Nitride ta3n5, preparation method and application thereof

Abstract

This invention discloses a nitride Ta3N5, its preparation method, and its applications. Specifically, the method involves high-temperature hydrolysis of precursor I to prepare smaller-sized TaO. x Using TaO x Due to its amorphous shape and small particle radius, Ta3N5 nitride can be prepared in a short time by nitriding, which effectively reduces the formation of low-valence metal defects and improves charge separation efficiency. It exhibits water-splitting activity in photocatalytic water splitting reaction, and its activity is significantly improved compared with Ta3N5 prepared by conventional methods.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material synthesis and renewable clean energy utilization, and particularly relates to a nitride Ta3N5 and a preparation method and application thereof. BACKGROUND

[0002] The (oxy)nitride compounds have suitable band gaps and conduction / valence band positions, can be used for decomposing water, and are considered as a kind of visible light response photocatalyst with great attraction. However, the (oxy)nitride photocatalysts are generally synthesized by a high-temperature solid phase method, the precursor particle radius is large, and a longer time is needed to completely nitride, so more anion vacancies or low-valence metal species are inevitably generated, and the anion vacancies or low-valence metal species are generally considered as recombination centers, which can reduce the photocatalyst activity.

[0003] The traditional synthesis method of the nitride Ta3N5 is to directly nitride the oxide precursor Ta2O5. However, due to the large particle size of the precursor and the long high-temperature nitriding process, the low-valence defect density is increased, and the charge separation ability is reduced.

[0004] Currently, researchers have made many attempts to inhibit the defects of the oxy-nitride compounds, mainly including:

[0005] (1) doping low-valence metals, that is, inhibiting the generation of low-valence metal defects by doping low-valence metal species (such as Mg, Sc, Zr, etc.) which are not easy to be reduced;

[0006] (2) molten salt-assisted nitriding, that is, by molten salt-assisted nitriding, the synthesis path is changed, and the material activity is improved, such as using Na2CO3 to assist the nitriding of the Ta2O5 precursor, first generating Na2Ta2O6, and then volatilizing potassium ions to generate Ta3N5 by nitriding;

[0007] (3) reducing the nitriding time, that is, by short-time high-temperature nitriding of the KTaO3 precursor, high-quality, low-defect Ta3N5 nanorods are obtained at the edge of the KTaO3, unfortunately, short-time nitriding cannot completely convert the oxide precursor into the (oxy)nitride compound, and the Ta3N5 nanorods are mainly located on the surface of the material.

[0008] The above three methods have their advantages, but for inhibiting low-valence metal defects, the strategy of reducing the nitriding time has the highest priority, because the number of low-valence metal defects can be subsequently regulated by changing the precursor or the type of molten salt.

[0009] The traditional method of reducing the nitriding time is mainly achieved by reducing the geometric size of the precursor, and the specific method is to prepare the oxide precursor by a sol-gel method. SUMMARY

[0010] This section is intended to introduce some aspects of embodiments of the present application, which are described below. This section is not intended to limit the scope or the patentability of the embodiments of the present application.

[0011] In view of the above and / or existing problems in the prior art, the present application is proposed.

[0012] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, and provide a preparation method of nitride Ta3N5.

[0013] To solve the above technical problems, the present application provides the following technical solutions:

[0014] The precursor I is high-temperature hydrolyzed to obtain amorphous product TaO x ;

[0015] TaO x High-temperature nitriding obtains Ta3N5;

[0016] The precursor I includes ATaP2O8 and A3TaP2O9, and A is selected from any one of K and Na.

[0017] As a preferred scheme of the preparation method of the nitride Ta3N5, the temperature of the high-temperature hydrolysis of the precursor I is 80-100℃, and the time is 1-2h.

[0018] As a preferred scheme of the preparation method of the nitride Ta3N5, the high-temperature hydrolysis process of the precursor I includes adding 1-5M AOH solution, and A is selected from any one of K and Na.

