WO2023115929A1 - High-entropy metal oxide coating, preparation method therefor and use thereof - Google Patents

Abstract

The present invention relates to the technical field of coatings and provides a high-entropy metal oxide coating, a preparation method therefor and a use thereof. The method comprises: first preparing a metal salt solution, preheating a substrate to 300-500℃, oxidizing the metal salt solution by means of a spray gun by using a plasma spraying technology, and depositing the metal salt solution on a surface of the substrate to obtain a high-entropy metal oxide coating; the concentration of each metal salt in the metal salt solution is 0.1-0.4 mol/L, the feeding flow rate of the metal salt solution is 5-50 mL/min; the spray gun is provided to have a power of 28-40 kW, a current of 790-850 A, a voltage of 38-44 V, a spraying distance of 50-200 mm, a flame core temperature of 10000-15000 K, and a moving speed of 100-1000 mm/s; and the spraying cycle is 2-50 times. According to the high-entropy metal oxide coating in the present invention, the preparation process can be simplified, the stability of the electrode coating can be improved, and preparation of the high-entropy metal oxide electrode coating oriented to practical engineering application can be better achieved.

Description

A kind of high entropy metal oxide coating and its preparation method and application technical field

The invention relates to the technical field of coatings, in particular to a high-entropy metal oxide coating and its preparation method and application.

Background technique

High-entropy materials are a new class of materials composed of various principal components in an equimolar ratio or nearly equimolar ratio. They have properties that traditional alloys do not possess while possessing mechanical properties of traditional alloys. High-entropy metal oxides are new ceramic materials developed based on the concept of high-entropy alloys, which have good mechanical properties, and the selection of appropriate metal elements as the main component can make high-entropy metal oxides have excellent electrocatalytic properties, so they are extremely Potential lithium battery negative electrode and electrolytic water anode candidate materials.

The current common method for preparing high-entropy metal oxides with electrocatalytic activity is solid-state sintering. In the method, a ball mill is first used to mix metal oxide powders containing metal principal components, and then high-entropy metal oxide blocks can be obtained through high-temperature heat treatment and sintering steps. In order to obtain the final active electrode coating, it is also necessary to crush the above-mentioned block to obtain the powder material for film formation, and then obtain the final electrocatalytic coating on the current collector based on the coating process containing a binder . Therefore, the preparation of electrocatalytic thin layers by solid-state sintering method has the following problems: First, the use of prefabricated powder obtained by ball mills as raw materials limits the mixing uniformity of metal principal components to the particle size range, which affects the high-entropy metal oxide phase. Composition quality; second, in order to obtain high-entropy metal oxide phase, the existing preparation technology needs to adopt "furnace type" post-heating treatment, and its limited heating and cooling rate may cause element segregation, making an exception for the purity of phase composition; third , based on the conventional process, it is necessary to grind the high-entropy metal oxide block obtained by high-temperature sintering into a powder material. The transfer and diffusion of ions and electrons between the liquid-coating-current collector, thereby reducing the electrocatalytic activity of the electrode coating. It can be seen that traditional preparation techniques are not conducive to obtaining high-performance high-entropy metal oxide electrode coatings.

Plasma spraying technology uses a plasma arc driven by direct current as a heat source to heat materials such as ceramics, alloys, and metals to a molten or semi-molten state, and sprays them on the surface of a pretreated workpiece at high speed to form a firmly attached surface layer. . It is very meaningful to develop a new process for preparing high-performance high-entropy metal oxide electrode coatings by using liquid material plasma spraying technology.

Contents of the invention

Therefore, the technical problem to be solved by the present invention is to overcome problems such as limited mixing uniformity of metal elements, potential segregation of metal elements, uncontrollable microstructure, and the introduction of binders in high-entropy metal oxides in the prior art.

In order to solve the above technical problems, the present invention provides a high-entropy metal oxide coating and its preparation method and application. The invention utilizes the liquid material plasma spraying technology and feeds the multi-component metal salt solution mixed at the atomic level to realize the synthesis and deposition of the high-entropy metal oxide mixed at the atomic level and obtain a controllable microstructure.

