High-entropy oxide catalyst with high specific surface area and preparation method and application thereof

Abstract

The invention discloses a high-entropy oxide catalyst with a high specific surface area as well as a preparation method and application thereof, and belongs to the technical field of electro-catalytic materials and preparation thereof. The chemical formula of the high-specific-surface-area high-entropy oxide catalyst is (FeCoNiMnCr) O, the specific surface area is 50-250 m < 2 > g <-1 >, the pore diameter is 7-15 nm, the pore volume is 0.35-1.0 cm < 3 > g <-1 >, and the high-specific-surface-area high-entropy oxide catalyst contains five metal elements of Fe, Co, Ni, Mn and Cr which are uniformly distributed. The (FeCoNiMnCr) O high-entropy oxide oxygen evolution catalyst is large in specific surface area, more active sites can be provided in the water electrolysis oxygen evolution reaction process, oxygen is separated out more easily, the oxygen evolution catalytic activity of the catalyst is improved, and the problems that in the prior art, the specific surface area of a high-entropy oxide is low, and the oxygen evolution efficiency is low are solved. And the number of active sites provided during the electric oxygen evolution reaction is not enough.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysis technology, in particular to a high-entropy oxide OER electrocatalyst, more particularly to a high specific surface area high-entropy oxide catalyst and a preparation method and application thereof. BACKGROUND

[0002] Under the background of carbon reduction goals, the production of new green hydrogen energy by electrochemical decomposition of water will promote this development strategy. Electrolysis of water to produce hydrogen mainly consists of two half-reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Among them, the oxygen evolution reaction (OER) is the key factor restricting the efficiency of the entire water electrolysis device due to its multi-electron transfer process and slow kinetics reaction. Therefore, researchers have been committed to developing various electrocatalysts to promote the development of water electrolysis hydrogen production technology. The most effective OER electrocatalyst is still the oxide of noble metals iridium and ruthenium (IrO2 and RuO2, etc.), but this kind of material is scarce in reserves and high in cost, which cannot meet the demand of large-scale industrial application. Non-noble metal-based catalysts (such as transition metal nitrides, sulfides) have low cost, but they have problems such as insufficient activity and poor long-term stability, making it difficult to replace noble metal catalysts. Therefore, it is necessary to develop OER catalysts with low cost, high activity and long-term stability.

[0003] High-entropy oxides (HEOs) have higher configurational entropy compared to traditional doped transition metal oxides, which are easy to form simple rock salt, fluorite, spinel or perovskite solid solution structures. At the same time, due to the tendency of each main element to arrange in disorder, i.e., atoms are randomly distributed and chemical composition is in a disordered state, HEOs exhibit "collective characteristics" due to multiple main elements, and show various excellent properties. As catalysts applied to OER reactions, HEOs have a very broad application prospect. In recent years, the development of high-entropy oxides has made some progress, but there are still many aspects that can be improved, such as the preparation process involving relatively complex reaction equipment, the need for a specific experimental atmosphere and harsh high-pressure environment, resulting in a complicated preparation process, low yield, and difficulty in achieving mass production, which restricts its large-scale application and commercialization in the OER catalysis field. In addition, the existing high-entropy oxide OER electrocatalyst has low specific surface area, and the number of active sites provided during the electrochemical oxygen evolution reaction is not enough, resulting in poor oxygen evolution catalytic activity of the catalyst.

[0004] Existing OER catalysts cannot balance low cost, high activity and long-term stability, while high-entropy oxides have potential but are limited by the preparation bottleneck. Therefore, it is an urgent need to develop new OER catalysts with low cost, high activity and long service life, especially to break through the preparation technology of high-entropy oxide catalysts with poor oxygen evolution catalytic activity, which is an urgent need to promote the industrialization of water electrolysis hydrogen production.

[0005] In order to solve the above problems, the present application is proposed. SUMMARY

[0006] In order to solve the above problems, the present application is proposed.

[0007] The present application provides a high specific surface area high-entropy oxide catalyst, which has a chemical formula of (FeCoNiMnCr)O and a specific surface area of 50-250 m 2 g -1 / m 3 g -1 .

[0008] Preferably, the high specific surface area high-entropy oxide catalyst has a pore size of 7-15 nm and a pore volume of 0.35-1.0 cm 3 g -1 .

[0009] Preferably, the high specific surface area high-entropy oxide catalyst has a spinel crystal structure, and the high specific surface area high-entropy oxide catalyst presents a secondary irregular configuration in which primary round small particles are aggregated.

