A sulfur-doped carbon support with optimized pore structure, a preparation method, a catalyst, and a fuel cell

Abstract

The present application belongs to the technical field of electrocatalysis, and particularly relates to a sulfur-doped carbon carrier with optimized pore structure, a preparation method, a catalyst and application. By introducing sulfur-containing materials, the hydrophilic properties of the carbon carrier are modified by sulfur-containing sites, effectively improving the service life and gas transport characteristics of the carbon carrier. The sulfur-containing sites can provide sites for subsequent noble metal loading and anchoring on the carbon carrier, improving the dispersion ability of the noble metal. The strong interaction force between the noble metal and the sulfur can improve the sintering resistance and electrochemical cycle stability of the noble metal particles. The introduction of sulfur-containing surfactants can make the sulfur source enter the pores of the carbon carrier, fill the deep pores, prevent the noble metal particles from entering the deep pores and being unable to be utilized, and in addition, the introduction of the sulfur-containing surfactants is beneficial to the dispersion of the carbon carrier. The better dispersibility of the carbon carrier can make the carrier material fully contact with the metal precursor, promoting the uniform loading and dispersion of the noble metal nanoparticles on the surface of the carrier.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalysis, and particularly relates to a sulfur-doped carbon carrier with optimized pore structure, a preparation method, a catalyst and application. BACKGROUND

[0002] In recent years, hydrogen fuel cells as a green and pollution-free ultimate energy supply system have attracted much attention at home and abroad, and have great application prospects in the field of vehicle fuel cells. However, due to the high oxygen reduction overpotential of the cathode, the electrochemical reaction rate of the cathode, the performance and efficiency of the fuel cell are not satisfactory, and the marketization of the fuel cell cannot be realized. Therefore, in order to improve the performance of the fuel cell, platinum (Pt) or its alloy is usually used as an electrocatalyst. As the most commonly used oxygen reduction reaction electrocatalyst, platinum nanoparticles are usually supported on high specific surface area carbon materials. However, after long-term operation, the weak interaction force between the platinum nanoparticles and the carbon carrier will cause the agglomeration, ripening and peeling of the platinum nanoparticles on the carbon carrier, which reduces the durability of the catalyst.

[0003] In order to solve the problem of weak interaction force between platinum particles and the carrier, researchers actively explore new carbon materials, such as one-dimensional nanowires / rods / tubes, two-dimensional nanobands / sheets, graphene, three-dimensional nanospheres / flowers, etc. In addition, heteroatom-doped carbon materials have been widely studied in the past few decades, such as nitrogen-doped carbon, phosphorus-doped carbon, sulfur-doped carbon, etc. By simple carbon nanostructure manipulation and component adjustment, the physical and chemical properties can be significantly changed, and the application range is expanded. In particular, sulfur-doped carbon has attracted widespread attention in recent years due to its strong affinity for noble metal nanoparticles.

[0004] Theoretical and experimental results have confirmed that the effect of sulfur doping on the carbon carrier includes: the strong interaction force between the sulfur-doped carbon and the noble metal can make the carrier more effectively disperse and stabilize the metal, improve the utilization rate and anti-sintering ability of the metal; and it can also induce charge transfer between the metal and the carrier, causing the electronic structure of the metal active center to change, thereby affecting the adsorption energy of the catalyst for the reaction intermediates, even changing the reaction path in the catalytic reaction process, and ultimately changing the catalytic activity, selectivity and stability of the catalyst.

[0005] The synthesis of traditional sulfur-doped carbon requires pyrolysis of one or more sulfur-containing precursors to form a sulfur-doped carbon support, or heat treatment of carbon materials with sulfur-containing precursors at high temperatures. However, these sulfur source materials are often expensive, toxic and environmentally polluting, and the synthesis process is complex, especially the yield is very low, which is not suitable for mass industrial production. In addition, the sulfur-doped carbon support prepared by the above method is difficult to guarantee in terms of sulfur content, batch consistency, graphitization degree and uniformity of sulfur distribution, and the hydrophilicity of the carbon support treated at high temperature is poor, which is not conducive to the dispersion of the carbon support in the liquid phase, ultimately leading to poor loading and dispersion of active component particles on the surface of the carbon support, so most sulfur-doped carbon materials are not suitable as a support to load platinum as a fuel cell catalyst.

[0006] Therefore, how to prepare sulfur-doped carbon by a simple, low-cost, large-batch synthesis method suitable for fuel cells is of great practical significance for developing new electrocatalysts and improving catalyst durability. SUMMARY

[0007] The present application aims at: in view of the technical defects existing in the preparation method of sulfur-doped carbon and the structure of sulfur-doped carbon support in the prior art, a preparation method of sulfur-doped carbon support with optimized pore structure is provided.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0009] A preparation method of sulfur-doped carbon support with optimized pore structure, comprising the following preparation steps:

[0010] Step S1: mix a first sulfur source with a first solvent to prepare a first sulfur source solution, add the first sulfur source solution to a carbon support material, and obtain a carbon support A through solid-liquid separation and drying treatment;

[0011] Step S2: mix a second sulfur source with a second solvent to prepare a second sulfur source solution, add the second sulfur source solution to the carbon support A in step S1, and obtain a carbon support B through solid-liquid separation and drying treatment, wherein the second sulfur source is a sulfur-containing surfactant;

[0012] Step S3: crush the carbon support B in step S2, and then calcine it in an inert atmosphere to obtain a sulfur-doped carbon support with optimized pore structure, denoted as carbon support C.

