Gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material and preparation method and application thereof

Abstract

Gallium phosphide-nitrogen-doped titanium dioxide visible-light photocatalytic nanocomposite and its preparation method and application, comprising the following steps: preparing GaP nanoparticles; preparing N-doped TiO2 sol; dispersing GaP nanoparticles in N-doped TiO2 sol to prepare GaP@N-TiO2 sol; coating the inner wall of a quartz tube with the GaP@N-TiO2 sol, and sintering to obtain a visible-light photocatalytic nanocomposite GaP@N-TiO2 film, which responds to visible light and has strong oxidation and reduction capabilities, effectively improving the photocatalytic performance. The preparation method of the visible-light photocatalytic oxidation-reduction nanocomposite GaP@N-TiO2 is simple and has good stability.

Description

Technical Field

[0001] The invention relates to the field of visible light catalysis, and in particular to a gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material and a preparation method and application thereof. Background Art

[0002] Titanium dioxide (TiO2) semiconductor materials are widely used due to their excellent photocatalytic activity, stable chemical properties, resistance to light corrosion, chemical corrosion, low preparation cost, and non-toxicity. Among them, anatase TiO2 has the best photocatalytic activity and is the most commonly used photocatalyst. However, its band gap is relatively wide (3.2eV), and its photocatalytic oxidation-reduction activity can only be driven by ultraviolet light shorter than 387 nanometers. It has problems such as low utilization of the solar spectrum (accounting for only 4% to 5% of sunlight) and health risks to experimental personnel. There are many different ways to solve this problem. Nitrogen-doped titanium dioxide (N-TiO2) prepared by doping nitrogen (N) into TiO2 can achieve visible light excitation and generate reducing electrons (e - ), generating oxidative holes (h + ) to achieve the purpose of reduction or oxidation.

[0003] Another issue that needs attention is to avoid the conduction band e of single N-TiO2 nanosemiconductor in photocatalytic reaction. - and valence band h + The Z-type heterogeneous composite semiconductor material has a unique e - and h + transfer path, with strong oxidation ability or strong reduction ability. While maintaining the visible light excitation characteristics of N-TiO2 and its valence band h + Based on the strong oxidation ability of N-TiO2, the key to designing a Z-type heterojunction semiconductor composite material with strong reduction ability lies in another semiconductor compounded with N-TiO2. At present, there is no report on the preparation and application of GaP@N-TiO2 composite materials. This invention is funded by the National Natural Science Foundation of China (Fund No.: 22193053). Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problems in the prior art and to provide a gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material and a preparation method and application thereof. The prepared gallium phosphide-nitrogen doped titanium dioxide GaP@N-TiO2 has strong oxidation and reduction capabilities, thereby improving the photocatalytic efficiency.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] The method for preparing a gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material comprises the following steps: preparing GaP nanoparticles; preparing N-TiO2 sol; dispersing the GaP nanoparticles in the N-TiO2 sol to prepare GaP@N-TiO2 sol; coating the sol on the inner wall of a quartz tube, and obtaining a visible light catalytic oxidation-reduction nanocomposite material GaP@N-TiO2 after sintering.

[0007] The specific steps include:

[0008] (1) Preparation of GaP nanoparticles

[0009] Step 1: Sodium phosphide (Na3P) and anhydrous gallium chloride (GaCl3) react in xylene, wash with 100°C xylene, anhydrous ethanol, ultrapure water, and dry to obtain an amorphous precursor substance (product A);

[0010] Step 2: transferring product A to a tube furnace for heat treatment to obtain a mixture of GaP and gallium phosphate (GaPO4) nanoparticles (product B);

[0011] Step 3: Soak the product B in concentrated hydrochloric acid to remove GaPO4 nanoparticles, wash with ultrapure water, vacuum dry or freeze-dry, and purify to obtain GaP nanoparticles.

[0012] Preferably, argon gas is used for protection throughout step 2.

[0013] Preferably, the heating rate of the heat treatment in step 2 is 1-10°C min -1 The heat treatment temperature is 400-800℃ and the holding time is 0.5-5h.

[0014] Preferably, the acid treatment time in step 3 is 6 to 48 hours.