[0010] Preferably, the primary round small particles have a particle size of 16-40 nm, and more preferably, the primary round small particles have a particle size of 20 nm.

[0011] In order to achieve the above-mentioned purposes, the present application provides a preparation method of the high specific surface area high-entropy oxide catalyst according to the first aspect of the present application, which comprises the following process steps:

[0012] (1) Dissolve each metal salt of Fe, Co, Ni, Mn, Cr in deionized water in a molar ratio of Fe, Co, Ni, Mn, Cr, and stir uniformly at room temperature to obtain a mixed solution containing metal salts;

[0013] (2) Weigh solid SiO2 in an aqueous solution, stir uniformly at room temperature, and obtain a uniformly dispersed SiO2 suspension;

[0014] (3) Add the SiO2 suspension obtained in step (2) to the mixed solution containing metal salts obtained in step (1), heat and stir until a gel state is obtained;

[0015] (4) Place the gel-like substance obtained in step (3) in a high-temperature reactor, heat treat, and grind thoroughly to obtain a precursor powder coated with high-entropy metal oxides on the surface of SiO2;

[0016] (5) Etch the precursor powder obtained in step (4) with a base, and after water washing, alcohol washing, and oven drying, obtain a loose and porous high specific surface area high-entropy oxide.

[0017] Preferably, in step (1), the metal salt is one of nitrate, chloride, acetylacetone salt, and acetate.

[0018] Preferably, in step (1), the total molar concentration of Fe, Co, Ni, Mn, and Cr in the metal salt mixed solution is 0.2-4 mol / L.

[0019] Preferably, in step (2), the particle size of the SiO2 powder is 5-100 nm, and the specific surface area of the SiO2 powder is 150-400 m 2 / g.

[0020] Preferably, in step (2), the mass fraction of the SiO2 suspension is 80%, and the molar ratio of the SiO2 powder to the total metal cations in the metal nitrate in step (1) is 1:2-2:1.

[0021] Preferably, in step (3), the temperature for heating and stirring is 70-90°C, and the stirring time is 1-6 h.

[0022] Preferably, in step (4), the heating treatment conditions are to increase the temperature to 350-700°C at a heating rate of 5°C / min, and the holding time is 3-6 h.

[0023] Preferably, in step (5), the base is a 0.5-2 mol / L NaOH solution.

[0024] Preferably, in step (5), the base is stirred and etched at 50-80°C for 12-48 h.

[0025] Preferably, in step (5), the drying temperature is 80-140°C, and the drying time is 12-48h.

[0026] The third aspect of the present application provides a high specific surface area high-entropy oxide catalyst (FeCoNiMnCr)O in the application of electrocatalytic oxygen evolution reaction OER.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1、The present application utilizes the viscous flow characteristics of the template, increases the viscosity of the metal salt solution through sufficient heating and stirring, makes the metal salt precursor fixedly coated with SiO2 growth, and converts the metal salt into metal oxide while maintaining sufficient mixing state under low-temperature calcination, avoids segregation and phase separation of metal elements during long-term cooling process, and improves the sintering problem of high-entropy oxide under high-temperature conditions. High-entropy oxide is prone to sintering under high-temperature conditions, causing particle agglomeration, leading to a decrease in specific surface area and activity. The preparation method of "template assisted + low-temperature preparation" can solve the above problems and obtain high-entropy oxide (FeCoNiMnCr)O with high specific surface area.

[0029] 2、The present application utilizes SiO2 template assisted preparation of spinel high-entropy oxide, successfully prepares high-entropy oxide with high specific surface area, and greatly improves the electrocatalytic oxygen evolution reaction performance. The (FeCoNiMnCr)O-350 high-entropy oxide prepared by the method of the present application has a specific surface area much higher than that of the (FeCoNiMnCr)O high-entropy oxide with the same formula synthesized by one-pot hydrothermal chemical method.