[0013] In the technical solution of the present application, by introducing a sulfur-containing material, the hydrophilic property of the carbon carrier is modified by the sulfur-containing site, which effectively improves the service life and gas transport characteristics of the carbon carrier. The sulfur-containing site can provide an anchoring site for subsequent noble metal loading on the carbon carrier, improving the dispersion ability of the noble metal. At the same time, the strong interaction between the noble metal and sulfur can improve the sintering resistance and electrochemical cycle stability of the noble metal particles. The introduction of the sulfur-containing surfactant can make the sulfur source enter the pores of the carbon carrier, fill the deep pores, prevent the noble metal particles from entering too deep pores and being unable to be utilized, and prevent the volatilization of the sulfur-containing material during the heat treatment process, thereby increasing the sulfur content in the carbon carrier. In addition, the introduction of the sulfur-containing surfactant is beneficial to the dispersion of the carbon carrier, and the better dispersion of the carbon carrier can facilitate the full contact of the carrier material and the metal precursor, thereby promoting the uniform loading and dispersion of the noble metal nanoparticles on the surface of the carrier.

[0014] As a preferred technical solution of the present application, in step S1, the first sulfur source includes any one of thiourea, dimethyl sulfoxide, potassium sulfate, magnesium sulfate, benzyl disulfide, and thiophene, preferably a small-molecule organic sulfur source with high sulfur content per unit mass and low boiling point, and further preferably thiourea.

[0015] The first sulfur source is selected as thiourea mainly because thiourea, as a small-molecule sulfur-containing organic material, can provide more sulfur elements for the carbon carrier per unit mass. However, its dispersion is poor during impregnation, and its melting point is low, ranging from 100-200℃. During the heat treatment process, it is easy to volatilize and has poor stability. Sodium dodecylbenzenesulfonate is used as a sulfur-containing surfactant, which has good dispersion and can better enter the pores of the carbon carrier. It is also beneficial to the dispersion of the carbon carrier, has a high melting point, and will not volatilize during the heat treatment process, thereby ensuring the stability of the sulfur content. However, it can provide less sulfur elements per unit mass.

[0016] Preferably, in step S1, the first solvent includes one or more of deionized water, methanol, formaldehyde, ethanol, ethylene glycol, n-propanol, isopropanol, diethyl ether, benzene, and carbon tetrachloride in any proportion, and is preferably deionized water.

[0017] As a preferred technical solution of the present application, in step S2, the second sulfur source includes any one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate, preferably a high-boiling, long-chain macromolecular organic surfactant sulfur source with a boiling point of 400℃ or higher and good stability, and more preferably, the second sulfur source is sodium dodecylbenzenesulfonate.

[0018] The adding sequence of the two sulfur sources has a great influence on the performance of the carbon carrier, and the use of the two sulfur sources and the sequence of adding thiourea first and then sodium dodecyl benzene sulfonate can provide a large amount of sulfur elements for the carrier and achieve the effect of plugging the holes: the use of thiourea first can make it enter the holes of the carbon carrier, and then the use of sodium dodecyl benzene sulfonate can plug the holes, so that, after carbonization by heat treatment, the platinum particles cannot enter too deep holes and cannot be utilized, and the platinum nanoparticles are forced to mainly distribute on the outer surface of the carrier, thereby improving the utilization rate of platinum and the activity of the catalyst; meanwhile, sodium dodecyl benzene sulfonate can plug the holes of thiourea, prevent the volatilization of thiourea in the heat treatment process, and provide more stable and appropriate sulfur elements for the carrier, and meanwhile, the distribution of the sulfur elements and the carrier are more uniform, thereby improving the durability of the catalyst.

[0019] Preferably, in the step S2, the second solvent includes one or more of deionized water, methanol, formaldehyde, ethanol, ethylene glycol, n-propanol, isopropanol, diethyl ether, benzene, carbon tetrachloride, or a mixture of any proportion thereof, and preferably is deionized water.

[0020] As a preferred technical solution of the present application, the mass ratio of the first sulfur source to the second sulfur source is preferably (0.1-10):(0.1-10), and further preferably (1-4):(1-4). Within this range, the carrier can have a high sulfur content, and meanwhile, the carrier has a moderate specific surface area and pore volume. If the first sulfur source is too much, the first sulfur source will volatilize in the heat treatment process, and the effect of sulfur doping on the carrier cannot be achieved; if the second sulfur source is too much, the specific surface area and pore volume of the carrier will greatly decrease, the critical distance between platinum particles will become smaller, the particle size of the synthesized catalyst will increase, and the activity of the catalyst will decrease.

