Method for synthesizing zinc selenide / copper molybdenum sulfide photocatalyst by solvothermal method

Abstract

The invention belongs to the technical field of photocatalytic hydrogen evolution, and particularly relates to a method for synthesizing a zinc selenide / copper molybdenum sulfide photocatalyst by a solvothermal method. The preparation method comprises the following steps: firstly synthesizing necessary cuprous oxide, then synthesizing copper molybdenum sulfide by taking the cuprous oxide as a template, and finally synthesizing the zinc selenide / copper molybdenum sulfide heterojunction photocatalyst by taking the copper molybdenum sulfide as a cocatalyst. Compared with pure zinc selenide, the zinc selenide / copper molybdenum sulfide photocatalyst has richer hydrogen evolution active sites and lower hydrogen evolution overpotential; and the carrier separation efficiency of the zinc selenide / copper molybdenum sulfide photocatalyst is obviously superior to that of pure zinc selenide, so that the photocatalytic hydrogen evolution activity of the zinc selenide can be obviously improved by introducing copper molybdenum sulfide. Experimental results show that zinc selenide / 1wt% of copper molybdenum sulfide shows optimal hydrogen production performance, and the average hydrogen production rate is 4.14 times that of pure zinc selenide.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic hydrogen evolution, and more particularly relates to a method for synthesizing a zinc selenide / molybdenum copper sulfide photocatalyst by a solvothermal method. BACKGROUND

[0002] Photocatalytic decomposition of water to produce hydrogen is considered to be one of the effective ways to reduce environmental pollution and alleviate energy crisis. Therefore, designing efficient and stable photocatalytic materials has become the research focus of many scholars. At present, various semiconductor nanomaterials have been successfully applied in the field of photocatalytic decomposition of water to produce hydrogen, mainly including nitrides, selenides, metal sulfides, carbides and the like.

[0003] Zinc selenide (ZnSe) is outstanding among many selenides due to its suitable energy band structure and low cost. However, in addition to a suitable band gap, a high-efficiency photocatalyst should also have a fast photo-generated carrier separation and transfer efficiency, a rich hydrogen evolution active site and the like. Apparently, although ZnSe has great potential in the field of photocatalytic hydrogen evolution, there is still a large room for improvement in the photocatalytic hydrogen evolution activity. Therefore, how to improve the photocatalytic hydrogen evolution activity of the ZnSe photocatalyst has become a technical problem to be solved in the field. SUMMARY

[0004] The purpose of the application is to provide a method for synthesizing a zinc selenide / molybdenum copper sulfide (ZnSe / Cu2MoS4) photocatalyst by a solvothermal method, so as to solve the problem of low photocatalytic hydrogen evolution activity of the existing zinc selenide photocatalyst due to low photo-generated carrier separation efficiency and fast photo-generated electron and hole recombination rate.

[0005] To achieve the above purpose, the application provides the following solutions. One of the technical solutions of the application provides a method for synthesizing molybdenum copper sulfide by a solvothermal method, and the steps include: dispersing cuprous oxide (Cu2O) into ethylene glycol (EG), then adding sodium molybdate (Na2MoO4) and thioacetamide (TAA) to mix uniformly, and then performing solvothermal treatment to obtain the molybdenum copper sulfide.

[0006] Further, the preparation step of the cuprous oxide includes: dissolving copper sulfate (CuSO4), sodium citrate (Na3(C6H5O7)) and sodium hydroxide (NaOH) in water, then adding ascorbic acid (C6H8O6) to mix uniformly and then react, and then standing, centrifuging, vacuum drying and grinding to obtain the cuprous oxide (Cu2O).

[0007] Optionally, the molar ratio of the copper sulfate, the sodium citrate and the sodium hydroxide is 0.06:0.017:1.

[0008] Optionally, the molar ratio of the copper sulfate and ascorbic acid is 1:1.

[0009] Optionally, the ascorbic acid is added in the form of an aqueous solution with a concentration of 1wt%.

[0010] Further, the molar ratio of the cuprous oxide, sodium molybdate and thioacetamide is 0.16:0.19:1.

[0011] Further, the temperature of the solvothermal treatment is 160℃ and the time is 12 h.

