Thiourea modified carbon support loaded platinum-cobalt solid solution catalyst, preparation method and application thereof

Abstract

The application provides a thiourea-modified carbon carrier loaded platinum-cobalt solid solution catalyst and a preparation method and application thereof, and relates to the technical field of catalyst preparation. First, a commercial carbon carrier is subjected to acid pickling treatment; then the acid-pickled carbon carrier is subjected to impregnation treatment in an organic solvent in which thiourea compounds are dispersed; finally, a platinum-cobalt solid solution catalyst is formed in situ on the carbon carrier by combining one-step solvothermal reduction. The catalyst exhibits excellent catalytic performance in electrocatalytic oxygen reduction reaction. The preparation method has a simple overall process, uses low-cost reagents, has low requirements on production equipment, and is suitable for large-scale batch production.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to a thiourea-modified carbon support supported platinum-cobalt solid solution catalyst, its preparation method, and its application. Background Technology

[0002] Against the backdrop of accelerated global energy transition, proton exchange membrane fuel cells (PEMFCs) have become a key supporting technology for achieving the "dual carbon" goal due to their high efficiency and cleanliness. As the core material of PEMFCs, the performance of the cathode oxygen reduction reaction (ORR) catalyst directly determines the energy conversion efficiency and commercial potential of the battery. Currently, the large-scale application of commercial platinum-based (Pt / C) catalysts is constrained by the scarcity and high cost of platinum resources. Therefore, alloying platinum with transition metals (such as cobalt) has become an important research direction. By forming platinum-based alloys, the electronic structure of Pt can be controlled, and the distribution of active sites can be optimized, thereby improving catalytic activity while reducing the amount of Pt required.

[0003] However, the preparation of platinum-cobalt alloy catalysts faces key technical challenges. On the one hand, while commercially available carbon supports exhibit good conductivity and applicability in fuel cells, their limited surface functionalization groups result in insufficient anchoring ability for transition metal ions. This deficiency makes cobalt prone to migration, aggregation, and even loss during reduction, hindering sufficient alloying with platinum and ultimately leading to a low effective cobalt content in the catalyst, thus limiting the degree of alloying and catalytic performance improvement. On the other hand, while high-temperature treatment commonly used in existing technologies aids alloying, it easily damages the carbon support structure and causes metal particle sintering, reducing the exposure of active sites. For example, invention patent CN120072960A proposes a method for preparing carbon-supported platinum-based intermetallic compound catalysts, aiming to enhance the anchoring ability of the support for metals and achieve ordered alloying through high-temperature graphitization, heteroatom (nitrogen-containing compound) modification, and a stepwise loading strategy. However, this method still has the following shortcomings: the preparation process is complex, involving high-temperature graphitization (2000~2800℃) and multiple high-temperature treatments (400~950℃), which consumes a lot of energy and is prone to causing the collapse of the support pores; the ability to anchor cobalt ions by relying solely on the coordination effect of nitrogen atoms is limited, making it difficult to effectively suppress the migration of cobalt during the reduction process; the high-temperature ordering treatment is prone to causing metal particle agglomeration, making particle size control difficult, ultimately resulting in a large room for improvement in the catalyst's specific activity and electrochemical active area.

[0004] In view of this, developing a catalyst preparation method that is simple in process, mild in conditions, and can effectively anchor cobalt ions and promote the simultaneous reduction of platinum and cobalt is of great significance for improving the oxygen reduction performance of platinum-cobalt alloy catalysts and promoting the commercialization of fuel cells. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a thiourea-modified carbon support for a platinum-cobalt solid solution catalyst, its preparation method, and its application. The preparation method first involves acid washing a commercial carbon support to remove impurities and introduce oxygen-containing functional groups and create defect sites on its surface. Next, the acid-washed carbon support is impregnated in an organic solvent containing thiourea compounds, introducing sulfur and nitrogen functional groups. Finally, a solvothermal reduction step is performed to form a platinum-cobalt solid solution catalyst in situ on the carbon support. On one hand, the oxygen, sulfur, and nitrogen functional groups introduced on the carbon support surface can anchor platinum and cobalt ions through electrostatic adsorption and coordination, inducing a downward shift of the d-band center of platinum, promoting the simultaneous reduction of the two metal ions and forming a uniform platinum-cobalt alloy structure. On the other hand, the sulfur-containing functional groups introduced by the thiourea compounds can generate electrostatic interactions with ionomers (such as Nafion), promoting the uniform distribution of ionomers in the catalyst layer, thereby effectively reducing oxygen mass transfer resistance. The thiourea-modified carbon support for a platinum-cobalt solid solution catalyst prepared in this way exhibits excellent catalytic performance in electrocatalytic oxygen reduction reactions. This preparation method uses an impregnation method to pretreat the carbon support, and the active component is co-reduced and loaded in a one-step process. The overall process is simple, the reagents used are inexpensive, and the requirements for production equipment are low, making it suitable for large-scale batch production.

