MnIn2S4-moO2 heterojunction photocatalyst and preparation method thereof

Abstract

The application discloses a MnIn2S4-MoO2 heterojunction photocatalyst and a preparation method thereof, and specifically relates to the following steps: preparing MnIn2S4 through a hydrothermal method; activating the prepared MnIn2S4 by using sodium borohydride as an activator; mixing the activated MnIn2S4 with a MoO2 precursor, and preparing the MnIn2S4-MoO2 heterojunction photocatalyst through a hydrothermal method and a calcination method; the MnIn2S4 and the MoO2 in the prepared MnIn2S4-MoO2 heterojunction photocatalyst are bonded through S-Mo bonds, and have a close coupling degree; the covalent bond greatly improves the photogenerated carrier separation efficiency of the heterojunction photocatalyst, and the obtained MnIn2S4-MoO2 heterojunction has excellent photocatalytic performance; the method has simple process, mild reaction conditions, and no environmental pollution, and is easy to be industrialized.

Description

TECHNICAL FIELD

[0001] The application relates to the field of photocatalysts, in particular to a MnIn2S4-MoO2 heterojunction photocatalyst and a preparation method thereof. BACKGROUND

[0002] Energy and environmental problems are two challenges faced by mankind today, and semiconductor-based photocatalytic technology is expected to achieve a breakthrough in the above problems, so the research and development of the technology have become a focus in the related field in recent decades. However, a large number of studies have shown that the energy band width and the lifetime of photo-generated carriers of the semiconductor catalyst are key factors affecting the catalytic efficiency and application of the photocatalyst. The wider the energy band of the semiconductor, the weaker the visible light response ability and the lower the solar light utilization rate; the photo-generated electrons and holes generated by the excitation of the elemental semiconductor are prone to recombination due to the homogeneity of the elemental semiconductor, which leads to a decrease in the photo quantum efficiency and affects the photocatalytic effect, thereby limiting the industrial application thereof.

[0003] In recent years, ternary metal chalcogenide semiconductors have attracted attention from researchers in the field due to their narrow energy band width and excellent visible light activity. Among them, the band gap of MnIn2S4 is about 2.2 eV, and it has good visible light response ability. In addition, the assembly of MnIn2S4 and other semiconductor materials to form a heterojunction can inhibit the recombination of photo-generated electrons and holes. MoO2 is a kind of metal oxide semiconductor, which has good electrical conductivity and chemical stability, and can effectively capture electrons, thereby promoting the separation of photo-generated electrons and holes. Moreover, the energy band potential of MnIn2S4 and MoO2 is staggered, and a transmission path for electrons and holes can be formed between them. However, the existing heterojunction photocatalytic materials have problems such as poor coupling degree between heterojunction materials, low transmission efficiency of photo-generated carriers between heterojunctions, and complex preparation process of heterojunction catalysts. SUMMARY

[0004] The purpose of the present application is to provide a MnIn2S4-MoO2 heterojunction photocatalyst and a preparation method thereof. The MnIn2S4-MoO2 heterojunction photocatalyst prepared by the method is tightly combined between MnIn2S4 and MoO2 through S-Mo bonds. The chemical bond provides a channel for the transmission of photo-generated carriers between heterojunctions, inhibits the recombination of photo-generated electrons and holes, and thus significantly improves the photocatalytic activity of the catalyst.

[0005] The preparation method of the MnIn2S4-MoO2 heterojunction photocatalyst provided by the present application comprises the following steps:

[0006] S1. preparing a MnIn2S4 catalyst by a hydrothermal method;

[0007] S2. activating the prepared MnIn2S4 with sodium borohydride as an activator;

[0008] S3. The activated MnIn2S4 is mixed with MoO2 precursor to prepare MnIn2S4-MoO2 heterojunction photocatalyst by hydrothermal method and calcination method.

[0009] In step S1, the hydrothermal method is specifically as follows: MnCl2·4H2O, InCl3·4H2O and thioacetamide are added into ethanol solution to form a uniform mixture by stirring; the mixture is moved into a reaction kettle to perform hydrothermal reaction, and the obtained product is washed and dried to obtain MnIn2S4 photocatalyst. The molar ratio of MnCl2·4H2O, InCl3·4H2O and thioacetamide is 1:2:4, the amount ratio of thioacetamide and ethanol is 4-8 mmol: 50-80 mL, and the hydrothermal reaction temperature is 110-200°C, and the reaction time is 8-48 h.

