Preparation method and application of a ce-based high-entropy oxynitride material

Abstract

The application belongs to the technical field of high-entropy materials, and particularly relates to a preparation method of Ce-based high-entropy oxynitride material and application thereof. The method comprises the following steps: (1) dissolving a titanium precursor in ethylene glycol, adding HE metal salt and citric acid to obtain a mixed solution; (2) heating the mixed solution obtained in step (1) to obtain a gel precursor; (3) heat-treating the gel precursor obtained in step (2); and (4) treating the powder obtained in step (3) with ammonia nitriding to obtain the high-entropy oxynitride material. The high-entropy oxynitride material prepared by the application is easy to adjust in metal type, and the preparation method is simple and controllable, and the preparation conditions are mild and universal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-entropy materials, and particularly relates to a preparation method of Ce-based high-entropy oxynitride material and application thereof. BACKGROUND

[0002] As a new type of material, high-entropy materials have attracted widespread attention in recent years. The concept of high-entropy was first developed from high-entropy alloys, which was first proposed by Professor Ye Wucheng in 2004, and then gradually expanded to other material systems. At present, this kind of material mainly refers to single-phase alloys or solid solution materials composed of four or more components with similar element contents (Science, 2022, 376, eabn3103; Sci. Adv., 2021, 7, eabg1600; J. Mater. Chem. A, 2020, 8, 3814-3821). High-entropy materials have the characteristics of diverse and adjustable components, and exhibit four unique effects, including high-entropy effect, lattice distortion effect, sluggish diffusion effect and cocktail effect, which make them have great application potential in the fields of materials, energy, environment, catalysis and the like.

[0003] Perovskite oxynitride materials have wide spectral visible light response capability and exhibit excellent performance in the fields of solar energy utilization, catalysis and the like (J. Am. Chem. Soc., 2012, 134, 20, 8348-8351; Adv. Mater., 2021, 33, 2101883; Nat. Commun., 2021, 12, 1005). However, the synthesis process of oxynitride often requires high-temperature conditions, which puts high requirements on the synthesis equipment. Especially Ce-based oxynitride, such as CeTiO2N, needs to be calcined at 1200℃ for 8h in a platinum boat, and then synthesized by nitriding at 950℃ for 20h (Chem. Mater., 2015, 27, 2414-2420). The unique effects of high-entropy oxynitride materials not only can reduce the preparation temperature, but also can provide multifunctional active sites for complex catalytic reactions, and regulate the electronic properties of the materials, thereby laying a foundation for precise regulation of catalytic activity and selectivity. However, the preparation technology of high-entropy oxynitride materials is very limited. There are still great challenges in the development of new high-entropy oxynitride material preparation technology. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of Ce-based high-entropy oxynitride material and application thereof to solve the above problems.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0006] The application provides a preparation method of a Ce-based high-entropy oxynitride material.

[0007] The method comprises the following steps:

[0008] (1) dissolving a titanium precursor in ethylene glycol, adding HE metal salt and citric acid to obtain a mixed solution;

[0009] (2) heating the mixed solution obtained in step (1) to obtain a gel precursor;

[0010] (3) heat treating the gel precursor obtained in step (2);

[0011] (4) treating the powder obtained in step (3) with ammonia nitriding to obtain the high-entropy oxynitride material.

[0012] In the technical solution, further, in step (1), the molar ratio of the citric acid to all the metals is 2:1-6:1;

[0013] The molar ratio of the ethylene glycol to all the metals is 10:1-30:1;

[0014] The molar ratio of the HE metal to Ti is 1:1.

[0015] In the technical solution, further, in step (1), the HE metal salt is a nitrate, an acetate or a chloride of the HE;

[0016] The titanium precursor is one of tetrabutyl titanate, tetraisopropyl titanate and tetraethyl titanate.

[0017] In the technical solution, further, in step (2), the heating temperature is 110-160 DEG C, and the holding time is 3-18 hours.

[0018] In the technical solution, further, in step (3), the heat treatment is first heating to 300-350 DEG C and keeping for 1-3 hours, and then heating to 600-1000 DEG C and keeping for 1-5 hours.

[0019] In the technical solution, further, in step (3), the heat treatment is in a hydrogen atmosphere or a mixed hydrogen and argon atmosphere.

[0020] In the technical solution, further, in step (4), the nitriding temperature is 800-1200 DEG C, and the holding time is 1-5 hours.

