CN116364963A - Platinum carbon catalyst and its preparation method and fuel cell - Google Patents

Abstract

The invention relates to a platinum-carbon catalyst, a preparation method thereof and a fuel cell. The preparation method of the platinum carbon catalyst comprises the following steps: activating the carbon carrier; mixing a sulfite complex of platinum with the activated carbon carrier and an oxidant for oxidation precipitation reaction under acidic and ultrasonic stirring conditions to obtain an unmodified platinum carbon sample; modifying a modifier on the surface of an unmodified platinum carbon sample to prepare a platinum carbon catalyst, wherein the modifier comprises any one or more of melamine and melamine polymers. The preparation method of the platinum-carbon catalyst can improve the platinum loading capacity and the electrocatalytic oxygen reduction activity.

Description

Platinum carbon catalyst and its preparation method and fuel cell

technical field

The invention relates to the field of fuel cells, in particular to a platinum-carbon catalyst, a preparation method thereof, and a fuel cell.

Background technique

The proton exchange membrane fuel cell is a high-efficiency power generation device that directly and continuously converts the chemical energy in the hydrogen oxidation reaction into electrical energy at around room temperature. It is green and clean and has broad development prospects.

The catalyzer of the proton exchange membrane fuel cell widely used at present is Pt/C, and it has following problems: activity is low, is reflected in the about 0.2A/mg _Pt of mass specific activity (MSA, 0.9V); Platinum loading is low, is reflected in Pt Most of the loads are below 20%.

Contents of the invention

Based on this, it is necessary to provide a preparation method of a platinum-carbon catalyst, which can increase the platinum loading and activity of the platinum-carbon catalyst.

In addition, it is also necessary to provide a platinum carbon catalyst prepared by the above method and a fuel cell comprising the platinum carbon catalyst.

A preparation method of platinum carbon catalyst, comprising the steps of:

Activate the carbon carrier;

Under acidic and ultrasonic stirring conditions, the platinum sulfite complex is mixed with the activated carbon carrier and oxidant to carry out oxidation precipitation reaction to prepare an unmodified platinum carbon sample; and

A modifier is modified on the surface of the unmodified platinum-carbon sample to prepare a platinum-carbon catalyst, and the modifier includes any one or more of melamine and melamine polymer.

In some of these embodiments, the step of modifying the modifier on the surface of the unmodified platinum carbon sample comprises: immersing the unmodified platinum carbon sample in a solution containing the modifier, In the modifier solution, the concentration of the modifier is 0.5mmol/L-20mmol/L.

In some of the embodiments, the melamine polymer includes any one or a combination of melamine-formaldehyde resin and sulfonated melamine-formaldehyde resin.

In some of these embodiments, the ultrasonic power is 100W-250W.

In some of these embodiments, the pH of the acidic condition is 2-3.

In some embodiments, the mass ratio of the platinum sulfite complex to the activated carbon support is 0.5:1˜20:1.

In some of the embodiments, the molar ratio of the platinum sulfite complex to the oxidizing agent is 1:30˜1:200.

In some of these embodiments, under acidic and ultrasonic stirring conditions, the step of mixing platinum sulfite complexes with activated carbon supports and oxidants to carry out oxidation precipitation reaction includes: under acidic conditions, first The platinum sulfite complex is dissolved, then mixed with the activated carbon carrier, stirred ultrasonically for 0.5h-3h, then added hydrogen peroxide for oxidation precipitation reaction, stirred ultrasonically for 0.5h-3h, and added alkaline reagent during the reaction Maintain the pH at 2-3, then heat and reflux for 0.5h to 3h; or,

Under acidic conditions, first dissolve the platinum sulfite complex, then add hydrogen peroxide for oxidation precipitation reaction, ultrasonically stir for 0.5h to 3h, add alkaline reagents during the reaction to maintain the pH at 2-3, after the reaction Then mix with the activated carbon carrier, stir ultrasonically for 0.5h-3h, and then heat and reflux for 0.5h-3h.

In some of the embodiments, the alkaline reagent includes any one or more of NaOH, KOH, Na ₂ CO ₃ and NH ₃ H ₂ O.

In some of these embodiments, the activated carbon support is mixed with the platinum sulfite complex and the oxidizing agent in the form of a suspension, and the solvent of the suspension includes water and/or alcohol solvents .

In some of these embodiments, the preparation step of the platinum sulfite complex includes: firstly dispersing the platinum salt precursor in water, then adding excess saturated NaHSO ₃ solution until precipitation occurs, adjusting the pH to 6-10, and preparing The platinum sulfite complex;

Wherein, the platinum salt precursor includes any one or more of H ₂ PtCl ₆ , K ₂ PtCl ₆ , K ₂ PtI ₆ , PtCl ₄ , K ₂ PtCl ₄ , PtCl ₂ and H ₂ Pt(OH) ₆ .

In some embodiments, the step of activating the carbon support includes: performing heat treatment on the carbon support in a carbon dioxide atmosphere, the temperature of the heat treatment is 300°C-900°C, and the time is 1h-12h; or,

heat-treating the carbon carrier in an ammonia atmosphere, the temperature of the heat treatment is 300°C-900°C, and the time is 1h-12h; or,

The carbon support is heated to reflux in nitric acid solution for 1h-12h.

