A method for preparing a platinum-carbon catalyst

Abstract

This invention discloses a method for preparing a platinum-carbon catalyst, comprising the following steps: adding a metal oxide and a hydrophilic surfactant to deionized water to form a mixed pre-reaction solution; adding hydrophilically treated carbon powder, dispersing it evenly to obtain a carbon dispersion; adding an alcohol solution to the carbon dispersion, stirring, and reacting hydrothermally or solvothermally; adding a platinum precursor, a reducing agent, and a salt or organic compound providing an alkaline environment to deionized water to form a platinum precursor solution, a reducing agent solution, and an alkaline precursor solution, respectively; adding these to the treated carbon dispersion; acid treatment and washing with water to obtain the platinum-carbon catalyst. This invention uses surfactants and oxides to adjust the spacing of carbon-supported platinum nanoparticles, enabling the acquisition of Pt / C precursors with high platinum nanoparticle loading dispersed on carbon supports with different specific surface areas, thereby preventing platinum particle growth and controlling particle size during hydrothermal or solvothermal processes.

Description

Technical Field

[0001] This invention belongs to the field of key material manufacturing technology for fuel cells, specifically relating to a method for preparing a platinum-carbon catalyst. Background Technology

[0002] In recent years, fuel cells have attracted much attention due to their high energy conversion efficiency and environmental friendliness, becoming a powerful alternative to traditional energy storage devices. Among them, proton exchange membrane fuel cells (PEMFCs) have low operating temperatures and fast start-up speeds, making them widely applicable in transportation, backup power, and mobile applications. Pt-based materials, due to their high oxygen reduction activity, play a crucial role in improving the cathode kinetics of PEMFCs. However, Pt-based materials are scarce and expensive. Furthermore, Pt has high surface migration energy, making it prone to agglomeration at high temperatures, leading to increased grain size and reduced specific surface area, thus decreasing oxygen reduction activity and durability. Therefore, exploring solutions to the agglomeration problem of Pt-based catalysts is urgently needed.

[0003] To reduce the aggregation of Pt nanoparticles, extensive research has been conducted both domestically and internationally. For example, introducing transition metals to form platinum alloys has been employed. However, these alloys exhibit low physical and chemical stability, with transition metals easily dissolving during testing. Furthermore, their disordered arrangement within the alloy reduces electrochemical activity and stability, limiting improvements in oxygen reduction performance. Notably, introducing surfactants or metal oxides, employing a steric confinement strategy, may help control platinum growth at high temperatures. Surfactants can assist in dispersing platinum nanoparticle precursors on carbon supports, preventing their subsequent transformation into platinum nanoparticles. The hydrophilicity / hydrophobicity of surfactants can also alter the surface binding force of dispersed carbon powder to varying degrees, effectively reducing Pt nanoparticle aggregation on the carbon powder surface. Therefore, the choice of surfactant significantly impacts the performance of platinum-based catalysts. Introducing metal oxides with high content, such as MgO and SnO, readily forms an oxide layer on the material surface, effectively stabilizing platinum particles at high temperatures and limiting their size. Moreover, these oxides are easily dissolved by acids or bases, facilitating their removal from the catalyst without affecting the subsequent activity of the platinum-based catalyst. Therefore, the present invention provides a novel method for preparing a platinum-carbon catalyst with highly dispersed platinum particles by simultaneously introducing metal oxides and surfactants. Summary of the Invention

[0004] To address the shortcomings of existing technologies, and considering that an appropriate ratio of surfactant to metal oxide can promote the inhibition of platinum particle agglomeration, this invention provides a method for preparing a highly efficient platinum-carbon catalyst.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a platinum-carbon catalyst, comprising the following steps:

[0007] Step 1: Add the oxide and hydrophilic surfactant to deionized water, disperse them evenly to form a mixed pre-reaction solution;

[0008] Step 2: Add hydrophilically treated carbon powder to the pre-reaction solution mixed in Step 1, disperse it evenly to obtain a carbon dispersion, add an alcohol solution to the carbon dispersion, stir and react hydrothermally or solvothermally.

[0009] Step 3: Add the platinum precursor, reducing agent, and salt or organic matter that provides an alkaline environment to deionized water to form a platinum precursor solution, a reducing agent solution, and an alkaline precursor solution, respectively.

[0010] Step 4: Adjust the pH of the carbon dispersion treated in Step 2 to 10-12, and add the platinum precursor solution, reducing agent solution and alkaline precursor solution in batches while stirring. During the addition process, control the temperature at 60-150℃, react for 2-8 hours, and stir at 300-1000 rpm.

