TiO2 nanosheets loaded with Pt metal nanoclusters and their preparation method

Abstract

TiO2 nanosheet loaded with Pt metal nanoclusters and a preparation method thereof: an aqueous solution of H2PtCl6, ammonia and nano-TiO2 are added into an aqueous solution of polyvinylpyrrolidone and mixed uniformly in dark to obtain a mixed solution; the mixed solution is centrifuged to obtain a solid; the solid is cleaned, dried and ground to obtain a powder; the powder is calcined and naturally cooled to room temperature. The present application successfully realizes loading of Pt metal nanoclusters on the surface of TiO2 nanosheet under mild conditions, and this structure can significantly reduce the band gap of the photocatalyst, reduce the recombination rate of photo-generated electron-hole pairs, and thus improve the photocatalytic performance of the photocatalyst as a photocatalyst.

Description

Technical Field

[0001] This invention relates generally to a photocatalytic material, and more specifically to a Pt / TiO2 nanocomposite material. Background Technology

[0002] Hydrogen is a sustainable and clean energy source. Photocatalytic hydrogen evolution reaction (HER), aided by photocatalysts, is crucial for the development of clean energy technologies. TiO2 has become a common photocatalyst due to its relatively strong heat resistance and chemical durability, low cost, high photocatalytic efficiency, high refractive index, and non-toxicity. However, due to the wide bandgap of TiO2, its energy conversion efficiency as a photocatalyst for direct water splitting under sunlight is relatively low. Its photocatalytic performance can be improved by loading noble metals (such as Pt) onto the TiO2 surface.

[0003] Methods for synthesizing Pt / TiO2 nanocomposites typically focus on loading Pt single atoms or particles onto the TiO2 surface, as disclosed in CN109289838B, CN112403460B, CN108479766B, and CN102500363B. Other synthetic methods for Pt / TiO2 nanocomposites include loading Pt onto TiO2 matrices of different morphologies, such as CN110813280B, CN106732550B, CN103223338B, and CN 108325519B. However, these known synthetic methods are all relatively complex and require stringent conditions, which are not conducive to large-scale industrial production. Summary of the Invention

[0004] The purpose of this invention is to provide a photocatalyst for efficient photocatalytic water splitting to produce hydrogen.

[0005] According to a first aspect of the present invention, a method for preparing a photocatalyst is provided, comprising:

[0006] Provide an aqueous solution of polyvinylpyrrolidone, wherein the concentration of polyvinylpyrrolidone is 5–15 mg / ml;

[0007] Provide an aqueous solution of H2PtCl6, wherein the Pt ion concentration is 1–3 mg / ml;

[0008] Provides TiO2 with an average particle size of 20–30 nanometers;

[0009] A mixed solution was prepared by adding H2PtCl6 aqueous solution, ammonia water and TiO2 to polyvinylpyrrolidone aqueous solution and mixing them evenly in the dark. The mass ratio of polyvinylpyrrolidone, TiO2 and Pt ions was (80-120):(80-120):1 and the volume ratio of polyvinylpyrrolidone aqueous solution to ammonia water was (80-120):1.

[0010] The mixed solution was separated by centrifugation to obtain a solid.

[0011] Clean and dry the resulting solid;

[0012] Grind the dried solid into powder;

[0013] The calcined powder is naturally cooled to room temperature to obtain the photocatalyst, wherein the calcination temperature is 380℃~420℃ and the calcination time is 0.5~1.5h.

[0014] According to the preparation method of the present invention, the cleaned solid preferably includes washing with deionized water and ethanol in sequence.

[0015] According to the preparation method of the present invention, the drying temperature is preferably 55℃~65℃, and the drying time is preferably 5~10h.

[0016] According to the preparation method of the present invention, the mixing time is preferably 3 to 5 hours.

