Nano confinement platinum / mesoporous carbon catalyst and preparation method thereof

Abstract

The invention discloses a nano confinement platinum / mesoporous carbon catalyst and a preparation method thereof, and belongs to the technical field of carbon materials and electro-catalysis. The method comprises the following steps: firstly, extracting the coal liquefaction residues by adopting a deep eutectic solvent system to remove light oil and asphaltene, and carrying out acid pickling, water washing and drying to obtain a refined carbon precursor; mixing the carbon precursor with a nano inorganic template, carbonizing and / or activating in an inert atmosphere, and dissolving out the template to construct a mesoporous carbon carrier; dipping the mesoporous carbon carrier in a platinum-containing salt solution to obtain a platinum precursor-loaded composite precursor; and finally, performing staged heat treatment in an inert or reducing atmosphere to decompose the platinum precursor into a nano platinum core, and realizing nano confinement compression and in-situ reduction of platinum nanoparticles in a pore channel in the processes of controllable shrinkage and graphitization rearrangement of a carrier framework, thereby obtaining the platinum-loaded nano-platinum composite material. The prepared catalyst can be used for proton exchange membrane fuel cell electrodes, electrocatalytic hydrogen evolution, oxygen reduction and other hydrogen energy related electrochemical reactions.

Description

Technical Field

[0001] This invention relates to the field of carbon materials and electrocatalysis technology, specifically to a nano-confined platinum / mesoporous carbon catalyst and its preparation method. Background Technology

[0002] Hydrogen-related electrochemical processes (such as proton exchange membrane fuel cells and electrocatalytic hydrogen evolution and oxygen reduction reactions) place extremely high demands on the activity and stability of electrode catalysts. Currently, the common approach is to use a structure where the precious metal platinum is supported on a carbon carrier to improve the dispersion and utilization of the precious metal. Among these, mesoporous carbon materials, with their high specific surface area and ordered pore structure, are considered ideal supports for platinum-based catalysts due to their good conductivity, strong pore connectivity, and excellent corrosion resistance. In existing technologies, mesoporous carbon is mostly prepared from conventional organic precursors such as phenolic resins, sucrose, and petroleum asphalt using hard or soft template methods, followed by impregnation-reduction loading of platinum particles. While these methods are mature, the availability of precursors is limited, costs are high, and it is difficult to balance resource utilization with environmental friendliness.

[0003] Coal liquefaction residue is a large amount of solid byproduct generated during the indirect coal liquefaction process. It contains a large amount of high-carbon, highly aromatic organic components and has good carbonization potential. However, at present, the disposal of coal liquefaction residue is still mainly based on simple incineration or stockpiling, which wastes high-value carbon resources and easily causes environmental pressure. There have been reports on using organic solvent extraction, acid washing and other methods to refine the residue and prepare carbon materials, but most of them use traditional organic solvent systems such as toluene and tetrahydrofuran. These solvents are highly toxic and have high volatilization losses. The extraction process has heavy energy consumption and environmental burden, which is difficult to meet the needs of green and low-carbon development.

[0004] On the other hand, most existing platinum / mesoporous carbon catalysts are obtained through conventional impregnation-reduction processes. During reduction, platinum precursors tend to migrate and aggregate on the pore wall surface, resulting in larger and more unevenly distributed platinum particles and limited metal-support interactions. Under long-term electrochemical cycling or high-potential shock conditions, platinum particles can also undergo dissolution-reprecipitation and sintering growth, leading to a decrease in electrochemical specific surface area and catalytic performance. To improve platinum particle dispersion and stability, existing technologies have introduced measures such as nitrogen-doped carbon and graphitization, but most of these are limited to adjusting the chemical environment of the support surface, providing insufficient spatial confinement and mechanical constraint for platinum nanoparticles, making it difficult to effectively suppress platinum particle migration and loss.

