Sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst as well as a preparation method and application thereof, and belongs to the technical field of photocatalytic hydrogen production. The photocatalyst comprises a Cd0. 7Zn0. 3S solid solution and MoS2 loaded on the surface of the Cd0. 7Zn0. 3S solid solution In the photocatalyst, the content of MoS2 is 5-40 wt%. According to the invention, a MoS2 two-dimensional co-catalysis layer is constructed on the surface of Cd0. 7Zn0. 3S by adopting a one-step hydrothermal method, the MoS2 two-dimensional co-catalysis layer and the Cd0. 7Zn0. 3S are promoted to form tight interface contact and Schottky junction, and the strong interface coupling effect is utilized to enhance interaction force and accelerate photogenerated charge transfer, so that the MoS2 two-dimensional co-catalysis layer has high activity and low cost, and can fully utilize solar energy to drive a photocatalytic reaction; the solar energy conversion efficiency is greatly improved, a feasible solution is provided for a high-efficiency and stable photocatalytic hydrogen production technology, and the method has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic hydrogen production, and particularly relates to a sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst as well as a preparation method and application thereof. BACKGROUND

[0002] Under the background of global economic sustainable development, energy demand is showing a rapid growth trend. Traditional fossil energy (including coal, oil and natural gas, etc.) has been exploited on a large scale for a long time, and its reserves are facing the severe situation of exhaustion. This energy structure mainly has two major problems: first, the non-renewable nature of fossil energy leads to a continuous decrease in resource reserves, and energy supply security faces major challenges; second, a large amount of greenhouse gases and harmful pollutants are produced in the combustion process of fossil fuels, which not only aggravates global climate change, but also causes serious environmental pollution. These problems have become an important bottleneck restricting the sustainable development of economy and society.

[0003] Hydrogen energy, as a promising clean energy solution, has attracted much attention. This energy form has the following advantages: first, hydrogen is abundant on earth, mainly in the form of water, which can be produced on a large scale through water electrolysis and other technologies; second, hydrogen energy is completely clean, and its combustion product is only water, truly achieving zero carbon and zero pollutant emissions; third, hydrogen energy has a very high energy density, about 3 times that of gasoline, which can provide more efficient and longer-lasting energy supply for various power equipment; finally, hydrogen energy has wide application adaptability and can be widely used in transportation, power generation, industrial manufacturing and other fields. Based on these advantages, hydrogen energy technology is expected to become a key breakthrough to solve the current energy and environmental dilemma, and provide important support for building a clean, low-carbon, safe and efficient modern energy system.

[0004] Since Fujishima and Honda first reported the photoelectrochemical water splitting phenomenon of TiO2 electrode in 1972, semiconductor materials have been continuously concerned in the field of artificial photocatalytic water splitting due to their unique photoelectric properties. However, existing photocatalysts still face key bottlenecks such as low quantum efficiency and high cost-effectiveness ratio, which seriously restrict their industrial application. Sulfur-zinc-cadmium solid solution (CdZnS) is a kind of metal sulfide semiconductor photocatalyst, which has attracted much attention due to its adjustable band gap structure, excellent light absorption performance and high efficient charge separation efficiency. Although CdZnS has adjustable band gap structure, excellent light absorption performance and high efficient charge separation efficiency, it still has problems as a single photocatalyst, such as high intrinsic carrier recombination rate, limited light absorption range and slow surface reaction kinetics. Therefore, it is crucial to build a composite system to improve its charge separation efficiency and surface reaction activity. SUMMARY

[0005] To solve the above problems in the prior art, the application provides a sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst, a preparation method and application thereof.

[0006] To achieve the above object, the application provides the following technical scheme. The application provides a sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst. 0.7 Zn 0.3 S solid solution and two-dimensional sheet MoS2 loaded on the surface; in the photocatalyst, the content of MoS2 is 5-40wt%.

[0007] The application further provides a preparation method of the sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst, comprising the following steps: dissolving a sulfur source and a molybdenum source in water, stirring uniformly, then adding a metal ion chelating agent and a Cd 0.7 Zn 0.3 S solid solution, stirring uniformly, heating the obtained mixture, and obtaining the sulfur-zinc-cadmium loaded molybdenum disulfide photocatalyst.

[0008] As a preferred technical scheme of the application, the sulfur source comprises thiourea, the molybdenum source comprises (NH4)2MoO4·4H2O, and the metal ion chelating agent comprises citric acid.

[0009] As a preferred technical scheme of the application, the heating temperature is 200-220 DEG C, and the time is 15-20h.

[0010] As a preferred technical scheme of the application, after the heating is completed, the operation of cooling, collecting the solid product, washing and drying is further included.

