Red titanium dioxide heterojunction, and preparation method therefor and use thereof

Abstract

The present disclosure belongs to the technical field of material synthesis and utilization of renewable clean energy, and provides a red titanium dioxide heterojunction, and a preparation method therefor and the use thereof. The preparation method for a red titanium dioxide heterojunction comprises: forming a first precursor of B-doped titanium dioxide; calcining the first precursor at a high temperature to obtain a second precursor of a B-doped titanium dioxide heterojunction; and mixing any one of (NH4)2TiF6, NH4TiOF3 and (NH4)2TiOF4 with the second precursor, followed by a nitridation treatment in an ammonia gas flow to obtain a red titanium dioxide heterojunction uniformly doped with a rutile phase and an anatase phase. In the present disclosure, titanium dioxide in a rutile phase can be nitrided by means of an ammonium fluotitanate treatment, such that a red titanium dioxide heterojunction uniformly doped with both a rutile phase and an anatase phase is formed, which heterojunction exhibits relatively high water oxidation activity in a photocatalytic water decomposition reaction.

Description

A red titanium dioxide hetero junction and a preparation method and application thereof

[0001] Cross-reference to Related Applications

[0002] This application claims priority to Chinese Patent Application No. 202411355396.1, filed on September 27, 2024, and entitled "A red titanium dioxide hetero junction and a preparation method and application thereof", the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure belongs to the technical field of material synthesis and renewable clean energy utilization, and specifically relates to a red titanium dioxide hetero junction and a preparation method and application thereof. BACKGROUND

[0004] Titanium dioxide is the main material in the field of photocatalysts, but its absorption spectrum is mainly in the ultraviolet region, which limits its application. The means of expanding the absorption spectrum of semiconductor photocatalytic materials include doping cations, doping anions, forming solid solutions, and surface disordering. There have been a large number of research works around the modification of titanium dioxide. For example, in 2001, R. Asahi found that the anion N-doped TiO 2-x N x can significantly improve the visible light absorption of titanium dioxide, opening up the curtain of visible light response modification of catalysts. However, there are two outstanding problems in the nitrogen-doped titanium dioxide system: (1) nitrogen atoms are generally concentrated on the surface, and uniform bulk doping cannot be achieved; (2) there is a difference in valence state between nitrogen atoms and oxygen atoms, and doping will cause charge imbalance of the material and increase the photo-generated charge recombination center. Secondly, in 2022, Professor Chen Xiaobo reported that by surface hydrogen reduction treatment, the surface of titanium dioxide was disordered, and its absorption spectrum could reach 1000 nm. However, this method is not conducive to the smooth progress of chemical reactions that need to have a clear surface adsorption point to start the photocatalytic process, i.e., it is not conducive to the smooth progress of such reactions.

[0005] However, a hetero junction can effectively promote charge separation. Titanium dioxide has two phases of rutile and anatase, and pure rutile or anatase phase titanium dioxide has low activity in photocatalytic reforming, but the activity of titanium dioxide with two phases coexisting in photocatalytic methanol reforming is significantly improved, which can prove that "hetero junction" can effectively promote charge separation. However, the phase of red titanium dioxide is mainly anatase, and rutile phase red titanium dioxide cannot be synthesized.

[0006] In view of this, currently, boron-doped rutile and anatase two-phase are synthesized by simple calcination, but a large amount of boron element is lost by only calcination, the doping process mainly occurs on the outer surface of the material, and uniform doping of the two phases cannot be achieved, resulting in shoulder-shaped absorption of the absorption spectrum, limiting the absorption of visible light, and thus affecting the utilization rate of solar energy. SUMMARY

[0007] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provide a red titanium dioxide hetero-phase junction and a preparation method and application thereof.

[0008] In one aspect of the present disclosure, a preparation method of a red titanium dioxide hetero-phase junction is provided, and the preparation method comprises:

[0009] forming a first precursor of B-doped titanium dioxide;

[0010] high-temperature calcining the first precursor to obtain a second precursor of a B-doped titanium dioxide hetero-phase junction;

[0011] mixing any one of (NH4)2TiF6 (also referred to as ammonium fluorotitanate in the present application), NH4TiOF3, and (NH4)2TiOF4 with the second precursor and then performing nitrogenization treatment in an ammonia gas stream to obtain a red titanium dioxide hetero-phase junction uniformly doped with rutile and anatase phases.

[0012] Optionally, the forming of the first precursor of B-doped titanium dioxide comprises:

[0013] hydrothermally treating TiB2 in an H2SO4 solution system to obtain the first precursor.

