High-entropy oxide material, preparation method and application thereof

Abstract

The application provides a high-entropy oxide material and a preparation method and application thereof, and relates to the technical field of supercapacitor materials.The high-entropy oxide material is prepared from nitrate of Cr, Fe, Co and Ni and ammonium paramolybdate as raw materials through a simple solution synthesis method, and has a spinel structure and a space group of Fd-3m.The preparation method can utilize the high-entropy effect of multiple metal elements, increase the specific surface area of the material, and make the prepared high-entropy oxide maintain the structural stability and electrochemical activity under high temperature or extreme electrochemical conditions, and is not prone to phase separation or degradation, thereby significantly improving the durability and service life of the material.The high-entropy oxide material prepared by the above method exhibits excellent pseudo-capacitance behavior in electrochemical energy storage, and provides an efficient and economical material selection for energy storage.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitor materials, and in particular to a high-entropy oxide material and a preparation method and application thereof. Background Art

[0002] In recent years, supercapacitors have shown broad application prospects in the field of energy storage due to their high power density, fast charge and discharge, and excellent cycle life. Among them, pseudocapacitive materials have gradually become a research hotspot because they can store charge through reversible redox reactions, which not only significantly improves the specific capacity of supercapacitors, but also has fast kinetic characteristics and excellent stability. At present, common pseudocapacitive materials include transition metal oxides (such as RuO2, MnO2) and conductive polymers. Among them, RuO2 is considered to be one of the most promising materials due to its excellent pseudocapacitive behavior and conductive properties. However, the high cost and resource scarcity of precious metal oxides seriously limit the feasibility of their large-scale commercial application. Therefore, the search for alternative materials, especially low-cost, high-efficiency alternative materials, has become one of the current research hotspots in the field of electrochemical energy storage. In this context, in order to address the performance limitations of traditional materials, researchers have begun to seek alternative materials with high performance and multifunctionality, which not only increase the number of active sites but also significantly improve their electrochemical stability and charge storage capacity, laying an important foundation for the further development of energy storage technology.

[0003] In view of this, it is necessary to design an improved high entropy oxide material and its preparation method and application to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a high entropy oxide material and a preparation method and application thereof.

[0005] To achieve the above-mentioned object of the invention, on the one hand, the present invention provides a high entropy oxide material, wherein the high entropy oxide contains five transition metal elements, which are Cr, Fe, Co, Ni and Mo;

[0006] The chemical formula of the high entropy oxide is (CrFeCoNiMo x )3O4, and the range of x is 0.01-0.4, which is a spinel structure with a space group of Fd-3m.

[0007] Preferably, the value of x is 0.01:1, 0.1:1, 0.2:1, 0.3:1, or 0.4:1.

[0008] On the other hand, the present invention also provides a method for preparing the high entropy oxide material, comprising the following steps:

[0009] Dissolving nitrates corresponding to Cr, Fe, Co, and Ni and ammonium paramolybdate in water to form a mixed solution, and adjusting the pH of the solution to 11 to obtain a mixed solution;

[0010] Drying the mixture at 70-80° C. for 10-14 hours, and grinding the product after drying to obtain a precursor powder;

[0011] The precursor powder is heated and oxidized at 700-800° C. for 1-2 hours, and then ground again after heating to obtain a high entropy oxide material.

[0012] Preferably, the molar ratio of the secondary nitrates corresponding to Cr, Fe, Co and Ni is 1:1:1:1.

[0013] Preferably, the ratio of the mass of the ammonium paramolybdate to the total mass of the five transition metal raw materials is (0.01-0.4):1.

[0014] Preferably, the ratio of the mass of the ammonium paramolybdate to the total mass of the five transition metal raw materials is 0.01:1, 0.1:1, 0.2:1, 0.3:1, or 0.4:1.

[0015] Preferably, the total concentration of solutes in the mixed solution is 0.5 mol / L.

[0016] Preferably, the pH of the solution is adjusted using aqueous ammonia, with the mass percentage of aqueous ammonia being 25-28%.

[0017] Preferably, the temperature of the heating oxidation process is increased from 30°C to 750°C at a heating rate of 5°C / min.

[0018] In particular, the high entropy oxide material prepared by the preparation method proposed in the present invention can be used as an electrochemical supercapacitor material and a pseudocapacitor electrode material.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention provides a method for preparing a high-entropy oxide material. This method uses nitrates corresponding to Cr, Fe, Co, and Ni and ammonium paramolybdate as raw materials, and a spinel-structured high-entropy oxide material with a space group of Fd-3m can be prepared by a simple solution synthesis method. Secondly, the present invention flexibly regulates the performance of the material by controlling the ratio of each metal element and the synthesis conditions. The prepared high-entropy oxide material exhibits excellent performance in the field of supercapacitors, exhibits significant pseudocapacitive behavior, has long charge and discharge time and high stability, and provides an efficient solution and economical material selection for energy storage.

