An alloy catalyst, a method for preparing the same, and an application thereof

Abstract

The application belongs to the technical field of catalysts, and discloses an alloy catalyst and a preparation method and application thereof.The alloy catalyst comprises a PdM alloy nanoflower, wherein M represents a non-palladium transition metal.The preparation process of the alloy catalyst is to replace a traditional single solvent with a composite solvent, and the composite solvent can not only efficiently disperse palladium salt and non-palladium transition metal salt, but also can combine different solvent characteristics with metal ions to produce specific coordination, control the growth direction of metal nanomaterials, and further improve the methanol oxidation performance of the alloy catalyst.In addition, by controlling the type of reducing agent, the growth speed of metal nanomaterials is controlled, the surface and interface structure of the palladium-based alloy material is further controlled, and the performance of the alloy catalyst is optimized.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and specifically relates to an alloy catalyst, its preparation method, and its application. Background Technology

[0002] Palladium (Pd), as a noble metal catalyst, has wide applications in catalytic chemistry, environmental remediation, and energy conversion. Particularly in direct alcohol fuel cells (DAFCs), palladium-based alloy catalysts have attracted considerable attention due to their excellent catalytic activity and stability. Traditional methods for preparing palladium-based alloy catalysts include co-precipitation, impregnation, and chemical vapor deposition. While these methods can produce materials with certain catalytic performance, they often suffer from problems such as complex preparation processes, high costs, and insufficient catalyst activity and stability.

[0003] Direct alcohol fuel cells (DAFCs), as highly efficient energy conversion devices, rely heavily on the catalysts they use for performance. The methanol oxidation reaction (MOR) is a key reaction in DAFCs, placing higher demands on the activity, selectivity, and stability of the catalysts. Currently, methanol oxidation catalysts are mainly based on platinum group metals, but their high cost and resource scarcity limit their large-scale application. Therefore, developing highly active, stable, and cost-effective palladium-based alloy catalysts is of great significance for promoting the commercialization of DAFCs.

[0004] Although solvothermal methods have shown great potential in catalyst preparation, existing technologies still have certain limitations in preparing palladium-based alloy catalysts with specific structures and compositions. For example, for the methanol oxidation reaction, existing catalysts often suffer from insufficient active sites, weak resistance to poisoning, and poor long-term stability.

[0005] Therefore, there is an urgent need to provide a new catalyst with good catalytic activity. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an alloy catalyst, its preparation method, and its application. The alloy catalyst of this invention exhibits good catalytic activity and excellent methanol oxidation performance. The alloy catalyst of this invention can achieve more efficient energy conversion in alcohol fuel cells.

[0007] A first aspect of the present invention provides an alloy catalyst.

[0008] Specifically, an alloy catalyst includes PdM alloy nanoflowers, where M represents a non-palladium transition metal.

[0009] Preferably, M represents at least one of Fe, Co, Ni, and Cu.

[0010] Preferably, in the PdM alloy nanoflowers, the molar ratio of Pd to M is (1-8):(1-5), and more preferably (1-6):(1-3).

[0011] Preferably, the alloy catalyst further includes a support, on which the PdM alloy nanoflowers are loaded.

[0012] Preferably, the carrier is carbon.

[0013] Preferably, the carrier is Ketjen Black ECP-600JD conductive carbon black.

[0014] Preferably, the PdM alloy nanoflowers are PdNi alloy nanoflowers.

[0015] Preferably, the mass ratio of the PdM alloy nanoflowers to the carrier is 1:(1-30), and more preferably 1:(1-20).

[0016] The support is mainly used to load the PdM alloy nanoflowers. After loading, the PdM alloy nanoflowers are better and more uniformly deposited on the support surface, fully exposing the active sites, preventing the aggregation of PdM alloy nanoflowers, and improving the activity and stability of the alloy catalyst.

[0017] A second aspect of the present invention provides a method for preparing an alloy catalyst.

[0018] Specifically, a method for preparing an alloy catalyst includes the following steps:

[0019] The raw materials for preparing the alloy catalyst include a composite solvent, a metal precursor, and a reducing agent. The composite solvent includes octadecene, triethylenetetramine, and m-phenylenediamine.

