阅读说明：本技术 氧化/还原-双助催化剂复合的CdS基多元光催化复合材料的制备方法及其产氢应用 (Preparation method of oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material and hydrogen production application thereof ) 是由 王舜 孙彬淑 刘爱丽 金辉乐 肖周敏 郑健宏 于 2020-05-08 设计创作，主要内容包括：本发明涉及一种氧化/还原-双助催化剂复合的CdS基多元光催化复合材料的制备方法及其产氢应用,所述的制备方法包括如下步骤：S1：含硫钼源为二甲基二硫代氨基甲酸钼；S2：配置四氯钯酸钠乙二醇溶液为钯源；S3：将所述含硫钼源和镉源前驱体加入到有机溶剂中,充分搅拌,混合均匀,得到前驱体反应液；S4：将所述前驱体反应液进行一步液相微波辅助法快速合成反应；S5：在S4的上述反应过程中,热注入作为钯源的四氯钯酸钠乙二醇溶液,从而得到双助催化剂复合的CdS基多元光催化复合材料。所述制备方法通过特定的工艺步骤与工艺参数的选择与组合,从而得到了具有优良制氢性能的CdS基多元光催化复合材料,可将其用于光解水制氢领域,具有良好的应用前景和工业化潜力。(The invention relates to a preparation method of an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material and hydrogen production application thereof, wherein the preparation method comprises the following steps: s1: the sulfur-containing molybdenum source is molybdenum dimethyldithiocarbamate; s2: preparing a sodium tetrachloropalladate glycol solution as a palladium source; s3: adding the sulfur-containing molybdenum source precursor and the cadmium source precursor into an organic solvent, fully stirring, and uniformly mixing to obtain a precursor reaction solution; s4: carrying out one-step liquid phase microwave-assisted rapid synthesis reaction on the precursor reaction solution; s5: in the reaction process of S4, sodium tetrachloropalladate glycol solution serving as a palladium source is injected in a hot manner, so that the double-promoter composite CdS-based multielement photocatalytic composite material is obtained. The preparation method obtains the CdS-based multielement photocatalytic composite material with excellent hydrogen production performance by selecting and combining specific process steps and process parameters, can be used in the field of hydrogen production through water photolysis, and has good application prospect and industrialization potential.)

1. A preparation method of an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material is characterized by comprising the following steps of:

s1: preparing molybdenum dimethyldithiocarbamate as a sulfur-containing molybdenum source;

s2: preparing a sodium tetrachloropalladate glycol solution as a palladium source;

s3: adding the sulfur-containing molybdenum source precursor and the cadmium source precursor into an organic solvent, fully stirring, and uniformly mixing to obtain a precursor reaction solution;

s4: carrying out one-step liquid phase microwave-assisted rapid synthesis reaction on the precursor reaction solution;

s5: in the reaction process of S4, sodium tetrachloropalladate glycol solution as a palladium source is injected in a hot manner, so that the CdS-based multielement photocatalytic composite material is obtained.

2. The method for preparing an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material as claimed in claim 1, characterized in that: the molybdenum dimethyldithiocarbamate in S1 is obtained by reacting molybdenum chloride, sodium ferbamate, and absolute ethanol, and in step S3, the cadmium source precursor is selected from any one or a mixture of any more of cadmium diethyldithiocarbamate, cadmium acetate, and dimethyl cadmium.

3. The method for preparing an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material as claimed in claim 1, characterized in that: in step S3, the organic solvent is C_1-6Alcohol, C_2-6Any one of glycol, N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone.

4. The method for preparing an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material as claimed in claim 1, characterized in that: in step S3, the mass ratio of the cadmium source precursor to the sulfur-containing molybdenum source is 2: 1.

5. The preparation method and the hydrogen production application of the oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material as claimed in claim 1 are characterized in that: the step S4 is specifically as follows: s4-1: setting a temperature-time program under the microwave power of ultrasonic stirring of 200W, heating the precursor reaction solution obtained in the step S3 from room temperature to 90 ℃, wherein the process needs 3-5 minutes, and keeping the temperature for 10 minutes to obtain a first reaction solution;

s4-2: and continuously heating the first reaction solution to 160 ℃, wherein the process needs 3-5 minutes, and keeping the temperature for 5 minutes to obtain a second reaction solution.

6. The method for preparing an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material as claimed in claim 7, characterized in that: the step S5 is specifically as follows:

s5-1: injecting a palladium source into the second reaction solution obtained in the step S4 at 160 ℃, and keeping stirring to obtain a third reaction solution;

s5-2: continuing to heat the third reaction solution at 160 ℃ for 5 minutes, and keeping stirring;

s5-3: naturally cooling the third reaction solution to room temperature, centrifuging for 5 minutes at the centrifugal speed of 18000 rpm, washing the obtained precipitate with absolute ethyl alcohol for 3-4 times in sequence, and then drying in vacuum to obtain the multi-component sulfide composite material.