[0019] As a preferred scheme of the preparation method of the nitride Ta3N5, the ATaP2O8 is prepared by high-temperature solid-phase method using A precursor, Ta precursor, P precursor, and AP mixed precursor as raw materials, and the molar ratio of A, Ta, P, and AP is 1:1:2:(0-10).

[0020] The A3TaP2O9 is prepared by high-temperature solid-phase method using A precursor, Ta precursor, P precursor, and AP mixed precursor as raw materials, and the molar ratio of A, Ta, P, and AP is 3:1:2:(0-10).

[0021] As a preferred scheme of the preparation method of the nitride Ta3N5, the A precursor includes at least one of carbonates, oxalates, and nitrates of A.

[0022] The Ta precursor is Ta2O 5；

[0023] The P precursor is NH4H2PO 4；

[0024] The AP mixed precursor comprises at least two of H3PO4, AH2PO 4、 A2HPO4.

[0025] As a preferred scheme of the preparation method of the nitride Ta3N5, in the high-temperature solid-phase method, the processing temperature is 800-900 DEG C, and the processing time is 5-15 h.

[0026] As a preferred scheme of the preparation method of the nitride Ta3N5, in the high-temperature nitriding, the ammonia gas flow is 200-300 mL / min, the temperature is 850-1000 DEG C, and the time is 3-10 h.

[0027] Another object of the present application is to provide the nitride Ta3N5 prepared by the preparation method of the nitride Ta3N5.

[0028] Another object of the present application is to provide the application of the nitride Ta3N5 in photocatalytic oxygen production

[0029] The present application has the following beneficial effects:

[0030] The present application can prepare the TaO x with small size by high-temperature hydrolysis of the precursor I. x The amorphous and small-particle-radius TaO BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor. Among them:

[0032] Figure 1 The scanning electron microscope images of the Ta3N5 prepared in the present application example 1 and comparative examples 1 and 2.

[0033] Figure 2 The XRD images of the Ta3N5 prepared in the present application example 1 and comparative examples 1 and 2.

[0034] Figure 3 The decomposition water production oxygen activity chart of Ta3N5 prepared for the embodiment 1 and the comparative examples 1 and 2 of the present application. DETAILED DESCRIPTION

[0035] In order to make the above objectives, features and advantages of the present application more apparent, the specific embodiments of the present application will be described in detail below with reference to the embodiments of the present application.

[0036] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the concept of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0037] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent of or mutually exclusive with other embodiments.

[0038] The raw materials used in the present application are commercially available in the art without special description.

[0039] Embodiment 1

[0040] The present embodiment provides a preparation method of Ta3N5, specifically:

[0041] 1) Synthesis of precursor I:

[0042] According to the molar ratio of Na, Ta, P, AP(1), AP(2) being 3:1:2:2:2, Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 are mixed and ground to make them uniformly mixed, and then calcined at 900℃ for 8h to prepare the precursor I Na3TaP2O9.

[0043] 2) High temperature hydrolysis of precursor I:

[0044] The precursor I Na3TaP2O9 is heated in water bath, the heating temperature is 80℃, and the time is 1h, and after hydrothermal treatment, the powder is obtained by cooling and centrifugation, which is the amorphous product TaO x , wherein the supernatant is directly cooled and centrifuged, and the lower precipitate is repeatedly heated in water bath as many times as possible to dissolve the precipitate, and then cooled and centrifuged to obtain the amorphous product TaO x .

[0045] 3) TaO x High temperature nitriding:

[0046] TaO x The nitride Ta3N5 was obtained by nitriding at 900°C for 5h under the ammonia gas flow of 250mL / min, and was recorded as Ta3N5-KP.

[0047] Comparative Example 1

[0048] This comparative example provides another method for synthesizing the nitride Ta3N5, which is as follows:

[0049] 1) Synthesis of precursor I:

[0050] Na2CO3, Ta2O5, NH4H2PO4, and NaH2PO4 were mixed and ground according to the molar ratio of Na:Ta:P:AP(1):AP(2) of 3:1:2:2:2, and were mixed uniformly. The mixture was calcined at 900°C for 8h to obtain the precursor I Na3TaP2O9.