[0015] (2) Preparation of N-TiO2 sol

[0016] Solution 1: Add isopropyl titanate (TTIP) to a mixed solution of anhydrous ethanol and acetylacetone and stir;

[0017] Solution 2: appropriate amounts of different nitrogen source compounds dissolved in anhydrous ethanol;

[0018] Solution 2 was dropped into solution 1, stirred, and allowed to stand for aging to obtain N-TiO2 sol.

[0019] The N source is selected from ammonium acetate (CH3COONH4), triethanolamine ((HOCH2CH2)3N), triethylamine ((C2H5)3N), ethylenediamine (NH2CH2CH2NH2), urea (CH4N2O), ammonia water (NH3·H2O) and hydrazine hydrate (N2H4·H2O), preferably urea (CH4N2O).

[0020] The N:Ti molar ratio of N-TiO2 is 0.25 to 1.75:1, preferably 0.5:1.

[0021] (3) Preparation of GaP@N-TiO2 composite films

[0022] A proper amount of GaP nanomaterial is dispersed in N-TiO2 sol, stirred, and allowed to stand for aging to obtain GaP@N-TiO2 sol.

[0023] The GaP@N-TiO2 sol is filled in a quartz tube, left to stand, and the sol in the quartz tube is removed, dried at low temperature, and then heat treated at high temperature, and the coating and heat treatment processes are repeated five times. Then, it is washed alternately with ultrapure water and anhydrous ethanol, and dried to obtain a GaP@N-TiO2 composite material.

[0024] The Ga:Ti molar ratio of the GaP@N-TiO2 is 0.1 to 10.0:100, preferably 5.0:100.

[0025] The synthesized GaP@N-TiO2 composites can be used for the photocatalytic reduction of trace element ions and the oxidative photodegradation of organic dyes.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] The present invention modifies TiO2 nanomaterials by N doping to achieve visible light absorption excitation, disperses GaP nanoparticles in N-TiO2 sol, and obtains GaP@N-TiO2 composite materials by heat treatment. After being excited by visible light, the carriers (e - and h + ) presents a "Z" type transfer, which solves the problem of GaP and N-TiO2's respective - and h + Therefore, GaP@N-TiO2 has stronger oxidation and reduction capabilities, which improves the photocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 SEM image (a), XRD pattern (b), and UV-Vis-DRS pattern (c) of GaP nanoparticles.

[0029] Figure 2 (a) XRD patterns of N-TiO2 prepared with different N sources, and (b) photocatalytic reduction of As by visible light at 420 nm. III Signal (b).

[0030] Figure 3(a) XRD patterns of N-TiO2 with different N doping ratios, and (b) photocatalytic reduction of As under visible light at 420 nm. III Signal (b), UV-Vis-DRS image of N-TiO2 (molar ratio N:Ti=0.5:1) (c), SEM image of N-TiO2 (molar ratio N:Ti=0.5:1) nanofilm material (d).

[0031] Figure 4 TEM image (a) and SEM image (b) of GaP@N-TiO2 (molar ratio N:Ti=0.5:1, Ga:Ti=0.5:100) nano-semiconductor thin film material.

[0032] Figure 5 XRD pattern (a), UV-Vis-DRS pattern (b) of GaP@N-TiO2 nano-semiconductor thin film material, and visible light 420nm photocatalytic As III Signal (c).

[0033] Figure 6 This is the signal of visible light light catalytic oxidation of rhodamine using GaP@N-TiO2 composite nanomaterials.

[0034] Figure 7 Visible light photocatalytic reduction of As using GaP@N-TiO2 composite nanomaterials III signal.

[0035] Figure 8 Visible light photocatalytic reduction of As using GaP@N-TiO2 composite nanomaterials III Determination of stability. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to these embodiments.

[0037] Embodiment 1:

[0038] Preparation of GaP nanoparticles

[0039] Step 1: In a glove box filled with nitrogen (N2), weigh 0.50g of white phosphorus and 0.39g of sodium metal (Na), add them to 50mL of xylene, stir, and react at 120℃ for 10h to generate a black product, Na3P; weigh 0.65g of anhydrous gallium chloride (GaCl3) and add it to the above system. Continue stirring and react at 80℃ for 2.5h; wash with 100℃ xylene, anhydrous ethanol, and ultrapure water three times in sequence, and dry in vacuum at 45℃ to obtain a brown product A.