[0011] Step 5: Treat the solution from the reaction in Step 4 with acid and wash it with water to obtain the platinum-carbon catalyst.

[0012] Preferably, step 1 involves at least one of magnesium oxide, aluminum oxide, zinc oxide, iron oxide, nickel oxide, cobalt oxide, and chromium oxide.

[0013] The hydrophilic surfactant is at least one of cellulose, vinyl acetate polymer, copolymer with vinyl acetate, hemicellulose, starch, pectin, alginic acid, polyacrylamide, H+ type polyacrylic acid, H+ type polymethacrylic acid, H+ type polymaleic acid, sulfonated bisphenol condensate, and lignin; these hydrophilic polymers are hydrophilized by hydrophilic groups such as hydroxyl, ether, carboxyl, ketone, amide, H+ type sulfonic acid, sulfonyl, and ester groups;

[0014] The added oxide and hydrophilic surfactant are added at a ratio of 1:10 to 1:100 of the preset carbon mass; the ratio of the added deionized water volume to the preset carbon mass is 0.1 L / g to 1 L / g.

[0015] Preferably, the dispersion method in steps 1 and 2 is one of homogenizer dispersion, shearing machine dispersion, ultrasonic machine dispersion, and ultrasonic rod dispersion.

[0016] Preferably, the carbon powder in step 2 is at least one of activated carbon, mesoporous carbon, carbon nanotubes, and carbon fibers, and the hydrophilic treatment method for the carbon powder is one of plasma etching and strong acid oxidation.

[0017] Preferably, in step 2, the volume ratio of alcohol to carbon dispersion is 1:10 to 3:1, the stirring rate is 300 to 1000 rpm, the hydrothermal or solvothermal reaction time is 12 to 18 h, and the reaction temperature is 120 °C.

[0018] Preferably, in step 3, the mass ratio of platinum precursor to deionized water is 1 g / L to 20 g / L, the volume ratio of reducing agent to deionized water is 10 g / L to 20 g / L, the volume ratio of salt or organic matter providing an alkaline environment to deionized water is 10 g / L to 50 g / L, the molecular ratio of platinum precursor to reducing agent is 1:10 to 1:40, and the molecular ratio of platinum precursor to salt or organic matter providing an alkaline environment is 1:20 to 1:40.

[0019] Preferably, the platinum precursor in step 3 is at least one of chloroplatinic acid, potassium chloroplatinate, potassium chloroplatinate, platinum chloride, platinum nitrate, tetraaminoplatinum nitrate, and platinum acetylacetonate.

[0020] The reducing agent is at least one of sodium borohydride, potassium borohydride, hydrazine hydrate, hydrazine hydrochloride, ethanol, formic acid, ethylene glycol, and glycerol.

[0021] The salt or organic substance providing the alkaline environment is at least one of ammonium bicarbonate, urea, and melamine.

[0022] Preferably, in step 4, the pH is adjusted by adding one of ammonia, sodium hydroxide, or potassium hydroxide.

[0023] Preferably, the acidic solution used in step 5 includes at least one of sulfuric acid, nitric acid, perchloric acid and hydrochloric acid, the concentration of the acidic solution is controlled between 0.5M and 2M, the pickling temperature is between 50℃ and 90℃, and the pickling time is between 0.2 and 4 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention uses surfactants and oxides to adjust the spacing of carbon-loaded platinum nanoparticles, which can obtain Pt / C precursors with high platinum nanoparticle loading dispersed on carbon supports with different specific surface areas, thereby ensuring that platinum particle growth is prevented during hydrothermal or solvothermal processes and controlling particle size. The carbon powder is hydrophilized by using surfactants, and the surface of the carbon powder after the surfactant is attached forms an electric double layer and they repel each other, so that the carbon powder is evenly dispersed in the solvent, which is conducive to exposing a larger effective loading area of ​​carbon powder. At the same time, the spatial barrier effect of the surfactant further makes the metal ions evenly distributed on the carbon surface.

[0026] (2) In this invention, a surfactant is introduced on the carbon support in advance. Its function is to help disperse the precursor when loading platinum nanoparticle precursor to prevent it from migrating when it is subsequently transformed into platinum nanoparticle. At the same time, the hydrophilic and hydrophobic properties of the surfactant can also change the surface binding force of the carbon powder after dispersion, and introduce oxides to form steric hindrance on the carbon powder surface, further enhancing the dispersion of platinum particle precursor, and obtaining a platinum carbon catalyst with good dispersion.