[0010] In step S2, the activation is specifically as follows: the MnIn2S4 photocatalyst prepared in step S1 is added into sodium borohydride ethanol solution to perform heating reflux reaction under stirring, and the obtained product is washed and dried to obtain activated MnIn2S4 photocatalyst. The amount ratio of MnIn2S4, sodium borohydride and ethanol is 100-500 mg: 20-150 mg: 40-60 mL, the reaction temperature is 30-60°C, and the reaction time is 1.5-5 h.

[0011] In step S3, the hydrothermal method and calcination method are specifically as follows: MoCl5, acetic acid and activated MnIn2S4 prepared in step S2 are added into ethanol solution to form a uniform mixture by stirring; the mixture is moved into a reaction kettle to perform hydrothermal reaction, and the obtained product is washed and dried and then placed in a tube furnace to perform calcination, thereby preparing MnIn2S4-MoO2 heterojunction photocatalyst. The amount ratio of MoCl5, acetic acid, activated MnIn2S4 and ethanol is 2-8 mmol: 1-3 mL: 1-10 mmol: 50-80 mL, the hydrothermal reaction time is 12-48 h, the hydrothermal reaction temperature is 100-200°C, the calcination temperature is 200-500°C, the calcination atmosphere is argon, and the calcination time is 30-120 min.

[0012] The application prepares a MnIn2S4 single-phase photocatalyst by a hydrothermal method, then activates the MnIn2S4 by sodium borohydride to increase the unsaturated S vacancies in the crystal phase structure of the MnIn2S4, and then reacts the activated MnIn2S4 with a MoO2 precursor by a hydrothermal method and a calcination method to prepare a MnIn2S4-MoO2 heterojunction photocatalyst, in which the unsaturated S atoms in the structure of the activated MnIn2S4 combine with Mo atoms in the MoO2 to form S-Mo bonds, so that the MnIn2S4 and the MoO2 in the heterojunction form a tight chemical bond coupling, which can effectively promote the separation of photo-generated electrons and holes of the heterojunction catalyst, and the photocatalytic activity is significantly improved.

[0013] Compared with the prior art, the application has the following remarkable advantages:

[0014] (1) The MnIn2S4-MoO2 heterojunction photocatalyst is prepared for the first time, the preparation method of the catalyst is simple, the reaction conditions are mild, the requirement for equipment is low, the environment is not polluted, and the industrialized production is easy.

[0015] (2) The MnIn2S4-MoO2 heterojunction photocatalyst prepared in the application is coupled between the MnIn2S4 and the MoO2 through S-Mo bonds, has a tight coupling degree, and the S-Mo bonds can promote the transmission of photo-generated carriers between the heterojunction materials, inhibit the recombination of electrons and holes, and significantly enhance the photocatalytic activity.

[0016] (3) The MnIn2S4-MoO2 heterojunction photocatalyst prepared in the application has high visible light activity, and has high practical value and application prospect in the field of environmental governance. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is an XRD characterization graph of the MnIn2S4-MoO2 heterojunction photocatalyst prepared in Example 3.

[0018] Figure 2 (a) and (b) are respectively S2p high-resolution XPS characterization graphs of the MnIn2S4 / MoO2 heterojunction photocatalyst prepared in Comparative Example 1 and the MnIn2S4-MoO2 photocatalyst prepared in Example 3.

[0019] Figure 3 The figure is a photocurrent response graph of the MnIn2S4-MoO2 photocatalyst prepared in Example 3 and the MnIn2S4 / MoO2 heterojunction photocatalyst prepared in Comparative Example 1.

[0020] Figure 4Electrochemical impedance plots of the MnIn2S4-MoO2 heterojunction photocatalyst prepared in Example 3 and the MnIn2S4 / MoO2 photocatalyst prepared in Comparative Example 1.

[0021] Figure 5 A comparison plot of the photocatalytic activity of the MnIn2S4-MoO2 heterojunction photocatalyst prepared in Example 3 and the MnIn2S4 / MoO2 photocatalyst prepared in Comparative Example 1. DETAILED DESCRIPTION

[0022] Example 1

[0023] 1 mmol of MnCl2·4H2O, 2 mmol of InCl3·4H2O and 4 mmol of thioacetamide were added to a 50 mL ethanol solution, stirred for 30 min to form a uniform mixture; the mixture was transferred to a reaction kettle and subjected to hydrothermal reaction at 110°C for 8 h, and the obtained product was washed with deionized water and anhydrous ethanol and dried to obtain a MnIn2S4 photocatalyst.

