阅读说明：本技术 一例基于硫化镍量子点的复合光催化剂的制备方法及应用 (Preparation method and application of composite photocatalyst based on nickel sulfide quantum dots ) 是由 侯东芳 邓敏 黄磊 乔秀清 李东升 吴涛 于 2019-10-16 设计创作，主要内容包括：本发明公开了一例基于硫化镍量子点的复合光催化剂的制备方法及应用。本发明采用两步水热法,首先利用醋酸镉和硫脲为原料,通过水热法合成原始的硫化镉纳米微球,然后以氯化镍、柠檬酸钠和硫脲为原料,加入上步合成的硫化镉纳米微球,通过水热法得到硫化镉纳米微球表面负载硫化镍量子点的复合光催化剂。其中,通过控制硫化镍量子点原料的加入量,合成不同镍镉比的硫化镉/硫化镍复合材料(记为CdS/NiS<Sub>2</Sub>)。复合材料的合成实现了光生载流子的有效分离和迁移,并且改善了光催化剂的光稳定性,从而获得了优异的光催化性能。(The invention discloses a preparation method and application of a composite photocatalyst based on nickel sulfide quantum dots. The method adopts a two-step hydrothermal method, firstly cadmium acetate and thiourea are used as raw materials, the original cadmium sulfide nano-microsphere is synthesized by the hydrothermal method, then nickel chloride, sodium citrate and thiourea are used as raw materials, the cadmium sulfide nano-microsphere synthesized in the previous step is added, and the composite photocatalyst of the cadmium sulfide nano-microsphere with the surface loaded with the nickel sulfide quantum dots is obtained by the hydrothermal method. Wherein, cadmium sulfide/nickel sulfide composite materials (marked as CdS/NiS) with different nickel-cadmium ratios are synthesized by controlling the adding amount of nickel sulfide quantum dot raw materials 2 ). The synthesis of the composite material realizes the effective separation and migration of photon-generated carriers, and improves the light stability of the photocatalyst, thereby obtaining excellent photocatalytic performance.)

1. The preparation method of the composite photocatalyst based on the nickel sulfide quantum dots is characterized by comprising the following steps of:

(1) weighing cadmium acetate dihydrate and thiourea, adding the cadmium acetate dihydrate and the thiourea into water, stirring until the cadmium acetate dihydrate and the thiourea are uniformly dispersed, transferring the mixture into a lining of a polytetrafluoroethylene reaction kettle, heating the mixture in an oven to carry out hydrothermal reaction, and cooling, washing and drying the hydrothermal reaction product to obtain cadmium sulfide nano microspheres;

(2) weighing the cadmium sulfide nano microspheres prepared in the step (1), dispersing in water, adding nickel chloride hexahydrate, sodium citrate and thiourea under stirring, adjusting the pH of the dispersion to 10-12 by using ammonia water, continuously stirring to obtain uniform suspension, heating in an oven, cooling to room temperature, washing with pure water and ethanol for multiple times, and drying in a vacuum drying oven to obtain CdS/NiS₂A composite photocatalyst is provided.

2. The preparation method of the composite photocatalyst based on the nickel sulfide quantum dots, as claimed in claim 1, wherein the molar ratio of cadmium acetate to thiourea in the step (1) is 1: 1-10.

3. The preparation method of the composite photocatalyst based on the nickel sulfide quantum dots, as claimed in claim 1, wherein the nickel chloride, the sodium citrate and the thiourea are added in the step (2) in a molar ratio of 1: 1: 2-5.

4. The method for preparing the composite photocatalyst based on the nickel sulfide quantum dots, as claimed in claim 1, wherein the adding amount of the nickel source is 0.05 mmol-0.25 mmol, and the loading amount of the nickel sulfide is 12.5 mol% -42 mol%.

5. The application of the composite photocatalyst based on the nickel sulfide quantum dots prepared by any one of claims 1 to 4 in photocatalytic hydrogen production.

6. The application of the composite photocatalyst as claimed in claim 5, wherein the composite photocatalyst based on nickel sulfide quantum dots is dispersed in an aqueous solution of lactic acid under the irradiation of visible light, and photocatalytic hydrogen production is carried out under continuous stirring, wherein the lactic acid is used as a sacrificial agent for photocatalytic hydrogen production by water splitting.

7. The use of claim 6, wherein the composite photocatalyst based on nickel sulfide quantum dots is dispersed in an aqueous solution of lactic acid, and the content of lactic acid in the aqueous solution is 10 vol%.

Technical Field

The invention belongs to the field of nano material preparation technology and green energy application, and particularly relates to a preparation method of a supported nickel sulfide quantum dot matrix composite material and application of the supported nickel sulfide quantum dot matrix composite material in photocatalytic hydrogen production.

Background

The exhaustion of fossil energy and the pollution to the environment have attracted extensive attention of countries in the world, and the search for clean energy to replace traditional fossil energy has become an urgent problem to be solved. With the continuous development of the technology for converting solar energy into hydrogen energy, the hydrogen energy is pollution-free and has high energy density, the solar energy is inexhaustible, and the development of the solar hydrogen production photocatalyst with high efficiency and low cost by not using noble metals becomes the aim and direction of people's efforts, but is still a huge challenge so far. In particular, metal sulfides are considered to be ideal candidates for visible light catalysis due to their superior electrocatalytic effects in the electrolysis of water. The n-type semiconductor CdS with narrow forbidden band width of 2.4 eV has high activity in visible light and enough negative flat band potential to make H⁺Reduction to H₂Is a very attractive photocatalytic hydrogen evolution material. However, due to severe charge carrier recombination and photo-corrosion, the original CdS photocatalytic activity is still not ideal, and needs to be improved. The nickel sulfide is composed of elements rich in earth stock, is a cocatalyst material with great application prospect, and attracts people's extensive attention. The composite photocatalyst based on the nickel sulfide quantum dots can enrich photo-generated electrons and holes, can reduce the activation energy and overpotential of reaction, promote the reduction or oxidation reaction, promote the separation of the electrons and the holes at the interface of a cocatalyst/a semiconductor, and effectively inhibit the occurrence of photo-corrosion. Therefore, the nickel sulfide based composite material based on the quantum dot scale is not only beneficial to the rapid vector diffusion of photo-generated electrons, but also can promote H by reducing the thermodynamic overpotential of proton reduction₂The photocatalytic performance of the composite catalyst is obviously improved.