[0021] Another aspect of the present application provides an application of the high-entropy oxynitride material in a photocatalytic reaction.

[0022] The present application has the following advantages:

[0023] 1. The present application realizes the uniform mixing of the HE metal salt, the titanium precursor and the citric acid by regulating the adding sequence of the precursors and the dissolving temperature, and the high-entropy oxynitride material is prepared by the method of dissolving-polymerizing-calcining-nitriding. The metal type of the prepared high-entropy oxynitride material is easy to adjust, and the method is universal.

[0024] 2. The preparation method of the present application is simple and controllable, and the conditions are mild.

[0025] 3. The high-entropy oxynitride material prepared by the present application has a perovskite structure and a wide-spectrum solar energy absorption characteristic. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 XRD characterization of the samples prepared for Example 1 and Comparative Example 1;

[0027] Figure 2 Photocatalytic ammonia decomposition hydrogen production performance of the sample prepared for Example 1. DETAILED DESCRIPTION

[0028] The entire material preparation process is described in detail below through examples, but the scope of the claims of the present application is not limited by these examples. At the same time, the examples only give part of the conditions to achieve the purpose, but do not mean that these conditions must be met to achieve the purpose.

[0029] The materials of Examples 1-10 of the present application are detected by the following instruments and methods:

[0030] The structure information of the examples is analyzed by X-ray diffraction spectrum (XRD);

[0031] Examples 1-3 are for adjusting the metal type and number; Examples 3-5 are for adjusting the polymerization temperature and time; Examples 6-8 are for adjusting the heat treatment temperature and time; and Examples 8-10 are for adjusting the nitriding temperature and the time of passing in ammonia gas.

[0032] Example 1

[0033] (1) 5 mmol of tetrabutyl titanate was dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3 and Pr(NO3)3 was added respectively, and 20 mmol of citric acid was added to obtain a mixed solution;

[0034] (2) Place the mixed solution obtained in step (1) in an oil bath and stir at 130°C for 6 hours. After cooling to room temperature, the gel precursor is obtained.

[0035] (3) Place the gel precursor obtained in step (2) in a tube furnace, and heat it to 350°C at a program of 5°C / min under a mixed atmosphere of H2 and Ar, and hold it for 2 hours. After grinding, heat it to 900°C and hold it for 3 hours.

[0036] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 950°C at a flow rate of 250 mL / min under an ammonia atmosphere. The temperature is maintained for 3 hours to obtain high-entropy nitrogen oxides (LaCePrNdSm)TiO2N.

[0037] like Figure 1 As shown, the Ce-based high-entropy nitrides prepared in Example 1 have a single perovskite-type structure.

[0038] Example 2

[0039] (1) Dissolve 5 mmol of tetrabutyl titanate in 12 mL of ethylene glycol, and add 1 mmol each of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, and Gd(NO3)3 and 20 mmol of citric acid.

[0040] (2) Place the mixed solution obtained in step (1) in an oil bath and stir at 130°C for 6 hours. After cooling to room temperature, the gel precursor is obtained.

[0041] (3) Place the gel precursor obtained in step (2) in a tube furnace, and heat it to 350°C at a program of 5°C / min under a mixed atmosphere of H2 and Ar, and hold it for 2 hours. After grinding, heat it to 900°C and hold it for 3 hours.

[0042] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 950°C at a flow rate of 250 mL / min under an ammonia atmosphere. The temperature is maintained for 3 hours to obtain high-entropy nitrogen oxides (LaCeSmNdGd)TiO2N.

[0043] Example 3

[0044] (1) Dissolve 6 mmol of tetrabutyl titanate in 12 mL of ethylene glycol, add 1 mmol each of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, Pr(NO3)3, and Gd(NO3)3 and 24 mmol of citric acid to obtain a mixed solution;

[0045] (2) The mixed solution obtained in step (1) is placed in an oil bath at 130°C and stirred for 6 hours. After cooling to room temperature, a gel precursor is obtained;

[0046] (3) The gel precursor obtained in step (2) is placed in a tube furnace and heated to 350°C at a rate of 5°C / min under a mixed gas atmosphere of H2 and Ar, and kept for 2 hours. After grinding, the temperature is raised to 900°C and kept for 3 hours;

[0047] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 950°C at a rate of 5°C / min under an ammonia gas atmosphere with a flow rate of 250 mL / min, and kept for 3 hours, to obtain a high-entropy oxynitride (LaCeNdPrSmGd)TiO2N.