[0030] 3、In the process of preparing the catalyst, the present application finds that different calcination temperatures have a great influence on the specific surface area of the obtained catalyst. At 350°C low-temperature calcination, the specific surface area is as high as 250 m 2 g -1 , while at 1000°C calcination, the specific surface area decays to 29 m 2 g -1 , and at 300°C calcination, the specific surface area decays to 35 m 2 g -1It can be seen that temperature is a decisive factor for determining the specific surface area of the catalyst. The lower the calcination temperature, the larger the specific surface area of the corresponding catalyst, and the more active sites exposed. However, when the temperature is lower than 350 DEG C, the specific surface area of the corresponding catalyst will also decrease. Therefore, as the temperature decreases, the OER catalytic performance of the catalyst also increases, and the catalytic activity of (FeCoNiMnCr)O-350 is much higher than that of (FeCoNiMnCr)O-1000. However, when the temperature is lower than 350 DEG C, the OER catalytic performance of the catalyst will also decrease, and the catalytic activity of (FeCoNiMnCr)O-300 is lower than that of (FeCoNiMnCr)O-350.

[0031] 4、Compared with the commonly used noble metal electrocatalyst, the high-entropy oxide OER electrocatalyst with high catalytic activity is prepared at a lower cost, and the preparation process is simple, mild, green and environmentally friendly, and the raw materials are cheap and easy to obtain, which is convenient for industrial large-scale production, and is more suitable as an OER electrocatalyst for industrial electrolytic cell.

[0032] 5、The liquid phase batching is adopted to ensure that the raw materials are uniformly mixed at the molecular level, and the product realizes the stoichiometric ratio meeting the high-entropy requirement. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The XRD pattern of the (FeCoNiMnCr)O high-entropy oxide oxygen evolution catalyst of Example 1;

[0035] Figure 2 The electron microscope pattern of the (FeCoNiMnCr)O high-entropy oxide oxygen evolution catalyst of Example 1;

[0036] Figure 3 The BET pattern of the (FeCoNiMnCr)O high-entropy oxide oxygen evolution catalyst of Example 1 and the noble metal oxygen evolution reaction catalyst ruthenium oxide (RuO2) of Comparative Example 2;

[0037] Figure 4Tafel slope plot of (FeCoNiMnCr)O high-entropy oxide oxygen evolution catalyst of Example 1, Comparative Example 1, Comparative Example 2 (FeCoNiMnCr)O high-entropy oxide synthesized by one-pot hot-wet chemical method in 1 M KOH electrolyte;

[0038] Figure 5 Tafel slope plot of (FeCoNiMnCr)O high-entropy oxide oxygen evolution catalyst of Example 1, Comparative Example 1, Comparative Example 2 (FeCoNiMnCr)O high-entropy oxide synthesized by one-pot hot-wet chemical method in 1 M KOH electrolyte;

[0039] Figure 6 Stability test plot of (FeCoNiMnCr)O high-entropy oxide oxygen evolution catalyst of Example 1 in 1 M KOH electrolyte;

[0040] Figure 7 XRD plot of (LaFeCoNiCuZn)O high-entropy oxide of Example 6;

[0041] Figure 8 XRD plot of (CeZrMnCuPrNi)O high-entropy oxide of Example 7. DETAILED DESCRIPTION

[0042] The present application is further described in the following examples without limitation. The experimental methods in the examples, unless otherwise indicated, were typically carried out according to conventional conditions and as described in the manuals, or by using general equipment, materials, reagents, etc. as suggested by the manufacturers, and were commercially available, unless otherwise specified.

[0043] Comparative Sample 1: The currently widely used noble metal oxygen evolution reaction catalyst ruthenium oxide (RuO2) was prepared into an electrocatalytic electrode according to the method described in Experiment 1.

[0044] Comparative Sample 2: The same formula (FeCoNiMnCr)O high-entropy oxide was synthesized using a one-pot hot-wet chemical method. The same mass and proportion of metal nitrate as in Example 1 was weighed, glycine was added, and stirring was performed to heat to dissolution. Heating to 350°C caused it to burn into a powder, and the (FeCoNiMnCr)O high-entropy oxide finished product had a specific surface area of 6 m 2 g -1 , a pore size of 19.0 nm, and a pore volume of 0.055 cm 3 ·g -1The molar percentages of Fe, Co, Ni, Mn, and Cr in all metal elements are 19.4 mol%, 20.4 mol%, 21.0 mol%, 19.5 mol%, and 19.7 mol%, respectively.

[0045] Examples 1-5 are the preparation of (FeCoNiMnCr)O high-entropy oxide catalysts at different calcination temperatures.