[0040] Step 2: Transfer the above product A to a tube furnace and heat it at 5°C min -1 The temperature was raised to 600°C at a rate of 1 °C, kept constant for 1 h, and then naturally cooled to obtain product B.

[0041] Step 3: Soak product B in concentrated HCl for 12 h, wash with ultrapure water until neutral, and freeze-dry to obtain product GaP nanoparticles.

[0042] Figure 1 (a) is a scanning electron microscope (SEM) image of GaP nanoparticles, where GaP appears as microspheres of 150 to 250 nm; Figure 1 (b) is an XRD pattern of the material in the process of preparing GaP nanoparticles, indicating that product A is an amorphous precursor material, and product B is a mixture of gallium phosphide (GaP) and gallium phosphate (GaPO4) nanoparticles. After acid washing, the final product GaP nanoparticles are obtained; Figure 1 (c) is the ultraviolet-visible diffuse reflectance absorption spectrum (UV-Vis-DRS) of GaP, indicating that the band gap of GaP is 2.23 eV and can absorb visible light.

[0043] Embodiment 2:

[0044] Step 1: Selection of N source compounds in N-TiO2 sol

[0045] Solution 1: 10 mL of isopropyl titanate (TTIP) and 2.5 mL of acetylacetone were dissolved in 20 mL of anhydrous ethanol and stirred for 30 min.

[0046] Solution 2: No nitrogen source and different N source solvents: ammonium acetate (CH3COONH4), triethanolamine ((HOCH2CH2)3N), triethylamine ((C2H5)3N), ethylenediamine (NH2CH2CH2NH2), urea (CH4N2O), ammonia (NH3·H2O) and hydrazine hydrate (N2H4·H2O) were added to 20 mL of anhydrous ethanol, and the molar ratio of N:Ti was 0.5:1.

[0047] Solution 2 was stirred at 1 mL min -1 After the addition was completed, the mixed solution was stirred for 1 hour and allowed to stand for 24 hours to obtain light yellow TiO2 and N-TiO2 sols.

[0048] Step 2: Deposition of TiO2 and N-TiO2 nanofilms on the inner wall of the quartz tube

[0049] Before coating, remove organic matter and salts from the surface of the quartz tube to avoid cracking and shedding of the coating. The cleaning steps of the quartz tube are as follows: clean with acetone for 60 minutes; clean with ultrapure water until the effluent pH is 7; -1Wash with NaOH for 12 h, and then wash with excess water until the pH of the effluent is 7; -1 Wash with HCl for 12 hours; wash with ultrapure water until the effluent pH = 7; wash with acetone for 60 minutes; blow dry with nitrogen.

[0050] The quartz tube was filled with the above sol and allowed to stand for 10 min. The sol in the tube was then discharged. The quartz tube was placed at 25 °C for 30 min to form a gel film. The film was dried at 80 °C for 30 min and transferred to a programmed temperature muffle furnace at 1.5 °C min. -1 The temperature was raised to 450℃ at a speed of 100℃ and kept at this temperature for 1 hour. The coating and heat treatment process was repeated five times. The coated quartz tube was rinsed with ultrapure water and anhydrous ethanol three times alternately, dried at 80℃, and sealed to obtain TiO2 and N-TiO2 nanofilms.

[0051] Figure 2 (a) is the XRD pattern of TiO2 and N-TiO2 prepared using different N source solvents; Figure 2 (b) shows that the N-TiO2 photocatalyst can reduce 100 ng mL -1 As III The results of atomic fluorescence spectroscopy (AFS) showed that N-TiO2 can achieve As under visible light absorption excitation. III The photocatalytic reduction effect is best when urea is used as the nitrogen source.

[0052] Embodiment 3:

[0053] Selection of N-doping ratio in N-TiO2 sol

[0054] Solution 1: 10 mL TTIP, 2.5 mL acetylacetone were dissolved in 20 mL anhydrous ethanol and stirred for 30 min.

[0055] Solution 2: Take urea (molar ratio N:Ti=0.25-1.75:1) and add it into 20 mL of anhydrous ethanol.

