Nanoporous crystal-glass intergrowth high-entropy alloy and preparation method and electrode thereof

Abstract

The application discloses a kind of nano-porous crystal-glass symbiotic high-entropy alloy and its preparation method, electrode, belongs to catalytic electrode field, method steps are as follows: depositing manganese-containing first alloy layer and zirconium-containing second alloy layer on substrate, after annealing treatment, first with hydrofluoric acid, ammonium sulfate de-alloying;By magnetron sputtering and annealing, a plurality of metal atoms of first alloy layer diffuses to second alloy layer, due to negative mixing enthalpy and atomic radius difference makes zirconium-containing layer alloy conversion glass alloy, eliminates heterogeneous nucleation;After two-step de-alloying, form nano-porous crystal-glass symbiotic high-entropy alloy, abundant element types and large specific surface area formed after de-alloying provide a large number of active sites for catalytic reaction to occur, while crystal layer high-entropy alloy by regulating surface glass layer alloy electronic structure, the intrinsic catalytic activity of second alloy layer is enhanced, and the high stability of structure also improves the durability of electrode material.

Description

Technical Field

[0001] This invention relates to a nanoporous crystal-glass coexisting high-entropy alloy, its preparation method, and an electrode, belonging to the field of catalytic electrodes. Background Technology

[0002] Hydrogen energy is a crucial component of the future energy system. Electrolysis of water using renewable energy sources such as wind and solar power is a vital technological means to achieve the goal of "carbon peaking and carbon neutrality." Currently, Pt and IrO2 are the most commonly used cathode and anode catalysts for water electrolysis due to their excellent catalytic activity and durability. However, 1 GW of water electrolysis requires 300 kg of platinum and 700 kg of iridium. Continuing to use precious metal catalysts makes it difficult to strike a balance between excellent electrochemical performance and low cost, forcing the development of highly efficient non-precious metal catalysts. Transition metal-based catalysts are widely available, low in cost, contain unfilled d orbitals, and their unpaired electrons are beneficial for the adsorption and desorption of reactive groups, making them a potential alternative to precious metal catalysts. However, the activity and cycle life of current transition metal-based catalysts are not ideal. Developing highly active and stable transition metal-based catalysts is of great significance for promoting the large-scale application of water electrolysis technology.

[0003] Heterogeneous HER (hydrogen evolution reaction) catalysts possess fine nanostructures and well-exposed edges, providing ample adsorption sites for HER reaction intermediates. The charge transfer or redox properties between different components of heterogeneous catalysts can enhance the activity and efficiency of the chemical reaction, and the synergistic effect of different active sites can improve reaction kinetics. Compared to corresponding single-phase transition metal-based catalysts, the synergistic effect between the two phases in heterogeneous catalysts may exhibit higher conductivity, catalytic activity, and stability.

[0004] Most heterostructured materials are crystal-crystal structures. Unlike crystalline structures, amorphous materials possess randomly oriented chemical bonds, which can induce abundant unsaturated coordination configurations and dangling bonds. These structural defect sites can serve as potential active sites in electrocatalytic reactions. However, the relatively low electrical conductivity of amorphous materials limits electron transfer processes. By coupling amorphous components with crystalline components to form crystal-amorphous heterostructures, interfacial electron redistribution can be induced, promoting electron transfer processes on the crystal-amorphous heterostructure catalyst during electrocatalysis. Furthermore, the formation of crystal-amorphous heterostructures is always accompanied by the modulation of electronic states and the optimization of adsorption / desorption behavior.