[0046] Example 1

[0047] 2.02 g of Fe(NO3)3·9H2O, 1.455 g of Co(NO3)2·6H2O, 1.454 g of Ni(NO3)2·6H2O, 1.165 mL of Mn(NO3)2·4H2O solution, and 2.001 g of Cr(NO3)3·9H2O were weighed and dissolved in 10 mL of distilled water to obtain a mixed solution containing metal nitrate; then 1.5000 g of SiO2 powder with a particle size of 7-40 nm and a specific surface area of 300 m 2 g -1 was stirred uniformly in 6 mL of aqueous solution at room temperature to obtain a uniformly dispersed SiO2 suspension; then the suspension was added to the metal salt solution, heated and stirred at 70°C for 3 h, and then evaporated to obtain a viscous gel; finally, the gel was placed in a muffle furnace, heated to 350°C at a rate of 5°C / min -1 , and held for 6 h, then taken out and ground to obtain a powder. The powder was etched with 2 mol / L NaOH at 70°C for 24 h, washed with water and ethanol, and dried at 80°C for 12 h to obtain a powder. The high specific surface area (FeCoNiMnCr)O-350 high-entropy oxide catalyst for OER reaction has a spinel crystal structure, a specific surface area of 250 m 2 g -1 , a pore size of 7.2 nm, and a pore volume of 0.77 cm 3 ·g -1 . The molar percentages of Fe, Co, Ni, Mn, and Cr in all metal elements are 22.4 mol%, 23.7 mol%, 23.8 mol%, 22.2 mol%, and 7.9 mol%, respectively.

[0048] The microstructure of the high-entropy oxide OER electrocatalyst prepared in Example 1 was tested and characterized by electron microscopy, and the results are shown in Figures 1-3 . As can be seen from Figure 1 , it presents a spinel crystal structure, indicating that the (FeCoNiMnCr)O-350 spinel high-entropy oxide is successfully synthesized. From Figure 2It can be seen from the figure that the large metal particles of (FeCoNiMnCr)O-350 are stacked by small particles with a size of about 20 nm, and have obvious spinel porous structure. In addition, the image also shows a large number of randomly distributed lattice fringes and amorphous regions, which are all conducive to the transmission process of electrons in the oxygen evolution reaction. Figure 3 It can be seen from the figure that the specific surface area of the high-entropy oxide material prepared by the SiO2 template assisted method in Example 1 is much higher than that of the high-entropy oxide (FeCoNiMnCr)O synthesized by the one-pot hydrothermal chemical method in Comparative Example 2.

[0049] Example 2

[0050] Example 2 weighed 2.02 g of Fe(NO3)3·9H2O, 1.455 g of Co(NO3)2·6H2O, 1.454 g of Ni(NO3)2·6H2O, 1.165 mL of Mn(NO3)2·4H2O solution, and 2.001 g of Cr(NO3)3·9H2O, and dissolved them in 10 mL of distilled water to obtain a mixed solution containing metal nitrate; then 1.5000 g of SiO2 powder with a particle size of 7-40 nm and a specific surface area of 300 m 2 g -1 was weighed in 6 mL of aqueous solution, and stirred uniformly at room temperature to obtain a uniformly dispersed SiO2 suspension; then the suspension was added to the metal salt solution, and heated and stirred at 70°C for 3 h, and then evaporated to obtain a viscous gel; finally, the gel was placed in a muffle furnace, and heated to 400°C at a rate of 5 °C / min -1 , and kept for 3 h, and then taken out and ground to obtain a powder. The powder was etched with 2 mol / L NaOH at 70°C for 24 h, and then washed with water and ethanol, and dried at 80°C for 12 h to obtain a powder. The high specific surface area (FeCoNiMnCr)O-400 high-entropy oxide catalyst for OER reaction has a spinel crystal structure, a specific surface area of 162 m 2 g -1 , a pore size of 10.0 nm, and a pore volume of 0.80 cm 3 ·g -1 . The molar percentages of Fe, Co, Ni, Mn, and Cr in all metal elements are 15.7 mol%, 30.8 mol%, 22.2 mol%, 20.4 mol%, and 10.9 mol%, respectively.

