阅读说明：本技术 一种钒酸镧/石墨相氮化碳复合材料及其制备方法和应用 (Lanthanum vanadate/graphite phase carbon nitride composite material and preparation method and application thereof ) 是由 胡俊蝶 李雪 李长明 于 2021-07-20 设计创作，主要内容包括：本发明公开了一种钒酸镧/石墨相氮化碳复合材料和其制备方法,以及其作为光催化剂的应用。本发明涉及新能源功能材料技术领域。制备方法包括：制备石墨相氮化碳纳米片和钒酸镧纳米片；将钒酸镧纳米片与石墨相氮化碳混合研磨后煅烧,得到钒酸镧/石墨相氮化碳复合材料。本发明还公开了钒酸镧/石墨相氮化碳复合材料在光催化分解水制备氢气新能源协同生产糠醛的应用。本发明制备的钒酸镧/石墨相氮化碳复合材料合成步骤简单,具有优异的可见光响应性、高载流子迁移率和高比表面积,因此,该复合材料对可见光有很强的吸收能力,光催化产氢效率高,并且可有效利用光生空穴,将生物质材料糠醇氧化为高附加值产物糠醛,具有广泛应用前景。(The invention discloses a lanthanum vanadate/graphite phase carbon nitride composite material, a preparation method thereof and application thereof as a photocatalyst. The invention relates to the technical field of new energy functional materials. The preparation method comprises the following steps: preparing graphite-phase carbon nitride nanosheets and lanthanum vanadate nanosheets; mixing and grinding lanthanum vanadate nanosheets and graphite-phase carbon nitride, and calcining to obtain the lanthanum vanadate/graphite-phase carbon nitride composite material. The invention also discloses application of the lanthanum vanadate/graphite phase carbon nitride composite material in preparing hydrogen new energy by photocatalytic water decomposition and cooperatively producing furfural. The lanthanum vanadate/graphite phase carbon nitride composite material prepared by the invention has simple synthesis steps, excellent visible light responsiveness, high carrier mobility and high specific surface area, so the composite material has very strong absorption capacity on visible light, has high photocatalytic hydrogen production efficiency, can effectively utilize photoproduction holes to oxidize biomass material furfuryl alcohol into high value-added product furfural, and has wide application prospect.)

1. A preparation method of a lanthanum vanadate/graphite phase carbon nitride composite material is characterized by comprising the following steps:

(1) respectively preparing graphite-phase carbon nitride nanosheets and lanthanum vanadate nanosheets;

(2) mixing and grinding the graphite-phase carbon nitride nanosheets and the lanthanum vanadate nanosheets, and calcining in an inert gas atmosphere to obtain the lanthanum vanadate/graphite-phase carbon nitride nanocomposite.

2. The method for preparing lanthanum vanadate/graphite phase carbon nitride composite material according to claim 1, wherein a precursor for preparing the graphite phase carbon nitride nanosheets is selected from one or more of cyanamide, dicyandiamide, melamine, urea and thiourea.

3. The preparation method of the lanthanum vanadate/graphite-phase carbon nitride composite material according to claim 2, wherein the precursor is calcined at 200-550 ℃ for 2-5 h to obtain the graphite-phase carbon nitride nanosheet.

4. The method for preparing a lanthanum vanadate/graphite-phase carbon nitride composite material according to claim 1, wherein the lanthanum vanadate nanosheet is prepared by the following steps:

1) dissolving ammonium metavanadate in an alkaline solution, adding oleic acid and an organic solvent, adding a lanthanum nitrate aqueous solution, and fully mixing to form a precursor;

2) and reacting the precursor at 140-150 ℃ for 8-9 h to obtain the lanthanum vanadate nanosheet.

5. The method of claim 4, wherein the organic solvent is selected from one or more of ethanol, methanol, and cyclohexane.

6. The method for preparing lanthanum vanadate/graphite phase carbon nitride composite material according to claim 1, wherein in the step (2),

the mass ratio of the graphite-phase carbon nitride nanosheets to the lanthanum vanadate nanosheets is 75-95: 5-25;

the inert gas is argon and/or nitrogen.

7. The method for preparing a lanthanum vanadate/graphite phase carbon nitride composite material according to claim 1, wherein in the step (2), the calcination is performed under the condition of 200-500 ℃ for 1-5 h.

8. A lanthanum vanadate/graphite phase carbon nitride composite material prepared by the preparation method according to any one of claims 1 to 7.

9. The use of the lanthanum vanadate/graphite phase carbon nitride composite material according to claim 8 for preparing hydrogen by photocatalytic decomposition of water.