In some of these embodiments, the carbon support includes any one or a combination of XC-72R, KB EC300, KB EC600, carbon nanotubes, graphene and Fe-N-C.

In some of the embodiments, the loading amount of platinum in the platinum-carbon catalyst is 15%-70%.

A platinum-carbon catalyst, prepared by the above-mentioned preparation method of the platinum-carbon catalyst.

A fuel cell, comprising the above-mentioned platinum-carbon catalyst.

Traditional platinum-carbon catalysts have the problems of low activity and low platinum loading. The inventors found in experiments that the intrinsic activity of the catalyst can be improved by increasing the platinum loading. However, when the platinum loading is high, the platinum particle size is large and easily Agglomeration leads to a decrease in mass specific activity. Based on this, the present invention provides a method for preparing a platinum-carbon catalyst. In the above-mentioned method, the carbon support is first activated to improve its surface functional groups, which is beneficial to improving the loading effect of the carbon support and platinum. The preparation of platinum colloids by oxidation precipitation is beneficial to reduce the size of platinum colloids, and adjust the pH to be acidic, and use electrostatic adsorption to enhance the interaction between the activated carbon carrier and platinum colloids. In addition, through ultrasonic treatment, a On the one hand, it improves the dispersion of platinum colloidal loading on the carbon carrier after activation treatment, and improves the dispersibility; Platinum has good dispersion and is not easy to agglomerate under high loading. Finally, it was modified with melamine or melamine polymer modifier to weaken the interaction between nano-platinum particles and oxygen-containing intermediates during the oxygen reduction process, so that the platinum-on-carbon catalyst has higher activity at high platinum loading. Experiments have proved that the mass specific activity of the platinum-carbon catalyst prepared by the above method can reach 2 to 3 times that of commercial catalysts, and the platinum loading can reach up to 70%.

Description of drawings

Fig. 1 is the process flow chart of the preparation method of the platinum carbon catalyst of an embodiment;

FIG. 2 is a TEM image of the platinum-carbon catalyst prepared in Comparative Example 2.

Detailed ways

In order to facilitate the understanding of the present invention, the following will describe the present invention more fully in combination with specific embodiments. Preferred embodiments of the invention are given in the detailed description. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terminology used herein in the description of the present invention is only for the purpose of describing specific embodiments, and is not intended to limit the present invention.

Unless otherwise stated or there is a conflict, the terms or phrases used in the present invention have the following meanings:

In the present invention, "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features.

In the present invention, "and/or" includes any and all combinations of one or more related listed items.

In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, "one or several" refers to any one, any two or any two or more of the listed items. Wherein, "several types" refers to any two or more than two.

In the present invention, the percentage concentration involved refers to the final concentration unless otherwise specified. The final concentration refers to the proportion of the added component in the system after the component is added.

The words "preferably", "more preferably" etc. in the present invention refer to embodiments of the invention which may afford certain advantages, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

When a numerical range is disclosed herein, the said range is considered continuous and includes the minimum and maximum values of the range and every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum of the range is included. Furthermore, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein.

In the present invention, the technical features described in open form include closed technical solutions consisting of the enumerated features, as well as open technical solutions including the enumerated features.

The terms "comprising" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes unlisted steps or units, or optionally further includes For other steps or components inherent in those processes, methods, products, or devices.

Reference in the present disclosure to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The occurrences of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is understood explicitly and implicitly by those skilled in the art that the described embodiments of the invention can be combined with other embodiments.

Traditional platinum-carbon catalysts have the problems of low activity and low platinum loading. The inventors found that the catalyst activity can be improved by increasing the dispersion and platinum loading of the catalyst. However, most of the Pt loadings in Pt/C catalysts reported so far are low. When the loading of platinum is higher than 20%, there is a problem that the platinum particle size is large and easy to agglomerate, resulting in a decrease in activity.

Based on this, the first aspect of the present invention provides a method for preparing a platinum-carbon catalyst, which can increase the activity of the catalyst while increasing the platinum loading.

Please refer to Fig. 1, the preparation method of the platinum carbon catalyst of one embodiment, comprises the steps:

Step S110: Activating the carbon support.

In some embodiments, the carbon support includes any one or a combination of XC-72R, KB EC300, KB EC600, carbon nanotubes, graphene and Fe-N-C. It can be understood that the carbon support is not limited thereto, and can also be a carbon support commonly used in fuel cell catalysts in the field.

It can be understood that the step of activating the carbon support is not particularly limited, and may be a common step in the art. Specifically, three ways of activating the carbon support are provided in this embodiment, but are not limited thereto.

In some embodiments, step S110 includes: heat-treating the carbon carrier in a carbon dioxide atmosphere.

In some of the embodiments, the temperature of the heat treatment is 300°C-900°C, and the time is 1h-12h.

In a specific example, the heat treatment temperature can be, but not limited to, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C , 900°C or any two of these values.

In a specific example, the heat treatment time can be, but not limited to, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any two of these values. .

In a specific example, heat treatment can be performed, but is not limited to, in a tube furnace.