[0024] 100 mg of the above-prepared MnIn2S4 and 20 mg of sodium borohydride were added to a 40 mL ethanol solution, heated to reflux at 30°C under stirring for 1.5 h, and the obtained product was washed with deionized water and anhydrous ethanol and dried to obtain an activated MnIn2S4 photocatalyst.

[0025] 2 mmol of the above-prepared activated MnIn2S4, 3 mmol of MoCl5 and 1.5 mL of acetic acid were added to a 55 mL ethanol solution, stirred for 30 min to form a uniform mixture; the mixture was transferred to a reaction kettle and subjected to hydrothermal reaction at 100°C for 12 h, and the obtained product was calcined in a tube furnace at 200°C under argon atmosphere for 30 min to obtain a MnIn2S4-MoO2 heterojunction photocatalyst.

[0026] Example 2

[0027] 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added to a 60 mL ethanol solution, stirred for 30 min to form a uniform mixture; the mixture was transferred to a reaction kettle and subjected to hydrothermal reaction at 140°C for 16 h, and the obtained product was washed with deionized water and anhydrous ethanol and dried to obtain a MnIn2S4 photocatalyst.

[0028] 200 mg of the above-prepared MnIn2S4 and 60 mg of sodium borohydride were added to a 45 mL ethanol solution, heated to reflux at 45°C under stirring for 2 h, and the obtained product was washed with deionized water and anhydrous ethanol and dried to obtain an activated MnIn2S4 photocatalyst.

[0029] Into 60 mL of ethanol solution, 3 mmol of the above-prepared activated MnIn2S4, 6 mmol of MoCl5 and 2 mL of acetic acid were added, and stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 140°C for 18 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 300°C for 60 min in an argon atmosphere to prepare a MnIn2S4-MoO2 heterojunction photocatalyst.

[0030] Example 3

[0031] Into 70 mL of ethanol solution, 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 300°C for 60 min in an argon atmosphere to prepare a MnIn2S4 photocatalyst.

[0032] Into 50 mL of ethanol solution, 250 mg of the above-prepared MnIn2S4 and 70 mg of sodium borohydride were added, and subjected to reflux reaction at 50°C for 2.5 h under stirring; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 300°C for 60 min in an argon atmosphere to prepare an activated MnIn2S4 photocatalyst.

[0033] Into 70 mL of ethanol solution, 5 mmol of the above-prepared activated MnIn2S4, 6 mmol of MoCl5 and 2.5 mL of acetic acid were added, and stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 400°C for 60 min in an argon atmosphere to prepare a MnIn2S4-MoO2 heterojunction photocatalyst.

[0034] Example 4

[0035] Into 80 mL of ethanol solution, 2 mmol of MnCl2·4H2O, 4 mmol of InCl3·4H2O and 8 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 200°C for 48 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 300°C for 60 min in an argon atmosphere to prepare a MnIn2S4 photocatalyst.

[0036] Into 60 mL of ethanol solution, 350 mg of the above-prepared MnIn2S4 and 70 mg of sodium borohydride were added, and subjected to reflux reaction at 55°C for 4 h under stirring; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 300°C for 60 min in an argon atmosphere to prepare an activated MnIn2S4 photocatalyst.

[0037] Into 70 mL of ethanol solution, 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture. The mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h. The obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 450°C under argon atmosphere for 90 min to obtain a MnIn2S4 photocatalyst.

[0038] Comparative Example 1

[0039] Into 70 mL of ethanol solution, 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture. The mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h. The obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 450°C under argon atmosphere for 90 min to obtain a MnIn2S4 photocatalyst.

[0040] Into 70 mL of ethanol solution, 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture. The mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h. The obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 450°C under argon atmosphere for 90 min to obtain a MnIn2S4 photocatalyst.

[0041] Comparative Example 2

[0042] Into 70 mL of ethanol solution, 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture. The mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h. The obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 450°C under argon atmosphere for 90 min to obtain a MnIn2S4 photocatalyst.

[0043] Into 70 mL of ethanol solution, 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added, and stirred for 30 min to form a uniform mixture. The mixture was transferred into a reaction kettle, and subjected to hydrothermal reaction at 180°C for 24 h. The obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 450°C under argon atmosphere for 90 min to obtain a MnIn2S4 photocatalyst.

