TiN / N-TiO2 photocatalytic composite material for producing hydrogen by decomposing water as well as preparation method and application of TiN / N-TiO2 photocatalytic composite material

Abstract

The invention provides a TiN / N-TiO2 photocatalytic composite material for producing hydrogen by decomposing water as well as a preparation method and application of the TiN / N-TiO2 photocatalytic composite material, and belongs to the technical field of hydrogen production. The preparation method comprises the following steps: calcining rutile phase N-TiO2 powder in a mixed atmosphere of hydrogen and inert gas, so as to obtain the TiN / N-TiO2 photocatalytic composite material. According to the preparation method, the TiN / N-TiO2 heterojunction photocatalyst with the lattice matching heterogeneous interface is successfully prepared. The separation and transfer efficiency of photon-generated carriers in TiN / N-TiO2 can be improved by forming the lattice matching heterogeneous interface. Meanwhile, the light absorption capacity of the TiN / N-TiO2 in the range of 3002000 nm is obviously enhanced. Finally, TiN / N-TiO2 has excellent activity of photocatalytic decomposition of water to produce hydrogen.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production technology, and relates to photocatalytic materials, specifically to a TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting, its preparation method, and its application. Background Technology

[0002] With the rapid development of global industrialization and urbanization, over-reliance on fossil fuels has triggered a severe energy crisis and environmental problems, such as the greenhouse effect and climate change. Therefore, finding a clean, renewable, and efficient alternative energy source has become a global focus. Among numerous candidate energy sources, hydrogen is considered one of the most promising ideal green energy sources due to its high calorific value and the fact that its combustion product is only water, achieving true zero carbon emissions. Among various "green hydrogen" production technologies, photocatalytic water splitting technology is considered a highly attractive approach because it can directly utilize inexhaustible solar energy to decompose water into hydrogen and oxygen. This technological route has significant advantages such as mild reaction conditions, simple process, and no pollution. However, the practical application of photocatalytic water splitting technology still faces significant challenges, with the core bottleneck being the photocatalyst material itself. Developing a novel, highly efficient photocatalyst with a broad spectral response, high carrier separation efficiency, excellent stability, and abundant active sites is crucial for promoting the practical application of solar photocatalytic hydrogen production technology and fundamentally solving energy and environmental problems.

[0003] Titanium dioxide (TiO2), as a classic semiconductor photocatalytic material, has been widely used in photocatalysis research and is considered a benchmark material in this field due to its outstanding advantages such as chemical stability, strong resistance to photocorrosion, non-toxicity, low cost, and abundant reserves. However, the inherent physicochemical properties of titanium dioxide also severely limit its photocatalytic performance. First, its wide bandgap means it can only respond to the high-energy but small-scale ultraviolet light portion of the solar spectrum, failing to effectively utilize visible light, which accounts for 43% of solar energy, resulting in a significant waste of solar energy resources. Second, the rapid recombination of photogenerated electron-hole pairs in and on the surface of titanium dioxide greatly reduces the number of effective charge carriers participating in surface redox reactions, leading to generally low quantum efficiency. These problems severely restrict the performance of unmodified pure-phase titanium dioxide photocatalysts in practical applications. Therefore, effective physical or chemical modification of titanium dioxide is necessary to expand its spectral response range and suppress the recombination of photogenerated charge carriers in order to significantly improve its photocatalytic activity and meet the needs of practical applications.

[0004] To overcome the bottlenecks of low solar energy utilization efficiency and rapid carrier recombination in traditional photocatalysts (such as titanium dioxide), plasmonic materials with localized surface plasmon resonance (LSPR) offer an effective solution. Among them, titanium nitride (TiN), as a non-noble metal plasmonic material, is considered an ideal choice for constructing high-performance composite photocatalysts due to its wide LSPR absorption range, low cost, and high thermal and chemical stability. However, a large carrier transport barrier exists at the interface between the plasmonic material and the semiconductor photocatalyst, resulting in low carrier separation efficiency and a less than ideal hydrogen evolution rate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen, its preparation method, and its application. This invention solves the technical problem in existing technologies where a large carrier transport barrier exists at the interface between plasma materials and semiconductor photocatalysts, resulting in low carrier separation efficiency and an insufficient hydrogen evolution rate of the photocatalyst.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting, the method comprising: calcining rutile N-TiO2 powder at a temperature of 700-800℃ for 3-6 hours in a mixed atmosphere of hydrogen and inert gas to obtain the TiN / N-TiO2 photocatalytic composite material.