7. An oxidation/reduction-double promoter compounded CdS-based multi-photocatalytic composite material as prepared by the method as claimed in any one of claims 1-8, wherein the CdS-based multi-photocatalytic composite material is marked as PdS-CdS-MoS₂。

8. Use of the oxidation/reduction-double cocatalyst-composited CdS-based multi-photocatalytic composite material according to claim 7 as a photocatalyst in the photolysis of water to produce hydrogen.

9. A method for producing hydrogen by photolysis comprises the following steps: the multi-component sulfide photocatalytic composite material according to claim 8 is added to a mixture of lactic acid and water, continuously irradiated with a 300W xenon lamp, filtered using a filter of 420nm or less, and photolyzed to obtain hydrogen.

10. The method of claim 9, wherein: in the photolytic hydrogen production method, the mass-to-volume ratio of the multi-component sulfide photocatalytic composite material to a mixture composed of lactic acid and water is 1:1-3 mg/mL.

Technical Field

The invention belongs to the field of inorganic semiconductor materials and energy materials, and particularly relates to a multi-component sulfide photocatalytic composite material, a preparation method thereof and hydrogen production application.

Background

The solar photocatalytic hydrogen production technology not only meets the effective utilization and conversion of solar energy, but also realizes the safe, clean and low-cost hydrogen preparation, thereby becoming one of important approaches for solving the environmental pollution and developing novel renewable energy sources. In the research of solar photocatalytic hydrogen production technology, it is most important to develop and create a novel and efficient photocatalytic hydrogen production system, find a novel visible light-driven photocatalyst with a special energy band structure, and improve the efficiency and stability of photocatalyst hydrogen production.

Among many visible light-responsive semiconductor photocatalyst materials, cadmium sulfide is paid much attention by scientists because of its typical II-VI direct band gap structure (band gap width is 2.40eV), high in solar energy utilization rate and oxidation-reduction potential closest to water decomposition, namely suitable valence band potential (1.50eV) and conduction band potential (-0.87eV vs NHE), satisfy the condition of hydrogen production by photolysis of water. The single-component semiconductor CdS is easy to generate a photo-corrosion phenomenon, namely after a certain illumination time, a CdS compound can generate a photo-decomposition phenomenon to decompose bivalent cadmium ions with toxicity, so that the photo-catalytic activity is reduced. On the other hand, the photo-generated electron-hole pairs on the single-component CdS are easy to recombine, so that the hydrogen production efficiency of photocatalytic hydrolysis is low. By controlling the appearance of the catalyst, doping metal ions or forming a heterojunction material by utilizing a composite cocatalyst, the efficiency of photocatalytic hydrolysis hydrogen production of CdS and the light corrosion resistance can be improved. Among them, a heterostructure formed by loading a cocatalyst on CdS is one of effective methods for reducing recombination of photo-generated electron-hole pairs. When the double promoters (the reduction type promoter and the oxidation type promoter) are compounded at the same time, the best photo-generated carrier separation effect can be achieved.

Two-dimensional molybdenum sulfide (MoS)₂) The catalyst is an excellent reduction type cocatalyst, and the surface of the catalyst has a plurality of exposed active centers, so that the catalyst has excellent optical performance and catalytic performance, and the photocatalytic reduction reaction is promoted. The band gap of palladium sulfide (PdS) is 1.60eV, the conduction band and the valence band are close to those of CdS, and the palladium sulfide has excellent optical properties. And PdS is an excellent oxidation type catalyst promoter, and can capture holes from the CdS catalyst, so that electron-hole pairs are better separated. CdS/MoS as described in CN103566953A and CN201610162861.9₂The composite material has good photocatalytic efficiency. CN201210370370.5 introduces the preparation of PdS/CdS composite material, and the prepared PdS/CdS nanocomposite material can be applied to the fields of visible light photocatalysis, photoelectric materials, hydrogen storage and the like.

CN201811245436.1 introduces that a microwave-assisted synthesis method is utilized to load a promoter MoS on CdS nano-particles₂、WS₂And the hydrogen production performance of the particle material obtained by the Pt nanocrystalline is obviously improved, and the superiority of loading multiple promoters on the CdS is also proved.