[0021] As a preferred technical solution of the present application, the mass ratio of the sulfur source (the total mass of the first sulfur source and the second sulfur source) to the carbon source is (0.1-10):(0.1-10), and preferably (1-3):(1-3). Within this range, the carrier can have a high sulfur content, and meanwhile, the carrier has a moderate specific surface area and pore volume. If the sulfur source is too little, the effect of sulfur doping on the carrier cannot be achieved; if the sulfur source is too much, the specific surface area and pore volume of the carrier will greatly decrease, the critical distance between platinum particles will become smaller, the particle size of the synthesized catalyst will increase, and the activity of the catalyst will decrease.

[0022] As a preferred technical solution of the present application, the selected carbon carrier material includes but is not limited to one or more of Ketjen Black EC300J, Ketjen Black EC600J, Vulcan XC 72, Black Pearls 2000, and Denka black, and preferably is Ketjen Black EC300J.

[0023] As a more preferred technical solution, in steps S1 and S2, the solid-liquid separation method includes but is not limited to freeze-drying method, decantation method, filtration method, centrifugal separation method, gravity sedimentation method, preferably freeze-drying method.

[0024] Preferably, the inert atmosphere includes any one of helium, neon, argon, nitrogen, preferably nitrogen, with a purity of at least 99.5%; the calcination process includes at least two stages: first purging for 60-200 min, then increasing the temperature to 150-300°C at a rate of 1-5°C / min, and keeping the temperature constant for 1-3 hours; then increasing the temperature to 800-1200°C at a rate of 5-10°C / min, and keeping the temperature constant for 1-5 hours; the gas flow rate is 50-100 ml / min. Two-stage temperature increase can ensure the relative stability of thiourea during heat treatment, reducing the decomposition and volatilization of thiourea.

[0025] As a preferred technical solution of the present application, it further includes step S4, washing the carbon carrier C in step S3 with a washing liquid, drying after solid-liquid separation to obtain a sulfur-doped and surface pore structure changed carbon carrier, denoted as S-C.

[0026] Further preferably, the selected washing liquid includes but is not limited to one or a mixture of deionized water, low-carbon alcohol, acetone, preferably deionized water; further, the washed carbon carrier is vacuum dried at 100-180°C for 6-15 hours to obtain a sulfur-doped and pore structure improved carbon carrier, denoted as S-C.

[0027] A sulfur-doped carbon carrier material obtained by the above preparation method. The carbon carrier material has a high sulfur content, and in the sulfur-doped and pore structure optimized carbon carrier material, the mass content of sulfur is 1-6 wt%, further preferably the mass content of sulfur is 2-5 wt%, which can enhance the interaction between the carrier and platinum particles, and improve the sintering resistance and durability of the catalyst; in addition, the carbon carrier material also has a moderate specific surface area and pore volume, which can force the noble metal particles to be distributed on the surface of the carbon carrier, improve the utilization rate of the noble metal particles, and thus improve the activity of the catalyst; compared with the original carbon material, the surface pore volume is reduced by more than 30%.

[0028] A preparation method of a carbon-supported noble metal catalyst, using the above-mentioned sulfur-doped carbon carrier, specifically further including the following steps:

[0029] Step 1, preparing a precursor solution by mixing platinum precursor and solvent, then uniformly mixing with sodium hydroxide solution, and then adding the carbon carrier S-C to obtain a carbon black suspension after low-temperature ultrasonic dispersion;

[0030] Step 2, the carbon black suspension obtained in step 1 is introduced into a microwave-assisted flow reaction device, and a mixed slurry liquid is obtained by reacting at 150-180℃; the mixed slurry liquid is cooled to room temperature, the pH of the mixed slurry liquid is adjusted to below 3.5, and a carbon-supported platinum-based catalyst is obtained by solid-liquid separation.

[0031] As a preferred technical solution of the present application, the platinum precursor includes chloroplatinic acid and its salts; specifically, one or a combination of several of potassium chloroplatinate, sodium chloroplatinate, platinum nitrate, platinum acetate, and preferably chloroplatinic acid is selected. The selected solvent includes one or a mixture of multiple of deionized water, methanol, formaldehyde, ethanol, ethylene glycol, n-propanol, isopropanol, diethyl ether, benzene, carbon tetrachloride in any proportion, and preferably ethylene glycol is selected.

[0032] A carbon-supported noble metal catalyst obtained by the preparation method described above. The catalyst has good sintering resistance, electrochemical activity and durability.

[0033] A fuel cell comprising the carbon-supported noble metal catalyst described above.

[0034] In summary, due to the adoption of the technical solutions described above, the present application has the following beneficial effects:

[0035] In the carbon support preparation method of the present application, the sulfur-containing material is introduced to modify the hydrophilic properties of the carbon support through the sulfur-containing sites, effectively improving the service life and gas transport characteristics of the carbon support. The sulfur-containing sites can provide sites for the subsequent loading and anchoring of noble metals on the carbon support, improving the dispersion ability of the noble metals. The strong interaction between the noble metals and sulfur can improve the sintering resistance and electrochemical cycle stability of the noble metal particles. The introduction of the sulfur-containing surfactant allows the sulfur source to enter the pores of the carbon support, filling the deeper pores and preventing the noble metal particles from entering too deep pores and being unavailable. At the same time, the introduction of the sulfur-containing surfactant prevents the volatilization of the sulfur-containing material during the heat treatment process, increasing the sulfur content in the carbon support. In addition, the introduction of the sulfur-containing surfactant is beneficial to the dispersion of the carbon support. The better dispersion of the carbon support allows the carrier material to fully contact the metal precursor, promoting the uniform loading and dispersion of the noble metal nanoparticles on the surface of the carrier.