[0007] The present invention also has the following technical features: Specifically, the temperature is increased to the required calcination temperature at a heating rate of 2–5 °C / min.

[0008] Specifically, in the mixed atmosphere, the volume ratio of hydrogen to inert gas is 1:(15-20); the flow rate of the mixed atmosphere is 35-45 mL / min.

[0009] Specifically, the inert gas is selected from argon or helium.

[0010] Specifically, the preparation process of rutile N-TiO2 powder includes: mixing soluble titanium source organic solvent, soluble oxygen source organic solvent, and water evenly to obtain a mixed solution; slowly adding a soluble nitrogen source solution dropwise to the mixed solution to form a white precipitate, centrifuging and drying the precipitate, and then calcining the white precipitate in air to obtain anatase N-TiO2 powder; calcining the anatase N-TiO2 powder in an inert atmosphere to obtain rutile N-TiO2 powder.

[0011] Specifically, the soluble titanium source organic solvent is tetrabutyl titanate; the soluble oxygen source organic solvent is glacial acetic acid; the soluble nitrogen source solution is ammonia; and the molar ratio of tetrabutyl titanate, glacial acetic acid and ammonia is 5:10:(1-2).

[0012] Specifically, the calcination temperature in air is 300–500℃, and the time is 1–3 hours.

[0013] Specifically, the calcination temperature in an inert atmosphere is 700–800℃, and the time is 1–3 hours.

[0014] The present invention also protects a TiN / N-TiO2 photocatalytic composite material prepared by the preparation method described above.

[0015] This invention also protects the application of the TiN / N-TiO2 photocatalytic composite material as described above as a photocatalyst for hydrogen production by water splitting.

[0016] Specifically, the application includes: dispersing the photocatalyst in water, adding triethanolamine as a hole sacrificial agent, and performing ultrasonic dispersion; subsequently, transferring the resulting mixed solution to a photocatalytic reactor, subjecting the reaction system to vacuum treatment, and then operating at 100 mW cm⁻¹. 2 The photocatalytic reaction was carried out under xenon lamp irradiation; magnetic stirring was maintained throughout the reaction process, and the temperature of the reaction solution was kept at 6°C.

[0017] Specifically, the mass ratio of the photocatalyst to the volume of water is 4 mg: 9 mL.

[0018] Specifically, the volume ratio of triethanolamine to water is 1:9.

[0019] Compared with the prior art, the present invention has the following technical effects: This invention prepares a TiN / N-TiO2 heterojunction photocatalyst with effective carrier separation capability by forming a lattice-matched heterointerface through epitaxial growth, achieving high-efficiency hydrogen evolution performance. Due to the difference in Fermi levels between N-TiO2 and TiN, electrons transfer from TiN to N-TiO2 upon contact, and the lattice-matched heterointerface can serve as a rapid carrier transfer channel, significantly improving the separation and transfer efficiency of photogenerated carriers in TiN / N-TiO2. Simultaneously, TiN / N-TiO2 exhibits high efficiency at 300°C. It exhibits enhanced light absorption in the 2000 nm range. Furthermore, the lattice-matched heterostructure in the TiN / N-TiO2 photocatalytic composite material can effectively suppress the backflow of photogenerated electrons, thereby reducing recombination and achieving efficient separation of photogenerated carriers. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of TiN / N-TiO2 prepared in Example 2 of the present invention; Figure 2 The X-ray diffraction patterns of N-TiO2 and TiN / N-TiO2 prepared in Example 2, Comparative Example 1 and Comparative Example 2 of this invention are shown below. Figure 3 The UV-Vis-NIR diffuse reflectance spectra of N-TiO2 and TiN / N-TiO2 prepared in Comparative Example 1 and Example 2 of this invention; Figure 4 Electrochemical impedance spectroscopy diagrams of N-TiO2, TiN+N-TiO2 and TiN / N-TiO2 prepared in Comparative Examples 1-2 and Example 2 of this invention; Figure 5 The graphs show the rates of photocatalytic water splitting to H2 prepared by N-TiO2, TiN+N-TiO2 and TiN / N-TiO2 in Comparative Examples 1-2 and Example 2 of this invention. Figure 6 The diagram shows the cycle stability of photocatalytic water splitting to H2 prepared in Comparative Examples 1-2 and Example 2 of this invention.

