阅读说明：本技术 一种含有s空位的z型异质结光催化剂的制备方法 (Preparation method of Z-type heterojunction photocatalyst containing S vacancies ) 是由 夏盛杰 张冠华 倪哲明 谢波 于 2021-08-26 设计创作，主要内容包括：一种含有S空位的BiVO-(4)/S-(V)-ZnIn-(2)S-(4)Z型异质结光催化剂的制备方法：将甘油加入pH＝2～2.5的HCl水溶液中,搅拌10～20min,得到溶液A；在所得溶液A中加入ZnCl-(2)、InCl-(3)·4H-(2)O、硫代乙酰胺和BiVO-(4),超声15～30min,再搅拌10～20min,得到溶液B；将所得溶液B在80～85℃下搅拌反应120～150min,之后经离心,洗涤,干燥,得到目标产物；本发明制备方法简单,只需要简单的水热合成,合成的BiVO-(4)/S-(V)-ZnIn-(2)S-(4)比纯相BiVO-(4)和纯相ZnIn-(2)S-(4)表现出更高的光吸收性能和载流子分离效率,并表现出高效的光催化合成氨活性。(BiVO containing S vacancy 4 /S V ‑ZnIn 2 S 4 The preparation method of the Z-type heterojunction photocatalyst comprises the following steps: adding glycerol into an HCl aqueous solution with the pH value of 2-2.5, and stirring for 10-20 min to obtain a solution A; ZnCl is added into the obtained solution A 2 、InCl 3 ·4H 2 O, thioacetamide and BiVO 4 Performing ultrasonic treatment for 15-30 min, and stirring for 10-20 min to obtain a solution B; stirring the obtained solution B at 80-85 ℃ for reaction for 120-150 min, and then centrifuging, washing and drying to obtain a target product; the preparation method is simple, and only simple hydrothermal synthesis is needed, so that the synthesized BiVO 4 /S V ‑ZnIn 2 S 4 Relatively pure phaseBiVO 4 And pure phase ZnIn 2 S 4 Exhibits higher light absorption performance and carrier separation efficiency, and exhibits high photocatalytic ammonia synthesis activity.)

1. BiVO containing S vacancy₄/S_V-ZnIn₂S₄The preparation method of the Z-type heterojunction photocatalyst is characterized by comprising the following steps:

(1) adding glycerol into an HCl aqueous solution with the pH value of 2-2.5, and stirring for 10-20 min to obtain a solution A;

(2) ZnCl is added into the solution A obtained in the step (1)₂、InCl₃·4H₂O, thioacetamide and BiVO₄Performing ultrasonic treatment for 15-30 min, and stirring for 10-20 min to obtain a solution B;

(3) stirring the solution B obtained in the step (2) at 80-85 ℃ for reaction for 120-150 min, and then centrifuging, washing and drying to obtain the BiVO containing S vacancy₄/S_V-ZnIn₂S₄A Z-type heterojunction photocatalyst.

2. BiVO containing S vacancies as claimed in claim 1₄/S_V-ZnIn₂S₄The preparation method of the Z-type heterojunction photocatalyst is characterized in that in the solution A in the step (1), the volume fraction of glycerol is 20-25%, and the volume fraction of HCl aqueous solution is 75-80%.

3. BiVO containing S vacancies as claimed in claim 1₄/S_V-ZnIn₂S₄The preparation method of the Z-type heterojunction photocatalyst is characterized in that in the step (2), ZnCl is adopted₂、InCl₃·4H₂The mass ratio of O to thioacetamide is 1: 1: 2.

4. BiVO containing S vacancies as claimed in claim 1₄/S_V-ZnIn₂S₄The preparation method of the Z-type heterojunction photocatalyst is characterized in that in the step (2), ZnCl is adopted₂The concentration of the solution B in the solution B is 0.05-0.075 mmol/mL.

5. BiVO containing S vacancies as claimed in claim 1₄/S_V-ZnIn₂S₄The preparation method of the Z-type heterojunction photocatalyst is characterized in that in the step (2), the BiVO₄The concentration of the B-containing solution in the B-containing solution is 2.5-5 mg/mL.