[0017] According to the preparation method of the present invention, nano-TiO2 is preferably provided by the following method:

[0018] Hydrofluoric acid is reacted with tetrabutyl titanate, followed by centrifugation to obtain a precipitate, which is then calcined to obtain nano-TiO2. Hydrofluoric acid is preferably added dropwise to tetrabutyl titanate under stirring, followed by a high-pressure (1–2 MPa) and constant-temperature (140°C–160°C) reaction for 1–3 hours. The preferred calcination temperature is 330°C–370°C, and the preferred calcination time is 1–3 hours.

[0019] According to another aspect of the present invention, a photocatalyst prepared according to the above method is also provided.

[0020] The photocatalyst according to the present invention is preferably used for photocatalytic water splitting to produce hydrogen.

[0021] This invention successfully achieved the loading of Pt metal nanoclusters (average size less than 1 nm) onto the surface of TiO2 nanosheets under mild conditions. This structure can significantly reduce the band gap of the photocatalyst and decrease the recombination rate of photogenerated electron-hole pairs, thereby improving its photocatalytic performance. The photocatalyst of this invention is particularly suitable for photocatalytic water splitting to produce hydrogen, exhibiting higher hydrogen production efficiency and stability. Attached Figure Description

[0022] Figure 1(a) shows the microstructure of nano-TiO2;

[0023] Figure 1(b) shows the state of Pt metal nanoclusters in the photocatalyst material prepared according to the present invention;

[0024] Figure 2UV-vis absorption spectra of different photocatalyst materials;

[0025] Figure 3 Photoluminescence spectra of different photocatalyst materials;

[0026] Figure 4 Photocurrent response diagrams for different photocatalyst materials;

[0027] Figure 5 Nyquist plots for different photocatalyst materials;

[0028] Figure 6 Photocatalytic water splitting to hydrogen production curves for different photocatalyst materials. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments and accompanying drawings. Those skilled in the art should understand that the embodiments and accompanying drawings are only for a better understanding of the present invention and are not intended for any limiting purpose.

[0030] Example: Preparation of TiO2 nanomaterials supported on Pt metal nanoclusters

[0031] Preparation of titanium dioxide nanosheets: 3 ml of hydrofluoric acid (HF) was added dropwise to 25 ml of tetrabutyl titanate (Ti(OBu)4) under vigorous stirring (280 r / min) for 10 minutes to obtain a reaction mixture. The reaction mixture was then transferred to a 50 ml autoclave (1 MPa) and reacted at 150 °C for 2 hours to obtain a precipitate. The precipitate was separated by centrifugation and washed three times repeatedly with water and ethanol. The precipitate was then dried overnight under vacuum at 60 °C and calcined at 350 °C for 2 hours to obtain nano-titanium dioxide, the structure of which is analyzed later.

[0032] Impregnation and mixing: Dissolve 200 mg of polyvinylpyrrolidone (PVP) in 20 ml of deionized water, then add 200 mg of the above-prepared TiO2, 0.85 ml of H2PtCl6 aqueous solution (with a Pt ion concentration of 2.38 mg / ml), and 0.2 ml of ammonia water in sequence. Place in the dark and stir for 4 h to obtain a mixed solution.

[0033] Cleaning and drying: After centrifuging the mixed solution, a white solid was obtained. It was then washed with deionized water and ethanol in sequence and dried in an oven at 60°C overnight.

[0034] Grinding and calcination: The dried solid was ground into powder and calcined in a muffle furnace at 400℃ for 1 hour to obtain TiO2 nanomaterials loaded with Pt metal nanoclusters: Pt c / TiO2.

[0035] Comparative Example 1: Preparation of TiO2 nanomaterials loaded with Pt single atoms

[0036] The rest is the same as in the embodiment, except that in the impregnation and mixing step, 200 mg of disodium ethylenediaminetetraacetate is used instead of PVP dissolved in 20 ml of deionized water; TiO2 nanomaterials loaded with Pt single atoms are obtained: Pt SA / TiO2.

[0037] Comparative Example 2: Preparation of TiO2 nanomaterials loaded with Pt nanoparticles

[0038] The rest is the same as in the embodiment, except that PVP is not added to the 20 ml of deionized water used in the impregnation and mixing step; TiO2 nanomaterials loaded with Pt nanoparticles are obtained: Pt P / TiO2.

