A nitrogen-doped carbon supported high-entropy alloy nanoparticle electrocatalyst, a preparation method and application thereof

Abstract

A nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst, its preparation method, and its application are disclosed. The catalyst uses nitrogen-doped carbon as a support, on which high-entropy alloy nanoparticles, a single-phase solid solution formed by five metal elements—platinum, copper, iron, cobalt, and nickel—are loaded. The preparation method mainly includes: first, preparing the nitrogen-doped carbon support; then, mixing it with a metal salt precursor and drying it; finally, subjecting the mixture to instantaneous high-temperature thermal shock treatment using Joule heating technology, which forces the various metal atoms to dissolve mutually during ultra-rapid heating and cooling, forming a homogeneous alloy that is firmly loaded onto the support. This method effectively solves the problems of easy phase separation, long cycle, and easy agglomeration of nanoparticles in traditional high-entropy alloy synthesis. The prepared catalyst exhibits excellent catalytic activity in the electrochemical hydrogen evolution reaction, reaching 10 mA / cm² under acidic conditions, for example. 2 The required current density is only 13 mV overpotential. This invention offers a simple and efficient process, providing a new approach for the preparation of high-performance, low-cost electrocatalysts.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials technology, specifically relating to a nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst, its preparation method, and its application in the electrochemical hydrogen evolution reaction (HER). Background Technology

[0002] The transformation of the global energy structure and the urgent need for environmental protection are driving the rapid development of clean and sustainable energy technologies. Hydrogen energy, as an ideal secondary energy carrier with high energy density and zero carbon emissions, is considered an important component of the future energy system. Large-scale production of green hydrogen through water electrolysis is one of the key pathways to realizing the industrialization of hydrogen energy, and the efficiency and economic viability of this technology hinge on the performance of the electrocatalyst for the hydrogen evolution reaction. Currently, platinum-based catalysts are widely recognized as having the best intrinsic activity for the hydrogen evolution reaction in acidic media. However, the extremely low abundance of platinum in the Earth's crust and its extremely high price severely restrict its widespread application in large-scale water electrolysis plants. Furthermore, the stability of platinum-based catalysts under long-term operating conditions still needs improvement; their active sites are prone to migration, aggregation, or loss during the reaction, leading to catalytic performance degradation. Therefore, developing novel electrocatalysts that combine high activity and high stability while significantly reducing the amount of precious metals used is a core issue in promoting the practical application of water electrolysis hydrogen production technology.

[0003] In recent years, high-entropy alloys, as an emerging multi-principal-element alloy material, have shown great potential in the field of catalysis. Their unique compositional characteristics bring about high-entropy effects, severe lattice distortion, slow diffusion effects, and the so-called cocktail effect, providing ample space for controlling the electronic structure and surface adsorption energy of the material, and potentially breaking the trade-off between activity and stability inherent in traditional binary or ternary alloys. Theoretically, high-entropy alloy nanoparticles composed of multiple transition metals and a small amount of noble metals can achieve catalytic performance exceeding that of single metals or simple alloys by significantly reducing the amount of noble metals used, through the synergistic effect between the components. However, translating this theoretical advantage into practically usable high-performance catalysts still faces a series of severe synthetic scientific challenges. Traditional alloy preparation methods, such as arc melting and mechanical ball milling, typically require prolonged high-temperature treatment to obtain a homogeneous phase. However, the lengthy heat treatment process easily leads to elemental segregation and phase separation, making it difficult to obtain a single-phase solid solution with uniform composition at the atomic scale. While conventional wet chemical methods or tubular furnace pyrolysis can prepare nanoparticles, achieving uniform alloying of up to five or more metallic elements at the nanoscale is challenging. Furthermore, the nanoparticles are prone to Ostwald ripening and severe agglomeration, leading to a sharp decrease in the active specific surface area. Additionally, firmly anchoring the generated high-entropy alloy nanoparticles onto supports with high conductivity and large specific surface area to enhance electron conduction, prevent particle migration, and optimize mass transfer remains a key technical challenge. Nitrogen-doped carbon materials are considered ideal catalyst supports due to their excellent conductivity, chemical stability, and abundant nitrogen anchoring sites; however, achieving uniform loading and robust bonding of high-entropy alloy nanoparticles on them remains difficult. Existing technologies often suffer from complex processes, long synthesis cycles, high energy consumption, or poor product uniformity, hindering the controllable synthesis and large-scale preparation of such high-performance catalysts. Therefore, there is an urgent need to develop an efficient, rapid, and universal synthesis strategy to overcome these bottlenecks and prepare nitrogen-doped carbon-supported high-entropy alloy electrocatalysts with well-defined structures, uniform composition, and good dispersion. Summary of the Invention