[0051] Example 3

[0052] Weigh 2.02g Fe(NO3)3·9H2O, 1.455g Co(NO3)2·6H2O, 1.454g Ni(NO3)2·6H2O, 1.165ml Mn(NO3)2·4H2O solution, and 2.001g Cr(NO3)3·9H2O, dissolve them in 10 mL distilled water, and stir well at room temperature to obtain a mixed solution containing metal nitrates; weigh out particles with a diameter of 7-40nm and a specific surface area of ​​300 m². 2 g -1 1.5000 g of SiO2 powder was dissolved in 6 mL of aqueous solution and stirred at room temperature to obtain a uniformly dispersed SiO2 suspension. The suspension was then added to a metal salt solution and heated and stirred at 70°C for 3 hours. After evaporating the water, a viscous gel was obtained. Finally, the gel was placed in a muffle furnace and heated at 5°C for 1 minute. -1 After heating to 700℃ and holding for 5 h, the product was removed and ground to obtain powder. It was then etched with 2 mol / L NaOH at 70℃ with stirring for 24 h. After washing with water and ethanol, it was dried at 80℃ for 12 h to obtain powder. This (FeCoNiMnCr)O-700 high-entropy oxide catalyst, with a high specific surface area, is applied to the OER reaction. Its crystal structure is spinel-type, and its specific surface area is 50 m² / h. 2 g -1 The pore size is 15.0 nm, and the pore volume is 0.35 cm³. 3 ·g -1 The molar percentages of Fe, Co, Ni, Mn, and Cr among all metallic elements are 19.9 mol%, 21.1 mol%, 21.3 mol%, 18.7 mol%, and 19.0 mol%, respectively.

[0053] Example 4

[0054] Weigh 2.02g Fe(NO3)3·9H2O, 1.455g Co(NO3)2·6H2O, 1.454g Ni(NO3)2·6H2O, 1.165ml Mn(NO3)2·4H2O solution, and 2.001g Cr(NO3)3·9H2O, dissolve them in 10 mL distilled water, and stir well at room temperature to obtain a mixed solution containing metal nitrates; then weigh out particles with a diameter of 7-40nm and a specific surface area of ​​300 m². 2 g -1 1.5000 g of SiO2 powder was dissolved in 6 mL of aqueous solution and stirred evenly at room temperature to obtain a uniformly dispersed SiO2 suspension. The suspension was then added to a metal salt solution and heated and stirred at 70°C for 3 hours. After evaporating the water, a viscous gel was obtained. Finally, the gel was placed in a muffle furnace and heated at 5°C for 1 minute. -1After being raised to 1000°C for 5 h, the powder was obtained by grinding. The powder was obtained by stirring and etching with 2 mol / L NaOH at 70°C for 24 h, water washing, ethanol washing, and drying at 80°C for 12 h. The high specific surface area (FeCoNiMnCr)O-1000 high-entropy oxide catalyst applied to the OER reaction has a spinel crystal structure, a specific surface area of 29 m 2 g -1 , a pore size of 4.68 nm, and a pore volume of 0.27 cm 3 ·g -1 . The molar percentages of Fe, Co, Ni, Mn, and Cr in all metal elements are 19.5 mol%, 21.4 mol%, 21.1 mol%, 18.7 mol%, and 19.3 mol%, respectively.

[0055] Example 5

[0056] 2.02 g of Fe(NO3)3·9H2O, 1.455 g of Co(NO3)2·6H2O, 1.454 g of Ni(NO3)2·6H2O, 1.165 mL of Mn(NO3)2·4H2O solution, and 2.001 g of Cr(NO3)3·9H2O were weighed and dissolved in 10 mL of distilled water to obtain a mixed solution containing metal nitrate; 1.5000 g of SiO2 powder with a particle size of 7-40 nm and a specific surface area of 300 m 2 g -1 was stirred in 6 mL of aqueous solution at room temperature to obtain a uniformly dispersed SiO2 suspension; then the suspension was added to the metal salt solution, heated and stirred at 70°C for 3 h, and a viscous gel was obtained after evaporation of water; finally, the gel was placed in a muffle furnace, and the temperature was raised to 300°C at a rate of 5 °C / min -1 After being raised to 1000°C for 5 h, the powder was obtained by grinding. The powder was obtained by stirring and etching with 2 mol / L NaOH at 70°C for 24 h, water washing, ethanol washing, and drying at 80°C for 12 h. The high specific surface area (FeCoNiMnCr)O-1000 high-entropy oxide catalyst applied to the OER reaction has a spinel crystal structure, a specific surface area of 29 m 2 g -1 , a pore size of 5.12 nm, and a pore volume of 0.30 cm 3 ·g -1 . The molar percentages of Fe, Co, Ni, Mn, and Cr in all metal elements are 19.5 mol%, 21.4 mol%, 21.1 mol%, 18.7 mol%, and 19.3 mol%, respectively.

[0057] Example 6-7 are the preparation of high-entropy oxide (LaFeCoNiCuZn)O and high-entropy oxide (CeZrMnCuPrNi)O, respectively.