In some other embodiments, step S110 includes: heating the carbon carrier to reflux in a nitric acid solution for 1h-12h.

In some other embodiments, step S110 includes: heat-treating the carbon carrier in an ammonia gas atmosphere at a temperature of 300° C. to 900° C. for 1 h to 12 h.

The nature and quantity of oxygen-containing functional groups on the surface of the carbon support can be improved by activating the carbon support, and the specific surface area and pore structure of the carbon support can be changed at the same time, thereby changing the interaction between the carbon support and Pt and improving the electrochemical performance of the prepared catalyst.

Step S120: first disperse the platinum salt precursor in water, then add excess saturated NaHSO ₃ solution until precipitation occurs, adjust the pH to 6-10, and prepare a platinum sulfite complex.

In some embodiments, the platinum salt precursor includes any one of H ₂ PtCl ₆ , K ₂ PtCl ₆ , K ₂ PtI ₆ , PtCl ₄ , K ₂ PtCl ₄ , PtCl _{2 ,} and H ₂ Pt(OH) ₆ or Several kinds. Platinum sulfite complexes can be prepared from the above platinum salt precursors. The divalent platinum salt precursor directly generates platinum sulfite complex precipitation through the above reaction, and the tetravalent platinum salt precursor is first reduced by NaHSO ₃ to form a precipitate.

In some embodiments, in the step of adjusting the pH to 6-10, the pH is adjusted with a saturated Na ₂ CO ₃ solution. Further, after the step of adjusting the pH to 6-10, a purification step is also included. The purification steps include: standing, filtering, washing and drying.

Optionally, the drying temperature is 90°C-120°C. For example, the drying temperature may be, but not limited to, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or a range consisting of any two of these values.

Optionally, the standing time is 12h.

In some of these embodiments, step S120 includes: dispersing the platinum salt precursor in water, adding saturated NaHSO ₃ solution to dissolve, the pH value is 1-3, then adding excess saturated NaHSO ₃ solution until precipitation occurs, and using saturated Na ₂ CO _3. Adjusting the pH of the solution to 6-10, standing still, filtering, washing and drying to obtain the platinum sulfite complex.

It can be understood that the above only gives a preparation step of a platinum sulfite complex, but is not limited thereto, and other steps commonly used in the art can also be used, as long as the platinum sulfite complex can be obtained.

Step S130: Under acidic and ultrasonic stirring conditions, the platinum sulfite complex is mixed with the activated carbon support and the oxidant to carry out an oxidation precipitation reaction to prepare an unmodified platinum carbon sample.

In some embodiments, the pH of the acidic condition is 2-3.

In some embodiments, the mass ratio of the platinum sulfite complex to the activated carbon support is 0.5:1˜20:1. In a specific example, the mass ratio of the platinum sulfite complex to the activated carbon support can be, but not limited to, 0.5:1, 1:1, 2:1, 5:1, 6:1, 8 :1, 10:1, 12:1, 14:1, 17:1, 20:1 or any two of these values.

In some embodiments, the molar ratio of the platinum sulfite complex to the oxidizing agent is 1:30˜1:200. In a specific example, the molar ratio of the platinum sulfite complex to the oxidant may be, but not limited to, 1:30, 1:40, 1:60, 1:80, 1:100, 1:120, 1: 140, 1:150, 1:160, 1:180, 1:200, or a range of any two of these values.

In some embodiments, the oxidizing agent includes hydrogen peroxide. The mass percentage concentration of hydrogen peroxide is 10%-30%. It can be understood that the oxidizing agent is not limited to hydrogen peroxide, and may also be potassium permanganate and the like. Preferably, the oxidizing agent includes hydrogen peroxide. Using hydrogen peroxide as the oxidizing agent, on the one hand, hydrogen peroxide has strong oxidizing property and can oxidize the sulfite complex of platinum; on the other hand, the product after hydrogen peroxide oxidation is water, and no new impurities will be introduced.

In some embodiments, step S130 includes: under acidic conditions, first dissolving the platinum sulfite complex, then mixing with the activated carbon support, ultrasonically stirring for 0.5h-3h, and then adding hydrogen peroxide to carry out oxidation precipitation reaction , ultrasonically stirred for 0.5h to 3h, adding alkaline reagents during the reaction to maintain the pH at 2-3, and then heated to reflux for 0.5h to 3h.

Specifically, in the step of dissolving the platinum sulfite complex, dilute sulfuric acid is added to adjust the pH to 2-3.

Further, the activated carbon support is mixed in the form of a suspension, and the solvent of the suspension includes water and/or an alcohol solvent. Specifically, disperse the activated carbon carrier into a mixed solution of ethanol-water, or disperse the activated carbon carrier in water, and heat to reflux to obtain a suspension containing the activated carbon carrier. It can be understood that when the solvent of the suspension includes an alcohol solvent, such as ethanol, the ethanol can reduce the prepared platinum oxide colloid to a certain extent and adjust the ratio of zero-valent platinum in the Pt/C catalyst.