[0005] In summary, existing technologies still have shortcomings in the high-value utilization of coal liquefaction residues, green refining into carbon, and nanostructure regulation of platinum / mesoporous carbon catalysts: First, coal liquefaction residues have not been fully developed into high-performance mesoporous carbon supports, resulting in a low level of resource utilization; second, traditional organic solvent refining routes are not environmentally friendly and are not conducive to large-scale promotion; and third, there is a lack of design ideas for nano-confining and compressing platinum nanoparticles by utilizing the evolution of the support framework structure, which means that there is still considerable room for improvement in the activity and durability of catalysts. Summary of the Invention

[0006] One of the objectives of this invention is to address the problems of existing coal liquefaction residue disposal methods being singular, the refining process having a large environmental burden, and the easy agglomeration of platinum nanoparticles, weak metal-support interaction, and insufficient cycle stability in platinum / mesoporous carbon catalysts. This invention provides a method for preparing nano-confined platinum / mesoporous carbon catalysts, which can produce nano-confined platinum / mesoporous carbon catalysts with high specific surface area, regular mesoporous structure, and strong metal-support interaction.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a nano-confined platinum / mesoporous carbon catalyst includes the following steps:

[0009] a. The coal liquefaction residue is screened to remove large particulate impurities, and the coal liquefaction residue is extracted using a deep eutectic solvent system to remove light oil and asphaltenes, resulting in a solid that has been purified by the deep eutectic solvent; the solid is then pretreated to obtain a coal liquefaction residue carbon precursor.

[0010] b. Mix the coal liquefaction residue carbon precursor obtained in step a with a nano-inorganic template to obtain a template-containing precursor molded body. Carbonize and / or activate it under an inert atmosphere to obtain a template-containing carbon material. Remove the nano-inorganic template by acid washing and dry to obtain a mesoporous carbon carrier.

[0011] c. Prepare a solution containing platinum salt, place the mesoporous carbon support obtained in step b into the solution containing platinum salt, and use equal volume impregnation, vacuum impregnation or ultrasonic-assisted impregnation to allow platinum to enter the interior of the mesoporous carbon channels, and dry to obtain a platinum precursor-loaded composite precursor.

[0012] d. The composite precursor obtained in step c is subjected to staged heat treatment under an inert or reducing atmosphere. In the first stage, the temperature is raised to 200-400℃ and held to decompose the platinum precursor in the composite precursor and form dispersed platinum nanonuclei. In the second stage, the temperature is raised to 400-900℃ and held to cause the mesoporous carbon support framework to undergo controllable shrinkage and / or graphitization rearrangement, thereby performing nano-confined compression and reduction of the platinum nanoparticles inside the pores to obtain a nano-confined platinum / mesoporous carbon catalyst.

[0013] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, in step a, the deep eutectic solvent system consists of a hydrogen bond acceptor and a hydrogen bond donor. The hydrogen bond acceptor is selected from at least one of choline chloride, choline nitrate, and betaine, and the hydrogen bond donor is selected from at least one of urea, glycerol, ethylene glycol, propylene glycol, lactic acid, and acetamide. The molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:1 to 4.

[0014] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, in step a, the mass ratio of the deep eutectic solvent system to the coal liquefaction residue is 2-10:1, the extraction temperature is 40-120 °C, the extraction time is 0.5-6 h, and at least two-stage extraction is used.

[0015] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, step a includes the following pretreatment step: washing with inorganic acid to remove inorganic salts and metal impurities, washing with water until neutral and drying to obtain a refined coal liquefaction residue carbon precursor.

[0016] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, in step b, the nano-inorganic template is selected from nano-magnesium oxide, nano-silica, nano-alumina or nano-titanium dioxide, the nano-inorganic template has a particle size of 5-100 nm, and the mass ratio of the nano-inorganic template to the carbon precursor of coal liquefaction residue is 0.1-3:1.

[0017] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, in step b, the carbonization and / or activation treatment is carried out under a nitrogen and / or argon atmosphere, with the temperature increased to 600-1000 ℃ at a heating rate of 1-10 ℃ / min, and held at that temperature for 0.5-3 h. Optionally, water vapor and / or carbon dioxide are introduced for physical activation to obtain a mesoporous carbon support with a specific surface area of ​​500-2000 m² / g and an average pore size of 2-20 nm.

[0018] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, in step c, the platinum salt-containing solution is chloroplatinic acid, platinum nitrate, platinum sulfate, or their complexes, the platinum concentration in the platinum salt-containing solution is 1–30 mg / mL, and the impregnation time is 0.5–24 h.

[0019] In the above-mentioned method for preparing a nano-confined platinum / mesoporous carbon catalyst, in step d, after the second stage heat treatment, the average pore size of the obtained mesoporous carbon support shrinks by 5-50% relative to the mesoporous carbon support obtained in step b, the average particle size of the obtained platinum nanoparticles is 1-5 nm, and at least 60% of the platinum nanoparticles are distributed inside the mesoporous carbon channels and / or partially embedded in the carbon walls.

