Preparation method of novel photocatalytic hydrogen production material Cu-ZnS / ZnO

Abstract

The invention provides a preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO, and belongs to the technical field of photocatalytic materials. According to the invention, ZnO and Cu-ZnS are respectively prepared by adopting a hydrothermal method, then ZnO is added into the turbid liquid of Cu-ZnS, and then the Cu-ZnS / ZnO composite photocatalyst is successfully synthesized by adopting the hydrothermal method, so that the preparation process is simple, the equipment requirement is low, and the production cost is low. The prepared Cu-ZnS / ZnO photocatalytic hydrogen production activity is high, under simulated sunlight irradiation, 0.05 g of the prepared optimal composite photocatalytic material is dispersed in 100 mL of shale gas flowback wastewater containing sacrificial agents (0.35 mol / L Na2S and 0.25 mol / L Na2SO3), illumination is carried out for 3 hours, the hydrogen production amount reaches 2645.1 micromol, the corresponding hydrogen production rate is 17000 micromol.g <-1 >. H <-1 >, and the product prepared through the method can be widely applied to the field of photocatalytic hydrogen production.

Description

Technical Field

[0001] The present invention relates to a preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO, belonging to the technical field of inorganic catalytic materials. Background Art

[0002] As an efficient and pollution-free energy carrier, hydrogen gas is regarded as an important part of the future energy system due to its high energy density and the fact that its combustion product is water. Photocatalytic hydrogen production technology uses solar energy to drive water decomposition for hydrogen production, providing a highly potential solution for the production of green hydrogen. Among various semiconductor photocatalytic materials, zinc sulfide (ZnS), as a classic sulfide, has received extensive attention due to its rich sources, simple synthesis process, high electrochemical stability, low cost, and environmental friendliness. However, it still has problems such as a relatively large band gap, low charge separation efficiency, and photocorrosion. To improve the photocatalytic activity of ZnS, copper ions (Cu 2+ ) and zinc oxide (ZnO) are respectively selected as representatives of metal doping elements and semiconductor support materials to prepare a ternary composite catalyst, thereby effectively improving the hydrogen production performance of the material. Copper (Cu), as an excellent conductor among transition metals, can release a large number of free electrons under the action of metal bonding. These electrons flow almost unobstructed in the lattice, achieving efficient current transmission. When used as a doping element, it can effectively regulate the band structure of the semiconductor, narrow the band gap, and broaden the excitation band of the photocatalytic reaction. And ZnO has a similar band gap to ZnS. ZnS has a sufficient reduction potential, and ZnO has a sufficient oxidation potential, promising to form a stepped staggered band structure, shortening the transfer distance of photogenerated carriers, and thus obtaining high-efficiency photocatalytic performance.

[0003] Currently, researchers have modified ZnS materials by means of defect engineering, element doping, heterojunction composite, etc. to make up for the defects of single-component photocatalyst materials and obtain more excellent photocatalytic materials. For example, in the article "Highly boosted photocatalytic H2 production from ZnS particles assisted by Cd-Cu co-doping" in "Journal of Environmental Chemical Engineering", Volume 11, Issue 3, Article No. 109833 (Comparative Document 1), a Cd-Cu co-doped ZnS composite photocatalyst was prepared by a solvothermal method using acetonitrile as a solvent. The disadvantages of this method are: (1) Acetonitrile has a toxicity risk and will decompose and carbonize under high-temperature conditions, affecting the purity of the product; (2) The hydrogen production activity of the composite photocatalyst is relatively low. Under simulated sunlight, the best hydrogen production rate of Cu / Cd-ZnS is only 6401.06 μmol·g-1 ·h -1 。Also, in the article "Induction of a piezo-potential improves photocatalytic hydrogen production over ZnO / ZnS / MoS2 heterostructures" in Volume 93, Issue 106867 of "Nano Energy" (Comparative Document 2), a ZnO / ZnS / MoS2 photocatalytic material was synthesized by a stepwise hydrothermal method. The disadvantages of this method are: (1) The hydrogen production activity of the composite photocatalyst is relatively low, and the optimal hydrogen production rate under simulated sunlight irradiation is 10420 μmol·g -1 ·h -1 ; (2) Hexamethylenetetramine was added during the preparation of ZnO, and a large amount of volatile substances will be discharged during subsequent drying and heat treatment processes, causing pollution to the atmospheric environment. Summary of the Invention

