Application of surface partially embedded nanohigh-entropy structure catalyst

Abstract

The application relates to the technical field of electrochemical reaction catalysts, and discloses application of a surface partially embedded nano high-entropy structure catalyst. The preparation method steps are as follows: adding a ligand and a non-noble metal salt precursor into deionized water, uniformly stirring to form a solution; adding ammonia water into the solution, continuously stirring and then drying to obtain a dry gel; and self-combusting the dry gel at a high temperature of 250 DEG C or above to obtain the surface partially embedded nano high-entropy structure catalyst. The surface partially embedded non-noble metal nano high-entropy structure is synthesized through a sol-gel method coupled with a self-combustion method, and is applied to the field of electrocatalysis. Through the strong stability of the embedded interface limitation, high-entropy "cocktail" effect / lag diffusion effect, surface diffusion mass transfer and improvement of substrate adsorption and activation behavior, the electrocatalytic performance is improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical reaction catalyst technology, and in particular to the application of a surface-embedded nano-high-entropy structure catalyst. Background Technology

[0002] Fuel cell technology, with its superior fuel efficiency and smaller carbon footprint compared to internal combustion engines, has been widely recognized as a key solution for both mobile and stationary energy supply. Among these, proton exchange membrane fuel cells (PEMFCs) have achieved breakthroughs in commercial applications, such as their use in powertrain systems for automobiles and aircraft. However, their efficient hydrogen oxidation reaction (HOR) is still limited by the cost of platinum group metal (Pt)-based electrocatalysts and the durability of the catalytic structure. Therefore, the rational design of the active local structure of the HOR electrocatalyst to reduce the number of Pt, Pd, and other platinum group metal sites is crucial for hydrogen fuel cells, and it is essential to address the high potential dependence and structural stability issues arising from the desorption of hydrogen intermediates (H*) at a single active site. Furthermore, liquid fuels (methanol, ethanol, glycerol, and other polyols) offer higher volumetric energy density than hydrogen while being easy to handle, making them strong candidates for portable electricity and transportation applications besides hydrogen. In acidic environments, using alcohols as fuels can avoid the fuel permeation and severe carbonation problems associated with alkaline environments; however, these alcohol-based fuel cells suffer from slow reaction kinetics and low efficiency.

[0003] To address the aforementioned issues, current technologies primarily employ methods such as designing high-entropy alloy nanocatalysts and core-shell catalysts. For example, patent CN116364961B describes a core-shell catalyst with a high-entropy alloy core, a transition metal subshell encapsulating the high-entropy alloy core, and a platinum-rich outer shell encapsulating the transition metal subshell, applied to the oxygen reduction reaction in fuel cells. Patents CN120683390B and CN114566662B respectively introduce a platinum-based high-entropy intermetallic compound and a structurally ordered PtIrFeCoCu high-entropy alloy catalyst, used as cathode catalysts in hydrogen fuel cells. Patent CN104218249B yields a core-shell fuel cell anode catalyst supported on carbon nanotubes, with a gold shell and a core composed of any two metal alloys selected from copper, cobalt, nickel, zinc, and iron. However, current development of high-entropy catalysts remains focused on component selection and supported nanoparticles, which suffer from problems such as easy agglomeration and sintering during the reaction process, leading to a decrease in electrochemical active area and performance. Meanwhile, core-shell structures mainly focus on the construction of active shells, using traditional electronic / geometric structure control to improve performance, while neglecting surface mass transfer. Summary of the Invention

