Nitride Ta3N5 as well as preparation method and application thereof

Abstract

The invention discloses a nitride Ta3N5 and a preparation method and application thereof.The specific method comprises the steps that a precursor I is subjected to pyrohydrolysis, TaOx with the small size is prepared, the nitride Ta3N5 can be prepared after short-time nitridation by means of the characteristics that TaOx is amorphous and small in particle radius, generation of low-valence metal defects is effectively reduced, the charge separation efficiency is improved, and the method is suitable for industrial production. The Ta3N5 shows water decomposition activity in a photocatalytic water decomposition reaction, and the activity of the Ta3N5 is obviously improved compared with that of Ta3N5 prepared by a conventional method.

Description

Technical Field

[0001] The present invention belongs to the technical field of material synthesis and renewable clean energy utilization, and specifically relates to a nitride Ta3N5 and a preparation method and application thereof. Background Art

[0002] (Oxygen) nitrogen compounds have suitable band gaps and conduction band / valence band positions and can be used to decompose water. They are considered to be an attractive class of visible light responsive photocatalysts. However, these (oxygen) nitrogen compound photocatalysts are generally synthesized by high-temperature solid-phase methods. The precursor particles have a large radius and require longer time to be completely nitrided, which inevitably produces more anion vacancies or low-valent metal species. Anion vacancies or low-valent metal species are generally considered to be recombination centers that reduce the photocatalytic activity.

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

[0004] At present, researchers have made many attempts to suppress oxygen-nitrogen compound defects, mainly including:

[0005] (1) Doping with low-valent metals, that is, suppressing the generation of low-valent metal defects by doping with low-valent metal species that are not easily reduced (such as Mg, Sc, Zr, etc.);

[0006] (2) Molten salt-assisted nitridation, that is, molten salt-assisted nitridation changes the synthesis path and improves the activity of the material. For example, Na2CO3 is used to assist in the nitridation of Ta2O5 precursors, first generating Na2Ta2O6, and then potassium ions volatilize to generate Ta3N5;

[0007] (3) Reduce the nitridation time, that is, by nitriding the KTaO3 precursor at high temperature for a short time, high-quality, low-defect Ta3N5 nanorods are obtained at the edge of KTaO3. Unfortunately, short-time nitridation cannot completely convert the precursor oxide into (oxy)nitrogen compounds, and the Ta3N5 nanorods are mainly located on the surface of the material.

[0008] The above three methods all have their merits, but for suppressing low-valent metal defects, the strategy of reducing the nitridation time has the highest priority, because the number of low-valent metal defects can be subsequently controlled by changing the type of precursor or molten salt.

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

[0010] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

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

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

[0013] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0014] The precursor I was hydrolyzed at high temperature to obtain the amorphous product TaO x ;

[0015] TaO x High temperature nitridation can obtain Ta3N5;

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

[0017] As a preferred embodiment of the method for preparing the nitride Ta3N5 of the present invention, the temperature of the high-temperature hydrolysis of the precursor I is 80-100°C and the time is 1-2h.

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

[0019] As a preferred embodiment of the preparation method of the nitride Ta3N5 of the present invention, the ATaP2O8 is prepared by a high temperature solid phase method using 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);

[0020] The A3TaP2O9 is prepared by a high-temperature solid phase method using 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).

[0021] As a preferred embodiment of the method for preparing the nitride Ta3N5 of the present invention, the A precursor comprises at least one of the carbonate, oxalate and nitrate of A;

[0022] The Ta precursor is Ta2O 5；

[0023] The P precursor is NH4H2PO 4；

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

[0025] As a preferred embodiment of the method for preparing the nitride Ta3N5 of the present invention, the processing temperature of the high-temperature solid phase method is 800-900°C and the processing time is 5-15h.

[0026] As a preferred embodiment of the method for preparing the nitride Ta3N5 of the present invention, the high-temperature nitridation is carried out in an ammonia gas flow of 200 to 300 mL / min, at a temperature of 850 to 1000°C, for a time of 3 to 10 hours.

[0027] Another object of the present invention is to provide a method for preparing nitride Ta3N5 and to obtain the nitride Ta3N5.

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

[0029] Beneficial effects of the present invention:

[0030] The present invention can prepare TaO with smaller size by hydrolyzing the precursor I at high temperature. x , using TaO x Due to its amorphous shape and small particle radius, the nitride Ta3N5 can be prepared after a short nitridation time, which effectively reduces the generation of low-valent metal defects and improves the charge separation efficiency. It exhibits water decomposition activity in the photocatalytic water decomposition reaction, and its activity is significantly improved compared with Ta3N5 prepared by conventional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0032] Figure 1 The scanning electron microscope images of Ta3N5 prepared in Example 1 of the present invention and Comparative Examples 1 and 2 are shown.