[0020] The reducing agent is selected from at least one of xylitol and phloroglucinol;

[0021] The metal precursors include palladium salts and non-palladium transition metal salts.

[0022] Preferably, the palladium salt is selected from at least one of palladium acetylacetonate, palladium chloride, and palladium nitrate.

[0023] Preferably, the nickel salt is selected from at least one of nickel formate dihydrate, chloride, nickel sulfate, nickel sulfite, and nickel nitrate.

[0024] Preferably, the iron salt is selected from at least one of ferric sulfate, ferric nitrate, and ferric chloride.

[0025] Preferably, the cobalt salt is selected from at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride.

[0026] Preferably, the copper salt is selected from at least one of copper sulfate, copper nitrate, and copper chloride.

[0027] Preferably, in the composite solvent, the proportions of octadecene, triethylenetetramine, and m-phenylenediamine, by mass fraction, are each 5-90%. For example, the content of octadecene and triethylenetetramine is 5%, and the content of m-phenylenediamine is 90%; or the content of octadecene is 90%, triethylenetetramine is 5%, and the content of m-phenylenediamine is 5%; or the content of octadecene is 5%, triethylenetetramine is 90%, and the content of m-phenylenediamine is 5%; or the content of octadecene is 10%, triethylenetetramine is 10%, and the content of m-phenylenediamine is 80%. The content of each of the three solvents is between 5-90%, and the total content of the three solvents is 100%.

[0028] Preferably, the non-palladium transition metal salt is selected from at least one of iron salts, cobalt salts, nickel salts, and copper salts.

[0029] Preferably, the molar ratio of palladium to non-palladium transition metal in the metal precursor is (1-8):(1-5), and more preferably (1-6):(1-3).

[0030] Preferably, the mass ratio of the metal precursor to the reducing agent is 28:(40-80), and more preferably 28:(55-65).

[0031] Preferably, a method for preparing an alloy catalyst includes the following steps:

[0032] The palladium salt, non-palladium transition metal salt, and reducing agent are added to a composite solvent, mixed, heated to react, and then separated to obtain the alloy catalyst.

[0033] Preferably, the temperature of the heating reaction is 140-220℃, and the heating reaction time is 180-600 min.

[0034] Preferably, the heating reaction is carried out in a high-pressure reactor.

[0035] Preferably, the separation involves centrifuging and washing the product obtained after the heated reaction in an ethanol-cyclohexane mixed solvent to remove residual composite solvent, reducing agent, palladium salt or non-palladium transition metal salt, thereby obtaining the alloy catalyst.

[0036] Preferably, the alloy catalyst is deposited on a support to obtain an alloy catalyst containing a support.

[0037] Preferably, the deposition process is as follows: dissolve the alloy catalyst in cyclohexane, add a support, disperse the catalyst, and then centrifuge and dry it to obtain an alloy catalyst containing the support.

[0038] Preferably, the mass ratio of the alloy catalyst to the support is 1:(1-25), and more preferably 1:(1-20).

[0039] A third aspect of the present invention provides the application of the above-described alloy catalyst.

[0040] An alcohol fuel cell comprising the aforementioned alloy catalyst.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The preparation process of the alloy catalyst described in this invention employs a composite solvent instead of a traditional single solvent. This composite solvent not only efficiently disperses palladium salts and non-palladium transition metal salts, but also combines the specific coordination of different solvent properties with metal ions to regulate the growth direction of metal nanomaterials, thereby improving the methanol oxidation performance of the alloy catalyst. Furthermore, by controlling the type of reducing agent, the growth rate of the metal nanomaterials can be controlled, further controlling the surface and interface structure of the palladium-based alloy material and optimizing the performance of the alloy catalyst.

