Oxygen vacancy-enriched NiTiO3-coated Ni heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic materials, and relates to an oxygen vacancy-enriched NiTiO3-coated Ni heterojunction photocatalyst and a preparation method and application thereof, and the preparation method comprises the following steps: (1) preparing a NiTiO3 precursor; and (2) preparing the NiTiO3 and Ni heterojunction photocatalyst rich in oxygen vacancy. The heterojunction photocatalyst can be applied to photocatalytic production of hydrogen peroxide. According to the NiTiO3-Ni composite visible-light-driven photocatalyst prepared by the method, due to the fact that the NiTiO3-Ni composite visible-light-driven photocatalyst contains a large number of oxygen vacancies, absorption and utilization of visible light by the catalyst are greatly improved, and high-conductivity Ni and NiTiO3 are in closer contact, so that photo-induced electrons and holes can be better separated, and the interface charge separation efficiency is remarkably improved. The photocatalyst has high hydrogen peroxide generation efficiency and stability under the irradiation of visible light; the photocatalyst is low in preparation condition requirement and simple to operate, and raw materials are low in price and easy to obtain; the photocatalyst is environment-friendly and high in visible light catalysis efficiency, and has a wide application prospect in the field of photocatalysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation and visible light photocatalysis, and specifically relates to an oxygen-rich NiTiO 3 @Ni heterojunction photocatalyst and its preparation method and application. Background Art

[0002] Hydrogen peroxide (H 2 O 2 ) is a very promising energy carrier and is widely used as an environmentally friendly oxidant in organic synthesis, drinking water treatment, wastewater treatment and other industrial and medical fields. With the improvement of environmental protection requirements, it is expected that H 2 O 2 The demand for H will increase significantly. 2 O 2 The process is complicated and there is a phenomenon of organic matter polluting the environment. 2 and H 2 Photocatalytic production of H using O as raw material, solar energy as energy, and semiconductors as photocatalysts 2 O 2 It is a green chemical process with the advantages of mild reaction conditions, simple and controllable operation and no secondary pollution. 2 O 2 It has attracted widespread attention. Metal oxides have the advantages of low cost, relatively good stability and biocompatibility, easy preparation and a variety of modification strategies. More importantly, the appropriate energy band position gives metal oxides good reduction and oxidation abilities, which is beneficial to oxygen reduction (ORR) and water oxidation (WOR) processes. NiTiO 3 As a new type of photocatalyst, NiTiO has been intensively studied. It meets the thermodynamic conditions for WOR to occur, but its kinetics are limited. Limited light absorption and severe photogenerated carrier recombination remain the main barriers to its widespread application. Therefore, how to promote NiTiO 3 The effective separation of charge carriers is crucial to improving its photocatalytic performance. Interface regulation is one of the most effective methods to promote effective separation of charge carriers and thus improve photocatalytic activity.

[0003] Oxygen vacancy engineering, as an important structural control method, can affect the local geometric structure and electronic structure of materials. Oxygen vacancy defects can serve as active sites for catalytic reactions, thereby affecting the activity of photocatalytic reactions. Therefore, it has very important research significance. Introducing an appropriate amount of oxygen vacancy defects on the surface of oxide semiconductors usually moves the Fermi level upward, resulting in defect energy levels in the band gap, thereby improving the light absorption capacity and narrowing the band gap width; oxygen vacancy defects can also serve as active sites to optimize the adsorption energy of reactants, reduce reaction energy barriers, and promote molecular activation; in addition, the presence of oxygen vacancies can also improve the conductivity of materials and accelerate charge separation and migration efficiency. Therefore, oxygen vacancy engineering has been proven to be an effective control strategy in promoting photogenerated carrier separation and small molecule activation.