[0014] Optionally, the H2SO4 solution system adopts an HCl and Na2SO4 mixed solution system 。

[0015] Optionally, the concentration of the HCl is 0.5-1.5 M, and the concentration of the Na2SO4 is 0.05-0.2 M.

[0016] Optionally, the temperature of the hydrothermal treatment is 180-200℃, and the time is 6-24 h.

[0017] Optionally, the temperature of the high-temperature calcination is 600-750℃, and the time is 1-2 h.

[0018] Optionally, the molar ratio of the ammonium fluorotitanate to the second precursor is (0-0.5):1.

[0019] Optionally, the temperature of the nitrogenization treatment is 500-600℃, and the time is 1-2 h. In the nitrogenization treatment, the ammonia gas stream flow rate is 50-100 mL / min.

[0020] Another aspect of the present disclosure provides a red titania heterojunction, which is prepared according to the preparation method described above.

[0021] Another aspect of the present disclosure provides an application of the red titania heterojunction, which is used for decomposing water.

[0022] The present disclosure provides a red titania heterojunction, a preparation method and an application thereof. The preparation method of the red titania heterojunction comprises the following steps: forming a first precursor of B-doped titania; calcining the first precursor at a high temperature to obtain a second precursor of the B-doped titania heterojunction; mixing any one of (NH4)2TiF6, NH4TiOF3 and (NH4)2TiOF4 with the second precursor, and then performing a nitriding treatment in an ammonia gas flow to obtain the red titania heterojunction. According to the present disclosure, the rutile titania can be nitrided by using ammonium fluorotitanate, so that the red titania heterojunction with uniform doping of rutile and anatase phases is formed, and the water oxidation activity is exhibited in the photocatalytic water decomposition reaction. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 is a flow chart of a preparation method of the red titania heterojunction according to an embodiment of the present disclosure;

[0024] Fig. 2 is an XRD pattern of the titania heterojunction according to Example 1 and Comparative Example 1 of the present disclosure;

[0025] Fig. 3 is a UV-vis pattern of the titania heterojunction according to Example 1 and Comparative Example 1 of the present disclosure;

[0026] Fig. 4 is a hydrogen production activity pattern of the titania heterojunction according to Example 1 and Comparative Example 1 of the present disclosure. DETAILED DESCRIPTION

[0027] In order to make the skilled in the art better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are part of the embodiments of the present disclosure, but not all the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by the skilled in the art without creative labor are within the scope of protection of the present disclosure.

[0028] As shown in Fig. 1, in one aspect of the present disclosure, a preparation method S100 of a red titania heterojunction is provided, which specifically comprises the following steps S110-S130:

[0029] S110, forming a first precursor of B-doped titania.

[0030] Specifically, the first precursor is prepared by a hydrothermal method, i.e., TiB2 is used as a raw material, and a hydrothermal treatment is performed in an H2SO4 solution system to obtain the first precursor.

[0031] It should be noted that in the hydrothermal treatment, only the H2SO4 solution system needs to be ensured, and sulfate is helpful to control the crystal form. For example, the H2SO4 solution system is a solution system formed by mixing HCl and Na2SO4, wherein the concentration of HCl can be selected as 0.5-1.5M, for example, 0.5M, 0.7M, 1.0M, 1.2M, 1.5M, etc., and the concentration of Na2SO4 can be selected as 0.05-0.2M, for example, 0.05M, 0.1M, 0.12M, 0.15M, etc. Of course, other components can also be used to form the H2SO4 solution system, which is not limited in particular.

[0032] As a further optional solution, the ratio of the concentration of HCl to the concentration of 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, in other optional solutions, other concentration ratios can also be selected, which is not limited in particular.

[0033] In other optional embodiments, the temperature of the hydrothermal treatment is 180-200℃, for example, 180℃, 190℃, 200℃, etc., and the time of the hydrothermal treatment is 6-24h, for example, 6h, 8h, 10h, 15h, 20h, 24h, etc.

[0034] S120, the first precursor is high-temperature calcined to obtain a second precursor of a B-doped titanium dioxide hetero-junction.

[0035] Specifically, the first precursor is cooled and centrifuged, and then is placed in a muffle furnace for calcination treatment to obtain a B-doped titanium dioxide hetero-junction, which is denoted as a second precursor.

[0036] In some optional embodiments, the temperature of the calcination treatment is 600-750℃, for example, 600℃, 650℃, 700℃, 750℃, etc., and the calcination time is 1-2h, for example, 1h, 1.5h, 2h, etc.