[0056] Solution 2 was stirred at 1 mL min -1 After the addition was completed, the mixed solution was stirred for 1 hour and allowed to stand for 24 hours to obtain a light yellow N-TiO2 sol.

[0057] The preparation of N-TiO2 nanofilm deposited on the inner wall of the quartz tube is the same as in Example 2.

[0058] Figure 3 (a) is the XRD pattern of N-TiO2 prepared using different N source solvents; Figure 3(b) shows that N-TiO2 photocatalyst reduces 100 μL 100 ng mL under 420 nm light in the presence of 5% formic acid (HCOOH, pH = 3). -1 As III , indicating that the photocatalytic effect is best when the molar ratio of N:Ti in N-TiO2 is 0.5:1; Figure 3 (c) is the UV-Vis-DRS spectra of TiO2 and N-TiO2, indicating that N doping can make N-TiO2 absorb visible light; Figure 3 (d) is a SEM image of N-TiO2 (molar ratio N:Ti=0.5:1) nanofilm, indicating that the average particle size of N-TiO2 is 10nm.

[0059] Embodiment 4:

[0060] Preparation of GaP@N-TiO2 Nanocomposites

[0061] The preparation steps of N-TiO2 (N:Ti=0.5:1) sol are the same as those in Example 2.

[0062] GaP nanomaterial (molar ratio Ga:Ti=0.1-10:100) was dispersed in the N-TiO2 sol prepared above, and the mixture was stirred for 1 hour and allowed to stand for aging to obtain GaP@N-TiO2 sol.

[0063] The steps of depositing GaP@N-TiO2 nanofilm on the inner wall of the quartz tube are the same as those in Example 2.

[0064] Figure 4 (a) is a TEM image of GaP@N-TiO2 nano-semiconductor thin film material, which shows that GaP (111) surface d = 0.31nm and N-TiO2 (101) surface d = 0.35nm, and the dotted line part represents the contact interface between the semiconductor GaP and N-TiO2, indicating that there is a close contact between the GaP semiconductor and the N-TiO2 semiconductor to form a heterojunction; Figure 4 (b) is a SEM image of GaP@N-TiO2 nano-semiconductor thin film material, whose thickness is 800nm.

[0065] Figure 5 (a) is the XRD pattern of the nanocomposite GaP@N-TiO2, which has diffraction peaks of GaP and N-TiO2, indicating that GaP and N-TiO2 have been recombined; Figure 5 (b) shows that the nanocomposite GaP@N-TiO2 can absorb visible light; Figure 5 (c) shows that the GaP@N-TiO2 photocatalyst reduces 100 ng mL under 420 nm light in the presence of formic acid (HCOOH). -1 As III , indicating that the photocatalytic effect is best when the molar ratio of N:Ti in the nanocomposite material GaP@N-TiO2 is 0.5:1 and Ga:Ti=0.5:100.

[0066] Example 5

[0067] GaP@N-TiO2 composite nanomaterials + Oxidation capacity evaluation

[0068] GaP nanomaterial (molar ratio Ga:Ti=0.5:100) was dispersed in the TiO2 sol prepared in Example 2, and the mixture was stirred for 1 hour and allowed to stand for aging to obtain GaP@TiO2 sol. The steps for depositing GaP@TiO2 nanofilm on the inner wall of the quartz tube were the same as those in Example 2.

[0069] The initial mass concentration was 10 mg L -1 Rhodamine B (RhB) solution, 0.5 g L -1 GaP@N-TiO2, GaP@TiO2, N-TiO2, GaP and no catalyst (blank, KB) were placed in the dark for 15 minutes, illuminated with 420nm light for 30 minutes, and the supernatant was taken after centrifugation to measure UV absorption (λ=550nm). Figure 6 The results showed that the degradation rate of Rh B by GaP@N-TiO2 composite nanomaterials under visible light for 30 min was 42.7%, which was stronger than that of GaP (21.7%), N-TiO2 (35.9%) and GaP@TiO2 (37.2%). Figure 6 The middle inset shows the color depth of the RhB solution after photocatalytic degradation, which demonstrates this result more intuitively.