[0021] 2. The preparation method of the high-entropy oxide material provided by the present invention can be achieved without a specific experimental atmosphere, the reaction conditions are mild, and the experiment is highly repeatable, which can be achieved in large-scale production and is suitable for industrial applications.

[0022] 3. The preparation method of the high entropy oxide material provided by the present invention has high product purity, adjustable material properties, few by-products, and low environmental pollution, while avoiding the use of expensive or toxic reducing agents.

[0023] 4. The preparation method of the high-entropy oxide material provided by the present invention increases the specific surface area of ​​the material through the high-entropy effect of multiple metal elements. The high-entropy oxide can still maintain structural stability and electrochemical activity under high temperature or extreme electrochemical conditions, and is not prone to phase separation or degradation, thereby significantly improving the durability and service life of the material.

[0024] 5. The preparation method of the high-entropy oxide material provided by the present invention can adjust the 3d electronic structure of the spinel structure by regulating the doping amount of Mo. The prepared high-entropy oxide material exhibits high specific capacitance and excellent cycle stability, and is suitable for application in high-performance supercapacitor electrode materials, providing a new solution for the energy storage field. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an optical photograph of the high entropy oxide material prepared in Example 1 of the present invention;

[0026] Figure 2 This is the XRD pattern of the high entropy oxide material prepared in Example 1 of the present invention;

[0027] Figure 3 This is a constant current charge and discharge curve of the high entropy oxide material prepared in Example 1 of the present invention;

[0028] Figure 4 This is a constant current charge and discharge curve of the high entropy oxide material prepared in Example 2 of the present invention;

[0029] Figure 5 TEM image (100 nm) of the high entropy oxide material prepared in Example 2 of the present invention;

[0030] Figure 6 TEM image (20 nm) of the high entropy oxide material prepared in Example 3 of the present invention;

[0031] Figure 7 TEM image (10 nm) of the high entropy oxide material prepared in Example 3 of the present invention;

[0032] Figure 8 This is a constant current charge and discharge curve of the high entropy oxide material prepared in Example 3 of the present invention;

[0033] Figure 9 This is a constant current charge and discharge curve of the high entropy oxide material prepared in Example 4 of the present invention;

[0034] Figure 10 This is the constant current charge and discharge curve of the high entropy oxide material prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0037] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0038] On the one hand, the present invention provides a high entropy oxide material, wherein the high entropy oxide contains five transition metal elements, wherein the five transition metal elements are Cr, Fe, Co, Ni and Mo, and the chemical formula of the high entropy oxide is (CrFeCoNiMo x )3O4, and the range of x is 0.01-0.4, which is a spinel structure with a space group of Fd-3m.

[0039] On the other hand, the present invention also provides a method for preparing the above-mentioned high entropy oxide material, comprising the following steps:

[0040] Dissolve the corresponding nitrates of Cr, Fe, Co, and Ni and ammonium paramolybdate in water to form a mixed solution, and add ammonia water to adjust the solution pH to 11;

[0041] Drying the mixed solution at 70-80° C. for 10-14 hours, grinding the product after drying to obtain a precursor powder; wherein the total concentration of the solute in the mixed solution is 0.5 mol / L;

[0042] The oxidation precursor powder is heated at 700-800°C for 1-2 hours and then ground again to obtain a high entropy oxide material.

[0043] In some embodiments, the molar ratio of the nitrates corresponding to Cr, Fe, Co, and Ni is 1:1:1:1, and the ratio of the mass of ammonium paramolybdate to the total mass of the five transition metal raw materials is (0.01-0.4):1. The specific ratio can be 0.01:1, 0.1:1, 0.2:1, 0.3:1, or 0.4:1.

[0044] In the above technical solution, by regulating the ratio of each metal element and heating the oxidation precursor powder at 750°C for 1 hour, an oxide material with a spinel structure is produced. This process can utilize the high entropy effect of multiple metal elements to increase the specific surface area of ​​the material. The resulting high entropy oxide can still maintain structural stability and electrochemical activity under high temperature or extreme electrochemical conditions, and is not prone to phase separation or degradation, thereby significantly improving the durability and service life of the material. The high entropy oxide material produced by the above method exhibits excellent pseudocapacitive behavior in electrochemical energy storage and can be used in supercapacitors and related energy storage devices.

