion liquid to realize the deposition of the Co precursor and the Pt colloid on the Pt/C raw material catalyst loaded with Pt, so as to obtain an intermediate. The Co-deposition is realized by adopting a mode of dropwise adding and mixing Pt colloid, so that the two are precipitated at a proper speed, and a structure that Co is close to the inner side and Pt is close to the outer side is formed.
Specifically, in this embodiment, the Pt/C raw material catalyst loaded with Pt is dispersed in an aqueous solution, and a required Co precursor is added, so that the emulsification and dispersion are uniform, and the emulsification duration can be 30-120 min; after emulsification is completed, placing the mixture in a water bath, magnetically stirring the mixture at a magnetic stirring speed of 200-500 rpm, slowly dripping Pt colloid, and stirring the mixture for 4-10 hours after all dripping is completed; and separating filtrate, cleaning, and vacuum drying at 80 ℃ for 8-10h to obtain an intermediate.
Further, the dropping speed of the Pt colloid is 5-10 ml/min. By controlling the dropping speed of the Pt colloid, the deposition speed is controlled, and a structure that Co is close to the inner side and Pt is close to the outer side is formed.
In some embodiments, the molar ratio of Pt to Co in the intermediate is (3-5): 1. controlling the mole ratio of Pt and Co on the intermediate is beneficial to improving the degree of alloying of Co.
S3, performing heat treatment on the intermediate to obtain the platinum-cobalt alloy catalyst.
Specifically, in this embodiment, the intermediate is loaded into a porcelain boat, and N is introduced before reduction in the tube furnace temperature zone 2 Displacing for 20-60min to remove air, and maintaining at 300-400deg.C for 1-3 hr under the atmosphere of H 2 /N 2 :10/200-100/300 to provide a reducing environment for the heat treatment. After N 2 In the atmosphere, the temperature is raised to 600-850 ℃ at a temperature rising rate of 2-15 ℃ so as to prevent the growth of alloy particles, and finally H is introduced 2 : preserving heat for 2-4h at 5-20ml/min to form a compact platinum-rich structure, and naturally cooling to room temperature.
In some embodiments, the temperature of the heat treatment is 600-850 ℃; the atmosphere of the heat treatment is a reducing atmosphere; the ratio of the reducing gas in the reducing atmosphere is 1/21-1/4; the reducing atmosphere is a mixture of hydrogen and nitrogen. The temperature of the heat treatment process and the ratio of the reducing gas in the reducing atmosphere are controlled, so that the alloying degree is improved.
Based on the same inventive concept, the embodiment of the application also provides a catalyst, which is prepared by adopting the preparation method of the catalyst.
The catalyst is prepared based on the method, specific steps of the method can refer to the embodiment, and as the catalyst adopts part or all of the technical schemes of the embodiment, the catalyst has at least all of the beneficial effects brought by the technical schemes of the embodiment, and the detailed description is omitted.
The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. The experimental procedures, which are not specified in the following examples, are generally determined according to national standards. If the corresponding national standard does not exist, the method is carried out according to the general international standard, the conventional condition or the condition recommended by the manufacturer.
Examples 1 to 6
A method for preparing a platinum cobalt alloy catalyst, comprising the following steps:
one-step impregnation method for synthesizing Pt/C catalyst with low Pt loading
(1) Placing 4 parts of carbon EC600, 1 part of chloroplatinic acid solution, 20 parts of aqueous solution and 300 parts of ball-milling beads in a ball-milling tank;
(2) Ball milling for 2 hours at 600 rpm;
(3) Rapidly transferring the materials in the step (2) into a glass surface dish, and rapidly pre-freezing in a low-temperature refrigerator at-45 ℃;
(4) Transferring the pre-frozen material in the step (3) to a freeze dryer for freeze drying;
(5) Separating ball-milling beads, transferring the freeze-dried powder to a porcelain boat, and carrying out reduction treatment under a tube furnace;
(6) And after the reduction is finished, taking out the porcelain boat, wherein the obtained product is a Pt/C catalyst with 10 percent of loading.
(II) Pt colloid Synthesis
(1) Uniformly mixing 600 parts of ethylene glycol, 3 parts of chloroplatinic acid solution and 15 parts of NaOH solution by ultrasonic waves;
(2) 1500W microwave for 2min for standby;
(III) PtCo Synthesis
(1) Dispersing the Pt/C catalyst with the Pt loading of 10% synthesized in the step (I) in an aqueous solution, adding 0.5 part of cobalt nitrate precursor, emulsifying and dispersing for 40min;
(2) Placing the (1) into a water bath, magnetically stirring at 300rpm, dripping the synthesized Pt colloid of the (two) at a speed of 5ml/min, and stirring for 5 hours after all dripping is finished;
(3) Separating the filtrate in the step (2), cleaning, and vacuum drying at 80 ℃ for 8-10h;
(4) Filling the ceramic boat in the step (3), introducing N before reduction in a tube furnace temperature zone 2 Replacing for 60min, and maintaining the temperature at 300 ℃ for 2H under the atmosphere of H 2 /N 2 ：20/300ml。N 2 Heating to 750 ℃ at a temperature rising rate of 5 ℃ under the atmosphere, and introducing H 2 :20ml/min, and preserving the heat for 3h. Naturally cooling to room temperature.
(5) After the heat treatment is finished, N is introduced 2 1H, H in the replacement tube 2 Sampling after the temperature is reduced to room temperature to obtain the Pt rich layer Pt 3 Co alloy catalyst.
