High-entropy oxygen storage material and preparation method thereof

Abstract

The application provides a high-entropy oxygen storage material and a preparation method thereof, and belongs to the technical field of oxygen storage materials. (4‑n) X n O 7+δ Wherein, δ is the oxygen adsorption molar quantity, 0 < δ ≤ 1.5; X is at least five kinds of Cu, Fe, Zn, Ga, Al and Mn; and n is the doping amount of X metal elements, 0 < n ≤ 1. The preparation method of the high-entropy oxygen storage material comprises a solid-phase reaction method, a sol-gel method or an electrostatic spinning method. The oxygen storage material is modified by high-entropy based on YBaCo4O 7+δ Oxide, through the selection and content control of the doped metal elements, the synergistic effect among multiple sites is exerted, the thermal stability of the material is significantly improved, and the working temperature window is widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oxygen storage materials, in particular to a high-entropy oxygen storage material and a preparation method thereof. BACKGROUND

[0002] As an important component of automobile exhaust treatment catalyst, the oxygen storage material should have reversible oxygen storage and release function to dynamically regulate and buffer the automobile exhaust, so as to maintain the air-fuel ratio near the theoretical value. In order to improve the working life of the oxygen storage material in the application of automobile exhaust catalytic conversion and the stability under specific working conditions, it is of great significance to optimize and improve the phase structure stability and temperature operation window of the oxygen storage material itself. YBaCo4O 7+δ (YBCO) oxide is a widely studied and used oxygen storage material, but its working temperature range is narrow, and above 500℃, YBCO phase will decompose, resulting in catalytic deactivation of the automobile exhaust treatment system. In view of the above problems, based on detailed research and material optimization, high-entropy modification is finally selected to improve the thermal stability of YBCO material and inhibit its composition segregation and phase separation.

[0003] Based on the high-entropy design, YBCO is optimized and modified to obtain high-entropy YBCO (HE-YBCO). The essence of high-entropy design is to increase the number of elements in the crystal structure, induce lattice distortion of atomic configuration, and thus increase the entropy of the system driven by distortion, i.e. configuration entropy S conf It is known that Gibbs free energy G = H-TS, where H is enthalpy, T is absolute temperature, and S is entropy. If the configuration entropy S conf (S, a component of S) in the system increases, the Gibbs free energy decreases, and the thermodynamic stability of the system increases, and the phase structure stability of the material will be improved. In order to obtain high performance, reactive transition metal elements need to be introduced, and to ensure stability, elements with lower reactivity need to be introduced to enhance the strength of cation-oxygen bond. The high-entropy oxygen storage material can effectively prevent the diffusion of other component elements to its surface and induce segregation, and can effectively improve the oxygen vacancy concentration and oxygen surface exchange characteristics. Different elements have unique interactions between adjacent atoms, and high-entropy oxygen storage materials can provide a large number of unique surface binding sites. The selection and proportion of doped and substituted elements directly affect the number and local composition of reactive sites, thereby optimizing the oxygen storage properties of the material. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a high-entropy oxygen storage material and a preparation method thereof, aiming to solve the technical problem of poor thermal stability of the existing YBCO material.

[0005] In a first aspect, the present application provides a high-entropy oxygen storage material with a molecular formula of YBaCo (4-n) X n O 7+δ , wherein δ is an oxygen adsorption molar amount, 0 < δ ≤ 1.5; X is at least five of Cu, Fe, Zn, Ga, Al, and Mn; and n is a doping amount of the metal elements, 0 < n ≤ 1.

[0006] YBaCo4O7 is a new perovskite-like compound. Due to its non-stoichiometric nature of perovskite-like substances, it can release and absorb oxygen atoms (1.5 oxygen atoms per unit cell) when the ambient atmosphere or temperature changes, so the molecular formula is often written as YBaCo4O 7+δ , and the oxygen adsorption molar amount δ ranges from 0 to 1.5.