[0058] Example 6

[0059] Weigh 2.02 g of Fe(NO3)3·9H2O, 1.455 g of Co(NO3)2·6H2O, 1.20 g of Cu(NO3)2·3H2O, 1.454 g of Ni(NO3)2·6H2O, 1.40 g of Zn(NO3)2·6H2O, 2.20 g of La(NO3)·6H2O, dissolve in 10 mL of distilled water, stir uniformly at room temperature, to obtain a mixed solution containing metal nitrate; then weigh 1.5000 g of SiO2 powder with a particle size of 7-40 nm and a specific surface area of 300 m 2 g -1 2 in 6 mL of aqueous solution, stir uniformly at room temperature, to obtain a uniformly dispersed SiO2 suspension; then add the suspension to the metal salt solution, heat and stir at 70°C for 3 h, evaporate the water to obtain a viscous gel; finally, place the above gel in a muffle furnace, heat to 350°C at a rate of 5 °C / min -1 , keep for 6 h, take out and grind to obtain a powder. Stir and etch with 2 mol / L NaOH at 70°C for 24 h, wash with water and ethanol, dry at 80°C for 12 h to obtain (LaFeCoNiCuZn)O powder, which has a perovskite crystal structure, a specific surface area of 156 m 2 g -1 , a pore size of 8.6 nm, and a pore volume of 0.53 cm 3 ·g -1 . The molar percentages of La, Fe, Co, Ni, Cu, and Zn in all metal elements are 18.9 mol%, 15.4 mol%, 16.9 mol%, 13.4 mol%, 19.1 mol%, and 16.3 mol%, respectively.

[0060] Figure 7 The XRD pattern of the (LaFeCoNiCuZn)O high-entropy oxide provided in Example 6 is shown in Figure 6, from Figure 7 which it can be seen that Example 6 exhibits a perovskite crystal structure, without the presence of impurity peaks, indicating that the (LaFeCoNiCuZn)O high-entropy perovskite oxide is successfully synthesized.

[0061] Example 7

[0062] Ce(NO3)3·6H2O, 2.26 g of Zr(NO3)4·5H2O, 1.79 g of Mn(NO3)2·4H2O, 1.21 g of Cu(NO3)2·3H2O, 2.17 g of Pr(NO3)2·6H2O, and 1.45 g of Ni(NO3)2·6H2O were weighed out, dissolved in 10 mL of distilled water, and stirred uniformly at room temperature to obtain a mixed solution containing metal nitrate; then, 1.5000 g of SiO2 powder with a particle size of 7-40 nm and a specific surface area of 300 m 2 g -1 was stirred uniformly in 6 mL of an aqueous solution at room temperature to obtain a uniformly dispersed SiO2 suspension; then, the suspension was added to the metal salt solution, heated and stirred at 70°C for 3 h, and a viscous gel was obtained after evaporation of water; finally, the gel was placed in a muffle furnace, heated to 350°C at a rate of 5°C / min -1 , and held at 350°C for 5 h, and then removed and ground to obtain a powder. The powder was etched with 2 mol / L NaOH at 70°C for 24 h, washed with water and ethanol, and dried at 80°C for 12 h to obtain a high-entropy oxide (CeZrMnCuPrNi)O powder, which had a fluorite structure, a specific surface area of 75 m 2 g -1 , a pore size of 12.17 nm, and a pore volume of 2.0 cm 3 ·g -1 . The molar percentages of Ce, Zr, Mn, Cu, Pr, and Ni in all the metal elements were 17.2 mol%, 19.0 mol%, 14.6 mol%, 16.7 mol%, 15.2 mol%, and 17.3 mol%, respectively.

[0063] Figure 8 The XRD pattern of the (CeZrMnCuPrNi)O high-entropy oxide provided in Example 7 is shown in FIG. 6. Figure 8 It can be seen that the fluorite crystal form is present, indicating that the (CeZrMnCuPrNi)O high-entropy fluorite oxide was successfully synthesized.

[0064] Performance Investigation:

[0065] The application method of the catalyst samples in Comparative Examples 1-2 and Examples 1-7 in the OER reaction is as follows: the catalyst samples in Comparative Examples 1-2 and Examples 1-7 were made into anode catalytic electrodes and loaded on an area of 1 cm 2The carbon paper electrode with a loading of 200 mg was used as the working electrode, and the graphite electrode and Hg / HgO electrode were used as the counter electrode and reference electrode, respectively, to form a three-electrode system. The OER catalytic activity of the one-pot hydrothermal chemical method (FeCoNiMnCr)O of Examples 1-7, Comparative Example 2, Comparative Example 1 of RuO2 was tested at room temperature using an electrochemical workstation with 1 mol / L KOH solution as the electrolyte solution.