10. Use according to claim 9, wherein furfuryl alcohol is used as a hole scavenger to co-produce furfural.

Technical Field

The invention relates to the technical field of new energy functional materials, in particular to a preparation method of a lanthanum vanadate/graphite phase carbon nitride composite photocatalyst and application of the lanthanum vanadate/graphite phase carbon nitride composite photocatalyst in preparation of furfural chemicals by hydrogen new energy synergistic production through photocatalytic water decomposition.

Background

On one hand, with the improvement of living standard of people, the demand of energy is increasing day by day, but the world level energy consumption is mainly concentrated on fossil fuels such as coal, petroleum, natural gas and the like, and the fossil fuels are non-renewable and have strong pollution; on the other hand, due to excessive exploitation and development, fossil fuels are about to be exhausted globally, and there is an urgent need to build an effective catalytic system to realize a clean and sustainable energy technology.

The photocatalysis has the advantages of cleanness, environmental protection, high efficiency, economy, cyclic utilization and the like because the sunlight is used as a light source, and becomes a research hotspot. Photocatalytic hydrogen production materials are numerous, including graphite phase carbon nitride (g-C)₃N₄) Bismuth-based (BiOBr, Bi)₂WO₃Etc.), titanium dioxide (TiO)₂) Vanadates (BiVO)₄、LaVO₄) And the like. Graphite-phase carbon nitride has attracted wide attention due to its good catalytic activity, low cost, nontoxicity, abundant resources, easy preparation and other advantages, but graphite-phase carbon nitride has many disadvantages, such as narrow absorption range and weak absorption strength for visible light, fast recombination rate of photo-generated electrons and holes, low carrier mobility and the like, and greatly limits its ability to catalytically decompose water under the action of visible light. For this reason, the construction of a graphite-phase carbon nitride-based heterojunction has proven to be an effective strategy, since it allows the precise spatial tuning of the redox active sites, allowing a controlled manipulation of the oxidation and reduction half-reactions. Recently, two-dimensional lanthanum vanadate (LaVO) having high crystallinity₄) Nanoflakes have proven to be an attractive semiconductor, modulating reduction and oxidation sites through the directional transfer of photogenerated charges, which are potential candidates for photocatalytic hydrogen evolution.

At present, a hole scavenger is usually required to be added to improve the hydrogen precipitation efficiency in the preparation of hydrogen by photocatalytic water decomposition, and the method is expensive, wastes resources and does not accord with the green environmental protection concept. In response to this problem, it is an effective way to convert a hole scavenger into a valuable chemical by converting a hole sacrificial agent into a high value-added chemical by means of an oxidation half-reaction that decomposes water. In addition, biomass materials which are rich in content, cheap and easy to obtain are used as raw materials of the oxidation half reaction, so that the method has great significance for industrial production and clean new energy preparation.

Disclosure of Invention

In order to solve the technical problems, the invention provides a lanthanum vanadate/graphite phase carbon nitride composite material photocatalyst which is used for preparing hydrogen new energy by photocatalytic decomposition of water and cooperatively producing furfural chemicals. The composite material has strong absorption capacity on visible light due to excellent visible light responsiveness and high carrier mobility, the efficiency of catalyzing and decomposing water to produce hydrogen is high, meanwhile, the biomass material furfuryl alcohol is oxidized into furfural with high added value by the photoproduction cavity, and the problem of resource waste of the oxidation half reaction is solved.

The invention provides a preparation method of a lanthanum vanadate/graphite phase carbon nitride nanocomposite, which comprises the following steps:

(1) respectively preparing graphite-phase carbon nitride nanosheets and lanthanum vanadate nanosheets;

(2) grinding and mixing the graphite-phase carbon nitride nanosheets and the lanthanum vanadate nanosheets according to a certain proportion, and calcining again to synthesize the lanthanum vanadate/graphite-phase carbon nitride nanocomposite.

Preferably, the precursor for preparing the graphite phase carbon nitride nanosheets is selected from one or more of cyanamide, dicyandiamide, melamine, urea and thiourea.

And further, calcining the precursor at 200-550 ℃ for 2-5 h to obtain the graphite-phase carbon nitride nanosheet.

Further, the specific steps for preparing the lanthanum vanadate nanosheet are as follows:

1) dissolving ammonium metavanadate in an alkaline solution, adding oleic acid and an organic solvent, adding a lanthanum nitrate aqueous solution, and fully mixing to form a precursor;

2) and reacting the precursor at 140-150 ℃ for 8-9 h to obtain the lanthanum vanadate nanosheet.

