阅读说明：本技术 一种二维超薄CdS纳米片及其制备方法 (two-dimensional ultrathin CdS nanosheet and preparation method thereof ) 是由 柴波 刘纯 闫俊涛 范国枝 宋光森 程群鹏 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种二维超薄CdS纳米片及其制备方法。该制备方法包括：1)将氯化镉水溶液、硫粉、二乙烯三胺混合反应,产物经离心、干燥得到CdS前驱物；2)将CdS前驱物与L-半胱氨酸盐酸盐分散于水中得到混合溶液,超声剥离,得到剥离CdS的黄色溶液；3)将剥离CdS的黄色溶液分级离心,上清液减压抽滤,洗涤得到湿润黄色固体,分散在水中,得到二维超薄CdS纳米片的剥离溶液；4)冷冻干燥,得到所述二维超薄CdS纳米片。本发明制备二维超薄CdS纳米片的方法操作简便,所需实验装置简单,反应条件温和。制备的超薄CdS纳米片产物稳定,具有较强的化学稳定性和光响应特性,表现出了优良的光催化分解水产氢性能。(The invention discloses a two-dimensional ultrathin CdS nanosheet and a preparation method thereof. The preparation method comprises the following steps: 1) mixing and reacting a cadmium chloride aqueous solution, sulfur powder and diethylenetriamine, and centrifuging and drying a product to obtain a CdS precursor; 2) dispersing a CdS precursor and L-cysteine hydrochloride in water to obtain a mixed solution, and ultrasonically stripping to obtain a yellow CdS stripping solution; 3) carrying out fractional centrifugation on the CdS-stripped yellow solution, carrying out vacuum filtration on supernate, washing to obtain a wet yellow solid, and dispersing the wet yellow solid in water to obtain a two-dimensional ultrathin CdS nanosheet stripping solution; 4) and (5) freeze drying to obtain the two-dimensional ultrathin CdS nanosheet. The method for preparing the two-dimensional ultrathin CdS nanosheet is simple and convenient to operate, simple in required experimental device and mild in reaction condition. The prepared ultrathin CdS nanosheet product is stable, has strong chemical stability and photoresponse characteristic, and shows excellent hydrogen production performance by photocatalytic water decomposition.)

1. A preparation method of a two-dimensional ultrathin CdS nanosheet is characterized by comprising the following steps:

1) Mixing a cadmium chloride aqueous solution, sulfur powder and diethylenetriamine, reacting at 60-98 ℃, centrifuging, washing and drying a product to obtain a CdS precursor;

2) Dispersing a CdS precursor and L-cysteine hydrochloride in water to obtain a mixed solution, adjusting the pH value of the system to 9-11 by adopting an acid-base regulator, and then carrying out ultrasonic stripping on the mixed solution to obtain a yellow CdS stripping solution;

3) Carrying out fractional centrifugation on the CdS-stripped yellow solution, carrying out vacuum filtration on the supernatant obtained finally, washing to obtain a wet yellow solid, and dispersing the yellow solid in water to obtain a stripping solution of the two-dimensional ultrathin CdS nanosheet;

4) And (3) freeze-drying the stripping solution of the two-dimensional ultrathin CdS nanosheet to obtain the two-dimensional ultrathin CdS nanosheet.

2. The production method according to claim 1, wherein, in step 1),

The concentration of cadmium chloride in the cadmium chloride aqueous solution is 0.03-0.08 mol/L;

The molar ratio of the cadmium chloride to the sulfur powder is 1: 3-10;

The volume ratio of the water to the diethylenetriamine is 1: 4-6.

3. the preparation method according to claim 1, wherein the reaction time in step 1) is 3 to 24 hours.

4. the method according to claim 1, wherein the reaction is carried out under stirring at a constant temperature in step 1).

5. The production method according to claim 1, wherein, in the step 2),

The mass ratio of the CdS precursor to the L-cysteine hydrochloride is 1: 0.5-2;

The concentration of the CdS precursor in the mixed solution is 0.5-1 g/L.

