A red titanium dioxide heterostructure, its preparation method, and its application

Abstract

This disclosure presents a red titanium dioxide heterojunction, its preparation method, and its applications, belonging to the field of materials synthesis and renewable clean energy utilization technology. The preparation method of the red titanium dioxide heterojunction includes: forming a first precursor of boron-doped titanium dioxide; calcining the first precursor at high temperature to obtain a second precursor of the boron-doped titanium dioxide heterojunction; mixing any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 with the second precursor and then nitriding it in an ammonia stream to obtain a red titanium dioxide heterojunction uniformly doped with rutile and anatase phases. This disclosure utilizes ammonium fluorotitanate treatment to nitrid rutile titanium dioxide, forming a red titanium dioxide heterojunction uniformly doped with both rutile and anatase phases, exhibiting high water oxidation activity in photocatalytic water splitting reactions.

Description

Technical Field

[0001] This disclosure belongs to the field of materials synthesis and renewable clean energy utilization technology, specifically relating to a red titanium dioxide heterostructure, its preparation method, and its application. Background Technology

[0002] Titanium dioxide is a key material in the field of photocatalysts, but its absorption spectrum is mainly in the ultraviolet region, limiting its applications. Methods to extend the absorption spectrum of semiconductor photocatalysts include doping with cations and anions, forming solid solutions, and surface disordering. Extensive research has been conducted on the modification of titanium dioxide; for example, in 2001, R. Asahi discovered that anion-doped TiO₂... 2-x N x It can significantly improve the visible light absorption of titanium dioxide, opening the prelude to visible light response modification of catalysts. However, nitrogen-doped titanium dioxide systems have two prominent problems: (1) nitrogen atom doping is generally concentrated on the surface, making it impossible to achieve uniform doping in the bulk phase; (2) the valence states of nitrogen atoms and oxygen atoms are different, and doping will lead to charge imbalance in the material, increasing the number of photogenerated charge recombination centers. Secondly, in 2022, Professor Chen Xiaobo reported that by treating the surface with hydrogen, the surface of titanium dioxide can be disordered, and its absorption spectrum can reach 1000 nm. However, this method is not conducive to chemical reactions that require specific surface adsorption sites to initiate the photocatalytic process, that is, it is not conducive to the smooth progress of such reactions.

[0003] However, heterojunctions can effectively promote charge separation. Titanium dioxide has two phases: rutile and anatase. Pure rutile or anatase titanium dioxide exhibits low activity during photocatalytic reforming, but titanium dioxide with both phases present shows significantly improved activity during photocatalytic methanol reforming. This demonstrates that heterojunctions can effectively promote charge separation. However, the primary phase of red titanium dioxide is the anatase phase, making it impossible to synthesize rutile-phase red titanium dioxide.

[0004] To address this, a simple calcination method is used to synthesize boron-doped rutile and anatase phases. However, calcination alone results in the loss of a large amount of boron. The doping process generally occurs mainly on the outer surface of the material, making it impossible to achieve uniform doping of both phases. This leads to a shoulder-shaped absorption spectrum, which limits the absorption of visible light and thus affects the utilization rate of solar energy. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a red titanium dioxide heterostructure, its preparation method, and its application.

[0006] One aspect of this disclosure provides a method for preparing a red titanium dioxide heterostructure, the method comprising:

[0007] The first precursor of boron-doped titanium dioxide is formed;

[0008] The first precursor was calcined at high temperature to obtain a second precursor of B-doped titanium dioxide heterostructure.

[0009] Any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 is mixed with the second precursor and then nitrided in an ammonia gas stream to obtain a red titanium dioxide heterostructure uniformly doped with rutile and anatase phases.

[0010] Optionally, the first precursor for forming B-doped titanium dioxide includes:

[0011] TiB2 was hydrothermally treated in an H2SO4 solution system to obtain the first precursor.

[0012] Optionally, the H2SO4 solution system may be a mixture of HCl and Na2SO4.

[0013] Optionally, the concentration of HCl is 0.5-1.5M, and the concentration of Na2SO4 is 0.05-0.2M.

[0014] Optionally, the hydrothermal treatment temperature is 180–200℃ and the time is 6–24 hours.