Technical Field

The invention relates to BiVO containing S vacancy₄/S_V-ZnIn₂S₄A preparation method of a Z-type heterojunction photocatalyst.

Background

Ammonia (NH)₃) As one of the largest industrial synthetic chemicals in the world, it has been widely used in the fields of agriculture, chemical industry, medicine, and the like. The current industrial synthesis of ammonia relies entirely on the highly energy intensive Haber-Bosch process. Due to N₂The natural inertness of the molecule, the Haber-Bosch process, requires reactions under severe conditions of high temperature (400 ℃) and high pressure (20-40 MPa). The technology of synthesizing ammonia by photocatalysis is expected to become a new method for replacing Haber-Bosch process. This is because the process uses inexhaustible solar energy and water to provide energy for the synthesis of ammonia. However, intrinsic photocatalysts tend to exhibit poor ammonia synthesis activity due to their high carrier recombination efficiency. In this regard, we need to modify the intrinsic photocatalyst appropriately to obtain more photogenerated electrons to participate in the ammonia synthesis reaction. A large number of researches show that the construction of the heterojunction is a method for effectively improving the separation efficiency of intrinsic semiconductor carriers and generating more photon-generated electrons. Particularly Z-type heterojunction system, which can generate a large amount of photogenerated carriers and simultaneously maximally improve the oxidation/reduction potential of the heterojunction system, thereby ensuring the prerequisite of reaction thermodynamics, which is a characteristic that other types of heterojunction do not have.

However, Z-type heterojunctions have been reported to catalyze and synthesize ammonia, but the activity of ammonia synthesis is still low. The fundamental reason is that the photogenerated electrons in the Z-type heterojunction are injected into N₂The efficiency of the molecule is very low. Therefore, the key to solving this bottleneck is how to build a large number of effective active sites on the surface of the active component of the Z-type heterojunction catalyst, in the heterojunction system and N₂An effective electron transfer bridge is established between reduction reaction systems, and a large amount of photo-generated electrons generated by the Z-shaped heterojunction are effectively transmitted to N₂And (4) carrying out reduction reaction. Numerous studies report that defect engineering is a very effective means of increasing the surface active sites of catalysts. Researchers have developed a large number of lights containing defectsThe catalytic material being used in reactions for photocatalytic synthesis of ammonia, e.g. Bi containing oxygen defects₅O₇Br and TiO₂Zn with S defects_0.1Sn_0.1Cd_0.8S and MoS₂. The research finds that the defect site can effectively adsorb N₂Molecules and photo-generated electrons from the catalyst to N₂And (4) transferring the molecules.

Therefore, if a vacancy is constructed in the active component in the Z-type heterojunction, namely the vacancy is used as a bridge for electron transfer, the photoproduction electrons can be effectively promoted from the surface of the catalyst to N₂The injection of molecules improves the activity of photocatalytic synthesis of ammonia. In this system, the Z-type heterojunction is N₂The reduction provides a driving force, namely a large amount of photo-generated electrons are generated; and the vacancy is photo-generated electron to N₂The injection provides a channel.

Disclosure of Invention

The invention aims to provide BiVO containing S vacancy₄/S_V-ZnIn₂S₄A preparation method of a Z-type heterojunction photocatalyst. BiVO is prepared by a hydrothermal method₄Then ZnIn is put into₂S₄The nano-sheet grows to BiVO in situ₄The BiVO containing S vacancy can be prepared and obtained₄/S_V-ZnIn₂S₄A Z-type heterojunction photocatalyst.