[0012] Further, the process further comprises a centrifugation and vacuum drying process after the solvothermal treatment.

[0013] Optionally, the temperature of the vacuum drying is 60℃ and the time is 12 h.

[0014] The prepared molybdenum copper sulfide (Cu2MoS4) as a bimetallic sulfide shows more sufficient redox reaction and better conductivity than a monometallic sulfide. Therefore, the molybdenum copper sulfide (Cu2MoS4) can be coupled with other semiconductors as a cocatalyst to become a new type of heterojunction photocatalyst, thereby improving the hydrogen evolution activity of the photocatalyst.

[0015] The second technical scheme of the present application provides an application of the molybdenum copper sulfide prepared by the above method in improving the photocatalytic performance of zinc selenide.

[0016] The third technical scheme of the present application provides a method for synthesizing a zinc selenide / molybdenum copper sulfide photocatalyst by a solvothermal method, comprising: The method uses a selenium source and a zinc source as reactants, the molybdenum copper sulfide prepared by the above method as a cocatalyst, and ethylene glycol as a reducing agent to perform a solvothermal reaction under alkaline conditions, so as to obtain a zinc selenide / molybdenum copper sulfide photocatalyst.

[0017] Further, the selenium source is sodium selenite (Na2SeO3·5H2O).

[0018] Further, the zinc source comprises zinc acetate (Zn(CH3COO)2·2H2O) and / or zinc nitrate (Zn(NO3)2·6H2O).

[0019] Further, the molar ratio of the selenium source and the zinc source is 1:1.

[0020] Further, the molybdenum copper sulfide in the zinc selenide / molybdenum copper sulfide photocatalyst accounts for 0.5-2wt% of the mass of the zinc selenide.

[0021] Optionally, the molybdenum copper sulfide in the zinc selenide / molybdenum copper sulfide photocatalyst accounts for 0.5wt%, 1wt%, 1.5wt% or 2wt% of the mass of the zinc selenide.

[0022] Further, the molar ratio of the ethylene glycol and the selenium source is 356.8:1.

[0023] Further, the temperature of the solvothermal reaction is 160-200℃, and the time is 18-36 h.

[0024] Optionally, the temperature of the solvothermal reaction is 180℃, and the time is 24 h.

[0025] Further, the alkaline condition is that the pH value is adjusted to 12-13 by a sodium hydroxide solution with a concentration of 5 M.

[0026] Further, after the solvothermal reaction, the process of centrifugation and vacuum drying is further included.

[0027] Optionally, the temperature of the vacuum drying is 50-70℃, and the time is 10-15 h.

[0028] Preferably, the temperature of the vacuum drying is 60℃, and the time is 12 h.

[0029] The fourth technical solution of the present application provides a zinc selenide / molybdenum copper sulfide photocatalyst, which is prepared by the above method.

[0030] The fifth technical solution of the present application provides an application of the above zinc selenide / molybdenum copper sulfide photocatalyst in photocatalytic hydrogen evolution.

[0031] The sixth technical solution of the present application provides a method for improving the photocatalytic activity of zinc selenide, which comprises: In the synthesis process of zinc selenide, the molybdenum copper sulfide prepared by the above method is introduced as a cocatalyst to prepare a zinc selenide / molybdenum copper sulfide photocatalyst.

[0032] The present application discloses the following technical effects: The zinc selenide / molybdenum copper sulfide (ZnSe / Cu2MoS4) photocatalyst synthesized by using the non-noble metal molybdenum copper sulfide (Cu2MoS4) as a cocatalyst has low production cost, high product purity and good crystallinity. Compared with pure zinc selenide (ZnSe), the zinc selenide / molybdenum copper sulfide (ZnSe / Cu2MoS4) photocatalyst has more abundant hydrogen evolution active sites and lower hydrogen evolution overpotential; and the carrier separation efficiency of the zinc selenide / molybdenum copper sulfide (ZnSe / Cu2MoS4) photocatalyst is obviously better than that of pure zinc selenide (ZnSe). BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The accompanying drawings do not constitute an inappropriate limitation on the present application. In the drawings: Figure 1 Flow chart for preparing ZnSe / Cu2MoS4 of Example 1.