Specifically, during the process of ultrasonic stirring, the ultrasonic power is 100W-250W. In a specific example, the ultrasonic power may be, but not limited to, 100W, 120W, 140W, 150W, 160W, 180W, 200W, 220W, 240W, 250W or any two of these values. The ultrasonic stirring time may be, but not limited to, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or a range consisting of any two of these values.

Ultrasonic treatment, on the one hand, improves the dispersion of Pt colloidal particles on the carbon carrier and improves the dispersibility. On the other hand, ultrasonic treatment can increase the loading of platinum on the carbon carrier to a certain extent, making high The lower platinum has good dispersion and is not easy to agglomerate, which is conducive to further improving the activity of the platinum-carbon catalyst. The catalyst with high dispersion and high platinum loading can increase the contact probability between the catalyst active site and Nafion (perfluorosulfonic acid) ionomer on the one hand, improve the utilization rate of Pt, and improve the catalyst activity; on the other hand, it can make the catalyst layer thinner , speed up mass transfer and reduce membrane electrode voltage loss.

Specifically, the alkaline reagent includes any one or a combination of NaOH, KOH, Na ₂ CO ₃ and NH ₃ H ₂ O.

Optionally, the time for heating to reflux may be, but not limited to, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or a range consisting of any two of these values. By heating and reflux treatment, the adsorption effect of platinum on the carbon carrier is further improved, and the loading capacity of platinum is increased.

Further, in some embodiments, step S130 includes: dispersing the platinum sulfite complex in water, adjusting the pH to 2-3 with dilute sulfuric acid solution, dissolving the platinum sulfite complex, and then activating the Mix the treated carbon carrier, add hydrogen peroxide under ultrasonic and stirring conditions for oxidation precipitation reaction, adjust the pH to about 3 with alkaline reagents, stir ultrasonically for 0.5h-3h, then heat and reflux for 0.5h-3h, cool, filter, and wash , and dry to obtain an unmodified platinum carbon sample.

In a specific example, the drying temperature is 90°C-120°C.

In some other embodiments, step S130 includes: under acidic conditions, dissolving the platinum sulfite complex first, then adding hydrogen peroxide for oxidation precipitation reaction, stirring ultrasonically for 0.5h-3h, adding alkaline reagents during the reaction to maintain The pH is 2-3, and after the reaction is completed, it is mixed with the heat-treated carbon carrier, stirred ultrasonically for 0.5h to 3h, and then heated to reflux for 0.5h to 3h.

Experiments have shown that adding a carbon support during the oxidative precipitation of the platinum sulfite complex and an oxidant, or adding a carbon support after the oxidation precipitation is completed, can achieve high loading of platinum on the carbon support. First oxidize and precipitate and then add carbon support, the nano-Pt particles have grown to 2-3 nanometers, and will not enter the micropores of the carbon support, but can be more exposed on the surface, and can absorb more modification when modifying the modifier. sex agent.

In some embodiments, the loading amount of platinum in the unmodified platinum carbon sample is 15%-70%. For example, the loading of platinum in the unmodified platinum carbon sample can be but not limited to 15%, 20%, 25%, 30%, 35%, 40%, 45%, 55%, 60%, 65%, 70% or a range of any two of these values. It can be understood that the loading amount of platinum refers to the percentage of the mass of platinum in the unmodified platinum-carbon sample to the total mass of the unmodified platinum-carbon sample.

Step S140: modifying a modifier on the surface of the unmodified platinum-carbon sample to prepare a platinum-carbon catalyst. The modifier includes any one or more of melamine and melamine polymer.

In some embodiments, the melamine polymer includes any one or more of melamine-formaldehyde resin and sulfonated melamine-formaldehyde resin.

In some embodiments, the step of modifying the modifier on the surface of the unmodified platinum carbon sample comprises: immersing the unmodified platinum carbon sample in a solution containing the modifier for 0.5h to 2h, and in the solution containing the modifier In , the concentration of modifier is 0.5mmol/L～20mmol/L. For example, the concentration of modifier can be but not limited to 0.5mmol/L, 1mmol/L, 2mmol/L, 5mmol/L, 8mmol/L, 10mmol/L, 12mmol/L, 15mmol/L, 18mmol/L, 20mmol /L or a range of any two of these values. In one embodiment, the solvent used in the solution containing the modifying agent includes alcohol solvent and/or water. For example, the solvent is a mixture of isopropanol and water, or the solvent is water.

Further, in the step of immersing the unmodified platinum carbon sample in a solution containing a modifier, ultrasonic stirring was also carried out. Specifically, the power of the ultrasonic stirring is 100W-250W, and the time is 0.5h-2h.

In some embodiments, step S140 includes: dispersing the unmodified platinum-carbon sample into a solution containing melamine and/or melamine polymer, ultrasonically stirring for 0.5h-2h, filtering, washing, and drying to obtain a platinum-carbon catalyst.

By modifying the surface of platinum-carbon samples with melamine or melamine polymer, the interaction between nano-Pt particles and oxygen-containing intermediates during the oxygen reduction process of platinum-carbon catalysts is weakened, and the catalyst activity is improved.

