A high-entropy alloy material with a heterogeneous structure and a preparation method thereof

Abstract

The application discloses a high-entropy alloy material with a heterogeneous structure, which is composed of Fe, Ni, Cu, Co, Zn, V and P elements; wherein the atomic percentages of the metal elements Fe, Ni, Cu, Co and Zn in the high-entropy alloy material are the same, and are all 14% to 16%; the atomic percentage of the metal element V in the high-entropy alloy material is 10% to 20%; and the balance is the non-metal element P. The application further discloses a preparation method of the high-entropy alloy material with the heterogeneous structure. The high-entropy alloy material with the heterogeneous structure can be prepared through the regulation of element components, contents and ball milling process parameters, the alloy material has an amorphous structure matrix, the structure can provide a large number of unsaturated sites, the catalytic activity is improved, meanwhile, nano-crystals are dispersedly distributed on the amorphous matrix, the nano-crystals have good conductivity, the transfer efficiency of electrons can be effectively improved, and thus the OER catalytic reaction is facilitated.

Description

Technical Field

[0001] This invention relates to a high-entropy alloy material with a heterostructure, and also to a method for preparing the above-mentioned high-entropy alloy material. Background Technology

[0002] Electrocatalytic water splitting is an important hydrogen production strategy, consisting of two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, the OER at the anode, involving the migration of four electrons, requires a higher overpotential to break the OH bond in the hydroxyl group and form an OO bond. Its reaction kinetics are much slower than the HER, becoming a bottleneck limiting the efficiency of water electrolysis. Therefore, improving the efficiency of the OER at the anode is a key focus of water electrolysis hydrogen production technology.

[0003] Numerous studies have shown that Ru and Ir-based materials in noble metals generally exhibit superior OER electrocatalytic activity compared to other noble metals and their related compounds. However, the high cost and scarcity of these elements limit the large-scale utilization of noble metal-based materials as water electrolysis catalysts. 3d transition metals, such as Fe, Ni, Cu, and Co, possess incompletely filled d orbitals, making them more prone to electron gain and loss, which is beneficial for electron transfer during hydrolysis, resulting in high catalytic activity and abundant resources. Therefore, transition metal alloys hold promise as ideal electrocatalytic materials. Summary of the Invention

[0004] Objective of this invention: The objective of this invention is to provide a high-entropy alloy material with a heterostructure, which combines the high active sites of an amorphous structure with the high conductivity of a nanocrystalline structure. This effectively increases the number of reactive sites and improves electron transfer efficiency, thereby accelerating the electrocatalytic oxygen evolution reaction and enhancing its activity. Another objective of this invention is to provide a method for preparing the aforementioned high-entropy alloy material with a heterostructure and its application as an electrocatalytic material.

[0005] Technical solution: The high-entropy alloy material with heterogeneous structure described in this invention is composed of Fe, Ni, Cu, Co, Zn, V, and P elements; wherein the atomic percentages of the metallic elements Fe, Ni, Cu, Co, and Zn in the high-entropy alloy material are the same, all being 14% to 16%, the atomic percentage of the metallic element V in the high-entropy alloy material is 10% to 20%, and the balance is the non-metallic element P.

[0006] In this high-entropy alloy material, the atomic percentages of metallic elements Fe, Ni, Cu, Co, and Zn are all 14%, while the atomic percentage of metallic element V is 20%, with the remainder being non-metallic element P.

[0007] The heterostructure of FeNiCuCoZnVP consists of nanocrystals dispersed on an amorphous matrix.

[0008] Among them, nanocrystals, whose total volume is 10-20% of the volume of the amorphous matrix, are dispersed on the amorphous matrix.

[0009] The preparation method of the above-mentioned high-entropy alloy material with heterostructure is as follows: Fe, Ni, Cu, Co, Zn, V and P components are mixed according to the formula amount, the proportion of each component is calculated by converting atomic percentage to mass percentage, and the high-entropy alloy material with heterostructure is prepared by ball milling under an inert atmosphere.

[0010] The ball milling medium is anhydrous ethanol.