[0004] In view of the problems of the relatively large band gap and easy recombination of charge carriers in the single ZnS sample, the present invention proposes to jointly prepare a Cu-ZnS / ZnO ternary composite photoanode material by means of metal Cu 2+ doping and ZnO compounding to improve the defects existing in the structure and performance of a single semiconductor material, and to investigate its hydrogen production activity in shale gas flowback wastewater. The preparation process of this method is simple, the catalytic activity of the composite photocatalytic material is high and the cost is low, which provides technical support for the research of ZnS-based photocatalytic materials and photocatalytic hydrogen production technology. The preparation method of the Cu-ZnS / ZnO composite photocatalytic material of the present invention is as follows:

[0005] (1) Preparation of ZnO

[0006] Weigh 0.56 g of Zn(CHCOO)2·2H2O, 0.4 g of polyvinylpyrrolidone, and 0.5 g of urea into a 100 mL beaker, add 60 mL of ethylene glycol, and magnetically stir for 1 h to obtain a mixed solution; transfer the mixed solution to a 100 mL autoclave, place it in an oven, and carry out hydrothermal reaction at 180 °C for 2 h; naturally cool to room temperature, filter, wash the filter cake 3 times with deionized water and absolute ethanol respectively, place it in a vacuum oven and dry at 60 °C for 12 h, and grind to obtain light yellow ZnO powder.

[0007] (2) Preparation of Cu-ZnS

[0008] Weigh 1.317 g of Zn(CHCOO)2·2H2O and 0.4568 g of thiourea into a 100 mL beaker, add 60 mL of deionized water, stir magnetically for 30 min to dissolve, then add 0.0725 g of Cu(NO3)2·3H2O, and continue stirring for 1 h to obtain a transparent Cu-ZnS precursor solution; transfer the precursor solution to a 100 mL autoclave, place it in an oven and carry out hydrothermal reaction at 180 °C for 18 h; after natural cooling to room temperature, filter, wash the filter cake with deionized water and absolute ethanol three times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain green Cu-ZnS powder.

[0009] (3) Preparation of Cu-ZnS / ZnO

[0010] Weigh 0.25 g of Cu-ZnS powder into a 50 mL beaker, add 30 mL of deionized water, ultrasonicate for 3 min to obtain a green suspension, add ZnO powder with a mass ratio of 5 wt% - 20 wt%, and ultrasonicate for 30 min to obtain a uniformly dispersed precursor solution; transfer the precursor solution to a 50 mL reaction kettle, place it in an oven and carry out hydrothermal reaction at 180 °C for 18 h; after natural cooling to room temperature, filter, wash the filter cake with deionized water and absolute ethanol three times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain the Cu-ZnS / ZnO photocatalytic material.

[0011] The present invention adopts the above technical scheme and mainly has the following effects:

[0012] (1) The Cu-ZnS / ZnO composite photocatalytic material prepared by the present invention has high photocatalytic activity. Under the irradiation of a xenon lamp simulating sunlight (340 - 800 nm), disperse 0.05 g of the prepared optimal composite photocatalytic material in 100 mL of shale gas produced water containing sacrificial agents (0.35 mol / L Na2S and 0.25 mol / L Na2SO3), irradiate for 3 h, and the hydrogen production amount is as high as 2645.1 μmol, and the corresponding hydrogen production rate is 17000 μmol·g -1 ·h -1 , which are all superior to the results of Comparative Document 1 and Comparative Document 2.

[0013] (2) The present invention is prepared by a hydrothermal method, with a simple preparation method, few required equipment, and low cost. Description of the Drawings

[0014] Figure 1 It is the X-ray diffraction pattern of ZnS, Cu-ZnS and Cu-ZnS / ZnO.

[0015] Figure 2 It is the SEM image of ZnS, Cu-ZnS and Cu-ZnS / ZnO.

[0016] Figure 3 Hydrogen production effect comparison diagrams of ZnS, Cu-ZnS, and Cu-ZnS / ZnO. Specific embodiments

[0017] The present invention will be further described below in conjunction with specific embodiments.

[0018] Example 1

[0019] A preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO, the specific steps are as follows:

[0020] (1) Preparation of ZnO

[0021] Weigh 0.56 g of Zn(CHCOO)2·2H2O, 0.4 g of polyvinylpyrrolidone, and 0.5 g of urea into a 100 mL beaker, add 60 mL of ethylene glycol, and magnetically stir for 1 h to obtain a mixed solution; transfer the mixed solution to a 100 mL autoclave, place it in an oven and hydrothermally react at 180 °C for 2 h; naturally cool to room temperature, filter, wash the filter cake with deionized water and absolute ethanol 3 times respectively, place it in a vacuum oven and dry at 60 °C for 12 h, and grind to obtain pale yellow ZnO powder.