Preferably, the organic solvent is selected from one or more of ethanol, methanol and cyclohexane.

Preferably, the alkaline solution is an aqueous NaOH solution.

Specifically, the preparation method of the lanthanum vanadate nanosheet comprises the following steps:

1) dissolving 0.5-1.5 g of NaOH in 3-10 mL of water, adding 0.01-0.08 g of ammonium metavanadate, dissolving the ammonium metavanadate in a beaker, sequentially adding 5-30 mL of oleic acid and 5-30 mL of ethanol in the beaker, finally adding 1-5 mL of lanthanum nitrate hexahydrate aqueous solution, and fully mixing to form a precursor;

2) and (3) putting the precursor into a reaction kettle, then putting the reaction kettle into an oven, and carrying out hydrothermal treatment for 5-10 h at 100-300 ℃. And after the hydrothermal method is finished, washing the lanthanum vanadate nanosheet with cyclohexane and ethanol for three times respectively, and drying the lanthanum vanadate nanosheet in vacuum at the temperature of 50-70 ℃ to obtain the lanthanum vanadate nanosheet.

Preferably, in the step (2), the mass ratio of the graphite-phase carbon nitride nanosheets to the lanthanum vanadate nanosheets is 75-95: 5-25.

Preferably, in step (2), the inert gas is argon and/or nitrogen.

Preferably, in the step (2), the calcination is performed under the condition of 200-500 ℃ for 1-5 h.

The invention also provides the lanthanum vanadate/graphite phase carbon nitride composite material prepared by the preparation method. According to the method, lanthanum vanadate nanosheets are successfully modified to the surface of graphite-phase carbon nitride, a perfect heterojunction structure is formed, and the method plays an important role in improving the efficiency of photocatalytic hydrogen production.

The method takes dicyandiamide as a raw material, the dicyandiamide is calcined twice in an oxygen environment to prepare graphite-phase carbon nitride nanosheets, lanthanum vanadate nanosheets are prepared by a hydrothermal method, and finally the smaller lanthanum vanadate nanosheets are modified to the surface of the graphite-phase carbon nitride by the calcination method under the action of intermolecular van der Waals force to form a perfect heterostructure. The introduction of lanthanum vanadate enhances the absorption capacity of the composite material to visible light, and the composite material has proper band gap and good conductivity, so that the recombination rate of photo-generated electrons and photo-generated holes is reduced, and the photocatalytic performance of graphite-phase carbon nitride is greatly improved.

The invention also provides application of the lanthanum vanadate/graphite phase carbon nitride composite material in photocatalytic decomposition of water to generate hydrogen, and furfuryl alcohol can be used as a hole scavenger to produce furfural.

The invention has the beneficial effects that:

1. the lanthanum vanadate/graphite phase carbon nitride composite material has the advantages of simple preparation method, easily obtained raw materials, simple and convenient operation and great key to industrial application;

2. according to the invention, the introduction of lanthanum vanadate can greatly improve the electron transmission efficiency, and can improve the absorption and utilization rate of graphite-phase carbon nitride to visible light, thereby improving the hydrogen production efficiency of photocatalytic water decomposition;

3. the lanthanum vanadate/graphite phase carbon nitride composite material is a photocatalyst with excellent performance, has high efficiency of photocatalytic decomposition of water to produce hydrogen and good stability, is beneficial to recovery and reutilization of the photocatalyst, and can be applied to photocatalytic production of clean energy;

4. the lanthanum vanadate/graphite phase carbon nitride composite material provided by the invention is used for photocatalytic splitting of water to produce hydrogen, and meanwhile, a traditional hole scavenger is replaced by furfuryl alcohol in an oxidation half reaction, and the furfuryl alcohol is oxidized into furfural by photoproduction of holes, so that the lanthanum vanadate/graphite phase carbon nitride composite material can be applied to medical and industrial production.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a Scanning Electron Micrograph (SEM) of graphite phase carbon nitride;

FIG. 2 is a Transmission Electron Micrograph (TEM) of graphite-phase carbon nitride;

FIG. 3 is a transmission electron micrograph of lanthanum vanadate;

FIG. 4 is a scanning electron micrograph of a lanthanum vanadate/graphite phase carbon nitride composite;

FIG. 5 is a transmission electron micrograph of a lanthanum vanadate/graphite phase carbon nitride composite;

FIG. 6 is a diagram showing the effect of photocatalytic water splitting for hydrogen production;

FIG. 7 is a diagram showing the effect of furfural production chemicals;

FIG. 8 is a diagram showing the effect of the cycle of photocatalytic water splitting to produce hydrogen.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Example 1

1. Preparation of graphite phase carbon nitride nanosheet

Adding 50mg of dicyandiamide into a crucible, putting the crucible into a muffle furnace, and setting the program to heat up the mixture from 20 ℃ to 550 ℃ at the heating rate of 5 ℃/min, keeping the temperature and calcining the mixture for 4 hours, grinding the graphite-phase carbon nitride obtained by the first firing, continuously calcining the ground graphite-phase carbon nitride for 2 hours under the same conditions, and naturally cooling the ground graphite-phase carbon nitride to obtain the graphite-phase carbon nitride nanosheet.