[0036] The carbon support material of the present application has a high sulfur content, which can enhance the interaction between the carrier and platinum particles and improve the sintering resistance and durability of the catalyst. In addition, the carbon support material also has a moderate specific surface area and pore volume, which can force the noble metal particles to be distributed on the surface of the carbon support, improve the utilization rate of the noble metal particles, and thus improve the activity of the catalyst. The surface pore volume of the carbon support material is reduced by more than 30% compared to the original carbon material. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1Transmission electron micrograph of catalyst of sample Pt / C-1 (Comparative Example 1) and sample Pt / S-C-1 (Example 2);

[0038] Figure 2 Durability test plot for platinum catalyst prepared in Example 2;

[0039] Figure 3 Durability test plot for platinum catalyst prepared in Example 3;

[0040] Figure 4 Durability test plot for platinum catalyst prepared in Example 4;

[0041] Figure 5 Durability test plot for platinum catalyst prepared in Example 5;

[0042] Figure 6 Durability test plot for platinum catalyst prepared in Example 6;

[0043] Figure 7 Durability test plot for platinum catalyst prepared in Example 7;

[0044] Figure 8 Durability test plot for platinum catalyst prepared in Comparative Example 1;

[0045] Figure 9 Durability test plot for platinum catalyst prepared in Comparative Example 2;

[0046] Figure 10 Durability test plot for platinum catalyst prepared in Comparative Example 3;

[0047] Figure 11 Durability test plot for platinum catalyst prepared in Comparative Example 4;

[0048] Figure 12 Nitrogen isotherm adsorption-desorption curve of sample C-1 (Comparative Example 1) and sample S-C-1 (Example 1);

[0049] Figure 13 EDS spectrum of sample Pt / S-C-1 (Example 2);

[0050] Figure 14 XRD spectrum of catalyst sample Example 8 Pt / S-C-1-X Figure 14 b) after heat treatment at different temperatures (Example 8 Pt / S-C-1-X Figure 14 a);

[0051] Figure 15The average particle size statistics chart of catalyst sample example 8 (Pt / S-C-1-X) and comparative example 7 (Pt / C-1-X) after heat treatment at different temperatures is shown in the following table. DETAILED DESCRIPTION

[0052] In order to more clearly describe the purposes, technical solutions and advantages of the embodiments of the present application, the following will describe the embodiments in detail with reference to the accompanying drawings. The embodiments described in the above examples are only the basic principles, main features and / or advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples. The above examples and the description in the summary of the application only describe the principles or specific cases of the present application. Without departing from the essence of the present application, the present application can have various changes and improvements. These changes and improvements fall within the scope of the present application.

[0053] The above examples describe only the basic principles, main features and / or advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples. The above examples and the description in the summary of the application only describe the principles or specific cases of the present application. Without departing from the essence of the present application, the present application can have various changes and improvements. These changes and improvements fall within the scope of the present application.

[0054] The present application will be described in detail below with reference to the accompanying drawings.

[0055] In order to make the purposes, technical solutions and advantages of the present application more clear, the following will further describe the present application with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0056] Example 1

[0057] The present embodiment discloses a preparation method of a sulfur-doped carbon carrier, which specifically comprises the following preparation steps:

[0058] S1, first mix 5 grams of thiourea (first sulfur source) with 50 milliliters of 60°C deionized water (first solvent) and mechanically stir for 0.5 hours. Then slowly add the obtained thiourea solution to the prepared 10 grams of crushed KetjenBlack EC300J using a rubber bulb dropper, stirring while adding, and then continue stirring for 0.5 hours. After freeze-drying, carbon sample A is obtained;

[0059] S2, then 5 grams of sodium dodecyl benzene sulfonate (second sulfur source) was mixed with 50 milliliters of 60 °C deionized water (second solvent) and mechanically stirred for 0.5 hours. The resulting sodium dodecyl benzene sulfonate solution was slowly added to the carbon sample A using a rubber bulb dropper while stirring, and then the stirring was continued for 0.5 hours. After that, the carbon sample B was obtained by freeze-drying;

[0060] S3, the carbon support obtained in S2 was ground thoroughly and placed in a tube furnace. High purity nitrogen gas with a purity of 99.999 % was continuously introduced into the furnace at a flow rate of 50 milliliters / min. After purging for 150 min, the furnace was programmed to increase the temperature. First, the temperature was increased to 180 °C at a rate of 2 °C / min and maintained for 1 hour. Then, the temperature was increased to 900 °C at a rate of 5 °C / min and maintained for 2 hours. Subsequently, the temperature was decreased to room temperature to obtain the carbon support sample C.

[0061] S4, the carbon support sample C obtained in S3 was placed in deionized water and ultrasonically dispersed for 1 hour, followed by stirring for 2 hours. Then, the mixture was filtered and washed until the washing filtrate became neutral. Finally, the washed product was placed in a vacuum drying oven and dried at 150 °C for 12 hours to obtain the pretreated and dried carbon support, which was labeled as S-C-1.