[0006] In a first aspect, the present invention provides a method for preparing a platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support, comprising the following steps: S1, Acid washing is performed on the commercial carbon support to obtain a pretreated carbon support with a surface rich in oxygen-containing functional groups and defect sites. S2, The pretreated carbon support is subjected to room temperature liquid phase impregnation treatment with thiourea compounds to obtain a modified carbon support with a surface rich in both amino and C=S functional groups. S3, a mixed solution containing platinum precursor and cobalt precursor is mixed with the modified carbon support, and a one-step solvothermal reduction reaction is carried out under alkaline conditions, so that platinum and cobalt are simultaneously reduced under mild conditions of 130~250℃, and a platinum-cobalt solid solution structure is formed in situ on the surface of the modified carbon support, thus preparing a platinum-cobalt solid solution catalyst supported on a thiourea-based modified carbon support.

[0007] As a further improvement of the present invention, in step S2, the thiourea compound is at least one of thiourea, methylthiourea, ethylthiourea, and trimethylthiourea.

[0008] As a further improvement of the present invention, in step S2, the mass ratio of the thiourea compound to the pretreated carbon support is 1:1 to 1:5.

[0009] As a further improvement of the present invention, in step S1, the acid solution used in the pickling treatment is at least one of concentrated nitric acid, concentrated sulfuric acid or concentrated hydrochloric acid, and the treatment time is 1 to 5 hours.

[0010] As a further improvement of the present invention, the solid-liquid ratio of the commercial carbon carrier to the acid solution is 1g:(10~150)ml; the acid washing treatment is only used to introduce oxygen-containing functional groups and does not require high-temperature graphitization treatment.

[0011] As a further improvement of the present invention, the commercial carbon carrier is selected from at least one of Vulcan XC-72R, BP2000, EC-300J, and acetylene black.

[0012] As a further improvement of the present invention, in step S3, the pH value of the alkaline condition is 10-12. This alkaline environment enhances the positive charge of the amino group and strengthens the electrostatic adsorption of platinum chloride complex ions.

[0013] As a further improvement of the present invention, in step S3, the solvent is ethylene glycol, water, or a mixture of ethylene glycol and water; the reaction time of the thermal reduction reaction is 1-8 h. Ethylene glycol, as both a reducing agent and a solvent, promotes the simultaneous reduction of platinum and cobalt ions under mild conditions, avoiding the need for external reducing agents and high-temperature ordering treatment. This effectively avoids the technical problems of carbon support loss and active phase sintering and agglomeration that easily occur under high-temperature conditions, leading to decreased conductivity and poor activity during catalytic oxygen reduction.

[0014] As a further improvement of the present invention, in step S3, the platinum precursor is selected from at least one of chloroplatinic acid, ammonium chloroplatinate, potassium chloroplatinate, and platinum chloride; the cobalt precursor is selected from at least one of cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt acetylacetonate.

[0015] As a further improvement of the present invention, in step S2, the solvent used for the room temperature liquid phase impregnation treatment is at least one of deionized water, ethanol, and ethylene glycol. The room temperature liquid phase impregnation modification avoids damage to the carrier structure caused by high-temperature treatment; after impregnation modification, no high-temperature carbonization treatment is required, and it can be directly used for subsequent metal loading.

[0016] Secondly, the present invention also provides a thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst, which is prepared by the above-described preparation method. In the thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst, platinum and cobalt exist in an atomically mixed solid solution form, with a Pt content of 10-40 wt% and a molar ratio of Pt to Co of 1:0.1-1:1. Among them, the carbon support modified with thiourea compounds anchors cobalt ions through the dual effects of electrostatic adsorption of amino groups and coordination bonding of C / S groups, and induces the downward shift of the d-band center of platinum, thereby achieving simultaneous reduction of platinum and cobalt and highly dispersed loading.