[0004] Technical Problem Solved: This invention aims to provide a nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst, its preparation method, and its application. Uniform single-phase high-entropy alloy nanoparticles of nitrogen-doped carbon (Pt, Cu, Fe, Co, Ni) are synthesized via Joule heating. The instantaneous high temperature during Joule heating causes severe lattice distortion in the metals, generating a large number of low-coordination active sites, which is beneficial for the adsorption and desorption of hydrogen ions (HER). The high dispersion of the five metal elements at the atomic scale produces a synergistic catalytic effect, significantly reducing the overpotential of HER.

[0005] Technical solution: A method for preparing a nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst, comprising the following steps: (1) reacting 2-methylimidazole with zinc salt in methanol, centrifuging and drying to obtain ZIF-8 precursor, and then carbonizing under an inert atmosphere to obtain a nitrogen-doped porous carbon support; (2) mixing and stirring the nitrogen-doped porous carbon support obtained in step (1) with metal salts containing platinum, copper, iron, cobalt and nickel in an organic solvent, and then evaporating to remove the solvent to obtain a mixture of metal precursors; (3) placing the mixture obtained in step (2) on a conductive support, and under an inert atmosphere, performing Joule heating treatment by applying a pulse current, wherein the single pulse time of the Joule heating treatment is 0.05s-1s, so that different combinations of metal element components are alloyed and loaded on the nitrogen-doped porous carbon support to obtain the nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst.

[0006] The carbonization temperature in step (1) is 1000℃ and the holding time is 3 hours; the zinc salt is zinc nitrate.

[0007] The metal salt mentioned in step (2) is acetylacetone salt; the organic solvent is acetone; and the molar ratio of the metal elements platinum, copper, iron, cobalt and nickel is (1-4):1:1:1:1.

[0008] The molar ratio of the metal elements platinum, copper, iron, cobalt and nickel is 2:1:1:1:1.

[0009] The peak temperature of the Joule heating treatment in step (3) is 1000℃ to 1400℃.

[0010] The number of thermal shocks in the Joule heating treatment in step (3) is 3 to 10.

[0011] The conductive carrier mentioned in step (3) is one of graphite tube, graphite boat, graphite paper, graphite felt or graphite sheet.

[0012] The nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst prepared by the above method comprises a nitrogen-doped carbon support and high-entropy alloy nanoparticles supported thereon. The high-entropy alloy comprises five metal elements: platinum, copper, iron, cobalt, and nickel, and forms a single-phase solid solution structure.

[0013] The average particle size of the above-mentioned high-entropy alloy nanoparticles is 5 nanometers, and they are uniformly dispersed on the surface of the nitrogen-doped carbon support.

[0014] The above-mentioned nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalysts are applied in the electrochemical hydrogen evolution reaction.

[0015] Invention Principle: Utilizing the ultrafast heating rate (e.g., 1500℃ / s) and extremely short isothermal time (e.g., 0.1s) provided by Joule heating technology, a rapid high-temperature thermal shock is applied to precursors of various metal salts, including platinum, copper, iron, cobalt, and nickel, supported on a nitrogen-doped carbon support. This process forces different metal atoms to undergo forced mutual dissolution under extreme non-equilibrium conditions, effectively suppressing the phase separation tendency caused by differences in the mixing enthalpy of each element, thereby forming atomically homogeneous single-phase solid solution high-entropy alloy nanoparticles. Simultaneously, the rapid high-temperature and quenching process introduces severe lattice distortion into the alloy lattice, generating a large number of low-coordination active sites, optimizing the adsorption / desorption energy for hydrogen intermediates; the nitrogen-doped carbon support provides a conductive network and anchoring points, inhibiting nanoparticle aggregation, ultimately achieving a synergistic balance between high activity and high stability of the catalyst in the hydrogen evolution reaction.