[0066] The overpotential of the noble metal OER catalyst RuO2 in Comparative Example 1 was 318 mV at a current density of 10 mA / cm 2

[0067] The overpotential of the high-entropy catalyst synthesized by the one-pot hydrothermal chemical method in Comparative Example 2 was 303 mV, and the Tafel slope was 50.0 mV / dec.

[0068] The (FeCoNiMnCr)O-350 material prepared in Example 1 was applied to the electrolytic water oxygen evolution reaction, and linear sweep voltammetry curve test was performed in 1 mol / L KOH. The overpotential of the material was 267 mV at 10 mA·cm -2

[0069] The (FeCoNiMnCr)O-400 material prepared in Example 2 was applied to the electrolytic water oxygen evolution reaction, and linear sweep voltammetry curve test was performed in 1 mol / L KOH. The overpotential of the material was 281 mV at 10 mA·cm -2

[0070] The (FeCoNiMnCr)O-700 material prepared in Example 3 was applied to the electrolytic water oxygen evolution reaction, and linear sweep voltammetry curve test was performed in 1 mol / L KOH. The overpotential of the material was 318 mV at 10 mA·cm -2

[0071] The (FeCoNiMnCr)O-1000 material prepared in Example 4 was applied to the electrolytic water oxygen evolution reaction, and linear sweep voltammetry curve test was performed in 1 mol / L KOH. The overpotential of the material was 335 mV at 10 mA·cm -2

[0072] ​​​​​The (FeCoNiMnCr)O-300 material prepared in Example 5 is applied to the oxygen evolution reaction of electrolytic water, linear sweep voltammetry test is carried out in 1 mol / L KOH, and it is found that the material has a current density of 10 mA·cm -2 -2 at 10 mA·cm -2 -2, the overpotential is 342 mV, and the Tafel slope is 62.7 mV / dec.

[0073] The (LaFeCoNiCuZn)O material prepared in Example 6 is applied to the oxygen evolution reaction of electrolytic water, linear sweep voltammetry test is carried out in 1 mol / L KOH, and it is found that the material has a current density of 10 mA·cm -2 -2 at 10 mA·cm -2 -2, the overpotential is 293 mV, and the Tafel slope is 49.2 mV / dec.

[0074] The (CeZrMnCuPrNi)O material prepared in Example 7 is applied to the oxygen evolution reaction of electrolytic water, linear sweep voltammetry test is carried out in 1 mol / L KOH, and it is found that the material has a current density of 10 mA·cm -2 -2 at 10 mA·cm -2 -2, the overpotential is 304 mV, and the Tafel slope is 52.6 mV / dec.

[0075] In combination Figures 4-6 , by comparing Comparative Example 1, Comparative Example 2 and Example 1, it is found that the overpotential and Tafel slope of the (FeCoNiMnCr)O-350 are lower than those of the catalyst synthesized by the one-pot wet chemical method and RuO2, which proves that the high-entropy oxide OER electrocatalyst (FeCoNiMnCr)O-350 prepared in Example 1 has high OER catalytic activity and can completely replace the expensive noble metal electrocatalyst. In 1 mol / L KOH, the current density of the (FeCoNiMnCr)O-350 is 100 mA·cm -2 -2 at 10 mA·cm -2 , and the performance only attenuates by 1.97% after stable maintenance for 100 h.

[0076] By comparing Examples 1-5, it is found that different calcination temperatures have a great influence on the specific surface area of the obtained catalyst. The specific surface area is as high as 250 m 2 g -1 after calcination at 350°C, and the specific surface area is attenuated to 29 m 2 g -1 after calcination at 1000°C; the specific surface area is attenuated to 35 m 2 g -1It can be seen that temperature is a decisive factor for specific surface area of the catalyst. The lower the calcination temperature, the larger the specific surface area of the corresponding catalyst, and the more active sites exposed; but when the temperature is lower than 350 DEG C, the specific surface area of the corresponding catalyst will also decrease. Therefore, with the decrease of temperature, the OER catalytic performance of the catalyst also increases, and the catalytic activity of (FeCoNiMnCr) O-350 is far more than that of (FeCoNiMnCr) O-1000; however, when the temperature is lower than 350 DEG C, the OER catalytic performance of the catalyst will also decrease, and the catalytic activity of (FeCoNiMnCr) O-300 is lower than that of (FeCoNiMnCr) O-350.