[0062] Example 2

[0063] This example was based on the S-C-1 obtained in Example 1, and further prepared Pt / S-C-1.

[0064] Specifically, it included the following steps:

[0065] S5, 200 milliliters of ethylene glycol solution of chloroplatinic acid with a platinum concentration of 5 milligrams / milliliter was poured into a 500 milliliter glass beaker and stirred for 30 min. 60 milliliters of ethylene glycol solution of sodium hydroxide with a concentration of 1 mol / L was added and the stirring was continued for 30 min. 4.05g of S-C-1 was added to the above solution and ultrasonically dispersed at low temperature for 1 hour, followed by mixing and stirring for 30 min to obtain a carbon black suspension.

[0066] S6, the above suspension was introduced into a microwave-assisted flow reaction device and reacted at 160 °C. The reaction mixture was collected and cooled to room temperature. Then, dilute hydrochloric acid solution was added to the slurry to adjust the pH of the slurry to below 3.5, so as to accelerate the settling of the catalyst. Finally, solid-liquid separation was performed by reduced pressure filtration, and the filter cake was washed with hot water at 90-100 °C for multiple times until the washing filtrate became neutral. Finally, the catalyst filter cake was dried in a vacuum at 70 °C for 12 hours. The obtained carbon-supported platinum catalyst sample was labeled as Pt / S-C-1, and the synthesis of the platinum-carbon catalyst was about 5 grams, of which the mass content of platinum was about 20 wt.%. Figure 13 The EDS spectrum of the sample Pt / S-C-1 (Example 2) was obtained by Figure 13It can be seen that the sulfur element is uniformly distributed in the catalyst.

[0067] Example 3

[0068] This example provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of Examples 1-2, the only difference being that in Example 3, the thiourea and sodium dodecyl benzene sulfonate used by S1 and S2 are 8 grams and 2 grams, respectively. The obtained carbon carrier is marked as S-C-2, and the obtained catalyst is marked as Pt / S-C-2.

[0069] Example 4

[0070] This example provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of Examples 1-2, the only difference being that in Example 4, the thiourea and sodium dodecyl benzene sulfonate used by S1 and S2 are 2 grams and 8 grams, respectively. The obtained carbon carrier is marked as S-C-3, and the obtained catalyst is marked as Pt / S-C-3.

[0071] Example 5

[0072] This example provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of Examples 1-2, the only difference being that in Example 5, the first sulfur source used by S1 is changed from 5 grams of thiourea to 5 grams of dimethyl sulfoxide. The obtained carbon carrier is marked as S-C-4, and the obtained catalyst is marked as Pt / S-C-4.

[0073] Example 6

[0074] This example provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of Examples 1-2, the only difference being that in Example 6, the second sulfur source used by S2 is changed from 5 grams of sodium dodecyl benzene sulfonate to 5 grams of sodium dodecyl sulfate. The obtained carbon carrier is marked as S-C-5, and the obtained catalyst is marked as Pt / S-C-5.

[0075] Example 7

[0076] This example provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of Examples 1-2, the only difference being that in Example 7, the first sulfur source used by S1 is changed from 5 grams of thiourea to 5 grams of dimethyl sulfoxide, and the second sulfur source used by S2 is changed from 5 grams of sodium dodecyl benzene sulfonate to 5 grams of sodium dodecyl sulfate. The obtained carbon carrier is marked as S-C-6, and the obtained catalyst is marked as Pt / S-C-6.

[0077] Example 8

[0078] In order to study the stability of the catalyst material, the catalyst prepared in Example 2 was placed in a tube furnace, and argon-hydrogen mixed gas was continuously introduced, with a hydrogen content of 3% and a flow rate of 50 ml / min. After purging for 150 min, the furnace was turned on and programmed to heat at a rate of 5°C / min. The temperature was raised to X°C (X includes 200, 300, 400, 500, and 600), and held constant for 2 hours. Then the temperature was lowered to room temperature, and the obtained catalyst sample was labeled as Pt / S-C-1-X, where X represents the temperature used for heat treatment.

[0079] The above five Pt / S-C-1-X samples and the Pt / S-C-1 sample were subjected to XRD testing, and the XRD patterns shown in Figure (a) were obtained. From the results shown in the figure, it can be seen that as the heat treatment temperature increases, the Pt / S-C-1-X changes relatively gently. This is because the strong interaction between platinum and sulfur in Pt / S-C-1-X causes platinum to be firmly anchored on the support, preventing the agglomeration of platinum particles during heat treatment. Figure 14

[0080] Comparative Example 1

[0081] This comparative example provides a supported platinum-based catalyst sample, which is prepared by a method basically the same as that of Example 2, with the only difference being the use of a different support. In Comparative Example 1, 4.05 grams of original Ketjen Black EC300J was used as the support, labeled as C-1, and the catalyst Pt / C-1 was directly synthesized.

[0082] Figure 12 Nitrogen isothermal adsorption-desorption curves of the carbon support sample C-1 (Comparative Example 1) and the sample S-C-1 (Example 1); by Figure 12 It can be clearly seen that as the amount of sodium dodecyl benzene sulfonate used in the synthesis of the carbon support increases, the specific surface area and pore volume of the support gradually decrease, corresponding to Table 1.