[0022] (2) Preparation of Cu-ZnS

[0023] Weigh 1.317 g of Zn(CHCOO)2·2H2O and 0.4568 g of thiourea into a 100 mL beaker, add 60 mL of deionized water, magnetically stir for 30 min to dissolve, then add 0.0725 g of Cu(NO3)2·3H2O, and continue to stir for 1 h to obtain a transparent Cu-ZnS precursor solution; transfer the precursor solution to a 100 mL autoclave, place it in an oven and hydrothermally react at 180 °C for 18 h; naturally cool to room temperature and then filter, wash the filter cake with deionized water and absolute ethanol 3 times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain green Cu-ZnS powder.

[0024] (3) Preparation of Cu-ZnS / ZnO

[0025] Weigh 0.25 g of Cu-ZnS powder into a 50 mL beaker, add 30 mL of deionized water, ultrasonically stir for 3 min to obtain a green suspension, add ZnO powder with a mass ratio of 5 wt%, and then ultrasonically stir for 30 min to obtain a uniformly dispersed precursor solution; transfer the precursor solution to a 50 mL reaction kettle, place it in an oven and hydrothermally react at 180 °C for 18 h; naturally cool to room temperature and then filter, wash the filter cake with deionized water and absolute ethanol 3 times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain the Cu-ZnS / ZnO photocatalytic material (CSO-5).

[0026] Example 2

[0027] A preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO is as follows:

[0028] (1) The same as (1) in Example 1.

[0029] (2) The same as (2) in Example 1.

[0030] (3) Preparation of Cu-ZnS / ZnO

[0031] Weigh 0.25 g of Cu-ZnS powder into a 50 mL beaker, add 30 mL of deionized water, and ultrasonicate for 3 min to obtain a green suspension. After adding ZnO powder with a mass ratio of 10 wt%, ultrasonicate for 30 min to obtain a uniformly dispersed precursor solution; transfer the precursor solution to a 50 mL autoclave, place it in an oven and carry out hydrothermal reaction at 180 °C for 18 h; after natural cooling to room temperature, filter, wash the filter cake with deionized water and absolute ethanol 3 times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain the Cu-ZnS / ZnO photocatalytic material (CSO-10).

[0032] Example 3

[0033] A preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO is as follows:

[0034] (1) The same as (1) in Example 1.

[0035] (2) The same as (2) in Example 1.

[0036] (3) Preparation of Cu-ZnS / ZnO

[0037] Weigh 0.25 g of Cu-ZnS powder into a 50 mL beaker, add 30 mL of deionized water, and ultrasonicate for 3 min to obtain a green suspension. After adding ZnO powder with a mass ratio of 15 wt%, ultrasonicate for 30 min to obtain a uniformly dispersed precursor solution; transfer the precursor solution to a 50 mL autoclave, place it in an oven and carry out hydrothermal reaction at 180 °C for 18 h; after natural cooling to room temperature, filter, wash the filter cake with deionized water and absolute ethanol 3 times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain the Cu-ZnS / ZnO photocatalytic material (CSO-15).

[0038] Example 4

[0039] A preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO is as follows:

[0040] (1) The same as (1) in Example 1.

[0041] (2)Same as (2) in Example 1.

[0042] (3)Preparation of Cu-ZnS / ZnO

[0043] Weigh 0.25 g of Cu-ZnS powder into a 50 mL beaker, add 30 mL of deionized water, and ultrasonicate for 3 min to obtain a green suspension. After adding ZnO powder with a mass ratio of 20 wt%, ultrasonicate for 30 min to obtain a uniformly dispersed precursor solution; transfer the precursor solution to a 50 mL autoclave, place it in an oven, and carry out hydrothermal reaction at 180 °C for 18 h; after natural cooling to room temperature, filter, wash the filter cake 3 times with deionized water and anhydrous ethanol respectively, place it in an oven and dry at 60 °C for 12 h, and obtain the Cu-ZnS / ZnO photocatalytic material (CSO-20) after grinding.

[0044] Experimental results

[0045] The composite photocatalytic material Cu-ZnS / ZnO (CSO-10) prepared in Example 2 has the best catalytic hydrogen production performance. For the convenience of comparison, a ZnS sample was prepared. The preparation method of ZnS is to not add Cu(NO3)2·3H2O in step (2) of Example 1.