The technical scheme of the invention is as follows:

BiVO containing S vacancy₄/S_V-ZnIn₂S₄The preparation method of the Z-type heterojunction photocatalyst comprises the following steps:

(1) adding glycerol into an HCl aqueous solution with the pH value of 2-2.5, and stirring for 10-20 min to obtain a solution A;

in the solution A, the volume fraction of glycerol is 20-25%, and the volume fraction of HCl aqueous solution is 75-80%;

(2) ZnCl is added into the solution A obtained in the step (1)₂、InCl₃·4H₂O, thioacetamide and BiVO₄Performing ultrasonic treatment for 15-30 min, and stirring for 10-20 min to obtain a solution B;

the ZnCl₂、InCl₃·4H₂The mass ratio of O to thioacetamide is 1: 1: 2;

the ZnCl₂The concentration of the mixed solution in the solution B is 0.05-0.075 mmol/mL;

the BiVO₄The concentration of the solution B in the solution B is 2.5-5 mg/mL;

(3) stirring the solution B obtained in the step (2) at 80-85 ℃ for reaction for 120-150 min, centrifuging, washing (with deionized water), and drying to obtain the BiVO containing S vacancy₄/S_V-ZnIn₂S₄A Z-type heterojunction photocatalyst;

the drying is carried out in a vacuum drying oven at the temperature of 60-80 ℃ for 8-12 h.

In the present invention, the "solution a" and "solution B" have no special meaning, and the labels "a" and "B" are only used to distinguish the solutions obtained in the different steps.

BiVO containing S vacancy prepared by the invention₄/S_V-ZnIn₂S₄The Z-type heterojunction photocatalyst can be applied to the reaction of synthesizing ammonia by photocatalysis.

The invention has the advantages that:

the preparation method is simple and only needs simple hydrothermal synthesis. Synthetic BiVO₄/S_V-ZnIn₂S₄BiVO of relatively pure phase₄And pure phase ZnIn₂S₄Exhibits higher light absorption performance and carrier separation efficiency, and exhibits high photocatalytic ammonia synthesis activity.

Drawings

FIG. 1 is BiVO of example 1₄XRD pattern of (a).

FIG. 2 shows ZnIn in example 2₂S₄XRD pattern of (a).

FIG. 3 is BiVO in example 3₄/S_V-ZnIn₂S₄XRD pattern of (a).

FIG. 4 shows BiVO in example 1₄SEM image of (d).

FIG. 5 shows ZnIn in example 2₂S₄SEM image of (d).

FIG. 6 shows an embodiment3 BiVO₄/S_V-ZnIn₂S₄SEM image of (d).

FIG. 7 is BiVO in example 3₄/S_V-ZnIn₂S₄Mapping graph of (1).

FIG. 8 shows BiVO in examples 1, 2 and 3₄、ZnIn₂S₄And BiVO₄/S_V-ZnIn₂S₄Ultraviolet-visible diffuse reflectance spectrum of.

FIG. 9 shows ZnIn in examples 2 and 3₂S₄And BiVO₄/S_V-ZnIn₂S₄Electron paramagnetic resonance characterization of (a).

FIG. 10 shows BiVO in examples 1, 2 and 3₄、ZnIn₂S₄And BiVO₄/S_V-ZnIn₂S₄Photocurrent characterization plots.

FIG. 11 shows BiVO in examples 1, 2 and 3₄、ZnIn₂S₄And BiVO₄/S_V-ZnIn₂S₄The data of the activity of the photocatalytic synthesis of ammonia.

Detailed Description

The invention is further described below by means of specific examples, without the scope of protection of the invention being limited thereto.

Example 1:

BiVO₄the preparation method comprises the following steps:

to a solution of 50mL of diluted HNO₃Adding Bi (NO) into (2mol/L) beaker₃)₃·5H₂O (2.370g, 6mmol) and NH₄VO₃(0.7019g, 6mmol) and stirred for 10 min. Ammonia was then added dropwise to the solution until the pH was 2. Then transferring the mixture into a teflon reaction kettle, reacting for 120min at 180 ℃, centrifuging, washing, and drying in a vacuum drying oven at 60 ℃ for 24h to obtain BiVO₄。

Example 2:

ZnIn₂S₄the preparation method comprises the following steps:

reacting ZnCl₂(0.2726g，2mmol)、InCl₃·4H₂O (1.1727g, 4mmol), thioacetamide (0.6024g, 8 mmol)l) dispersed ultrasonically in 20mL of ethylene glycol and stirred continuously for 60 min. The mixture was then poured into a teflon autoclave and kept heated at 80 ℃ for 120 min. Naturally cooling to room temperature after the reaction is finished, washing the obtained precipitate for 3 times by using absolute ethyl alcohol, and then drying in a vacuum drying oven at 60 ℃ overnight, wherein the sample is recorded as ZnIn₂S₄。