[0037] S130, any one of (NH4)2TiF6, NH4TiOF3, and (NH4)2TiOF4 is mixed with the second precursor, and then is subjected to a nitriding treatment in an ammonia gas stream to obtain a rutile phase and an anatase phase uniformly doped red titanium dioxide hetero-junction.

[0038] In some optional embodiments, the molar ratio of any one of (NH4)2TiF6, NH4TiOF3, (NH4)2TiOF4 to the second precursor is (0-0.5):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, etc.

[0039] In some other optional embodiments, the temperature of the nitriding treatment is 500-600℃, for example, 500℃, 550℃, 600℃, etc., and the time is 1-2h, for example, 1h, 1.5h, 2h, etc.

[0040] In some other optional embodiments, in the nitriding treatment, the ammonia gas flow rate is 50-100mL / min, for example, 50mL / min, 70mL / min, 100mL / min, etc.

[0041] In the present embodiment, the second precursor with heterogeneous phase junction can be prepared by calcining the first precursor, and the rutile phase titanium dioxide is nitrided by mixing one of (NH4)2TiF6, NH4TiOF3, (NH4)2TiOF4 and then nitriding treatment, so that the rutile and anatase phases are uniformly doped in the interior and surface of the titanium dioxide, and the red titanium dioxide heterogeneous phase junction is obtained. The preparation method is simple, and the absorption spectrum of the product is wide.

[0042] In another aspect of the present disclosure, a red titanium dioxide heterogeneous phase junction is provided, which is prepared by the preparation method given above, and the specific preparation process is described above and will not be repeated here.

[0043] It should be understood that the red titanium dioxide heterogeneous phase junction provided in the present embodiment refers to a mixed crystal form of rutile phase and anatase phase, that is, it includes both rutile and anatase phases, that is, the two phases are uniformly doped in the interior and surface of the material. Compared with doping only on the outer surface, the mixed crystal form of titanium dioxide has higher photocatalytic activity.

[0044] In another aspect of the present disclosure, an application of the red titanium dioxide heterogeneous phase junction is provided. The red titanium dioxide heterogeneous phase junction described above is applied to decompose water, and shows higher water oxidation activity in the photocatalytic water decomposition reaction, effectively improving the hydrogen production.

[0045] The preparation method and application of the red titanium dioxide heterogeneous phase junction will be further described below with reference to specific embodiments:

[0046] Example 1

[0047] The present example provides a preparation method of a red titanium dioxide heterogeneous phase junction, which mainly includes the following steps:

[0048] Step one, preparing a first precursor (B-doped titanium dioxide)

[0049] Take 0.1 g TiB2 into 60 mL of a mixed solution of 1M HCl and 0.1M Na2SO4, stir for half an hour, and put it into a hydrothermal reactor for hydrothermal reaction, with a reaction temperature of 180°C and a hydrothermal time of 6h.

[0050] Step two, preparation of the second precursor (B-doped titanium dioxide hetero-phase junction)

[0051] Cool and centrifuge the first precursor (B-doped titanium dioxide), and calcine it in air at 700°C for 1h.

[0052] Step three, preparation of red titanium dioxide hetero-phase junction

[0053] The molar ratio of ammonium fluorotitanate (NH4)2TiF6 to the second precursor is 0.3:1, and the nitridation is carried out in an ammonia gas flow of 100mL / min, with a nitridation temperature of 550°C and a nitridation time of 1h.

[0054] As shown in FIG. 2, according to the XRD results, the red titanium dioxide hetero-phase junction obtained in Example 1 includes two phases of rutile and anatase.

[0055] As shown in FIG. 3, according to the UV-vis results, the maximum absorption peak of Example 1 is at 400nm, and the absorption band edge can be extended to 600nm, showing the characteristics of band-to-band transition absorption.

[0056] Further, the titanium dioxide hetero-phase junction prepared in Example 1 is used as a photocatalyst for activity evaluation experiments of photocatalytic water decomposition, and the reaction conditions are as follows:

[0057] 50mg of titanium dioxide hetero-phase junction sample, 100mL of H2O, 5mM of Fe(NO3)3, and a 300W xenon lamp light source.

[0058] As shown in FIG. 4, according to the hydrogen production activity diagram for water decomposition, the titanium dioxide hetero-phase junction photocatalyst of Example 1 shows high oxygen production activity under light catalysis for water decomposition.