[0043] Meanwhile, through careful design of composite solvent and reducing agent combinations and optimized reaction conditions, the alloy catalyst of the present invention exhibits higher catalytic activity and is expected to achieve more efficient energy conversion in direct alcohol fuel cells. Attached Figure Description

[0044] Figure 1 TEM image of the PdNi alloy nanoflowers prepared in Example 1;

[0045] Figure 2 TEM image of the PdNi alloy nanomaterial prepared in Comparative Example 1;

[0046] Figure 3 TEM image of the PdNi alloy nanomaterial prepared in Comparative Example 2;

[0047] Figure 4 The image shows the XRD pattern of the PdNi alloy catalyst prepared in Example 1. Detailed Implementation

[0048] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0049] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0050] Example 1

[0051] A method for preparing an alloy catalyst includes the following steps:

[0052] (1) 5 mL of octadecene, 2 mL of triethylenetetramine and 3 mL of m-phenylenediamine were successively added to a beaker and stirred thoroughly to form a composite solvent. Then, 20 mg of palladium acetylacetonate, 8 mg of nickel formate dihydrate and 60 mg of xylitol were added to the composite solvent and stirred for 30 min to mix thoroughly. The mixture was then placed in a high-pressure reactor and heated from room temperature to 160 °C for 6 h within 30 min. After the reaction was completed, the mixture was washed three times by centrifugation with ethanol-cyclohexane solution to obtain PdNi alloy nanoflowers.

[0053] (2) 10 mg of PdNi alloy nanoflowers and 40 mg of Ketjen Black ECP-600JD conductive carbon black powder (i.e. carbon support) were mixed in 10 mL of cyclohexane and ultrasonically dispersed for 1 hour to make the PdNi alloy nanoflowers uniformly deposited on the carbon support. After centrifugation and drying, the alloy catalyst containing carbon support was obtained.

[0054] Example 2

[0055] A method for preparing an alloy catalyst includes the following steps:

[0056] (1) 0.5 mL of octadecene, 0.5 mL of triethylenetetramine and 9 mL of m-phenylenediamine were successively added to a beaker and stirred thoroughly to form a composite solvent. Then, 20 mg of palladium acetylacetonate, 10 mg of nickel formate dihydrate and 65 mg of xylitol were added to the composite solvent and stirred for 30 min to mix thoroughly. The mixture was then placed in a high-pressure reactor and heated from room temperature to 150 °C for 6.5 h within 30 min. After the reaction was completed, the mixture was washed three times by centrifugation with ethanol-cyclohexane solution to obtain PdNi alloy nanoflowers.

[0057] (2) 10 mg of PdNi alloy nanoflowers and 60 mg of Ketjen Black ECP-600JD conductive carbon black powder (i.e. carbon support) were mixed in 15 mL of cyclohexane and ultrasonically dispersed for 1 hour to make the PdNi alloy nanoflowers uniformly deposited on the carbon support. After centrifugation and drying, the alloy catalyst containing carbon support was obtained.

[0058] Example 3

[0059] A method for preparing an alloy catalyst includes the following steps:

[0060] (1) 9 mL of octadecene, 0.5 mL of triethylenetetramine and 0.5 mL of m-phenylenediamine were successively added to a beaker and stirred thoroughly to form a composite solvent. Then, 20 mg of palladium acetylacetonate, 12 mg of nickel formate dihydrate and 50 mg of xylitol were added to the composite solvent. After stirring for 30 min to mix evenly, the mixture was placed in a high-pressure reactor and heated from room temperature to 180 °C for 6.5 h within 30 min. After the reaction was completed, the mixture was washed three times by centrifugation with ethanol-cyclohexane solution to obtain PdNi alloy nanoflowers.

[0061] (2) 10 mg of PdNi alloy nanoflowers and 50 mg of Ketjen Black ECP-600JD conductive carbon black powder (i.e. carbon support) were mixed in 15 mL of cyclohexane and ultrasonically dispersed for 1 hour to make the PdNi alloy nanoflowers uniformly deposited on the carbon support. After centrifugation and drying, the alloy catalyst containing carbon support was obtained.

[0062] Example 4

[0063] A method for preparing an alloy catalyst includes the following steps:

[0064] (1) 0.5 mL of octadecene, 9 mL of triethylenetetramine and 0.5 mL of m-phenylenediamine were successively added to a beaker and stirred thoroughly to form a composite solvent. Then, 20 mg of palladium acetylacetonate, 9 mg of nickel formate dihydrate and 70 mg of phloroglucinol were added to the composite solvent and stirred for 30 min to mix thoroughly. The mixture was then placed in a high-pressure reactor and heated from room temperature to 180 °C for 5 h within 30 min. After the reaction was completed, the mixture was repeatedly centrifuged and washed three times with ethanol-cyclohexane solution to obtain PdNi alloy nanoflowers.

