Medium-entropy catalyst based on self-reduction strategy as well as preparation method and application of medium-entropy catalyst
By preparing a medium-entropy catalyst through a self-reduction strategy, the problem of insufficient active sites in existing catalysts was solved, and a highly efficient electrochemical nitrate reduction to ammonia synthesis reaction was achieved. This catalyst exhibits excellent catalytic performance and stability and has broad application prospects.
Patent Information
- Application Number
- CN202511668454.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-02-06
AI Technical Summary
In existing technologies, single metal and traditional binary alloy catalysts have a limited number of active sites and low electron conduction efficiency in the electrochemical nitrate reduction to ammonia synthesis reaction. They are difficult to simultaneously address reactant adsorption, intermediate conversion, and product desorption, resulting in poor reaction selectivity and Faraday efficiency that cannot meet the needs of practical applications. Furthermore, multi-principal alloy catalysts are costly and have poor controllability.
A self-reduction strategy was adopted to prepare medium-entropy catalysts. By synergistically regulating the electronic structure of multiple elements, the adsorption/desorption behavior of reaction intermediates was optimized. Cu and non-Cu metals were deposited on a foamed iron substrate using an entropy increase strategy to form medium-entropy catalysts such as Fe-Cu-Ni, Fe-Cu-Co, Fe-Cu-Sn, Fe-Cu-Ag, and Fe-Cu-Bi, thereby realizing the entropy increase process of the materials.
The prepared medium-entropy catalyst provides abundant active sites in the electrochemical synthesis of ammonia, with a Faraday efficiency of up to 98.74% and a yield of up to 19.56 mg·h-1·cm-2. It has good stability and is suitable for electrocatalysis fields such as nitrate electroreduction, CO2 reduction, nitrogen reduction, water electrolysis for hydrogen production and organic synthesis, with good catalytic effect and economic benefits.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, specifically relating to a medium-entropy catalyst based on a self-reduction strategy, its preparation method, and its application. Background Technology
[0002] With the global energy crisis and environmental pollution becoming increasingly severe, the development of efficient and sustainable energy conversion and storage technologies has become a top priority in current research. Electrocatalysis technology is particularly important because it can convert small molecules (such as CO2, N2, and NO3) under mild conditions. ⁻ The electrochemical reduction of nitrates to ammonia (NO3) has attracted much attention due to its enormous potential for catalytic conversion. − The nitrogen cycle reaction (RR to NH3) not only provides a new approach to alleviate nitrogen cycle imbalance and treat nitrate pollution in water bodies, but also offers the possibility of achieving green, low-carbon "electricity-to-ammonia" and resource recycling. However, this reaction involves a multi-electron-proton transfer process, has slow kinetics, and the presence of multiple intermediate products and the competing hydrogen evolution reaction (HER) complicates the reaction route. Therefore, developing highly active and highly selective catalytic NO3-reduction reactions is crucial. − The catalyst for RR is the core bottleneck that drives this technology toward practical application.
[0003] Currently, research in this field mainly focuses on single-metal catalysts (such as Cu, Pd, Ru, etc.) and traditional binary alloy catalysts. These catalysts suffer from limited active sites, low electronic conductivity, and difficulty in simultaneously addressing the multiple requirements of reactant adsorption, intermediate conversion, and product desorption, resulting in poor reaction selectivity and Faraday efficiency that fails to meet practical application needs. Multi-principal alloy or high-entropy alloy catalysts, due to their unique "high-entropy effect," "lattice distortion effect," "retarded diffusion effect," and "cocktail effect," exhibit excellent catalytic activity, stability, and multifunctionality. However, their complex composition design and synthesis often lead to high costs and poor controllability. In recent years, medium-entropy catalysts (typically containing 3-5 main elements) have emerged as an important branch of multi-component alloy catalytic materials. They retain the synergistic effect of multiple elements while avoiding the phase separation problems that may occur in high-entropy systems, demonstrating excellent catalytic potential. Through the synergistic effect of multiple components and entropy-driven microstructural regulation, they exhibit unique electronic properties and surface structure advantages, significantly increasing the number of active sites for catalytic reactions and optimizing the adsorption / desorption behavior of reaction intermediates, providing new degrees of freedom for catalyst design.