[0007] In the high-entropy oxygen storage material YBaCo (4-n) X n O 7+δ , X is a doped metal element. Doping YBaCo4O 7+δ with multiple metal elements can improve the high-temperature stability of the material.

[0008] Preferably, the X metal element includes four metal elements of Ga, Fe, Zn, and Cu, and at least one of Al and Mn.

[0009] Preferably, the molar amount of each metal element in the X metal element is equal.

[0010] In a second aspect, the present application provides a preparation method of a high-entropy oxygen storage material, including the following steps: taking a yttrium source, a barium source, a cobalt source, and a doped metal element source to prepare a high-entropy oxygen storage material.

[0011] The preparation method includes any one of a solid-phase reaction method, a sol-gel method, and an electrospinning method.

[0012] The yttrium source includes a metal oxide or a soluble salt of yttrium.

[0013] The barium source includes a metal oxide or a soluble salt of barium.

[0014] The cobalt source includes a metal oxide or a soluble salt of cobalt.

[0015] The doped metal element source includes a metal oxide or a soluble salt of the doped metal element.

[0016] Preferably, the solid-phase reaction method specifically includes:

[0017] The yttrium source, the barium source, the cobalt source and the doping metal element source are mixed with ethanol in a stoichiometric ratio, and then are calcined once, and then are ground, tabletted and calcined twice to obtain the high-entropy oxygen storage material.

[0018] In the application, the valence of the metal elements in the metal oxide does not affect the preparation of the material.

[0019] Preferably, the first calcination temperature is 800-1200 DEG C, and the second calcination temperature is 1000-1500 DEG C, and the second calcination temperature is higher than the first calcination temperature.

[0020] Preferably, the sol-gel method specifically comprises:

[0021] The yttrium source, the barium source, the cobalt source and the doping metal element source are mixed with ethanol in a stoichiometric ratio, and then are calcined once, and then are ground, tabletted and calcined twice to obtain the high-entropy oxygen storage material.

[0022] Preferably, the stabilizer comprises ethylene glycol, and the chelating agent comprises glycine and / or citric acid.

[0023] Preferably, the heating temperature is 150-400 DEG C, and the sintering temperature is 1000-1200 DEG C.

[0024] Preferably, the electrospinning method specifically comprises:

[0025] The yttrium source, the barium source, the cobalt source and the doping metal element source are mixed with ethanol in a stoichiometric ratio, and then are calcined once, and then are ground, tabletted and calcined twice to obtain the high-entropy oxygen storage material.

[0026] Preferably, the stabilizer comprises ethylene glycol, and the chelating agent comprises glycine and / or citric acid.

[0027] According to the doping tolerance principle of substitution solid solution, the atomic size, electronegativity and valence are more similar, and the solid solubility is greater.

[0028] Compared with the prior art, the present application has the beneficial effects that:

[0029] The present application provides a high-entropy oxygen storage material with a molecular formula of YBaCo (4-n) X n O 7+δ , wherein X is at least five metal elements selected from Cu, Fe, Zn, Ga, Al and Mn. The present application increases the types of elements in the crystal structure by metal doping YBaCo4O 7+δ , induces lattice distortion of atomic configuration, thereby increasing the distortion-driven entropy, i.e., the configuration entropy S conf value in the system, and obtaining a high-entropy oxygen storage material. The oxygen storage material is based on YBaCo4O 7+δ oxide and is modified by high-entropy. Through the selection and content control of the doped metal, the synergistic effect between multiple sites is exerted, the thermal stability of the material is significantly improved, and the working temperature range is widened. Test results show that the material still has good oxygen storage performance under high temperature conditions. The high-entropy oxygen storage material provided by the present application is simple to prepare, and can be obtained by solid phase reaction method, glycine complex decomposition method, sol-gel method or electrospinning method, which is convenient for large-scale promotion. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 XRD patterns of the high-entropy oxygen storage material sample prepared in Example 1 and after heat preservation at 600 DEG C in air for 10h;