Disclosure of Invention

In order to solve the problems and the defects in the prior art, the invention aims to provide a preparation method of an oxidation/reduction-double-promoter compounded CdS-based multielement photocatalytic composite material and hydrogen production application thereof. The preparation method is simple, rapid, economic and environment-friendly, and the prepared multi-component sulfide photocatalytic composite material has the advantages of regularity and controllable morphology, and the application of the composite material in the field of photocatalysis is researched.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing an oxidation/reduction-double-promoter composited CdS-based multielement photocatalytic composite material, comprising the steps of:

s1: preparing molybdenum dimethyldithiocarbamate as a sulfur-containing molybdenum source;

s2: preparing a sodium tetrachloropalladate glycol solution as a palladium source;

s3: adding the sulfur-containing molybdenum source precursor and the cadmium source precursor into an organic solvent, fully stirring, and uniformly mixing to obtain a precursor reaction solution;

s4: carrying out one-step liquid phase microwave-assisted rapid synthesis reaction on the precursor reaction solution;

s5: in the above reaction process of S4, a sodium tetrachloropalladate glycol solution as a palladium source was thermally injected, thereby obtaining a multi-component sulfide photocatalytic composite material.

It is further provided that the molybdenum dimethyldithiocarbamate in S1 is obtained by reacting molybdenum chloride, sodium ferbamate and absolute ethanol. In the preparation method of the oxidation/reduction-double-promoter composite CdS-based multi-element photocatalytic composite material of the present invention, in step S1, the amount of ethanol used is not particularly limited, for example, the amount may be an amount that is easy to react and/or perform post-treatment, and those skilled in the art can make appropriate selections and determinations, and thus details are not repeated herein. In step S1, the reaction temperature is preferably room temperature.

It is further provided that in step S3, the cadmium source precursor is selected from any one or a mixture of any more of cadmium diethyldithiocarbamate, cadmium acetate, and cadmium dimethyl. Most preferred is cadmium diethyldithiocarbamate (CED).

It is further provided that in step S3, the organic solvent is C_1-6Alcohol, C_2-6Any one of glycol, N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone. Preferably a C2-6 diol, most preferably ethylene glycol.

In the preparation method of the oxidation/reduction-double-promoter compounded CdS-based multi-element photocatalytic composite material of the present invention, in step S3, the amount of the organic solvent used is not particularly limited, for example, may be an amount that is easy to react and/or perform post-treatment, and those skilled in the art can make appropriate selection and determination, and details are not repeated here.

It is further provided that in step S3, the mass ratio of the cadmium source precursor to the sulfur-containing molybdenum source is 2: 1.

It is further provided that in step S3, the stirring is: stirring at normal temperature for 40min, and performing ultrasonic treatment for 20 min.

It is further set that the step S4 is as follows:

s4-1: setting a temperature-time program under the microwave power of ultrasonic stirring of 200W, heating the precursor reaction solution obtained in the step S3 from room temperature to 90 ℃, wherein the process needs 3-5 minutes, and keeping the temperature for 10 minutes to obtain a first reaction solution;

s4-2: and continuously heating the first reaction solution to 160 ℃, wherein the process needs 3-5 minutes, and keeping the temperature for 5 minutes to obtain a second reaction solution.

It is further set that the step S5 is as follows:

s5-1: injecting a palladium source into the second reaction solution obtained in the step S4 at 160 ℃, and keeping stirring to obtain a third reaction solution;

s5-2: continuing to heat the third reaction solution at 160 ℃ for 5 minutes, and keeping stirring;

s5-3: and naturally cooling the third reaction solution to room temperature, centrifuging at the centrifugal speed of 18000 rpm for 5 minutes, washing the obtained precipitate with absolute ethyl alcohol for 3-4 times in sequence, and then drying in vacuum to obtain the CdS-based multielement photocatalytic composite material.

The inventor finds that when the preparation method is adopted, the CdS-based multielement photocatalytic composite material with specific appearance forms (both granular and flaky) can be obtained, and when certain process parameters such as raw material dosage ratio, microwave power, constant temperature time and the like are changed, the photocatalytic composite material with the forms cannot be obtained.

In addition, the invention also provides an oxidation/reduction-double-promoter compounded CdS-based multi-element photocatalytic composite material prepared by the method, and the CdS-based multi-element photocatalytic composite material is marked as PdS-CdS-MoS₂。

In addition, the invention also provides the application of the oxidation/reduction-double-promoter compounded CdS-based multi-element photocatalytic composite material as photocatalysis in hydrogen production by photolysis of water, and the oxidation/reduction-double-promoter compounded CdS-based multi-element photocatalytic composite material has good application prospect and industrialization potential.

The method specifically comprises the following steps: adding the CdS-based multi-element photocatalytic composite material into a mixture consisting of lactic acid and water, continuously irradiating by using a 300W xenon lamp, filtering by using an optical filter below 420nm, and photolyzing the water to obtain hydrogen.