[0083] Comparative Example 2

[0084] This comparative example provides a supported platinum-based catalyst sample, which is prepared by a method basically the same as that of Examples 1-2, with the only difference being that 5 grams of sodium dodecyl benzene sulfonate was used in S2, and there was no step S1, i.e., no thiourea was added. The obtained carbon support was labeled as S2-C-7, and the carbon-supported platinum catalyst sample prepared according to Example 2 was labeled as Pt / S2-C-7.

[0085] Comparative Example 3

[0086] ​The comparative example 3 provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of the comparative examples 1-2, the only difference being that the sodium dodecyl benzene sulfonate used in S2 is 10 grams, and there is no step S1, i.e. no thiourea is added. The obtained carbon carrier is labeled as S2-C-8, and the carbon-supported platinum catalyst sample prepared according to example 2 is labeled as Pt / S2-C-8.

[0087] Comparative example 4

[0088] The comparative example 3 provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of the comparative examples 1-2, the only difference being that the sodium dodecyl benzene sulfonate used in S2 is 10 grams, and there is no step S1, i.e. no thiourea is added. The obtained carbon carrier is labeled as S2-C-8, and the carbon-supported platinum catalyst sample prepared according to example 2 is labeled as Pt / S2-C-8.

[0089] Comparative example 5

[0090] The comparative example 3 provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of the comparative examples 1-2, the only difference being that the sodium dodecyl benzene sulfonate used in S2 is 10 grams, and there is no step S1, i.e. no thiourea is added. The obtained carbon carrier is labeled as S2-C-8, and the carbon-supported platinum catalyst sample prepared according to example 2 is labeled as Pt / S2-C-8.

[0091] Comparative example 6

[0092] The comparative example 3 provides a supported platinum-based catalyst sample, the preparation method of which is basically the same as that of the comparative examples 1-2, the only difference being that the sodium dodecyl benzene sulfonate used in S2 is 10 grams, and there is no step S1, i.e. no thiourea is added. The obtained carbon carrier is labeled as S2-C-8, and the carbon-supported platinum catalyst sample prepared according to example 2 is labeled as Pt / S2-C-8.

[0093] Comparative example 7

[0094] To further demonstrate the stability of the catalyst material of this application, a high-temperature test was conducted using catalyst Pt / C-1 from Comparative Example 1 as an example. Specifically, the catalyst prepared in Comparative Example 1 was placed in a tube furnace, and an argon-hydrogen mixture was continuously introduced. The hydrogen content was 3%, and the flow rate was 50 mL / min. After purging for 150 min, the furnace temperature program was started. The temperature was increased at 5 °C / min. The temperature was raised to X °C (X includes 200, 300, 400, 500, 550, and 600 °C) and held at that temperature for 2 hours. Subsequently, it was cooled to room temperature. The resulting catalyst sample was labeled Pt / C-1-X, where X represents the heat treatment temperature used.

[0095] Further XRD tests were performed on the six Pt / C-1-X catalyst samples and the Pt / C-1 catalyst sample, and the results were as follows: Figure 14 (b) shows the XRD pattern. As can be seen from the results, with the increase of heat treatment temperature, the characteristic peaks of the Pt / C-1-X catalyst gradually become sharper and narrower. The characteristic peaks of the Pt / C-1-X catalyst changed abruptly after 500℃, indicating that the platinum nanoparticles underwent significant aggregation after 500℃ when there was no interaction between the catalyst and the support.

[0096] Furthermore, statistical diagrams of the average particle size of platinum samples Pt / C-1-X (Comparative Example 7) and Pt / SC-1-X (Example 8) after heat treatment at different temperatures were obtained by calculating the (220) crystal plane of platinum according to the Scherrer formula. Figure 15 As shown in the figure, before 500℃, the particle size of Pt / C-1-X is smaller than that of Pt / SC-1-X, but after 500℃, the particle size of Pt / C-1-X increases sharply and exceeds that of Pt / SC-1-X. Figure 14 The XRD results are consistent, which further proves that sulfur doping can enhance the interaction between the carbon support and platinum particles, prevent particle agglomeration during heat treatment, and improve the catalyst's anti-sintering performance.

[0097] Half-cell performance tests were conducted on the catalysts of Examples 2-7 and Comparative Examples 1-4.

[0098] Performance testing method: Weigh 16 mg of the prepared catalyst and add 10 mL of deionized water and isopropanol solution. Disperse the catalyst evenly by ultrasonic vibration for 30 min. After cooling to room temperature, add 200 μL of Nafion ion exchange resin solution (5% by mass, DuPont). Then, ultrasonically vibrate the solution in ice water for 10 min. Using a microsyringe, aspirate 6.5 μL and uniformly coat it onto a glassy carbon rotating disk electrode (5 mm inner diameter) to prepare a catalyst film. Use this as the working electrode, a platinum wire as the counter electrode, and a saturated calomel electrode as the reference electrode.