The first object of the present invention is to provide a kind of preparation method of high entropy metal oxide coating,

S1. Configuring a metal salt solution, the metal salt solution includes at least four principal metals;

S2. Preheat the substrate to 300-500°C, and use plasma spraying technology to oxidize the metal salt solution described in step S1 through a spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; in the metal salt solution The concentration of each metal salt is 0.1-0.4mol/L; the feed flow rate of the metal salt solution is 5-50mL/min; the power of the spray gun is 28-40kW, the current is 790-850A, and the voltage is 38-44V. The spraying distance is 50-200mm, the flame core temperature is 10000-15000K, the moving speed is 100-1000mm/s; the number of spraying cycles is 2-50 times.

In one embodiment of the present invention, in step S1, the principal metal is four or more of nickel, cobalt, copper, zinc and magnesium.

In one embodiment of the present invention, in step S2, the material of the substrate is alumina, stainless steel or nickel-based alloy; the surface of the substrate is sandblasted, and the thickness of the substrate is 2-50 mm.

In one embodiment of the present invention, in the step S2, the heating rate of the flame core is 5×10 ⁷ -6×10 ⁷ K/s.

In one embodiment of the present invention, in step S2, the temperature of the substrate is kept at 100-300°C during the spraying process.

In one embodiment of the present invention, in step S2, the main gas pressure in the plasma spraying technology is 0.5-0.7MPa, the main gas flow rate is 38-70L/min, the auxiliary gas pressure is 0-0.5MPa, the auxiliary gas The flow rate is 0-45L/min.

In one embodiment of the present invention, the gas used in the spraying technique is one or more of helium, argon, nitrogen and hydrogen.

A second object of the present invention is to provide a high entropy metal oxide coating.

In one embodiment of the present invention, the thickness of the high-entropy metal oxide coating is 5-50 μm.

The third object of the present invention is to provide an application of a high-entropy metal oxide coating in the field of electrocatalysis.

Compared with the prior art, the technical solution of the present invention has the following advantages:

(1) The high-entropy metal oxide coating of the present invention utilizes the liquid material plasma spraying technology, by means of the multi-component metal salt solution feeding material mixed at the atomic level, the high temperature of the thermal plasma (the flame core temperature is as high as 10000-15000K) and the extreme The characteristics of cold and extreme heat (the heating and cooling rate can reach 5×10 ⁷ -6×10 ⁷ K/s when the liquid feed enters and leaves the plasma flame to deposit on the substrate, which promotes the anchoring of metal elements), and the high entropy The synthesis and deposition of the metal oxide coating are integrated in one step, and the mixing uniformity of the metal principal components is improved to the atomic level, and the obtained electrolytic coating does not require a binder.

(2) The high-entropy metal oxide coating of the present invention uses a variety of metal salt solutions as liquid materials through the liquid material plasma spraying technology to realize the atomic-level mixing of multi-metal principal components in the high-entropy metal oxide coating . The liquid material plasma spraying technology can directly deposit the high-entropy metal oxide coating on the metal current collector without subsequent treatments such as heat treatment, powder crushing, and binder addition. Therefore, compared with various methods such as traditional solid-state sintering, the present invention can achieve atomic-level mixed high-entropy metal oxide coating deposition, and obtain a controllable micro-nano hierarchical structure, effectively improving the activity of the electrode coating.

(3) The high-entropy metal oxide coating of the present invention contains four or more principal metals, and a variety of metal salts containing a certain number of moles of metal atoms are dissolved in deionized water by liquid material plasma spraying technology to make the metal elements Reaching Atomic Scale Mixing. The coating is deposited directly on the substrate by means of liquid material plasma spraying technology, and finally a high-entropy metal oxide electrode coating without post-treatment and binder is obtained.

(4) The high-entropy metal oxide coating of the present invention can not only simplify the preparation process, but also improve the stability of the electrode coating, and can better realize the preparation of high-entropy metal oxide electrode coatings for practical engineering applications .

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of the plasma spraying process of the present invention.

Fig. 2 is a flow chart of the present invention for preparing a high-entropy metal oxide coating.