[0048] Results and discussion: In the same other conditions, by adjusting the types and amounts of metals, high-entropy oxynitride materials with perovskite structure can be prepared in Examples 1-3.

[0049] Example 4

[0050] (1) 6 mmol of tetrabutyl titanate is dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, Pr(NO3)3, and Gd(NO3)3 are added, and 24 mmol of citric acid is added to obtain a mixed solution;

[0051] (2) The mixed solution obtained in step (1) is placed in an oil bath at 110°C and stirred for 18 hours. After cooling to room temperature, a gel precursor is obtained;

[0052] (3) The gel precursor obtained in step (2) is placed in a tube furnace and heated to 350°C at a rate of 5°C / min under a mixed gas atmosphere of H2 and Ar, and kept for 2 hours. After grinding, the temperature is raised to 900°C and kept for 3 hours;

[0053] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 950°C at a rate of 5°C / min under an ammonia gas atmosphere with a flow rate of 250 mL / min, and kept for 3 hours, to obtain a high-entropy oxynitride (LaCeNdPrSmGd)TiO2N.

[0054] Example 5

[0055] (1) 6 mmol of tetrabutyl titanate is dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, Pr(NO3)3, and Gd(NO3)3 are added, and 24 mmol of citric acid is added to obtain a mixed solution;

[0056] (2) The mixed solution obtained in step (1) is placed in an oil bath at 160°C for stirring for 3 hours, and after being cooled to room temperature, a gel precursor is obtained;

[0057] (3) The gel precursor obtained in step (2) is placed in a tube furnace, and is heated to 350°C at a rate of 5°C / min under a mixed gas atmosphere of H2 and Ar, and is kept for 2 hours, and after being ground, the temperature is raised to 900°C and is kept for 3 hours;

[0058] (4) The powder obtained in step (3) is placed in a tube furnace, and is heated to 950°C at a rate of 5°C / min under an ammonia gas atmosphere with a flow rate of 250 mL / min, and is kept for 3 hours, to obtain a high-entropy oxynitride (LaCeNdPrSmGd)TiO2N.

[0059] Result discussion: Examples 3-5 can all obtain high-entropy oxynitride materials with perovskite structure by changing the polymerization temperature and time under the premise of other consistent conditions.

[0060] Example 6

[0061] (1) 5 mmol of tetrabutyl titanate is dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3 and Pr(NO3)3 is added respectively, and 20 mmol of citric acid is added to obtain a mixed solution;

[0062] (2) The mixed solution obtained in step (1) is placed in an oil bath at 130°C for stirring for 6 hours, and after being cooled to room temperature, a gel precursor is obtained;

[0063] (3) The gel precursor obtained in step (2) is placed in a tube furnace, and is heated to 300°C at a rate of 5°C / min under a mixed gas atmosphere of H2 and Ar, and is kept for 3 hours, and after being ground, the temperature is raised to 1000°C and is kept for 1 hour;

[0064] (4) The powder obtained in step (3) is placed in a tube furnace, and is heated to 900°C at a rate of 5°C / min under an ammonia gas atmosphere with a flow rate of 250 mL / min, and is kept for 3 hours, to obtain a high-entropy oxynitride (LaCePrNdSm)TiO2N.

[0065] Example 7

[0066] (1) 5 mmol of tetrabutyl titanate is dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3 and Pr(NO3)3 is added respectively, and 20 mmol of citric acid is added to obtain a mixed solution;

[0067] (2) The mixed solution obtained in step (1) is placed in an oil bath at 130°C and stirred for 6 hours. After cooling to room temperature, a gel precursor is obtained;

[0068] (3) The gel precursor obtained in step (2) is placed in a tube furnace and heated to 350°C at a rate of 5°C / min under a mixed gas atmosphere of H2 and Ar, and kept for 2 hours. After grinding, the temperature is raised to 600°C and kept for 5 hours;

[0069] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 900°C at a rate of 5°C / min under an ammonia gas atmosphere with a flow rate of 250 mL / min, and kept for 3 hours, to obtain a high-entropy oxynitride (LaCePrNdSm)TiO2N.