[0020] Another object of the present invention is to provide a nano-confined platinum / mesoporous carbon catalyst, which is prepared by any of the above preparation methods. The nano-confined platinum / mesoporous carbon catalyst comprises a mesoporous carbon support constructed with coal liquefaction residue as a carbon source and platinum nanoparticles dispersed in its pores and partially embedded in the carbon walls, wherein the mass fraction of platinum is 0.1 to 40 wt%.

[0021] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0022] (1) The deep eutectic solvent system is used to replace the traditional organic solvent for refining coal liquefaction residue. The extraction selectivity is better, and it can effectively enrich the high aromaticity components suitable for carbonization. At the same time, it has the advantages of low volatility and recyclability, which significantly reduces the environmental burden of the refining process and realizes the green and high-value resource utilization of coal liquefaction residue.

[0023] (2) A mesoporous carbon support with high specific surface area, adjustable pore size and good connectivity was constructed on the basis of coal liquefaction residue through a combination process of nano-inorganic template-carbonization-acid washing, which provides favorable geometric space for confined loading of platinum nanoparticles and mass transfer of reactants / products.

[0024] (3) A staged heat treatment strategy is adopted. In the first stage, the platinum precursor is mildly decomposed and nanonuclei are generated. In the second stage, the platinum nanoparticles in the pores are compressed and partially coated by the controllable shrinkage and graphitization rearrangement of the mesoporous carbon skeleton, so that the particle size of the platinum particles is stabilized in the nanoscale range and the metal-support interaction between the platinum particles and the support is enhanced, effectively inhibiting the migration, sintering and dissolution and reprecipitation of platinum particles.

[0025] (4) The obtained nano-confined platinum / mesoporous carbon catalyst exhibits excellent cycle stability and corrosion resistance while maintaining high platinum utilization and catalytic activity. This is beneficial for reducing the amount of precious metals used, improving the lifespan and economy of hydrogen-related electrochemical devices, and has good prospects for industrial application. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings:

[0027] Figure 1 The N2 adsorption-desorption curves are for the catalysts prepared in Examples 1-6 of this invention.

[0028] Figure 2 The pore size distribution diagrams are for the catalysts prepared in Examples 1-6 of this invention.

[0029] Figure 3 This is a SEM image of the catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0031] All the raw materials required for this invention can be purchased through commercial channels.

[0032] The main technical concept of this invention is as follows: using coal direct liquefaction residue as raw material, refined asphalt with low ash content is obtained through purification, and then cross-linking technology is used to improve the structural stability of the refined asphalt. Combined with the initial wet impregnation template technology, the distribution state of the asphalt in the template channel is precisely controlled, thereby constructing a mesoporous carbon catalyst with stable structure and uniform and regular pore size.

[0033] Example 1:

[0034] A method for preparing a nano-confined platinum / mesoporous carbon catalyst, comprising the following steps:

[0035] Step 1: Take dried coal liquefaction residue from a coal liquefaction unit, sieve it through a 200-mesh sieve to remove large particles, and weigh 100g of the sieve residue. Weigh choline chloride and urea in a molar ratio of 1:2, and dissolve them by stirring at 80℃ to obtain a transparent and homogeneous deep eutectic solvent. Add 400g of this deep eutectic solvent to a three-necked flask, heat to 80℃ and keep at that temperature, then add 100g of the above coal liquefaction residue, and extract by mechanical stirring at 80℃ for 2 h. Filter, and wash the filter cake twice with the same deep eutectic solvent at 80℃. Place the obtained solid in 1 L of 1 mol / L hydrochloric acid, stir at 80℃ for 1 h, filter, wash with deionized water until neutral, and dry at 80℃ for 12 h to obtain refined coal liquefaction residue carbon precursor A.

[0036] Step 2: Mix 20g of precursor A with 20g of nano-magnesium oxide with an average particle size of approximately 20nm, add a small amount of deionized water to form a uniform wet agglomerate, extrude it into strips with a diameter of approximately 2mm, and dry at 110 ℃ for 10 h to obtain a template-containing precursor molded body. Place the molded body in a tube furnace and heat it to 800 ℃ at 5 ℃ / min under a nitrogen atmosphere (200 mL / min), hold it at this temperature for 2 h; during the holding period, water vapor (approximately 20 mL / h) is introduced for physical activation. After cooling, remove the solid, add 800mL of 1mol / L hydrochloric acid and soak at 80℃ for 2 h to dissolve the magnesium oxide template, filter and wash with water until pH≈7, dry at 110 ℃ for 12 h to obtain mesoporous carbon support C-1.