6. The preparation method according to claim 1, wherein in the step 2), the time for ultrasonic peeling is 12h to 24 h.

7. the production method according to claim 1, wherein, in step 3), the step of fractional centrifugation comprises:

Carrying out first centrifugation on the CdS-stripped yellow solution at the rotating speed of 3000-4000 rpm, and separating to obtain a first supernatant;

Carrying out second centrifugation on the first supernatant at the rotating speed of 6000-8000 rpm, and separating to obtain a second supernatant;

And performing third centrifugation on the second supernatant at the rotating speed of 12000-15000 rpm, and separating to obtain the supernatant finally obtained.

8. The production method according to claim 7, wherein the time for the first centrifugation, the second centrifugation, and the third centrifugation is each 15min to 30 min.

9. the process according to claim 1, wherein in the step 3), the fraction having a particle size of 10nm or more is retained after vacuum filtration.

10. two-dimensional ultrathin CdS nanosheet prepared by the preparation method of any one of claims 1-9.

Technical Field

The invention belongs to the technical field of low-dimensional structure semiconductor materials, and particularly relates to a two-dimensional ultrathin CdS nanosheet and a preparation method thereof.

Background

the rapid development of industrial technology and the massive combustion of fossil fuels bring about not only environmental pollution but also energy shortage which is increasingly prominent in the current society, and thus the development and utilization of clean and efficient new energy is urgently needed. As an excellent energy form, the hydrogen is an ideal choice due to the characteristics of ultrahigh combustion value, no pollution and the like. In 1972, Japanese scholars Fujishima and Honda found that the illumination of titanium dioxide (TiO2) semiconductor electrodes leads to direct decomposition of water to generate hydrogen, and the feasibility of hydrogen production technology based on semiconductor photocatalytic decomposition of water is demonstrated.

cadmium sulfide (CdS) is a II-VI family direct band gap semiconductor material, has two crystal structures of cubic sphalerite and hexagonal wurtzite, has higher visible light absorption and photoreaction activity due to proper band gap width (2.4 eV), and has attracted wide attention in the field of solar energy hydrogen decomposition. However, CdS also has the disadvantages of strong photo-corrosivity, easy recombination of photo-generated electron-hole pairs, and the like, and these disadvantages reduce the reaction activity in the actual hydrogen production by photocatalytic decomposition of water with visible light, and greatly limit the practical application capability of the CdS because the performance of photocatalytic decomposition of water with hydrogen is poor.

disclosure of Invention

the invention aims to solve the problems and provides a preparation method of a two-dimensional ultrathin CdS nanosheet, which is simple to operate and mild in reaction conditions.

In order to achieve the above object, a first aspect of the present invention provides a preparation method of a two-dimensional ultrathin CdS nanosheet, the preparation method comprising:

1) Mixing a cadmium chloride aqueous solution, sulfur powder and diethylenetriamine, reacting at 60-98 ℃, centrifuging, washing and drying a product to obtain a CdS precursor;

2) Dispersing a CdS precursor and L-cysteine hydrochloride in water to obtain a mixed solution, adjusting the pH value of the system to 9-11 by adopting an acid-base regulator, and then carrying out ultrasonic stripping on the mixed solution to obtain a yellow CdS stripping solution;

3) Carrying out fractional centrifugation on the CdS-stripped yellow solution, carrying out vacuum filtration on the supernatant obtained finally, washing to obtain a wet yellow solid, and dispersing the yellow solid in water to obtain a stripping solution of the two-dimensional ultrathin CdS nanosheet;

4) and (3) freeze-drying the stripping solution of the two-dimensional ultrathin CdS nanosheet to obtain the two-dimensional ultrathin CdS nanosheet.

Preferably, in the step 1), the concentration of the cadmium chloride in the cadmium chloride aqueous solution is 0.03mol/L-0.08 mol/L.

Preferably, in the step 1), the molar ratio of the cadmium chloride to the sulfur powder is 1: 3-10.

Preferably, in the step 1), the volume ratio of the water to the diethylenetriamine is 1: 4-6.

Preferably, in the step 1), the reaction time is 3-24 h.

Preferably, in step 1), the reaction is carried out under constant temperature and stirring conditions to ensure sufficient contact between the substances in the system and a constant reaction rate.

Preferably, in the step 1), an environment with the temperature of 60-98 ℃ can be created through a water bath.

Preferably, in the step 1), the rotation speed of the centrifugation is 3000rpm-4000rpm, and the time is 5-10 min.