[0004] This invention aims to overcome the aforementioned problems in the prior art and provides an application of a surface-embedded high-entropy nanostructure catalyst. The surface-embedded non-precious metal high-entropy nanostructure is synthesized by a sol-gel method coupled with a self-combustion method, and then mixed with a platinum-carbon catalyst for application in the field of electrocatalysis. The electrocatalytic performance is improved through the strong stability of the embedded interface confinement, the high-entropy "cocktail" effect / retarded diffusion effect, surface diffusion mass transfer, and improved substrate adsorption and activation behavior.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The application of a surface-embedded nano-high-entropy structure catalyst, mixed with a platinum-carbon catalyst, in alcohol electro-oxidation or hydrogen electro-oxidation reactions; The preparation method of the surface-embedded nano-high-entropy structure catalyst includes the following steps: (1) Add the ligand and non-precious metal salt precursor to deionized water and stir until a solution is formed; (2) Add ammonia water to the solution, stir continuously, and then dry to obtain a dry gel; (3) The dry gel is self-combusted at a high temperature above 250°C to obtain the surface part embedded nano high entropy structure catalyst.

[0006] This invention employs a sol-gel method combined with a self-combustion method to synthesize non-noble metal high-entropy nanostructures partially embedded in nitrogen-doped carbon. Coordination is first formed through a sol-gel process, followed by the preferential deflagration of metal nitrates during self-combustion at the designated temperature. This deflagration drives the incomplete combustion of surrounding coordinated organic matter, forming a support nitrogen-doped carbon. Therefore, the metal salt preferentially nucleates, while the support formed by the ligands restricts further particle growth, resulting in an embedded structure. Finally, due to the high temperature of combustion, the carbon layer on the surface of the metal nanoparticles is oxidized and removed by calcination in air. The catalyst in this invention, when physically mixed with a traditional platinum-carbon catalyst, significantly enhances the performance of acidic alcohol electro-oxidation and hydrogenation reactions. High-entropy nanoparticles possess strong structural stability, including acid resistance due to hysteresis diffusion effects, and through the synergistic effect of the "cocktail" effect, the electronic structure enriched by electronic modulation and the geometric structure of surface distortion can improve acidic electro-oxidation performance. However, high-entropy nanoparticles are susceptible to surface migration leading to agglomeration and Ostwald ripening, resulting in decreased activity. Traditional core-shell structures can also lead to the loss of activity by encapsulating active sites. Therefore, this invention constructs a high-entropy nanostructure with only partial embedding of conductive support. This structure stabilizes itself through partial embedding of nanoparticles and achieves adsorption and activation of reactants through a dispersed distribution: First, the non-noble metal nanostructure catalyst with partial embedding on the surface improves the adsorption energy of hydrogen and alcohols (ethanol) based on multi-component synergistic effects or even a high-entropy "cocktail" effect, promoting substrate adsorption and activating intermediates under electrocatalysis; second, the intermediates migrate to platinum nanoparticle sites for subsequent reactions through long-range interactions such as interfacial mass transfer, reducing the poisoning effect of the intermediates. The advantage of the catalyst in this invention is that it improves the adsorption and activation of reaction substrates, lowers the reaction energy barrier, and rapidly renews active sites without interfering with the intrinsic performance of platinum nanoparticles (i.e., platinum-carbon catalysts), thereby improving the performance of acidic electrocatalysis of hydrogen and alcohols represented by ethanol, i.e., enhancing the anode performance of proton exchange membrane fuel cells.

[0007] To address the issues of insufficient activity and poor structural stability in the electro-oxidation of acidic alcohols, the catalyst of this invention offers the following advantages: 1. The non-noble metal high-entropy structure utilizes oxophilic non-noble metal oxides to achieve alcohol adsorption and activation, significantly increasing the surface concentration of alcohols and intermediates, and promoting the reaction through surface diffusion; 2. The high-entropy structure provides abundant component modulation space through rich electronic modulation and multiple active sites; 3. The separated platinum-high-entropy bifunctional active sites optimize the performance of alcohol electro-oxidation at different stages, and this embedded non-noble metal high-entropy nanostructure can also be extended to electro-oxidation reactions such as hydroxide oxidation; 4. The partially embedded structure on the surface can also achieve interfacial confinement stability of the high-entropy structure, resulting in strong structural stability.

[0008] Preferably, the mass ratio of platinum-carbon catalyst to surface-embedded nano-high-entropy structure catalyst is 0.3~1.5:1.