[0044] MnIn2S4-MoO2 heterojunction photocatalyst was prepared by adding 5 mmol of the above prepared activated MnIn2S4, 6 mmol of MoCl5 and 2.5 mL of acetic acid into 70 mL of an ethanol solution, stirring for 30 min to form a uniform mixture, transferring the mixture into a reaction kettle, and performing hydrothermal reaction at 180°C for 24 h. The obtained product was calcined in a tube furnace at 400°C for 60 min in an argon atmosphere after being washed with deionized water and anhydrous ethanol and dried.

[0045] Comparative Example 3

[0046] MnIn2S4 photocatalyst was prepared by adding 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide into 70 mL of an ethanol solution, stirring for 30 min to form a uniform mixture, transferring the mixture into a reaction kettle, and performing hydrothermal reaction at 180°C for 24 h.

[0047] Activated MnIn2S4 photocatalyst was prepared by adding 300 mg of the above prepared MnIn2S4 and 90 mg of sodium borohydride into 70 mL of an ethanol solution, and performing reflux reaction at 50°C for 2.5 h under stirring. The obtained product was washed with deionized water and anhydrous ethanol and dried.

[0048] MnIn2S4-MoO2 heterojunction photocatalyst was prepared by adding 5 mmol of the above prepared activated MnIn2S4, 6 mmol of MoCl5 and 2.5 mL of acetic acid into 70 mL of an ethanol solution, stirring for 30 min to form a uniform mixture, transferring the mixture into a reaction kettle, and performing hydrothermal reaction at 180°C for 24 h. The obtained product was calcined in a tube furnace at 400°C for 60 min in an argon atmosphere after being washed with deionized water and anhydrous ethanol and dried.

[0049] Comparative Example 4

[0050] MnIn2S4 photocatalyst was prepared by adding 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide into 70 mL of an ethanol solution, stirring for 30 min to form a uniform mixture, transferring the mixture into a reaction kettle, and performing hydrothermal reaction at 180°C for 24 h.

[0051] Activated MnIn2S4 photocatalyst was prepared by adding 200 mg of the above prepared MnIn2S4 and 50 mg of sodium borohydride into 70 mL of an ethanol solution, and performing reflux reaction at 50°C for 2.5 h under stirring. The obtained product was washed with deionized water and anhydrous ethanol and dried.

[0052] 5 mmol of the activated MnIn2S4 prepared above, 6 mmol of MoCl5 and 2.5 mL of acetic acid were added into 70 mL of an ethanol solution, stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and a hydrothermal reaction was performed at 120 °C for 24 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 400 °C for 60 min in an argon atmosphere to obtain a MnIn2S4-MoO2 heterojunction photocatalyst.

[0053] Comparative Example 5

[0054] 1.5 mmol of MnCl2·4H2O, 3 mmol of InCl3·4H2O and 6 mmol of thioacetamide were added into 70 mL of an ethanol solution, stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and a hydrothermal reaction was performed at 180 °C for 24 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 400 °C for 60 min in an argon atmosphere to obtain a MnIn2S4 photocatalyst.

[0055] 200 mg of the MnIn2S4 prepared above and 50 mg of sodium borohydride were added into 70 mL of an ethanol solution, heated to reflux at 50 °C for 2.5 h under stirring; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 400 °C for 60 min in an argon atmosphere to obtain an activated MnIn2S4 photocatalyst.

[0056] 5 mmol of the activated MnIn2S4 prepared above, 6 mmol of MoCl5 and 2.5 mL of acetic acid were added into 70 mL of an ethanol solution, stirred for 30 min to form a uniform mixture; the mixture was transferred into a reaction kettle, and a hydrothermal reaction was performed at 160 °C for 24 h; the obtained product was washed with deionized water and anhydrous ethanol, dried, and then calcined in a tube furnace at 400 °C for 60 min in an argon atmosphere to obtain a MnIn2S4-MoO2 heterojunction photocatalyst.

[0057] The methyl orange was used as a target pollutant to be removed, and the photocatalytic degradation abilities of the heterojunction photocatalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 5 on the methyl orange in water were measured.

[0058] The test method was as follows: 500 mL of a methyl orange solution having an initial concentration of 60 mg / L was taken, 0.5 g of the heterojunction photocatalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 5 was added, constant temperature oscillation was performed for 30 min, and then a photocatalytic degradation experiment was performed after visible light irradiation for 60 min after adsorption equilibrium was reached; after the experiment was completed, the solution was taken out, centrifuged, and then the concentration of the methyl orange in the supernatant was measured; and the removal rate was calculated according to the following formula e ​The concentration of methyl orange in the solution after the photocatalytic reaction (mg-L) is shown in Table 1.