[0034] Figure 2 XRD patterns of the photocatalysts prepared for Cu2MoS4 of Example 1, Examples 1-4 and Comparative Examples 1-4.

[0035] Figure 3 Effect diagrams of the photocatalysts prepared for Comparative Example 1, Comparative Example 2, Comparative Example 4 and Examples 1-4, wherein (a) is a plot of hydrogen evolution amount versus time, and (b) is a plot of average hydrogen evolution rate.

[0036] Figure 4 Photoelectrochemical performance diagrams of different photocatalysts, wherein (a) is an EIS diagram of the photocatalysts of Comparative Example 1 and Examples 1-4 and copper molybdenum sulfide of Example 1, (b) is a transient photocurrent response diagram of the photocatalysts of Comparative Example 1 and Examples 1-4 and copper molybdenum sulfide of Example 1, (c) is an LSV curve diagram of copper molybdenum sulfide of Example 1, Comparative Example 1, Example 2, and (d) is a Tafel slope diagram of Comparative Example 1 and Example 2. DETAILED DESCRIPTION

[0037] Various illustrative embodiments of the present application are now described in detail below. The following description includes specific details for the purpose of providing a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring the understanding of the present application.

[0038] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, for a range of values of a parameter, unless otherwise indicated, each intervening value by each intervening value, as well as any other stated or intervening value in that stated range is encompassed. In addition, any combination of the above ranges, as well as any other stated or intervening value in that stated range, is encompassed. Unless otherwise stated, the above ranges are inclusive of the recited endpoints.

[0039] 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 in their entirety for the disclosure and

[0040] Many modifications and variations to the illustrative embodiments described herein will be apparent to those of ordinary skill in the art from this specification, which is to be regarded in the light of defining and enabling the scope of the present application. 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.

[0041] 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 including, but not limited to.

[0042] In some embodiments, the present application provides a method for synthesizing a zinc selenide / molybdenum copper sulfide photocatalyst by a solvothermal method, comprising: S1, dissolving copper sulfate (CuSO4), sodium citrate (Na3(C6H5O7)) and sodium hydroxide (NaOH) in deionized water in sequence, then adding ascorbic acid (C6H8O6) and mixing and reacting thoroughly, and then standing, centrifuging, vacuum drying and grinding to obtain cuprous oxide (Cu2O); The molar ratio of copper sulfate, sodium citrate and sodium hydroxide is 0.06:0.017:1; the molar ratio of the copper sulfate and ascorbic acid is 1:1; the ascorbic acid is added in the form of an aqueous solution, and the concentration is 1wt%; In step S1, after mixing copper sulfate (CuSO4), sodium citrate (Na3(C6H5O7)) and sodium hydroxide (NaOH), a double decomposition reaction occurs. Since the size of the precipitated particles is related to the degree of supersaturation, the greater the degree of supersaturation, the smaller the particles formed. Therefore, in order to form smaller nanoparticles, sodium citrate needs to be added to rapidly nucleate in a short period of time and form a large number of nanoparticles, otherwise larger precipitated particles will be obtained. Ascorbic acid (C6H8O6) is added as a reducing agent to reduce copper hydroxide to obtain cuprous oxide (Cu2O), and the specific reaction process is as follows: CuSO4+2NaOH→Cu(OH)2↓+Na2SO4; 2Cu(OH)2+C6H8O6→Cu2O+ 3H2O+C6H6O6; S2, dispersing the cuprous oxide (Cu2O) into ethylene glycol (EG), adding anhydrous sodium molybdate (Na2MoO4) and thioacetamide (TAA), mixing uniformly, and then performing solvothermal treatment, and after the reaction is completed, centrifuging, vacuum drying and grinding to obtain the molybdenum copper sulfide (Cu2MoS4); The molar ratio of cuprous oxide, sodium molybdate and thioacetamide is 0.16:0.19:1; the temperature of the solvothermal treatment is 160°C, and the time is 12 h; the vacuum drying temperature is 60°C, and the time is 12 h; In step S2, cuprous oxide (Cu2O) is subjected to a redox reaction with ethylene glycol (EG), sodium molybdate (Na2MoO4) and thioacetamide (TAA) to obtain copper molybdenum sulfide (Cu2MoS4), and the specific reaction process is as follows: Cu2O+Na2MoO4+4C2H5NS+H2O→Cu2MoS4+4C2H5NO+2NaOH; S3, the selenium source and the zinc source are dissolved in deionized water and mixed, then sodium hydroxide (NaOH) is added to adjust the pH value to 12-13, then copper molybdenum sulfide (Cu2MoS4) and ethylene glycol (EG) are added, and the mixture is subjected to solvothermal treatment, and after the reaction is completed, the selenium zinc / copper molybdenum sulfide (ZnSe / Cu2MoS4) photocatalyst is obtained by centrifugation, vacuum drying and grinding; The selenium source is sodium selenite (Na2SeO3·5H2O); the zinc source includes zinc acetate (Zn(CH3COO)2·2H2O) and / or zinc nitrate (Zn(NO3)2·6H2O); the molar ratio of the selenium source to the zinc source is 1:1; the copper molybdenum sulfide in the selenium zinc / copper molybdenum sulfide photocatalyst is 0.5-2% of the mass of the selenium zinc; the molar ratio of the ethylene glycol to the selenium source is 356.8:1; the temperature of the solvothermal reaction is 160-200°C, and the time is 18-36 h; sodium hydroxide is added in the form of an aqueous solution, and the concentration is 5 M; the vacuum drying temperature is 50-70°C, and the time is 10-15 h; In step S3, sodium selenite (Na2SeO3·5H2O) is first subjected to a redox reaction with ethylene glycol (EG) to generate sodium selenide (Na2Se), and then sodium selenide (Na2Se) is subjected to a double decomposition reaction with zinc acetate (Zn(CH3COO)2·2H2O) to generate zinc selenide (ZnSe) precipitate, and the specific reaction process is as follows: 5Na2SeO3+3C2H6O2→5Na2Se+6CO2↑+9H2O; Na2Se+Zn(CH3COO)2→ZnSe↓+2CH3COONa.