[0021] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0022] In this invention: N-TiO2 refers to nitrogen-doped titanium dioxide.

[0023] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the art.

[0024] The technical concept of this invention is as follows: N-TiO2 powder is placed in the central region of a heating container and calcined in a mixed atmosphere of hydrogen and an inert gas to obtain a TiN / N-TiO2 photocatalytic composite material. During calcination, the doped N in N-TiO2 acts as a nitrogen source, epitaxially growing TiN along the titanium dioxide boundary, ultimately forming the TiN / N-TiO2 photocatalytic composite material. Simultaneously, during calcination, the inert gas helps improve the uniformity of the reaction, while hydrogen promotes the growth of the material's crystal structure and effectively removes oxides or impurities from the material surface.

[0025] Following the above technical ideas and solutions, the following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0026] Example 1 This embodiment provides a method for preparing a TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting, which specifically includes the following steps: Step 1, Preparation of N-TiO2: Add 5 mL of glacial acetic acid to 10 mL of tetrabutyl titanate solution, maintain at approximately 20 °C, and magnetically stir the mixture for 5 min. Then, slowly add 30% concentrated ammonia at a rate of 1 mL / min until the pH reaches 9. Rinse the white precipitate repeatedly with deionized water and dry in an oven at 85 °C for 12 h. Grind in agate slurry and calcine in a box-type resistance furnace at 400 °C for 2 h in air atmosphere. Calcine the resulting yellow powder at 800 °C for 2 h in Ar atmosphere to obtain N-TiO2 (rutile crystal form).

[0027] Step 2: Place 500 mg of N-TiO2 powder into a ceramic boat, cover the ceramic boat with a lid, place it in a tube furnace, and introduce Ar / H2 with a volume ratio of H2 to Ar of 1:18 and a flow rate of 40 mL / min. Heat to 800 °C at a heating rate of 5 °C / min and calcine at a constant temperature for 3 hours to obtain TiN / N-TiO2 (T3).

[0028] Example 2 This embodiment provides a method for preparing a TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting, which specifically includes the following steps: Step 1, Preparation of N-TiO2: Same as in Example 1.

[0029] Step 2: Place 500 mg of N-TiO2 powder into a ceramic boat, cover the ceramic boat with a lid, place it in a tube furnace, and introduce Ar / H2 with a volume ratio of H2 to Ar of 1:18 and a flow rate of 40 mL / min. Heat to 800 °C at a heating rate of 5 °C / min and calcine at a constant temperature for 4 hours to obtain TiN / N-TiO2 (T4).

[0030] Example 3 This embodiment provides a method for preparing a TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting, which specifically includes the following steps: Step 1, Preparation of N-TiO2: Same as in Example 1.

[0031] Step 2: Place 500 mg of N-TiO2 powder into a ceramic boat, cover the ceramic boat with a lid, place it in a tube furnace, and introduce Ar / H2 with a volume ratio of H2 to Ar of 1:18 and a flow rate of 40 mL / min. Heat to 800 °C at a heating rate of 5 °C / min and calcine at a constant temperature for 5 hours to obtain TiN / N-TiO2 (T5).

[0032] Example 4 This embodiment provides a method for preparing a TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting, which specifically includes the following steps: Step 1, Preparation of N-TiO2: Same as in Example 1.