[0004] The medium-entropy catalyst preparation method based on the entropy increase strategy significantly improves the number of active sites in terms of both "specific surface area expansion" and "enrichment of active site types," providing a new direction for solving the problem of insufficient catalytic activity. "Entropy increase," as a fundamental principle of thermodynamics, drives a system to evolve towards a more disordered and stable state. In materials science, introducing multiple principal elements to increase configurational entropy yields uniformly distributed active sites. However, how to combine this macroscopic thermodynamic strategy of "entropy increase" with the design of microscopic active sites in catalysts, especially in the field of electrochemical nitrate reduction, still lacks systematic research. Summary of the Invention
[0005] The purpose of this invention is to provide a medium-entropy catalyst based on a self-reduction strategy, its preparation method, and its application. By synergistically regulating the electronic structure through multiple elements, the adsorption / desorption behavior of reaction intermediates is optimized, thereby improving the adsorption capacity of NO3-. − Reduction (RR) performance is of great significance. Meanwhile, the medium-entropy catalyst preparation method based on the entropy increase strategy has universality and shows broad application prospects in multiple electrocatalysis fields such as CO2 reduction, nitrogen reduction, water electrolysis for hydrogen production, and organic synthesis.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] One of the technical solutions of this invention is to provide a method for preparing a medium-entropy catalyst based on a self-reduction strategy, comprising the following steps:
[0008] A plating solution is prepared by dissolving a non-Cu metal salt with weaker metal activity than iron, a Cu salt, a metal ligand, and a surfactant in water. A foamed iron substrate is immersed in the plating solution for 10-60 minutes to increase entropy and obtain a medium-entropy catalyst. The molar ratio of Cu to non-Cu metal in the plating solution is (1-2):(1-4).
[0009] Optionally, the non-Cu metal salt with weaker metal activity than iron includes Ni salt, Co salt, Sn salt, Ag salt, or Bi salt, etc.
[0010] Optionally, the non-Cu metal salt with weaker metallic activity than iron comprises chloride salts and / or nitrate salts; the Cu salt comprises chloride salts and / or nitrate salts.
[0011] Preferably, the concentration of the metal salt with weaker metal activity than iron in the plating solution is 20 mmol / L.
[0012] Preferably, the concentration of the copper salt in the plating solution is 20 mmol / L.
[0013] Preferably, the metal ligand is 5,5-dimethylhydantoin.
[0014] More preferably, the concentration of 5,5-dimethylhydantoin in the plating solution is 5 mmol / L.
[0015] Preferably, the surfactant is polyethylene glycol 4000.
[0016] More preferably, the concentration of polyethylene glycol 4000 in the plating solution is 6 g / L.
[0017] Preferably, the foamed iron substrate further includes a pretreatment step before being immersed in the plating solution.
[0018] The second technical solution of the present invention provides a medium-entropy catalyst prepared according to the above-mentioned method for preparing medium-entropy catalysts based on self-reduction strategies.
[0019] The third technical solution of the present invention provides an application of the Fe-Cu-Ni medium-entropy catalyst in the above-mentioned medium-entropy catalyst in the electrochemical synthesis of ammonia.
[0020] The beneficial technical effects of the present invention are as follows:
[0021] This invention employs a simple one-step in-situ self-reduction strategy to achieve the entropy increase process of the material, providing abundant active sites for the adsorption and reduction conversion of nitrates during the catalytic electrochemical synthesis of ammonia.
[0022] The medium-entropy catalyst provided by this invention has a simple, efficient, and low-cost preparation method that is easy to mass-produce.
[0023] This invention discloses a method and application for designing and applying a universally applicable medium-entropy catalyst based on the metal self-reduction process to achieve entropy increase. It can easily prepare various medium-entropy catalysts such as Fe-Cu-Ni, Fe-Cu-Co, Fe-Cu-Sn, Fe-Cu-Ag, and Fe-Cu-Bi. In addition to being used for nitrate electroreduction, it can also provide new ideas for the preparation of materials in the fields of electrocatalysis such as CO2 reduction, nitrogen reduction, water electrolysis for hydrogen production, and organic synthesis.
[0024] The Fe-Cu-Ni medium-entropy catalyst, one of the medium-entropy catalysts prepared in this invention, exhibits excellent catalytic performance in the electrochemical synthesis of ammonia, with a Faradaic efficiency (FE) as high as 98.74% and a yield as high as 19.56 mg·h⁻¹. -1 ·cm -2 Furthermore, in stability tests exceeding 12 hours, its performance remained above 90% of its original value, with the reduction product being high-purity NH4Cl. It also maintains high stability in coal chemical industry wastewater recycling, achieving efficient removal and resource utilization of the target pollutant (nitrate) in industrial wastewater, thus combining economic and environmental benefits. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 The XRD pattern of the Fe-Cu-Ni medium-entropy catalyst prepared in Example 1 is shown.