[0005] Although crystalline-amorphous interface materials have unique interfaces that can induce synergistic effects, electronic interactions, and strain effects among multiple components to enhance catalyst activity, in actual use, the heterogeneous nucleation at the crystalline-amorphous heterostructure interface results in poor thermal stability and easy structural damage. In particular, glass alloys exhibit room temperature brittleness, which affects the lifespan of the electrodes. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a nanoporous crystal-glass co-existing high-entropy alloy and its preparation method. The obtained nanoporous crystal-glass co-existing high-entropy alloy has high catalytic activity, high thermal stability, and a certain degree of flexibility at room temperature. The present invention also provides an electrode accordingly.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] In a first aspect, this application provides a method for preparing a nanoporous crystal-glass co-existing high-entropy alloy, comprising the following steps:

[0009] A first alloy layer is deposited on a substrate; the first alloy layer is a solid solution alloy of at least three of nickel, cobalt, iron, molybdenum, copper, chromium, ruthenium, palladium, tungsten, osmium, iridium, platinum, silver, and gold with manganese;

[0010] A second alloy layer is deposited on the surface of the first alloy layer; the second alloy layer is a solid solution alloy formed by at least one of titanium, niobium, hafnium, tantalum, terbium, and yttrium with zirconium; the substrate temperature is below 90°C when depositing the first alloy layer and the second alloy layer;

[0011] Annealing is performed to obtain the symbiotic alloy precursor;

[0012] The symbiotic alloy precursor is first-step dealloyed using hydrofluoric acid solution;

[0013] The symbiotic alloy precursor was subjected to a second-step dealloying process using ammonium sulfate solution to obtain the nanoporous crystal-glass symbiotic high-entropy alloy.

[0014] The method for preparing nanoporous crystal-glass symbiotic high entropy alloy provided in this application first deposits two alloy layers, both of which are crystalline structures. Elements migrate between the layers, with the metal containing Mn (the first alloy layer) diffusing into the alloy containing Zr (the second alloy layer). Due to the large negative enthalpy of mixing and the large difference in atomic radii, the alloy containing Zr undergoes a glass transition to form a glass alloy. The stable symbiotic alloy interface eliminates heterogeneous nucleation, enhances thermodynamic and mechanical stability, and improves both strength and ductility. The resulting material exhibits excellent HER properties.

[0015] Furthermore, the thickness of the second alloy layer is 10 nm, which is conducive to the migration of interlayer elements to form a glass layer and a crystal-glass interface. If the thickness of the second alloy layer is too small or too large, it will be difficult to form a glass layer.

[0016] Furthermore, the thickness of the first alloy layer is less than 2 μm, which is beneficial for the first alloy layer to form a porous structure and to expose active sites to the greatest extent to participate in the catalytic reaction.

[0017] Furthermore, based on atomic number, the zirconium content in the second alloy layer is above 45%.

[0018] In the first step of dealloying, Zr is mainly removed. The zirconium content in the second alloy layer is above 45%, which is conducive to the formation of a three-dimensional continuous through-hole structure after the first step of dealloying and to the effective contact between the electrolyte and the alloy layer during the second step of dealloying.

[0019] Furthermore, the first step of dealloying the symbiotic alloy precursor using hydrofluoric acid solution includes immersing the nanoporous crystal-glass symbiotic high-entropy alloy in a 0.05 mol / L-0.5 mol / L hydrofluoric acid solution for 2 s-120 s. This dealloying step rapidly forms a large, interconnected porous structure on the surface of the second alloy layer, extending down to the first alloy layer. This not only increases the surface area and fully exposes the crystal-glass interface but also facilitates a more efficient reaction between the ammonium sulfate solution and the first alloy layer during the second dealloying step. By adjusting the time and temperature of the first dealloying step, the pore structure and active centers can be controlled.

[0020] Furthermore, based on the number of atoms, the manganese content in the first alloy layer is above 50%.

[0021] The first alloy layer contains four or more elements to form a high-entropy alloy. The second step of dealloying uses ammonium sulfate solution to remove the Mn element from the crystal layer (first alloy layer) using chemical / electrochemical methods to form a second nanoporous structure. When the manganese content is too low, it is difficult to carry out electrochemical dealloying, so the manganese content should be above 50%.

[0022] Furthermore, the second-step dealloying step using ammonium sulfate solution to the symbiotic alloy precursor includes: soaking the nanoporous crystal-glass symbiotic high-entropy alloy in a 1.0 mol / L-3.0 mol / L ammonium sulfate solution for 3-6 hours. By adjusting the concentration of the ammonium sulfate solution, hierarchical nanoporous alloys with different structures can be obtained.

