阅读说明：本技术 一种兼具光催化和光热转换性能的非晶氧化钼纳米点/二维氮化碳纳米片及其制备方法 (Amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet with photocatalysis and photothermal conversion performances and preparation method thereof ) 是由 任玉美 冯德胜 朱船辉 董潇翔 冯琛 于 2020-07-18 设计创作，主要内容包括：本发明提供一种兼具光催化和光热转换性能的非晶氧化钼纳米点/二维氮化碳纳米片及其制备方法。将本体氧化钼分散于乙醇水溶液中,然后将该分散液在冷水浴中超声,离心取上层分散液,然后将一定量的抗坏血酸加入到上层分散液中,冷水浴超声后即可得到非晶氧化钼纳米点；将三聚氰胺在空气气氛中进行煅烧,研磨得到本体氮化碳,然后再在空气气氛中煅烧即可得到类石墨相的二维氮化碳纳米片；将得到的非晶氧化钼纳米点与氮化碳纳米片按一定的质量比进行冷水浴超声混合即可得到非晶氧化钼纳米点/二维氮化碳纳米片复合材料。本发明提供了一种简单的超声化学法和热处理方法制备非晶氧化钼纳米点/二维氮化碳纳米片,原料便宜易得,有较好的应用前景。(The invention provides an amorphous molybdenum oxide nano-dot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion performances and a preparation method thereof. Dispersing the bulk molybdenum oxide in an ethanol water solution, then carrying out ultrasonic treatment on the dispersion liquid in a cold water bath, centrifuging to obtain an upper layer dispersion liquid, then adding a certain amount of ascorbic acid into the upper layer dispersion liquid, and carrying out ultrasonic treatment in the cold water bath to obtain amorphous molybdenum oxide nanodots; calcining melamine in air atmosphere, grinding to obtain bulk carbon nitride, and calcining in air atmosphere to obtain graphite-like two-dimensional carbon nitride nanosheets; and carrying out cold water bath ultrasonic mixing on the obtained amorphous molybdenum oxide nanodots and the carbon nitride nanosheets according to a certain mass ratio to obtain the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material. The invention provides a simple ultrasonic chemical method and a heat treatment method for preparing amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets, which have cheap and easily-obtained raw materials and good application prospect.)

1. A preparation method of amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets with both photocatalytic and photothermal conversion properties is characterized by comprising the following steps:

step one, preparing amorphous molybdenum oxide nanodots;

dispersing molybdenum oxide in an ethanol water solution to obtain a dispersion liquid, then carrying out ultrasonic treatment on the dispersion liquid in a cold water bath, carrying out centrifugal treatment on the dispersion liquid after ultrasonic treatment, and taking the upper-layer dispersion liquid into a container;

adding ascorbic acid into the upper-layer dispersion liquid to obtain a mixed liquid, and carrying out ultrasonic treatment on the mixed liquid in a cold water bath to obtain amorphous molybdenum oxide nanodots;

step two, preparing a graphite-like carbon nitride nanosheet;

calcining melamine, and grinding after calcining to obtain bulk carbon nitride; then calcining the bulk carbon nitride to obtain a graphite-like carbon nitride nanosheet;

step three, preparing an amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material;

and ultrasonically mixing the amorphous molybdenum oxide nanodots obtained in the step one and the carbon nitride nanosheets obtained in the step two in a cold water bath according to a certain mass ratio to obtain the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material.

2. The method for preparing the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets having both photocatalytic and photothermal conversion properties as claimed in claim 1, wherein in step one, the mass ratio of the molybdenum oxide to the volume ratio of the ethanol aqueous solution is 1g: (50-200) ml;

preferably, the volume percentage of the ethanol in the ethanol water solution is 10-90%.

3. The method for preparing amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets having both photocatalytic and photothermal conversion properties as claimed in claim 1, wherein in step one, the ratio of the mass of the ascorbic acid to the volume of the upper layer dispersion is 1g: (1-5) ml.

4. The method for preparing the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets having both photocatalytic and photothermal conversion properties as claimed in any one of claims 1 to 3, wherein in the first step, the temperature of the cold water bath is not higher than 25 ℃, and the ultrasonic time of ultrasonic treatment is 3-8 h;

preferably, in the step one, the centrifugal rotation speed of the centrifugal treatment is 3000-6000 rpm/min.