[0017] Thirdly, the present invention also provides an application of a thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst, which is mainly used in the oxygen reduction reaction of hydrogen fuel cells and methanol fuel cells.

[0018] To address the technical bottleneck of insufficient cobalt ion anchoring capacity of existing commercial carbon supports, which hinders the simultaneous reduction of platinum and cobalt, this invention, based on thiourea compounds, modifies the acid-washed carbon support with sulfur and nitrogen functional groups under mild conditions. These functional groups simultaneously anchor and induce the co-reduction of platinum and cobalt during solvothermal processes, directly forming a uniform platinum-cobalt solid solution on the carbon support surface. This fundamentally avoids the technical defects of traditional processes where high-temperature treatment for cobalt anchoring and alloying damages the support structure. The preparation method provided by this invention is based on a thiourea compound modification strategy with a dual synergistic effect of electrostatic adsorption and coordination bonding. The amino and C=S groups in the thiourea molecule respectively exert the dual functions of electrostatic adsorption and coordination anchoring, achieving efficient enrichment and stable fixation of platinum and cobalt ions. The synergistic mechanism is as follows: at the anchoring level, under alkaline conditions, the protonated amino group becomes positively charged, adsorbing platinum chloride complex ions and cobalt ions through electrostatic attraction, achieving initial enrichment of metal ions; simultaneously, the sulfur atom in the C=S group provides a lone pair of electrons, which interact with Co... 2+ The formation of stable coordination bonds and the dual effect effectively inhibited the migration and loss of cobalt during the reduction process, solving the problem of low cobalt loading caused by the single functional group in traditional commercial carbon supports. At the reduction and regulation level, the anchored cobalt ions optimized the electronic structure of platinum through electron-donating effects, causing the d-band center of Pt to shift downwards and lowering the reduction activation energy barrier of platinum-cobalt ions. This allows both to be simultaneously reduced to an atomically mixed solid solution structure under mild solvothermal conditions, avoiding particle sintering and support damage caused by high-temperature processing. Ultimately, an anchoring-regulation-reduction chain reaction was formed, constructing a highly dispersed platinum-cobalt solid solution nanostructure on the carbon support surface.

[0019] Beneficial effects: 1. The method provided by this invention simplifies the preparation process and avoids damage to commercial carbon supports caused by high-temperature processing. It employs room-temperature liquid-phase impregnation combined with mild solvothermal reduction (130–250℃) to achieve simultaneous reduction of platinum and cobalt in a one-step process, significantly simplifying the procedure while fully preserving the pore structure and surface properties of the support. This catalyst preparation method is simple, with easily controllable conditions and processes, making it suitable for stable batch production.

[0020] 2. The method provided by this invention effectively enhances the cobalt ion anchoring ability and solves the problem of low effective cobalt content. By introducing amino and C=S groups through thiourea compounds, a dual anchoring effect of electrostatic adsorption and coordination bonding is achieved, which firmly fixes cobalt ions on the support surface, significantly increasing the effective cobalt content in the catalyst and ensuring full platinum-cobalt alloying.

[0021] 3. The method provided by this invention can promote the simultaneous reduction of platinum and cobalt, achieving a highly dispersed solid solution structure. The anchored cobalt ions act as nucleation sites, inducing the in-situ reduction of platinum around them. Under mild conditions, the two are simultaneously co-reduced to form an atomically mixed solid solution structure, avoiding high-temperature treatment and achieving high dispersion and controllable particle size of nanoparticles.

[0022] 4. The method provided in this invention optimizes the electronic structure of platinum, significantly improving the performance of the catalyst. The thiourea modification-induced downward shift of the d-band center optimizes the intrinsic oxygen reduction activity of platinum. Combined with the highly dispersed solid solution structure, this increases the catalyst's specific activity to 0.93 A / mgPt, and the electrochemical active area reaches 92.61 m². 2 / gPt exhibits excellent oxygen reduction performance.