[0004] Loading metal co-catalysts is a common method to promote surface charge separation and regulate interfacial redox kinetics. When metal nanoparticles are integrated onto the semiconductor surface, the interface between them usually forms a Schottky junction or an Ohmic junction. The resulting interfacial electric field can significantly accelerate the separation of photoexcited carriers. More importantly, metal co-catalysts can also serve as highly active sites for a variety of reactions, improving the photocatalytic performance of semiconductors. 3 Heterostructures are beneficial for suppressing the recombination of photogenerated carriers, thereby achieving higher photocatalytic performance. For example, Kyoung-Suk Moon et al. (Materials Chemistry and Physics, 2024, 314, 128910) reported an Au-coated NiTiO 3 And applied to photocatalytic antibacterial, the report pointed out that they first used NiTi foil as a nickel source and titanium source in NH 4 NiTiO was obtained by electrodeposition in F electrolyte 3 The nanotubes were crystallized by high temperature calcination and then deposited on NiTiO 3 Au nanoparticles were deposited on the surface of nanotubes to obtain Au-coated NiTiO 3 The composite catalyst has high photocatalytic antibacterial performance. The co-catalyst Au used in the above report is a precious metal, which makes the catalyst modification cost high and is not conducive to large-scale application. 3Due to the huge difference in the crystal structure of the two, there will be a large charge transfer impedance at the interface between the two, which is not conducive to electron transfer and limits the improvement of photocatalytic activity. The cheap, readily available, highly conductive metal Ni has very little band overlap and is considered to be a viable substitute for precious metals, which has attracted widespread attention. More importantly, since the metal Ni and the Ni-containing compound contain the same element Ni, a strong coupling interface with low lattice mismatch can be formed between the metal Ni and the Ni-containing compound by sharing Ni atoms. This close atomic-level interface contact will simultaneously give the constructed metal / semiconductor system a more stable heterogeneous interface and an efficient interface charge transfer channel, which is crucial to improving photocatalytic performance. CN 109772338A discloses a defective Ni / NiTiO 3-x / C composite nanofiber membrane photocatalytic material. The invention first uses electrospinning technology to prepare a composite fiber membrane precursor, and then heat treats it under the protection of a hydrogen / argon mixed gas to obtain a defective Ni / NiTiO 3-x / C composite nanofiber film photocatalytic material. The material exhibits good photocatalytic degradation performance. However, the electrospinning technology used in the patent is high in cost, low in yield, complex in solution formulation, low in strength of electrospun nanofibers, high in cleanliness requirements for the production environment, and in the obtained Ni / NiTiO 3-x In the NiTiO / C composite material, the presence of a large amount of C increases the electron transfer interface, and the significant interface impedance limits the transmission of photogenerated charges, which is not conducive to the improvement of catalytic performance. More importantly, the NiTiO 3 The morphology of the matrix and the concentration of oxygen vacancies cannot be flexibly controlled, and it is difficult to fully explore the potential of NiTiO by synergistic morphology and defect engineering. 3 photocatalytic potential. Summary of the invention

[0005] The purpose of the present invention is to provide an oxygen-rich NiTiO 3 @Ni heterojunction photocatalyst and its preparation method and application. The catalyst is prepared by sol-gel method to synthesize NiTiO 3 As a precursor, NaBH 4 The invention is characterized in that, in NiTiO 3 The composite photocatalyst formed by in-situ anchoring of metal Ni nanoparticles on the surface can be applied to a photocatalytic synthesis of hydrogen peroxide system. The composite photocatalyst obtained by the invention has a highly efficient photocatalytic synthesis of hydrogen peroxide effect, and the preparation method is simple and easy.

[0006] To achieve the above object, the present invention adopts the following technical solution: A NiTiO with oxygen vacancy 3The preparation method of @Ni heterojunction photocatalyst specifically comprises the following steps: (1) Preparation of NiTiO 3 Precursor Nickel salt and titanium salt were dissolved in ethylene glycol according to the stoichiometric ratio, stirred at room temperature for reaction, and the precipitate was collected by centrifugation, dried and ground evenly, placed in a muffle furnace, heated to 600-800 °C, and kept warm to obtain NiTiO 3 Precursor; (2) Preparation of oxygen-vacancy-rich NiTiO 3 @Ni heterojunction photocatalyst The NiTiO obtained in step (1) 3 Precursor and NaBH 4 The mixture was uniformly mixed by grinding and placed in a tube furnace under N 2 or Ar protection, the temperature was raised to 300-500 °C, and the obtained product was naturally cooled to room temperature, dispersed in deionized water, centrifuged, washed and dried to obtain oxygen-rich NiTiO 3 @Ni heterojunction photocatalyst.