[0099] The electrolyte solution was a 0.1 mol / L solution of perchloric acid saturated with nitrogen. The catalyst was activated by cyclic voltammetry for 30 cycles at a scan rate of 50 mV / s in a voltage window of 0.05-1.2 V. Subsequently, the linear sweep polarization curve was tested in a 0.1 mol / L solution of perchloric acid saturated with oxygen, at a rotation speed of 1600 rpm, in a scan range of 0.05-1.03 V, and at a scan rate of 10 mV / s.

[0100] The durability test was performed at a scan rate of 100 mV / s in a voltage window of 0.6-0.95 V, in a nitrogen atmosphere, and the activation and activity test were performed according to the above-mentioned activity test standard.

[0101] The performance tests described above were performed on the catalysts of Examples 2-7 and Comparative Examples 1-4, and the results are shown in Table 1. Figures 2-11

[0102] Table 1. EDS elemental characterization results, specific surface area, and pore volume of S-C sulfur-doped carbon materials and C-1

[0103]

[0104] As can be seen from the data in Table 1, the selection of the sulfur source, the ratio of the sulfur source, and the heat treatment step can affect the sulfur content, the specific surface area, and the pore volume. In the sulfur-containing carbon carrier with 10 grams of sulfur source, sample S1-C-9 (Comparative Example 4) has the least sulfur content. Although the sulfur content of thiourea per unit mass is high, thiourea is extremely volatile and decomposes during the heat treatment process. In sample S-C-1 (Example 1), thiourea is first introduced into the pores of the carbon carrier using an impregnation method, and then sodium dodecylbenzenesulfonate is used to block the thiourea in the pores, preventing the loss of sulfur elements during the heat treatment process. Thus, a sulfur-doped carbon material with moderate sulfur content and better stability is obtained. Therefore, by selecting and combining different sulfur sources, changing the addition order of the sulfur sources, using a segmented heating process, and changing the heating rate during the heat treatment process, the sulfur content of the carrier can be effectively controlled. The decrease in the pore volume and the specific surface area further proves that the sulfur modification process has a pore-filling effect on the carbon carrier, which helps to avoid the platinum particles from entering too deep pores and being unable to be utilized, thereby improving the activity of the catalyst. In addition, the pore-filling effect can prevent the volatilization of the sulfur-containing substances during the heat treatment process, provide an appropriate amount of sulfur elements, and improve the activity and durability of the catalyst.

[0105] Figure 1 ​Transmission electron microscopy (TEM) images of the catalysts for samples Pt / C-1 (Comparative Example 1) and Pt / SC-1 (Example 2) are shown. In Comparative Example 1, the circled areas represent agglomerated platinum particles, while in Example 2, agglomerated platinum particles are almost invisible. Furthermore, the platinum particles in the boxed areas of Example 2 are more uniformly dispersed than those in Comparative Example 1. This demonstrates that the introduction of sulfur-containing surfactants is beneficial for the dispersion of the carbon support. The superior dispersibility of the carbon support leads to the formation of more platinum particle loading sites. Simultaneously, the strong interaction between sulfur and platinum promotes platinum deposition during synthesis, resulting in more uniform platinum particle dispersion.

[0106] The electrochemical performance of catalysts, such as Figures 2-11 As shown, the initial activity of sample Pt / SC-1 (Example 2) was slightly lower than that of sample Pt / C-1 (Comparative Example 1), but its durability was higher. This is mainly because the addition of thiourea followed by sodium dodecylbenzenesulfonate significantly reduced the specific surface area of ​​the support, resulting in a smaller critical distance between platinum particles. This made the particles more prone to growth during synthesis, leading to a decrease in the catalyst's ECSA and consequently, a decrease in MA. Furthermore, the impregnation process significantly increased the sulfur content of the support, and the strong interaction between platinum and sulfur also contributed to platinum poisoning, thus making the initial activity of Pt / SC-1 slightly lower than that of Pt / C-1. Meanwhile, platinum particles are firmly anchored to the surface of the carbon support, preventing platinum agglomeration and dissolution after long-term operation, enhancing the stability of the catalyst system and improving the durability of the fuel cell. In addition, thiourea is added first to introduce pores, and then sodium dodecylbenzenesulfonate is added to plug pores. With appropriate sulfur doping and proper pore filling, the specific surface area of ​​the carbon support decreases under the combined effect of the two, achieving the effect of plugging pores. This forces the platinum nanoparticles to be mainly distributed on the outer surface of the support, improving the utilization rate of platinum and thus enhancing the activity of the catalyst.

[0107] The activity of sample Pt / SC-2 (Example 3) decreased compared to sample Pt / C-1 (Comparative Example 1) because of the large amount of thiourea and the small amount of sodium dodecylbenzenesulfonate entering the pores. At this ratio, the specific surface area of ​​the support decreased and the particle size of the catalyst increased, but the pore filling rate was insufficient, and the utilization rate of platinum was still not high, thus reducing the initial activity.

[0108] The activity of sample Pt / SC-3 (Example 4) decreased compared to sample Pt / C-1 (Comparative Example 1) because a large amount of sodium dodecylbenzenesulfonate was added. Excessive pore filling led to a significant decrease in specific surface area, which reduced the critical distance between platinum particles. The synthesized catalyst had a larger particle size, resulting in a decrease in catalyst activity.