[0059] Table 1 shows the removal rates of methyl orange by the heterojunction photocatalysts prepared in Examples 1-4 and Comparative Examples 1-5.

[0060]

[0061]

[0062] As shown in Table 1, Comparative Example 1 exhibits lower photocatalytic activity for the degradation of methyl orange in water compared to Examples 1-4. This is mainly due to the lack of activation of MnIn2S4, resulting in the absence of dense heterogeneous coupling between MnIn2S4 and MoO2 in the prepared MnIn2S4 / MoO2, thus hindering effective heterogeneous transport of photogenerated carriers. Comparative Examples 2-3 demonstrate that the amount of sodium borohydride affects the activation degree of MnIn2S4, thereby influencing the coupling degree between MnIn2S4 and MoO2 in the MnIn2S4-MoO2 heterojunction, ultimately affecting the photocatalytic activity of the product. Comparative Examples 4-5 show that the reaction temperature of the activated MnIn2S4 and MoO2 precursors in the reactor affects the crystallization degree of the heterojunction material, thus impacting the photocatalytic activity of the prepared catalyst.

[0063] Figure 1 The image shows the XRD pattern of the MnIn2S4-MoO2 heterojunction photocatalyst prepared in Example 3. Figure 1 In the XRD pattern, the 2θ peaks at 14.3°, 27.6°, 33.5°, 43.9°, and 48.1° can be attributed to the (111), (311), (400), (511), and (440) crystal planes of MnIn2S4, consistent with the standard JCPDS No. 65-7474 card for MnIn2S4. Meanwhile, the 2θ peaks at 26.0°, 37.0°, 53.5°, and 66.7° can be attributed to the (-111), (-211), (-312), and (-402) crystal planes of MoO2, consistent with the standard JCPDS No. 32-0671 card for MoO2. The XRD characterization shows that the prepared MnIn2S4-MoO2 heterojunction photocatalyst has high phase purity.

[0064] Figure 2 (a) and (b) are the S2p high-resolution XPS spectra of the MnIn2S4 / MoO2 photocatalyst prepared in Comparative Example 1 and the MnIn2S4-MoO2 heterojunction photocatalyst prepared in Example 3, respectively. Figure 2(a) shown, the S2p spectrum of MnIn2S4 / MoO2 shows three fitted peaks, corresponding to S-Mn (161.3 ev), S-In (162.9 ev) in MnIn2S4 structure and S-Mo (159.7 ev) formed between MnIn2S4 and MoO2. Compared with the S2p spectrum of MnIn2S4 / MoO2, the S-Mo peak at 159.7 eV in the S2p fitted peaks of MnIn2S4-MoO2 is significantly enhanced, indicating that the coupling degree between MnIn2S4 and MoO2 in the heterojunction catalyst is improved, and the two form a close heterojunction structure.

[0065] Figure 3 The photocurrent performance test diagram of the MnIn2S4 / MoO2 photocatalyst prepared for Comparative Example 1 and the MnIn2S4-MoO2 heterojunction photocatalyst prepared for Example 3. As can be seen from the figure, under the same light conditions, the instantaneous photocurrent intensity generated by MnIn2S4-MoO2 is significantly higher than that of MnIn2S4 / MoO2, which is mainly due to the increased S-Mo bond energy between MnIn2S4 and MoO2 in the MnIn2S4-MoO2 heterojunction photocatalyst, which effectively promotes the transport of photo-generated carriers, thereby inhibiting the recombination of electrons and holes.

[0066] Figure 4 The electrochemical impedance test diagram of the MnIn2S4 / MoO2 photocatalyst prepared for Comparative Example 1 and the MnIn2S4-MoO2 heterojunction photocatalyst prepared for Example 3. As can be seen from the figure, the radius of the first half of the MnIn2S4-MoO2 heterojunction impedance spectrum is smaller than that of MnIn2S4 / MoO2, indicating that MnIn2S4-MoO2 has better photo-generated carrier transport performance, which is consistent with the conclusion obtained from the photocurrent diagram. Figure 3