[0043] The present application first synthesizes the necessary cuprous oxide (Cu2O), then synthesizes copper molybdenum sulfide (Cu2MoS4) using cuprous oxide (Cu2O) as a template, and finally uses copper molybdenum sulfide (Cu2MoS4) as a cocatalyst to synthesize a zinc selenide / copper molybdenum sulfide (ZnSe / Cu2MoS4) heterojunction photocatalyst.

[0044] The specific reaction process of the application is as follows: copper sulfate (CuSO4), sodium citrate (Na3(C6H5O7)) and sodium hydroxide (NaOH) are sequentially dissolved in deionized water, and ascorbic acid (C6H8O6) solution is added and mixed thoroughly; cuprous oxide (Cu2O) is obtained by standing, centrifugation, vacuum drying and grinding; the cuprous oxide (Cu2O) is dispersed into ethylene glycol (EG), and sodium molybdate (Na2MoO4) and thioacetamide (TAA) are added and mixed uniformly, followed by solvent thermal treatment; after the reaction is completed, the selenium zinc / sulfur molybdenum copper (ZnSe / Cu2MoS4) photocatalyst is obtained by centrifugation, vacuum drying and grinding.

[0045] Unless otherwise specified, the raw materials and reagents involved in the specific embodiments of the application are commercially available products.

[0046] Unless otherwise specified, the room temperature and normal temperature referred to in the specific embodiments of the application both refer to 20-30℃.

[0047] It should be noted that the details not described in the application are all conventional operating means in the art, and are not the focus of the application.