The preparation method of the above-mentioned platinum-carbon catalyst has at least the following advantages:

(1) In the preparation method of the above-mentioned platinum-carbon catalyst, the carbon support is first activated to improve its surface functional groups, which is conducive to improving the loading effect between the carbon support and platinum and increasing the platinum loading capacity. Prepare nano-platinum colloids by oxidation precipitation, adjust the pH to be acidic, and use electrostatic adsorption to enhance the interaction between the activated carbon carrier and platinum colloids. The dispersion on the carrier improves the dispersibility. On the other hand, the loading capacity of platinum on the carbon carrier can also be increased by ultrasonic treatment, so that the dispersion of platinum under high loading capacity is good and it is not easy to agglomerate. Finally, it was modified with melamine or melamine modifier to weaken the interaction between nano-platinum particles and oxygen-containing intermediates during the oxygen reduction process, so that the platinum-on-carbon catalyst has higher activity at high platinum loading. Experiments have proved that the mass specific activity of the platinum-carbon catalyst prepared by the above method can reach 2 to 3 times that of commercial catalysts.

(2) The stability of traditional platinum-carbon catalysts is relatively poor, and problems such as Pt particle dissolution and agglomeration and carbon carrier corrosion are prone to occur during the reaction process, resulting in a decrease in catalyst activity and limiting the commercial application of fuel cells. Platinum carbon catalysts can improve stability to a certain extent.

(3) The preparation method of the above-mentioned platinum-carbon catalyst has a simple process and is easy to scale up production.

The second aspect of the present invention also provides a platinum-carbon catalyst, which is prepared by the above-mentioned preparation method of the platinum-carbon catalyst.

The third aspect of the present invention also provides a fuel cell, including the above-mentioned platinum-carbon catalyst.

In order to make the purpose and advantages of the present invention clearer, the platinum-carbon catalyst of the present invention and its effects will be further described in detail below in conjunction with specific examples. It should be understood that the specific examples described here are only used to explain the present invention and are not intended to used to limit the present invention. The following examples do not include other components except unavoidable impurities unless otherwise specified. The drugs and instruments used in the examples are all routine choices in the art unless otherwise specified. The experimental methods for which specific conditions are not indicated in the examples are implemented according to conventional conditions, such as conditions described in literature, books or methods recommended by the manufacturer.

Example 1

This embodiment provides a method for preparing a platinum sulfite complex, comprising the following steps:

Disperse 2g _{of K2PtCl6} into deionized water, add an appropriate amount of saturated _NaHSO3 solution until _{K2PtCl6 is} completely dissolved. Then, excess saturated NaHSO ₃ solution was added to the above solution until a large amount of white precipitates were produced. The pH of the mixture was adjusted to 6-8 with saturated Na ₂ CO ₃ solution, stirred and left to stand overnight. Then filter, wash and dry to obtain platinum sulfite complexes.

Example 2

The present embodiment provides a kind of preparation method of platinum carbon catalyst, comprises the following steps:

(1) The carbon support KB EC300 was heat-treated at 500° C. for 2 hours in a carbon dioxide atmosphere to obtain the heat-treated carbon support KB EC300.

(2) Disperse 0.2 g of heat-treated carbon carrier KB EC300 into a mixed solution of ethanol-water to obtain a mixture A. Disperse 0.5 g of the platinum sulfite complex prepared in Example 1 into deionized water, adjust the pH with dilute sulfuric acid to completely dissolve the platinum sulfite complex, and obtain solution B. Solution B was added to mixture A and stirred for 0.5 h under the condition of ultrasonic power of 150 W to obtain mixture C. Then, 10 mL of diluted hydrogen peroxide solution (15% by mass H ₂ O ₂ ) was slowly added dropwise to mixture C, and the pH of the mixture was adjusted to be stable at about 3 with dilute NaOH solution, and stirred for 1 h under the condition of ultrasonic power of 150 W. Then heated to reflux for 1h. After the solution was cooled, it was filtered, washed and dried to obtain an unmodified platinum carbon sample.

(3) Disperse the obtained unmodified platinum carbon sample into a 10mmol/L melamine aqueous solution, stir for 0.5h under the condition of ultrasonic power of 240W, filter, wash, and dry to obtain a melamine-modified Pt/C catalyst.

Example 3

The present embodiment provides a kind of preparation method of platinum carbon catalyst, comprises the following steps:

(1) The carbon support KB EC300 was heat-treated at 500° C. for 2 hours in a carbon dioxide atmosphere to obtain the heat-treated carbon support KB EC300.

(2) Disperse 0.2 g of heat-treated KB EC300 in deionized water, heat to reflux, and obtain mixture A. 1 g of the platinum sulfite complex prepared in Example 1 was dispersed in deionized water, and the pH was adjusted with dilute sulfuric acid to obtain solution B. Solution B was added to mixture A and stirred for 0.5 h under the condition of ultrasonic power of 150 W to obtain mixture C. Then, 30 mL of diluted hydrogen peroxide solution (15% concentration of H ₂ O ₂ ) was slowly added dropwise to mixture C, and the pH of the mixture was adjusted to be stable at about 3 with dilute ammonia solution, and stirred for 1 h under the condition of ultrasonic power of 240 W. Then heated to reflux for 2h. After the solution was cooled, it was filtered, washed, and dried to obtain an unmodified Pt/C sample.