[0023] 5. The method provided by this invention uses an acid washing process to remove impurities (ash, Fe, Ni, etc.) from the surface of the carbon support, and creates oxygen-containing functional groups such as -COOH and -OH on its surface. It also opens the carbon layer edges, creating defect sites. These defect sites created by acid washing facilitate the anchoring of thiourea molecular groups and Pt ions, further promoting the co-reduction of platinum and cobalt to a platinum-cobalt solid solution structure at the same site. Attached Figure Description

[0024] Figure 1 The XRD patterns are those of the catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention, and the commercial JM 20%Pt / C catalyst.

[0025] Figure 2 The LSV polarization curves are for the catalysts prepared in Example 1, Comparative Examples 1 and 3 of this invention, and for the commercial JM 20%Pt / C catalyst.

[0026] Figure 3 The N2-CV curves are for the catalysts prepared in Example 1, Comparative Examples 1 and 3 of this invention, and for the commercial JM 20%Pt / C catalyst.

[0027] Figure 4 The thermogravimetric analysis curves are those of the catalysts prepared in Example 1, Comparative Examples 1 and 3 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0030] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] While commercially available carbon supports exhibit good conductivity and applicability in fuel cells, their limited surface functionalization groups hinder their application to Co. 2+ The insufficient anchoring ability of transition metal ions leads to the easy migration, aggregation, and even loss of cobalt during the reduction process, making it difficult to fully alloy with platinum. This ultimately results in a low effective cobalt content in the catalyst, limiting the degree of alloying and the improvement of catalytic performance. Furthermore, while high-temperature treatment helps alloying, it easily causes structural damage to the carbon support and sintering of metal particles, reducing the exposure of active sites. This invention provides a thiourea-modified carbon support for a platinum-cobalt solid solution catalyst, its preparation method, and its application. Thiourea compounds are used to impregnate and modify the acid-washed carbon support at room temperature. The amino and C=S groups in the thiourea molecular structure generate a dual anchoring effect of electrostatic adsorption and coordination bonding, thereby effectively fixing Co. 2+ This method induces a downward shift of the d-band center of Pt; based on this, combined with a mild one-step solvothermal reduction, it achieves simultaneous and uniform reduction of platinum-cobalt ions on the support surface and in-situ construction of a highly dispersed solid solution structure, significantly improving the oxygen reduction reaction performance of the catalyst. This method is simple and operates under mild conditions, successfully solving the problems of easy cobalt loss, uneven alloying, and support damage caused by high-temperature treatment in traditional technologies.

[0032] This invention provides a method for preparing a platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support, comprising the following steps: S1, Acid treatment of commercial carbon support to obtain pretreated carbon support with surface rich in oxygen-containing functional groups and defect sites; Specifically: the commercial carbon support is treated in an acidic solution in a water bath for a period of time to remove impurities and form oxygen-containing functional groups on its surface. After filtration, washing with deionized water and drying, the pretreated carbon support is obtained. The commercial carbon carrier is one of Vulcan XC-72R, BP2000, EC-300J, and acetylene black. Preferably, it is one of Vulcan XC-72R and EC-300J.

[0033] The acidic solution is one of concentrated nitric acid, concentrated hydrochloric acid, or concentrated sulfuric acid, and the treatment time is 1-5 hours. Concentrated nitric acid is preferred, and the treatment time is 1-3 hours.

[0034] The solid-liquid ratio of the commercial carbon carrier to the acidic solution is 1 g:(10~150) ml. Preferably, it is 1 g:(10~80) ml.

[0035] S2, the pretreated carbon support is subjected to room temperature liquid phase impregnation treatment with thiourea compounds to obtain a modified carbon support with a surface rich in amino and C=S functional groups; specifically, the pretreated carbon support is added to a solvent containing a certain amount of thiourea compounds, ultrasonically dispersed until uniform, impregnated and stirred at room temperature for a period of time, filtered, washed with deionized water and dried to obtain the modified carbon support. The thiourea compound is a thiourea compound, specifically thiourea, methylthiourea, ethylthiourea, or trimethylthiourea. Preferably, it is one of thiourea or methylthiourea.

[0036] The mass ratio of the thiourea compound to the carbon support is 1:1 to 1:5, preferably 1:1 to 1:3.

[0037] The solvent is one of deionized water, ethanol, and ethylene glycol. Ethylene glycol is preferred.

[0038] The impregnation and stirring time is 1~24 h; the drying temperature is 30~80℃. Preferably, it is 10~20 h and 40~60℃.