[0051] 2) High-temperature nitriding of Na3TaP2O9:

[0052] The nitride Ta3N5 was obtained by nitriding Na3TaP2O9 at 950°C for 15h under the ammonia gas flow of 250mL / min, and was recorded as Ta3N5-2.

[0053] Comparative Example 2

[0054] This comparative example provides another method for synthesizing the nitride Ta3N5, which is as follows:

[0055] 1) Synthesis of precursor I:

[0056] Na2CO3, Ta2O5, NH4H2PO4, and NaH2PO4 were mixed and ground according to the molar ratio of Na:Ta:P:AP(1):AP(2) of 3:1:2:2:2, and were mixed uniformly. The mixture was calcined at 900°C for 8h to obtain the precursor I Na3TaP2O9.

[0057] 2) High-temperature nitriding of Na3TaP2O9:

[0058] The nitride Ta3N5 was obtained by nitriding Na3TaP2O9 at 950°C for 15h under the ammonia gas flow of 250mL / min, and was recorded as Ta3N5-2.

[0059] Figure 1 The scanning electron microscope images of the nitride Ta3N5 obtained in Example 1 and Comparative Examples 1 and 2 are shown in FIG. 1. Figure 2The XRD patterns of Example 1 and Comparative Examples 1 and 2 can prove that the nitride Ta3N5 is successfully synthesized according to the scheme of the examples and comparative examples.

[0060] Application test

[0061] The nitride Ta3N5 synthesized according to the examples or comparative examples is used for the photocatalytic oxygen evolution reaction, and the reaction conditions include:

[0062] 500 mg of Ta3N5 sample loaded with 2 wt% CoO x , 500 mg of La2O3, 1.6988 g of AgNO3, 200 mL of H2O, and a 300 W xenon lamp light source;

[0063] The results are shown in Table 1. Figure 3 As can be seen from Table 1, the nitride Ta3N5 prepared according to the present application can realize the photocatalytic oxygen evolution half-reaction after loading the corresponding oxygen evolution cocatalyst. With the extension of the reaction time, the oxygen evolution rate decreases, because the sacrificial agent AgNO3 is reduced to Ag element and deposited on Ta3N5, resulting in light absorption being blocked and the reaction activity being reduced, which is a common phenomenon. This experiment proves that the generated Ta3N5 has the photocatalyst oxygen evolution performance, and the photocatalyst oxygen evolution performance of the nitride prepared according to Comparative Example 1 and Comparative Example 2 is significantly improved.

[0064] Example 2

[0065] 1) Synthesis of precursor I:

[0066] Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 are mixed and ground according to the molar ratio of Na, Ta, P, AP(1), AP(2) of 3:1:2:2:2, and are mixed uniformly, and are calcined at 850℃ for 12h to prepare the precursor I Na3TaP2O9.

[0067] 2) High temperature hydrolysis of precursor I:

[0068] The precursor I Na3TaP2O9 is heated in a water bath, the heating temperature is 100℃, and the time is 1h, and after hydrothermal treatment, the powder obtained by cooling and centrifugation is the amorphous product TaO x , wherein the supernatant is directly cooled and centrifuged, and the lower layer of the precipitate is repeatedly heated in a water bath for multiple times to dissolve the solution and precipitate as much as possible, and then cooled and centrifuged to obtain the amorphous product TaO x .

[0069] 3) High temperature nitriding of TaO x

[0070] TaO x ​The nitride Ta3N5 is obtained by nitriding at a temperature of 1000°C for 3h under an ammonia gas flow of 200mL / min.

[0071] Example 3

[0072] 1) Synthesis of precursor I:

[0073] Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 are mixed and ground in a molar ratio of Na:Ta:P:AP(1):AP(2) of 3:1:2:2:2, and then uniformly mixed and calcined at 800°C for 15h to obtain the precursor I Na3TaP2O9.