[0065] (2) 10 mg of PdNi alloy nanoflowers and 65 mg of Ketjen Black ECP-600JD conductive carbon black powder (i.e. carbon support) were mixed in 15 mL of cyclohexane and ultrasonically dispersed for 1 hour to make the PdNi alloy nanoflowers uniformly deposited on the carbon support. After centrifugation and drying, the alloy catalyst containing carbon support was obtained.

[0066] Comparative Example 1

[0067] A method for preparing an alloy catalyst includes the following steps:

[0068] (1) 20 mg palladium acetylacetonate, 8 mg nickel formate dihydrate and 60 mg ascorbic acid were added to 10 mL triethylenetetramine solvent and stirred for 30 min to mix evenly. Then, the mixture was placed in a high-pressure reactor and heated from room temperature to 160 °C for 6 h within 30 min. After the reaction was completed, the PdNi alloy nanomaterial was obtained by repeated centrifugation and washing three times with ethanol-cyclohexane.

[0069] (2) 10 mg of PdNi alloy nanomaterial and 40 mg of Ketjen Black ECP-600JD conductive carbon black powder were mixed in 10 mL of cyclohexane solution, ultrasonically dispersed for 1 hour, and then separated by centrifugation and dried to obtain the alloy catalyst.

[0070] Comparative Example 2

[0071] A method for preparing an alloy catalyst includes the following steps:

[0072] (1) 5 mL of octadecene, 2 mL of triethylenetetramine and 3 mL of m-phenylenediamine were successively added to a beaker and stirred thoroughly to form a composite solvent. Then, 20 mg of palladium acetylacetonate, 8 mg of nickel formate dihydrate and 60 mg of phenol were added to the composite solvent and stirred for 30 min to mix thoroughly. The mixture was then placed in a high-pressure reactor and heated from room temperature to 160 °C for 6 h within 30 min. After the reaction was completed, the mixture was washed three times by centrifugation with ethanol-cyclohexane solution to obtain PdNi alloy nanomaterials.

[0073] (2) 10 mg of PdNi alloy nanomaterial and 40 mg of Ketjen Black ECP-600JD conductive carbon black powder (i.e. carbon support) were mixed in 10 mL of cyclohexane and ultrasonically dispersed for 1 hour to make PdNi alloy nanoflowers uniformly deposited on the carbon support. After centrifugation and drying, the alloy catalyst containing carbon support was obtained.

[0074] Comparative Example 3

[0075] Commercially available Premetek 20% Pd / C catalyst.

[0076] Product effectiveness test

[0077] 1. Microstructure of alloy catalysts

[0078] The alloy catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to microstructure testing using transmission electron microscopy.

[0079] Figure 1 This is a TEM image of the PdNi alloy nanoflowers prepared in Example 1. Figure 1 As can be seen, the alloy catalyst prepared in Example 1 has a uniform structure, exhibiting a three-dimensional nanoflower-like structure assembled from one-dimensional nanowires. The diameter of the nanowires is approximately 5 nm, and the diameter of the nanoflowers is approximately 35 nm. This unique three-dimensional structure reduces the stacking of nanoparticles, which is beneficial for the full exposure of palladium atoms, thereby improving the oxygen reduction performance of the alloy catalyst.

[0080] Figure 2 The image shows a TEM image of the PdNi alloy nanomaterial prepared in Comparative Example 1. Figure 2It is known that when no composite solvent and specific reducing agent are used, the alloy catalyst exhibits a solid nanoparticle structure with a diameter of 30 nm, which is not conducive to the exposure of catalytic active sites such as palladium atoms, and will also lead to a decrease in the electrochemical performance of the alloy catalyst.