[0048] Example 1 The method for synthesizing the selenium zinc / sulfur molybdenum copper photocatalyst by the solvent thermal method comprises the following steps: S1, copper sulfate (CuSO4), sodium citrate (Na3(C6H5O7)) and sodium hydroxide (NaOH) are sequentially dissolved in deionized water, and ascorbic acid (C6H8O6) is added and mixed thoroughly and reacted, followed by standing, centrifugation, vacuum drying and grinding to obtain cuprous oxide (Cu2O); The molar ratio of copper sulfate, sodium citrate and sodium hydroxide is 0.06:0.017:1; the molar ratio of copper sulfate and ascorbic acid is 1:1; the ascorbic acid is added in the form of an aqueous solution, and the concentration is 1wt%; S2, the cuprous oxide (Cu2O) is dispersed into ethylene glycol (EG), and anhydrous sodium molybdate (Na2MoO4) and thioacetamide (TAA) are added and mixed uniformly, followed by solvent thermal treatment; after the reaction is completed, the selenium zinc / sulfur molybdenum copper (Cu2MoS4) is obtained by centrifugation, vacuum drying and grinding; The mass ratio of cuprous oxide and ethylene glycol is 1:1230; the molar ratio of cuprous oxide, sodium molybdate and thioacetamide is 0.16:0.19:1; the temperature of the solvothermal treatment is 160°C, and the time is 12 hours; the vacuum drying temperature is 60°C, and the time is 12 hours; S3, the selenium source and the zinc source are dissolved in deionized water and mixed, then sodium hydroxide (NaOH) is added to adjust the pH value to 12, then copper molybdenum sulfide (Cu2MoS4) and ethylene glycol (EG) are added, and the mixture is fully mixed and then subjected to solvothermal treatment. After the reaction is completed, the zinc selenide / copper molybdenum sulfide (ZnSe / Cu2MoS4) photocatalyst is obtained by centrifugation, vacuum drying and grinding, and is denoted as 0.5CMS / ZS; The selenium source is sodium selenite (Na2SeO3·5H2O); the zinc source is zinc acetate (Zn(CH3COO)2·2H2O); the molar ratio of the selenium source and the zinc source is 1:1; the copper molybdenum sulfide in the zinc selenide / copper molybdenum sulfide photocatalyst is 0.5wt% of the mass of the zinc selenide; the molar ratio of ethylene glycol and the selenium source is 356.8:1; the temperature of the solvothermal reaction is 180°C, and the time is 24 hours; sodium hydroxide is added in the form of an aqueous solution, and the concentration is 5M; the vacuum drying temperature is 60°C, and the time is 12 hours.

[0049] Example 2 Compared with Example 1, the difference is that the copper molybdenum sulfide in the zinc selenide / copper molybdenum sulfide photocatalyst is 1wt% of the mass of the zinc selenide, and the product is denoted as 1CMS / ZS.

[0050] Example 3 Compared with Example 1, the difference is that the copper molybdenum sulfide in the zinc selenide / copper molybdenum sulfide photocatalyst is 1.5wt% of the mass of the zinc selenide, and the product is denoted as 1.5CMS / ZS.

[0051] Example 4 Compared with Example 1, the difference is that the copper molybdenum sulfide in the zinc selenide / copper molybdenum sulfide photocatalyst is 2wt% of the mass of the zinc selenide, and the product is denoted as 2CMS / ZS.

[0052] Comparative Example 1 The preparation steps of the zinc selenide (ZnSe) photocatalyst include: Sodium selenite (Na2SeO3·5H2O) and zinc acetate (Zn(CH3COO)2·2H2O) were dissolved in deionized water and mixed, and then sodium hydroxide (NaOH) and ethylene glycol (EG) were added. After being mixed thoroughly, the mixture was subjected to solvothermal treatment. After the reaction was completed, the zinc selenide (ZnSe) photocatalyst was obtained through centrifugation, vacuum drying and grinding. The molar ratio of sodium selenite to zinc acetate was 1:1. The molar ratio of ethylene glycol to selenium source was 356.8:1. The solvothermal reaction temperature was 180°C, and the reaction time was 24 h. Sodium hydroxide was added in the form of an aqueous solution, and the concentration was 5 M. The vacuum drying temperature was 60°C, and the vacuum drying time was 12 h.

[0053] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 is that the zinc source in the zinc selenide / molybdenum copper sulfide photocatalyst is zinc nitrate (Zn(NO3)2·6H2O), and the product is denoted as ZnSe-2.