[0037] Step 3: Weigh 1.6 g of carrier C-1. Weigh 0.53 g of chloroplatinic acid hexahydrate and dissolve it in deionized water to prepare a 20 mL solution with a platinum concentration of approximately 10 mg / mL. Using an equal-volume impregnation method, completely add the solution to a beaker containing C-1, gently evacuate to remove gas from the pores, let it stand at room temperature for 12 h, and then dry it at 110 ℃ for 8 h to obtain the platinum precursor-supported composite precursor P-1.

[0038] Step 4: Place P-1 in a tube furnace purged with a 5 vol% H2 / 95 vol% N2 mixture (100 mL / min): First stage: Heat to 280℃ at 2℃ / min and hold for 2 h to decompose the platinum precursor and form dispersed platinum nanonuclei; Second stage: Heat to 700℃ at 5℃ / min and hold for 1 h to graphitize and rearrange the mesoporous carbon framework and cause controlled shrinkage. Cool to room temperature to obtain the catalyst. The SEM image of the catalyst prepared in Example 1 of this invention is shown below. Figure 3 As shown.

[0039] Example 2:

[0040] The difference from Example 1 is that:

[0041] In step a, the deep eutectic solvent used was changed from "choline chloride / urea (molar ratio 1:2)" to "choline chloride / glycerol (molar ratio 1:3)", the mass ratio of deep eutectic solvent to coal liquefaction residue was 3:1, the extraction temperature was 90 ℃, and the time was 3h;

[0042] In step b, the inorganic template is changed from nano-magnesium oxide with an average particle size of about 20 nm to nano-silica with an average particle size of about 10 nm. The mass ratio of template to precursor is 0.5:1, the carbonization temperature is 900 ℃, the holding time is 1.5 h, and CO2 is introduced as an activation gas during the carbonization process.

[0043] In step d, the second stage heat treatment temperature is 650 ℃ and the holding time is 1.5 h. The mass fraction of platinum in the resulting catalyst is about 10 wt%, and the average particle size of platinum nanoparticles is about 2.0 nm, which are mainly distributed inside the mesoporous channels.

[0044] Example 3:

[0045] The difference from Example 1 is that:

[0046] In step a, the deep eutectic solvent was changed from "choline chloride / urea" to "choline chloride / ethylene glycol", the molar ratio of choline chloride to ethylene glycol was 1:4, the mass ratio of deep eutectic solvent to coal liquefaction residue was 5:1, the extraction temperature was 110 ℃, and the time was 1 h.

[0047] In step b, the inorganic template is changed from nano-magnesium oxide to nano-titanium dioxide with an average particle size of about 30 nm. The mass ratio of template to precursor is 0.5:1, the carbonization temperature is 750 ℃, the holding time is 2 h, and no additional activation gas is introduced.

[0048] In step c, the concentration of the platinum precursor solution is 2 mg / mL, and the immersion time is 8 h;

[0049] In step d, the second stage heat treatment temperature is 550 °C and the holding time is 1.5 h. The mass fraction of platinum in the resulting catalyst is about 5 wt%, and the average particle size of platinum particles is about 3.0 nm.

[0050] Example 4:

[0051] The difference from Example 1 is that:

[0052] In step b, the inorganic template is changed from a single nano-magnesium oxide to a composite template of nano-magnesium oxide and nano-silica, with average particle sizes of approximately 50 nm and 20 nm, respectively. The total mass ratio of the composite template to the precursor is 3:1. The carbonization temperature is 850 ℃, and the temperature is maintained for 2 h while CO2 is introduced for activation.

[0053] In step c, the concentration of the platinum precursor solution is 1 mg / mL, the impregnation method is vacuum impregnation + ultrasonic (200 W) combined, and the impregnation time is 4 h;

[0054] In step d, the second stage heat treatment temperature is 600 ℃ and held for 2 h. The mass fraction of platinum in the resulting catalyst is about 0.5 wt%, and the average particle size of platinum particles is about 1.8 nm, mainly distributed in the interior of smaller pores.

[0055] Example 5:

[0056] The difference from Example 1 is that:

[0057] In step a, the deep eutectic solvent was changed from "choline chloride / urea" to "choline chloride / propylene glycol" with a molar ratio of 1:1. The mass ratio of deep eutectic solvent to coal liquefaction residue was 5:1. The extraction temperature was 70 ℃ and the time was 3 h. A two-stage extraction method was adopted.