[0074] 2) High-temperature hydrolysis of precursor I:

[0075] The precursor I Na3TaP2O9 is heated in a water bath at a temperature of 90°C for 2h, and then cooled, centrifuged and powdered to obtain the amorphous product TaO x , wherein the supernatant is directly cooled, centrifuged, and the lower precipitate is repeatedly heated in a water bath to dissolve the precipitate as much as possible, and then cooled and centrifuged to obtain the amorphous product TaO x .

[0076] 3) TaO x High-temperature nitriding:

[0077] TaO x The nitride Ta3N5 is obtained by nitriding at a temperature of 850°C for 9h under an ammonia gas flow of 300mL / min.

[0078] Example 4

[0079] 1) Synthesis of precursor I:

[0080] Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 are mixed and ground in a molar ratio of Na:Ta:P:AP(1):AP(2) of 3:1:2:2:2, and then uniformly mixed and calcined at 900°C for 5h to obtain the precursor I Na3TaP2O9.

[0081] 2) High-temperature hydrolysis of precursor I:

[0082] The precursor I Na3TaP2O9 is heated in a water bath at a temperature of 80°C for 2h, and then cooled, centrifuged and powdered to obtain the amorphous product TaO xThe supernatant is directly cooled and centrifuged, the lower precipitate is repeatedly heated in a water bath, and the solution is precipitated as much as possible, and then the amorphous product TaO is obtained by cooling and centrifugation x .

[0083] 3) TaO x High-temperature nitridation

[0084] TaO x The nitride Ta3N5 can be obtained by nitridation at a temperature of 850 DEG C for 10 h under an ammonia gas flow of 200 mL / min.

[0085] The nitride Ta3N5 obtained by the method of the reference examples 2-4 has the same property as the product of example 1.

[0086] In summary, the TaO x with a small size can be prepared by high-temperature hydrolysis of the precursor I. x The amorphous and small-particle-radius TaO

[0087] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been 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 replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a nitride Ta3N5, characterized by: The preparation method comprises the following steps: The precursor I is hydrolyzed at 80-100 °C for 1-2 h to obtain amorphous product TaO x ; TaO x High temperature nitridation yields Ta3N5; The precursor I comprises ATaP2O8 and A3TaP2O9, wherein A is selected from K and Na.

2. The method of claim 1, wherein the method is characterized by: The high-temperature hydrolysis process of the precursor I comprises adding 1-5M AOH solution, wherein A is selected from K and Na.

3. The method of claim 1, wherein the method is characterized by: The ATaP2O8 is prepared by a high-temperature solid phase method with A precursor, Ta precursor, P precursor and AP mixed precursor as raw materials, wherein the molar ratio of A, Ta, P and AP is 1:1:2:(0-10). The A precursor comprises at least one of carbonates, oxalates and nitrates of A. The Ta precursor is Ta2O 5； The P precursor is NH4H2PO4 4； The AP mixed precursor includes H3PO4, AH2PO 4、 at least two of A2HPO4.

4. The method of claim 1, wherein the method is characterized by: The A3TaP2O9 is prepared by a high-temperature solid phase method with A precursor, Ta precursor, P precursor and AP mixed precursor as raw materials, wherein the molar ratio of A, Ta, P and AP is 3:1:2:(0-10). The A precursor comprises at least one of carbonates, oxalates and nitrates of A. The Ta precursor is Ta2O 5； The P precursor is NH4H2PO4 4； The AP mixed precursor includes H3PO4, AH2PO 4、 at least two of A2HPO4.

5. The method of producing nitride Ta3N5 according to any one of claims 3 or 4, characterized by: The processing temperature of the high-temperature solid phase method is 800-900 DEG C, and the processing time is 5-15h.

6. The method of claim 1, wherein the method is characterized by: The high-temperature nitriding is carried out in 200-300 mL / min ammonia gas flow, the temperature is 850-1000 DEG C, and the time is 3-10h. 7.The nitride Ta3N5 prepared by the preparation method in any one of claims 1-6. 8.The nitride Ta3N5 in claim 7 is applied to photocatalytic oxygen production.

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