Fig. 1 and 2 are SEM and TEM images of graphite-phase carbon nitride, respectively, from which it can be observed that the prepared porous graphite-phase carbon nitride is uniform in size and has a thin sheet-like structure.

2. Preparation of lanthanum vanadate nanosheet material

Adding 5mL of deionized water and 0.6g of NaOH into a 25mL beaker, adding 0.06g of ammonium metavanadate after NaOH particles are dissolved, sequentially adding 10mL of oleic acid and 10mL of ethanol after the ammonium metavanadate is dissolved, finally adding 1mL of 1mmol/mL lanthanum nitrate hexahydrate aqueous solution, fully mixing, putting into a polytetrafluoroethylene reaction kettle with the volume of 25mL, putting the reaction kettle into an oven, and reacting for 8 hours at the temperature of 140 ℃. And after the hydrothermal method is finished, washing the obtained product with cyclohexane and absolute ethyl alcohol for three times respectively, and drying the product in vacuum at the temperature of 50-70 ℃ to obtain lanthanum vanadate nanosheets.

FIG. 3 is a TEM image of lanthanum vanadate, and it can be seen from the image that the lanthanum vanadate has a regular thin nano-sheet structure.

3. Preparation of lanthanum vanadate/graphite phase carbon nitride composite material

And putting 15mg of lanthanum vanadate nanosheets and 85mg of graphite-phase carbon nitride nanosheets into a mortar for grinding for 0.5h, putting the grinded material into a quartz boat, calcining at 450 ℃ in an argon environment, and reacting for 2h to obtain the lanthanum vanadate/graphite-phase carbon nitride composite material.

Fig. 4 and 5 are SEM and TEM images of the lanthanum vanadate/graphite-phase carbon nitride composite material, respectively, from which it can be clearly and intuitively seen that lanthanum vanadate nanosheets are successfully modified on the surface of graphite-phase carbon nitride sheets, forming a perfect heterojunction structure.

Example 2

20mg of the lanthanum vanadate/graphite phase carbon nitride composite material prepared in example 1 and 90mL of deionized water are uniformly mixed, put into a photocatalytic reactor, added with 10mL of triethanolamine, added with 1.86mL of 3% chloroplatinic acid hexahydrate, wrapped with tinfoil in a dark place, vacuumized for 0.5h, reacted, and introduced with condensed water to keep the water temperature at 15 ℃, and a xenon lamp light source is turned on to start a photocatalytic reaction.

FIG. 6 is a diagram showing the effect of a lanthanum vanadate/graphite phase carbon nitride composite material in photocatalytic decomposition of water to produce hydrogen. As can be seen from the figure, the efficiency of hydrogen production by photocatalytic hydrolysis of the lanthanum vanadate/graphite phase carbon nitride composite material is remarkably superior to that of a graphite phase carbon nitride material or a lanthanum vanadate nanosheet material, and the lanthanum vanadate/graphite phase carbon nitride composite material has good stability.

FIG. 7 is a diagram showing the effect of furfural production during the photocatalytic hydrolysis of lanthanum vanadate/graphite phase carbon nitride composite material to produce hydrogen under the condition of furfuryl alcohol as a hole scavenger. It can be seen from the figure that when furfuryl alcohol is used as a hole scavenger, the efficiency of hydrogen production by photocatalytic hydrolysis of the lanthanum vanadate/graphite-phase carbon nitride composite material is also significantly better than that of the graphite-phase carbon nitride material or lanthanum vanadate nano material, and the efficiency of furfural production is also significantly better than that of the graphite-phase carbon nitride material or lanthanum vanadate nano material.

FIG. 8 is a diagram showing the effect of a cycle experiment of preparing hydrogen by photocatalytic decomposition of water with a lanthanum vanadate/graphite phase carbon nitride composite material. As can be seen from the figure, the material has good recycling performance, and still has high hydrogen evolution effect after being used for four times, which indicates that the material has high potential industrial application value.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.