[0039] S3. A mixed solution containing platinum and cobalt precursors is mixed with the modified carbon support, and a one-step solvothermal reduction reaction is carried out under alkaline conditions. This allows platinum and cobalt to be simultaneously reduced under mild conditions of 130-250°C, forming a platinum-cobalt solid solution structure in situ on the carbon support surface, thus preparing a thiourea-modified carbon support-supported platinum-cobalt solid solution catalyst. Specifically: the modified carbon support is dispersed in a first solvent and ultrasonically dispersed uniformly. A second solvent containing platinum and cobalt precursors is then added dropwise. After stirring for a period of time, sodium hydroxide is added to adjust the pH of the solution to alkaline. After stirring for another period, the solution is transferred to a mechanically stirred reactor and reacted at high temperature for a certain time. After cooling to room temperature, the solution is filtered, washed, and dried to obtain the thiourea-modified carbon support-supported platinum-cobalt solid solution catalyst.

[0040] The platinum precursor is one of chloroplatinic acid, ammonium chloroplatinate, potassium chloroplatinate, and platinum chloride; the cobalt precursor is one of cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt acetylacetonate. The platinum precursor is preferably one of chloroplatinic acid and ammonium chloroplatinate, and the cobalt precursor is preferably one of cobalt chloride and cobalt nitrate.

[0041] Add sodium hydroxide to adjust the pH to 10-12, preferably 11-12; after adding sodium hydroxide, stir for 5-60 minutes, preferably 30-60 minutes.

[0042] The first solvent and the second solvent are one of ethylene glycol, water, or ethylene glycol / water (1:1 to 5:1).

[0043] The first solvent is preferably ethylene glycol, and the second solvent is preferably water; the reaction temperature is 130~250℃, and the reaction time is 1~8 h, preferably 3~6 h at 150~200℃.

[0044] In the embodiments of this application, the commercial carbon support after acid washing is functionalized with thiourea to enrich its functional groups. Specifically, thiourea compounds are used for modification, and the oxygen-, sulfur-, and nitrogen-containing polar functional groups (such as hydroxyl, mercapto, and amino groups) introduced during the modification process can react with platinum-cobalt precursor ions (Pt). n+ / Co 2+ This generates strong electrostatic adsorption and coordination bonding, effectively anchoring Co. 2+ On the one hand, it inhibits the migration and aggregation of Pt ions, and on the other hand, it modulates the electronic structure of Pt through electron-donating / electron-withdrawing effects, causing the d-band center of Pt to shift downward. This electronic structure optimization effect can significantly reduce the activation energy barrier of the Pt-Co ion reduction reaction, promote the synchronous and uniform reduction of both on the carbon support surface, and construct highly dispersed Pt-Co alloy nanostructures in situ, thereby improving the electrocatalytic oxygen reduction reaction performance of platinum-cobalt solid solution catalysts.

[0045] The present invention also provides a thiourea compound-modified carbon support supported platinum-cobalt solid solution catalyst, which is prepared by the aforementioned preparation method. The thiourea compound-modified carbon support supported platinum-cobalt solid solution catalyst has a Pt content of 10~40 wt% and a Pt to Co molar ratio of 1:0.1~1:1.

[0046] The aforementioned thiourea compounds modified carbon support for platinum-cobalt solid solution catalysts are applied in the oxygen reduction reaction of hydrogen fuel cells and methanol fuel cells.

[0047] The preparation method of the platinum-cobalt solid solution catalyst modified with thiourea compounds supported on a carbon support provided by the present invention will be described below with reference to specific embodiments. Unless otherwise specified, the raw materials and reagents used in the embodiments of this application were purchased commercially.

[0048] Example 1 Example 1 provides a method for preparing a platinum-cobalt solid solution catalyst supported on a carbon support modified with thiourea compounds, comprising the following steps: S1, 3 g of commercial carbon support (EC300-J) was treated in a 150 mL concentrated nitric acid water bath for 2.5 h, and after filtration, washing with deionized water and drying, EC300-J-HNO3 was obtained. S2, dissolve 145mg thiourea in 70mL ethylene glycol solution, add 90mg carbon support EC300-J-HNO3, disperse evenly by ultrasonication, continue to disperse by magnetic stirring, stir for 18h, filter and wash 5 times with water, dry at 60℃ and collect for later use. S2, 50 mg of the treated modified carbon support was dispersed in 75 mL of ethylene glycol. After ultrasonic dispersion, 10.5 mL of 0.0244 M H2PtCl6 / deionized water containing 59 mg of cobalt chloride hexahydrate was added dropwise. After stirring for 20 minutes, 2 mL of 1 M NaOH solution was added dropwise to adjust the pH of the solution to 11.27. After stirring for another 60 minutes, the dispersion was transferred to a reaction vessel and reacted at 190 °C for 5 hours. After the reaction was completed and cooled to room temperature, the solid sample was separated by filtration, washed 5 times with deionized water, and dried at 60 °C to obtain the thiourea-modified carbon support supported platinum-cobalt solid solution catalyst.