[0027] Figure 2 The image shows the SEM images of the Fe-Cu-Ni medium-entropy catalyst prepared in Example 1, where a and b are SEM images at different magnifications.
[0028] Figure 3 The image shows the HAADF diagram of the entropy-medium catalyst of Fe-Cu-Ni prepared in Example 1.
[0029] Figure 4 The performance of Fe-Cu-Ni medium entropy catalyst in electrocatalyzing the reduction of nitrate to ammonia under different voltages.
[0030] Figure 5 The figure shows the stability test results of the Fe-Cu-Ni medium entropy catalyst at −1.0 V vs. RHE.
[0031] Figure 6 The image shows the XRD pattern of the reduction product of Fe-Cu-Ni medium entropy catalyst after enrichment and evaporation crystallization at −1.0 V vs. RHE.
[0032] Figure 7 The performance of the medium entropy catalysts prepared in Examples 2-5 in electrocatalyzing the reduction of nitrate to ammonia at −1.0 V vs. RHE is shown.
[0033] Figure 8 This is a schematic diagram illustrating the principle of preparing entropy catalysts based on a self-reduction strategy according to the present invention. Detailed Implementation
[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.
[0035] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.
[0036] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.
[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0039] Example 1
[0040] Preparation of entropy catalysts in Fe-Cu-Ni:
[0041] S1: Pretreatment of foamed iron:
[0042] The foamed iron was cut into 1 cm × 1 cm squares (with 3 mm × 5 mm tabs), and then ultrasonically cleaned in an ice bath for 15 min in sequence with acetone, 2 mol / L hydrochloric acid, deionized water, and anhydrous ethanol to remove oxides, organic matter and other impurities from the surface of the foamed iron.
[0043] S2: Preparation of plating solution:
[0044] Each 50 mL volume of plating solution contains 1 mmol NiCl2, 1 mmol CuCl2, 2.5 mmol 5,5-dimethylhydantoin, and 0.3 g polyethylene glycol 4000. The 0.3 g polyethylene glycol 4000 needs to be fully dissolved in deionized water before use. The plating solution needs to be thoroughly stirred before use.
[0045] S3: Self-reducing entropy increase:
[0046] The pretreated foamed iron was immersed below the surface of the plating solution and self-deposited for 10 min with stirring at 200 rpm. The resulting catalyst was then immersed in deionized water for 30 s and dried with cold air to obtain the Fe-Cu-Ni medium entropy catalyst, which was then sealed and stored.
[0047] The XRD pattern of the Fe-Cu-Ni medium-entropy catalyst prepared in Example 1 is shown in [Figure 1]. Figure 1 .Depend on Figure 1It can be seen that, in addition to matching the diffraction peaks of Cu and Ni elements, it can also match the diffraction peaks of a small number of Fe-Ni alloys and Cu-Ni alloys, proving the successful substitution of Cu and Ni.
[0048] The SEM image of the Fe-Cu-Ni medium-entropy catalyst prepared in Example 1 is shown below. Figure 2 Where a and b are SEM images at different magnifications. Figure 2 It can be seen that at lower magnification, there are diffusely distributed micro-protrusions at the pore edges of the three-dimensional skeleton of foamed iron. Through high-magnification imaging analysis, these protrusions are CuNi particles densely attached to the substrate surface.
[0049] The HAADF diagram of the Fe-Cu-Ni intermediate entropy catalyst prepared in Example 1 is shown below. Figure 3 .Depend on Figure 3 As can be seen from HAADF-STEM imaging and the corresponding EDS elemental distribution map, the signal intensities of Fe, Ni, and Cu are uniformly distributed without bias at the nanoscale, and their spatial positions are highly overlapping, indicating that the three elements form a homogeneous mixed phase.
[0050] Example 2
[0051] Preparation of entropy catalysts in Fe-Cu-Co:
[0052] Unlike Example 1, in step S2, NiCl2 is replaced with an equimolar amount of CoCl2, while the other steps remain the same, thus obtaining the Fe-Cu-Co entropy catalyst.