[0033] Step 2: Place 500 mg of N-TiO2 powder into a ceramic boat, cover the ceramic boat with a lid, place it in a tube furnace, and introduce Ar / H2 with a volume ratio of H2 to Ar of 1:18 and a flow rate of 40 mL / min. Heat to 800 °C at a heating rate of 5 °C / min and calcine at a constant temperature for 6 hours to obtain TiN / N-TiO2 (T6).

[0034] Comparative Example 1 This embodiment provides a method for preparing rutile N-TiO2, which specifically includes the following steps: Add 5 mL of glacial acetic acid to 10 mL of tetrabutyl titanate solution, maintain at approximately 20 °C, and magnetically stir the mixture for 5 min. Then, slowly add 30% concentrated ammonia at a rate of 1 mL / min until the pH reaches 9. Rinse the white precipitate repeatedly with deionized water and dry in an oven at 85 °C for 12 h. Grind the precipitate in agate slurry and calcine it in a box-type resistance furnace at 400 °C for 2 h in air atmosphere to obtain a yellow powder, N-TiO2 (anatase). Calcine the yellow powder in an Ar atmosphere at 800 °C for 2 h to obtain N-TiO2 (rutile).

[0035] Comparative Example 2 This comparative example provides a method for preparing a mixed material of N-TiO2 and TiN. The method specifically includes the following steps: 1g of N-TiO2 and 100mg of TiN powder sample are added to a mortar and ground until uniformly mixed to obtain TiN+N-TiO2 powder. The particle size of the TiN / N-TiO2 powder is 0.5–2μm; the particle size of the TiN powder is 10–200nm.

[0036] Example 5 This embodiment describes the application of the TiN / N-TiO2 photocatalytic composite material prepared in Example 2 as a photocatalyst for water splitting to produce hydrogen, with Comparative Examples 1 and 2 as controls. The application includes: dispersing 20 mg of the photocatalyst in 45 mL of deionized water, adding 5 mL of triethanolamine as a hole sacrificial agent, and performing ultrasonic dispersion for 30 minutes. Subsequently, the resulting mixed solution is transferred to a photocatalytic reactor, and the reaction system is evacuated until the vacuum reaches 0.3 kPa. Then, the reaction is carried out at 100 mW / cm². 2The photocatalytic reaction was carried out under xenon lamp irradiation; magnetic stirring was maintained throughout the reaction, and a circulating cooling water system was used to maintain the reaction solution temperature at 6°C. The gases generated during the experiment were transferred every 30 minutes via argon to a gas chromatograph (Shimadzu GC) equipped with a thermal conductivity detector. 2014c), and analyzed by molecular sieve column.

[0037] Characterization and effect verification: Figure 1 The image shown is a scanning electron microscope (SEM) image of the TiN / N-TiO2 prepared in Example 2. Figure 1 It can be seen that in the morphology of TiN / N-TiO2, TiN nanoparticles are loaded on the surface of N-TiO2 microsheets.

[0038] Figure 2 The images show X-ray diffraction (XRD) patterns of N-TiO2 and TiN / N-TiO2 prepared in Comparative Example 1 and Example 2. Figure 2 As can be seen from the data, Example 2 contains diffraction peaks of TiN and N-TiO2, which indicates the successful preparation of TiN / N-TiO2.

[0039] Figure 3 The UV-Vis-NIR diffuse reflectance spectra of N-TiO2 and TiN / N-TiO2 prepared in Comparative Example 1 and Example 2 are shown. Figure 3 It can be seen that TiN / N-TiO2 exhibits enhanced light absorption in both the visible and near-infrared regions, which is superior to N-TiO2.

[0040] Figure 4 Electrochemical impedance spectroscopy (EIS) diagrams of N-TiO2, TiN+N-TiO2, and TiN / N-TiO2 prepared in Comparative Examples 1, 2, and 2. From... Figure 4 It can be seen that the TiN / N-TiO2 sample has the smallest arc radius, indicating that the interfacial charge transfer resistance is the lowest in TiN / N-TiO2, and the formation of the lattice-matched heterojunction is conducive to the transport of charge carriers.