[0023] Furthermore, in the steps of depositing the first alloy layer and depositing the second alloy layer, magnetron sputtering is used at a deposition rate of 5 nm / min.

[0024] Low-temperature magnetron sputtering is beneficial for the formation of symbiotic alloys. During magnetron sputtering, alloy atoms undergo interlayer diffusion, with elements from the first alloy layer diffusing into the second alloy layer. Due to the large radius difference between atoms and the large negative enthalpy of mixing, these elements readily combine with atoms in the second alloy layer, resulting in a glass transition. Subsequent annealing further promotes interlayer migration of elements, which is even more conducive to the formation of crystal-glass symbiotic high-entropy alloys.

[0025] Secondly, this application provides a nanoporous crystal-glass coexisting high-entropy alloy, which is prepared by the method described in the first aspect. It has high HER catalytic activity, high thermal stability, and a certain degree of flexibility at room temperature.

[0026] Thirdly, this application provides an electrode comprising the nanoporous crystal-glass co-existing high-entropy alloy described in the second aspect.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) It combines the advantages of crystalline high-entropy alloy catalysts and amorphous high-entropy alloy catalysts. By designing alloy composition and preparation methods, a crystal-glass symbiotic alloy interface is formed, which overcomes the thermal instability caused by heterogeneous nucleation of crystal-glass alloys and improves the durability of the catalyst.

[0029] (2) Crystalline high-entropy alloys can regulate the electronic structure of the surface amorphous layer, optimize the binding energy between active sites and intermediate products, and reduce the water dissociation potential energy, thereby enhancing the intrinsic catalytic activity of this type of catalyst.

[0030] (3) The use of dealloying strategy to construct nanoporous structures greatly increases the electrochemical surface area and exposes more active sites. At the same time, the pore channels help the electrolyte to enter and exit and the bubbles to be released. It can also increase the specific surface area, expose more active sites, and enhance reaction kinetics.

[0031] (4) The symbiotic alloy structure reduces the room temperature brittleness of glass alloys, which solves the bottleneck problem for the engineering application of this type of catalyst.

[0032] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0033] Figure 1 The graph shows the results of testing the overpotential of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and a commercial electrode under different current densities.

[0034] Figure 2The graph shows the results of electrode stability testing on the nanoporous crystal-glass co-existing high-entropy alloy prepared in Example 2.

[0035] Figure 3 This is a diagram showing the state of the symbiotic alloy precursor obtained in Example 2 under pressure.

[0036] Figure 4 This is an electron microscope image of the nanoporous crystal-glass coexisting high-entropy alloy prepared in Example 2. Detailed Implementation

[0037] Crystalline-amorphous interface materials possess unique interfaces that can induce synergistic effects, electronic interactions, and strain effects among multiple components to enhance catalyst activity, enabling the design of heterogeneous HER catalysts. However, heterogeneous nucleation occurs at the crystal-glass interface in general crystalline-amorphous interface materials, resulting in poor thermal stability and high brittleness.

[0038] This application provides a method for preparing a nanoporous crystal-glass co-existing high-entropy alloy, comprising the following steps:

[0039] S1: Deposit a first alloy layer on the substrate. The first alloy layer is a solid solution alloy of at least three of the following: nickel, cobalt, iron, molybdenum, copper, chromium, ruthenium, palladium, tungsten, osmium, iridium, platinum, silver, and gold, with manganese. The substrate can be titanium, stainless steel, polymer, etc.

[0040] S2: Deposit a second alloy layer on the surface of the first alloy layer. The second alloy layer is a solid solution alloy formed by at least one of titanium, niobium, hafnium, tantalum, terbium, and yttrium with zirconium.

[0041] S3: Annealing is performed to obtain the symbiotic alloy precursor.

[0042] S4: The first step of dealloying the symbiotic alloy precursor is performed using hydrofluoric acid solution.