(3) Disperse the unmodified Pt/C sample obtained in the isopropanol-water solution of 0.5mmol/L melamine formaldehyde resin, ultrasonic 0.5h, stir 0.5h, filter, wash, dry, obtain melamine formaldehyde resin modified Pt/C catalyst.

Example 4

The present embodiment provides a platinum carbon catalyst, comprising the steps of:

(1) The carbon support KB EC300 was heat-treated at 500°C for 2h in a carbon dioxide atmosphere.

(2) Disperse 0.1 g of the heat-treated carbon carrier KB EC300 in deionized water, heat to reflux, and obtain mixture A. Disperse 2 g of the platinum sulfite complex prepared in Example 1 into deionized water, adjust the pH with dilute sulfuric acid to completely dissolve the intermediate, and obtain solution B. Solution B was added to mixture A and stirred for 0.5 h under the condition of ultrasonic power of 150 W to obtain mixture C. Then, 32 mL of diluted hydrogen peroxide solution (H ₂ O ₂ mass percent concentration: 15%) was slowly added dropwise to mixture C, and the pH of the mixture was adjusted to be stable at about 3 with diluted NaOH solution, and stirred for 1 h under the condition of ultrasonic power of 150 W. Then heated to reflux for 1h. After the solution was cooled, it was filtered, washed and dried to obtain an unmodified platinum carbon sample.

(3) Disperse the obtained unmodified platinum carbon sample into 10mmol/L melamine aqueous solution, stir for 0.5h under the condition of ultrasonic power of 240W, filter, wash and dry to obtain melamine-modified Pt/C catalyst.

Comparative example 1

Comparative Example 1 provides a platinum-carbon catalyst, which is similar to the preparation process of the platinum-carbon catalyst in Example 2, except that the melamine modification of step (3) is not performed.

Comparative example 2

Comparative Example 2 provides a platinum-carbon catalyst, which is similar to the preparation process of the platinum-carbon catalyst in Example 3, except that the modification of the melamine-formaldehyde resin in step (3) is not performed.

Comparative example 3

Comparative Example 3 provides a platinum-carbon catalyst, which is similar to the preparation process of the platinum-carbon catalyst in Example 2, except that in step (3), 10 mmol/L of melamine solution is replaced with 10 mmol/L of aniline solution.

Comparative example 4

Comparative example 4 provides a kind of platinum carbon catalyst, and the preparation process of the platinum carbon catalyst of embodiment 2 is similar, and difference is, the modification of the melamine formaldehyde resin that does not carry out step (3), and step (2) is different, the Step (2) is as follows:

0.2 g of the heat-treated carbon support KB EC300 was dispersed into a mixed solution of ethanol-water to obtain a mixture A. Disperse 0.5 g of the platinum sulfite complex prepared in Example 1 into deionized water, adjust the pH with dilute sulfuric acid to completely dissolve the platinum sulfite complex, and obtain solution B. Solution B was added to mixture A and stirred for 0.5 h to obtain mixture C. Then, 10 mL of diluted hydrogen peroxide solution (15% H ₂ O ₂ concentration) was slowly added dropwise to the mixture C, and the pH of the mixture was adjusted to be stable at about 3 with dilute NaOH solution, and stirred for 1 h. Then heated to reflux for 1h. After the solution was cooled, it was filtered, washed, and dried to obtain an unmodified Pt/C sample.

Comparative example 5

This comparative example provides a kind of preparation method of unmodified platinum carbon catalyst, and preparation process is as follows:

(1) The carbon support KB EC300 was heat-treated at 600° C. for 2 h in an ammonia atmosphere to obtain the heat-treated carbon support KB EC300.

(2) Disperse 0.3 g of heat-treated carbon carrier KB EC300 into a mixed solution of ethanol-water to obtain a mixture A. Disperse 1 g of the sulfite complex prepared in Example 1 into deionized water, adjust the pH with dilute sulfuric acid to completely dissolve the sulfite complex, and obtain solution B. Solution B was added to mixture A and stirred for 0.5 h under the condition of ultrasonic power of 150 W to obtain mixture C. Then, 20 mL of diluted hydrogen peroxide solution (15% H ₂ O ₂ ) was slowly added dropwise to the mixture C, the pH of the mixture was adjusted to be stable at about 3 with dilute NaOH solution, and the mixture was stirred for 1 h under the condition of ultrasonic power of 240 W. Then heated to reflux for 1h. After the solution is cooled, it is filtered, washed and dried to obtain an unmodified Pt/C catalyst.

Comparative example 6

This comparative example provides a kind of unmodified platinum carbon catalyst, and the preparation process of the platinum carbon catalyst of embodiment 2 is similar, difference is, step (3) is not carried out, and step (2) is different, the step (2) of this comparative example ) is: disperse 0.5 g of the platinum sulfite complex prepared in Example 1 into deionized water, and adjust the pH with dilute sulfuric acid to completely dissolve the platinum sulfite complex to obtain solution A. Stir for 0.5 h under the condition of ultrasonic power of 150W. Then, 10 mL of dilute hydrogen peroxide solution (H ₂ O ₂ mass percent concentration: 15%) was slowly added dropwise to solution A, and the pH of the mixture was adjusted to be stable at about 3 with dilute NaOH solution. Disperse 0.2 g of KBEC300 into deionized water and heat to reflux to obtain mixture B. Add mixture B to solution A, and stir for 1 h under the condition of ultrasonic power of 150 W. Then heated to reflux for 1h. After the solution is cooled, it is filtered, washed and dried to obtain an unmodified platinum-carbon catalyst.