Fig. 3 is the SEM image of the surface microstructure of the high-entropy metal oxide coating prepared in Example 1 of the present invention; wherein, (a) is a 500-fold magnified image of a surface with a scale of 15.7 mm, and (b) is a 5000-fold magnified image of a surface with a scale of 18.1 mm image.

FIG. 4 is a Raman spectrum of the high-entropy metal oxide coating prepared in Example 1 of the present invention.

Fig. 5 is the lithium battery electrode cycle life test chart prepared by the high-entropy metal oxide coating prepared in Example 1 of the present invention; wherein, (a) is the relationship between the number of charging cycles and the charge-discharge specific capacity, (b) is the relationship between the specific capacity and Voltage charge and discharge curves.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

Example 1

As shown in Figure 1-2, a high-entropy metal oxide coating and its preparation method, the prefabricated equimolar metal solution is used as the liquid phase feed material, and the liquid phase feed material enters the plasma flame and rapidly heats up through the flight process, and Deposited on the substrate, cooling down rapidly after leaving the plasma flame, and undergoing a synthetic process of converting droplets into unit cells, forming a high-entropy metal oxide coating with a surface microstructure and a mechanically occluded boundary with the substrate, the specific steps are as follows :

(1) Prefabricated metal salt solution: five metal elements of nickel, cobalt, copper, zinc, and magnesium are used as the main components, and the corresponding nitrates of the five main metals are dissolved in deionized water in equimolar numbers, and each metal The concentration of elements is controlled at 0.2mol/L.

(2) Substrate: The substrate is a stainless steel substrate with surface sandblasting treatment, the thickness is set to 2 mm, and the substrate is preheated to 400° C. with a spray gun.

(3) Spraying technology: set the spraying process parameters, use plasma spraying technology to oxidize the metal salt solution through the spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; control the movement of the plasma spray gun by combining the mechanical arm, The moving speed of the mechanical arm is set to 400mm/s, the spraying distance is set to 100mm, the heating rate of the flame core is 5×10 ⁷ K/s, the temperature of the flame core is 12000K, and the number of spraying cycles is 32. The flow rate of the liquid material is set to 30mL/min; the power of the spray gun is set to 32kW, the current is set to 800A, the voltage is set to 40V, the main air pressure is 0.7MPa, the main air flow is set to 38L/min, and the auxiliary air pressure is 0.4 MPa, the flow rate of the auxiliary gas is set to 38L/min; the gas used in the spraying technology is helium and argon; the temperature of the substrate is maintained at 200 °C by cooling during the spraying process; the thickness of the high-entropy metal oxide coating is set to 42 μm, The microscopic appearance of the surface presents a cauliflower-like structure of particle agglomeration, with a size of 30 μm. The surface of the coating is matte when observed directly.

Example 2

A high-entropy metal oxide coating and a preparation method thereof, the specific steps are as follows:

(1) Prefabricated metal salt solution: five metal elements of nickel, cobalt, copper, zinc, and magnesium are used as the main components, and the corresponding nitrates of the five main metals are dissolved in deionized water in equimolar numbers, and each metal The concentration of elements is controlled at 0.2mol/L.

(2) Substrate: The substrate is a stainless steel substrate with surface sandblasting treatment, the thickness is set to 2 mm, and the substrate is preheated to 400° C. with a spray gun.

(3) Spraying technology: set the spraying process parameters, use plasma spraying technology to oxidize the metal salt solution through the spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; control the movement of the plasma spray gun by combining the mechanical arm, The moving speed of the mechanical arm is set to 400mm/s, the spraying distance is set to 100mm, the heating rate of the flame core is 5.7×10 ⁷ K/s, the temperature of the flame core is 12800K, and the number of spraying cycles is 32. The flow rate of the liquid material is set to 30mL/min; the power of the spray gun is set to 34kW, the current is set to 810A, the voltage is set to 42V, the main air pressure is 0.7MPa, the main air flow is set to 38L/min, and the auxiliary air pressure is 0.4 MPa, the flow rate of the auxiliary gas is set to 38L/min; the gas used in the spraying technology is helium and argon; the temperature of the substrate is maintained at 200 °C by cooling during the spraying process; the thickness of the high-entropy metal oxide coating is set to 42 μm, The surface microscopic morphology presents a cauliflower-like structure of particle agglomeration with a size of 25 μm.