[0053] Example 3
[0054] Preparation of entropy catalysts in Fe-Cu-Sn:
[0055] Unlike Example 1, in step S2, NiCl2 is replaced with an equimolar amount of SnCl2, and a small amount of 1 mol / L hydrochloric acid is added to prevent Sn from spreading. 2+ Hydrolysis, with the remaining steps being the same, yields the entropy catalyst in Fe-Cu-Sn.
[0056] Example 4
[0057] Preparation of entropy catalysts in Fe-Cu-Ag:
[0058] Unlike Example 1, in step S2, CuCl2 and NiCl2 are replaced with equimolar amounts of Cu(NO3)2 and AgNO3, respectively. The remaining steps are the same, and the Fe-Cu-Ag entropy catalyst can be obtained.
[0059] Example 5
[0060] Preparation of entropy catalysts in Fe-Cu-Bi:
[0061] Unlike Example 1, in step S2, CuCl2 and NiCl2 were replaced with equimolar amounts of Cu(NO3)2 and Bi(NO3)3, respectively, and a small amount of 10 wt.% HNO3 was added to ensure that Bi 3+ After stable dissolution, the remaining steps are the same, and the entropy catalyst in Fe-Cu-Bi can be obtained.
[0062] The Fe-Cu-Ni entropy catalyst prepared in Example 1 was used for the electrocatalytic reduction of nitrate to synthesize ammonia:
[0063] The performance of the Fe-Cu-Ni medium-entropy catalyst was tested in an H cell using a Chenhua electrochemical workstation (CHI660E) with an electrolyte of 1 mol / L KOH + 0.1 mol / L KNO3. The Fe-Cu-Ni medium-entropy catalyst, a 2 cm × 2 cm platinum sheet, and Ag / AgCl were used as the working electrode, counter electrode, and reference electrode, respectively. Each anode and cathode chamber contained 30 mL of electrolyte. Before testing, the electrodes were activated using linear sweep voltammetry (LSV) at a scan rate of 10 mV / s until the polarization curves stabilized. The voltage range was −1.2 V to −0.2 V vs. RHE. Stability testing was performed at the voltage (−1.0 V vs. RHE) for optimal Faraday efficiency and yield. A fresh electrolyte was used for each cycle, while other parameters remained constant. Nessler's reagent was used to determine the ammonia yield. The reaction solution after reduction at constant potential for 1 h was diluted to the calibrated concentration range, and the ammonia yield was calculated by converting the absorbance.
[0064] Figure 4 The performance of the Fe-Cu-Ni medium entropy catalyst in electrocatalyzing the reduction of nitrate to ammonia under different voltages. From Figure 4 As can be seen, when electrolyzing at a constant potential of −1.0 V vs. RHE, the Faraday efficiency (FE) is as high as 98.74%, and the yield is as high as 19.56 mg·h⁻¹. -1 ·cm -2 It exhibits superior catalytic performance.
[0065] Figure 5 The figure shows the stability test results of the Fe-Cu-Ni medium entropy catalyst at −1.0 V vs. RHE. Figure 5 The results showed that after 12 consecutive cycles of use, it still maintained a Faraday efficiency of over 92% and a concentration of over 18.27 mg / h. -1 ·cm -2 ammonia yield.
[0066] Figure 6The image shows the XRD pattern of the reduction product of Fe-Cu-Ni medium entropy catalyst after enrichment and evaporation crystallization at −1.0 V vs. RHE. Figure 6 The results show that the NH4Cl solid obtained after evaporation and crystallization matches the standard substance card perfectly, proving that the recovered NH4Cl has high purity.
[0067] Replacing Ni with Co, Sn, Ag, and Bi yielded the Fe-Cu-Co, Fe-Cu-Sn, Fe-Cu-Ag, and Fe-Cu-Bi entropy catalysts obtained in Examples 2-5. The XRD patterns of these catalysts all matched their respective metal phases (Co, Sn, Ag, and Bi), exhibiting excellent catalytic performance and stability. The catalysts obtained in Examples 2-5 were subjected to NO3- catalysis at −1.0 V vs. RHE. − RR performance verification (method same as Fe-Cu-Ni medium entropy catalyst), the obtained electrocatalytic nitrate reduction to ammonia synthesis performance is shown in [reference]. Figure 7 . Figure 7 The results showed that the Fe-Cu-Co, Fe-Cu-Sn, Fe-Cu-Ag, and Fe-Cu-Bi catalysts achieved FE yields of 91.04%, 84.73%, 77.21%, and 88.42%, respectively, with yields of 16.6, 17.94, 16.1, and 19.98 mg·h⁻¹. -1 ·cm -2 This indicates that the entropy catalyst obtained by the self-reduction strategy has universality and applicability.