[0027] (3) The oxides are easily dissolved by acids or bases in subsequent processes, making them convenient to remove from the catalyst without affecting its activity. The oxide steric hindrance agent is deposited on the surface of the carbon powder through self-precipitation, hydrolysis, etc., forming nano-sized particles, not isolated particles or other morphologies. The surfactant and oxide steric hindrance agent are formed by first complexing the oxide with the hydrophilic surfactant, and then forming an oxide layer with a surface coating on the carbon powder surface; the oxide nanoparticles in the coating layer provide steric hindrance and have a certain nano-size effect. Attached Figure Description

[0028] Figure 1 These are the XRD patterns of the platinum-carbon catalysts obtained in Examples 1-4 of this invention;

[0029] Figure 2 These are the CV diagrams of the platinum-carbon catalysts obtained in Examples 1-4 of this invention;

[0030] Figure 3 These are the LSV diagrams of the platinum-carbon catalysts obtained in Examples 1-4 of this invention;

[0031] Figure 4 These are TEM images of the platinum-carbon catalysts obtained in Examples 1-4 of this invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0033] Define 'a' as the ratio of metal loading to the actual specific surface area of ​​the toner used. For example, with a platinum metal loading of 20 wt.%, the specific surface area of ​​the toner is 80 m². 2 If the ratio is / g, then the parameter is a = 80 * 0.8 / 0.2 / 100 = 3.2; the proposed reasonable range of the ratio of a is 2.8 to 60; among which, the preferred value range of a is 2.8 to 7.2. Within the preferred range of a value, the uniformity of platinum nanoparticles and the dispersion distance between each particle are improved, so that the dispersion of each particle is uniform.

[0034] Example 1:

[0035] 1) Weigh 0.3g of cellulose and 1g of magnesium oxide and disperse them in 15L of water. After homogenization, a mixed pre-reaction solution is obtained.

[0036] 2) Add 30g of hydrophilicized carbon powder that has been etched with hydrofluoric acid and ammonia in steps to the mixed pre-reaction solution. Disperse it evenly with an ultrasonic rod and a homogenizer. Add 3L of ethylene glycol and continue stirring. Heat the solution to 120℃ while maintaining a stirring rate of 800rpm and keep it at that temperature for 12h.

[0037] 3) Weigh 43.47g of potassium chloroplatinate and dissolve it in 2.5L of deionized water, weigh 8.43g of sodium borohydride and dissolve it in 0.5L of deionized water, and weigh 123g of urea and dissolve it in 3L of deionized water. Disperse them evenly.

[0038] 4) Adjust the pH of the toner dispersion to 11 using potassium hydroxide and heat it to 90°C. Add potassium chloride platinumate solution, sodium borohydride solution and urea solution in batches, while maintaining a stirring speed of 800 rpm.

[0039] 5) Wash with 0.5M sulfuric acid at 60°C for 2 hours, then wash with deionized water by filtration to obtain the platinum-carbon catalyst.

[0040] The XRD, CV, and LSV data obtained in this embodiment are labeled as follows: Figure 1-3 Curve 1 in the middle, TEM is Figure 4-1 .

[0041] Example 2:

[0042] The steps are the same as in Example 1, except that in step 1), the surfactant is 1g of alginic acid, the oxide is 2g of aluminum oxide, and in step 3), the potassium chloroplatinate is 123g of a platinum nitrate solution containing 16% platinum. The remaining steps are the same as in Example 1.

[0043] The XRD, CV, and LSV data obtained in this embodiment are labeled as follows: Figure 1-3 Curve 2 in the middle, TEM is Figure 4-2 .

[0044] Example 3:

[0045] The steps are the same as in Example 1, except that in step 1), the surfactant is 1g of H+ type polymaleic acid and the oxide is 1.5g of chromium oxide; in step 2), the ethylene glycol content is adjusted to 2L, and the solution is heated to 15h while maintaining a stirring rate of 800rpm, with the reaction temperature remaining constant; in step 4), the pH is adjusted to 11 with concentrated ammonia, and the platinum precursor solution, reducing agent solution, and alkaline precursor solution are added in batches while the temperature is controlled at 90℃ and the reaction is carried out for 4 hours. The remaining steps are the same as in Example 1.