[0033] Figure 2 The XRD diagrams of Ta3N5 prepared in Example 1 of the present invention and Comparative Examples 1 and 2 are shown.

[0034] Figure 3 The activity diagram of decomposing water and producing oxygen of Ta3N5 prepared in Example 1 of the present invention and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0038] Unless otherwise specified, the raw materials used in the present invention are all commercially available in the art.

[0039] Example 1

[0040] This embodiment provides a method for preparing Ta3N5, specifically:

[0041] 1) Synthesis of Precursor I:

[0042] According to the molar ratio of Na, Ta, P, AP(1) and AP(2) of 3:1:2:2:2, Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 were mixed and ground to make them uniform, and calcined at 900°C for 8h to obtain precursor ⅠNa3TaP2O9.

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

[0044] The precursor I Na3TaP2O9 was heated in a water bath at 80°C for 1 h. After hydrothermal treatment, it was cooled and centrifuged to obtain a powder, which is the amorphous product TaO x The supernatant was directly cooled and centrifuged, and the lower precipitate was repeatedly heated in a water bath to precipitate the solution as much as possible, and then cooled and centrifuged to obtain the amorphous product TaO x .

[0045] 3)TaO x High temperature nitriding:

[0046] TaO x Nitriding is carried out in an ammonia gas flow of 250 mL / min at a nitriding temperature of 900°C and a nitriding time of 5 h to obtain the nitride Ta3N5, which is recorded as Ta3N5-KP.

[0047] Comparative Example 1

[0048] This comparative example provides another method for synthesizing nitride Ta3N5, specifically:

[0049] 1) Synthesis of Precursor I:

[0050] According to the molar ratio of Na, Ta and P of 3:1:2, Na2CO3, Ta2O5 and NH4H2PO4 were mixed and ground to make them uniform, and calcined at 900°C for 8h to obtain precursor ⅠNa3TaP2O9.

[0051] 2) High temperature nitridation of Na3TaP2O9:

[0052] Na3TaP2O9 is nitrided in an ammonia gas flow of 250 mL / min at a nitriding temperature of 950°C and a nitriding time of 15 h to obtain the nitride Ta3N5, which is recorded as Ta3N5-1.

[0053] Comparative Example 2

[0054] This comparative example provides another method for synthesizing nitride Ta3N5, specifically:

[0055] 1) Synthesis of Precursor I:

[0056] According to the molar ratio of Na, Ta, P, AP(1) and AP(2) of 3:1:2:2:2, Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 were mixed and ground to make them uniform, and calcined at 900°C for 8h to obtain precursor ⅠNa3TaP2O9.

[0057] 2) High temperature nitridation of Na3TaP2O9:

[0058] Na3TaP2O9 is nitrided in an ammonia gas flow of 250 mL / min at a nitriding temperature of 950°C and a nitriding time of 15 h to obtain the nitride Ta3N5, which is recorded as Ta3N5-2.

[0059] Figure 1 The scanning electron microscope images of the nitride Ta3N5 prepared in Example 1 and Comparative Examples 1 and 2 are shown in FIG. Figure 2The XRD diagrams of Example 1 and Comparative Examples 1 and 2 prove that the nitride Ta3N5 is successfully synthesized by the Example and Comparative Example schemes.

[0060] Application Testing

[0061] The nitride Ta3N5 synthesized in the embodiment or comparative example is used for photocatalytic oxygen production reaction. Specifically, the reaction conditions include:

[0062] 500mg loaded with 2wt% CoO x Ta3N5 sample, 500mgLa2O3, 1.6988gAgNO3200mL H2O, 300W xenon lamp light source;

[0063] The results are as follows Figure 3 As shown, it can be seen that the nitride Ta3N5 prepared by the present invention can realize the photocatalytic oxygen production half reaction after loading the corresponding oxygen production co-catalyst. As the reaction time increases, the oxygen production rate decreases. This is because the sacrificial agent AgNO3 is reduced to Ag elemental substance and deposited on Ta3N5, resulting in obstructed light absorption and decreased reaction activity. This is a common phenomenon. This experiment proves that the generated Ta3N5 has photocatalytic oxygen production performance, and the photocatalytic oxygen production performance of the nitride prepared in Comparative Examples 1 and 2 is significantly improved.

[0064] Example 2

[0065] 1) Synthesis of Precursor I:

[0066] According to the molar ratio of Na, Ta, P, AP(1) and AP(2) of 3:1:2:2:2, Na2CO3, Ta2O5, NH4H2PO4, NaH2PO4 and Na2HPO4 were mixed and ground to make them uniform, and calcined at 850°C for 12h to obtain precursor ⅠNa3TaP2O9.