[0059] Comparative Example 1

[0060] The present example proposes a method for preparing a red titanium dioxide hetero-phase junction, which mainly includes the following steps:

[0061] Step one, preparation of the first precursor (B-doped titanium dioxide)

[0062] Take 0.1 g TiB2 into 60 mL of a mixed solution of 1M HCl and 0.1M Na2SO4, stir for half an hour, and put it into a hydrothermal reactor for hydrothermal reaction, with a reaction temperature of 180°C and a hydrothermal time of 6h.

[0063] Step two, preparation of the second precursor (B-doped titanium dioxide heterojunction)

[0064] The first precursor (B-doped titanium dioxide) was cooled and centrifuged, calcined at 700℃ in air for 1h.

[0065] Step three, preparation of red titanium dioxide heterojunction

[0066] Nitridation was carried out at 550℃ for 1h under an ammonia gas flow of 100mL / min.

[0067] As shown in Figure 2, according to the XRD results, the red titanium dioxide heterojunction obtained in the present comparative example 1 includes both rutile and anatase phases.

[0068] As shown in Figure 3, according to the UV-vis results, the maximum absorption peak of the present comparative example 1 is at 350nm, and the absorption band edge is at 550nm, showing the characteristics of shoulder-shaped absorption.

[0069] Further, the titanium dioxide heterojunction prepared in the present comparative example 1 was used as a photocatalyst to evaluate the activity of photocatalytic water decomposition, and the reaction conditions were as follows:

[0070] 50mg of titanium dioxide heterojunction sample, 100mL of H2O, 5mM of Fe(NO3)3, and a 300W xenon lamp light source.

[0071] As shown in Figure 4, according to the hydrogen production activity diagram of water decomposition, the titanium dioxide heterojunction photocatalyst of the present comparative example 1 photocatalytically decomposes water under light source, and has low oxygen production activity.

[0072] In summary, the present example 1 realizes the preparation of red titanium dioxide heterojunction, and the nitrogen doping is uniform, the absorption spectrum is full, and the oxygen production activity is high. The color of the present comparative example 1 is dark red to brown, indicating that the nitrogen doping is not uniform without the addition of ammonium fluorotitanate, the absorption spectrum is not full, which affects the light absorption efficiency in the photocatalyst reaction, and the oxygen production activity is significantly lower than that of the present example 1.

[0073] The present disclosure proposes a red titanium dioxide heterojunction and a preparation method and application thereof, which has the following beneficial effects compared with the prior art: the present disclosure forms B-doped titanium dioxide by hydrothermal method, which is used as a precursor, and further prepares a precursor II with heterojunction by calcination, and then mixes it with ammonium fluorotitanate and nitrifies to prepare a red titanium dioxide heterojunction. This method can form a titanium dioxide heterojunction with uniform doping of rutile and anatase phases, and the product shows high water decomposition activity in the photocatalytic water decomposition reaction.

[0074] It is understood that the above embodiments are only exemplary for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A method for the preparation of red titanium dioxide hetero-phase junctions, characterized in that, The preparation method comprises: forming a first precursor of B-doped titanium dioxide; high-temperature calcining the first precursor to obtain a second precursor of B-doped titanium dioxide hetero-junction; mixing any one of (NH4)2TiF6, NH4TiOF3 and (NH4)2TiOF4 with the second precursor and then treating the mixture in an ammonia gas stream to obtain red titanium dioxide hetero-junction uniformly doped with rutile phase and anatase phase.

2. The production method according to claim 1, characterized by, The first precursor of B-doped titanium dioxide is formed by: hydrothermally treating TiB2 in an H2SO4 solution system to obtain the first precursor.

3. The production method according to claim 2, characterized by, The H2SO4 solution system is a solution system of HCl and Na2SO4 mixed together.

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

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

6. The method of claim 1, wherein, The temperature of the high-temperature calcining is 600-750 ℃ and the time is 1-2 h.

7. The preparation method according to claim 1, characterized in that, The molar ratio of the ammonium fluorotitanate ((NH4)2TiF6) to the second precursor is (0-0.5):

1.

8. The method of claim 1, wherein, The temperature of the nitriding treatment is 500-600 ℃ and the time is 1-2 h, and the flow rate of the ammonia gas stream is 50-100 mL / min.

9. A red titanium dioxide hetero-phase junction characterized in that, The red titanium dioxide hetero-junction is prepared according to the preparation method of any one of claims 1-8.

10. Use of red titanium dioxide hetero-phase junctions characterized in that, The red titanium dioxide hetero-junction of claim 9 is used for decomposing water.

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