[0067] Figure 5 The photocatalytic degradation of methyl orange activity comparison diagram of the MnIn2S4 / MoO2 photocatalyst prepared for Comparative Example 1 and the MnIn2S4-MoO2 heterojunction photocatalyst prepared for Example 3. The experimental method is as follows: 500 mL of methyl orange solution with an initial concentration of 60 mg / L is taken, 0.5 g of the MnIn2S4 / MoO2 photocatalyst prepared for Comparative Example 1 and the MnIn2S4-MoO2 heterojunction photocatalyst prepared for Example 3 is added respectively, and the suspension is oscillated under constant temperature and light shielding conditions for 30 min, then the visible light source is turned on for irradiation for 60 min, and the photocatalytic degradation experiment is carried out. From the experimental process, the suspension is taken out at intervals, centrifuged by a high-speed centrifugal machine, and the methyl orange concentration in the supernatant is measured, and the removal rate is calculated according to formula (1), and the results are shown as follows. Figure 5

[0068] As shown in Figure 5 ​​It can be seen that the photocatalytic degradation rate of methyl orange on the MnIn2S4-MoO2 heterojunction photocatalyst is significantly improved compared with the MnIn2S4 / MoO2 photocatalyst. This is mainly because the activated MnIn2S4 can further react with the MoO2 precursor to form a tight S-Mo bond, so that the prepared MnIn2S4-MoO2 heterojunction has a more optimal transfer efficiency of photo-generated carriers, thereby promoting the separation of photo-generated electrons and holes, so that the photocatalytic efficiency is improved.

[0069] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary and that changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the application. The scope of the application is therefore defined by the claims appended hereto and their equivalents.

Claims

1. A method for preparing a MnIn2S4-MoO2 heterojunction photocatalyst, characterized in that, Includes the following steps: S1. Preparation of MnIn2S4 catalyst by hydrothermal method; S2. The prepared MnIn2S4 was activated using sodium borohydride as an activating agent; S3. The activated MnIn2S4 was mixed with the MoO2 precursor, and the MnIn2S4-MoO2 heterojunction photocatalyst was prepared by hydrothermal method and calcination method. In step S2, the specific activation process is as follows: The MnIn2S4 photocatalyst obtained in step S1 was added to an ethanol solution of sodium borohydride and heated under reflux under stirring. The resulting product was washed and dried to obtain the activated MnIn2S4 photocatalyst. The ratio of MnIn2S4, sodium borohydride, and ethanol is 100-500 mg: 20-150 mg: 40-60 mL; the reaction temperature is 30-60 °C; and the reaction time is 1.5-5 h.

2. The preparation method of the MnIn2S4-MoO2 heterojunction photocatalyst according to claim 1, characterized in that, The specific steps of the hydrothermal method are as follows: MnCl2·4H2O, InCl3·4H2O and thioacetamide were added to the ethanol solution and stirred to form a homogeneous mixture. The mixture was transferred into a reactor for hydrothermal reaction, and the resulting product was washed and dried to obtain MnIn2S4 photocatalyst.

3. The preparation method of the MnIn2S4-MoO2 heterojunction photocatalyst according to claim 2, characterized in that, The molar ratio of MnCl2·4H2O, InCl3·4H2O and thioacetamide is 1:2:4, and the molar ratio of thioacetamide to ethanol is 4~8 mmol:50~80 mL.

4. The preparation method of the MnIn2S4-MoO2 heterojunction photocatalyst according to claim 2, characterized in that, The hydrothermal reaction temperature is 110~200℃, and the reaction time is 8~48h.

5. The preparation method of the MnIn2S4-MoO2 heterojunction photocatalyst according to claim 1, characterized in that, The specific steps of the hydrothermal method and the calcination method are as follows: MoCl5, acetic acid, and the activated MnIn2S4 obtained in step S2 were added to an ethanol solution and stirred to form a homogeneous mixture. The mixture was then transferred to a reaction vessel for hydrothermal reaction. The resulting product was washed, dried, and calcined in a tube furnace to obtain a MnIn2S4-MoO2 heterojunction photocatalyst.

6. The method for preparing the MnIn2S4-MoO2 heterojunction photocatalyst according to claim 5, characterized in that, The ratio of MoCl5, acetic acid, activated MnIn2S4 and ethanol is 2~8 mmol: 1~3 ml: 1~10 mmol: 50~80 ml; The hydrothermal reaction temperature is 100~200℃, and the hydrothermal reaction time is 12~48h; The calcination temperature is 200~500℃, the calcination atmosphere is argon, and the calcination time is 30~120min.

7. A MnIn2S4-MoO2 heterojunction photocatalyst, characterized in that, It was obtained by the preparation method described in any one of claims 1-6.

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