[0049] Comparative Example 1 Comparative Example 1 provides a method for preparing a commercially available carbon-supported platinum-cobalt solid solution catalyst. The difference from Example 1 is that step S2, the thiourea modification of the carbon support, is not performed, while the other steps are the same as in Example 1.

[0050] Comparative Example 2 Comparative Example 2 provides a method for preparing a platinum-cobalt solid solution catalyst supported on a carbon support modified with thiourea compounds. The difference from Example 1 is that step S2, the thiourea modification of the carbon support, is not performed, and in step S3, after the carbon support is dispersed in ethylene glycol, 2 ml of an ethylene glycol solution containing 27 mg of thiourea is added dropwise. The other steps are the same as in Example 1.

[0051] Comparative Example 3 Comparative Example 3 provides a method for preparing a platinum-cobalt solid solution catalyst supported on a carbon support modified with thiourea compounds. The difference from Example 1 is that the carbon support is treated differently. After impregnating the carbon support with an equal amount of thiourea, the dried carbon support is heat-treated at 900°C for 3 hours in a N2 atmosphere. The other steps are the same as in Example 1.

[0052] Table 1 Comparison of main parameters and performance of Example 1 with Comparative Examples 1 and 3 Figure 1 The XRD patterns are those of the catalysts prepared in Example 1 and Comparative Examples 1-3, and commercial JM 20%Pt / C. The diffraction peaks of the catalyst prepared in Example 1 corresponding to the Pt (111) and (200) crystal planes are shifted to the right compared to commercial JM 20%Pt / C, indicating that cobalt species are doped into the platinum atomic lattice, leading to lattice distortion and the formation of a platinum-cobalt solid solution structure. The diffraction peaks of the catalyst prepared in Comparative Example 1 corresponding to Pt...0 Characteristic diffraction peaks indicate the loss of cobalt ions during the reduction process. Further experimental observations show that after the reduction reaction, the filtrate was pink when the solid sample was collected, indicating that cobalt ions remained in the reaction solution in an ionic state and were not reduced. Comparative Example 1 demonstrates that the treatment of the carbon support with thiourea compounds facilitates the adsorption of cobalt ions on the carbon support, promoting the co-reduction of platinum and cobalt to form a platinum-cobalt solid solution catalyst. The XRD diffraction peaks of the catalyst prepared in Comparative Example 2 did not show characteristic diffraction peaks corresponding to platinum and cobalt species, indicating that thiourea compounds are not conducive to the reduction of platinum and cobalt ions on the carbon support surface during the reduction reaction. This proves that in the preparation of the platinum-cobalt solid solution catalyst supported on the carbon support modified with thiourea compounds, the effect is to enhance the functionalization of the carbon support surface through pretreatment, rather than decomposing to promote the reduction of platinum and cobalt species during the reduction process. After adding a high-temperature heat treatment step after thiourea impregnation of the carbon support, a platinum-cobalt alloy structure was formed in the XRD pattern of Comparative Example 3, but the corresponding diffraction peak intensity was lower, indicating that its metal content was lower than that of Example 1.

[0053] Figure 2 The LSV polarization curves are shown for the catalysts prepared in Example 1, Comparative Examples 1 and 3, and the commercial JM platinum-carbon catalyst. Based on the results given in Table 1, the specific activity of the catalyst prepared in Comparative Example 1 is only 0.33 A / mg. Pt After adding the step of treating the carbon support with thiourea, the specific activity of the catalyst prepared in Example 1 was significantly improved to 0.93 A / mg. Pt It is significantly higher than that of commercial JM platinum-carbon catalyst (0.12 A / mg). Pt This indicates that using thiourea-modified carbon support can significantly improve the catalytic performance of platinum-cobalt solid solution catalysts. However, after adding the high-temperature treatment step, the specific activity of the catalyst prepared in Comparative Example 3 decreased to 0.57 A / mg. Pt This indicates that the high-temperature treatment step is not conducive to improving the catalyst activity.