[0016] Beneficial Effects: This invention utilizes the Joule heating reaction to provide an ultrafast heating rate of 1500℃·s and an extreme isothermal time of 0.1 s, forcing the five components Pt, Cu, Fe, Co, and Ni to achieve forced miscibility at the atomic scale. This effectively solves the problems of component segregation and phase separation caused by the enthalpy difference in metal mixing in traditional heat treatment processes, ensuring that the catalyst has a highly uniform single-phase solid solution structure. Through instantaneous thermal shock treatment at 1200℃, this invention induces a severe lattice distortion effect within the high-entropy alloy nanoparticles. This distortion not only changes the coordination state of surface atoms but also generates a large number of low-coordination unsaturated sites, greatly enhancing the adsorption and desorption kinetics of the reaction intermediate *H, thus fundamentally improving the intrinsic activity of the catalyst. It significantly reduces the overpotential of the hydrogen evolution reaction (HER). Through the electronic synergistic effect of the high-entropy components and the NC anchoring effect of the support, the catalyst prepared by this invention exhibits excellent catalytic performance. In acidic electrolytes, this catalyst achieves a reaction rate of 10 mA / cm². 2 The overpotential is 13 mV at 100 mA / cm 2 The overpotential is 108 mV. This performance is significantly better than most reported Pt-based alloy catalysts. The preparation process of this invention is simple, requiring only millisecond-level thermal pulses for the conversion from metal salt to the target alloy catalyst. Compared with traditional metallurgical or heat treatment methods, this greatly reduces energy and time costs, providing a new process route for the large-scale, standardized preparation of high-performance, low-precious-metal electrocatalysts. Attached Figure Description

[0017] Figure 1The catalyst prepared in Example 1 is uniformly distributed on dodecahedral carbon-doped carbon without obvious agglomeration, with an average particle size of about 5 nm. (a) It can be seen that a large number of dodecahedral carbon substrates maintain complete geometric structure, the catalyst support is uniform in size, and exhibits good dispersibility; (b) The adhesion of Pt2CuFeCoNi nanoparticles to the dodecahedral carbon surface is clearly shown, and the fine alloy particles are anchored on the support surface with high density and uniformity; (c) Further magnification of a single dodecahedral structure confirms that there is a strong interaction between the high-entropy alloy and the nitrogen-doped carbon support, and such a structure helps to expose more active sites; (d) Statistical analysis of a large number of particles confirms that its narrow diameter distribution characteristics (average about 5 nm) and this size effect promote the hydrogen evolution reaction activity.

[0018] Figure 2 SEM images of the catalyst prepared by the conventional tube furnace in Comparative Example 1 are shown. (a) It can be seen that the dodecahedral structure of the carbon support is preserved, but the distribution of the metal material loaded on the surface is extremely uneven, and obvious metal agglomerates appear locally; (b) The metal particles show severe thermal agglomeration, with an average particle size of more than ten nanometers, and the particle shape is no longer regular.

[0019] Figure 3 To compare PtCuFeCoNi / NC catalysts with different feed ratios and different Joule heat treatments using XRD, it was found that (a) when the Pt content and total transition metal content were 1:2, only two main diffraction peaks belonging to the alloy phase were observed (located at approximately 42° and 49°), and no impurity peaks belonging to elemental metals or other metal compounds were observed, proving that the five metals achieved a high degree of mixing and formed a single-phase alloy. The half-width of the diffraction peak of Pt2CuFeCoNi / NC was significantly larger than that of other components, and the average grain size of this component was significantly reduced, which was attributed to the severe lattice distortion effect of the high-entropy alloy and the inhibition of grain growth by the Joule heat ultrafast quenching process. Transition metals are doped into the Pt lattice, and phase separation occurs as the Pt content decreases. As shown in (b), when the thermal shock temperature is 1000℃, the diffraction peaks of the sample are diffuse and have low intensity, making it difficult to obtain a high-entropy alloy phase with high catalytic activity; when the temperature is too high (1400℃), the diffraction peaks become significantly sharper, indicating that the high temperature leads to the intense sintering and agglomeration of the active nanoparticle components, and the synthesized high-entropy alloy will exhibit phase separation.