The parameter control in each embodiment is shown in the following table:
comparative example 1
A method for preparing a platinum cobalt alloy catalyst, comprising the following steps:
(1) 64.3mg of cobalt acetylacetonate was added to a 50ml beaker, 10ml of ethanol and 5ml of deionized water were added, and the mixture was sonicated for about 10 minutes. 80mg of 20% Pt@C platinum carbon catalyst and 5ml of deionized water were added and dispersed ultrasonically for about 30 minutes. The prepared pasty mixture is magnetically stirred for 3 hours at normal temperature.
(2) Transferring the beaker onto a constant temperature heating table, heating at a constant temperature of 50 ℃ and magnetically stirring until the mixture is evaporated to dryness to obtain a uniformly dispersed platinum carbon catalyst-cobalt precursor mixture. The mixture was placed in a forced air drying oven and dried at 60℃for 8 hours. After the mixture was ground, it was transferred to a tube furnace for annealing at 600℃for 4 hours under an atmosphere of H2/Ar with a mass fraction of hydrogen of 5%. A fuel cell PtCo catalyst was obtained.
Comparative example 2
A method for preparing a platinum cobalt alloy catalyst, comprising the following steps:
mixing 4mL of 0.1mol/L aqueous cobalt nitrate solution and 4mL of 0.1mol/L aqueous citric acid monohydrate solution, and stirring to form sol; adding 0.57g of platinum-carbon catalyst with 40% platinum loading into the sol system, stirring, ultrasonically dispersing, and then adjusting pH=8 by ammonia water; heating in a metal bath at 60 ℃ to form a gel; transferring the gel into a tube furnace, preserving heat for 1 hour at 500 ℃ in a nitrogen atmosphere, and naturally cooling to room temperature to obtain black powder which is the platinum-cobalt alloy catalyst.
XRD tests were performed on the catalysts provided in examples 1 to 10 and comparative examples 1 to 2, and since the results of each example have similarities, the results of example 3 alone are used for illustration, and fig. 4 to 6 are obtained, from which it is possible to prepare a platinum cobalt alloy catalyst using the method provided in the example of the present application, without a Co elemental phase after heat treatment, without a pickling operation for removing Co, while the platinum cobalt alloy catalyst prepared using the method provided in comparative examples 1 and 2, with a Co elemental phase after heat treatment, requires a pickling operation.
The platinum cobalt alloy catalysts provided in examples 1 to 10 were subjected to an average particle diameter test and ORR activity test, and the results are shown in the following table:
as can be seen from the above table, the comparison of examples 1 to 6 shows that the Pt/C as nucleation sites has a better ORR activity for the synthesized catalyst when the Pt loading is 5% -20%. Also, when the Pt loading is less than 5%, the grain size of the formed alloy is large, and the inventors analyzed that the cause thereof may be caused by too few nucleation sites. As can be seen from the comparison of examples 7 to 10, the synthetic catalyst has a good ORR activity when the Pt colloid dropping rate is 5-10 ml/min during the co-deposition process. The inventor analyzes that the reason may be that when the dropping rate of the Pt colloid is less than 5ml/min, part of the Pt colloid is settled into Pt particles preferentially, the Pt layer on the outer alloy layer is not compact enough, and Co is easy to dissolve out; while when the Pt colloid dropping rate is more than 10ml/min, co is accelerated 2+ Is not easy to grow along the Pt nucleation sites; the Pt-rich structure with Co inside and Pt (colloidal deposition) outside is not easily formed, resulting in poor ORR activity of the synthesized catalyst.
The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. A method for preparing a platinum cobalt alloy catalyst, the method comprising:
obtaining a Pt/C raw material catalyst loaded with Pt;
depositing a Co precursor and Pt colloid to the Pt/C raw material catalyst loaded with Pt under an alkaline condition to obtain an intermediate;
carrying out heat treatment on the intermediate to obtain a platinum-cobalt alloy catalyst;
wherein the depositing a Co precursor and a Pt colloid to the Pt/C raw material catalyst loaded with Pt under alkaline conditions to obtain an intermediate comprises:
dispersing a Co precursor and a Pt/C raw material catalyst loaded with Pt in a solvent to obtain a dispersion liquid;
dropwise adding alkaline Pt colloid into the dispersion liquid to realize the deposition of a Co precursor and the Pt colloid on the Pt/C raw material catalyst loaded with Pt, so as to obtain an intermediate;
the pH value of the Pt colloid is 10-13; the dropping speed of the Pt colloid is 5-10 ml/min.
2. The method for producing a platinum-cobalt alloy catalyst according to claim 1, wherein the Pt-supported Pt/C raw material catalyst has a Pt-supported amount of 5% to 20% by mass.
3. The method for preparing a platinum cobalt alloy catalyst according to claim 1, wherein the particle size of the Pt colloid is less than 2nm.
4. The method for preparing a platinum cobalt alloy catalyst according to claim 1, wherein the molar ratio of Pt to Co in the intermediate is (3-5): 1.
5. the method for preparing a platinum-cobalt alloy catalyst according to claim 1, wherein the temperature of the heat treatment is 600-850 ℃.
6. The method for producing a platinum cobalt alloy catalyst according to claim 1, wherein the heat-treated atmosphere is a reducing atmosphere; and/or
The ratio of the reducing gas in the reducing atmosphere is 1/21-1/4; and/or
The reducing atmosphere is a mixed gas of hydrogen and nitrogen.
7. A platinum cobalt alloy catalyst, characterized in that it is produced by the production method of a platinum cobalt alloy catalyst according to any one of claims 1 to 6.
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