[0011] The ball milling speed is 500-700 r / min, the ball-to-material ratio is 10-20:1, and the ball milling time is 60-80 h.

[0012] The ball milling process is as follows: the ball mill runs in both forward and reverse directions alternately, with a cycle consisting of 60 minutes of forward operation followed by a 10-minute pause, 60 minutes of reverse operation followed by a 10-minute pause, and a total of 30 to 40 cycles are performed.

[0013] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention can prepare high-entropy alloy materials with heterogeneous structures by controlling the elemental composition, content, and ball milling process parameters. This alloy material possesses an amorphous matrix, which provides a large number of unsaturated sites (reactive sites), thereby improving catalytic activity. Simultaneously, nanocrystals are dispersed on the amorphous matrix. These nanocrystals have excellent electrical conductivity, effectively improving electron transfer efficiency, thus facilitating the OER catalytic reaction. The high-entropy alloy material of this invention exhibits excellent catalytic performance. The high-entropy alloy (FeNiCuCoZn) measured under alkaline conditions... 70 V 20 P 10 The catalytic oxygen evolution reaction, after electrochemical activation, is carried out at a current density of 10 mA·cm⁻¹. -2 At that time, the overpotential was 240mV, and the Tafel slope was 40.2mV·dec. -1 At 10mA·cm -2 A stability test was conducted continuously for 24 hours at the specified current density, and the voltage did not increase significantly. Attached Figure Description

[0014] Figure 1 (FeNiCuCoZn) prepared in Example 1 70 V 20 P 10The (FeNiCuCoZn) prepared in Example 3 75 V 15 P 10 XRD phase analysis spectrum of the material;

[0015] Figure 2 (FeNiCuCoZn) prepared in Example 1 70 V 20 P 10 LSV curves before and after activation;

[0016] Figure 3 To activate the pre-high entropy alloy material (FeNiCuCoZn) 70 V 20 P 10 TEM photographs. Detailed Implementation

[0017] Example 1

[0018] This invention relates to a high-entropy alloy material (FeNiCuCoZn) with a heterostructure. 70 V 20 P 10 The preparation method includes the following steps:

[0019] (1) Based on the atomic percentage of 14:14:14:14:14:20:10, convert to weight percentage and weigh out Fe, Ni, Cu, Co, Zn, V and P powders respectively, and mix them evenly;

[0020] (2) High-entropy alloy powder was prepared by ball milling under a vacuum inert atmosphere (the powder was assembled in a vacuum glove box with inert gas introduced, and then ball milled on a ball mill).

[0021] The ball milling medium was anhydrous ethanol, the ball milling speed was 500 r / min, the ball-to-material ratio was 20:1, and the ball milling time was 72 h. The ball mill operated alternately in forward and reverse directions, with a cycle consisting of 60 min forward operation followed by a 10 min pause, 60 min reverse operation followed by a 10 min pause, and a total of 36 cycles were performed.

[0022] (3) Take out the powder after alloying and ball milling in step (2) to obtain a high-entropy alloy material (FeNiCuCoZn) with a heterostructure. 70 V 20 P 10 .

[0023] The obtained (FeNiCuCoZn) 70 V 20 P 10Powder was loaded onto carbon paper measuring 2 cm × 0.5 cm to obtain a supported working electrode. Electrochemical activation was performed in a 1 mol / L KOH solution at 25 °C. The electrochemical workstation was set with a cyclic voltammetry potential range of 0.3–0.6 V, a cyclic voltammetry activation time of 200 min, and a scan rate of 0.1 V / s. The desired (FeNiCuCoZn) was obtained after activation. 70 V 20 P 10 Electrode materials.

[0024] Activated (FeNiCuCoZn) 70 V 20 P 10 The overpotential of the electrode material is 10 mA·cm -2 At a current density of 240 mV, the Tafel slope is 40.2 mV·dec. -1 .