[0007] Preferably, the nickel salt in step (1) is selected from at least one of nickel acetate, nickel nitrate and nickel chloride.

[0008] Preferably, the titanium salt in step (1) is at least one selected from tetrabutyl titanate, titanium tetrachloride, and titanyl sulfate.

[0009] Preferably, the molar ratio of the nickel salt to the titanium salt in step (1) is 1:1.

[0010] Preferably, the stirring reaction time at room temperature in step (1) is 4 to 6 hours.

[0011] Preferably, the insulation time in step (1) is 3 to 5 hours.

[0012] Preferably, in step (2), NiTiO 3 Precursor and NaBH 4 The mass ratio is 1:(2~3).

[0013] Preferably, the insulation time in step (2) is 0.5 to 3 hours.

[0014] Further preferably, in step (2), NiTiO 3 Precursor and NaBH 4 The mass ratio of is 1:2.5 and the mixture is kept at 400 °C for 1 hour.

[0015] Oxygen vacancy-rich NiTiO prepared by the above preparation method 3 @Ni heterojunction photocatalyst.

[0016] The oxygen vacancy-rich NiTiO 3 @Application of Ni heterojunction photocatalyst in visible light photocatalytic synthesis of hydrogen peroxide.

[0017] Preferably, the application method is: dispersing an appropriate amount of photocatalyst in a mixed solution of oxygen-saturated benzyl alcohol and deionized water, using a 300 W xenon lamp equipped with a 420 nm cutoff filter as a light source, synthesizing hydrogen peroxide, and detecting the concentration of hydrogen peroxide by the DPD method.

[0018] In this application, NaBH 4 When the dosage or the temperature and holding time of thermal reduction are different, the photocatalytic synthesis of H 2 O 2 The activity is also different. When NaBH 4 The amount of NiTiO2 was 250 mg, the temperature of the thermal reduction process was 400 °C, and the holding time was 1 hour. 3 @Ni heterojunction photocatalyst has the best photocatalytic activity.

[0019] The significant advantage of the present invention is that the composite visible light photocatalyst of the present invention is composed of non-precious metal Ni and NiTiO 3 The raw materials are cheap and easy to obtain, the synthesis method is simple to operate, the requirements for preparation conditions are low, and it is easy to achieve mass production. 3 The obtained NiTiO 3 @Ni catalyst has a close interface at the atomic level, and the interfacial electron transfer is faster and more efficient. The in-situ synthesis method of the present invention can realize NiTiO 3 The substrate morphology, metal Ni and oxygen vacancy concentration can be controlled to give full play to the synergistic advantages of morphology control, heterogeneous structure and defect engineering. The metal Ni in the prepared catalyst is small in size and evenly distributed, exposing abundant reactive sites. Under visible light irradiation, the photocatalyst has excellent hydrogen peroxide synthesis performance and can be reused, with high use value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The pure NiTiO 3 、NiTiO 3 @XRD pattern of Ni heterojunction visible light catalyst; Figure 2 The NiTiO synthesized in Example 2 of the present invention 3 @TEM image of Ni heterojunction visible light catalyst; Figure 3 The NiTiO synthesized by the present invention 3@Ni heterojunction visible light catalyst and pure NiTiO 3 Room temperature EPR spectrum of Figure 4 The NiTiO synthesized by the present invention 3 @Ni heterojunction visible light catalyst and pure NiTiO 3 UV-Vis diffuse reflectance map; Figure 5 The NiTiO synthesized by the present invention 3 @Ni heterojunction visible light photocatalyst synthesis of hydrogen peroxide effect diagram and stability evaluation diagram; Figure 6 The NiTiO synthesized by the present invention 3 @Stability evaluation diagram of Ni heterojunction visible light photocatalyst for synthesizing hydrogen peroxide. DETAILED DESCRIPTION

[0021] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0022] Example 1 A NiTiO with oxygen vacancy 3 The preparation method of @Ni heterojunction photocatalyst comprises the following steps: (1) Ni(CH 3 COO 2 ·4H 2 O and Ti(OCH 2 CH 2 CH 2 CH 3 ) 4 Dissolve in 60 mL of ethylene glycol, stir at room temperature for 5 hours, collect the precipitate by centrifugation, dry it, grind it evenly, place it in a muffle furnace, heat it to 700 °C, and keep it for 4 hours to obtain NiTiO 3 Precursor.

