High-loading platinum-carbon catalyst and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out photo-reduction deposition on a mixed aqueous solution composed of a platinum salt, a metal salt, a sacrificial agent and a carbon carrier in an inert atmosphere to obtain a platinum alloy carbon-supported catalyst, carrying out oxidation etching on the platinum alloy carbon-supported catalyst in an oxidant solution to obtain a platinum-carbon catalyst intermediate, and carrying out high-loading platinum-carbon catalyst preparation on the platinum-carbon catalyst intermediate to obtain the high-loading platinum-carbon catalyst. And finally, carrying out secondary photo-reduction deposition on the platinum-carbon catalyst intermediate in an aqueous solution consisting of platinum salt and a sacrificial agent to obtain the high-load platinum-carbon catalyst. Through specific steps and conditions, the size of carbon-loaded platinum nanoparticles is effectively reduced, the dispersity and loading capacity of platinum are improved, and the conductivity and defects of the carrier are enhanced, so that the activity and stability of the catalyst are improved, and the preparation method is simple and easy to implement and beneficial to industrial application.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical catalysis, and specifically relates to a high-load platinum-carbon catalyst and a preparation method thereof. Background Art

[0002] Platinum-carbon catalysts have an irreplaceable catalytic effect in the process of hydrogen production by electrolysis of water (PEMWE) and fuel cells (PEMFC) due to their excellent catalytic performance and good catalytic stability. Existing commercial catalysts are mostly high-load (40wt% to 60wt%) platinum-carbon catalysts, and their preparation process mostly uses methods such as alkali precipitation, liquid phase reduction and high-temperature hydrogen reduction. There are usually problems such as difficulty in controlling the size and dispersion of platinum nanoparticles, few effective catalytic active sites, poor catalytic activity and stability, and low platinum utilization. Summary of the invention

[0003] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a high-loaded platinum-carbon catalyst and a preparation method thereof.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for preparing a high-loaded platinum-carbon catalyst comprises the following steps:

[0006] (I) preparing a mixed aqueous solution of platinum salt, metal salt, sacrificial agent and carbon support;

[0007] (II) subjecting the mixed aqueous solution to photoreduction deposition under an inert atmosphere to obtain a platinum alloy carbon-supported catalyst;

[0008] (III) oxidatively etching the platinum alloy carbon-supported catalyst obtained in step (II) in an oxidant solution, washing and drying to obtain a platinum-carbon catalyst intermediate;

[0009] (IV) The platinum-carbon catalyst intermediate obtained in step (III) is uniformly stirred with a platinum salt and a sacrificial agent in an aqueous solution, subjected to secondary photoreduction deposition in an inert atmosphere, and filtered, washed, and dried to obtain a high-load platinum-carbon catalyst.

[0010] In the above technical solution, the preparation of the mixed aqueous solution in step (I) is carried out under an inert gas atmosphere.

[0011] In the above technical solution, the platinum salt is any one or more combinations of chloroplatinic acid, platinum acetylacetonate, platinum nitrate, sodium chloroplatinate or potassium chloroplatinate.

[0012] In the above technical solution, the metal salt is any one or more of palladium dichloride, sodium tetrachloropalladate, dichlorotetraamminepalladium, nickel chloride, nickel nitrate, nickel acetylacetonate, cobalt chloride or cobalt nitrate.

[0013] In the above technical solution, the sacrificial agent is any one or more combinations of methanol, ethanol or isopropanol.

[0014] In the above technical solution, the carbon carrier is any one or more combinations of carbon black, graphitized carbon, high specific surface carbon, Ketjen black or graphene oxide.

[0015] In the above technical solution, the molar ratio of the platinum salt, the metal salt, the sacrificial agent and the carbon carrier is 1:(0.1-0.7):(1-10):(20-120).

[0016] In the above technical solution, the mass of the solvent water in the mixed aqueous solution is 50 to 100 times the mass of the platinum salt.

[0017] In the above technical scheme, the conditions of the photoreduction deposition in step (II) are: the photoreduction deposition is carried out under constant temperature of 25°C and stirring conditions, the light source is a xenon lamp, the wavelength is 190 to 1100 nm, and the light intensity is 0.2 to 1.0 W / cm 2 , the reaction time is 0.5h~5h.