Example 3:

BiVO containing S vacancy₄/S_V-ZnIn₂S₄The preparation method comprises the following steps:

add 8mL of glycerol to 32mL of HCl solution at pH 2.5 and continue stirring for 10min, denoted as solution a. Then adding the solution into ZnCl₂(0.2726g，2mmol)、InCl₃·4H₂O (1.1727g, 2mmol), thioacetamide (0.3012g, 4mmol) and BiVO₄(0.1g), stir for another 10min with ultrasound for 15min, and record as solution B. Stirring the solution B in a water bath at 80 ℃ for reaction for 120min, centrifugally washing, and drying in a vacuum drying oven at 60 ℃ overnight to finally obtain the BiVO containing S vacancy₄/S_V-ZnIn₂S₄Z-type heterojunction photocatalyst, noted BiVO₄/S_V-ZnIn₂S₄。

Characterization of XRD

A Shimadzu XRD-6000X-ray powder diffractometer is adopted, wherein the characteristic parameters are set as follows: cu target, Kalpha ray, lambda of 0.15405nm, angle range of 5-70 deg, and scanning speed of 4 deg/min.

As can be seen from FIG. 1, the synthesized BiVO₄The crystal form of the crystal is consistent with a monoclinic phase (JCPDS Card NO.14-0688), and a diffraction peak at a diffraction angle of about 18.7 degrees corresponds to a monoclinic phase BiVO₄The diffraction peak at a diffraction angle of about 30.6 ° corresponds to the (040) crystal plane.

As can be seen from FIG. 2, the characteristic diffraction peaks at diffraction angles of about 21.2 °, 27.6 °, 29.7 °, 39.4 °, 47.3 °, 51.7 ° and 55.8 ° correspond to ZnIn in the hexagonal phase, respectively₂S₄(006), (102), (104), (108), (110), (116) and (202) crystal plane (JCPDS No.72-0773), which shows ZnIn₂S₄The successful preparation.

Furthermore, BiVO is evident in FIG. 3₄/S_V-ZnIn₂S₄ZnIn appears in XRD pattern of photocatalyst at the same time₂S₄Characteristic peak and BiVO₄And no impurity peak was found, indicating that they are two-phase composites.

SEM and mapping characterization

The morphology of the catalyst was characterized using a scanning electron microscope (Gemini 500, Zeiss, Germany) with an acceleration voltage of 15 kV.

FIG. 4 is BiVO₄From which it can be seen that the morphology is a decahedral-like structure.

FIG. 5 shows ZnIn₂S₄From which the structure is clearly seen as a sheet-stacked structure.

FIG. 6 is BiVO₄/S_V-ZnIn₂S₄SEM image of the composite material, from which ZnIn can be clearly seen₂S₄The nano sheets are uniformly and densely coated on the BiVO₄And forming a 3D core-shell structure with a layered structure.

FIG. 7 is BiVO₄/S_V-ZnIn₂S₄Mapping characterization of the composite material, it can be seen from the figure that the composite material is composed of elements of Zn, S, V, In, Bi and O, which is the same as the expected result.

Characterization of ultraviolet-visible diffuse reflectance

The ultraviolet-visible diffuse reflection spectrum characterization instrument is Shimadzu-2600, the absorption performance of the material to light is analyzed, and BaSO is used in the test₄For background, the scan range was 200 and 800 nm.

FIG. 8 is BiVO₄、ZnIn₂S₄And BiVO₄/S_V-ZnIn₂S₄Ultraviolet-visible diffuse reflectance spectrum of. As can be seen from the figure, pure ZnIn₂S₄And pure BiVO₄The absorption edges of (a) are about 500nm and 540nm, respectively, which is consistent with the results reported previously. When the two compounds to form BiVO₄/S_V-ZnIn₂S₄When the photocatalyst is compounded, its ultraviolet-visible lightThe absorption intensity of the region is significantly enhanced.