[0011] As a preferred technical scheme of the application, the preparation method of the Cd 0.7 Zn 0.3 S solid solution comprises the following steps: dissolving polyvinylpyrrolidone, a cadmium source, a zinc source and a sulfur source in water, and performing hydrothermal reaction, and obtaining the Cd 0.7 Zn 0.3 S solid solution.

[0012] As a preferred technical scheme of the application, the cadmium source comprises Cd(CH3COO)2·2H2O, the zinc source comprises Zn(CH3COO)2·2H2O, the sulfur source comprises thiourea, the molar ratio of Cd, Zn and S in the cadmium source, the zinc source and the sulfur source is 0.7:0.3:1, the temperature of the hydrothermal reaction is 140-160 DEG C, and the time is 7-10h.

[0013] The application further provides an application of the sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst in photocatalytic decomposition of water to produce hydrogen.

[0014] As a preferred technical scheme of the present application, the photocatalytic water decomposition for hydrogen production is carried out under sunlight, and the mass ratio of the CdZnS supported MoS2 photocatalyst to water in the photocatalytic water decomposition system is (1-1.5):1, and the reaction temperature is 4-8 ℃.

[0015] As a preferred technical scheme of the present application, the sacrificial agent comprises Na2S with a concentration of 0.2-0.3 M and / or Na2SO3 with a concentration of 0.3 M, and the volume ratio of the sacrificial agent to water is 1:(3-5).

[0016] MoS2 has wide spectral light absorption characteristics and can respond to a wide range of sunlight, which helps to improve the utilization rate of solar energy. However, when MoS2 is used as a single cocatalyst, the active sites are mainly concentrated on the edges, the basal plane has low catalytic activity, and the layered structure is prone to aggregation, which can cover part of the active sites and affect the catalytic efficiency. The CdZnS solid solution has adjustable band gap structure, excellent light absorption performance and high charge separation efficiency, which can effectively promote the migration and separation of photo-generated carriers. Loading MoS2 on the photocatalyst not only helps to enhance the charge separation, but also its unique layered structure, excellent electron transport ability and rich active sites can accelerate the surface reaction kinetics. However, the layered structure of MoS2 is prone to aggregation in practical application, which can reduce the specific surface area and cover the originally rich active sites, thereby reducing the catalytic efficiency. The present application aims to construct a CdZnS supported MoS2 heterojunction composite material, and MoS2 is loaded on the surface of Cd 0.7 Zn 0.3 S by using a one-step hydrothermal method, which promotes the formation of a close interface contact and a Schottky junction between the two, and accelerates the transfer of photo-generated charges by using strong interface coupling. MoS2 loaded on the Cd 0.7 Zn 0.3 S solid solution (Cd 0.7 Zn 0.3 S) can form a synergistic effect with MoS2 due to the adjustable band gap structure, excellent light absorption performance and high charge separation efficiency of Cd 0.7 Zn 0.3The band gap of S can effectively absorb the energy in the visible light region, the adjustable band gap structure and excellent light absorption performance can effectively utilize sunlight, the high-efficiency charge separation efficiency reduces carrier recombination, and the wide spectrum response of MoS2 is combined, so that the solar energy can be more fully utilized to drive the photocatalytic reaction, and the solar energy conversion efficiency is greatly improved. The synergistic effect of the two realizes efficient charge separation of the catalyst, wide spectrum response and improved catalytic activity. The finally obtained photocatalytic hydrogen production material has high activity and low cost, and provides strong support for the scale application of the solar-driven clean hydrogen production technology.

[0017] Compared with the prior art, the present application has the following beneficial effects: The present application provides a kind of sulfur zinc cadmium solid solution loaded molybdenum disulfide photocatalyst, by using one-step hydrothermal method in Cd 0.7 Zn 0.3 S surface constructs MoS2 two-dimensional cocatalyst layer, promotes the formation of close interface contact and Schottky junction, utilizes this strong interface coupling to enhance interaction force, accelerates photoinduced charge transfer, so that it has high activity and low cost, can more fully utilize solar energy to drive photocatalytic reaction, greatly improves solar energy conversion efficiency, provides a feasible solution for efficient and stable photocatalytic hydrogen production technology, and has broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 In the figure, (a) and (b) are SEM images of 15% MoS2 / CdZnS prepared in Example 3 under different magnifications, respectively; Figure 2 In the figure, (a) and (b) are SEM images of 15% MoS2 / CdZnS prepared in Example 3 under different magnifications, respectively; Figure 3 CdZnS obtained in step (1) of Example 1 0.7 Zn 0.3 XRD patterns of MoS2 prepared in Example 1-6 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Example 1-6, and MoS2 prepared in Comparative Example 1; Figure 4 CdZnS obtained in step (1) of Example 1 0.7 Zn 0.3UV-Vis diffuse reflectance absorption spectra of MoS2 prepared in Comparative Example 1 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6; Figure 5 CdZnS prepared in Example 1, Step (1) 0.7 Zn 0.3 Transient photocurrent response curves of MoS2 prepared in Comparative Example 1 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6; Figure 6 CdZnS prepared in Example 1, Step (1) 0.7 Zn 0.3 Hydrogen production performance of MoS2 prepared in Comparative Example 1 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6; Figure 7 Stability test results of 5% MoS2 / CdZnS prepared in Example 1. DETAILED DESCRIPTION