5. The method for preparing an amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet having both photocatalytic and photothermal conversion properties as claimed in claim 1, wherein in step two, the melamine calcination treatment is specifically performed for 2-5 hours in an air atmosphere at a temperature of 500-580 ℃.

6. The method for preparing the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets as claimed in claim 5, wherein the heating rate of the melamine during calcination is 2-5 ℃/min.

7. The method for preparing amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets as claimed in claim 1 or 5, wherein in step two, the calcination treatment of the bulk carbon nitride is specifically calcination at 500-550 ℃ in an air atmosphere for 2-5 h.

8. The method for preparing an amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet having both photocatalytic and photothermal conversion properties as claimed in claim 7, wherein the rate of temperature rise during calcination of the bulk carbon nitride is 2-5 ℃/min.

9. The method for preparing the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets having both photocatalytic and photothermal conversion properties as claimed in claim 1, wherein in step three, the amorphous molybdenum oxide nanodots account for 5-20% by mass of the carbon nitride nanosheets;

preferably, in the third step, the time for ultrasonically mixing the amorphous molybdenum oxide nanodots and the carbon nitride nanosheets in the cold water bath is 2 h.

10. The amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets prepared by the method for preparing the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets having both photocatalytic and photothermal conversion properties as claimed in any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of nano materials, and particularly relates to an amorphous molybdenum oxide nano-dot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion properties and a preparation method thereof.

Background

With the rapid development of global economy, environmental problems and energy crisis become important problems facing mankind in the new century. Solar energy, as a clean renewable energy source, is one of the most promising alternative energy sources by using sunlight with abundant resources as an energy source, and has become the focus of energy conversion and utilization in recent years, and has been widely applied to the fields of photovoltaic power generation, photocatalysis, photothermal conversion and the like. The solar energy can be converted into hydrogen energy which can be stored and transported by photocatalysis, and seawater can be desalinated by solar energy through photothermal effect, which is helpful for relieving the problems of energy shortage, environmental pollution, shortage of fresh water resources and the like. How to prepare a novel high-efficiency light energy conversion material and improve the energy conversion efficiency of the material is a key subject in the field of solar energy conversion at present.

Molybdenum oxide can exhibit localized plasmon resonance (LSPR) properties due to the presence of its extra-nuclear d-orbital electrons, and its surface free electron concentration has a close relationship with oxygen holes. Molybdenum oxides with different stoichiometries and different crystal structures can be obtained by introducing different oxygen vacancy concentrations, and the molybdenum oxides are widely applied to the fields of catalysis, photothermal conversion, energy storage, electronic devices and the like. And the amorphous molybdenum oxide nanodots can show a remarkably enhanced LSPR effect due to abundant surface defects and active sites. Among numerous semiconductor nano materials, the graphite-like carbon nitride has a very suitable semiconductor band edge position, a forbidden band width of 2.7 eV, meets the thermodynamic requirements of hydrogen production and oxygen production by photolysis of water, has the characteristics of excellent surface functionalization modification, high physicochemical stability, no toxicity, rich raw materials and the like, and is widely concerned. The amorphous molybdenum oxide nano-dots have high surface activity and are easy to agglomerate, and the normally prepared carbon nitride photogenerated electron-hole recombination rate is high, so that the excellent characteristics of the amorphous molybdenum oxide nano-dots and the carbon nitride nano-sheet composite material can be fully exerted, the transmission and separation of charge carriers are promoted, the surface chemical reaction rate of a system is improved, the light absorption capacity is improved, and the catalytic reaction activity and the photothermal conversion performance of the system are improved. However, it is still a challenge to find a simple and efficient preparation technique.

Disclosure of Invention

The invention aims to provide a preparation method of amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets with photocatalysis and photothermal conversion performances, which has the advantages of cheap and easily-obtained raw materials, simple operation process and large-scale preparation.

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

a preparation method of amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets with both photocatalytic and photothermal conversion properties comprises the following steps:

step one, preparing amorphous molybdenum oxide nanodots;

dispersing molybdenum oxide in an ethanol water solution to obtain a dispersion liquid, then carrying out ultrasonic treatment on the dispersion liquid in a cold water bath, carrying out centrifugal treatment on the dispersion liquid after ultrasonic treatment, and taking the upper-layer dispersion liquid into a container;

adding ascorbic acid into the upper-layer dispersion liquid to obtain a mixed liquid, and carrying out ultrasonic treatment on the mixed liquid in a cold water bath to obtain amorphous molybdenum oxide nanodots;

step two, preparing a graphite-like carbon nitride nanosheet;

calcining melamine, and grinding after calcining to obtain bulk carbon nitride; then calcining the bulk carbon nitride to obtain a graphite-like carbon nitride nanosheet;

step three, preparing an amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material;

and ultrasonically mixing the amorphous molybdenum oxide nanodots obtained in the step one and the carbon nitride nanosheets obtained in the step two in a cold water bath according to a certain mass ratio to obtain the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material.