According to the invention, in step 1), washing can be carried out by means of water washing and alcohol washing. Optionally, after washing, drying at 75-85 deg.C, such as drying at 80 deg.C for 6 h.

Preferably, in the step 2), the mass ratio of the CdS precursor to the L-cysteine hydrochloride is 1: 0.5-2.

Preferably, in the step 2), the concentration of the CdS precursor in the mixed solution is 0.5-1 g/L.

Preferably, in step 2), the time for ultrasonic stripping is 12h to 24h to ensure that the desired target stripping degree is achieved.

according to the invention, in step 2), the pH value of the system can be adjusted to 9-11 by using an acid-base regulator which is conventionally used by a person skilled in the art. As a preferable scheme, ammonia water with low price is generally selected for adjustment.

preferably, in step 3), the step of fractional centrifugation comprises:

carrying out first centrifugation on the CdS-stripped yellow solution at the rotating speed of 3000-4000 rpm, and separating to obtain a first supernatant;

carrying out second centrifugation on the first supernatant at the rotating speed of 6000-8000 rpm, and separating to obtain a second supernatant;

and performing third centrifugation on the second supernatant at the rotating speed of 12000-15000 rpm, and separating to obtain the supernatant finally obtained.

Preferably, the time of the first centrifugation, the second centrifugation and the third centrifugation is 15min to 30min respectively.

Preferably, in the step 3), an ultrafiltration membrane with the pore diameter of 10nm is adopted for vacuum filtration. Specifically, an ultrafiltration membrane with the aperture of 10nm can be selected for vacuum filtration, and the yellow solid on the ultrafiltration membrane is cleaned by water suction filtration for 2-3 times, and finally the part with the particle size of more than or equal to 10nm is reserved to obtain the wet yellow solid.

Preferably, after the wet yellow solid is obtained in step 3), it is usually rapidly dispersed in water to avoid agglomeration and the like.

According to the invention, in the step 4), freeze drying is conventional experimental operation in the field, and the solid powder obtained after freeze drying is the two-dimensional ultrathin CdS nanosheet. Preferably, the freeze-drying time can be 40h-56 h.

According to the present invention, the water may be laboratory water conventionally used by those skilled in the art, including but not limited to deionized water, pure water, ultrapure water, and the like.

The second aspect of the invention provides the two-dimensional ultrathin CdS nanosheet prepared by the preparation method.

The invention has the beneficial effects that:

the two-dimensional ultrathin CdS nanosheet is bright yellow, the thickness of the two-dimensional ultrathin CdS nanosheet is about 1.5nm, and the yield of the stripped CdS nanosheet can reach 19.7%.

The method for preparing the two-dimensional ultrathin CdS nanosheet is simple and convenient to operate, simple in required experimental device and mild in reaction condition. The prepared ultrathin CdS nanosheet product is stable, has strong chemical stability and photoresponse characteristic, and shows excellent hydrogen production performance by photocatalytic water decomposition.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

drawings

FIG. 1 is an X-ray diffraction pattern of two-dimensional ultrathin CdS nanosheets and corresponding bulk CdS prepared in example 1;

FIG. 2 is a scanning electron micrograph of two-dimensional ultrathin CdS nanosheets prepared in example 1;

FIG. 3 is a transmission electron micrograph of two-dimensional ultrathin CdS nanosheets prepared in example 1;

FIG. 4 is an atomic force microscope photograph (a) of two-dimensional ultrathin CdS nanosheets prepared in example 1 and a thickness map (b) of the CdS nanosheets;

FIG. 5 is a graph of the UV-VIS absorption spectrum and a photograph of the two-dimensional ultra-thin CdS nanosheet aqueous solution dispersion newly prepared and after standing for 3 months in example 1;

FIG. 6 is an X-ray diffraction spectrum of the two-dimensional ultrathin CdS nanosheet prepared in example 2;

FIG. 7 is an X-ray diffraction spectrum of the two-dimensional ultrathin CdS nanosheet prepared in example 3;

FIG. 8 is an X-ray diffraction pattern of the two-dimensional ultrathin CdS nanosheet prepared in example 4;

FIG. 9 is an X-ray diffraction spectrum of the two-dimensional ultrathin CdS nanosheet prepared in example 5.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.