[0054] Figure 3 The N2-CV curves for the catalysts prepared in Example 1, Comparative Examples 1 and 3, and the commercial JM platinum-carbon catalyst are shown. Based on the results given in Table 1, the electrochemical active area is: Example 1 > Comparative Example 1 > Comparative Example 3 > Commercial JM platinum-carbon catalyst. This indicates that thiourea-modified carbon supports can effectively suppress the aggregation of active components on the support surface. Furthermore, high-temperature treatment not only destroys the structure of thiourea molecules but also affects the pore structure of the carbon support itself, which is detrimental to the loading of metal ions, leading to a significant reduction in the electrochemical active area.

[0055] Figure 4Thermogravimetric analysis (TGA) curves are shown for the catalysts prepared in Example 1 and Comparative Examples 1 and 3. The catalyst prepared in Comparative Example 1 showed a weight loss of 70.5% and a metal content of approximately 29.5%. After adding a thiourea-treated carbon support step, the catalyst prepared in Example 1 showed a weight loss of 51.94%, which may include some volatilization of thiourea groups, but the metal loading was still significantly higher than that of the catalyst prepared in Comparative Example 1, further demonstrating that thiourea-modified carbon support can enhance the anchoring effect on platinum and cobalt ions. After adding a high-temperature treatment step, the catalyst prepared in Comparative Example 3 showed a weight loss of 61.95% and a metal content of approximately 38.05%, lower than that of the catalyst prepared in Example 1. Figure 1 The XRD results show that although adding a high-temperature treatment step after thiourea modification of the carbon support is beneficial to the co-reduction of platinum-cobalt ions to platinum-cobalt alloy, the high-temperature treatment will cause some of the pores of the carbon support to collapse, reducing the metal loading and thus leading to a decrease in activity.

[0056] Example 2 Example 2 provides a method for preparing a platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support. The difference from Example 1 is that 145 mg of thiourea in step S2 is replaced with 172 mg of thiourea, while the rest is the same as in Example 1.

[0057] Example 3 Example 3 provides a method for preparing a platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support. The difference from Example 1 is that chloroplatinic acid in step S2 is replaced with ammonium chloroplatinate, while the remaining steps are roughly the same as in Example 1.

[0058] Example 4 Example 4 provides a method for preparing a platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support. The difference from Example 1 is that cobalt chloride in step S2 is replaced with cobalt nitrate, while the remaining steps are roughly the same as in Example 1.

[0059] Experiments show that thiourea compounds modified carbon supports for platinum-cobalt solid solution catalysts can be successfully prepared in Examples 2-4.

[0060] The above experimental data show that the preparation method of platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support provided by this invention, when the commercial carbon support is modified with thiourea compounds, introduces ammonia / sulfur groups that react with platinum-cobalt precursor ions (Pt). n+ / Co 2+ It generates strong electrostatic adsorption and coordination bonding, effectively anchoring cobalt ions and inhibiting their migration and aggregation during the reduction process, so that platinum and cobalt ions are reduced simultaneously, forming a highly dispersed platinum-cobalt alloy structure on the carbon support surface, which shows high electrocatalytic activity in oxygen reduction reaction performance tests.

[0061] It should be noted that in other embodiments of the present invention, the carbon black may also be one of Vulcan XC-72R, BP2000, and acetylene black, and the type and content may be selected according to the actual application.