In the preparation method of the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets with both photocatalytic and photothermal conversion performances, preferably, in the first step, the volume ratio of the mass of the molybdenum oxide to the ethanol aqueous solution is 1g: (50-200) ml;

preferably, the volume percentage of the ethanol in the ethanol water solution is 10-90%.

In the preparation method of the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets having both photocatalytic and photothermal conversion properties as described above, preferably, in the first step, the ratio of the mass of the ascorbic acid to the volume of the upper layer dispersion is 1g: (1-5) ml.

In the preparation method of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion performances, preferably, in the first step, the temperature of the cold water bath is not higher than 25 ℃, and the ultrasonic time of ultrasonic treatment is 3-8 h;

preferably, in the step one, the centrifugal rotation speed of the centrifugal treatment is 3000-6000 rpm/min.

In the preparation method of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion performances, preferably, in the second step, the melamine is calcined in an air atmosphere at 500-580 ℃ for 2-5 hours.

In the preparation method of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion performances, preferably, the heating rate of the melamine during calcination is 2-5 ℃/min.

In the preparation method of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet having both photocatalytic and photothermal conversion properties, preferably, in the second step, the calcination treatment of the bulk carbon nitride is specifically calcination in an air atmosphere at 500-550 ℃ for 2-5 hours.

In the preparation method of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion performances, preferably, the temperature rise rate of the bulk carbon nitride during calcination is 2-5 ℃/min.

In the preparation method of the amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets with both photocatalytic and photothermal conversion performances, preferably, in the third step, the amorphous molybdenum oxide nanodots account for 5-20% of the carbon nitride nanosheets by mass;

preferably, in the third step, the time for ultrasonically mixing the amorphous molybdenum oxide nanodots and the carbon nitride nanosheets in the cold water bath is 2 h.

An amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet prepared by the preparation method of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet with both photocatalytic and photothermal conversion performances.

Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:

the invention uses inorganic materials with rich resources to replace traditional noble metals and the like as photo-thermal reagents and catalysts, solves the problems of low absorption coefficient and expensive price of the conventional materials at present, and can realize large-scale preparation. The preparation method is simple and easy to implement, the raw materials are cheap and easy to obtain, and meanwhile, the introduction of the amorphous structure and the construction of the heterostructure effectively regulate the electronic structure of the material, so that the amorphous structure has good application prospects in the fields of optical, electric and thermal functional materials.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:

FIG. 1: a transmission electron microscope image of the amorphous molybdenum oxide nanodots subjected to ultrasonic treatment and ascorbic acid reduction in example 1 of the present invention;

FIG. 2: a transmission electron microscope image of the carbon nitride nanosheet after heat treatment in example 1 of the present invention;

FIG. 3: the transmission electron microscope image of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material subjected to ultrasonic mixing in the embodiment 1 of the invention;

FIG. 4: the photocatalytic performance effect diagram of the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material subjected to ultrasonic mixing in the embodiment 1 of the invention;

FIG. 5: embodiment 1 of the invention provides a photo-thermal response effect diagram of an amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material after ultrasonic mixing.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

The present invention will be described in detail with reference to examples. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material with both photocatalytic and photothermal conversion performances provided by the invention realizes effective stripping of molybdenum oxide under the action of molybdenum oxide and ethanol aqueous solution, and ascorbic acid is used as a reducing agent under the action of ultrasonic chemistry, so that hydrogen radicals can be effectively generated to enter the crystal lattice of the molybdenum oxide, and the formation of the amorphous molybdenum oxide nanodot is induced. In the air atmosphere, the two-dimensional carbon nitride nanosheet can be prepared by adopting a thermal polymerization method and taking melamine as a precursor, and the amorphous material with the atomic structure of disordered long-range and ordered short-range has abundant surface defects and active sites, so that the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material can be obtained by further ultrasonic mixing treatment.