[0031] Figure 2 XRD patterns of the high-entropy oxygen storage material sample prepared in Example 2 and after heat preservation at 600 DEG C in air for 10h;

[0032] Figure 3 XRD patterns of the high-entropy oxygen storage material sample prepared in Comparative Example 1 and after heat preservation at 600 DEG C in air for 10h;

[0033] Figure 4 XRD patterns of the high-entropy oxygen storage material sample prepared in Comparative Example 2 and after heat preservation at 600 DEG C in air for 10h;

[0034] Figure 5 XRD patterns of the high-entropy oxygen storage material sample prepared in Comparative Example 3 and after heat preservation at 600 DEG C in air for 10h;

[0035] Figure 6 Oxygen storage performance effect diagram of the high-entropy oxygen storage material sample prepared in Example 1 under the condition of 350 DEG C. DETAILED DESCRIPTION

[0036] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0037] Unless otherwise specified in the examples, the techniques or conditions are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. Unless otherwise specified, the reagents or instruments used are all conventional products that can be obtained commercially.

[0038] I. Preparation method

[0039] Example 1 Sol-gel method for preparing high-entropy oxygen storage material powder

[0040] YBaCo3Ga 0.2 Al 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ The preparation method of YBaCo3Ga

[0041] (1) According to the molar ratio of 1:1:3:0.2:0.2:0.2:0.2:0.2, each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2, Ga(NO3)3, Al(NO3)3, Fe(NO3)3, Zn(NO3)2, Cu(NO3)2 is weighed, the metal nitrate is dissolved in deionized water, and ethylene glycol and citric acid are added as chelating agents, the total molar ratio of metal ions, ethylene glycol and citric acid is 1:1:1.5, and the pH value is adjusted to 7 after stirring uniformly Slowly add ammonia water;

[0042] (2) The solution is heated and stirred at 120°C until it becomes a gel, then the gel is dried at 350°C for 4h to obtain a porous precursor, the precursor is ground into powder, then it is sintered in air at a heating rate of 5°C / min to 1000°C for 2h, and finally cooled to room temperature. Natural cooling, obtain high-entropy oxygen storage material powder.

[0043] It has been verified that the molecular formula of the obtained high-entropy oxygen storage material is YBaCo3Ga 0.2 Al 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ .

[0044] Example 2 Sol-gel method for synthesizing high-entropy oxygen storage material powder

[0045] YBaCo3Ga 0.2 Mn 0.2 Fe0.2 Zn 0.2 Cu 0.2 O 7+δ The preparation method of YBaCo3Ga

[0046] (1) Each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2, Ga(NO3)3, Mn(NO3)2, Fe(NO3)3, Zn(NO3)2, Cu(NO3)2 is weighed according to the molar ratio of 1:1:3:0.2:0.2:0.2:0.2:0.2, the metal nitrate is dissolved in 0.2 mol / L glycine solution, and stirred at 40°C to form a uniform solution;

[0047] (2) Ethylene glycol (EG) is added to the solution to form a metal-glycine complex by a chelation process, the obtained transparent red solution is stirred at 100°C for 3h, a gel is obtained, and then a black honeycomb-like precursor is formed after pyrolysis at 150°C in air for 3.5h;

[0048] (3) After the precursor is ground into powder, it is sintered at 1050°C in air at a rate of 3°C / min for 4h, and finally naturally cooled to room temperature to obtain high-entropy oxygen storage material powder.

[0049] It is verified that the molecular formula of the obtained high-entropy oxygen storage material is YBaCo3Ga 0.2 Mn 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ .

[0050] Example 3 Sol-gel method for synthesizing high-entropy oxygen storage material powder

[0051] YBaCo 3.5 Ga 0.1 Al 0.1 Fe 0.1 Zn 0.1 Cu 0.1 O 7+δ The preparation method comprises the following steps:

[0052] (1) Each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2, Ga(NO3)3, Al(NO3)3, Fe(NO3)3, Zn(NO3)2, Cu(NO3)2 is weighed according to the molar ratio of 1:1:3.5:0.1:0.1:0.1:0.1:0.1, the metal nitrate is dissolved in deionized water, and ethylene glycol and citric acid are added as chelating agents, the total molar ratio of metal ions, ethylene glycol and citric acid is 1:1:1.5, and ammonia water is slowly added after stirring to adjust the pH value to 7;

[0053] (2) The solution is heated and stirred at 120°C until it becomes a gel, then the gel is dried at 350°C for 4h to obtain a porous precursor, after the precursor is ground into powder, it is sintered in air at a heating rate of 5°C / min to 1000°C for 2h, and finally naturally cooled to room temperature to obtain a high-entropy oxygen storage material powder.

[0054] It is verified that the molecular formula of the obtained high-entropy oxygen storage material is YBaCo 3.5 Ga 0.1 Al 0.1 Fe 0.1 Zn 0.1 Cu 0.1 O 7+δ .

[0055] Example 4 Synthesis of high-entropy oxygen storage material powder by solid phase reaction

[0056] The preparation method of YBaCo3Ga 0.2 Al 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ includes the following steps:

[0057] (1) According to the molar ratio of 0.5:1:3:0.1:0.1:0.2:0.2:0.2, each metal oxide Y2O3, BaO, CoO, Ga2O3, Al2O3, FeO, ZnO, CuO is weighed, mixed with ball milling beads and ethanol in a ball milling tank (500r / min, 10h), then the obtained slurry-like product is filtered and dried into a powder sample, and once calcined in air at 1000°C for 12h, granulation treatment is performed to improve the morphology of the metal oxide;

[0058] (2) The once calcined sample is ground and pressed into a sheet, and then twice calcined at 1200°C for 24h to realize solid phase reaction, and after natural cooling to room temperature, the high-entropy oxygen storage material powder is obtained by grinding and ball milling.

[0059] It is verified that the molecular formula of the obtained high-entropy oxygen storage material is YBaCo3Ga 0.2 Al 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ .

[0060] Example 5 Preparation of high-entropy oxygen storage material nanofiber by electrospinning method

[0061] The preparation method of YBaCo3Ga 0.2 Al0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ The preparation method comprises the following steps:

[0062] (1) each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2, Ga(NO3)3, Al(NO3)3, Fe(NO3)3, Zn(NO3)2, Cu(NO3)2 is weighed according to the molar ratio of 1:1:3:0.2:0.2:0.2:0.2:0.2, the metal nitrate is dissolved in deionized water, the solution contains 70% water (mass fraction, the same below), then citric acid and ethylene glycol aqueous solution (ammonia water is used to adjust the pH of citric acid and ethylene glycol aqueous solution to 5, and the solution contains 58% water) is added, and the mixture is stirred and mixed uniformly, wherein the molar ratio of the total metal ions, citric acid and ethylene glycol is 1:2:3;

[0063] The solution is placed in a 80℃ water bath for stirring for 5h to obtain a sol, polyvinylpyrrolidone (PVP, molecular weight 1300000) is dissolved in deionized water to prepare a PVP aqueous solution with a mass fraction of 15%, a certain amount of PVP aqueous solution is added to the sol, and magnetic stirring is carried out for 10h to obtain a precursor solution with a PVP content of 3%; the precursor solution is injected into a syringe with a stainless steel needle (diameter 0.8mm) and installed on a syringe pump, the electrospinning voltage is set to 12kV, the distance between the needle and the collector is 10cm, and the supply rate of the precursor solution is 0.3mL / h. After the precursor fiber obtained in this way is dried, it is heat treated at 1000℃ for 2h to obtain high-entropy oxygen storage material nanofiber. It has been verified that the molecular formula of the obtained high-entropy oxygen storage material is YBaCo3Ga 0.2 Al 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ .

[0064] Comparative Example 1

[0065] This comparative example uses the preparation method of Example 1, and the preparation steps are the same as those of Example 1. The difference between this comparative example and Example 1 is that the molar ratio of each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2 used in preparation is 1:1:4; it has been verified that the molecular formula of the obtained high-entropy oxygen storage material is YBaCo4O 7+δ .

[0066] Comparative Example 2

[0067] The comparative example adopts the preparation method of Example 1, and the preparation steps are the same as those of Example 1. The difference between the comparative example and Example 1 is that in the comparative example, the molar ratio of each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2, Ga(NO3)3, Ni(NO3)2, Fe(NO3)3, Zn(NO3)2 and Cu(NO3)2 is 1:1:3:0.2:0.2:0.2:0.2:0.2, and the target high-entropy oxygen storage material YBaCo3Ga 0.2 Ni 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ However, X-ray diffraction (XRD) characterization (as shown in Figure 4 ) shows that a mixed peak appears when Ni is doped, and a uniform oxide solid solution is not formed, indicating that the Ni element is not successfully doped into the YBCO lattice, but is mixed in the powder product in the form of NiO.

[0068] Comparative Example 3

[0069] The comparative example adopts the preparation method of Example 1, and the preparation steps are the same as those of Example 1. The difference between the comparative example and Example 1 is that in the comparative example, the molar ratio of each metal nitrate Y(NO3)3, Ba(NO3)2, Co(NO3)2, Ga(NO3)3, Sc(NO3)3, Fe(NO3)3, Zn(NO3)2 and Cu(NO3)2 is 1:1:3:0.2:0.2:0.2:0.2:0.2, and the target high-entropy oxygen storage material is YBaCo3Ga 0.2 Sc 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ However, X-ray diffraction (XRD) characterization (as shown in Figure 5 ) shows that a mixed peak appears when Sc is doped, and a uniform oxide solid solution is not formed, indicating that the Sc element is not successfully doped into the YBCO lattice, but is mixed in the powder product in the form of Sc2O3.

[0070] II. Test method

[0071] (1) Thermal stability test of high-entropy oxygen storage material

[0072] The oxygen storage material samples prepared in Examples 1-2 and Comparative Example 1 were subjected to thermal stability tests, and the oxygen storage material samples and their respective X-ray diffraction characterization after being kept at 600°C in air for 10h were characterized.

[0073] (2) High-entropy oxygen storage material oxygen storage performance test

[0074] The oxygen absorption / desorption cycle performance of the oxygen storage material samples prepared in Examples 1-5 was tested at 350℃, and the test conditions were as follows: the sample was heated to 350℃ under a pure nitrogen atmosphere and kept at constant temperature, and after the reading was stable, the atmosphere was switched to pure oxygen, and the sample was subjected to oxygen absorption until the peak value, and then switched to pure nitrogen for desorption.

[0075] III. Analysis of test results of each example and comparative example

[0076] (1) Analysis of high-entropy oxygen storage material thermal stability test results

[0077] Figure 1 is the XRD pattern of the sample of Example 1 and after heat preservation at 600℃ in air for 10h; Figure 2 is the XRD pattern of the sample of Example 2 and after heat preservation at 600℃ in air for 10h; Figure 3 is the XRD pattern of the sample of Comparative Example 1 and after heat preservation at 600℃ in air for 10h; it has been verified that the XRD spectra of the high-entropy oxygen storage materials prepared in Examples 1-2 of the present application show good peak shape after heat preservation at 600℃ in air for 10h, while the structure of the material of Comparative Example 1 is destroyed after heat preservation at 600℃ in air for 10h, indicating that the structure of the high-entropy oxygen storage material prepared in the present application has good thermal stability.