[0058] In step b, the inorganic template was changed from nano-magnesium oxide to nano-alumina with an average particle size of about 5 nm. The mass ratio of template to precursor was 0.1:1, the carbonization temperature was 700 ℃, and the holding time was 0.5 h.

[0059] In step c, the concentration of the platinum precursor solution was 30 mg / mL, the impregnation volume was controlled by equal volume, and the mass fraction of platinum in the resulting catalyst was approximately 30 wt%.

[0060] In step d, the second-stage heat treatment temperature is 650 ℃, and the temperature is maintained for 1 h. The average particle size of the platinum nanoparticles in the obtained catalyst is about 2.5 nm, and most of them are located in mesoporous channels.

[0061] Example 6:

[0062] The difference from Example 1 is that:

[0063] In step b, the carbonization temperature is adjusted from 800 ℃ to 900 ℃, the holding time is 1 h, and the other conditions remain unchanged;

[0064] In step d, the second-stage heat treatment temperature is increased from 700 ℃ to 800 ℃, and the holding time is shortened to 0.5 h.

[0065] The N2 adsorption-desorption curves of the catalysts prepared in Examples 1-6 of this invention are shown below. Figure 1 As shown, the pore size distribution diagrams of the catalysts prepared in Examples 1-6 are as follows. Figure 2 As shown.

[0066] Comparative Example 1:

[0067] A method for preparing a nano-confined platinum / mesoporous carbon catalyst, comprising the following steps:

[0068] Step 1: Take dried coal liquefaction residue from a coal liquefaction unit, sieve it through a 200-mesh sieve to remove large particles, and weigh 100g of the sieve-passing material. Weigh choline chloride and urea in a molar ratio of 1:2, and dissolve them by stirring at 80℃ to obtain a transparent and homogeneous deep eutectic solvent. Alternatively, instead of using a deep eutectic solvent, treat the coal liquefaction residue by adding 500 mL of a toluene / tetrahydrofuran (volume ratio 1:1) organic mixed solvent, stirring and extracting at 80℃ for 3 h, filtering, washing with deionized water until neutral, and drying at 80℃ for 12 h to obtain refined coal liquefaction residue carbon precursor A.

[0069] Step 2: Mix 20g of precursor A with 20g of nano-magnesium oxide with an average particle size of approximately 20nm, add a small amount of deionized water to form a uniform wet agglomerate, extrude it into strips with a diameter of approximately 2mm, and dry at 110 ℃ for 10 h to obtain a template-containing precursor molded body. Place the molded body in a tube furnace and heat it to 800 ℃ at 5 ℃ / min under a nitrogen atmosphere (200 mL / min), hold it at this temperature for 2 h; during the holding period, water vapor (approximately 20 mL / h) is introduced for physical activation. After cooling, remove the solid, add 800mL of 1mol / L hydrochloric acid and soak at 80℃ for 2 h to dissolve the magnesium oxide template, filter and wash with water until pH≈7, dry at 110 ℃ for 12 h to obtain mesoporous carbon support C-1.

[0070] Step 3: Weigh 1.6 g of carrier C-1. Weigh 0.53 g of chloroplatinic acid hexahydrate and dissolve it in deionized water to prepare a 20 mL solution with a platinum concentration of approximately 10 mg / mL. Using an equal-volume impregnation method, completely add the solution to a beaker containing C-1, gently evacuate to remove gas from the pores, let it stand at room temperature for 12 h, and then dry it at 110 ℃ for 8 h to obtain the platinum precursor-supported composite precursor P-1.

[0071] Step 4: Place P-1 in a tube furnace purged with a 5 vol% H2 / 95 vol% N2 mixture (100 mL / min): First stage: Heat to 280℃ at 2℃ / min and hold for 2 h to decompose the platinum precursor and form dispersed platinum nanonuclei; Second stage: Heat to 700℃ at 5℃ / min and hold for 1 h to graphitize and rearrange the mesoporous carbon framework and cause controlled shrinkage. Cool to room temperature to obtain the catalyst.