Disclosure of Invention

The invention aims to provide a preparation method of a composite photocatalyst based on nickel sulfide quantum dots, and the composite photocatalyst is applied to photocatalytic hydrogen production. By the synergistic effect of the nickel sulfide quantum dots, visible light absorption is enlarged, the separation and transportation efficiency of charge carriers is improved, and the energy barrier for water is reduced, so that the photocatalytic performance of cadmium sulfide is improved. In addition, the composite photocatalyst is simple in preparation method, relatively stable and excellent in photocatalytic hydrogen evolution activity.

The invention synthesizes a series of CdS/NiS with different proportions by taking cadmium sulfide and nickel sulfide quantum dots as candidate materials₂A nanocomposite material.

In order to achieve the above object, the technical solution adopted by the present discovery is:

the experiment adopts a two-step hydrothermal method to obtain CdS/NiS₂A composite nanomaterial. Firstly, synthesizing metal sulfide CdS by a one-step hydrothermal method, and then adding CdS nano-microspheres into NiS by adopting seed-mediated mild hydrothermal treatment₂Under the condition of quantum dot synthesis, NiS is subjected to hydrothermal method₂The quantum dots grow on the surface of the CdS microsphere, thereby obtaining the novel CdS/NiS₂The composite photocatalyst has a theoretical nickel sulfide loading of 12.5-42 mol%.

The CdS/NiS with excellent photocatalytic hydrogen production performance₂The preparation method of the nano composite material comprises the following steps:

(1) weighing cadmium acetate dihydrate and thiourea, dispersing in water, stirring to dissolve completely, transferring to 50 mL

Covering the inner liner of the polytetrafluoroethylene reaction kettle, sealing and heating for 12-48 h, centrifuging the product at high speed, taking supernatant, collecting for later use, wherein the cadmium sulfide is football-shaped nano microspheres with the size of about 150-200 nm.

(2) Weighing CdS powder obtained in the step (1), dispersing in water, performing ultrasonic treatment to obtain uniform suspension, and weighing

Taking nickel chloride hexahydrate, sodium citrate and thiourea (the molar ratio of the nickel chloride hexahydrate, the sodium citrate and the thiourea is 1: 1: 2-5), adjusting the pH of the solution to 10-12 by using 25-28% ammonia water, and continuously stirring the solution until the solution is uniform.

(3) Transferring the mixed solution obtained in the step (2) into a polytetrafluoroethylene reaction kettle lining, and putting the polytetrafluoroethylene reaction kettle lining into a drying oven

Heating for 12-48 h. Cooled to room temperature, washed with pure water and ethanol several times, and then dried in a vacuum drying oven, and the product was collected.

The invention also provides CdS/NiS₂A research method for applying the nano composite material to photocatalytic hydrogen production. The method comprises the following specific steps: a hydrogen production experiment was performed in a closed quartz reaction system under visible light irradiation, the temperature of the reaction system was maintained at 6 ℃ by cooling circulating water, a certain amount of catalyst was dispersed in an aqueous solution of lactic acid as a sacrificial agent, which was completely deaerated under continuous stirring, and hydrogen evolution analysis was performed by using an online gas chromatography (FULI, GC-7920) with a 300W xenon arc lamp of a 420 nm filter (CEL-HXF300) as a light source. The maximum photocatalytic hydrogen evolution rate reaches 27.49mmol g⁻¹h⁻¹。

The reaction mechanism is as follows: the technical scheme adopted by the invention adopts CdS nano-microspheres to load NiS₂The quantum dot composite material shows excellent catalytic activity in photocatalytic hydrogen production. NiS₂The quantum dots are crucial for improving the photocatalytic performance of the composite material. By NiS₂The synergistic effect of the quantum dots can enlarge the visible light absorption of the composite material and improve the separation and transportation efficiency of charge carriers, and the high dispersibility of the small quantum dot nanoclusters can fully improve the close contact between the two components, greatly shorten the transfer time and the migration distance of photon-generated carriers, remarkably improve the transmission and separation efficiency of the photon-generated carriers and promote the generation of hydrogen. Therefore, this work has made an important step towards the design of high performance, low cost photocatalytic materials for the conversion of solar energy to hydrogen energy.

Drawings

FIG. 1 is an X-ray diffraction diagram of CdS and composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 2 is a scanning electron microscope image of the composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 3 is a transmission electron microscope image of the composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 4 is a UV-visible diffuse reflectance spectrum of CdS and composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 5 is an infrared spectrum of CdS and composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 6 is a photo-current diagram of CdS and composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 7 is an AC-impedance diagram of CdS and composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

FIG. 8 is a histogram of hydrogen production performance of CdS catalyst and composite photocatalyst based on nickel sulfide quantum dots prepared in example 1.

Detailed Description

The invention is further described in the following detailed description with reference to specific embodiments, which are intended to be illustrative only and not to be limiting of the scope of the invention, as various equivalent modifications of the invention will become apparent to those skilled in the art after reading the present disclosure, and the scope of the invention is defined by the appended claims.