阅读说明：本技术 一种钼掺杂的氧化镓复合材料及其制备方法和应用 (Molybdenum-doped gallium oxide composite material and preparation method and application thereof ) 是由 沈锦妮 刘旭 夏种类 徐慧慧 钟玉华 于 2021-11-03 设计创作，主要内容包括：本发明属于光催化材料技术领域,具体涉及一种钼掺杂的氧化镓复合材料及其制备方法和应用。通过将(NH-(4))-(6)Mo-(7)O-(24)·4H-(2)O与Ga(NO-(3))-(3)·xH-(2)O混合,然后通过在氨水的碱性环境下进行搅拌,最后通过水热得到形貌为二维纳米片的Mo/Ga-(2)O-(3)复合材料。本发明通过简单水热合成了钼掺杂的氧化镓复合材料的光催化材料,制备原材料便宜易得,不含贵金属和污染环境的重金属,用于光解水制氢气具有优异的产氢速率,而氢气是高热能、无污染、可再生的能源。(The invention belongs to the technical field of photocatalytic materials, and particularly relates to a molybdenum-doped gallium oxide composite material and a preparation method and application thereof. By reacting (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O and Ga (NO) 3 ) 3 ·xH 2 O, stirring in an alkaline environment of ammonia water, and finally obtaining Mo/Ga with the shape of a two-dimensional nanosheet through hydrothermal method 2 O 3 A composite material. The photocatalytic material of the molybdenum-doped gallium oxide composite material is synthesized by simple hydrothermal method, the raw materials for preparation are cheap and easy to obtain, and the photocatalytic material does not contain noble metals and heavy metals polluting the environment, and has excellent hydrogen production rate when being used for preparing hydrogen by photolysis of water, and the hydrogen is high-heat energy, pollution-free and renewable energy.)

1. A preparation method of a molybdenum-doped gallium oxide composite material is characterized in that a molybdenum source is introduced into a precursor for synthesizing gallium oxide, and the molybdenum source and the precursor are subjected to hydrothermal reaction in an ammonia environment to obtain Mo/Ga₂O₃A composite material.

2. The method for preparing a molybdenum-doped gallium oxide composite material according to claim 1, comprising the following steps:

1) dissolving a certain amount of ammonium molybdate tetrahydrate and gallium nitrate hydrate in ammonia water, fully stirring and uniformly mixing to prepare a mixed solution;

2) placing the mixed solution in a hydrothermal reaction kettle for hydrothermal reaction, cooling, filtering, washing and drying to obtain Mo/Ga₂O₃。

3. The method of claim 2, wherein the mass ratio of ammonium molybdate tetrahydrate to gallium nitrate hydrate in step 1) is 1 ։ 20.

4. The method for preparing a molybdenum-doped gallium oxide composite material according to claim 2, wherein the volume of the ammonia water in step 1) is 80 mL, and the concentration of the ammonia water is as follows: 25-28 wt%.

5. The method for preparing a molybdenum-doped gallium oxide composite material according to claim 2, wherein the stirring time in step 1) is 30 min.

6. The method for preparing the molybdenum-doped gallium oxide composite material according to claim 2, wherein the hydrothermal temperature in the step 2) is 160 ℃ and the reaction time is 10 hours.

7. The method according to claim 2, wherein the drying process in step 2) is vacuum drying at a temperature of 60 ℃.

8. The molybdenum-doped gallium oxide composite material obtained by the preparation method according to any one of claims 1 to 7, wherein the molybdenum-doped gallium oxide composite material is in a two-dimensional nanosheet morphology, wherein the doping content of molybdenum is 5 wt%.

9. Use of the molybdenum-doped gallium oxide composite material of claim 8, as a photocatalyst in the photolysis of water to produce hydrogen.

Technical Field

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a molybdenum-doped gallium oxide composite material, a preparation method thereof and an effect on photocatalytic hydrogen production.

Background

The problems of energy consumption and environmental climate change in the world need to be solved urgently, and the development of clean energy is imperative. Hydrogen energy is considered one of the most promising and desirable energy sources for the future, not only because of its high energy density and calorific value, but most importantly its clean combustion products. However, today's industrial hydrogen production still relies heavily on non-renewable fossil fuels and the production of hydrogen in the process also releases large amounts of carbon dioxide and other harmful gases. The solar energy is considered to be a feasible method for solving global energy and environmental problems, particularly the method for decomposing water into hydrogen and oxygen under the action of light by using a semiconductor material as a photocatalyst has the advantages of cleanness, low cost and sustainability, and shows great potential. The key point is to find a proper and high-efficiency catalyst.