[0072] In Comparative Example 1, conventional organic solvents were used instead of deep eutectic solvents for extraction. However, organic solvents have a weaker dissolving and complexing effect on polar oxygen- and nitrogen-containing components and metallic impurities in coal liquefaction residues. After extraction, the raw material still contains a significant amount of heavy polycyclic aromatic hydrocarbons, asphaltenes containing heteroatoms, and inorganic ash. During subsequent carbonization with a nano-inorganic template, these residual heavy components easily aggregate and coke locally, resulting in an uneven microstructure of the carbon skeleton and significant differences in the thickness of the carbon layer around the template. After demolding, the mesoporous structure of the carbon material is incomplete, with a significantly lower specific surface area and pore volume than in Example 1, and a wider pore size distribution. During subsequent platinum salt impregnation and reduction, the surface wettability of the support deteriorates, making it difficult for the platinum precursor to uniformly enter the pores. Platinum nanoparticles mainly aggregate on the outer surface, resulting in a weak nano-confining effect. When used as an energy storage electrode or a noble metal catalyst support, the utilization rate of active sites is low, and both ion and electron transport are limited. The specific capacity, catalytic activity, and cycle stability are all significantly lower than in Example 1.

[0073] Comparative Example 2:

[0074] The difference from Example 1 is that:

[0075] In step a, although the deep eutectic solvent with the same composition as in Example 1 is used, the mass ratio of the deep eutectic solvent to the coal liquefaction residue is adjusted from 4:1 (example) to 1:1, which is lower than the scope defined in the claims. The remaining steps are the same as in Example 1.

[0076] In this comparative example, although a deep eutectic solvent was used, the mass ratio of solvent to coal liquefaction residue was only 1:1, indicating a significantly low solvent dosage. The amount of deep eutectic phase relative to the raw material was insufficient, leading to incomplete dissolution of polar components and inorganic impurities in the residue, and the presence of numerous incompletely dispersed solid agglomerates in the system. During subsequent mixing and molding with nanotemplates, these agglomerates easily coat or block the surface of the template particles, causing a severe imbalance in the local carbon source / template ratio. During carbonization and activation, the blocked areas struggle to form interconnected mesopores, resulting in reduced mesoporosity of the carbon material after demolding, an increase in macropores and blind pores, and a significant deterioration in specific surface area, pore volume, and pore size uniformity. Further platinum salt impregnation resulted in difficulty in wetting the blocked areas with platinum solution, with some channels containing almost no platinum, leading to poor overall platinum dispersion. When used as a functional material (such as an energy storage electrode or catalyst support), insufficient mass transfer channels and uneven distribution of active sites resulted in significantly lower specific activity and utilization rate than in Example 1, failing to demonstrate the technical effect of the preferred solvent dosage of this invention.

[0077] Comparative Example 3:

[0078] The difference from Example 1 is that:

[0079] In step b, no nano-inorganic templates are added, and the refined coal liquefaction residue is directly carbonized in a nitrogen atmosphere. The carbonization temperature and time are the same as in Example 1. The subsequent impregnation and heat treatment steps are the same as in Example 1.

[0080] In this comparative example, the nano-inorganic template was omitted, and the refined coal liquefaction residue was directly carbonized. Due to the lack of template confinement and activation guidance, the resulting carbon framework mainly exhibited a random microporous structure with an extremely low proportion of mesopores and macropores. The specific surface area and pore volume were significantly lower than those of the sample prepared using the template. Subsequently, when impregnating and reducing platinum salt under the same conditions, the platinum precursor was mainly distributed on the outer surface of the carbon particles and at a small number of micropore inlets, making it difficult to achieve nano-confinement "within the pore channels and carbon walls." The resulting catalyst had a large and unevenly distributed platinum particle size, which was prone to migration and sintering during long-term use, resulting in a rapid decrease in the number of active sites. When used as a catalyst support for fuel cell electrodes or reactions such as hydrodechlorination, the active sites were not sufficiently exposed, and the transport of reactants and electrolytes in the pore channels was hindered. The initial activity and cycle stability were significantly lower than those of Example 1, indicating that the nano-inorganic template plays a crucial role in constructing a regular mesoporous structure and achieving nano-confinement.

[0081] Comparative Example 4:

[0082] The difference from Example 1 is that:

[0083] In step b, the inorganic template is changed from nano-magnesium oxide with an average particle size of about 20 nm to magnesium oxide particles with an average particle size of about 300 nm. The mass ratio of template to precursor remains 1:1, and the remaining carbonization, impregnation and heat treatment conditions are the same as in Example 1.