Example 3

A high-entropy metal oxide coating and a preparation method thereof, the specific steps are as follows:

(1) Prefabricated metal salt solution: five metal elements of nickel, cobalt, copper, zinc, and magnesium are used as the main components, and the corresponding nitrates of the five main metals are dissolved in deionized water in equimolar numbers, and each metal The concentration of elements is controlled at 0.2mol/L.

(2) Substrate: The substrate is a stainless steel substrate with surface sandblasting treatment, the thickness is set to 2 mm, and the substrate is preheated to 400° C. with a spray gun.

(3) Spraying technology: set the spraying process parameters, use plasma spraying technology to oxidize the metal salt solution through the spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; control the movement of the plasma spray gun by combining the mechanical arm, The moving speed of the mechanical arm is set to 400mm/s, the spraying distance is set to 100mm, the heating rate of the flame core is 5×10 ⁷ K/s, the temperature of the flame core is 13500K, and the number of spraying cycles is 32. The flow rate of the liquid material is set to 30mL/min; the power of the spray gun is set to 36kW, the current is set to 840A, the voltage is set to 43V, the main air pressure is 0.7MPa, the main air flow is set to 39L/min, and the auxiliary air pressure is 0.4 MPa, the flow rate of the auxiliary gas is set to 39L/min; the gas used in the spraying technology is helium and argon; the temperature of the substrate is maintained at 200°C by cooling during the spraying process; the thickness of the high-entropy metal oxide coating is set to 42 μm, The surface microscopic morphology presents a cauliflower-like structure of particle agglomeration with a size of 18 μm.

Example 4

A high-entropy metal oxide coating and a preparation method thereof, the specific steps are as follows:

(1) Prefabricated metal salt solution: five metal elements of nickel, cobalt, copper, zinc, and magnesium are used as the main components, and the corresponding nitrates of the five main metals are dissolved in deionized water in equimolar numbers, and each metal The concentration of elements is controlled at 0.2mol/L.

(2) Substrate: The substrate is a stainless steel substrate with surface sandblasting treatment, the thickness is set to 2 mm, and the substrate is preheated to 400° C. with a spray gun.

(3) Spraying technology: set the spraying process parameters, use plasma spraying technology to oxidize the metal salt solution through the spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; control the movement of the plasma spray gun by combining the mechanical arm, The moving speed of the mechanical arm is set to 400mm/s, the spraying distance is set to 120mm, the heating rate of the flame core is 5×10 ⁷ K/s, the temperature of the flame core is 12000K, and the number of spraying cycles is 32. The flow rate of the liquid material is set to 30mL/min; the power of the spray gun is set to 32kW, the current is set to 800A, the voltage is set to 40V, the main air pressure is 0.7MPa, the main air flow is set to 38L/min, and the auxiliary air pressure is 0.4 MPa, the auxiliary gas flow rate is set to 38L/min; the gas used in the spraying technology is helium and argon; the substrate temperature is maintained at 200°C by cooling during the spraying process; the thickness of the high-entropy metal oxide coating is set to 41 μm, The microscopic appearance of the surface presents a cauliflower-like structure of agglomerated particles with a size of 33 μm, and the surface of the coating is matte when observed directly.

Example 5

A high-entropy metal oxide coating and a preparation method thereof, the specific steps are as follows:

(1) Prefabricated metal salt solution: five metal elements of nickel, cobalt, copper, zinc, and magnesium are used as the main components, and the corresponding nitrates of the five main metals are dissolved in deionized water in equimolar numbers, and each metal The concentration of elements is controlled at 0.2mol/L.

(2) Substrate: The substrate is a stainless steel substrate with surface sandblasting treatment, the thickness is set to 2 mm, and the substrate is preheated to 400° C. with a spray gun.