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

[0068] The precursor I Na3TaP2O9 was heated in a water bath at 100°C for 1 h. After hydrothermal treatment, it was cooled and centrifuged to obtain a powder, which is the amorphous product TaO x The supernatant was directly cooled and centrifuged, and the lower precipitate was repeatedly heated in a water bath to precipitate the solution as much as possible, and then cooled and centrifuged to obtain the amorphous product TaO x .

[0069] 3)TaO x High temperature nitriding:

[0070] TaO xThe nitride Ta3N5 can be obtained by nitriding in an ammonia gas flow of 200 mL / min at a nitriding temperature of 1000°C and a nitriding time of 3 h.

[0071] Example 3

[0072] 1) Synthesis of Precursor I:

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

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

[0075] The precursor I Na3TaP2O9 was heated in a water bath at 90°C for 2 h. After hydrothermal treatment, it was cooled and centrifuged to obtain a powder, which is the amorphous product TaO x The supernatant was directly cooled and centrifuged, and the lower precipitate was repeatedly heated in a water bath to precipitate the solution 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 can be obtained by nitriding in an ammonia gas flow of 300 mL / min at a nitriding temperature of 850°C and a nitriding time of 9 h.

[0078] Example 4

[0079] 1) Synthesis of Precursor I:

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

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

[0082] The precursor I Na3TaP2O9 was heated in a water bath at 80°C for 2 h. After hydrothermal treatment, it was cooled and centrifuged to obtain a powder, which is the amorphous product TaO xThe supernatant was directly cooled and centrifuged, and the lower precipitate was repeatedly heated in a water bath to precipitate the solution as much as possible, and then cooled and centrifuged to obtain the amorphous product TaO x .

[0083] 3)TaO x High temperature nitriding:

[0084] TaO x The nitride Ta3N5 can be obtained by nitriding in an ammonia gas flow of 200 mL / min at a nitriding temperature of 850°C and a nitriding time of 10 h.

[0085] The properties of the nitride Ta3N5 obtained by the methods of Examples 2 to 4 are equivalent to those of the product of Example 1.

[0086] In summary, the present invention can prepare TaO with smaller size by hydrolyzing the precursor I at high temperature. x , using TaO x Due to its amorphous shape and small particle radius, the nitride Ta3N5 can be prepared after a short nitridation time, which effectively reduces the generation of low-valent metal defects and improves the charge separation efficiency. It exhibits water decomposition activity in the photocatalytic water decomposition reaction, and its activity is significantly improved compared with Ta3N5 prepared by conventional methods.

[0087] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention 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 invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing nitride Ta3N5, characterized in that: include, The precursor I was hydrolyzed at high temperature to obtain the amorphous product TaO x ; TaO x High temperature nitridation can obtain Ta3N5; Wherein, the precursor I includes ATaP2O8, A3TaP2O9, and A is selected from any one of K and Na.

2. The method for preparing the nitride Ta3N5 according to claim 1, characterized in that: The temperature of the high temperature hydrolysis of the precursor I is 80-100° C. and the time is 1-2 hours.

3. The method for preparing the nitride Ta3N5 according to claim 2, characterized in that: The high temperature hydrolysis process of the precursor I includes adding 1-5M AOH solution, wherein A is selected from any one of K and Na.

4. The method for preparing the nitride Ta3N5 according to claim 1, characterized in that: The ATaP2O8 is prepared by a high-temperature solid phase method using 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).

5. The method for preparing the nitride Ta3N5 according to claim 1, characterized in that: The A3TaP2O9 is prepared by a high-temperature solid phase method using 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).

6. The method for preparing the nitride Ta3N5 according to any one of claims 4 or 5, characterized in that: The A precursor includes at least one of carbonate, oxalate and nitrate of A; The Ta precursor is Ta2O 5； The P precursor is NH4H2PO 4； The AP mixed precursor includes H3PO4, AH2PO 4、 At least two of A2HPO4.

7. The method for preparing the nitride Ta3N5 according to claim 4, characterized in that: The processing temperature of the high temperature solid phase method is 800-900° C., and the processing time is 5-15 hours.

8. The method for preparing the nitride Ta3N5 according to claim 1, characterized in that: The high-temperature nitriding is carried out in an ammonia gas flow of 200 to 300 mL / min, at a temperature of 850 to 1000° C., for a time of 3 to 10 hours.

9. The nitride Ta3N5 obtained by the preparation method as described in any one of claims 1 to 8.

10. Use of the nitride Ta3N5 as claimed in claim 8 in photocatalytic oxygen production.

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