In the reaction process of semiconductor photocatalysis water decomposition, light irradiates on a catalyst, if the energy of photons is larger than the forbidden bandwidth of the photocatalyst, valence band electrons of a semiconductor material are excited by light to jump to a conduction band, meanwhile, holes are remained on the valence band, and then photo-generated electrons and the holes respectively migrate to the surface of the catalyst. In addition to this, if the semiconductor conduction band potential ratio H⁺/H₂(0V vs. NHE) reduction potential is more negative and the valence band potential is higher than H₂O/O₂Is corrected by the oxidation potential (1.23V), the strongly reducing electrons will convert H in water⁺Reduction to H₂The strong oxidizing cavity converts O in water^2- Oxidation to O₂. At present, a plurality of semiconductor materials can be used as photocatalysts, but most of the photocatalysts cannot produce hydrogen with high efficiency in a pure water system. Ga₂O₃Is a wide band gap semiconductor photocatalysis with very promising prospectThe material can be excited by ultraviolet light, has negative conduction band potential (-1.10 eV) and positive valence band potential (3.3 eV), has strong reducibility and oxidizability, and can theoretically carry out photocatalytic reaction on H₂Decomposition of O to H₂And O₂. But in practice Ga₂O₃The photocatalytic efficiency in a pure water system is yet to be further improved, and full water hydrolysis cannot be realized, which is caused by the low separation efficiency of electrons and holes.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a molybdenum-doped gallium oxide composite material, a preparation method thereof and an effect on photocatalytic hydrogen production. The preparation method has simple experimental conditions, mainly adopts hydrothermal method, does not involve substances polluting the environment in the preparation process, and has cheap and easily obtained raw materials. The product is a two-dimensional nano sheet, and the photocatalytic hydrogen production rate is obviously improved after the gallium oxide is doped with molybdenum.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a molybdenum-doped gallium oxide composite material for photocatalytic hydrogen production comprises the following steps:

1) a certain amount of (NH)₄)₆Mo₇O₂₄·4H₂O and Ga (NO)₃)₃·xH₂Dissolving O in ammonia water, and fully stirring to prepare a mixed solution;

2) carrying out hydrothermal reaction on the mixed solution, cooling, centrifuging, washing and drying to obtain Mo/Ga₂O₃A composite material;

said step 1) NH₄)₆Mo₇O₂₄·4H₂O and Ga (NO)₃)₃·xH₂The mass ratio of O is 1 ։ 20.

The volume of the ammonia water in the step 1) is 80 mL, the concentration of the ammonia water is 25wt% -28 wt%, and the stirring time is 30 min.

And 2) the hydrothermal temperature is 160 ℃, the reaction time is 10 h, and the drying treatment is vacuum drying at 60 ℃.

The molybdenum-doped gallium oxide composite material is in a two-dimensional nanosheet shape, wherein the doping content of molybdenum is 5 wt%.

The application comprises the following steps: the molybdenum-doped gallium oxide composite material is applied to the preparation of hydrogen by photolysis of water as a photocatalyst.

The present invention proposes (NH)₄)₆Mo₇O₂₄·4H₂O and Ga (NO)₃)₃·xH₂The mass ratio of O is 1 ։ 20, and the hydrogen production activity of the molybdenum-doped gallium oxide composite material obtained by a hydrothermal method under the condition of hydrothermal for 10 hours at 160 ℃ is optimal.

The photocatalytic activity of the photocatalytic material of the molybdenum-doped gallium oxide composite material was tested by photolysis of pure water under irradiation of an ultraviolet lamp.

The physical property characterization method of the photocatalytic material of the molybdenum-doped gallium oxide composite material comprises the following steps: the material composition and the structure condition of the product are analyzed by X-ray diffraction (XRD) spectrum, and the morphology of the product is observed by a Field Emission Scanning Electron Microscope (FESEM).

The invention has the advantages that: the experimental conditions of the scheme are simple and convenient, the method is mainly realized by hydrothermal, substances polluting the environment are not involved in the preparation process, and the raw materials are easy to obtain.

Compared with the prior art, the invention has the beneficial effects that:

the photocatalytic material of the molybdenum-doped gallium oxide composite material is synthesized by simple hydrothermal method, the raw materials for preparation are easy to obtain, the photocatalytic material does not contain noble metals and heavy metals polluting the environment, and the photocatalytic material has excellent hydrogen production activity when being used for preparing hydrogen by photolysis of water, and the hydrogen is high-heat energy, pollution-free and renewable energy.

The existence of Mo ions is favorable for accelerating electron migration, so that photo-generated electrons are transferred to the surface of the catalyst at a higher speed and undergo a reduction reaction with water to generate more hydrogen. In addition, compared to Ga of a single component₂O₃Ga doped with Mo₂O₃A certain amount of oxygen vacancies exist on the surface, and the oxygen vacancies can capture photo-generated electrons, play a role in separating electron hole pairs and reduce the recombination rate of photo-generated carriers. Thus, Mo-doped Ga₂O₃Having faster electron migrationThe shift rate and the higher electron separation efficiency, thereby greatly improving the hydrogen production rate.

Drawings

FIG. 1 shows Mo/Ga obtained by the synthesis method of example 1₂O₃XRD spectrum of the product.

FIG. 2 shows Mo/Ga obtained by the synthesis method of example 1₂O₃SEM photograph of nanoparticles.

FIG. 3 shows the effect of Mo doping on hydrogen production.

FIG. 4 shows the effect of hydrothermal reaction temperature on hydrogen production efficiency.

FIG. 5 is a graph showing the effect of hydrothermal reaction time on hydrogen production efficiency.