[0062] In summary, this invention provides a thiourea-modified carbon support for a platinum-cobalt solid solution catalyst, its preparation method, and its application, relating to the field of catalyst preparation technology. First, a commercial carbon support is acid-washed to remove impurities and introduce oxygen-containing functional groups onto its surface. Then, the acid-washed carbon support is impregnated in an organic solvent containing thiourea compounds, introducing sulfur and nitrogen functional groups. Finally, a solvothermal reduction step is used to form a platinum-cobalt solid solution catalyst in situ on the carbon support. In this preparation method, the acid-washed commercial carbon support is further functionalized by thiourea compounds, introducing sulfur / nitrogen-containing functional groups, which interact with the platinum-cobalt precursor ions (Pt). n+ / Co 2+ This generates strong electrostatic adsorption and coordination bonding, effectively anchoring Co. 2+ While inhibiting the migration and aggregation of Pt ions, this method optimizes the electronic structure of Pt, causing the d-band center of Pt to shift downward, lowering the activation energy barrier of the Pt-Co ion reduction reaction, promoting the simultaneous and uniform reduction of both ions on the carbon support surface, and enhancing the electrocatalytic oxygen reduction reaction performance of the catalyst. This catalyst exhibits excellent catalytic performance in the electrocatalytic oxygen reduction reaction. The preparation method is simple overall, uses inexpensive reagents, and has low requirements for production equipment, making it suitable for large-scale batch production.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a platinum-cobalt solid solution catalyst modified with thiourea compounds on a carbon support, characterized in that, Includes the following steps: S1, Acid washing is performed on the commercial carbon carrier to obtain a pretreated carbon carrier; S2, the pretreated carbon support is subjected to room temperature liquid phase impregnation treatment with thiourea compounds to obtain a modified carbon support; S3, a mixed solution containing platinum precursor and cobalt precursor is mixed with the modified carbon support, and a one-step solvothermal reduction reaction is carried out under alkaline conditions, so that platinum and cobalt are simultaneously reduced under mild conditions of 130~250℃, and a platinum-cobalt solid solution structure is formed in situ on the surface of the modified carbon support, thereby preparing a platinum-cobalt solid solution catalyst supported on a thiourea-based modified carbon support.

2. The method for preparing the thiourea compound-modified carbon support-supported platinum-cobalt solid solution catalyst according to claim 1, characterized in that, In step S2, the thiourea compound is at least one of thiourea, methylthiourea, ethylthiourea, and trimethylthiourea.

3. The method for preparing the thiourea compound-modified carbon support-supported platinum-cobalt solid solution catalyst according to claim 2, characterized in that, In step S2, the mass ratio of the thiourea compound to the pretreated carbon support is 1:1 to 1:

5.

4. The method for preparing the thiourea compound-modified carbon support supported platinum-cobalt solid solution catalyst according to claim 1, characterized in that, In step S1, the acid solution used in the pickling treatment is at least one of concentrated nitric acid, concentrated sulfuric acid, and concentrated hydrochloric acid, and the treatment time is 1-5 h; the solid-liquid ratio of the commercial carbon carrier to the acid solution is 1 g: (10-150) ml; the commercial carbon carrier is selected from at least one of Vulcan XC-72R, BP2000, EC-300J, and acetylene black.

5. The method for preparing the thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst according to claim 1, characterized in that, In step S3, the pH value of the alkaline condition is 10~12.

6. The method for preparing the thiourea compound-modified carbon support supported platinum-cobalt solid solution catalyst according to claim 1, characterized in that, In step S3, the solvent in the one-step solvothermal reduction reaction is ethylene glycol, water, or a mixture of ethylene glycol and water; the reaction time of the thermal reduction reaction is 1 to 8 hours.

7. The method for preparing the thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst according to claim 1, characterized in that, In step S3, the platinum precursor is selected from at least one of chloroplatinic acid, ammonium chloroplatinate, potassium chloroplatinate, and platinum chloride; the cobalt precursor is selected from at least one of cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt acetylacetonate.

8. The method for preparing the thiourea compound-modified carbon support supported platinum-cobalt solid solution catalyst according to claim 1, characterized in that, In step S2, the solvent used in the room temperature liquid phase impregnation treatment is at least one of deionized water, ethanol, and ethylene glycol.

9. A thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst, prepared by the method described in any one of claims 1-8, characterized in that, In the thiourea-based modified carbon support supported platinum-cobalt solid solution catalyst, the Pt content is 10-40 wt%, and the molar ratio between Pt and Co is 1:0.1-1:1; the platinum and cobalt exist in an atomically mixed solid solution form. Among them, the carbon support modified with thiourea compounds anchors cobalt ions through a dual action of electrostatic adsorption of amino groups and coordination bonding of C=S groups.

10. The application of a thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst prepared by any one of claims 1-8, or the thiourea compound-modified carbon-supported platinum-cobalt solid solution catalyst of claim 9, characterized in that... It is used in the oxygen reduction reaction of hydrogen fuel cells and methanol fuel cells.

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