[0009] Preferably, the ligand in step (1) is selected from at least one of citric acid and EDTA; the non-precious metal salt precursor is selected from at least one of nitrates or chlorides of ferrous, cobalt, nickel, copper, tin, and chromium.

[0010] Preferably, the molar ratio of the ligand to the metal ion in the non-noble metal salt precursor in step (1) is 0.8 to 3:1.

[0011] Preferably, in step (2), ammonia is added to adjust the pH of the solution to 6-10.

[0012] Preferably, the drying temperature in step (2) is 60~90℃.

[0013] Preferably, the surface-embedded nano-high-entropy structure catalyst includes a nitrogen-doped carbon support and non-precious metal high-entropy nanoparticles; the surface portion of the non-precious metal high-entropy nanoparticles is embedded in the nitrogen-doped carbon support, but is not completely covered by the support.

[0014] Preferably, the particle size of the non-noble metal high-entropy nanoparticles is 2~6 nm.

[0015] Preferably, the nanostructure of the catalyst with the surface partially embedded high-entropy nanostructure is a two-dimensional sheet structure.

[0016] Therefore, the present invention has the following beneficial effects: (1) A variety of non-noble metal high-entropy nanostructures partially embedded in nitrogen-doped carbon were synthesized by sol-gel method + self-combustion method and successfully applied to HOR reaction under acidic environment and alcohol electro-oxidation with ethanol electro-oxidation reaction as model substrate. (2) By using non-noble metal nano-high-entropy structures embedded in the mixed surface, separate bifunctional active sites are constructed: each metal participates in the reaction uniquely during the coupling process as an active site for different sub-reactions. The high-entropy nano islands preferentially catalyze the adsorption and activation of reactants, while the platinum site metal promotes subsequent transformations. Molecular and electron release and transfer are achieved through surface diffusion, reducing the activation energy barrier and further promoting the improvement of catalytic performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the surface-embedded nano-high-entropy structure catalyst of the present invention; Among them, 1-non-noble metal high-entropy nanoparticles; 2-nitrogen-doped carbon support.

[0018] Figure 2 The FeCoNiCuSn@C obtained in Example 6 of this invention x N y TEM image of the catalyst.

[0019] Figure 3 The FeCoNiCuSn@C obtained in Example 6 of this invention x N y Elemental distribution of HAADF-TEM-EDS in the catalyst.

[0020] Figure 4 This is a graph showing the mass activity of the catalysts obtained in the embodiments and comparative examples of the present invention for the electro-oxidation of ethanol. Detailed Implementation

[0021] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0022] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0023] General Implementation Examples: A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure includes the following steps: (1) Add the ligand and non-precious metal salt precursor to deionized water and stir until a solution is formed; (2) Add ammonia water to the solution, stir continuously, and then dry to obtain a dry gel; (3) The dry gel was spontaneously combusted at a high temperature above 250°C to obtain the surface-embedded nano-high-entropy structure catalyst, the schematic diagram of which is shown below. Figure 1 As shown, it includes a nitrogen-doped carbon support 2 and non-precious metal high-entropy nanoparticles 1; the surface of the non-precious metal high-entropy nanoparticles is partially embedded in the nitrogen-doped carbon support, but is not completely covered by the support.

[0024] In one specific implementation, the ligand in step (1) is selected from at least one of citric acid and EDTA; the non-precious metal salt precursor is selected from at least one of ferrous, cobalt, nickel, copper, and tin nitrates or chlorides.

[0025] In one specific implementation, the molar ratio of the ligand to the metal ions in the non-precious metal salt precursor in step (1) is 0.8~3:1.

[0026] In one specific implementation, ammonia is added in step (2) to adjust the pH of the solution to 6-10.

[0027] In one specific implementation, the drying temperature in step (2) is 60~90℃.