[0077] It can be seen from comparative example 1, example 6 and example 7 that different elements form different crystal forms of high-entropy oxides, which also have an impact on the reaction activity. The spinel crystal form high-entropy oxide formed by Fe, Co, Ni, Mn and Cr five elements exhibits the best catalytic activity, and has the best OER catalytic activity compared with fluorite type and perovskite type.

[0078] Finally, it should be noted that the above-mentioned is only a few specific embodiments of the present application, which is used to help illustrate the present application. Obviously, the present application is not limited to the above examples, and there can be many variations. All variations that can be directly derived or inferred from the content disclosed by the person skilled in the art should be considered as the protection scope of the present application.

Claims

1. A high specific surface area, high entropy oxide catalyst, characterized in that, The high specific surface area, high entropy oxide catalyst has the chemical formula (FeCoNiMnCr)O and a specific surface area of ​​50–250 m². 2 g -1 The high specific surface area high entropy oxide catalyst contains five metal elements, Fe, Co, Ni, Mn and Cr, which are uniformly distributed. The molar percentages of Fe, Co, Ni, Mn and Cr in the total metal elements are 15-25 mol%, 15-30 mol%, 15-25 mol%, 15-25 mol%, and 5-25 mol%, respectively.

2. The high specific surface area, high entropy oxide catalyst according to claim 1, characterized in that, The high specific surface area, high entropy oxide catalyst has a pore size of 7–15 nm and a pore volume of 0.35–1.0 cm³. 3 g -1 .

3. The high specific surface area, high entropy oxide catalyst according to claim 2, characterized in that, The high specific surface area high entropy oxide catalyst has a spinel crystal structure, and the high specific surface area high entropy oxide catalyst exhibits primary spherical small particles agglomerated into a secondary irregular configuration; The primary spherical particles have a particle size of 16-40 nm.

4. A method for preparing a high specific surface area, high entropy oxide catalyst as described in claim 1, characterized in that: Includes the following steps: (1) Dissolve the metal salts Fe, Co, Ni, Mn and Cr in deionized water in equal molar ratios and stir until homogeneous at room temperature to obtain a mixed solution containing the metal salts. (2) Weigh solid SiO2 into an aqueous solution and stir it evenly at room temperature to obtain a uniformly dispersed SiO2 suspension. (3) Add the SiO2 suspension obtained in step (2) to the mixed solution containing metal salt obtained in step (1), heat and stir until gel state is reached; (4) The gel-like substance obtained in step (3) is placed in a high-temperature reactor, heated, and ground thoroughly to obtain a precursor powder with high-entropy metal oxides coated on the surface of SiO2. (5) The precursor powder obtained in step (4) is etched with alkali, and after being washed with water, alcohol and dried, a loose and porous high specific surface area high entropy oxide is obtained.

5. The preparation method according to claim 4, characterized in that, In step (1): the metal salt is one of nitrate, chloride, acetylacetone, and acetate; In step (1): the total molar concentration of Fe, Co, Ni, Mn and Cr in the metal salt mixed solution is 0.2 to 4 mol / L.

6. The preparation method according to claim 4, characterized in that, In step (2), the particle size of the SiO2 powder is 5-100 nm, and the specific surface area of ​​the SiO2 powder is 150-400 m². 2 / g; In step (2), the mass fraction of the SiO2 suspension is 80%, and the molar ratio of the SiO2 powder to the total metal cations in the metal nitrate in step (1) is 0.5 to 2:

1.

7. The preparation method according to claim 4, characterized in that, In step (3), the heating and stirring temperature is 70-90°C and the stirring time is 1-6h.

8. The preparation method according to claim 4, characterized in that, In step (4), the heating conditions are to raise the temperature to 350-700°C at a heating rate of 5°C / min and hold it for 3-6 hours.

9. The preparation method according to claim 4, characterized in that, In step (5), the alkali is a 0.5~2 mol / L NaOH solution; In step (5), etch with alkali at 50~80℃ for 12-48 hours; In step (5), the drying temperature is 80°C to 140°C and the drying time is 12-48h.

10. The application of the high specific surface area high entropy oxide catalyst according to claim 1 in the electrocatalytic oxygen evolution reaction.

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