[0020] The following detailed description is presented to enable any person skilled in the art to make and use the application. It is not intended to limit the application as it is described in the broadest terms of the present disclosure. The present application is described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0021] In addition, for numerical ranges that are expressly recited in the present application, it is specifically intended that each and every intermediate value of the recited range is also expressly stated. The intermediate values can be included in or excluded from the range. Each smaller range that falls within the expressly recited range is also expressly stated; the upper and lower limits of the smaller range can be included in or excluded from the range.

[0022] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the patents, patent applications, publications, and descriptions are cited.

[0023] Many modifications and variations of the specific embodiments of the application described herein can be made in light of the above teachings. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0024] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed material or step.

[0025] The raw materials used in the following examples are all commercially available conventional raw materials, which are not particularly limited. The following will not be repeated.

[0026] Example 1 Photocatalyst MoS2 / Cd 0.7 Zn 0.3 The preparation of S is as follows: (1) Cd 0.7 Zn 0.3 Preparation of S: Cd(CH3COO)2·2H2O was used as the cadmium source and Zn(CH3COO)2·2H2O as the zinc source, and CH4N2S as the sulfur source. 0.8 g of polyvinylpyrrolidone (PVP) was dissolved in 60 mL of deionized water, and ultrasonic treatment was performed for 30 min to ensure complete dissolution. Subsequently, 0.625 g of Cd(CH3COO)2·2H2O and 0.221 g of Zn(CH3COO)2·2H2O and 0.2533 g of CH4N2S were added to the completely dissolved PVP solution, and magnetic stirring was performed for 1 hour to ensure thorough mixing. The homogeneous mixed system was transferred to a synthesis reaction kettle lined with polytetrafluoroethylene (PTFE), and heated at 150°C for 8 hours. After cooling to room temperature, the solid sample was collected. Subsequently, the solid sample was purified with deionized water and anhydrous ethanol, repeated three times to remove impurities. Finally, the purified sample was placed in a vacuum drying oven and dried at 60°C for 24 hours to obtain Cd 0.7 Zn 0.3 S solid solution.

[0027] (2) Preparation of MoS2 / CdZnS: 0.012 g of CH4N2S and 0.0061 g of (NH4)2MoO4·4H2O were weighed separately and dissolved in 20 mL of deionized water, and stirred vigorously for 30 min to ensure complete dispersion and a uniform system. Subsequently, 0.082 g of citric acid and 0.1 g of Cd 0.7 Zn 0.3S solid solution. The resulting mixture was stirred vigorously to ensure homogeneity. The mixture was transferred to a Teflon-lined synthesis reactor and heated at 210 °C for 18 hours. After cooling to room temperature, the solid sample was collected and subsequently washed repeatedly three times with deionized water and absolute ethanol to remove impurities and finally dried in a vacuum oven at 60 °C for 24 hours. The resulting sample was labeled as 5% MoS2 / CdZnS.

[0028] Example 2 The same as Example 1, except that in step (2), (NH4)2MoO4-4H2O was weighed at 0.0122 g and CH4N2S was weighed at 0.024 g. The sample was labeled as 10% MoS2 / CdZnS.

[0029] Example 3 The same as Example 1, except that in step (2), (NH4)2MoO4-4H2O was weighed at 0.0183 g and CH4N2S was weighed at 0.036 g. The sample was labeled as 15% MoS2 / CdZnS.

[0030] Example 4 The same as Example 1, except that in step (2), (NH4)2MoO4-4H2O was weighed at 0.0244 g and CH4N2S was weighed at 0.048 g. The sample was labeled as 20% MoS2 / CdZnS.

[0031] Example 5 The same as Example 1, except that in step (2), (NH4)2MoO4-4H2O was weighed at 0.0367 g and CH4N2S was weighed at 0.072 g. The sample was labeled as 30% MoS2 / CdZnS.