The following is the specific test part:

1. Platinum loading test

Test the platinum loading of the platinum-carbon catalysts prepared by the examples and comparative examples by the ICP-AES method, and obtain the data shown in the following table 1:

The platinum loading of the platinum carbon catalyst of each embodiment of table 1 and comparative example

load capacity Example 2 32% Example 3 48% Example 4 67% Comparative example 1 35% Comparative example 2 52% Comparative example 3 31% Comparative example 4 28% Comparative example 5 47% Comparative example 6 33%

2. Characterization of catalytic activity

Test method: The activity and stability of the prepared Pt/C catalyst were tested in a three-electrode system using a rotating disk electrode. Take a certain amount of Pt/C catalyst and make 1mg/mL slurry (the volume ratio of slurry is water: ethanol: 5% Nafion = 24:75: ₁ ) and apply it on the glassy carbon electrode as the working electrode; ₄ is the reference electrode; the Pt wire is the counter electrode. Carry out cyclic voltammetry scanning in 0.1mol/L perchloric acid solution saturated with nitrogen, scan at 50mV/s until the curve is stable, the scanning range is 0.05-1.1V, and use the hydrogen desorption peak of the cyclic voltammetry curve to characterize Pt/C The electrochemically active area of the catalyst. Carry out the oxygen reduction linear scanning test in the 0.1mol/L perchloric acid solution saturated with oxygen, the scanning speed is 10mV/s, the rotation speed of the rotating disk electrode is 1600r/min, the scanning range is 0.05-1.1V, select 0.9V ( vs RHE (reversible hydrogen electrode)) to calculate the mass specific activity and intrinsic activity of the current density.

The test data of the platinum carbon catalyst prepared in Examples 2 to 4 and Comparative Examples 1 to 6 and the commercial TKK 46.6% Pt/C catalyst are shown in Table 2 below:

Table 2

From the comparison of above Example 2 and Comparative Example 1, Example 3 and Comparative Example 2, it can be seen that the platinum carbon catalyst is modified with melamine or melamine polymer, which can significantly improve the mass specific activity and intrinsic activity of the catalyst, For example, the mass specific activity of Example 2 is 1.3 times that of Comparative Example 1, and the intrinsic activity is 3.8 times that of Comparative Example 1. From the comparison of Example 2, Comparative Example 1 and Comparative Example 3, it can be seen that modifying aniline on the platinum carbon catalyst cannot improve the catalyst activity.

From the comparison of Comparative Example 5 and Comparative Example 1, it can be seen that NH ₃ or CO ₂ heat treatment can achieve the purpose of activating the carbon support, and the activity of the prepared platinum carbon catalyst has no obvious difference.

From the comparison of Comparative Example 6 and Comparative Example 1, it can be seen that the addition of the carbon support before or after the oxidative precipitation of the Pt colloid has no significant effect on the catalyst activity.

From the comparison of above Example 2 and Example 3, Example 4, Comparative Example 1 and Comparative Example 2, it can be seen that when the loading of platinum increases, the electrochemically active area does not significantly decrease, indicating that when the loading of platinum is high , the dispersion of platinum is still good, and there is no obvious phenomenon of agglomeration.

From the comparison of Comparative Example 4 and Comparative Example 1, it can be seen that ultrasound can improve the catalyst loading, platinum particle size and distribution to a certain extent.

3. The TEM image of the platinum-carbon catalyst prepared in Comparative Example 2 is shown in Figure 2, as can be seen from Figure 2, when the platinum loading is 52%, the size of the platinum particles is small, and the dispersion is good, without Visible agglomeration occurs.

4. Stability test

Stability test was carried out on the platinum-carbon catalyst prepared in Example 3, and a certain amount of Pt/C catalyst was taken to form a 1 mg/mL slurry (the volume ratio of the slurry was water: ethanol: 5% Nafion = 24:75:1) and coated with The glassy carbon electrode is used as the working electrode; the Hg/Hg ₂ SO ₄ is used as the reference electrode; the Pt wire is used as the counter electrode. In perchloric acid solution saturated with _O2 , after 10,000 cycles of cyclic voltammetry scanning at 0.6-1.1V, it was observed that the mass specific activity of the catalyst could still be maintained at 635mA/mg _Pt , compared to the initial mass specific activity of 643mA/mg _Pt Hardly lowered. The mass specific activity of the commercial catalyst TKK 46.6% Pt/C decreased by about 25% after 10000 cycles. It can be seen that the stability of the platinum carbon catalyst prepared by this scheme has also been significantly improved.

The platinum-carbon catalysts prepared in Examples 2 and 4 have a stability comparable to that of the platinum-carbon catalysts in Example 3, so details are not repeated here.