[0084] In this comparative example, magnesium oxide particles with an average particle size of approximately 300 nm were used as templates, and the template size was significantly larger than the nanoscale. After mixing and molding, the spacing between the template particles was relatively large, and during carbonization and activation, channels with a scale of tens to hundreds of nanometers were formed only between the templates, mainly macroporous structures, making it difficult to generate a large number of effective mesopores in the range of 2–20 nm. After demolding, the contribution of the mesopore specific surface area of ​​the carbon material decreased significantly, while the number of macropores and through pores increased, providing almost no restriction or coating effect on the platinum nanoparticles. Subsequently, when loading and reducing platinum salts, the platinum particles mostly adhered to the inner walls of the macropores and the outer surface of the particles, resulting in a significant increase in particle size and severe agglomeration. When used as an energy storage electrode material or catalyst support, although macropores are beneficial for electrolyte penetration, the lack of sufficient mesopores and highly dispersed platinum active sites leads to a significantly lower specific activity and mass utilization rate per unit amount of platinum compared to Example 1, which used small-particle-size nanotemplates, thus failing to fully utilize the advantages of the micro / mesoporous synergistic structure of this invention.

[0085] Comparative Example 5:

[0086] The difference from Example 1 is that:

[0087] In step d, only the first stage of heat treatment is performed: the temperature is raised to 280℃ at 2℃ / min under a reducing atmosphere, held for 2 hours, and then naturally cooled. The second stage of high-temperature heat treatment in the range of 400–900℃ is not performed. The remaining steps are the same as in Example 1.

[0088] In this comparative example, only a first-stage low-temperature heat treatment of approximately 280 °C was performed. Although the platinum precursor decomposed into metallic or low-valent platinum species, the mesoporous carbon framework did not undergo the rearrangement and shrinkage process within the range of 400–900 °C, and the pore size remained essentially unchanged, resulting in a low degree of graphitization of the carbon layers. Due to the lack of a second-stage high-temperature treatment, the pore wall densification and pore size shrinkage were insufficient, leading to a weak physical confinement ability for platinum nanoparticles. Under electrochemical cycling or high-temperature reaction conditions, platinum particles were prone to migration and re-aggregation, with the particle size gradually increasing and the number of active sites continuously decreasing. Simultaneously, the support had poor orderliness and conductivity, limiting electron transport. As a result, the initial specific activity, mass activity, and cycling stability of this comparative catalyst were significantly lower than those of Example 1, and the performance degradation was more significant after prolonged use, indicating that the second-stage high-temperature heat treatment plays an important role in achieving nano-confinement and improving catalytic performance.

[0089] The carbon anode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were tested, and the test results are shown in Table 1.

[0090] Table 1

[0091]

[0092] Table 1 shows that by adjusting the composition and amount of the deep eutectic solvent, the type and size of the nanotemplate, and the segmented heat treatment regime, the synergistic optimization of the pore structure of the mesoporous carbon support and the platinum nano-confined state can be achieved. Taking Example 1 as an example, it has a moderate specific surface area, concentrated pore size, and good matching of platinum loading and particle size. The platinum particles are mainly distributed inside the pores or embedded in the carbon walls. At 0.90 V, it has the highest mass activity and cycle retention rate among all samples, exhibiting the best overall performance. Examples 2-6, by changing the DES system, template type, platinum loading, and second-stage temperature under the above conditions, show slightly lower mass activity and stability than Example 1, but are still significantly better than the comparative examples overall, indicating that the method of the present invention has a wide range of process applicability and adjustability.

[0093] In the comparative examples, some did not use deep eutectic solvents or used insufficient amounts of deep eutectic solvents; some omitted or enlarged nanotemplates; and some omitted the second-stage high-temperature heat treatment. These resulted in incomplete purification and impurity removal, incomplete mesoporous structures, or insufficient confinement of platinum particles. The specific surface area and pore size distribution were inferior to the examples, with corresponding increases in platinum particle size, severe surface agglomeration, and a general and significant decrease in mass activity and cycle retention. These results collectively indicate that a reasonable combination of deep eutectic extraction, nanotemplate construction, and a two-stage heat treatment regime is crucial for obtaining platinum particles with high specific surface area, suitable mesoporous structure, and high dispersion of nano-confined platinum particles. The process scheme in Example 1 is particularly preferred.

[0094] The coal liquefaction residue-based nano-confined platinum / mesoporous carbon prepared by this invention achieves controllable adjustment of the carrier pore structure and the size and distribution of platinum nanoparticles through the synergistic effects of deep eutectic solvent purification, nano-inorganic template pore formation, initial wet impregnation and loading of platinum precursor, and segmented heat treatment. While ensuring high specific surface area and suitable mesoporous structure, it significantly improves the dispersion and stability of platinum, thereby obtaining a catalytic material with high quality activity, high precious metal utilization rate and excellent cycle life.