[0032] Example 6 The same as Example 1, except that in step (2), (NH4)2MoO4-4H2O was weighed at 0.0488 g and CH4N2S was weighed at 0.096 g. The sample was labeled as 40% MoS2 / CdZnS.

[0033] Comparative Example 1 MoS2was prepared according to the following procedure: 0.724 g of (NH4)2MoO4-4H2O and 1.42 g of thiourea were dissolved in 20 mL of deionized water and stirred vigorously for 30 minutes to ensure complete dispersion and a homogeneous system. The resulting mixture was transferred to a Teflon-lined synthesis reactor and heated at 210 °C for 18 hours. After cooling to room temperature, the sample was collected and subsequently washed repeatedly three times with deionized water and absolute ethanol to remove impurities and finally dried in a vacuum oven at 60 °C for 24 hours to obtain MoS2.

[0034] Effect verification 1. The micro-morphology of the photocatalysts prepared in Examples 1-6 and MoS2 prepared in Comparative Example 1 was observed, Figure 1 Figs. (a) and (b) are SEM images of 15% MoS2 / CdZnS prepared in Example 3 at different magnifications, respectively, Figure 2 Figs. (a) and (b) are SEM images of 15% MoS2 prepared in Comparative Example 1 at different magnifications, respectively, which shows that the Cd 0.7 Zn 0.3 S monomer material is constructed with MoS2 two-dimensional cocatalyst layer on the surface to obtain MoS2 / CdZnS catalyst samples. In the composite catalyst, the morphology of Cd 0.7 Zn 0.3 S does not change significantly, which shows that Cd 0.7 Zn 0.3 S is successfully combined with MoS2 and has good stability in its own structure. Benefiting from this strong coupling effect, a close interface can be established between Cd 0.7 Zn 0.3 S and MoS2, which is conducive to the rapid migration of carriers from Cd 0.7 Zn 0.3 S nanoparticles to MoS2 cocatalyst. 0.7 Zn 0.3 S.

[0035] 2. The XRD patterns of Cd 0.7 Zn 0.3 S obtained in step (1) of Example 1, MoS2 prepared in Comparative Example 1, and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6 are shown in Figure 3 With the increase of MoS2 content, the diffraction peaks of MoS2 / CdZnS remain basically unchanged, which shows the excellent crystalline stability of MoS2 / CdZnS in the heterojunction and confirms the successful synthesis of MoS2 / CdZnS heterojunction. After the introduction of MoS2, the crystal phase structure of all MoS2 / CdZnS samples is similar to that of Cd 0.7 Zn 0.3 S, which shows that the introduction of MoS2 does not change the original crystal structure of Cd 0.7 Zn 0.3 S.

[0036] 3、 Figure 4 shows Cd 0.7 Zn 0.3UV-Vis diffuse reflectance absorption spectra of MoS2 prepared in Comparative Example 1 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6. The light absorption edge of MoS2 / CdZnS composite materials shows a regular change. Compared with Cd 0.7 Zn 0.3 S, the absorption intensity of MoS2 / CdZnS for visible light gradually increases. With the increase of MoS2 content, the response of the absorption edge of MoS2 / CdZnS in the visible light region is significantly enhanced, which is attributed to the strong response of MoS2 in the visible light region. Therefore, the excellent light absorption ability of MoS2 can significantly improve the light capture and utilization of MoS2 / CdZnS, thereby realizing high-efficiency photocatalysis.

[0037] 4, the carrier behavior in the sample was studied by photoelectrochemical method, Figure 5 Cd 0.7 Zn 0.3 S prepared in Comparative Example 1 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6. The results show that, compared with pure MoS2, the photocurrent of the composite sample loaded with MoS2 is significantly improved. Specifically, with the increase of MoS2 loading, the photoelectrochemical performance of the composite sample shows a gradually enhanced trend.