[0041] Figure 5 The rates of photocatalytic water splitting to H2 production from N-TiO2, TiN+N-TiO2, and TiN / N-TiO2 prepared in Comparative Examples 1-2 and Example 2 are shown. Figure 5 It can be seen that N-TiO2 exhibits a relatively low photocatalytic hydrogen production rate of 0.26 mmol g. 1 h 1 TiN / N-TiO2 exhibited the strongest photocatalytic hydrogen production performance, with a hydrogen production rate of 6.23 mmol g. 1 h 1 It is 23.96 times that of N-TiO2, and also higher than the photocatalytic activity of the mechanically mixed sample TiN+N-TiO2.

[0042] Figure 6 This is a cycle stability diagram of the photocatalytic water splitting to H2 production from TiN / N-TiO2 prepared in Example 2. Figure 6 It can be seen that after a continuous catalytic reaction of up to 16 hours, the performance of TiN / N-TiO2 remained almost unchanged, indicating that TiN / N-TiO2 has excellent cycle stability.

[0043] In summary, this invention provides a TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen, its preparation method, and its application. First, a precipitation method was used to prepare N-TiO2 with a nanosheet morphology. Then, a calcination method was used to epitaxially grow TiN nanoparticles on the surface of the N-TiO2 microsheets, successfully preparing the TiN / N-TiO2 photocatalytic composite material. Due to the difference in Fermi levels between N-TiO2 and TiN, electrons transfer from TiN to N-TiO2 upon contact. During this transfer, the lattice-matched heterojunction provides a rapid carrier transfer channel, significantly improving the separation and transfer efficiency of photogenerated carriers in TiN / N-TiO2. Simultaneously, TiN / N-TiO2 exhibits high efficiency at 300°C. It exhibits enhanced light absorption in the 2000 nm range. Ultimately, TiN / N-TiO2 demonstrates excellent photocatalytic water splitting activity for hydrogen production.

Claims

1. A method for preparing a TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen, characterized in that, The method includes calcining rutile N-TiO2 powder in a mixed atmosphere of hydrogen and inert gas to obtain TiN / N-TiO2 photocatalytic composite material.

2. The preparation method of the TiN / N-TiO2 photocatalytic composite material for hydrogen production by water splitting as described in claim 1, characterized in that, The calcination temperature is 700–800℃, the calcination time is 3–6 hours, and the heating rate during calcination is 2–5℃ / min.

3. The preparation method of the TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen as described in claim 1, characterized in that, In the mixed atmosphere, the volume ratio of hydrogen to inert gas is 1:(15-20); the flow rate of the mixed atmosphere is 35-45 mL / min.

4. The preparation method of the TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen as described in claim 1, characterized in that, The inert gas is selected from argon and helium.

5. The preparation method of the TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen as described in claim 1, characterized in that, The preparation process of rutile N-TiO2 powder includes: A soluble titanium source organic solvent, a soluble oxygen source organic solvent, and water are mixed evenly to obtain a mixed solution. A soluble nitrogen source solution is slowly added dropwise to the mixed solution to form a white precipitate. After centrifugation and drying, the white precipitate is calcined in air to obtain anatase N-TiO2 powder. The anatase N-TiO2 powder is then calcined in an inert atmosphere to obtain rutile N-TiO2 powder.

6. The preparation method of the TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen as described in claim 5, characterized in that, The soluble titanium source organic solvent is tetrabutyl titanate; the soluble oxygen source organic solvent is glacial acetic acid; the soluble nitrogen source solution is ammonia; and the molar ratio of tetrabutyl titanate, glacial acetic acid and ammonia is 5:10:(1-2).

7. The preparation method of the TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen as described in claim 5, characterized in that, The calcination temperature in air is 300–500℃, and the time is 1–3 hours.

8. The preparation method of the TiN / N-TiO2 photocatalytic composite material for water splitting to produce hydrogen as described in claim 5, characterized in that, The calcination temperature in an inert atmosphere is 700–800℃, and the time is 1–3 hours.

9. A TiN / N-TiO2 photocatalytic composite material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the TiN / N-TiO2 photocatalytic composite material as described in claim 9 as a photocatalyst for hydrogen production by water splitting.

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