The invention provides a preparation method of amorphous molybdenum oxide nanodots/two-dimensional carbon nitride nanosheets with both photocatalytic and photothermal conversion performances, which comprises the following steps:

step one, preparing amorphous molybdenum oxide nanodots;

dispersing molybdenum oxide in an ethanol water solution to obtain a dispersion liquid, then carrying out ultrasonic treatment on the dispersion liquid in a cold water bath, carrying out centrifugal treatment on the dispersion liquid after ultrasonic treatment, and taking the upper-layer dispersion liquid into a container;

adding ascorbic acid into the upper-layer dispersion liquid to obtain a mixed liquid, and carrying out ultrasonic treatment on the mixed liquid in a cold water bath to obtain the amorphous molybdenum oxide nanodots.

In the specific embodiment of the invention, the volume ratio of the mass of the molybdenum oxide to the volume of the ethanol aqueous solution is 1g: (50-200) ml (for example, 1g: 50 ml, 1g: 60 ml, 1g: 70 ml, 1g: 80 ml, 1g: 90 ml, 1g: 100 ml, 1g: 110 ml, 1g: 120 ml, 1g: 130 ml, 1g: 140 ml, 1g: 150 ml, 1g: 160 ml, 1g: 170 ml, 1g: 180 ml, 1g: 190 ml, 1g: 200 ml).

Preferably, the ethanol in the ethanol aqueous solution is 10-90% (e.g., 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%) by volume, and more preferably, the ethanol is 50% by volume.

In a specific example of the present invention, the ratio of the mass of ascorbic acid to the volume of the upper dispersion was 1g: (1-5) ml (for example, 1g: 1.5 ml, 1g: 2 ml, 1g: 2.5 ml, 1g: 3ml, 1g: 3.5 ml, 1g: 4 ml, 1g: 4.5 ml, 1g:5 ml).

In the specific embodiment of the invention, the temperature of the cold water bath is not higher than 25 ℃, and the ultrasonic time of ultrasonic treatment is 3-8 h (such as 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h and 8 h); preferably, in the step one, the centrifugal rotation speed of the centrifugal treatment is 3000-6000 rpm/min (3500 rpm/min, 4000 rpm/min, 4500 rpm/min, 5000rpm/min, 5500 rpm/min).

Step two, preparing a graphite-like carbon nitride nanosheet;

calcining melamine, and grinding after calcining to obtain bulk carbon nitride; and then calcining the bulk carbon nitride to obtain the graphite-like carbon nitride nanosheet.

In the specific embodiment of the present invention, the melamine calcination treatment is specifically performed by calcining the melamine in an air atmosphere at a temperature of 500 to 580 ℃ (e.g., 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃, 560 ℃, 570 ℃) for 2 to 5 hours (e.g., 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 4.8 hours). Preferably, the heating rate of the melamine during calcination is 2-5 ℃/min (such as 2.5 ℃/min, 3 ℃/min, 3.5 ℃/min, 4 ℃/min, 4.5 ℃/min, 5 ℃/min).

In an embodiment of the present invention, the calcination treatment of the bulk carbon nitride is specifically calcination in an air atmosphere at 500 to 550 ℃ (e.g., 505 ℃, 510 ℃, 515 ℃, 520 ℃, 525 ℃, 530 ℃, 535 ℃, 540 ℃, 545 ℃ and 550 ℃) for 2 to 5 hours (e.g., 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours and 4.8 hours). Preferably, the temperature rise rate during the calcination of the bulk carbon nitride is 2-5 ℃/min (such as 2.5 ℃/min, 3 ℃/min, 3.5 ℃/min, 4 ℃/min, 4.5 ℃/min, 5 ℃/min).

Step three, preparing an amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material;

and ultrasonically mixing the amorphous molybdenum oxide nanodots obtained in the step one and the carbon nitride nanosheets obtained in the step two in a cold water bath according to a certain mass ratio to obtain the amorphous molybdenum oxide nanodot/two-dimensional carbon nitride nanosheet composite material.

In a specific embodiment of the present invention, the amorphous molybdenum oxide nanodots account for 5-20% by mass (e.g., 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%) of the carbon nitride nanosheets.

In a specific embodiment of the invention, the time for ultrasonic mixing of the amorphous molybdenum oxide nanodots and the carbon nitride nanosheets in the cold water bath is 2 hours.

Molybdenum oxide (referred to as Molybdenum (VI) oxide, MoO for short) used in the following examples of the present invention₃) Purchased from Alfa Aesar. Melamine and ascorbic acid were purchased from the national pharmaceutical group chemical agents limited.