It should be noted that, in the above examples, the carbon carrier is KB EC300 for illustration, and other carbon carriers have similar properties to KB EC300, which will not be repeated here. Similarly, in the above examples, potassium chloroplatinate was used as the platinum salt precursor to prepare platinum sulfite complexes, and other platinum salt precursors can also be used to prepare platinum sulfite complexes, which will not be repeated here.

The various technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, which are convenient for a specific and detailed understanding of the technical solution of the present invention, but should not be construed as limiting the protection scope of the invention patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present invention are all within the protection scope of the appended claims of the present invention. Therefore, the protection scope of the patent for the present invention shall be determined by the content of the appended claims, and the description and drawings may be used to interpret the content of the claims.

Claims (10)

1. a preparation method of platinum carbon catalyst, is characterized in that, comprises the steps: Activate the carbon support; Under acidic and ultrasonic stirring conditions, the platinum sulfite complex is mixed with the activated carbon carrier and oxidant to carry out oxidation precipitation reaction to prepare an unmodified platinum carbon sample; and A modifier is modified on the surface of the unmodified platinum-carbon sample to prepare a platinum-carbon catalyst, and the modifier includes any one or more of melamine and melamine polymer. 2. the preparation method of platinum-carbon catalyst according to claim 1, is characterized in that, the step of modifying modifier on the surface of described unmodified platinum-carbon sample comprises: impregnating described unmodified platinum-carbon sample in containing In the solution of the modifying agent, in the solution containing the modifying agent, the concentration of the modifying agent is 0.5mmol/L˜20mmol/L. 3. according to the preparation method of the platinum-carbon catalyst described in any one of claim 1～2, it is characterized in that, described melamine polymer comprises the combination of any one or several in melamine formaldehyde resin and sulfonated melamine formaldehyde resin . 4. the preparation method of platinum-carbon catalyst according to claim 1 is characterized in that, under acidic and ultrasonic stirring conditions, the sulfite complex of platinum is mixed with carbon carrier after activation treatment, oxidizing agent to carry out oxidation precipitation reaction The steps meet any one or more of the following conditions: (1) Ultrasonic power is 100W ~ 250W; (2) The pH of the acidic condition is 2 to 3; (3) The mass ratio of the platinum sulfite complex to the activated carbon support is 0.5:1 to 20:1; (4) The molar ratio of the platinum sulfite complex to the oxidizing agent is 1:30˜1:200. 5. according to the preparation method of the described platinum-carbon catalyst of claim 1 or 4, it is characterized in that, under acidic and ultrasonic stirring conditions, the sulfite complex of platinum is mixed with carbon carrier after activation treatment, oxidizing agent to carry out oxidation The steps of the precipitation reaction include: under acidic conditions, first dissolving the platinum sulfite complex, then mixing with the activated carbon carrier, stirring ultrasonically for 0.5h to 3h, and then adding hydrogen peroxide to carry out oxidation precipitation reaction , ultrasonically stirred for 0.5h to 3h, adding alkaline reagents during the reaction to maintain the pH at 2-3, and then heating to reflux for 0.5h to 3h; or, Under acidic conditions, first dissolve the platinum sulfite complex, then add hydrogen peroxide for oxidation precipitation reaction, ultrasonically stir for 0.5h to 3h, add alkaline reagents during the reaction to maintain the pH at 2-3, after the reaction Then mix with the activated carbon carrier, stir ultrasonically for 0.5h-3h, and then heat and reflux for 0.5h-3h. 6. the preparation method of platinum-carbon catalyst according to claim 1, is characterized in that, the preparation step of the sulfite complex of platinum comprises: first platinum salt precursor is dispersed in water, then add excess saturated NaHSO ₃ solution until precipitation occurs, adjust the pH to 6-10, and prepare the platinum sulfite complex; Wherein, the platinum salt precursor includes any one or more of H ₂ PtCl ₆ , K ₂ PtCl ₆ , K ₂ PtI ₆ , PtCl ₄ , K ₂ PtCl ₄ , PtCl ₂ and H ₂ Pt(OH) ₆ . 7. The preparation method of the platinum-carbon catalyst according to claim 1, characterized in that, the step of activating the carbon carrier comprises: subjecting the carbon carrier to heat treatment in a carbon dioxide atmosphere, and the temperature of the heat treatment is 300° C. ～900℃, the time is 1h～12h; or, heat-treating the carbon carrier in an ammonia atmosphere, the temperature of the heat treatment is 300°C-900°C, and the time is 1h-12h; or, heating the carbon carrier to reflux in nitric acid solution for 1h to 12h; Wherein, the carbon support includes any one or a combination of XC-72R, KB EC300, KB EC600, carbon nanotubes, graphene and Fe-N-C. 8 . The preparation method of the platinum-carbon catalyst according to claim 4 , 6 or 7, characterized in that, the loading amount of platinum in the platinum-carbon catalyst is 15% to 70%. 9. A platinum-carbon catalyst, characterized in that it is prepared by the preparation method of the platinum-carbon catalyst according to any one of claims 1-8. 10. A fuel cell, characterized in that it comprises the platinum-carbon catalyst according to claim 9.

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