[0023] (2) NiTiO prepared in step (1) 3 100 mg vs. 200 mg NaBH 4 The mixture was uniformly mixed by grinding and placed in a tube furnace under N 2 Under the protection of the reactor, the temperature was raised to 400 °C and kept for 1 hour. The obtained product was naturally cooled to room temperature, dispersed in deionized water, centrifuged, washed and dried to obtain oxygen-rich NiTiO 3 @Ni heterojunction photocatalyst, labeled as N-NTO-200.

[0024] Example 2 A NiTiO with oxygen vacancy 3 The method for preparing the @Ni heterojunction photocatalyst is different from that in Example 1 in that in step (1), NaBH 4 The amount of NiTiO2 was 250 mg. 3 @Ni heterojunction photocatalyst, labeled as N-NTO-250.

[0025] Example 3 A NiTiO with oxygen vacancy 3 The method for preparing the @Ni heterojunction photocatalyst is different from that in Example 1 in that in step (1), NaBH 4 The amount of NiTiO2 was 300 mg. 3 @Ni heterojunction photocatalyst, labeled as N-NTO-300.

[0026] Example 4 A NiTiO with oxygen vacancy 3 The method for preparing the @Ni heterojunction photocatalyst is different from that in Example 2 in that the heat treatment time in step (2) is 0.5 hours. 3 @Ni heterojunction photocatalyst, marked as 0.5N-NTO.

[0027] Example 5 A NiTiO with oxygen vacancy 3 The method for preparing the @Ni heterojunction photocatalyst is different from that in Example 2 in that the heat treatment time in step (2) is 2 hours. 3 @Ni heterojunction photocatalyst, labeled as 2N-NTO.

[0028] Example 6 A NiTiO with oxygen vacancy 3 The method for preparing the @Ni heterojunction photocatalyst is different from that in Example 2 in that the heat treatment time in step (2) is 3 hours. 3 @Ni heterojunction photocatalyst, labeled as 3N-NTO.

[0029] Comparative Example 1 A NiTiO with oxygen vacancy 3 The method for preparing the @Ni heterojunction photocatalyst is different from that in Example 2 in that the heat treatment time in step (2) is 4 hours. 3 @Ni heterojunction photocatalyst, labeled as 4N-NTO.

[0030] The catalyst synthesized by the method of Examples 1 to 3 and pure NiTiO 3 The X-ray powder diffractometer characterization results showed that the synthesized catalyst was NiTiO 3 @Ni heterojunction visible light catalyst, see attached Figure 1 .

[0031] The catalyst synthesized according to the method of Example 2 was observed by transmission electron microscopy. The results showed that in the synthesized photocatalyst, a large number of small-sized Ni nanoparticles were evenly distributed on the NiTiO 3 The surface size is about 5 nm, see Appendix Figure 2 .

[0032] The catalyst synthesized by the method of Examples 1 to 3 and pure NiTiO 3 The room temperature electron paramagnetic resonance (EPR) characterization results showed that the synthesized NiTiO 3 @Ni heterojunction visible light catalyst contains a large number of oxygen vacancies, and the concentration of oxygen vacancies can be changed by changing the NaBH 4 The amount of N-NTO-300 was adjusted, among which the N-NTO-300 sample had the most oxygen vacancies, see Appendix Figure 3 .

[0033] The catalysts synthesized according to the methods of Examples 1 to 3 were respectively mixed with pure NiTiO 3 The UV-visible diffuse reflectance analysis showed that the in-situ modification of oxygen vacancies and Ni nanoparticles can significantly improve the NiTiO 3 @Visible light absorption of Ni composite materials, see Appendix Figure 4 .