[0025] High-entropy alloy materials (FeNiCuCoZn) 70 V 20 P 10 XRD diffraction as Figure 1 As shown, through Figure 1 It can be seen that the peaks in the spectrum have the steamed bun peak diffraction characteristics corresponding to the amorphous structure, and there are also several phase peaks in the spectrum, indicating high crystallinity. The XRD spectrum shows the high entropy alloy material (FeNiCuCoZn) prepared in Example 1. 70 V 20 P 10 The material exhibits a heterogeneous structure, as seen in the high-entropy alloy (FeNiCuCoZn) prepared in Example 3. 75 V 15 P 10 It does not have a heterostructure, but only an amorphous structure.

[0026] High-entropy alloy materials (FeNiCuCoZn) 70 V 20 P 10 The polarization curves before and after activation by cyclic voltammetry are as follows: Figure 2 As shown, by Figure 2 It is evident that cyclic voltammetric electrochemical activation can effectively enhance the electrocatalytic performance of electrode materials. Electrochemical activation leads to the formation of active substances with high OER catalytic activity and stability on the surface of the high-entropy alloy. This maintains the high active sites of the heterostructure and the high conductivity brought by the nanocrystals, while also forming hydroxyl oxide active substances containing multiple metal components, thereby effectively improving the electrocatalytic oxygen evolution performance of the material.

[0027] Figure 3To activate the pre-high entropy alloy material (FeNiCuCoZn) 70 V 20 P 10 Microstructural characterization. Figure 3 a shows the dispersed distribution of fine nanocrystals in the amorphous sample. Figure 3 In area b, marked in red, there are diffusely distributed nanocrystalline structures with clear diffraction rings and a small number of diffraction spots. These heterojunctions can promote the transfer of electrons at the interface and accelerate the catalytic reaction. Figure 3 c and Figure 3 d represents HRTEM images of nanocrystalline structures and amorphous substrates, respectively. Figure 3 The lattice fringes are clearly visible at the c-marked area, and the diffraction pattern shows that the area has strong crystallinity. Figure 3 The diffraction pattern at point d is a halo-like shape, indicating the presence of an amorphous matrix.

[0028] Example 2

[0029] A high-entropy alloy material (FeNiCuCoZn) 80 V 10 P 10 The preparation method includes the following steps:

[0030] (1) Based on the atomic percentage of 16:16:16:16:16:10:10, convert to weight percentage and weigh out Fe, Ni, Cu, Co, Zn, V and P powders respectively, and mix them evenly;

[0031] (2) High-entropy alloy powder was prepared by ball milling under a vacuum inert atmosphere;

[0032] The ball milling medium was anhydrous ethanol, the ball milling speed was 500 r / min, the ball-to-material ratio was 15:1, and the ball milling time was 66 h. The ball mill operated alternately in forward and reverse directions, with one cycle consisting of 60 min of forward operation followed by a 10 min pause, 60 min of reverse operation followed by a 10 min pause, and a total of 33 cycles were performed.

[0033] (3) Take out the powder after alloying and ball milling in step (2) to obtain (FeNiCuCoZn). 80 V 10 P 10 High-entropy amorphous alloy materials.

[0034] The (FeNiCuCoZn) obtained in Example 2 is not a heterostructure. 80 V 10 P 10Powder was loaded onto carbon paper measuring 2 cm × 0.5 cm to obtain a supported working electrode. Electrochemical activation was performed in a 1 mol / L KOH solution at 25 °C. The electrochemical workstation was set with a cyclic voltammetry potential range of 0.3–0.6 V, a cyclic voltammetry activation time of 200 min, and a scan rate of 0.1 V / s. The desired (FeNiCuCoZn) was obtained after activation. 80 V 10 P 10 Electrode materials.

[0035] Activated (FeNiCuCoZn) 80 V 10 P 10 The overpotential of the electrode material is 10 mA·cm -2 At a current density of 275 mV, the Tafel slope is 51.2 mV·dec. -1 .