[0018] In the above technical solution, the oxidant is any one or more combinations of hydrogen peroxide, nitric acid, sulfuric acid or sodium bromate.

[0019] In the above technical solution, the concentration of the oxidant in the oxidant solution is 5wt% to 20wt%.

[0020] In the above technical solution, the mass ratio of the oxidant to the platinum salt is (30-80):1.

[0021] In the above technical solution, the conditions of the oxidation etching in step (III) are: reaction temperature 50° C. to 80° C., and reaction time 2 h to 12 h.

[0022] In the above technical scheme, the molar ratio of the platinum salt to the sacrificial agent in step (IV) is 1:(1-10), and the molar ratio of the platinum salt in step (IV) to the platinum salt in step (I) is (2-5):1.

[0023] In the above technical solution, the conditions for the secondary photoreduction deposition in step (IV) are the same as those for the photoreduction deposition in step (II).

[0024] A high-loaded platinum-carbon catalyst is prepared by the method.

[0025] The beneficial effects of the present invention are:

[0026] The invention provides a high-load platinum-carbon catalyst and a preparation method thereof. The platinum alloy carbon-loaded catalyst is synthesized by adopting a photoreduction deposition method, and the parameters such as the illumination wavelength and light intensity, the reduction temperature and time in the photoreduction deposition reaction are adjusted to prepare a platinum alloy catalyst with fine particles and concentrated and uniform particle size distribution. The platinum alloy carbon-loaded catalyst is oxidatively etched by an oxidative etching method to etch away the remaining metals except platinum, effectively adjust the particle size, valence state and defective active sites of platinum nanoparticles, and improve the catalytic activity of the platinum nanoparticles. The carbon carrier is oxidatively modified to increase the number of oxidative functional groups of the carbon carrier, improve the dispersion of platinum, and increase the conductivity and corrosion and oxidation resistance of the carbon carrier. A large number of platinum nanoparticles with fine particles and concentrated and uniform particle size distribution are loaded on the carbon carrier through secondary photoreduction deposition, effectively increasing the platinum loading and avoiding the agglomeration of platinum nanoparticles, so that the catalyst has high loading, high dispersion and high catalytic activity at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of TEM test results of the platinum-carbon catalyst prepared in Example 1 of the present invention;

[0028] Figure 2 is the linear voltammetry (LSV) curve of the platinum-carbon catalyst prepared in Example 1 of the present invention;

[0029] Figure 3 This is the chronoamperometry test curve (CP) of the platinum-carbon catalyst prepared in Example 1 of the present invention.

[0030] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0032] Example 1

[0033] A method for preparing a high-loaded platinum-carbon catalyst comprises the following steps:

[0034] (I) Under a nitrogen atmosphere, 20 mg of platinum acetylacetonate, 4 mg of nickel acetylacetonate, 11.65 mL of isopropanol, and 60 mg of Ketjen black were stirred in 30 mL of aqueous solution until the mixture was uniform, to obtain a mixed aqueous solution;

[0035] (II) In a nitrogen atmosphere, the mixed aqueous solution was stirred at a constant temperature of 50°C, using a xenon lamp as the light source, with a wavelength of 190 to 1100 nm and a light intensity of 0.6 W / cm 2The reduction deposition was carried out for 3 hours; the reactant was filtered, washed and dried to obtain a platinum alloy carbon-supported catalyst;

[0036] (III) oxidatively etching the platinum alloy carbon-supported catalyst in nitric acid water with a mass concentration of 10% at a constant temperature of 60° C. for 5 h, filtering after cooling, washing with pure water and drying to obtain a platinum carbon catalyst intermediate;

[0037] (IV) Weigh 60 mg of the platinum-carbon catalyst intermediate, add 60 mg of platinum acetylacetonate and 35 mL of isopropanol, and mix them evenly in 50 mL of aqueous solution; and perform secondary photoreduction deposition under the same conditions as step (II), and after filtration, washing and drying, obtain a high-loaded platinum-carbon catalyst.