[0081] Figure 3 The image shown is a TEM image of the PdNi alloy nanomaterial prepared in Comparative Example 2. Figure 3 It is known that when a composite solvent is used but no specific reducing agent is used, the alloy catalyst exhibits a solid nanoparticle structure with a diameter of 12 nm. Compared with the example, this is not conducive to the exposure of catalytic active sites such as palladium atoms, which will lead to a decrease in the electrochemical performance of the alloy catalyst.

[0082] Figure 4 Example 1: XRD pattern of PdNi alloy catalyst prepared from... Figure 4 ("Intensity" represents intensity, "2Theta" represents the diffraction angle 2θ, and "PdNi / C" represents the alloy catalyst of Example 1.) A broad diffraction peak can be seen at approximately 24°, corresponding to the (002) diffraction peak of carbon. The diffraction peaks at the remaining positions are consistent with the face-centered cubic structure of palladium, while no peaks related to nickel were observed, which may indicate that nickel may exist in solid solution or in an amorphous state.

[0083] 2. Electrochemical performance of alloy catalysts

[0084] 2.5 mg of the alloy catalysts from Examples 1 and 1-3 were respectively added to 1 mL of isopropanol and ultrasonically dispersed for 30 min to prepare ink solutions. 5 μL of each ink solution was drop-coated onto the surface of a glassy carbon electrode using a pipette. After air drying, these solutions served as working electrodes (i.e., glassy carbon electrodes coated with alloy catalysts). A three-electrode test system was constructed using a carbon rod as the counter electrode, a mercury / mercuric oxide electrode as the reference electrode, and the glassy carbon electrode coated with alloy catalysts as the working electrode. The electrolyte was a mixed solution of 0.5 mol methanol and 1 mol KOH. The methanol oxidation performance of the alloy catalysts was characterized using cyclic voltammetry, and the results are shown in Table 1.

[0085] Table 1

[0086]

[0087] As shown in Table 1, under the same noble metal loading, the alloy catalyst of Example 1 has significantly improved performance compared with the commercial Pd / C catalysts of Comparative Examples 1-2 and Comparative Example 3, indicating that the alloy catalyst prepared by the present invention has superior methanol oxygen reduction performance.

[0088] Moreover, Examples 2-4 all achieved similar effects to Example 1.

[0089] Obviously, the above embodiments are specific examples of the technical solutions of the present invention, and not limitations on the implementation methods. Those skilled in the art can make other changes without creative effort based on the above description. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing an alloy catalyst, characterized in that, The raw materials for preparing the alloy catalyst include a composite solvent, a metal precursor, and a reducing agent. The composite solvent includes octadecene, triethylenetetramine, and m-phenylenediamine. The reducing agent is selected from at least one of xylitol and phloroglucinol; The metal precursor includes palladium salts and non-palladium transition metal salts; The preparation method includes the following steps: Palladium salt, non-palladium transition metal salt and reducing agent are added to a composite solvent, mixed, heated to react, and then separated to obtain the alloy catalyst. The alloy catalyst comprises PdM alloy nanoflowers and a support, wherein the PdM alloy nanoflowers are loaded on the support, wherein M represents a non-palladium transition metal; the support is carbon; and the PdM alloy nanoflowers are three-dimensional nanoflowers.

2. The preparation method according to claim 1, characterized in that, M represents at least one of Fe, Co, Ni, and Cu.

3. The preparation method according to claim 1, characterized in that, In the PdM alloy nanoflowers, the molar ratio of Pd to M is (1-8):(1-5).

4. The preparation method according to claim 1, characterized in that, The PdM alloy nanoflowers are PdNi alloy nanoflowers.

5. The preparation method according to claim 1, characterized in that, In the composite solvent, the proportions of octadecene, triethylenetetramine, and m-phenylenediamine are each 5-90% by mass fraction.

6. The preparation method according to claim 1, characterized in that, The non-palladium transition metal salt is selected from at least one of iron salt, cobalt salt, nickel salt, and copper salt; and / or, the molar ratio of palladium to non-palladium transition metal in the metal precursor is (1-8):(1-5); and / or, the mass ratio of the metal precursor to the reducing agent is 28:(40-80).

7. An alcohol fuel cell, characterized in that, The alloy catalyst includes the preparation method described in any one of claims 1-6.

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