[0095] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0096] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A method for preparing a nano-confined platinum / mesoporous carbon catalyst, characterized in that, Includes the following steps: a. The coal liquefaction residue is screened to remove large particulate impurities, and the coal liquefaction residue is extracted using a deep eutectic solvent system to remove light oil and asphaltenes, resulting in a solid that has been purified by the deep eutectic solvent; the solid is then pretreated to obtain a coal liquefaction residue carbon precursor. b. Mix the coal liquefaction residue carbon precursor obtained in step a with a nano-inorganic template to obtain a template-containing precursor molded body. Carbonize and / or activate it under an inert atmosphere to obtain a template-containing carbon material. Remove the nano-inorganic template by acid washing and dry to obtain a mesoporous carbon carrier. c. Prepare a solution containing platinum salt, place the mesoporous carbon support obtained in step b into the solution containing platinum salt, and use equal volume impregnation, vacuum impregnation or ultrasonic-assisted impregnation to allow platinum to enter the interior of the mesoporous carbon channels, and dry to obtain a platinum precursor-loaded composite precursor. d. The composite precursor obtained in step c is subjected to staged heat treatment under an inert or reducing atmosphere. In the first stage, the temperature is raised to 200-400℃ and held to decompose the platinum precursor in the composite precursor and form dispersed platinum nanonuclei. In the second stage, the temperature is raised to 400-900℃ and held to cause the mesoporous carbon support framework to undergo controllable shrinkage and / or graphitization rearrangement, thereby performing nano-confined compression and reduction of the platinum nanoparticles inside the pores to obtain a nano-confined platinum / mesoporous carbon catalyst.

2. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step a, the deep eutectic solvent system consists of a hydrogen bond acceptor and a hydrogen bond donor. The hydrogen bond acceptor is selected from at least one of choline chloride, choline nitrate and betaine, and the hydrogen bond donor is selected from at least one of urea, glycerol, ethylene glycol, propylene glycol, lactic acid and acetamide. The molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:1 to 4.

3. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step a, the mass ratio of the deep eutectic solvent system to the coal liquefaction residue is 2 to 10:1, the extraction temperature is 40 to 120 °C, the extraction time is 0.5 to 6 h, and at least two-stage extraction is used.

4. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step a, the pretreatment step is as follows: inorganic salts and metal impurities are removed by washing with inorganic acid, followed by washing with water until neutral and drying to obtain refined coal liquefaction residue carbon precursor.

5. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step b, the nano-inorganic template is selected from nano-magnesium oxide, nano-silica, nano-alumina or nano-titanium dioxide, the nano-inorganic template has a particle size of 5-100 nm, and the mass ratio of the nano-inorganic template to the carbon precursor of coal liquefaction residue is 0.1-3:

1.

6. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step b, the carbonization and / or activation treatment is carried out under a nitrogen and / or argon atmosphere, with the temperature increased to 600-1000 °C at a heating rate of 1-10 °C / min, and held at that temperature for 0.5-3 h. Optionally, water vapor and / or carbon dioxide are introduced for physical activation to obtain a mesoporous carbon support with a specific surface area of ​​500-2000 m² / g and an average pore size of 2-20 nm.

7. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step c, the platinum-containing solution is chloroplatinic acid, platinum nitrate, platinum sulfate or their complexes, the concentration of platinum in the platinum-containing solution is 1-30 mg / mL, and the immersion time is 0.5-24 h.

8. The method for preparing a nano-confined platinum / mesoporous carbon catalyst according to claim 1, characterized in that: In step d, after the second stage of heat treatment, the average pore size of the obtained mesoporous carbon support shrinks by 5-50% relative to the mesoporous carbon support obtained in step b, the average particle size of the obtained platinum nanoparticles is 1-5 nm, and at least 60% of the platinum nanoparticles are distributed inside the mesoporous carbon channels and / or partially embedded in the carbon walls.

9. A nano-confined platinum / mesoporous carbon catalyst, characterized in that, The nano-confined platinum / mesoporous carbon catalyst is prepared by any one of the preparation methods described in claims 1 to 8. The nano-confined platinum / mesoporous carbon catalyst comprises a mesoporous carbon support constructed using coal liquefaction residue as a carbon source and platinum nanoparticles dispersed in its pores and partially embedded in the carbon walls, wherein the mass fraction of platinum is 0.1 to 40 wt%.

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