[0015] Optionally, the high-temperature calcination temperature is 600–750°C, and the time is 1–2 hours.

[0016] Optionally, the molar ratio of ammonium fluorotitanate to the second precursor is (0-0.5):1.

[0017] Optionally, the nitriding treatment is performed at a temperature of 500–600°C for 1–2 hours.

[0018] During the nitriding process, the ammonia gas flow rate is 50–100 mL / min.

[0019] In another aspect of this disclosure, a red titanium dioxide heterostructure is proposed, prepared according to the preparation method described above.

[0020] In another aspect of this disclosure, an application of a red titanium dioxide heterostructure is proposed, which employs the red titanium dioxide heterostructure described above for the decomposition of water.

[0021] This disclosure proposes a red titanium dioxide heterojunction, its preparation method, and its application. The preparation method includes: forming a first precursor of boron-doped titanium dioxide; calcining the first precursor at high temperature to obtain a second precursor of the boron-doped titanium dioxide heterojunction; mixing any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 with the second precursor and then nitriding it in an ammonia stream to obtain the red titanium dioxide heterojunction. This disclosure utilizes ammonium fluorotitanate treatment to nitrid rutile-phase titanium dioxide, forming a red titanium dioxide heterojunction uniformly doped with both rutile and anatase phases, which exhibits water oxidation activity in photocatalytic water splitting reactions. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating a method for preparing a red titanium dioxide heterostructure according to an embodiment of the present disclosure.

[0023] Figure 2 The XRD patterns are of the titanium dioxide heterostructures in Example 1 and Comparative Example 1 of this disclosure.

[0024] Figure 3 The UV-vis images are of the titanium dioxide heterostructures in Example 1 and Comparative Example 1 of this disclosure;

[0025] Figure 4 The diagram shows the activity of titanium dioxide heterostructure in water decomposition to produce hydrogen in Example 1 and Comparative Example 1 of this disclosure. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0027] like Figure 1 As shown, one aspect of this disclosure provides a method S100 for preparing a red titanium dioxide heterostructure, specifically including the following steps S110 to S130:

[0028] S110 forms the first precursor of boron-doped titanium dioxide.

[0029] Specifically, the first precursor is prepared by a hydrothermal method, that is, TiB2 is used as raw material and hydrothermally treated in an H2SO4 solution system to obtain the first precursor.

[0030] It should be noted that in hydrothermal treatment, as long as the H2SO4 solution system is maintained, sulfate ions help control the crystal form. For example, the H2SO4 solution system can be a mixture of HCl and Na2SO4, wherein the concentration of HCl is preferably 0.5-1.5M, such as 0.5M, 0.7M, 1.0M, 1.2M, 1.5M, etc., and the concentration of Na2SO4 is preferably 0.05-0.2M, such as 0.05M, 0.1M, 0.12M, 0.15M, etc. Of course, H2SO4 solution systems formed by other components can also be used, and there are no specific limitations on this.

[0031] As a further preferred option, the concentration ratio of HCl to Na2SO4 is preferably 10:1. For example, the concentration of HCl is preferably 1M and the concentration of Na2SO4 is preferably 0.1M. Of course, other concentration ratios can be selected in other preferred options, and there is no specific limitation on them.

[0032] In some other preferred embodiments, the hydrothermal treatment temperature is 180–200°C, for example, 180°C, 190°C, 200°C, etc., and the hydrothermal treatment time is 6–24 hours, for example, 6 hours, 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, etc.

[0033] S120. The first precursor is calcined at high temperature to obtain a second precursor of B-doped titanium dioxide heterostructure.

[0034] Specifically, the first precursor is cooled and centrifuged, and then calcined in a muffle furnace to obtain a B-doped titanium dioxide heterostructure, which is denoted as the second precursor.

[0035] In some preferred embodiments, the calcination temperature is 600–750°C, for example, 600°C, 650°C, 700°C, 750°C, etc., and the calcination time is 1–2 hours, for example, 1 hour, 1.5 hours, 2 hours, etc.

[0036] S130. Any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 is mixed with the second precursor and then nitrided in an ammonia gas stream to obtain a red titanium dioxide heterostructure uniformly doped with rutile and anatase phases.