[0028] Example 1:

[0029] A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure, comprising the following steps: (1) Add citric acid and copper nitrate hydrate to ultrapure water; in solution A, citric acid reacts with Cu 2+ The molar ratio is 1:1; (2) Slowly add ammonia water to solution A to adjust the pH value of the solution to 7, and continue stirring to form solution B; (3) Solution B was dried at 80 degrees Celsius to obtain dry gel C. Dry gel C was spontaneously combusted at 350 degrees Celsius to form a catalyst with partially embedded nano-high entropy structure on its surface, denoted as Cu@C. x N y .

[0030] Example 2:

[0031] A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure, comprising the following steps: (1) Add citric acid, copper nitrate hydrate, and cobalt nitrate hydrate to ultrapure water, stir and dissolve evenly to form solution A; in solution A, citric acid and Cu 2+ Co 2+ The molar ratio is 1:0.5:0.5; (2) Slowly add ammonia water to solution A to adjust the pH value of the solution to 7, and continue stirring to form solution B; (3) Solution B was dried at 80 degrees Celsius to obtain dry gel C. Dry gel C was spontaneously combusted at 350 degrees Celsius to form a catalyst with partially embedded nano-high entropy structure on its surface, denoted as CuCo@C. x N y .

[0032] Example 3:

[0033] A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure, comprising the following steps: (1) Add citric acid, copper nitrate hydrate, cobalt nitrate hydrate, and nickel nitrate to ultrapure water, stir and dissolve evenly to form solution A; in solution A, citric acid and Cu 2+ Co 2+ Ni 2+ The molar ratio is 1:0.33:0.33:0.33; (2) Slowly add ammonia water to solution A to adjust the pH value of the solution to 7, and continue stirring to form solution B; (3) Solution B was dried at 80 degrees Celsius to obtain dry gel C. Dry gel C was spontaneously combusted at 350 degrees Celsius to form a surface-embedded nano-high-entropy catalyst, denoted as CuCoNi@C. x N y .

[0034] Example 4:

[0035] A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure, comprising the following steps: (1) Add citric acid, copper nitrate hydrate, cobalt nitrate hydrate, and chromium nitrate hydrate to ultrapure water, stir and dissolve evenly to form solution A; in solution A, citric acid reacts with Cu 2+ Co 2+ Cr 3+ The molar ratio is 1:0.33:0.33:0.33; (2) Slowly add ammonia water to solution A to adjust the pH value of the solution to 7, and continue stirring to form solution B; (3) Solution B was dried at 80 degrees Celsius to obtain dry gel C. Dry gel C was spontaneously combusted at 350 degrees Celsius to form a surface-embedded nano-high-entropy structure catalyst, denoted as CuCoCr@C. x N y .

[0036] Example 5:

[0037] A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure, comprising the following steps: (1) Add citric acid, copper nitrate hydrate, cobalt nitrate hydrate, nickel nitrate, and ferric chloride to ultrapure water, stir until dissolved to form solution A; in solution A, citric acid reacts with Cu 2+ Co 2+ Ni 2+ Fe 3+ The molar ratio is 1:0.25:0.25:0.25; (2) Slowly add ammonia water to solution A to adjust the pH value of the solution to 7, and continue stirring to form solution B; (3) Solution B was dried at 80 degrees Celsius to obtain dry gel C. Dry gel C was spontaneously combusted at 350 degrees Celsius to form a surface-embedded nano-high-entropy structure catalyst, denoted as FeCoNiCu@C. x N y .