[0068] Therefore, the entropy-increasing strategy proposed in this invention for the synthesis of medium-entropy catalysts exhibits excellent catalytic efficiency and demonstrates the universality of this strategy. Furthermore, evaporating and crystallizing the enriched product yields high-purity NH4Cl.
[0069] To verify the applicability of the Fe-Cu-Ni medium-entropy catalyst proposed in this invention, the Fe-Cu-Ni medium-entropy catalyst prepared in Example 1 was used as the working electrode, and the experimental method for electrocatalytic reduction of nitrate to ammonia synthesis was followed as described above. This was applied to wastewater from the coal chemical industry (NO3). − The resource recovery process of nitrate (at a concentration of approximately 1200 mg / L) was carried out at a voltage of −1.0 V vs. RHE. Without any prior treatment, 13.61 mg·h⁻¹ was obtained after 1 hour of electrocatalysis. -1 ·cm -2 The ammonia yield indicates the practical application value and commercial application potential of this medium-entropy catalyst.
[0070] A schematic diagram illustrating the principle of this invention for preparing entropy catalysts based on a self-reduction strategy is shown below. Figure 8 M is one of the chloride or nitrate salts of Ni, Co, Sn, Ag, and Bi.
[0071] In summary, this invention discloses a Fe-Cu-Ni medium-entropy catalyst for the electrochemical conversion of nitrate to ammonia. It utilizes in-situ self-reduction to achieve entropy increase, providing efficient catalytic sites for nitrate adsorption and activation. Furthermore, this invention discloses a general medium-entropy catalyst design method and application based on an entropy increase strategy. The above examples describe the basic principles, main features, and advantages of this invention. The preparation method is simple and efficient, suitable for large-scale preparation, and beneficial for the industrial application of this catalyst. Taking the electrocatalytic reduction of nitrate as an example, this invention demonstrates the broad application prospects of medium-entropy catalysts in the electrocatalytic reduction of nitrate to ammonia. Simultaneously, the entropy increase strategy verified by this invention provides important theoretical guidance and practical reference for the design and performance optimization of catalysts in other electrocatalytic fields such as CO2 reduction, water electrolysis for hydrogen production, and organic synthesis.
[0072] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing a medium-entropy catalyst based on a self-reduction strategy, characterized in that, Includes the following steps: A plating solution is prepared by dissolving a non-Cu metal salt with weaker metal activity than iron, a Cu salt, a metal ligand, and a surfactant in water. A foamed iron substrate is immersed in the plating solution for 10-60 minutes to increase entropy and obtain a medium-entropy catalyst. The molar ratio of Cu to non-Cu metal in the plating solution is (1-2):(1-4).
2. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 1, characterized in that, The non-Cu metal salts with weaker metallic activity than iron include Ni salts, Co salts, Sn salts, Ag salts, or Bi salts.
3. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 1, characterized in that, The non-Cu metal salts, which are less reactive than iron, contain chloride salts and / or nitrate salts; the Cu salts contain chloride salts and / or nitrate salts.
4. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 1, characterized in that, The concentration of the metal salt with weaker metal activity than iron in the plating solution is 20 mmol / L; and / or, the concentration of the copper salt in the plating solution is 20 mmol / L.
5. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 1, characterized in that, The metal ligand is 5,5-dimethylhydantoin.
6. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 5, characterized in that, The concentration of 5,5-dimethylhydantoin in the plating solution is 5 mmol / L.
7. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 1, characterized in that, The surfactant is polyethylene glycol 4000.
8. The method for preparing a medium-entropy catalyst based on a self-reduction strategy according to claim 7, characterized in that, The concentration of polyethylene glycol 4000 in the plating solution is 6 g / L.
9. A medium-entropy catalyst prepared by the method for preparing a medium-entropy catalyst based on a self-reduction strategy according to any one of claims 1 to 8.
10. The application of the Fe-Cu-Ni medium-entropy catalyst of claim 9 in the electrochemical synthesis of ammonia.