Electron paramagnetic resonance characterization

FIG. 9 shows ZnIn₂S₄And BiVO₄/S_V-ZnIn₂S₄Results of Electron Paramagnetic Resonance (EPR) test (see (1)). In ZnIn₂S₄Signal without any empty bit, and BiVO₄/S_V-ZnIn₂S₄The EPR signal of S vacancy appears when g is 2.003, which indicates that S vacancy exists in the constructed core-shell heterojunction.

Photocurrent characterization

The photocurrent curves of the samples were performed using the Zahner PP211(Germany) electrochemical workstation standard three-electrode test system. In a standard three-electrode system, a 0.5M sodium sulfate solution is used as an electrolyte, a Saturated Calomel Electrode (SCE) is used as a reference electrode, a platinum wire is used as a counter electrode, and a sample mold film coated on Indium Tin Oxide (ITO) glass is used as a working electrode. A5 mg sample of the powder was weighed, dispersed in 2mL of ethanol solution, sonicated for 30 minutes to form a homogeneous suspension, which was then added dropwise to ITO glass (1X2 cm)²) The above. The above working electrode was dried in an oven at 80 ℃ for 1 hour, and then subjected to a photoelectric test. The light source used for the electrochemical test was a 300W xenon lamp with a 20 second light interval (20 s on and 20s off). The surface photovoltage test equipment consists of a locking amplifier (SR830) photointerrupter, and monochromatic light is provided by a 500W xenon lamp through a monochromatic grating instrument.

FIG. 10 is BiVO₄、ZnIn₂S₄And BiVO₄/S_V-ZnIn₂S₄The photocurrent of (c) characterizes the result. As can be seen from the figure, BiVO of pure phase₄And ZnIn₂S₄Shows relatively low photocurrent density, and the current density is obviously enhanced after the two are compounded, which indicates that BiVO₄/S_V-ZnIn₂S₄The composite material has higher electron (e)^-) And a cavity (h)⁺) The separation efficiency.

Photocatalytic synthesis of ammonia test

At room temperature and N₂And carrying out a photocatalytic synthesis ammonia experiment in the atmosphere. In the experiment, 50mg of catalystThe reagent was dispersed in 200mL of ultrapure water and sonicated for 15 min. And pouring the suspension into a quartz reactor (a cover made of quartz material and the reactor are sealed by a sealing ring to prevent air leakage). Introducing N under dark and light-proof conditions₂(99.999%, 200mL/min) was bubbled for 30min to remove air from the system. Subsequently, a 300W Xe lamp (PL-X300D, lambda > 400nm, light intensity of 3.82W/cm)²) Photocatalytic experiments were performed.

Detection of NH in water using Nassler reagent₄ ⁺The method comprises the following specific operations: 10mL of the reaction solution was collected by syringe every 15min and immediately centrifuged (8000rpm, 10min), and the centrifuged solution was filtered through a 0.22 μm filter into a 10mL cuvette. Then, 200. mu.L of a sodium potassium tartrate solution was added to the cuvette, and after thorough mixing, 300. mu.L of a Nessler reagent was added to the above solution. After 15 minutes of mixing, the NH in the solution was measured by a Shimadzu UV-2600 spectrometer at λ 420nm₄ ⁺And (4) content.

Figure 11 shows the photocatalytic synthesis of ammonia test results. As can be seen, as the illumination time is prolonged, BVO, ZIS and BVO/S in different proportions_V-ZIS NH of composite material₄ ⁺The production amount steadily increased. BiVO₄/S_V-ZnIn₂S₄The synthetic ammonia rate of the composite photocatalyst is obviously higher than that of pure phase BiVO₄And ZnIn₂S₄NH of which₄ ⁺The generation rate reaches 58.5 mu mol g^-1·h^-1. This suggests that the formation of heterojunctions and S vacancies can promote the participation of more photogenerated electrons in the photocatalytic N₂Reduction reaction, increase NH₄ ⁺The rate of generation of.