[0037] In some preferred embodiments, the molar ratio of any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 to the second precursor is (0 to 0.5):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, etc.

[0038] In some other preferred embodiments, the nitriding treatment temperature is 500–600°C, for example, 500°C, 550°C, 600°C, etc., and the time is 1–2 hours, for example, 1 hour, 1.5 hours, 2 hours, etc.

[0039] In some other preferred embodiments, the ammonia gas flow rate during the nitriding process is 50–100 mL / min, for example, 50 mL / min, 70 mL / min, 100 mL / min, etc.

[0040] In this embodiment, a second precursor with heterogeneous phase junctions can be prepared by calcining the first precursor. The second precursor is then mixed with one of (NH4)2TiF6, NH4TiOF3, or (NH4)2TiOF4 and nitrided to nitrid the rutile phase titanium dioxide. This results in the uniform doping of the rutile and anatase phases into the interior and surface of the titanium dioxide, yielding a red titanium dioxide heterogeneous phase junction. This preparation method is simple, and the product has a broad absorption spectrum.

[0041] Another aspect of this disclosure is the preparation of a red titanium dioxide heterostructure, which is prepared using the method described above. For the specific preparation process, please refer to the previous description, which will not be repeated here.

[0042] It should be understood that the red titanium dioxide heterostructure provided in this embodiment refers to a mixed crystal form of rutile and anatase phases, that is, including both rutile and anatase phases. In other words, these two phases are uniformly doped into the interior and surface of the material. Compared with doping only on the outer surface, this mixed crystal form of titanium dioxide has higher photocatalytic activity.

[0043] Another aspect of this disclosure proposes an application of a red titanium dioxide heterostructure, which, when applied to water splitting, exhibits high water oxidation activity in the photocatalytic water splitting reaction, effectively increasing hydrogen production.

[0044] The preparation method and application of red titanium dioxide heterojunction will be further illustrated below with specific examples:

[0045] Example 1

[0046] This example presents a method for preparing red titanium dioxide heterostructures, which mainly includes the following steps:

[0047] Step 1: Preparation of the first precursor (B-doped titanium dioxide)

[0048] Take 0.1g TiB2 and put it into a mixed solution of 60mL 1M HCl and 0.1M Na2SO4. Stir for half an hour and then put it into a hydrothermal reactor for hydrothermal reaction at 180℃ for 6 hours.

[0049] Step 2: Preparation of the second precursor (B-doped titanium dioxide heterojunction)

[0050] The first precursor (B-doped titanium dioxide) was cooled and centrifuged, then calcined in air at 700°C for 1 hour.

[0051] Step 3: Preparation of red titanium dioxide heterostructure

[0052] The molar ratio of ammonium fluorotitanate (NH4)2TiF6 to the second precursor was 0.3:1. Nitriding was carried out in an ammonia gas flow of 100 mL / min, at a nitriding temperature of 550 °C, and for 1 h.

[0053] like Figure 2 As shown, according to the XRD results, the red titanium dioxide heterostructure obtained in Example 1 includes two phases: rutile and anatase.

[0054] like Figure 3 As shown, according to the UV-vis results, the maximum absorption peak of Example 1 is at 400 nm, and the absorption band edge can be extended to 600 nm, exhibiting the characteristics of band-to-band transition absorption.

[0055] Furthermore, the titanium dioxide heterostructure prepared in Example 1 was used as a photocatalyst to evaluate the photocatalytic water splitting activity. The reaction conditions were as follows:

[0056] 50 mg of titanium dioxide heterojunction sample, 100 mL of H2O, 5 mM Fe(NO3)3, 300 W xenon lamp light source.

[0057] like Figure 4 As shown in the diagram, the titanium dioxide heterojunction photocatalyst in Example 1 exhibits high oxygen production activity in the photocatalytic splitting of water under a light source.

[0058] Comparative Example 1

[0059] This example presents a method for preparing red titanium dioxide heterostructures, which mainly includes the following steps:

[0060] Step 1: Preparation of the first precursor (B-doped titanium dioxide)

[0061] Take 0.1g TiB2 and put it into a mixed solution of 60mL 1M HCl and 0.1M Na2SO4. Stir for half an hour and then put it into a hydrothermal reactor for hydrothermal reaction at 180℃ for 6 hours.