[0038] The schematic diagram of the TEM test results of the platinum-carbon catalyst prepared in this example is as follows: Figure 1 As shown, from Figure 1 It can be seen that the loading amount of platinum nanoparticles on the carbon carrier is high, the nanoparticles are distinct and the particle size distribution is uniform.

[0039] The linear voltammetric curve of the platinum-carbon catalyst prepared in this example is as follows: Figure 2 As shown, from Figure 2 It can be seen that the high-loaded platinum-carbon catalyst exhibits good catalytic activity in the electrochemical test linear voltammetry sweep test (LSV), with an overpotential of only 22 mV.

[0040] The chronoamperometric test curve of the platinum-carbon catalyst prepared in this example is as follows: Figure 3 As shown, from Figure 3 It can be seen that the catalytic performance of the platinum-carbon catalyst is stable within 20 hours without obvious attenuation.

[0041] Comparative Example 1

[0042] In this comparative example, the same preparation method as in Example 1 is used to prepare the oxygen evolution catalyst, and the same electrochemical performance evaluation method is used to evaluate the performance; the difference between this comparative example and Example 1 is that: in step (Ⅰ), nickel acetylacetonate is not added, and the total amount of platinum salt (20+60 mg platinum acetylacetonate) is directly added twice, and a high-load platinum-carbon catalyst is obtained by single photoreduction deposition for 6 hours, and steps (Ⅲ) and (Ⅳ) are no longer performed.

[0043] Comparative Example 2

[0044] In this comparative example, the same preparation method as in Example 1 was used to prepare the hydrogen evolution catalyst, and the same electrochemical performance evaluation method was used to evaluate the performance; the difference between this comparative example and Example 1 is that nickel acetylacetonate was not added in step (I).

[0045] Comparative Example 3

[0046] A method for preparing a platinum-carbon catalyst comprises the following steps:

[0047] (I) 60 mg of keratin black and 80 mg of acetylacetonate platinum were ultrasonically oscillated in 30 mL of ethylene glycol solution for 10 min and stirred at room temperature for 30 min until the mixture was uniform.

[0048] (II) Add 2.5 mol / L sodium hydroxide ethylene glycol solution dropwise to adjust the solution pH to >11.

[0049] (III) The above solution was heated at 150° C. for 3 h under a nitrogen atmosphere, filtered and washed with deionized water after cooling, and then dried in vacuo at 60° C. to obtain a platinum-carbon catalyst.

[0050] Comparative Example 4

[0051] This example adopts the same preparation method as Example 1 to prepare the catalyst, and adopts the same electrochemical performance evaluation method to evaluate the performance; the difference between this comparative example and Example 1 is that in step (III), 10% nitric acid is replaced by 10% hydrochloric acid.

[0052] The electrolysis life of the catalysts prepared in Example 1 and Comparative Examples 1 to 4 was evaluated respectively, and the specific parameters were as follows:

[0053] The electrocatalytic activity and durability were evaluated using a potentiostat with a standard three-electrode electrochemical cell. A graphite rod and a saturated calomel electrode were used as the counter electrode and reference electrode, respectively. The platinum-carbon catalyst loading on the glassy carbon rod was 0.1 mg / cm 2 , all potentials were converted to the potential of the reversible hydrogen electrode (RHE). The OER linear voltammetry (LSV) was measured in an Ar-saturated 0.1M HClO4 solution at a scan rate of 5mV / s, and the durability was measured by the shift of the LSV curve before and after the catalyst underwent 5000 cyclic voltammetry (CV) tests.

[0054] By using the same electrolysis life evaluation method, the comparison results of the electrolysis life of Example 1 and Comparative Examples 1 to 3 are obtained, as shown in Table 1:

[0055] Table 1 Electrolysis life list

[0056] Platinum loading (wt%) <![CDATA[Overpotential η 10 (mV)]]> <![CDATA[η 10 Offset(mV)]]> Example 1 67 22 12 Comparative Example 1 42 125 135 Comparative Example 2 55 52 35 Comparative Example 3 58 40 25 Comparative Example 4 46 85 66

[0057] As shown in Table 1, by comparing Example 1 with Comparative Example 1, it can be seen that the overpotential of the platinum-carbon catalyst formed by single photoreduction deposition of high-content platinum salt is abnormally high, and after 5000 CV cycles, the overpotential offset reaches 135 mV.