[0020] Figure 4 The following are polarization curves for the embodiments and control groups of the present invention. In (a), the polarization of Pt2CuFeCoNi / NC-1200℃ (red curve) is at 10 mA / cm. 2 The overpotential is 13 mV at 100 mA / cm 2The overpotential was 108 mV, indicating that the catalyst has good electrocatalytic hydrogen evolution activity; (b) Compared with nitrogen-doped carbon-supported high-entropy alloy nanoparticles with different metal element combinations, after replacing Ni with Mo (black curve) or V (blue curve), the polarization curve shifted significantly to the left, the overpotential increased significantly, and the catalytic activity decreased; when Ce component was introduced (green curve), the polarization curve had the lowest slope and the worst performance. Detailed Implementation

[0021] The following description, in conjunction with embodiments, further illustrates this experiment to enable those skilled in the art to better understand and implement the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example 1: Preparation of the optimal ratio of Pt2CuFeCoNi / NC

[0023] (1) Weigh 1.19 g of zinc nitrate and 2.65 g of 2-methylimidazole and dissolve them in 40 mL of methanol reagent. Sonicate for 30 min until completely dissolved. Add the obtained 2-methylimidazole solution dropwise to the zinc nitrate solution. After stirring at room temperature for 24 h, the solution changes from colorless to white. After washing three times with methanol by centrifugation, dry under vacuum at 60 °C to obtain ZIF-8.

[0024] (2) The obtained ZIF-8 precursor was placed in a tube furnace and heated to 1000℃ at a rate of 5℃ / min under an argon atmosphere and held for 2 h. After cooling to room temperature, a nitrogen-doped porous carbon support with high specific surface area and abundant nitrogen sites was obtained, denoted as NC.

[0025] (3) Loading of metal precursors: The above NC support was weighed and dispersed in acetone, and the corresponding acetylacetone salts were added according to the molar ratio of Pt:Cu:Fe:Co:Ni of 2:1:1:1:1. The mixture was stirred continuously at room temperature for 24 h to fully absorb metal ions by utilizing the pore structure of NC and the chelating effect of nitrogen sites. Then, the acetone was evaporated to dryness at 50 °C.

[0026] (4) Joule heating treatment: The mixed precursor was placed in the reaction chamber of a Joule furnace. Under an inert atmosphere, the sample was instantaneously heated to 1200℃ by adjusting the pulse current. The thermal shock program was set as follows: the single pulse time was 0.1 s, and the thermal shock was repeated 5 times. During this ultrafast heating and cooling process, the five metal atoms migrated rapidly on the NC surface and dissolved in situ, finally obtaining an electrocatalyst supported on Pt2CuFeCoNi / NC high-entropy alloy nanoparticles with uniform particle size distribution and high dispersion.

[0027] The catalyst was tested using an electrochemical workstation at 10 mA / cm². 2 The overpotential is 13 mV at 100 mA / cm 2 The overpotential is 108 mV. Example 1 ( Figure 1 The prepared catalyst is uniformly distributed on carbon-doped dodecahedrons with an average particle size of about 5 nm. XRD images show that Pt2CuFeCoNi is a single-phase high-entropy alloy without obvious phase separation.

[0028] Examples 2-5: Experiments with different mixing ratios

[0029] The atomic ratios of Pt, Cu, Fe, Co, and Ni were changed to 1:1:1:1:1, 2:1:1:1:1, 3:1:1:1:1, and 4:1:1:1:1, with the remaining processes the same as in Example 1. Test results showed that the electrochemical activity decreased to varying degrees after deviating from the 2:1:1:1:1 ratio.

[0030] Comparative Example 1: Heat treatment using a traditional tubular furnace

[0031] The remaining preparation parameters were exactly the same as in Example 1, except that the Joule heat treatment temperature in step (3) was changed to placing the dried mixed precursor in a conventional tube furnace and heating it at 5°C·min under an Ar atmosphere. -1 The sample was heated to 1200℃ at a heating rate and held at that temperature for 2 hours. As shown in Figure (2), the nanoparticles in the sample agglomerated, with the particles reaching tens of nanometers in size. They failed to form a uniform high-entropy alloy solid solution phase, and the HER activity was much lower than that in Example 1.

[0032] Comparative Example 2: Changing the combination of metallic elements that form high-entropy alloys

[0033] The preparation parameters were identical to those in Example 1, except that the molar ratio of Pt;Cu;Fe;Co;Ni in step (3) was changed from 2:1:1:1:1 to the corresponding proportions of Pt;Cu;Fe;Co;Mo, Pt;Cu;Fe;Co;V, and Pt;Cu;Fe;Co;Ce. The electrochemical performance of the synthesized catalyst was studied, and the results are as follows: Figure 4As shown in (b), Pt2CuFeCoNi / NC (red curve) exhibits the most significant HER catalytic activity. Replacing Ni with Mo (black curve) or V (blue curve) causes a significant leftward shift in the polarization curve, a substantial increase in overpotential, and a decrease in catalytic activity. When Ce component is introduced (green curve), the polarization curve has the lowest slope, resulting in the worst performance. The introduction of Ni atoms plays a crucial role in optimizing the electronic structure of the Pt center. The strong electronic coupling effect between Pt and Ni significantly reduces the adsorption energy barrier of the hydrogen intermediate (*H). This specific metal synergistic effect is difficult to replace with other elements.