[0062] Step 2: Preparation of the second precursor (B-doped titanium dioxide heterojunction)

[0063] The first precursor (B-doped titanium dioxide) was cooled and centrifuged, then calcined in air at 700°C for 1 hour.

[0064] Step 3: Preparation of red titanium dioxide heterostructure

[0065] Nitriding was carried out in an ammonia gas flow of 100 mL / min at a nitriding temperature of 550 °C for 1 h.

[0066] like Figure 2 As shown, according to the XRD results, the red titanium dioxide heterostructure obtained in Comparative Example 1 includes two phases: rutile and anatase.

[0067] like Figure 3 As shown, according to the UV-vis results, the maximum absorption peak of Comparative Example 1 is at 350 nm, and the absorption band edge is at 550 nm, exhibiting the characteristics of shoulder absorption.

[0068] Furthermore, the titanium dioxide heterostructure prepared in Comparative Example 1 was used as a photocatalyst to evaluate the photocatalytic water splitting activity. The reaction conditions were as follows:

[0069] 50 mg of titanium dioxide heterojunction sample, 100 mL of H2O, 5 mM Fe(NO3)3, 300 W xenon lamp light source.

[0070] like Figure 4 As shown in the diagram, the titanium dioxide heterojunction photocatalyst in Comparative Example 1 exhibits low oxygen production activity during the photocatalytic splitting of water under a light source.

[0071] In summary, Example 1 successfully prepared a red titanium dioxide heterojunction with uniform nitrogen doping, a full absorption spectrum, and high oxygen production activity. In contrast, Comparative Example 1 was dark red with a brownish tinge, indicating that the nitrogen doping was uneven and the absorption spectrum was not full without the addition of ammonium fluorotitanate, which affected the light absorption efficiency in the photocatalyst reaction and resulted in oxygen production activity that was significantly lower than that of Example 1.

[0072] This disclosure proposes a red titanium dioxide heterostructure, its preparation method, and its application. Compared with the prior art, it has the following beneficial effects: This disclosure forms B-doped titanium dioxide by hydrothermal method, which is used as a precursor. The precursor II containing the heterostructure is further prepared by calcination. Furthermore, the precursor II is mixed with ammonium fluorotitanate and nitrided to prepare the red titanium dioxide heterostructure. This method can form titanium dioxide heterostructures with uniform doping of rutile and anatase phases, and the product exhibits high water splitting activity in photocatalytic water splitting reaction.

[0073] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing a red titanium dioxide heterostructure, characterized in that, The preparation method includes: The first precursor of boron-doped titanium dioxide is formed; The first precursor is calcined at high temperature to obtain a second precursor of B-doped titanium dioxide heterostructure; the high temperature calcination temperature is 600~750℃. Any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 is mixed with the second precursor and then nitrided in an ammonia gas stream to obtain a red titanium dioxide heterojunction uniformly doped with rutile and anatase phases. The nitriding temperature is 500~600℃.

2. The preparation method according to claim 1, characterized in that, The first precursor for forming B-doped titanium dioxide includes: TiB2 was hydrothermally treated in an H2SO4 solution system to obtain the first precursor.

3. The preparation method according to claim 2, characterized in that, The H2SO4 solution system is a mixture of HCl and Na2SO4.

4. The preparation method according to claim 3, characterized in that, The concentration of HCl is 0.5-1.5M, and the concentration of Na2SO4 is 0.05-0.2M.

5. The preparation method according to claim 2, characterized in that, The hydrothermal treatment temperature is 180~200℃, and the time is 6~24h.

6. The preparation method according to claim 1, characterized in that, The high-temperature calcination time is 1~2 hours.

7. The preparation method according to claim 1, characterized in that, The molar ratio of any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 to the second precursor is (0~0.5):

1.

8. The preparation method according to claim 1, characterized in that, The nitriding treatment time is 1-2 hours, and the ammonia gas flow rate is 50-100 mL / min.

9. A red titanium dioxide heterostructure, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

10. An application of a red titanium dioxide heterostructure, characterized in that, The red titanium dioxide heterostructure described in claim 9 is applied to the decomposition of water.

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