[0038] Example 6:

[0039] A method for preparing a catalyst with a surface partially embedded nanostructured high-entropy structure, comprising the following steps: (1) Add citric acid, copper nitrate hydrate, cobalt nitrate hydrate, nickel nitrate, ferric chloride, and tin tetrachloride to ultrapure water, stir until dissolved to form solution A; in solution A, citric acid reacts with Cu 2+ Co 2+ Ni 2+ Fe 3+ Sn2+ The molar ratio is 1:0.2:0.2:0.2:0.2:0.2; (2) Slowly add ammonia water to solution A to adjust the pH value of the solution to 7, and continue stirring to form solution B; (3) Solution B was dried at 80 degrees Celsius to obtain dry gel C. Dry gel C was spontaneously combusted at 350 degrees Celsius to form a surface-embedded nano-high-entropy structure catalyst, denoted as FeCoNiCuSn@C. x N y Its TEM image and elemental distribution are as follows Figure 2 and Figure 3 As shown, from Figure 2 As can be seen from the above, the catalyst obtained by the present invention has a surface-embedded structure.

[0040] Comparative Example 1 (Coated FeCoNiCuSn@C x N y ): A method for preparing a coated nano-high-entropy structure catalyst, comprising the following steps: (1) Dissolve ferrous sulfate, cobalt sulfate, nickel sulfate, copper sulfate and stannous sulfate in dilute sulfuric acid in equal proportions (ultrasound for 1 min), and dissolve 2,2'-bipyridine in ethanol (ultrasound), with the molar ratio of 2,2'-bipyridine to total metals being 1:1; mix the two solutions and stir overnight. (2) Add the above solution to ethanol, add carbon support (Vulcan XC-72 carbon black), and then sonicate and stir the reaction. (3) Powder A was obtained by rotary evaporation at 45℃, overnight drying at 45℃, and then grinding. (4) Powder A was calcined in a N2 atmosphere at 800℃ for 3 hours to obtain coated FeCoNiCuSn@C x N y The FeCoNiCuSn nanoparticles have a nitrogen-doped carbon shell in close contact on their surface.

[0041] Application Example 1: The catalysts obtained in the above examples and comparative examples were mixed with the platinum-carbon catalyst at a mass ratio of 1:1 and ground uniformly to obtain a mixed catalyst. The mixed catalyst was ultrasonically dispersed in a mixed solvent of isopropanol and water (volume ratio 1:1), and 20 μL of 5% Nafion solution was added. After ultrasonic dispersion, the mixture was drop-coated onto a platinum-carbon electrode for electrochemical testing. The test results are as follows: Figure 4 As shown in the figure. Test environment: 0.1 mol / L perchloric acid solution containing 0.5 mol / L ethanol.

[0042] The preparation method of the platinum-carbon catalyst is as follows: (1) Add an ethanol solution containing chloroplatinic acid hexahydrate (catalyst Pt loading is 20wt%) to carbon black while sonicating to form mixture A; (2) Mixture A is stirred thoroughly for 2 hours to form mixture B; (3) Mixture B was dried and ground at 80 degrees Celsius, and then reduced at 300 degrees Celsius for 2 hours in a 10wt% hydrogen atmosphere to obtain a platinum-carbon catalyst.

[0043] In Examples 1-6, the method of this invention is used. Coordination is first formed through a gel sol, and then, during self-combustion, the metal nitrate preferentially undergoes deflagration upon reaching the designated temperature, leading to the incomplete combustion of surrounding coordinated organic matter and forming a nitrogen-doped carbon support. Therefore, the metal salt preferentially nucleates, while the support formed by the ligands restricts further particle growth, resulting in an embedded structure. Finally, due to the high temperature of combustion, the carbon layer on the surface of the metal nanoparticles is oxidized and removed during calcination in a muffle furnace (in the presence of air), ultimately yielding a non-noble metal nanostructured high-entropy catalyst with a partially embedded surface. In contrast, Comparative Example 1 uses a template method for coating, and the carbon layer is formed through high-temperature calcination in an inert atmosphere via pyrolysis of organic matter, resulting in the coating of active particles. However, the construction of a tightly contacted shell confines the nanoparticles within the shell, hindering contact with the reactants. Figure 4 As can be seen from the examples, the surface-embedded non-precious metal nanostructured catalysts prepared by the method of this invention in Examples 1-6, when used in combination with the platinum-carbon catalyst, can significantly improve the mass activity of ethanol electro-oxidation of Pt. However, when the coated catalyst prepared in Comparative Example 1 is used in combination with the platinum-carbon catalyst, it cannot effectively contact the activation sites of organic molecules, resulting in no performance improvement or even a slight decrease. This may be due to the reduction in the overall conductivity of the catalyst.