[0054] Comparative Example 3 The preparation steps of the photocatalyst include: S1, copper sulfate (CuSO4) and sodium hydroxide (NaOH) were sequentially dissolved in deionized water, and then ascorbic acid (C6H8O6) was added. After being mixed and reacted thoroughly, cuprous oxide (Cu2O) was obtained through standing, centrifugation, vacuum drying and grinding. The molar ratio of copper sulfate to sodium hydroxide was 0.06:1. The molar ratio of copper sulfate to ascorbic acid was 1:1. Ascorbic acid was added in the form of an aqueous solution, and the concentration was 1wt%. S2, the cuprous oxide (Cu2O) was dispersed in ethylene glycol (EG), and then anhydrous sodium molybdate (Na2MoO4) and thioacetamide (TAA) were added and mixed uniformly. After being subjected to solvothermal treatment, the molybdenum copper sulfide, i.e., the photocatalyst, was obtained through centrifugation, vacuum drying and grinding, and was denoted as Cu2MoS4-2. The mass ratio of cuprous oxide to ethylene glycol was 1:1230. The molar ratio of cuprous oxide, sodium molybdate and thioacetamide was 0.16:0.19:1. The solvothermal treatment temperature was 160°C, and the treatment time was 12 h. The vacuum drying temperature was 60°C, and the vacuum drying time was 12 h.

[0055] Comparative Example 4 The preparation steps of the photocatalyst include: The selenium source and the zinc source were dissolved in deionized water and mixed, and then sodium hydroxide (NaOH) was added to adjust the pH value to 12. Subsequently, the molybdenum copper sulfide (Cu2MoS4-2) prepared in Comparative Example 3 and ethylene glycol (EG) were added. After being mixed thoroughly, the mixture was subjected to solvothermal treatment. After the reaction was completed, the photocatalyst was obtained through centrifugation, vacuum drying and grinding, and was denoted as 1CMS / ZS-2. The selenium source was sodium selenite (Na2SeO3·5H2O); the zinc source was zinc acetate (Zn(CH3COO)2·2H2O); the molar ratio of the selenium source to the zinc source was 1:1; the mass fraction of the molybdenum copper sulfide in the photocatalyst to the mass of the zinc selenide was 1%; the molar ratio of the ethylene glycol to the selenium source was 356.8:1; the temperature of the solvothermal reaction was 180°C, and the time was 24 h; the sodium hydroxide was added in the form of an aqueous solution, and the concentration was 5M; the temperature of the vacuum drying was 60°C, and the time was 12 h.

[0056] Test Example Figure 1 A flowchart for preparing the ZnSe / Cu2MoS4 of Example 1 is shown.

[0057] Figure 2 XRD patterns of the photocatalysts prepared in Example 1 (Cu2MoS4), Example 1-4, and Comparative Examples 1-4 are shown. The XRD patterns were obtained by using a Cu Kα radiation source (λ=1.5406 A) at a scanning speed of 0.5° / min. Figure 2 As can be seen, the molybdenum copper sulfide (Cu2MoS4) and Comparative Example 3 both have 7 obvious characteristic peaks and perfectly correspond to the standard card PDF #81-1159. In addition, the photocatalysts prepared in Example 1-4, Comparative Example 4, and the zinc selenide (ZnSe) prepared in Comparative Examples 1 and 2 all exhibit 5 diffraction peaks corresponding to the standard card PDF #88-2345. None of the above samples exhibit other impurity peaks, which indicates that the molybdenum copper sulfide (Cu2MoS4), the zinc selenide / molybdenum copper sulfide (ZnSe / Cu2MoS4) photocatalyst, and the zinc selenide (ZnSe) are all successfully prepared.

[0058] The photocatalytic hydrogen evolution test was carried out in a sealed reaction system under xenon lamp irradiation using a sodium sulfide / sodium sulfite (Na2S / Na2SO3) solution as a sacrificial agent. The total amount of hydrogen evolution of the zinc selenide / molybdenum copper sulfide (ZnSe / Cu2MoS4) photocatalyst prepared in Example 1-4, Comparative Example 4, and the zinc selenide (ZnSe) prepared in Comparative Examples 1 and 2 was analyzed by a gas chromatograph within 5 h, and the average hydrogen evolution rate was calculated, as shown in Table 1. Figure 3 The specific method is as follows: Open the nitrogen cylinder main valve, adjust the pressure to 0.4 MPa; open the gas chromatograph and the sample system for preheating; open the cooling water for precooling; dissolve 2.5219 g of sodium sulfide (Na2S·9H2O) and 0.9453 g of sodium sulfite (Na2SO3) in 20 mL of deionized water as a sacrificial agent; then ultrasonic disperse 30 mg of zinc selenide / molybdenum sulfide copper (ZnSe / Cu2MoS4) photocatalyst into the sacrificial agent; move the above suspension and 10 mL of deionized water cleaning liquid into the reactor and seal; after the reactor is assembled, rotate the knob to the vacuum pump to exhaust the air in the reactor; after the internal pressure is stable, rotate to the sample, run the setting program, and expose the reactor to a 50 W (total output power) xenon lamp. The gas chromatograph automatically samples every hour and records the H2 concentration, and the test is completed after five consecutive samples.