[0078] (2) Analysis of high-entropy oxygen storage material oxygen storage performance test results

[0079] The oxygen storage performance test results of the high-entropy oxygen storage material are shown in Table 1.

[0080] Table 1

[0081]

[0082] The results in Table 1 show that the high-entropy oxygen storage material prepared in the present application has good oxygen storage performance under high temperature conditions.

[0083] Figure 6 is the high-entropy oxygen storage material YBaCo3Ga 0.2 Al 0.2 Fe 0.2 Zn 0.2 Cu 0.2 O 7+δ The oxygen absorption / desorption cycle performance test spectrum of the sample at 350℃ shows highly reversible oxygen absorption / desorption behavior within three oxygen absorption / desorption cycles.

[0084] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and achieving the same effects within the scope of the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments or by combining part of the constituent elements of the embodiments are also included in the scope of the present application without departing from the spirit of the present application.

Claims

1. A high entropy oxygen storage material, characterized in that The molecular formula of the high-entropy oxygen storage material is YBaCo (4-n) X n O 7+δ , where δ is the molar amount of oxygen adsorption, 0 < δ ≤ 1.5; X is at least one of the four metal elements Ga, Fe, Zn, Cu, and Al, Mn; n is the doping amount of X, 0 < n ≤ 1; the molar amounts of each metal element in the X are equal.

2. A method for preparing the high entropy oxygen storage material according to claim 1, characterized in that: The following steps are involved: A high entropy oxygen storage material is prepared by mixing a yttrium source, a barium source, a cobalt source and a doped metal element source; The preparation method includes any one of a solid phase reaction method, a sol-gel method, and an electrospinning method; The yttrium source includes a metal oxide or a soluble salt of yttrium; The barium source includes a metal oxide or a soluble salt of barium; The cobalt source includes metal oxides or soluble salts of cobalt; The doping metal element source includes a metal oxide or a soluble salt of the doping metal element.

3. The method for preparing a high entropy oxygen storage material according to claim 2, wherein: The solid phase reaction method specifically includes: According to the stoichiometric ratio, the yttrium source, the barium source, the cobalt source and the doping metal element source are fully mixed with ethanol and calcined once, and then ground, tableted and calcined twice in sequence to obtain the high entropy oxygen storage material.

4. The method for preparing a high entropy oxygen storage material according to claim 3, wherein: The primary calcination temperature is 800-1200° C., the secondary calcination temperature is 1000-1500° C., and the secondary calcination temperature is higher than the primary calcination temperature.

5. The method for preparing a high entropy oxygen storage material according to claim 2, wherein: The sol-gel method specifically includes: According to the stoichiometric ratio, the yttrium source, barium source, cobalt source, doping metal element source, stabilizer and chelating agent are dissolved in water, heated to form a gel, and the gel is dried to form a precursor, which is ground and sintered to obtain the high entropy oxygen storage material.

6. The method for preparing a high entropy oxygen storage material according to claim 5, characterized in that: The stabilizer includes ethylene glycol, and the chelating agent includes glycine and / or citric acid; the heating temperature is 150-400° C., and the sintering temperature is 1000-1200° C.

7. The method for preparing a high entropy oxygen storage material according to claim 2, wherein: The electrospinning method specifically comprises: According to the stoichiometric ratio, the yttrium source, barium source, cobalt source, and doping metal element source, stabilizer, and chelating agent are dissolved in water, and a polyvinyl pyrrolidone solution is added and stirred to obtain a precursor solution. The precursor solution is jet-spun in an electric field to obtain a precursor fiber. After drying and heat treatment, the high entropy oxygen storage material is obtained.

8. The method for preparing a high entropy oxygen storage material according to claim 7, wherein: The stabilizer includes ethylene glycol, and the chelating agent includes citric acid; the voltage of the electric field is 10-15V, the injection rate of the precursor solution is 0.1-0.5mL / h, and the heat treatment temperature is 800-1200°C.

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