[0044] Application Example 2: The FeCoNiCuSn@C obtained in Example 6 above x N y The catalyst and platinum-carbon catalyst were mixed and ground uniformly at a mass ratio of 1:1 to obtain a mixed catalyst. The mixed catalyst was ultrasonically dispersed in a mixed solvent of isopropanol and water (volume ratio 1:1), and 20 μL of 5% Nafion solution was added. After ultrasonic dispersion, the mixture was drop-coated onto a rotating disk electrode for electrochemical testing at a rotation speed of 1600 rpm. The test environment was a 0.1 mol / L perchloric acid solution saturated with H2. The test results are shown in Table 1.

[0045] The preparation method of the platinum-carbon catalyst is as follows: (1) Add an ethanol solution containing chloroplatinic acid hexahydrate (catalyst Pt loading is 20wt%) to carbon black while sonicating to form mixture A; (2) Mixture A is stirred thoroughly for 2 hours to form mixture B; (3) Mixture B was dried and ground at 80 degrees Celsius, and then reduced at 300 degrees Celsius for 2 hours in a 10wt% hydrogen atmosphere to obtain a platinum-carbon catalyst.

[0046] Table 1: Results of Hydroxylation Activity Test

[0047] As can be seen from Table 1, the surface-embedded nano-high-entropy structure catalyst prepared by the present invention can effectively improve the hydrogenation activity.

[0048] It should be noted that the specific implementation methods described above provide a detailed explanation of the technical solution and application results of the present invention. The above embodiments are only the most preferred embodiments and are not intended to limit the present invention. Modifications or equivalent substitutions made by those skilled in the art within the core theoretical scope of the present invention should all fall within the protection scope of the present invention.

Claims

1. The application of a surface-embedded nano-high-entropy structure catalyst, characterized in that, When mixed with a platinum-carbon catalyst, it is applied to alcohol electro-oxidation or hydrogen electro-oxidation reactions; the surface-embedded nano-high-entropy structure catalyst includes a nitrogen-doped carbon support and non-precious metal high-entropy nanoparticles; the surface portion of the non-precious metal high-entropy nanoparticles is embedded in the nitrogen-doped carbon support, but is not completely covered by the support; The preparation method of the surface-embedded nano-high-entropy structure catalyst includes the following steps: (1) Add the ligand and non-precious metal salt precursor to deionized water and stir until homogeneous to form a solution; the ligand is selected from at least one of citric acid and EDTA; (2) Add ammonia water to the solution, stir continuously, and then dry to obtain a dry gel; (3) The dry gel is spontaneously combusted at a high temperature above 250°C in air to obtain the surface part embedded nano high entropy structure catalyst.

2. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1, characterized in that, The mass ratio of platinum-carbon catalyst to surface-embedded nano-high-entropy structure catalyst is 0.3~1.5:

1.

3. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1, characterized in that, The non-precious metal salt precursor mentioned in step (1) is selected from at least one of the nitrates or chlorides of ferrous, iron, cobalt, nickel, copper, tin, and chromium.

4. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1 or 3, characterized in that, In step (1), the molar ratio of the ligand to the metal ion in the non-noble metal salt precursor is 0.8 to 3:

1.

5. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1, characterized in that, In step (2), ammonia water is added to adjust the pH of the solution to 6-10.

6. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1, characterized in that, The drying temperature in step (2) is 60~90℃.

7. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1, characterized in that, The particle size of the non-precious metal high-entropy nanoparticles is 2~6nm.

8. The application of the surface-embedded nano-high-entropy structure catalyst according to claim 1, characterized in that, The surface-embedded nano-high-entropy structure catalyst has a two-dimensional sheet-like nanostructure.

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