[0034] Comparative Example 3: Changing the temperature of the Joule furnace heat treatment

[0035] The preparation parameters were identical to those in Example 1, except that the Joule heat treatment in step (4) was changed from instantaneously heating the sample to 1200℃ to instantaneously heating it to 1000℃ and 1400℃, with a single thermal shock of 0.1 s and 5 thermal shocks. The synthesized samples were designated as Pt2CuFeCoNi / NC-1000℃ and Pt2CuFeCoNi / NC-1400℃, respectively. XRD and electrochemical tests were performed on the three synthesized catalysts, and the results are as follows: Figure 3 As shown in (b), when the thermal shock temperature is 1000℃, the diffraction peaks of the sample are diffuse and have low intensity, indicating that the energy input is insufficient to allow the multi-component metal atoms to achieve sufficient solid solution, making it difficult to obtain a high-entropy alloy phase with high catalytic activity. At excessively high temperatures (1400℃), the diffraction peaks become significantly sharper, indicating that the high temperature leads to severe sintering and agglomeration of the active nanoparticle components, but significantly reduces the specific surface area and catalytic activity. All synthesized high-entropy alloys exhibit phase separation, and their hydrogen evolution activity decreases significantly.

[0036] Those skilled in the art should understand that various equivalent substitutions or modifications can be made to the above specific embodiments without departing from the spirit and essence of the present invention, and all such substitutions or modifications fall within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst, characterized in that, Includes the following steps: (1) 2-methylimidazole and zinc salt were reacted in methanol, and ZIF-8 precursor was obtained by centrifugation and drying. Then, carbonization was carried out under an inert atmosphere to obtain nitrogen-doped porous carbon support; (2) The nitrogen-doped porous carbon support obtained in step (1) was mixed and stirred with metal salts containing platinum, copper, iron, cobalt and nickel in an organic solvent. Then, the solvent was evaporated to remove the solvent to obtain a mixture of metal precursors; (3) The mixture obtained in step (2) was placed on a conductive support and Joule heating was carried out by applying a pulse current under an inert atmosphere. The single pulse time of the Joule heating was 0.05s-1s, so that the metal element components of different combinations were alloyed and loaded on the nitrogen-doped porous carbon support to obtain the nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst.

2. The preparation method according to claim 1, characterized in that, The carbonization temperature in step (1) is 1000℃ and the holding time is 3 hours; the zinc salt is zinc nitrate.

3. The preparation method according to claim 1, characterized in that, The metal salt mentioned in step (2) is acetylacetone salt; the organic solvent is acetone; and the molar ratio of the metal elements platinum, copper, iron, cobalt and nickel is (1-4):1:1:1:

1.

4. The preparation method according to claim 3, characterized in that, The molar ratio of the metal elements platinum, copper, iron, cobalt and nickel is 2:1:1:1:

1.

5. The preparation method according to claim 1, characterized in that, The peak temperature of the Joule heating treatment in step (3) is 1000℃ to 1400℃.

6. The preparation method according to claim 1, characterized in that, The number of thermal shocks in the Joule heating treatment in step (3) is 3 to 10.

7. The preparation method according to claim 1, characterized in that, The conductive carrier mentioned in step (3) is one of graphite tube, graphite boat, graphite paper, graphite felt or graphite sheet.

8. The nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst prepared by any one of the preparation methods described in claims 1-7, characterized in that, The catalyst comprises a nitrogen-doped carbon support and high-entropy alloy nanoparticles supported thereon. The high-entropy alloy comprises five metallic elements: platinum, copper, iron, cobalt, and nickel, forming a single-phase solid solution structure.

9. The nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst according to claim 8, characterized in that, The high-entropy alloy nanoparticles have an average particle size of 5 nanometers and are uniformly dispersed on the surface of the nitrogen-doped carbon support.

10. The application of the nitrogen-doped carbon-supported high-entropy alloy nanoparticle electrocatalyst according to claim 8 or 9 in the electrochemical hydrogen evolution reaction.

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