[0034] 5 mg of each catalyst prepared in Examples 1 to 3 was taken and dispersed in a mixed solution of 2 mL of benzyl alcohol and 18 mL of deionized water, and added to a reactor. Oxygen was bubbled for 30 minutes before the reaction. The hydrogen peroxide production was measured every hour under visible light with a wavelength greater than 420 nm. The DPD method was used for analysis, and the average hydrogen peroxide generation rate was calculated by the average method. See Appendix Figure 5 (A) By Figure 5 (A) It can be seen that NaBH 4 When the dosage is 250 mg, the prepared NiTiO 3 The Ni heterojunction catalyst has the highest visible light catalytic activity, with a hydrogen peroxide generation rate of 1280 μmol h -1 g -1 , is pure NiTiO 3 113 times.

[0035] 5 mg of each catalyst prepared in Examples 2, 4-6 and Comparative Example 1 were taken and dispersed in a mixed solution of 2 mL of benzyl alcohol and 18 mL of deionized water, and added to a reactor. Oxygen was bubbled for 30 minutes before the reaction. The hydrogen peroxide production was measured every hour under visible light with a wavelength greater than 420 nm. The DPD method was used for analysis, and the average hydrogen peroxide generation rate was calculated by the average method. See Appendix Figure 5 (B) By Figure 5 (B) It can be seen that the heat treatment time is 1 hour, and the prepared NiTiO rich in oxygen vacancies 3 @Ni heterojunction visible light photocatalyst has the highest catalytic activity.

[0036] 5 mg of the catalyst prepared in Example 2 was dispersed in a mixed solution of 2 mL of benzyl alcohol and 18 mL of deionized water, and added to a reactor. Oxygen was bubbled for 30 minutes before the reaction. The hydrogen peroxide production was observed every hour under visible light with a wavelength greater than 420 nm. The DPD method was used for analysis. The average hydrogen peroxide generation rate was calculated by the average method. See Appendix Figure 6 .Depend on Figure 6 It can be seen that the prepared NiTiO 3 @Ni heterojunction visible light catalyst has good stability.

[0037] The above is only a preferred embodiment of the present invention. It should be understood that those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Therefore, any technical solution that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst, characterized in that: The specific steps include: (1) Preparation of NiTiO3 precursor The nickel salt and titanium salt are dissolved in ethylene glycol according to the stoichiometric ratio, stirred at room temperature for reaction, and the precipitate is collected by centrifugation, dried and ground evenly, placed in a muffle furnace, heated to 600-800 °C, and kept warm to obtain a NiTiO3 precursor; (2) Preparation of NiTiO3@Ni heterojunction photocatalysts with oxygen vacancies The NiTiO3 precursor obtained in step (1) is mixed with NaBH4 by grinding and uniformly placed in a tube furnace, and heated to 300-500°C under N2 or Ar protection. The mixture is kept warm, and the obtained product is naturally cooled to room temperature, dispersed in deionized water, centrifuged, washed and dried to obtain an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst.

2. The method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 1, characterized in that: The nickel salt in step (1) is selected from at least one of nickel acetate, nickel chloride and nickel nitrate; preferably, the titanium salt in step (1) is selected from at least one of tetrabutyl titanate, titanium tetrachloride and titanyl sulfate.

3. The method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 1, characterized in that: The molar ratio of the nickel salt to the titanium salt in step (1) is 1:

1.

4. The method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 1, characterized in that: The stirring reaction time at room temperature in step (1) is 4 to 6 hours.

5. The method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 1, characterized in that: The insulation time in step (1) is 3 to 5 hours.

6. The method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 1, characterized in that: In step (2), the mass ratio of NiTiO3 precursor to NaBH4 is 1:(2~3).

7. The method for preparing an oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 1, characterized in that: The holding time in step (2) is 0.5 to 3 hours; preferably, the mass ratio of NiTiO3 precursor to NaBH4 in step (2) is 1:2.5, and the mixture is kept at 400°C for 1 hour.

8. An oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst according to claim 8 in the visible light catalytic synthesis of hydrogen peroxide.

10. The use of the oxygen vacancy-rich NiTiO3@Ni heterojunction photocatalyst in the visible light catalytic synthesis of hydrogen peroxide according to claim 9, characterized in that: An appropriate amount of photocatalyst was dispersed in a mixed solution of oxygen-saturated benzyl alcohol and deionized water. A 300 W xenon lamp equipped with a 420 nm cutoff filter was used as the light source to synthesize hydrogen peroxide. The concentration of hydrogen peroxide was detected by the DPD method.

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