FIG. 6 shows Ga₂O₃And 5% Mo/Ga₂O₃Transient photocurrent response spectrum of (1).

FIG. 7 shows Ga₂O₃And 5% Mo/Ga₂O₃Electron paramagnetic resonance spectrum of (a).

FIG. 8 is a schematic view of a reactor for UV-catalyzed water splitting according to example 1.

FIG. 9 is a diagram of a photolytic reaction apparatus according to example 1.

Detailed Description

The invention is further illustrated by the following examples, which are intended to be illustrative only and not limiting.

Example 1

1.0228 g Ga (NO) were mixed under magnetic stirring₃)₃·xH₂O and 0.0511 g (NH)₄)₆Mo₇O₂₄·4H₂O was dissolved together in 80 mL of aqueous ammonia (25 wt%), and stirred for 30 min. Subsequently, the mixture was transferred to a stainless steel autoclave, sealed at 160 ℃ for 10 hours, and naturally cooled to room temperature. The precipitate was washed and dried in a vacuum oven at 60 ℃. Finally, 5% Mo/Ga is obtained₂O₃The target product of (1).

From Mo/Ga₂O₃XRD patterns of the nanoparticles (see FIG. 1) show that Mo/Ga synthesized by the method₂O₃Nanosheets having XRD pattern and Ga₂O₃Standard card completionThe alloy is completely coincident and does not contain other impurities, but the element content of Mo is less, so that the characteristic peak of the Mo element cannot be observed. From Mo/Ga₂O₃The SEM image (shown in figure 2) of the nano particles shows that the nano particles are uniform in morphology and are nano sheets with the thickness of 20 nm.

Example 2

Change only (NH)₄)₆Mo₇O₂₄·4H₂The amount of O added and the other preparation methods were the same as in example 1 to obtain Mo/Ga in which the Mo doping amounts were 1%, 3%, 7% and 9%, respectively₂O₃And (3) obtaining the product.

Example 3

Only the hydrothermal reaction temperature was changed to 120 deg.C, 140 deg.C, 180 deg.C, 200 deg.C, and the other preparation methods were the same as example 1 to obtain a series of products.

Example 4

Only the hydrothermal reaction time was changed, the hydrothermal reaction times were set to 5h and 15h, respectively, and the remaining preparation methods were the same as in example 1, to obtain a series of products.

The products of examples 1 to 4 were used in photocatalytic water splitting experiments to study the effects of Mo doping amount, hydrothermal reaction temperature and hydrothermal reaction time on hydrogen production activity, and the results are shown in fig. 3 to 5. As can be seen from the hydrogen production effect diagram (FIG. 3) of the obtained catalyst, Ga is obtained after Mo element is doped₂O₃The hydrogen production activity of the method is improved. (NH)₄)₆Mo₇O₂₄·4H₂O and Ga (NO)₃)₃·xH₂The optimal mass ratio of O is 1 ։ 20, the optimal hydrothermal temperature is 160 ℃, the optimal hydrothermal time is 10 h, the activity of the sample synthesized under the conditions is optimal, and the hydrogen production efficiency is 4.09 mmol/g^-1h^-1Is Ga₂O₃Single-component hydrogen production rate (1.6 mmol. g)^-1h^-1) More than 2 times of that of the Pt/Ga powder, and is 3wt% of Pt/Ga powder under the same condition₂O₃1.8 times of the total weight of the powder.

As can be seen from the results of the photocurrent response test (FIG. 6), the presence of Mo ions is beneficial to accelerating electron migration, so that photo-generated electrons are transferred to the surface of the catalyst at a faster rate and undergo a reduction reaction with water to generate more hydrogenAnd (4) qi. In addition, compared to Ga of a single component₂O₃Mo-doped Ga detected by electron paramagnetic resonance₂O₃And a certain amount of oxygen vacancies exist on the surface (figure 7), and the oxygen vacancies can capture photo-generated electrons, play a role in separating electron-hole pairs and reduce the recombination rate of photo-generated carriers. Thus, Mo-doped Ga₂O₃Has faster electron mobility and higher electron separation efficiency, thereby greatly improving the hydrogen production rate.

Application example 1

The experiment of photocatalytic water decomposition comprises the following specific steps:

the photocatalytic water splitting activity test of a series of prepared molybdenum-doped gallium oxide composite samples is carried out in a reaction device as shown in fig. 8, and the operation steps are as follows: 20 mg of the material catalyst was placed in the reactor, followed by 155 mL of deionized water.

The reactor was sealed with vacuum grease, connected to a photolysis water reaction system, and the system was subjected to vacuum treatment using circulating condensed water at 5 ℃ with the use of a reaction apparatus of fig. 9 until the system was maintained in a vacuum state for 30 min. And finally, irradiating for 180 min by using a 125W high-pressure mercury lamp light source, performing sampling once every 60 min, quantifying the intra-ring gas for mixing for 11 min, and detecting the hydrogen production of the reaction system by using FL9790 gas chromatography. The whole reaction process is carried out under the same stirring speed (500 r/s).

The above embodiments are preferred implementations of the present invention, and the present invention can be implemented in other ways without departing from the spirit of the present invention.