[0045] In some embodiments, the mass percentage of aqueous ammonia is 25-28%.

[0046] In some embodiments, the temperature of the heating oxidation process is increased from 30° C. to 750° C. at a heating rate of 5° C. / min.

[0047] Furthermore, the high entropy oxide material prepared by the preparation method proposed in the present invention can be used as an electrochemical supercapacitor material, and is particularly suitable for application in the field of pseudocapacitive electrode materials.

[0048] The high entropy oxide material, preparation method and application of the present invention are further described below with reference to specific embodiments:

[0049] Example 1

[0050] This embodiment prepares a high entropy oxide material, and the preparation method includes the following steps:

[0051] Weigh 1.1901g Cr(NO3)3·9H2O, 2.0204g Fe(NO3)3·9H2O, 1.4551g Co(NO3)2·6H2O, 1.4551g Ni(NO3)2·6H2O, 0.6170mg(NH4)6Mo7O 24·4H2O, and dissolved in 10mL of deionized water with a purity of 18.2MΩ·cm, first ultrasonically dissolved, and then magnetically stirred for 10min to obtain a mixed solution with a concentration of 0.5mol / L (the total concentration of the five transition metal elements); 25-28% ammonia water was slowly added dropwise to the mixed solution for 5min, until the pH of the mixed solution reached 11 and remained stable, then the addition was stopped, and then magnetically stirred at room temperature for 0.5h;

[0052] The solution was allowed to stand to allow the solid matter in the solution to settle, and then dried at 70-80°C for 12 hours. After drying, the obtained solid was ground to obtain a precursor powder;

[0053] The precursor powder was placed in a muffle furnace, and the starting temperature of the muffle furnace program was set to 30°C, the heating rate was 5°C / min, the temperature in the furnace was raised from 30°C to 750°C, and the holding time was 1h to heat and oxidize the precursor powder; after the heating was completed, the temperature in the furnace was cooled from 750°C to 25°C at a cooling rate of 2°C / min, the product was taken out, washed with deionized water, dried at 70-80°C for 12h, and then ground again to obtain a high entropy oxide material.

[0054] The optical photograph of the high entropy oxide material prepared in this embodiment is as follows Figure 1 As shown, the XRD pattern is Figure 2 As shown in the figure, after comparison with the phase library, the results show that the diffraction peaks at 2θ of 18.9°, 30.6°, 35.9°, 37.6°, 43.6°, 54.1°, 57.5°, 63.2° and 74.7° are attributed to the (111), (220), (311), (222), (400), (422), (511), (440) and (533) crystal planes of the spinel structure, respectively, and no diffraction peaks of other secondary phases or impurity phases are detected, indicating that a single phase is formed.

[0055] In order to explore the performance of the high entropy oxide material prepared in the above steps as an electrochemical supercapacitor material, the test was carried out according to the following method: 5 mg of high entropy oxide material was placed in a 1.5 mL centrifuge tube, and 250 uL of deionized water, 250 mL of anhydrous ethanol, and 5 uL of a Nafion solution with a mass fraction of 5 wt% were added to the centrifuge tube in sequence. After ultrasonic vibration at 25 ° C for 30 minutes, the solution prepared in the above steps was taken with a pipette and evenly dropped on the surface of a nickel foam substrate with a length × width = 1 cm × 3 cm. After drying, it was used as a working electrode; the working electrode was electrochemically activated by CV, the reference electrode was a saturated calomel electrode, the counter electrode was a Pt wire, and the electrolyte was a KOH solution with a concentration of 1 mol / L. The voltage scanning range of the test process was -1.5 to 1.2 V, the scanning rate was 0.05 V / s, and the number of cycles was 200-400. The constant current charge and discharge curves of the high entropy oxide are shown in Figure 2. Figure 3 As shown in the figure, the constant current charge and discharge (GCD) curve can be seen, and the calculated surface capacitance is 84.3F / cm when tested under the condition of current density of 1A / g. 2 , which shows that this material has good energy storage performance.

[0056] Example 2

[0057] The difference between Example 2 and Example 1 is that: (NH4)6Mo7O 24 The mass of 4H2O is different from that in Example 1, specifically 6.170 mg. The other experimental parameters are the same as those in Example 1 and will not be repeated here. The constant current charge and discharge curve of the high entropy oxide prepared in this example is shown in FIG. Figure 4 As shown in the figure, it can be seen that the charge and discharge time is increased compared with Example 1, and the calculated surface capacitance is 171.5F / cm 2 .