[0046] The XRD, CV, and LSV data obtained in this embodiment are labeled as follows: Figure 1-3 The three curves in the middle, TEM is Figure 4-3 .

[0047] Example 4:

[0048] The steps are the same as in Example 1, except that in step 1), the surfactant is 1g of lignin and the oxide is 2g of nickel oxide, and in step 4), concentrated ammonia is used to adjust the pH to 10 and the temperature is raised to 90°C. The remaining steps are the same as in Example 1.

[0049] The XRD, CV, and LSV data obtained in this embodiment are labeled as follows: Figure 1-3 Curve 4 in the middle, TEM is Figure 4-4 .

[0050] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a platinum-carbon catalyst, characterized in that, Includes the following steps: Step 1: Add the metal oxide and hydrophilic surfactant to deionized water, disperse them evenly to form a mixed pre-reaction solution; the hydrophilic surfactant is at least one of cellulose, vinyl acetate polymer, copolymer with vinyl acetate, hemicellulose, starch, pectin, alginic acid, polyacrylamide, H+ type polyacrylic acid, H+ type polymethacrylic acid, H+ type polymaleic acid, sulfonated bisphenol condensate, and lignin; the added mass of the oxide and hydrophilic surfactant is 1:10 to 1:100 of the preset carbon mass; the ratio of the added volume of deionized water to the preset carbon mass is 0.1 L / g to 1 L / g; Step 2: Add hydrophilically treated carbon powder to the pre-reaction solution mixed in Step 1, disperse it evenly to obtain a carbon dispersion, add an alcohol solution to the carbon dispersion, stir and react hydrothermally or solvothermally. Step 3: Add the platinum precursor, reducing agent, and salt or organic matter that provides an alkaline environment to deionized water to form a platinum precursor solution, a reducing agent solution, and an alkaline precursor solution, respectively. Step 4: Adjust the pH of the carbon dispersion treated in Step 2 to 10-12. While stirring, add the platinum precursor solution, reducing agent solution, and alkaline precursor solution in batches. During the addition process, control the temperature at 60-150°C. o C, react for 2-8 hours, with a stirring speed of 300-1000 rpm; Step 5: Treat the solution from the reaction in Step 4 with acid and wash it with water to obtain the platinum-carbon catalyst.

2. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step 1, at least one of magnesium oxide, aluminum oxide, zinc oxide, iron oxide, nickel oxide, cobalt oxide, and chromium oxide is used.

3. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, The dispersion method in steps 1 and 2 is one of homogenizer, shearing machine, ultrasonic, or ball mill.

4. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step 2, the carbon powder is at least one of activated carbon, mesoporous carbon, carbon nanotubes, and carbon fibers, and the hydrophilic treatment method for the carbon powder is one of plasma etching and strong acid oxidation.

5. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step 2, the volume ratio of alcohol to carbon dispersion is 1:10 to 3:1, the stirring rate is 300 to 1000 rpm, the hydrothermal or solvothermal reaction time is 12 to 18 h, and the reaction temperature is 120 °C.

6. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step 3, the mass ratio of platinum precursor to deionized water is 1 g / L to 20 g / L, the volume ratio of reducing agent to deionized water is 10 g / L to 20 g / L, the volume ratio of salt or organic matter providing an alkaline environment to deionized water is 10 g / L to 50 g / L, the molecular ratio of platinum precursor to reducing agent is 1:10 to 1:40, and the molecular ratio of platinum precursor to salt or organic matter providing an alkaline environment is 1:20 to 1:

40.

7. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, The platinum precursor in step 3 is at least one of chloroplatinic acid, potassium chloroplatinate, potassium chloroplatinate, platinum chloride, platinum nitrate, tetraaminoplatinum nitrate, and platinum acetylacetonate. The reducing agent is at least one of sodium borohydride, potassium borohydride, hydrazine hydrate, hydrazine hydrochloride, ethanol, formic acid, ethylene glycol, and glycerol. The salt or organic substance providing the alkaline environment is at least one of ammonium bicarbonate, urea, and melamine.

8. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step 4, the pH is adjusted by adding one of ammonia, sodium hydroxide, or potassium hydroxide.

9. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, The acid solution used in step 5 includes at least one of sulfuric acid, nitric acid, perchloric acid and hydrochloric acid. The concentration of the acid solution is controlled between 0.5M and 2M, the pickling temperature is between 50℃ and 90℃, and the pickling time is between 0.2 and 4 hours.

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