[0070] Example 8

[0071] (1) 5 mmol of tetrabutyl titanate is dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, and Pr(NO3)3 is added, and 20 mmol of citric acid is added to obtain a mixed solution;

[0072] (2) The mixed solution obtained in step (1) is placed in an oil bath at 130°C and stirred for 6 hours. After cooling to room temperature, a gel precursor is obtained;

[0073] (3) The gel precursor obtained in step (2) is placed in a tube furnace and heated to 350°C at a rate of 5°C / min under a mixed gas atmosphere of H2 and Ar, and kept for 2 hours. After grinding, the temperature is raised to 900°C and kept for 3 hours;

[0074] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 900°C at a rate of 5°C / min under an ammonia gas atmosphere with a flow rate of 250 mL / min, and kept for 3 hours, to obtain a high-entropy oxynitride (LaCePrNdSm)TiO2N.

[0075] Results and discussion: In Examples 6-8, under the same other conditions, by changing the heat treatment temperature and time, a high-entropy oxynitride material with a perovskite structure can be obtained.

[0076] Example 9

[0077] (1) 5 mmol of tetrabutyl titanate is dissolved in 12 mL of ethylene glycol, 1 mmol of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, and Pr(NO3)3 is added, and 20 mmol of citric acid is added to obtain a mixed solution;

[0078] (2) Place the mixed solution obtained in step (1) in an oil bath and stir at 130°C for 6 hours. After cooling to room temperature, the gel precursor is obtained.

[0079] (3) Place the gel precursor obtained in step (2) in a tube furnace, and heat it to 350°C at a program of 5°C / min under a mixed atmosphere of H2 and Ar, and hold it for 2 hours. After grinding, heat it to 900°C and hold it for 3 hours.

[0080] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 1200°C at a flow rate of 250 mL / min under an ammonia atmosphere. The temperature is maintained for 1 hour at a program of 5°C / min to obtain high-entropy nitrogen oxides (LaCePrNdSm)TiO2N.

[0081] Example 10

[0082] (1) Dissolve 5 mmol of tetrabutyl titanate in 12 mL of ethylene glycol, add 1 mmol each of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3, and Pr(NO3)3 and 20 mmol of citric acid to obtain a mixed solution;

[0083] (2) Place the mixed solution obtained in step (1) in an oil bath and stir at 130°C for 6 hours, then let it cool to room temperature;

[0084] (3) Place the gel precursor obtained in step (2) in a tube furnace, and heat it to 350°C at a program of 5°C / min under a mixed atmosphere of H2 and Ar, and hold it for 2 hours. After grinding, heat it to 900°C and hold it for 3 hours.

[0085] (4) Place the powder obtained in step (3) in a tube furnace and heat it to 800°C at a flow rate of 250 mL / min under an ammonia atmosphere. Hold the temperature for 5 hours to obtain high entropy nitrogen oxide (LaCePrNdSm)TiO2N.

[0086] Results and Discussion: Under the same conditions, Examples 8-10 demonstrated how the formation process of nitrogen oxides was controlled by adjusting the ammonia gas introduction time and nitriding temperature. Increasing the nitriding time and temperature promoted the formation of nitrogen oxides and improved crystallinity.

[0087] Comparative Example 1

[0088] Add 0.6 g of anhydrous sodium carbonate, 1 mmol each of Sm₂O₃, La₂O₃, Nd₂O₃, and Ce₂O₃, and 0.33 mmol of Pr₆O₃. 1110 mmol TiO2 was mixed uniformly by ball milling at a ball-to-material ratio of 10:1, a speed of 600 r / min, and a milling time of 0.5 hours. The resulting mixture was then calcined in a muffle furnace at 900 °C for 3 hours at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain the precipitate, which was then dried at 60 °C for 12 hours. The dried sample was then placed in a tube furnace and heated to 950 °C at a flow rate of 250 mL / min under an ammonia atmosphere, with the temperature programmed to increase at 5 °C / min and held for 3 hours to obtain nitrogen oxides (LaCeSmNdPr)TiO2. x N y .

[0089] Results and Discussion: Under the same conditions, the molten salt method cannot obtain single-phase perovskite structured nitrides, indicating that the technique proposed in this invention for preparing high-entropy nitride materials has high purity, mild conditions, and a simple method.

[0090] Comparative Example 2

[0091] (1) Dissolve 1 mmol each of La(NO3)3, Ce(NO3)3, Sm(NO3)3, Nd(NO3)3 and Pr(NO3)3 in 12 mL of ethylene glycol, add 5 mmol of tetrabutyl titanate and 20 mmol of citric acid to obtain a mixed solution;

[0092] (2) Place the mixed solution obtained in step (1) in an oil bath and stir at 130°C for 6 hours. After cooling to room temperature, the gel precursor is obtained.