[0046] The XRD pattern of ZnS is as Figure 1 (f) shown. Characteristic diffraction peaks of ZnS can be observed at diffraction angles 2θ of 28.9°, 48.1°, and 57.1°, corresponding to the (111), (220), and (311) crystal planes of the standard card (PDF#97-006-7790) respectively, and the diffraction peaks are sharp without impurity peaks, indicating that the prepared ZnS has good crystallinity.

[0047] The XRD pattern of Cu-ZnS ( Figure 1 (e)) can obviously observe the characteristic peaks of ZnS, and a diffraction peak belonging to CuS is found near 2θ of 46.053°, indicating that the Cu-ZnS composite photocatalyst is successfully prepared.

[0048] The XRD diffraction pattern of the composite photocatalytic material is as Figure 1 (a) to Figure 1 (d) shown, having all the peaks of the binary composite sample Cu-ZnS, and the positions of each diffraction peak correspond to those of the ZnS sample. At the same time, characteristic crystal plane peaks (100), (002), (101), (103), (112), and (201) of ZnO are observed, and no impurity peaks appear in all samples, indicating that each phase in the composite sample can be well combined and stably coexist, and Cu-ZnS / ZnO is successfully prepared.

[0049] The SEM patterns of ZnS, Cu-ZnS, and CSO-10 are as Figure 2As shown in the figure. Figures (a) and (b) are SEM images of pure-phase ZnS and Cu-ZnS, respectively. It can be observed that most of the ZnS is in the form of round small balls with different sizes, smooth surfaces, and relatively uniform distribution, while CuS presents a flaky structure attached to the surface of ZnS; Figure 2 (c) and (d) are SEM images of the CSO-10 sample. It is observed that the ternary sample retains the nanospheres and flaky structures in the binary composite sample Cu-ZnS, indicating that the addition of ZnO does not destroy the original morphology of Cu-ZnS. Compared with the binary composite spectrum, it can be observed that ZnO nanoblocks are scattered around, increasing the surface area.

[0050] The results of the photocatalytic hydrogen production experiment are as Figure 3 shown. Under the irradiation of a 300W xenon lamp simulating sunlight, the prepared 0.05g composite photocatalytic material CSO-10 has the best photocatalytic hydrogen production effect. The hydrogen production amount reaches 2645.1 μmol in 3 hours, and the corresponding hydrogen production rate is 17000 μmol·g -1 ·h -1 .

Claims

1. A preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO, characterized in that, The specific steps are as follows: (1) Preparation of ZnO Weigh 0.56 g of Zn(CHCOO)2·2H2O, 0.4 g of polyvinylpyrrolidone, and 0.5 g of urea into a 100 mL beaker, add 60 mL of ethylene glycol, and magnetically stir for 1 h to obtain a mixed solution; transfer the mixed solution to a 100 mL autoclave, place it in an oven, and carry out hydrothermal reaction at 180 °C for 2 h; naturally cool to room temperature, filter, wash the filter cake with deionized water and absolute ethanol three times respectively, place it in a vacuum oven and dry at 60 °C for 12 h, and grind to obtain pale yellow ZnO powder; (2) Preparation of Cu-ZnS Weigh 1.317 g of Zn(CHCOO)2·2H2O and 0.4568 g of thiourea into a 100 mL beaker, add 60 mL of deionized water, magnetically stir for 30 min to dissolve, then add 0.0725 g of Cu(NO3)2·3H2O, and continue to stir for 1 h to obtain a transparent Cu-ZnS precursor solution; transfer the precursor solution to a 100 mL autoclave, place it in an oven, and carry out hydrothermal reaction at 180 °C for 18 h; naturally cool to room temperature and then filter, wash the filter cake with deionized water and absolute ethanol three times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain green Cu-ZnS powder; (3) Preparation of Cu-ZnS / ZnO Weigh 0.25 g of Cu-ZnS powder into a 50 mL beaker, add 30 mL of deionized water, ultrasonically stir for 3 min to obtain a green suspension, add ZnO powder with a mass ratio of 5 wt% - 20 wt%, and then ultrasonically stir for 30 min to obtain a uniformly dispersed precursor solution; transfer the precursor solution to a 50 mL reaction kettle, place it in an oven and carry out hydrothermal reaction at 180 °C for 18 h; naturally cool to room temperature and then filter, wash the filter cake with deionized water and absolute ethanol three times respectively, place it in an oven and dry at 60 °C for 12 h, and grind to obtain the Cu-ZnS / ZnO photocatalytic material.

2. The preparation method of a novel photocatalytic hydrogen production material Cu-ZnS / ZnO according to claim 1, characterized in that, Effectively improves the photocatalytic hydrogen production activity of ZnS.

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