[0038] 5, hydrogen production performance verification: 20 mg of catalyst was added to the reactor, 16 mL of deionized water, 4 mL of 0.25M Na2S and 0.25M Na2SO3 mixed solution (volume ratio of 1:1) were added, and ultrasonic dispersion was carried out for 30 minutes. After 30 minutes of light deposition, the reaction system was vacuumed to-0.1 MPa, and the photocatalytic reaction was started. During the photocatalytic reaction process, the reaction liquid temperature was kept at 6 ℃ (in this experiment, a 300W xenon lamp was used to simulate AM1.5 conditions, so that the light deposition and photocatalytic reaction were carried out in the light intensity environment of standard sunlight). Gas chromatograph (GC-7900) was used to analyze the gas composition by PQ pre-separation column. The gas chromatograph was equipped with a hydrogen flame ionization detector (FID), and the carrier gas was high-purity argon (99.999%). The yield of H2 was calculated according to the retention time and peak area calibrated with the corresponding standard gas. Figure 6 Cd 0.7 Zn 0.3The hydrogen production performance of MoS2 prepared in S, Comparative Example 1 and MoS2 / CdZnS composite materials with different MoS2 loadings prepared in Examples 1-6. The hydrogen production activity of the sample increases approximately linearly with the reaction time, indicating excellent light stability during the reaction. With the increase of MoS2 loading, the hydrogen evolution performance of the composite material shows a trend of first increasing and then decreasing. Pure Cd 0.7 Zn 0.3 S shows a low H2 evolution rate due to fast carrier recombination, while the photocatalytic activity of bare MoS2 is negligible. The H2 release of 15% MoS2 / CdZnS is significantly improved, reaching 1.8 mmol·g -1 ·h -1 , which is about 4.28 times that of the original Cd 0.7 Zn 0.3 S (0.42 mmol·g -1 ·h -1 ). Comprehensive analysis shows that this improvement can be attributed to the successful formation of a Schottky junction between Cd 0.7 Zn 0.3 S and MoS2, which is beneficial to the separation and transmission of photo-generated carriers and increases the number of active sites, and 15% is the best loading ratio, achieving the highest hydrogen production performance.

[0039] Stability test of 5% MoS2 / CdZnS prepared in Example 1: according to the above steps, the photocatalytic reaction is 4 hours for one cycle, after each reaction, the catalyst is taken out, washed with water and the above steps are repeated again, a total of 6 cycles, the hydrogen production is as shown in Figure 7 , the hydrogen production of the last cycle is 87.6% of the initial, it can be seen that the catalyst prepared by the present application has good stability.

[0040] The above description is only a preferred specific embodiment of the present application, the protection scope of the present application is not limited thereto, any skilled person in the art can make equivalent replacement or change according to the technical solution and inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A sulfur-zinc-cadmium solid solution supported molybdenum disulfide photocatalyst, characterized in that, The photocatalyst includes Cd 0.7 Zn 0.3 S solid solution and MoS2 supported on the surface; in the photocatalyst, the content of MoS2 is 5-40 wt%.

2. A method for preparing a CdZnS solid solution supported MoS2 photocatalyst according to claim 1, characterized by, The method comprises the following steps: The sulfur source and the molybdenum source are dissolved in water, stirred, and then the metal ion chelating agent and Cd 0.7 Zn 0.3 S solid solution, and the resulting mixture is heated to obtain the sulfur-zinc-cadmium supported molybdenum disulfide photocatalyst.

3. The preparation method according to claim 2, characterized in that, The sulfur source comprises thiourea, the molybdenum source comprises (NH4)2MoO4·4H2O, and the metal ion chelator comprises citric acid.

4. The production method according to claim 2, characterized by, The heating temperature is 200-220℃, and the time is 15-20h.

5. The preparation method according to claim 4, characterized in that, After the heating, the method further comprises the following steps: cooling, collecting the solid product, washing, and drying.

6. The preparation method according to claim 2, characterized in that, The Cd 0.7 Zn 0.3 The preparation method of the S solid solution comprises the following steps: dissolving polyvinylpyrrolidone, a cadmium source, a zinc source and a sulfur source in water, and performing a hydrothermal reaction to obtain the Cd 0.7 Zn 0.3 S solid solution.

7. The preparation method according to claim 6, characterized in that, The cadmium source comprises Cd(CH3COO)2·2H2O, the zinc source comprises Zn(CH3COO)2·2H2O, the sulfur source comprises thiourea, the molar ratio of Cd, Zn and S in the cadmium source, the zinc source and the sulfur source is 0.7:0.3:1, the temperature of the hydrothermal reaction is 140-160℃, and the time is 7-10h.

8. The application of the sulfur-zinc-cadmium solid solution loaded molybdenum disulfide photocatalyst according to claim 1 in photocatalytic decomposition of water to produce hydrogen.

9. Use according to claim 8, characterized in that, In the photocatalytic decomposition of water to produce hydrogen system, the mass ratio of the sulfur-zinc-cadmium loaded molybdenum disulfide photocatalyst to water is (1-1.5):1, and the reaction temperature is 4-8℃.

10. Use according to claim 9, characterized in that, The sacrificial agent comprises Na2S with a concentration of 0.2-0.3M and / or Na2SO3 with a concentration of 0.3M, and the volume ratio of the sacrificial agent to water is 1:(3-5).

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