[0093] (3) Place the gel precursor obtained in step (2) in a tube furnace, and heat it to 350°C at a program of 5°C / min under a mixed atmosphere of H2 and Ar, and hold it for 2 hours. After grinding, heat it to 900°C and hold it for 3 hours.

[0094] (4) The powder obtained in step (3) is placed in a tube furnace and heated to 950°C at a flow rate of 250 mL / min under an ammonia atmosphere. The temperature is maintained for 3 hours to obtain nitrogen oxide [LaCePrNdSm]TiO2N.

[0095] Results and Discussion: The resulting mixed solution had a white precipitate attached, indicating that the present invention can obtain high-purity high-entropy nitrogen oxide materials by adjusting the order of addition.

[0096] Application Example 1

[0097] The high-entropy nitrogen oxides obtained in Example 1 were used as catalyst materials for the photocatalytic ammonia decomposition hydrogen production system. The performance of the photocatalytic ammonia decomposition hydrogen production reaction after ruthenium loading was investigated.

[0098] 1. Additive Modification: A high-entropy nitride with a ruthenium loading of 1 wt%, namely Ru / (LaCePrNdSm)TiO2N, was prepared by impregnation. First, the high-entropy nitride material was impregnated in a solution containing ruthenium chloride. After stirring, drying, and grinding, it was heated to 300℃ and held for 2 hours under a 5% H2 / Ar atmosphere.

[0099] 2. Catalytic performance evaluation: 20 mg Ru / (LaCePrNdSm)TiO2N was coated onto a 2*2 cm layer. 2 The sample was placed on a quartz plate in a photocatalytic reactor. Ammonia gas was introduced as the reaction gas, and the temperature was raised to 150°C under visible light (λ > 420 nm) irradiation. The hydrogen products were detected by gas chromatography-mass spectrometry to evaluate the hydrogen production performance of the high-entropy nitrogen oxide photocatalyst through ammonia decomposition.

[0100] like Figure 2 As shown, the high-entropy nitrogen oxides prepared in Example 1 have the ability to photocatalyze the decomposition of ammonia to produce hydrogen under visible light conditions.

[0101] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a Ce-based high-entropy oxynitride material, characterized in that, The chemical formula of this nitride material is HETiO2N, where HE is a combination of Ce and at least four selected from La, Sm, Pr, Nd, Gd, Yb, Tb, Eu, Ho, Er, Tm, Lu, and Dy; the percentage of each HE metal element in the total number of HE metal elements is 5% to 35%. The method includes the following steps: (1) Dissolve the titanium precursor in ethylene glycol, add HE metal salt and citric acid to obtain a mixed solution; (2) Heating the mixed solution obtained in step (1) yields a gel precursor; (3) Heat-treat the gel precursor obtained in step (2); (4) The powder obtained in step (3) is nitrided with ammonia to obtain the high-entropy nitrogen oxide material.

2. The method for preparing high-entropy nitride materials according to claim 1, characterized in that, In step (1), the molar ratio of citric acid to all metals is 2:1 to 6:1; The molar ratio of ethylene glycol to all metals is 10:1 to 30:1; The molar ratio of HE metal to Ti is 1:

1.

3. The method for preparing high-entropy nitride materials according to claim 1, characterized in that, In step (1), the HE metal salt is a nitrate, acetate, or chloride of HE; The titanium precursor is one of tetrabutyl titanate, tetraisopropyl titanate, and tetraethyl titanate.

4. The method for preparing high-entropy nitride materials according to claim 1, characterized in that, In step (2), the heating temperature is 110~160℃. o C, the heat preservation time is 3~18 hours.

5. The method for preparing high-entropy nitride materials according to claim 1, characterized in that, In step (3), the heat treatment involves first heating the temperature to 300~350°C. o Hold at 600-1000°C for 1-3 hours, then increase the temperature to 600-1000°C. o C, keep for 1-5 hours.

6. The method for preparing high-entropy nitride materials according to claim 1, characterized in that, In step (3), the atmosphere for the heat treatment is hydrogen or a mixture of hydrogen and argon.

7. The method for preparing high-entropy nitride materials according to claim 1, characterized in that, In step (4), the nitriding temperature is 800~1200℃. o C, the heat preservation time is 1~5 hours.

8. The application of a Ce-based high-entropy nitride material prepared by the preparation method according to any one of claims 1-7 in photocatalysis.

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