[0039] Performance comparison test

[0040] The microstructure of the prepared nano-TiO2 obtained by transmission electron microscopy is shown in Figure 1(a), which is a nanosheet structure with an average particle size of 20-30 nanometers.

[0041] For the TiO2 nanomaterials loaded with Pt metal nanoclusters prepared in the above embodiments, the state of Pt metal nanoclusters was obtained by high-angle annular dark-field transmission electron microscopy, as shown in Figure 1(b): each nanocluster successfully loaded on the surface of TiO2 nanosheets consists of 10-20 Pt atoms.

[0042] Figure 2 The UV-vis absorption spectra of four materials that can be used as photocatalysts are compared, including TiO2: the nano-titanium dioxide prepared above; Pt SA / TiO2: TiO2 nanomaterials loaded with Pt single atoms prepared in Comparative Example 1; Pt P / TiO2: TiO2 nanomaterials loaded with Pt nanoparticles prepared in Comparative Example 2; Pt c / TiO2: TiO2 nanomaterials loaded with Pt metal nanoclusters prepared in the examples. From Figure 2 It can be seen that Pt c / TiO2 exhibited the strongest light absorption capacity in the visible light region, indicating that it increased the absorption capacity of visible light compared to other materials, thereby improving the photocatalytic performance of the catalyst.

[0043] Figure 3 A comparison of the photoluminescence spectra of the four photocatalyst materials mentioned above, among which Pt c / TiO2 exhibited the weakest photoluminescence intensity, indicating that it had the lowest photogenerated electron-hole recombination rate compared to the other materials, thus improving photocatalytic efficiency.

[0044] Figure 4 A comparison of the photocurrent responses of the four photocatalyst materials mentioned above, among which Ptc / TiO2 exhibited the strongest photocurrent response, indicating that it significantly enhances the carrier migration efficiency in the material compared to other materials.

[0045] Figure 5 The Nyquist plots for the four photocatalyst materials mentioned above are shown, where Pt c / TiO2 exhibits the smallest arc, indicating that it has the highest charge transfer efficiency compared to the other materials.

[0046] Figure 6 The photocatalytic hydrogen production performance of the above four photocatalyst materials by water splitting is shown. It can be seen that Pt... c The hydrogen production performance of / TiO2 is 16.79 times that of nano-TiO2 and Pt P / 2.45 times that of TiO2, Pt SA / 9.21 times that of TiO2.

Claims

1. A method for preparing a photocatalyst for photocatalytic water splitting to produce hydrogen, comprising: Provide an aqueous solution of polyvinylpyrrolidone, wherein the concentration of polyvinylpyrrolidone is 5~15 mg / ml; Provide an aqueous solution of H2PtCl6, wherein the Pt ion concentration is 1~3 mg / ml; TiO2 nanosheets with an average particle size of 20-30 nanometers are provided; A mixed solution was prepared by adding H2PtCl6 aqueous solution, ammonia water and TiO2 nanosheets to polyvinylpyrrolidone aqueous solution and mixing them evenly in the dark. The mass ratio of polyvinylpyrrolidone, TiO2 nanosheets and Pt ions was (80~120):(80~120):1, and the volume ratio of polyvinylpyrrolidone aqueous solution to ammonia water was (80~120):

1. The mixed solution was separated by centrifugation to obtain a solid. The obtained solid is cleaned and dried, wherein the drying temperature is 55℃~65℃ and the drying time is 5~10h; Grind the dried solid into powder; The calcined powder is naturally cooled to room temperature to obtain the photocatalyst, wherein the calcination temperature is 380℃~420℃ and the calcination time is 0.5~1.5 h.

2. The preparation method according to claim 1, wherein cleaning the obtained solid comprises washing with deionized water and ethanol in sequence.

3. The preparation method according to claim 1, wherein the mixing time is 3-5 h.

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