[0043] S5: A second-step dealloying process is performed on the symbiotic alloy precursor using ammonium sulfate solution to obtain a nanoporous crystal-glass symbiotic high-entropy alloy. Solutions such as sulfuric acid and hydrochloric acid are too acidic, leading to excessively large pore sizes after dealloying, which is detrimental to electrocatalysis. Using ammonium sulfate solution for dealloying is more suitable for electrocatalysis. During the dealloying process, a negative pressure environment can be maintained to improve the dealloying effect.

[0044] During deposition, alloy atoms diffuse between layers, with elements from the first alloy layer diffusing into the second. Due to the large radius difference and negative enthalpy of mixing between atoms, the crystals in the second layer readily undergo a glass transition. Meanwhile, the alloying elements in the first alloy layer, due to their lower glass-forming ability, retain their crystalline structure, thus forming a crystal-glass co-existing alloy with high thermal stability. The first dealloying step uses HF solution for chemical dealloying, removing Zr elements from the amorphous layer to form a nanoporous structure. The second dealloying step uses ammonium sulfate solution for chemical / electrochemical dealloying, removing Mn elements from the crystalline layer to form the second nanoporous structure. Different nanoporous structures can be obtained using solutions of varying concentrations, dealloying times, and dealloying methods, including variations in pore size (from hundreds of nanometers to a few nanometers), elemental composition, dealloying depth, and catalytic active centers, thereby forming hierarchical nanoporous crystal-glass co-existing high-entropy alloys.

[0045] The method for preparing nanoporous crystal-glass co-existing high entropy alloy provided in this application first deposits two alloy layers, both of which are crystalline structures. Elements migrate between the layers, and the metal in the first alloy layer diffuses into the second alloy layer. Due to the large negative enthalpy of mixing and the large difference in atomic radii, the second alloy layer undergoes a glass transition to form a glass alloy. The stable co-existing alloy interface avoids heterogeneous nucleation of this type of material, enhances thermodynamic and mechanical stability, and also has excellent HER performance, making it suitable for use as a self-supporting electrode.

[0046] Example 1

[0047] The first alloy layer consists of nickel, cobalt, iron, molybdenum, and manganese, while the second alloy layer consists of titanium, zirconium, niobium, and hafnium. The alloy precursor composition is denoted as NiCoFeMoMn@TiZrNbHf, where the atomic ratio of NiCoFeMoMn is 14:14:14:6:52, and the atomic ratio of TiZrNbHf is 18:46:18:18. The symbiotic alloy precursor was deposited on a Ti substrate using magnetron sputtering. First, a NiCoFeMoMn layer was sputtered, followed by a TiZrNbHf layer. The thickness of the TiZrNbHf layer was 12 nm, and the deposition rate for both NiCoFeMoMn and TiZrNbHf layers was set to 5 nm / min, resulting in a total sputtered layer thickness of 2 μm. The NiCoFeMoMn@TiZrNbHf symbiotic high-entropy alloy precursor was then immersed in 0.05 M HF solution for 8 s. After washing with deionized water, place it in a 0.5M (NH4)2SO4 solution and dealloy for 4 hours under negative pressure. Then wash with deionized water and set aside for use.

[0048] Example 2

[0049] The alloy precursor composition was NiCoFeMoCrMn@TiZrNbHf, where the atomic ratio of NiCoFeMoCrMn was 14:14:14:4:4:50, and the atomic ratio of TiZrNbHf was 18:46:18:18. The symbiotic alloy precursor was deposited on a Ti substrate using magnetron sputtering. First, a NiCoFeMoCrMn layer was sputtered, followed by a TiZrNbHf layer. The thickness of the TiZrNbHf layer was 12 nm, and the deposition rate of both the NiCoFeMoCrMn and TiZrNbHf layers was set to 5 nm / min, resulting in a total sputtered layer thickness of 2 μm. The resulting symbiotic alloy precursor is shown below. Figure 3 As shown, it can undergo elastic bending under pressure and is not easily brittle, therefore it can be used as a self-supporting electrode. The NiCoFeMoCrMn@TiZrNbHf symbiotic high-entropy alloy precursor was then placed in 0.05M HF solution for 8 s. After washing with deionized water, it was placed in 0.5M (NH4)2SO4 and de-alloyed under negative pressure for 4 h, then washed with deionized water for later use. The electron micrograph of the obtained nanoporous crystal-glass symbiotic high-entropy alloy is shown below. Figure 4 As shown, first observe Figure 4 In the lower magnification field of view on the left, larger "cracks" can be seen, which are porous structures formed after the ammonium sulfate solution undergoes dealloying; further observation... Figure 4 In the field of view with higher magnification on the right, even smaller pores than "cracks" can be seen, indicating that the nanoporous crystal-glass co-existing high-entropy alloy has a hierarchical porous structure.