(3) Spraying technology: set the spraying process parameters, use plasma spraying technology to oxidize the metal salt solution through the spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; control the movement of the plasma spray gun by combining the mechanical arm, The moving speed of the mechanical arm is set to 400mm/s, the spraying distance is set to 140mm, the heating rate of the flame core is 5×10 ⁷ K/s, the temperature of the flame core is 12000K, and the number of spraying cycles is 32 times. The flow rate of the liquid material is set to 30mL/min; the power of the spray gun is set to 32kW, the current is set to 800A, the voltage is set to 40V, the main air pressure is 0.7MPa, the main air flow is set to 38L/min, and the auxiliary air pressure is 0.4 MPa, the auxiliary gas flow rate is set to 38L/min; the gas used in the spraying technology is helium and argon; the substrate temperature is maintained at 200°C by cooling during the spraying process; the thickness of the high-entropy metal oxide coating is set to 41 μm, The microscopic appearance of the surface presents a cauliflower-like structure of particle agglomeration with a size of 35 μm, and the coating surface is matte in direct observation.

Comparative example 1

(1) Prefabricated metal salt solution: five metal elements of nickel, cobalt, copper, zinc, and magnesium are used as the main components, and the corresponding nitrates of the five main metals are dissolved in deionized water in equimolar numbers, and each metal The concentration of elements is controlled at 0.2mol/L.

(2) Substrate: The substrate is made of aluminum oxide substrate with surface blasting treatment, the thickness is set to 2 mm, and the substrate is preheated to 400° C. with a spray gun.

(3) Spraying technology: set the spraying process parameters, use plasma spraying technology to oxidize the metal salt solution through the spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; control the movement of the plasma spray gun by combining the mechanical arm, The moving speed of the mechanical arm is set to 400mm/s, the spraying distance is set to 50mm, the heating rate of the flame core is 5×10 ⁷ K/S, the temperature of the flame core is 17000K, and the number of spraying cycles is 32 times. The flow rate of the liquid material is set to 30mL/min; the power of the spray gun is set to 32kW, the current is set to 800A, the voltage is set to 40V, the main air pressure is 0.7MPa, the main air flow is set to 55L/min, and the auxiliary air pressure is 0.4 MPa, the auxiliary gas flow rate is set to 25L/min; compare the effect of deposition temperature on surface morphology. The thickness of the high-entropy metal oxide coating is set to 54 μm, and the cauliflower-like microstructure on the surface is not obvious. Direct observation of the coating surface shows cracks on the edge surface, and the central surface is smooth. The matte color surface in Example 1 does not appear, so The surface morphology was severely damaged.

test case 1

Characterize the high-entropy metal oxide coating prepared in Example 1, and obtain the SEM image of the surface micro-topography, as shown in Figure 3, Figure a is a 500-fold enlarged image of a surface with a scale of 15.7 mm, and Figure b is a surface with a scale of 18.1 mm of 5000 Zoom in on the image. Under the magnifying microscope, the microstructure of the coating surface is a cauliflower-like microstructure formed by a large number of 30 μm particle agglomeration structures. The coating surface has sufficient specific area, so as to obtain more surfaces participating in the reaction, which is beneficial to the reaction medium during the electrocatalytic reaction. Sufficient contact can effectively improve the activity of the electrode coating.

Comparing the data in Examples 1-3, it can be seen that if the spraying power of the spray gun is increased in an appropriate range, the cauliflower-like microstructure on the surface of the coating obtained will be smaller and the surface will be more compact. Comparing the data in Examples 1, 4, and 5, it can be seen that as the spraying distance increases, the microstructure of the coating surface has a larger size and is more loose. From the data in Comparative Example 1, it can be seen that when the temperature of the flame core used in the spraying process is too high and the coating is thick, the microstructure of the coating surface will be severely damaged.

test case 2

The high-entropy metal oxide coating prepared in Example 1 was tested by atomic spectroscopy, and the percentage of metal atoms in the local area of the coating was determined to determine the mixing uniformity of the metal elements. Table 1 shows the mass percentage and atomic percentage of each element in the test area of the high-entropy metal oxide coating in Example 1.