[0036] Example 3

[0037] A high-entropy alloy material (FeNiCuCoZn) 75 V 15 P 10 The preparation method includes the following steps:

[0038] (1) Based on the atomic percentage of 15:15:15:15:15:15:10, convert to weight percentage, weigh out Fe, Ni, Cu, Co, Zn, V and P powders respectively, and mix them evenly;

[0039] (2) High-entropy alloy powder was prepared by ball milling under a vacuum inert atmosphere;

[0040] The ball milling medium is anhydrous ethanol, the ball milling speed is 500 r / min, the ball-to-material ratio is 10:1, and the ball milling time is 60 h. The ball mill runs alternately in forward and reverse directions. One cycle consists of 60 min of forward operation followed by a 10 min pause, 60 min of reverse operation followed by a 10 min pause, and a total of 30 cycles are run.

[0041] (3) Take out the powder after alloying and ball milling in step (2) to obtain (FeNiCuCoZn). 75 V 15 P 10 High-entropy amorphous alloy materials.

[0042] The (FeNiCuCoZn) obtained in Example 3 is not a heterostructure. 75 V 15 P 10Powder was loaded onto carbon paper measuring 2 cm × 0.5 cm to obtain a supported working electrode. Electrochemical activation was performed in a 1 mol / L KOH solution at 25 °C. The electrochemical workstation was set with a cyclic voltammetry potential range of 0.3–0.6 V, a cyclic voltammetry activation time of 200 min, and a scan rate of 0.1 V / s. The desired (FeNiCuCoZn) was obtained after activation. 75 V 15 P 10 Electrode materials.

[0043] Activated (FeNiCuCoZn) 75 V 15 P 10 The overpotential of the electrode material is 10 mA·cm -2 At a current density of 316 mV, the Tafel slope is 73.4 mV·dec. -1 .

[0044] Example 4

[0045] The preparation method of Example 4 is exactly the same as that of Example 1, except that the ball milling speed in step (2) is 400 r / min and the ball milling time is 48 h.

[0046] The (FeNiCuCoZn) obtained in Example 4 is not a heterostructure. 70 V 20 P 10 Powder was loaded onto carbon paper measuring 2 cm × 0.5 cm to obtain a supported working electrode. Electrochemical activation was performed in a 1 mol / L KOH solution at 25 °C. The electrochemical workstation was set with a cyclic voltammetry potential range of 0.3–0.6 V, a cyclic voltammetry activation time of 200 min, and a scan rate of 0.1 V / s. The desired (FeNiCuCoZn) was obtained after activation. 70 V 20 P 10 Electrode materials.

[0047] Activated (FeNiCuCoZn) 70 V 20 P 10 The overpotential of the electrode material is 10 mA·cm -2 At the current density of 292 mV, the Tafel slope is 77.4 mV·dec. -1 .

[0048] Adjusting the ball milling time and speed reduces the likelihood of obtaining high-entropy alloy materials with heterogeneous structures. In the initial stages of ball milling, the powder is easily deformed and compressed into flakes after intense impact from the grinding balls. With continued milling, the flake particles gradually weld together, forming blocky particles. The protruding parts of these blocky particles are crushed and smoothed by the grinding balls, while the pits are filled with the relatively ductile stearic acid, thus gradually causing the particles to become more spherical. If the ball milling time is too short, the powder will continue to mix uniformly and weld together. However, as the ball milling speed decreases, the number of effective collisions between powder particles decreases, the phase transformation energy decreases, the crystallization rate slows down, and the solid solution between the Fe, Ni, Cu, Co, Zn, V, and P element powders is reduced.

[0049] Comparative Example 1

[0050] Based on Example 1, Zn was replaced with Ag, while all other conditions remained unchanged, resulting in (FeNiCuCoAg). 70 V 20 P 10 Activated (FeNiCuCoAg) 70 V 20 P 10 The overpotential of the electrode material is 10 mA·cm -2 At the current density of 277 mV, the Tafel slope is 50.4 mV·dec. -1 .

[0051] Comparative Example 2

[0052] Based on Example 1, without adding the non-metallic element P, and keeping all other conditions unchanged, we obtained (FeNiCuCoZn). 80 V 20 Activated (FeNiCuCoZn) 80 V 20 The overpotential of the electrode material is 10 mA·cm -2 At a current density of 300mV, the Tafel slope is 89mV·dec. -1 .

[0053] Comparative Example 3

[0054] Based on Example 1, only the composition ratio of the elements was changed, while the other conditions remained the same.