[0070] Example 6

[0071] GaP@N-TiO2 composite nanomaterials - Restoration capability evaluation

[0072] All solutions were purged with argon to remove dissolved oxygen before use. The entire system was purged with argon for 5 minutes before testing to remove dissolved oxygen (O2) in the system. III A mixed solution of 5% HCOOH (pH=3) was passed through a quartz tube coated with GaP@N-TiO2 film, and catalytic reduction was performed under visible light (420nm) to produce AsH3 for AFS determination. Compared with TiO2, N-TiO2 and GaP@TiO2, the composite nanomaterial GaP@N-TiO2 showed better photocatalytic reduction ability ( Figure 7 ).

[0073] Example 7

[0074] Stability evaluation of GaP@N-TiO2 composite nanomaterials

[0075] Under 420nm light, the nanocomposite GaP@N-TiO2 catalyzed the reduction of 100μL 100ng mL -1 As III Standard solution. Figure 8 It shows that GaP@N-TiO2 has good stability, with an RSD of 1.9% (n=11).

[0076] In the present invention, GaP has the advantage of good chemical stability, and more importantly, its band gap is 2.25eV, which can absorb visible light, and its conduction band potential is -1.0V, which has stronger reduction ability than N-TiO2. The Z-type heterojunction GaP@N-TiO2 composite semiconductor material prepared by the present invention can not only be activated by visible light excitation, but also avoid their respective conduction band e - and valence band h + The composite has N-TiO2 valence band h + The oxidation ability and conduction band of GaP - restoration capability.

Claims

1. A method for preparing a gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material, characterized in that The following steps are involved: 1) Preparation of GaP nanoparticles; 2) Preparation of N-doped TiO2 sol; 3) Dispersing GaP nanoparticles in N-doped TiO2 sol to prepare GaP@N-TiO2 sol; 4) The GaP@N-TiO2 sol is coated on the inner wall of a quartz tube, and after sintering, a visible light-photocatalytic nanocomposite GaP@N-TiO2 film is obtained.

2. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 1, characterized in that: Step 1) includes the following: 1.1) Sodium phosphide and anhydrous gallium chloride react in xylene, wash with xylene, anhydrous ethanol, ultrapure water, and dry to obtain product A; 1.2) Transfer product A to a tube furnace for heat treatment to obtain product B; 1.3) Soak the product B in concentrated hydrochloric acid, wash with ultrapure water, vacuum dry or freeze dry, and purify to obtain GaP nanoparticles.

3. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 2, characterized in that: In step 1.2), argon protection is used and the heating rate of heat treatment is 1-10 ℃ min -1 , the heat treatment temperature is 400-800 ℃, and the holding time is 0.5-5 h; in step 1.3), the concentrated hydrochloric acid immersion time is 6-48 h.

4. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 1, characterized in that: Step 2) includes the following: 2.1) Prepare solution 1: Add isopropyl titanate into a mixed solution of anhydrous ethanol and acetylacetone and stir; 2.2) Prepare solution 2: dissolve the nitrogen source compound in anhydrous ethanol; 2.3) Solution 2 is dropped into solution 1, stirred, and allowed to stand for aging to obtain N-doped TiO2 sol.

5. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 4, characterized in that: In step 2.2), the nitrogen source is selected from at least one of ammonium acetate, triethanolamine, triethylamine, ethylenediamine, urea, ammonia water and hydrazine hydrate.

6. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 4, characterized in that: In the preparation of N-doped TiO2 sol, the N:Ti molar ratio is 0.25-1.75:

1.

7. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 1, characterized in that: In the preparation of GaP@N-TiO2 sol, the molar ratio of Ga:Ti is 0.1 to 10.0:

100.

8. The method for preparing the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 1, characterized in that: Step 4) includes the following: The GaP@N-TiO2 sol is filled in a quartz tube, allowed to stand, and the sol in the quartz tube is removed, dried at low temperature, and then heat treated at high temperature. The coating and heat treatment processes are repeated several times; then, it is washed alternately with ultrapure water and anhydrous ethanol, and dried to obtain a composite material GaP@N-TiO2 film.

9. Gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. The use of the gallium phosphide-nitrogen doped titanium dioxide visible light catalytic nanocomposite material according to claim 9, characterized in that: For As III Photocatalytic reduction and oxidative photodegradation of organic dyes.

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