[0059] Figure 3 The effect diagram of the photocatalyst prepared for Comparative Example 1, Comparative Example 2, Comparative Example 4 and Examples 1-4, wherein (a) is the hydrogen evolution amount-time change diagram, and (b) is the average hydrogen evolution rate diagram. As can be seen from the diagram, the total amount of hydrogen evolution of the 0.5CMS / ZS photocatalyst prepared in Example 1 is 203.8 μmol / 30 mg, and the corresponding average hydrogen evolution rate is 1358.75 μmol·g -1 ·h -1 ; the total amount of hydrogen evolution of the 1CMS / ZS photocatalyst prepared in Example 2 is 333.1 μmol / 30 mg, and the corresponding average hydrogen evolution rate is 2220.48 μmol·g -1 ·h -1 ; the total amount of hydrogen evolution of the 1.5CMS / ZS photocatalyst prepared in Example 3 is 245.9 μmol / 30 mg, and the corresponding average hydrogen evolution rate is 1639.20 μmol·g -1 ·h -1 ; the total amount of hydrogen evolution of the 2CMS / ZS photocatalyst prepared in Example 4 is 185.4 μmol / 30 mg, and the corresponding average hydrogen evolution rate is 1235.98 μmol·g -1 ·h -1 ; the total amount of hydrogen evolution of the ZnSe photocatalyst prepared in Comparative Example 1 is 80.5 μmol / 30 mg, and the corresponding average hydrogen evolution rate is 536.90 μmol·g -1 ·h -1 ; the total amount of hydrogen evolution of the ZnSe-2 photocatalyst prepared in Comparative Example 2 is 29.2 μmol / 30 mg, and the corresponding average hydrogen evolution rate is 194.52 μmol·g -1 ·h -1The total amount of hydrogen evolution of the 1CMS / ZS-2 photocatalyst prepared in Comparative Example 4 was 119.3 μmol / 30 mg, and the corresponding average hydrogen evolution rate was 795.30 μmol·g -1 ·h -1 It can be seen that the total amount of hydrogen evolution and the average hydrogen evolution rate of the ZnSe-2, 1CMS / ZS-2 photocatalysts prepared in Comparative Example 2 and Comparative Example 4 are not good compared with Comparative Example 1 and Example 2. In addition, the total amount of hydrogen evolution and the average hydrogen evolution rate of the ZnSe / Cu2MoS4 photocatalyst show a trend of first increasing and then decreasing with the increase of the content of Cu2MoS4, because the Cu2MoS4 with a small amount is beneficial to the separation of the photo-generated electron-hole pairs of ZnSe, but when the content exceeds 1wt%, Cu2MoS4 will block the xenon lamp light source and act as a recombination center of the photo-generated carriers, so that the average hydrogen evolution rate decreases.