Table 1

element	mass percentage	atomic percentage
C	2.91	9.07
o	15.26	35.76
Mg	5.88	9.07
co	16.85	10.72
Ni	17.29	11.04
Cu	21.88	12.81
Zn	19.93	11.43

As shown in Table 1, the atomic percentages of nickel, cobalt, copper, zinc, and magnesium are respectively 9.07%, 10.72%, 11.04%, 12.91%, and 11.43%, which basically meet the requirements of equimolar ratio. And evenly distributed. The highly uniform mixing of various metal atoms in the coating is conducive to improving the quality of the high-entropy metal oxide phase composition.

Test case 3

The Mann spectrum test was carried out on the high-entropy metal oxide coating prepared in Example 1, and the results are shown in Figure 4. The D peak in the spectrum represents a lattice defect, and the peak value of the D peak of the coating obtained by liquid plasma ion spraying technology can reach 9000 , and the coating contains a large number of defect structures. The defect characteristics in the coating structure meet the requirements for preparing electrode coatings with basic characteristics as electrocatalytic and electrode materials.

Test case 4

The lithium battery electrode cycle life test was carried out on the high-entropy metal oxide coating in Example 1, and the results are shown in Figure 5, wherein Figure a is the image of the specific capacity changing with the number of charge and discharge cycles, and Figure b is the specific capacity charge and discharge voltage Curve. It can be seen that the specific capacity of the lithium battery electrode prepared using the high-entropy metal oxide coating in Example 1 is stable at 450mAh/g during the cycle life cycle, which is much higher than the 170mAh/g of the conventional lithium battery, and the voltage change is stable during the discharge process . It shows that the high-entropy metal oxide coating has the performance required for electrocatalytic electrodes and is excellent enough.

Apparently, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in various forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. A method for preparing a high-entropy metal oxide coating, characterized in that it comprises the following steps,

   S1. Configuring a metal salt solution, the metal salt solution includes at least four principal metals;

   S2. Preheat the substrate to 300-500°C, and use plasma spraying technology to oxidize the metal salt solution described in step S1 through a spray gun and deposit it on the surface of the substrate to obtain the high-entropy metal oxide coating; in the metal salt solution The concentration of each metal salt is 0.1-0.4mol/L; the feed flow rate of the metal salt solution is 5-50mL/min; the power of the spray gun is 28-40kW, the current is 790-850A, and the voltage is 38-44V. The spraying distance is 50-200mm, the flame core temperature is 10000-15000K, the moving speed is 100-1000mm/s; the number of spraying cycles is 2-50 times.
2. The preparation method of high-entropy metal oxide coating according to claim 1, characterized in that, in the S1 step, the principal metal is four or more of nickel, cobalt, copper, zinc and magnesium .
3. The preparation method of high-entropy metal oxide coating according to claim 1, is characterized in that, in S2 step, the material of described substrate is aluminum oxide, stainless steel or nickel-based alloy; The surface of described substrate is sandblasted For processing, the thickness of the substrate is 2-50mm.
4. The method for preparing a high-entropy metal oxide coating according to claim 1, characterized in that, in step S2, the heating rate of the flame core is 5×10 ⁷ -6×10 ⁷ K/s.
5. The preparation method of the high-entropy metal oxide coating according to claim 1, characterized in that, in step S2, the temperature of the substrate is kept at 100-300° C. during the spraying process.
6. The preparation method of high-entropy metal oxide coating according to claim 1, is characterized in that, in S2 step, in described plasma spraying technology, main gas pressure is 0.5-0.7MPa, and main gas flow rate is 38-70L/ min, the auxiliary gas pressure is 0-0.5MPa, and the auxiliary gas flow rate is 0-45L/min.
7. The method for preparing a high-entropy metal oxide coating according to claim 6, wherein the gas used in the spraying technique is one or more of helium, argon, nitrogen and hydrogen.
8. The high-entropy metal oxide coating obtained by the preparation method described in any one of claims 1-7.
9. The high-entropy metal oxide coating according to claim 8, wherein the thickness of the high-entropy metal oxide coating is 5-50 μm.
10. Application of the high-entropy metal oxide coating described in any one of claims 8-9 in the field of electrocatalysis.

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