[0050] Comparative Example 1

[0051] The alloy precursor composition was NiFeMn@TiZrNbHf, with an atomic ratio of NiFeMn of 24:24:52 and TiZrNbHf of 18:46:18:18. The symbiotic alloy precursor was deposited on a Ti substrate using magnetron sputtering, first sputtering a NiFeMn layer, then a TiZrNbHf layer. The thickness of the TiZrNbHf layer was 12 nm, and the deposition rate of both NiFeMn and TiZrNbHf layers was set at 5 nm / min, resulting in a total sputtered layer thickness of 2 μm. The NiFeMn@TiZrNbHf symbiotic high-entropy alloy precursor was then placed in a 0.05 M HF solution for 8 s. After washing with deionized water, it was placed in a 0.5 M (NH4)2SO4 solution and de-alloyed under negative pressure for 4 h, followed by washing with deionized water for further use.

[0052] Comparative Example 2

[0053] The alloy precursor composition was NiFeMn@TiZrNb, with an atomic ratio of NiFeMn of 24:24:52 and TiZrNb of 25:50:25. The symbiotic alloy precursor was deposited on a Ti substrate using magnetron sputtering, first sputtering a NiFeMn layer, then a TiZrNb layer. The TiZrNb layer thickness was 12 nm, and the deposition rate of both NiFeMn and TiZrNb layers was set at 5 nm / min, resulting in a total sputtered layer thickness of 2 μm. The NiFeMn@TiZrNb symbiotic high-entropy alloy precursor was then immersed in 0.05 M HF solution for 8 s. After rinsing with deionized water, it was placed in 0.5 M (NH4)2SO4 solution and de-alloyed under negative pressure for 4 h. Finally, it was rinsed with deionized water and ready for use.

[0054] The overpotentials of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and the commercial Pt / C catalyst at different current densities were tested, and the results are as follows: Figure 1 As shown in Table 1, a portion of the data is extracted and presented below.

[0055] Table 1

[0056] Sample Name <![CDATA[10 mA cm -2 (mV)]]> <![CDATA[100 mA cm -2 (mV)]]> <![CDATA[500 mA cm -2 (mV)]]> <![CDATA[1000 mA cm -2 (mV)]]> Pt / C 41.1 169.0 NiFeMn@TiZrNb 59.2 134.6 215.5 NiFeMn@TiZrNbHf 54.3 117.5 182.5 230.2 NiCoFeMoMn@TiZrNbHf 27.5 66.6 123.2 172.0 NiCoFeMoCrMn@TiZrNbHf 28.5 61.0 108.7 153.7

[0057] Figure 1 Table 1 shows that in alkaline electrolytes, the HER performance of nanoporous symbiotic alloys is superior to that of commercial Pt / C catalysts. Furthermore, due to the synergistic effect between elements and the accelerated reaction kinetics of the crystal-glass interface, the catalytic activity of refractory metals such as Ti, Zr, and Nb is enhanced.

[0058] Using the nanoporous crystal-glass co-existing high-entropy alloy obtained in Example 2 as an electrode, electrode stability tests were performed, and the results are as follows: Figure 2 As shown, this confirms that the electrode maintains good stability even under large currents.

[0059] In summary, the embodiments of this application have the following effects:

[0060] (1) By using thermodynamically guided alloy design, the symbiotic combination of crystal-glass high-entropy alloys is realized, avoiding the thermal instability of materials caused by heterogeneous nucleation of crystal-amorphous materials, and improving the durability of catalysts.