[0060] Figure 4 are the EIS diagrams of the photocatalysts of Comparative Example 1 and Examples 1-4 and Cu2MoS4 in Example 1, (b) are the transient photocurrent response diagrams of the photocatalysts of Comparative Example 1 and Examples 1-4 and Cu2MoS4 in Example 1, (c) are the LSV curves of Cu2MoS4 in Example 1, Comparative Example 1, Example 2, and (d) are the Tafel slope diagrams of Comparative Example 1 and Example 2. From the diagrams, in (a), the arc radius of the ZnSe / Cu2MoS4 photocatalysts of Examples 1-4 is smaller than that of the pure ZnSe of Comparative Example 1, which indicates that the interfacial impedance of ZnSe / Cu2MoS4 is also smaller, and 1CMS / ZS has the smallest impedance, which represents that the charge transfer rate of 1CMS / ZS is also the fastest. In (b), the ZnSe / Cu2MoS4 photocatalysts of Examples 1-4 exhibit stronger photocurrent response under visible light than the pure ZnSe of Comparative Example 1, and 1CMS / ZS has the strongest response (about 0.19 μA / cm 2 ), which indicates that 1CMS / ZS has the highest efficient carrier separation. In (c) and (d), the hydrogen evolution overpotential of 1CMS / ZS (Example 2) (-0.1 V) is obviously lower than that of the pure ZnSe of Comparative Example 1 (-0.2 V), and 1CMS / ZS can obtain a higher current density than the pure ZnSe at the same voltage, and the Tafel slope (0.41 mV·dec -1 ) obtained by 1CMS / ZS is also obviously higher than that of the pure ZnSe (0.32 mV·dec -1), which all indicate that the photocatalytic hydrogen evolution activity of 1CMS / ZS is much higher than that of pure ZnSe, and 1CMS / ZS is easier to evolve hydrogen in the aspect of hydrogen evolution kinetics.

[0061] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be mutually referred to.

[0062] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for the synthesis of molybdenum copper sulfide by a solvothermal process, characterized in that the steps of The method comprises the following steps: The cuprous oxide is dispersed in ethylene glycol, then sodium molybdate and thioacetamide are added and uniformly mixed, and then solvent thermal treatment is performed to obtain the molybdenum copper sulfide.

2. The method of claim 1, wherein, The preparation of the cuprous oxide comprises the following steps: dissolving copper sulfate, sodium citrate and sodium hydroxide in water, then adding ascorbic acid and uniformly mixing, and then reacting, standing, centrifuging, vacuum drying and grinding to obtain the cuprous oxide. The molar ratio of the copper sulfate, the sodium citrate and the sodium hydroxide is 0.06:0.017:

1. The molar ratio of the copper sulfate and the ascorbic acid is 1:

1. The ascorbic acid is added in the form of an aqueous solution, and the concentration is 1wt%.

3. The method of claim 1, wherein, The molar ratio of the cuprous oxide, the sodium molybdate and the thioacetamide is 0.16:0.19:

1. The temperature of the solvent thermal treatment is 160℃, and the time is 12 hours. The solvent thermal treatment is followed by the steps of centrifuging and vacuum drying.

4. The application of the molybdenum copper sulfide prepared by the method of any one of claims 1-3 in improving the photocatalytic performance of zinc selenide.

5. A method for synthesizing a zinc selenide / molybdenum copper sulfide photocatalyst by a solvothermal method, characterized in that, The method comprises the following steps: The molybdenum copper sulfide prepared by the method of any one of claims 1-3 is used as a cocatalyst in a solvent thermal reaction of a selenium source and a zinc source in an alkaline condition, and ethylene glycol is used as a reducing agent to obtain a zinc selenide / molybdenum copper sulfide photocatalyst.

6. The method of claim 5, wherein, The selenium source is sodium selenite. The zinc source comprises zinc acetate and / or zinc nitrate. The molar ratio of the selenium source and the zinc source is 1:

1. The molybdenum copper sulfide in the zinc selenide / molybdenum copper sulfide photocatalyst accounts for 0.5-2wt% of the mass of the zinc selenide. The molar ratio of the ethylene glycol and the selenium source is 356.8:

1.

7. The method of claim 5, wherein, The temperature of the solvent thermal reaction is 160-200℃, and the time is 18-36 hours. The alkaline condition is that the pH value is adjusted to 12-13 by a sodium hydroxide solution with a concentration of 5M. The solvent thermal reaction is followed by the steps of centrifuging and vacuum drying.

8. A zinc selenide / molybdenum sulfide copper photocatalyst, characterized by, The zinc selenide / molybdenum copper sulfide photocatalyst is prepared by the method of any one of claims 5-7.

9. The application of the zinc selenide / molybdenum copper sulfide photocatalyst of claim 8 in photocatalytic hydrogen evolution.

10. A method of enhancing the photocatalytic activity of zinc selenide, characterized by, The method comprises the following steps: The molybdenum copper sulfide prepared by the method of any one of claims 1-3 is introduced as a cocatalyst in the synthesis of zinc selenide to obtain a zinc selenide / molybdenum copper sulfide photocatalyst.

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