The method is further characterized in that in the photolysis hydrogen production method, the mass-to-volume ratio of the CdS-based multi-element photocatalytic composite material to a mixture composed of lactic acid and water is 1:1-3 mg/mL. In the photolytic hydrogen production method, the volume ratio of the lactic acid to the water is 1:8-12, and may be, for example, 1:8, 1:9, 1:10, 1:11 or 1: 12.

The oxidation/reduction-double-promoter compounded CdS-based multi-element photocatalytic composite material has excellent photocatalytic hydrogen evolution efficiency, high-efficiency hydrogen evolution performance after continuous long-time reaction, high stability and capability of effectively solving the problems caused by photo-corrosion.

The inventor finds that the oxidation/reduction-double-promoter compounded CdS-based multi-element photocatalytic composite material obtained by the invention can prepare hydrogen by photolysis of water under the illumination condition, has very excellent hydrogen production performance and high stability, and effectively improves the problems caused by light corrosion. Provides a brand-new and high-efficiency photolysis composite material for photolysis hydrogen production, and has huge application potential and industrial value in the industrial field. See the example data for details.

Different from patent CN201811245436.1 are: in the material design, the patent specifically selects promoters with different functions, namely oxidized PdS and reduced MoS₂Rather than simply compounding the same type of promoter, separation of photogenerated carriers is more likely to be achieved; in addition, this patent is directed to synthesizing two-dimensional structures of MoS₂Amorphous nano-sheet, the obtained PdS-CdS particles are uniformly dispersed in MoS₂On nano-sheets, rather than agglomerated togetherThe particle structure increases the dispersity and the specific surface area of the catalyst to a certain extent, enhances the absorption and utilization of a light source, and simultaneously inhibits the recombination of a photon-generated carrier; in the synthesis method, the CdS-MoS is obtained by utilizing a microwave-assisted synthesis method₂After the heterojunction, the palladium source is injected at high temperature by combining a hot injection method, so that the PdS is prevented from independently nucleating in the previous synthesis, the PdS microcrystal is only loaded on the CdS particles, and simultaneously, the PdS microcrystal and the reduced MoS are simultaneously loaded₂The nanosheets are spatially separated; therefore, the catalyst promoter with different shapes and different functions, namely the reduction type catalyst promoter MoS, is loaded on the CdS at the same time₂When the catalyst is mixed with an oxidized cocatalyst PdS, a CdS-based multielement composite photolysis water catalyst with a multiple heterojunction structure is constructed, multiple synergistic effects are expected to be formed, the separation of photo-generated charges on space is achieved, the photocatalytic hydrolysis hydrogen production efficiency and stability driven by visible light are promoted, and PdS-CdS-MoS is formed₂The multielement photocatalytic composite material is a good way to improve the photocatalytic hydrogen production performance.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

FIG. 1 is a Scanning Electron Microscope (SEM) image of a CdS-based multi-element photocatalytic composite material compounded by oxidation/reduction-double promoters prepared in example 1 of the present invention;

FIG. 2 is a Transmission Electron Microscope (TEM) image (FIGS. 2a-2b), a local high resolution TEM image (FIG. 2c) and an elemental energy spectrum (EDS) image (FIGS. 2d-2h) of an oxidized/reduced-double promoted CdS-based multi-element photocatalytic composite material prepared in example 1 of the present invention;

FIG. 3 is an X-ray diffraction pattern (XRD) of a CdS-based multi-element photocatalytic composite material composited by oxidation/reduction-double promoters and prepared in example 1 of the present invention;

FIG. 4 is an X-ray photoelectron spectrum (XPS) of a CdS-based multi-element photocatalytic composite material composited by oxidation/reduction-double promoters and prepared in example 1 of the present invention;

FIG. 5 is a graph showing the diffuse reflection of ultraviolet light (FIG. 5a) and the fluorescence emission (FIG. 5b) of the oxidation/reduction-double-promoter composite CdS-based multi-element photocatalytic composite material prepared in example 1 of the present invention;

fig. 6 is a graph showing a comparison relationship between the irradiation time and the hydrogen production amount in the hydrogen production by photolysis of water between the oxidation/reduction-dual-promoter composite CdS-based multi-component photocatalytic composite material prepared in example 1 of the present invention and different components (fig. 6a), a comparison graph showing the hydrogen production of materials obtained at different heat injection temperatures (fig. 6b), a comparison graph showing the hydrogen production of composite materials with different PdS loading amounts (fig. 6c), and a 12-hour hydrogen production stability graph showing the multi-component sulfide photocatalytic composite material prepared in example 1 (fig. 6 d).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.