[0109] The initial activity of sample Pt / S2-C-7 (comparative example 2) is slightly higher than that of sample Pt / C-1 (comparative example 1), which is due to the appropriate plugging of the pores of the carrier, which reduces the specific surface area of the carrier, and the deeper pores of the carrier are blocked, forcing the platinum nanoparticles to be distributed only on the outer surface of the carrier, thereby improving the utilization of platinum and the activity of the catalyst.

[0110] The initial activity and durability of sample Pt / S2-C-8 (comparative example 3) are similar to those of sample Pt / S-C-3 (example 4), which is caused by excessive plugging of the pores.

[0111] The initial activity of sample Pt / S1-C-9 (comparative example 4) is slightly lower than that of sample Pt / C-1 (comparative example 1), which is caused by the slight poisoning effect of the small amount of sulfur content and the low plugging rate.

[0112] The nitrogen adsorption-desorption isotherm curves of sample C-1 (comparative example 1) and sample S-C-1 (example 1) show that the specific surface area and pore volume of the carbon carrier after sulfur modification are significantly reduced, which corresponds to the data in Table 1, indicating that the sulfur source successfully enters the pores and carbonizes, achieving the effect of providing stable and appropriate content of sulfur element and plugging the pores.

[0113] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a sulfur-doped carbon support with optimized pore structure, characterized in that, The method comprises the following steps: Step S1: mixing a first sulfur source with a first solvent to prepare a first sulfur source solution, and adding the first sulfur source solution into a carbon carrier material, and then performing solid-liquid separation and drying to obtain a carbon carrier A; in step S1, the first sulfur source includes any one of thiourea, dimethyl sulfoxide, potassium sulfate, magnesium sulfate, benzyl disulfide, and thiophene; Step S2: mixing a second sulfur source with a second solvent to prepare a second sulfur source solution, and adding the second sulfur source solution into the carbon carrier A in step S1, and then performing solid-liquid separation and drying to obtain a carbon carrier B, wherein the second sulfur source is a sulfur-containing surfactant; Step S3: crushing the carbon carrier B in step S2, and then calcining the carbon carrier B in an inert atmosphere to obtain a sulfur-doped and pore-structure-optimized carbon carrier, denoted as a carbon carrier C.

2. The method of claim 1, wherein the carbon support is prepared by a process comprising: In step S2, the second sulfur source includes any one of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate. ​ 3. The method for preparing a sulfur-doped carbon support with optimized pore structure according to claim 2, characterized in that, The mass ratio of the first sulfur source to the second sulfur source is (0.1-10):(0.1-10).

4. The method of claim 3, wherein the carbon support is prepared by a process comprising: providing a carbon support; and exposing the carbon support to a sulfur source. The mass ratio of the first sulfur source to the second sulfur source is (1-4):(1-4).

5. The method of claim 2, wherein the carbon support is prepared by a process comprising: 5 mixing a carbon source and a sulfur source to form a mixture; 0 heating the mixture to form a carbon-sulfur composite; and 5 calcining the carbon-sulfur composite to form the carbon support. The mass ratio of the total mass of the first sulfur source and the second sulfur source to the mass of the carbon carrier material is (0.1-10):(0.1-10).

6. The method for preparing a sulfur-doped carbon support with optimized pore structure according to claim 5, characterized in that, The mass ratio of the total mass of the first sulfur source and the second sulfur source to the mass of the carbon carrier material is (1-3):(1-3).

7. The method of claim 1, wherein the carbon support is prepared by a process comprising: providing a carbon support; and exposing the carbon support to a sulfur source. In step S3, the calcination process includes at least two stages: in the first stage, purging for 60-200 min, and then increasing the temperature to 150-300 ℃ at a rate of 1-5 ℃ / min, and maintaining the temperature for 1-3 h; in the second stage, increasing the temperature to 800-1200 ℃ at a rate of 5-10 ℃ / min, and maintaining the temperature for 1-5 h, and the gas flow rate is 50-100 ml / min, and the inert atmosphere includes any one of helium, neon, argon, and nitrogen.

8. The method of claim 1, wherein the carbon support is prepared by a process comprising: providing a carbon precursor; and exposing the carbon precursor to a sulfur source. The first solvent includes deionized water, methanol, formaldehyde, ethanol, ethylene glycol, n-propanol, isopropanol, diethyl ether, benzene, and carbon tetrachloride, or a mixture of any proportion of one or more thereof; and the second solvent includes deionized water, methanol, formaldehyde, ethanol, ethylene glycol, n-propanol, isopropanol, diethyl ether, benzene, and carbon tetrachloride, or a mixture of any proportion of one or more thereof.

9. A sulfur-doped and pore-structure-optimized carbon carrier material prepared by the preparation method in any one of claims 1-8, wherein the mass content of sulfur in the sulfur-doped and pore-structure-optimized carbon carrier material is 1-6 wt%, and the specific surface area and pore volume of the sulfur-doped and pore-structure-optimized carbon carrier material are reduced by more than 30% compared with those of the original carbon carrier material.

10. A carbon-supported noble metal catalyst, characterized by, The sulfur-doped and pore-structure-optimized carbon carrier material in claim 9.

11. A fuel cell characterized by comprising: The carbon-supported noble metal catalyst in claim 10. The carbon-supported noble metal catalyst in claim 10.

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