[0058] By comparing Example 1 with Comparative Example 2, it can be seen that during the primary photoreduction deposition process, no platinum-nickel alloy is formed, and the platinum-carbon catalyst formed by secondary deposition after oxidation of the carbon carrier in step 3 lacks defect sites of platinum nanoparticles, and the formed particles are relatively large, the overpotential will still be high, and the stability will be reduced.

[0059] By comparing the embodiment with comparative example 3, it can be seen that the high-loaded platinum-carbon catalyst obtained by innovatively adopting the step-by-step deposition and oxidation etching process has higher catalytic activity and better stability.

[0060] By comparing Example 1 with Comparative Example 4, it can be seen that when hydrochloric acid is used to etch the platinum alloy catalyst, hydrochloric acid is only corrosive but not oxidizing, and does not oxidize the carbon carrier, which will reduce the oxidative functional groups of the carbon carrier, affect the platinum loading in the secondary deposition process, and promote further deposition of platinum salts on existing platinum nanoparticles, causing the particles to become larger, the overpotential to increase, and the stability to decrease.

[0061] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a high-loaded platinum-carbon catalyst, characterized in that: The following steps are involved: (I) preparing a mixed aqueous solution of platinum salt, metal salt, sacrificial agent and carbon support; (II) subjecting the mixed aqueous solution to photoreduction deposition under an inert atmosphere to obtain a platinum alloy carbon-supported catalyst; (III) oxidatively etching the platinum alloy carbon-supported catalyst obtained in step (II) in an oxidant solution, washing and drying to obtain a platinum-carbon catalyst intermediate; (IV) The platinum-carbon catalyst intermediate obtained in step (III) is uniformly stirred with a platinum salt and a sacrificial agent in an aqueous solution, subjected to secondary photoreduction deposition in an inert atmosphere, and filtered, washed, and dried to obtain a high-load platinum-carbon catalyst.

2. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The preparation of the mixed aqueous solution in step (I) is carried out under an inert gas atmosphere.

3. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The platinum salt is any one or more combinations of chloroplatinic acid, platinum acetylacetonate, platinum nitrate, sodium chloroplatinate or potassium chloroplatinate; the metal salt is any one or more combinations of palladium dichloride, sodium tetrachloropalladate, dichlorotetraamminepalladium, nickel chloride, nickel nitrate, nickel acetylacetonate, cobalt chloride or cobalt nitrate; the sacrificial agent is any one or more combinations of methanol, ethanol or isopropanol; the carbon carrier is any one or more combinations of carbon black, graphitized carbon, mesoporous carbon, high specific surface carbon, Ketjen black or graphene oxide.

4. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The molar ratio of the platinum salt, the metal salt, the sacrificial agent and the carbon carrier is 1:(0.1-0.7):(1-10):(20-120); the mass of the solvent water in the mixed aqueous solution of step (I) is 50-100 times the mass of the platinum salt.

5. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The conditions of the photoreduction deposition in step (II) are as follows: the photoreduction deposition is carried out under stirring at a constant temperature of 25°C, the light source is a xenon lamp, the wavelength is 190 to 1100 nm, and the light intensity is 0.2 to 1.0 W / cm 2 , the reaction time is 0.5h~5h.

6. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The oxidant is any one or more of hydrogen peroxide, nitric acid, sulfuric acid or sodium bromate; The mass concentration of the oxidant in the oxidant solution is 5% to 20%; The mass of the oxidant is 30 to 80 times that of the platinum salt.

7. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The conditions of the oxidation etching in step (III) are: reaction temperature 50° C. to 80° C., and reaction time 2 h to 12 h.

8. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The molar ratio of the platinum salt to the sacrificial agent in step (IV) is 1:(1-10), and the molar ratio of the platinum salt in step (IV) to the platinum salt in step (I) is (2-5):

1.

9. The method for preparing a high-loaded platinum-carbon catalyst according to claim 1, characterized in that: The conditions of the secondary photoreduction deposition in step (IV) are the same as those of the photoreduction deposition in step (II).

10. A high-load platinum-carbon catalyst, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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