[0055] Based on the atomic percentage ratio of 16:16:16:16:16:10:10, converting it to weight percentage, weigh out Fe, Ni, Cu, Co, Zn, V, and P powders respectively, and mix them evenly to obtain (FeNiCuCoZn). 80 V 10 P 10 .

[0056] Activated (FeNiCuCoZn) 80 V 10 P 10 The overpotential of the electrode material is 10 mA·cm -2 At a current density of 285 mV, the Tafel slope is 57.5 mV·dec. -1 .

[0057] Comparative Example 4

[0058] Based on Example 1, only the composition ratio of the elements was changed, while the other conditions remained the same.

[0059] Based on the atomic percentage ratio of 15:15:15:15:15:15:10, converting it to weight percentage, weigh out Fe, Ni, Cu, Co, Zn, V, and P powders respectively, and mix them evenly to obtain (FeNiCuCoZn). 75 V 15 P 10 .

[0060] Activated (FeNiCuCoZn) 75 V 15 P 10 The overpotential of the electrode material is 10 mA·cm -2 At the current density of 292 mV, the Tafel slope is 63.4 mV·dec. -1 .

[0061] For the (FeNiCuCoZn) prepared in Example 1 70 V 20 P 10 For the electrode material, the cyclic voltammetry electrochemical activation time set in Example 1 was changed to 10 min, 50 min, and 100 min, with a potential range of 0.3–0.6 V and a scan rate of 0.1 V / s. The overpotential of the resulting activated electrode material was within 10 mA·cm⁻¹. -2 At current densities of 270mV, 264mV, and 255mV, respectively, the Tafel slopes were 70.5mV·dec. -1 50.1mV·dec -1 46.3mV·dec -1As CV activation proceeds, flocculent structures grow in situ on the particle surface. These flocculents adhere to the particle surface, further expanding the electrochemical active area of ​​the catalyst. This exposes more electrochemical active sites, thus improving the OER catalytic performance of the powder after activation compared to before activation. Furthermore, the longer the activation time, the more flocculent material grows, further increasing the catalyst's active area, enhancing catalytic activity, reducing overpotential, and resulting in a lower Tafel slope, which also signifies faster reaction kinetics and electron transfer rates.

Claims

1. A high-entropy alloy material having a heterogeneous structure, characterized by: The high-entropy alloy material is composed of Fe, Ni, Cu, Co, Zn, V and P elements; wherein, the atomic percentage of metal elements Fe, Ni, Cu and Co in the high-entropy alloy material is the same, all being 14%, the atomic percentage of metal element V in the high-entropy alloy material is 20%, and the rest is non-metal element P; the heterogeneous structure of FeNiCuCoZnVP is that nanocrystals are dispersedly distributed on the amorphous matrix; the nanocrystals dispersedly distributed on the amorphous matrix have a total volume of 10-20% of the volume of the amorphous matrix.

2. The method for preparing the high-entropy alloy material with heterogeneous structure according to claim 1, characterized in that, Specifically, the Fe, Ni, Cu, Co, Zn, V and P components are mixed according to the formula amount, and the high-entropy alloy material with a heterogeneous structure is prepared by using a ball milling method under an inert atmosphere; the ball milling speed is 500-700 r / min, and the ball milling time is 60-80 h. 3.The method of claim 2, wherein the method further comprises: annealing the high-entropy alloy material at a temperature of 800-1200 ℃ for 1-10 hours. The ball milling medium is anhydrous ethanol.

4. The method of claim 2, wherein the method further comprises: The ball-to-material ratio is 10-20:

1. ​ 5. The method of claim 2, wherein the method further comprises: The ball milling process is as follows: the ball mill is alternately operated in forward and reverse directions, the forward direction is operated for 60-65 min, then paused for 10-15 min, the reverse direction is operated for 60-65 min, then paused for 10-15 min, and the operation mode of one cycle period is as above, and the total operation cycle is 30-40. ​ 6. Application of the high-entropy alloy material with a heterogeneous structure as claimed in claim 1 as an electrocatalytic material.

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