[0058] Example 3

[0059] The only difference between Example 3 and Example 1 is that: (NH4)6Mo7O 24 The mass of 4H2O is different from that in Example 1, specifically 12.34 mg. The other experimental parameters are the same as those in Example 1 and will not be repeated here. The TEM images of the high entropy oxide prepared in this example at different magnifications are as follows: Figure 5-7 As shown in the figure, regular lattice fringes can be seen, indicating that the material has a good crystal structure; the constant current charge and discharge curve is shown in Figure 8 As shown in the figure, it can be seen that the charge and discharge time increases with the increase of Mo content, and the surface capacitance is 521.3F / cm 2 .

[0060] Example 4

[0061] The only difference between Example 4 and Example 1 is that: (NH4)6Mo7O 24 The mass of 4H2O is different from that in Example 1, specifically 18.51 mg. The other experimental parameters are the same as those in Example 1 and will not be repeated here. The constant current charge and discharge curve of the high entropy oxide prepared in this example is shown in FIG. Figure 9 As shown in the figure, the capacitance can be calculated to be 236.7F / cm 2 .

[0062] Example 5

[0063] The only difference between Example 5 and Example 1 is that: (NH4)6Mo7O 24 The mass of 4H2O is different from that in Example 1, specifically 24.68 mg. In Examples 1 to 5, (NH4)6Mo7O 24 The ratios of the mass of 4H2O to the total mass of the five transition metal raw materials were 0.01, 0.1, 0.2, 0.3, and 0.4, respectively. Other experimental parameters were the same as those in Example 1 and will not be repeated here.

[0064] The high entropy oxide prepared in this example was used as a pseudocapacitive electrode material for electrochemical testing. The electrolyte was 1 mol / L KOH solution, nickel foam covered with high entropy oxide was used as the working electrode, saturated calomel electrode was used as the reference electrode, and Pt wire was used as the counter electrode. The voltage sweep range during the test was -1.5 to 1.2 V, the sweep rate was 0.05 V / s, and the number of cycles was 200-400. The test results are shown in FIG. Figure 10 As shown in the figure, it can be seen that at a current density of 1A / g, the surface capacitance of the sample is 205.1F / cm 2 , showing excellent pseudocapacitive performance. From the test results of Examples 1 to 5, it can be seen that the amount of Mo added has a significant effect on the pseudocapacitive performance of the high-entropy oxide. This is because changes in the Mo content affect the number of active sites and charge storage capacity of the high-entropy oxide, thereby affecting the pseudocapacitive performance.

[0065] In summary, the high-entropy oxide material prepared by the present invention has a unique multi-metal composition and nanostructure. Its preparation method is simple, low-cost and highly controllable. During the preparation process, a uniform distribution of multiple metal elements is achieved through a homogeneous solution medium, and the formation of a spinel structure is optimized by heat treatment, ensuring the structural stability and high crystallinity of the material. Secondly, the high-entropy oxide prepared by the preparation method proposed by the present invention effectively regulates the electronic structure by introducing the Mo element, enhances the electronic transport performance of the material, thereby increasing the specific surface area and the number of pseudocapacitive active sites, providing an important guarantee for achieving excellent pseudocapacitive performance and charge storage capacity.

[0066] The above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalent replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a high entropy oxide material, characterized in that: Combine 1.1901g Cr(NO3)3·9H2O, 2.0204g Fe(NO3)3·9H2O, 1.4551g Co(NO3)2· 6H2O, 1.4551g Ni(NO3)2·6H2O, 12.34mg(NH4)6Mo7O 24 4H2O was dissolved in 10 mL of deionized water with a purity of 18.2 MΩ·cm to obtain a mixed solution with a concentration of 0.5 mol / L, and the pH of the solution was adjusted to 11 to obtain a mixed solution; Drying the mixture at 70-80° C. for 10-14 hours, and grinding the product after drying to obtain a precursor powder; The precursor powder is heated and oxidized at 700-800° C. for 1-2 hours, and then ground again after heating to obtain a high entropy oxide material.

2. The preparation method according to claim 1, characterized in that The pH of the solution is adjusted by using ammonia water, and the mass percentage of the ammonia water is 25-28%.

3. The preparation method according to claim 1, characterized in that The temperature of the heating oxidation process was increased from 30°C to 750°C at a heating rate of 5°C / min.

4. A high entropy oxide material, characterized in that The method is prepared according to any one of claims 1 to 3.

5. Use of a high entropy oxide material prepared by the preparation method according to any one of claims 1 to 3 or the high entropy oxide material according to claim 4 in an electrochemical supercapacitor material or a pseudocapacitor electrode material.

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