[0061] (2) Multilayer symbiotic alloys are prepared by magnetron sputtering. The crystal-glass symbiotic high-entropy alloy precursor is constructed by interlayer diffusion of atoms in the alloy. The active components of the surface glass alloy layer can be controlled to adapt to different catalytic reactions by adjusting the types of elements in the amorphous-glass layer.

[0062] (3) By combining crystal-glass co-existing high-entropy alloy with dealloying technology, a hierarchical nanoporous crystal-glass high-entropy alloy electrocatalyst is prepared. The catalyst has a hierarchical nanoporous structure. By controlling the dealloying process, the pore size, active center, catalytic surface area and other indicators can be adjusted to construct a highly active and stable transition metal-based catalyst.

[0063] (4) Symbiotic bonding improves the room temperature brittleness of glass alloys and promotes the industrial application of crystal-glass heterostructures.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0065] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a nanoporous crystalline-glass intergrowth high-entropy alloy, characterized in that, The method comprises the following steps: depositing a first alloy layer on a substrate; the first alloy layer is a solid solution alloy formed by at least three of nickel, cobalt, iron, molybdenum, copper, chromium, ruthenium, palladium, tungsten, osmium, iridium, platinum, silver, gold and manganese; depositing a second alloy layer on the surface of the first alloy layer; the second alloy layer is a solid solution alloy formed by at least one of titanium, niobium, hafnium, tantalum, terbium, yttrium and zirconium; when the first alloy layer and the second alloy layer are deposited, the temperature of the substrate is below 90°C; performing annealing treatment to obtain a symbiotic alloy precursor; performing first-step dealloying on the symbiotic alloy precursor by using a hydrofluoric acid solution; performing second-step dealloying on the symbiotic alloy precursor by using an ammonium sulfate solution to obtain the nano-porous crystal-glass symbiotic high-entropy alloy.

2. The method for preparing the nanoporous crystal-glass co-existing high-entropy alloy according to claim 1, characterized in that, The thickness of the second alloy layer is 10 nm.

3. The method for preparing the nanoporous crystal-glass co-existing high-entropy alloy according to claim 1, characterized in that, The thickness of the first alloy layer is below 2 μm.

4. The method for preparing the nanoporous crystal-glass co-existing high-entropy alloy according to claim 1, characterized in that, The content of zirconium in the second alloy layer is above 45% in terms of atomic number.

5. The method for preparing the nanoporous crystal-glass co-existing high-entropy alloy according to claim 4, characterized in that, The step of performing first-step dealloying on the symbiotic alloy precursor by using a hydrofluoric acid solution comprises soaking the symbiotic alloy precursor in a 0.05 mol / L-0.5 mol / L hydrofluoric acid solution for 2 s-120 s.

6. The method for preparing the nanoporous crystal-glass co-existing high-entropy alloy according to claim 1, characterized in that, The content of manganese in the first alloy layer is above 50% in terms of atomic number.

7. The method for preparing the nanoporous crystal-glass co-existing high-entropy alloy according to claim 6, characterized in that, The step of performing second-step dealloying on the symbiotic alloy precursor by using an ammonium sulfate solution comprises soaking the symbiotic alloy precursor in a 1.0 mol / L-3.0 mol / L ammonium sulfate solution. 8.The method of claim 1, wherein the nanoporous crystalline-glass intergrowth high-entropy alloy is prepared by a method comprising: preparing a precursor alloy by mixing a plurality of metal elements; and performing a heat treatment on the prepared precursor alloy. In the steps of depositing the first alloy layer and depositing the second alloy layer, magnetron sputtering is adopted, and the deposition rate is 5 nm / min.

9. A nanoporous crystalline-glass intergrowth high-entropy alloy, characterized in that, The nano-porous crystal-glass symbiotic high-entropy alloy prepared by the method of any one of claims 1-8.

10. An electrode characterized by, The nano-porous crystal-glass symbiotic high-entropy alloy of claim 9.

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