A FeIn2S4-Co3O4 heterojunction photocatalyst and its preparation method

Abstract

The present invention relates to the field of photocatalyst technology, specifically a FeIn2S4-Co3O4 heterojunction photocatalyst and a preparation method thereof, wherein the preparation method is specifically as follows: preparing FeIn2S4 by a hydrothermal method; calcining and activating the prepared FeIn2S4 in a mixed atmosphere of argon and ammonia; mixing the activated FeIn2S4 with a Co3O4 precursor, and preparing the FeIn2S4-Co3O4 heterojunction photocatalyst by hydrothermal reaction and calcination. The present invention activates the prepared FeIn2S4 so that an S-Co bond is formed between the heterojunctions during the composite process with Co3O4. The covalent bond can enhance the binding degree between FeIn2S4 and Co3O4 in the FeIn2S4-Co3O4 heterojunction, thereby improving the transfer efficiency of photogenerated carriers between catalysts in the photocatalytic reaction, so that the FeIn2S4-Co3O4 heterojunction exhibits excellent quantum efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, and in particular to a FeIn2S4-Co3O4 heterojunction photocatalyst and a preparation method thereof. Background Art

[0002] Semiconductor-based photocatalysis is an emerging, highly efficient, green technology that not only converts solar energy into highly efficient and pollution-free hydrogen energy, but also rapidly and effectively purifies water pollutants, achieving green environmental purification. However, traditional semiconductors such as TiO2, ZnO, and SnO2 have wide band gaps and require high energy for excitation, resulting in weak visible light response and low sunlight utilization, limiting their industrial application.

[0003] In recent years, ternary metal-sulfide semiconductors have attracted significant attention due to their narrow energy bandgap and their susceptibility to visible light excitation in the solar spectrum. Among them, FeIn2S4, with its approximately 1.8 eV bandgap, well-positioned band edges, and low cost, is a promising visible-light semiconductor photocatalyst. However, single homogeneous semiconductors often suffer from the drawback of easy recombination of photogenerated carriers during photocatalytic reactions. Studies have shown that heterojunctions of two semiconductors can enhance carrier migration to a certain extent. Therefore, heterojunctions of FeIn2S4 with other semiconductors are an effective approach to enhance their photocatalytic performance. Co3O4, due to its excellent electrochemical properties and physicochemical stability, can effectively transport electrons and promote the separation of photogenerated electrons and holes, making it widely used in heterojunctions of semiconductors. Combining FeIn2S4 with Co3O4 to form binary heterojunction semiconductors holds promise for producing photocatalysts with excellent photocatalytic performance. However, existing heterojunction photocatalytic materials suffer from poor coupling between the heterojunction materials, low efficiency of heterojunction transport of photogenerated carriers, and complex heterojunction catalyst preparation processes. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that existing heterojunction photocatalytic materials have problems such as poor coupling between heterogeneous materials, low efficiency of heterogeneous transmission of photogenerated carriers, and complex heterojunction catalyst preparation process; the FeIn2S4-Co3O4 heterojunction photocatalyst prepared by the present invention has a tight heterojunction coupling degree and shows excellent visible light catalytic activity, wherein FeIn2S4 and Co3O4 are tightly bound by an S-Co bond. This chemical bond can effectively promote the transmission of photogenerated carriers between heterojunctions and inhibit the recombination of photogenerated electrons and holes.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a FeIn2S4-Co3O4 heterojunction photocatalyst, characterized in that it comprises the following steps:

[0006] S1: FeIn2S4 catalyst prepared by hydrothermal method;

[0007] S2: calcining and activating the prepared FeIn2S4 catalyst in a combined atmosphere of argon and ammonia;

[0008] S3: The activated FeIn2S4 catalyst is mixed with the Co3O4 precursor, and the FeIn2S4-Co3O4 heterojunction photocatalyst is prepared by hydrothermal reaction and calcination.

[0009] Preferably, the hydrothermal method for preparing the FeIn2S4 catalyst specifically comprises the following steps:

[0010] S1: adding FeCl2·6H2O, InCl3·4H2O, and thiourea to deionized water according to the molar ratio and mixing uniformly to obtain a mixed solution;

[0011] S2: The mixed solution is transferred to a reactor for hydrothermal reaction, and the obtained product is washed and dried to obtain FeIn2S4 catalyst.

[0012] Preferably, the molar ratio of FeCl2·6H2O, InCl3·4H2O, and thiourea is 1:1-3:6-12, and the usage ratio of thiourea to deionized water is 6-12 mmol:50-80 mL; the temperature of the hydrothermal reaction is 120-220°C, and the reaction time is 4-24 h.

[0013] Preferably, the calcination activation is carried out in a tube furnace at a temperature of 200-400° C. for 20-90 min; in the common atmosphere of argon and ammonia, the volume percentage of ammonia is 5%-50%.

[0014] Preferably, the hydrothermal reaction and calcination are specifically as follows: the activated FeIn2S4 catalyst and the Co3O4 precursor are dissolved in a 50% ethanol-water solution, stirred evenly to obtain a reaction liquid, and after adjusting the pH, the reaction liquid is transferred into a reactor for a hydrothermal reaction. The obtained product is washed and dried and then placed in a tubular furnace for calcination to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0015] Preferably, the usage ratio of the activated FeIn2S4 catalyst, Co(NO3)2·6H2O, ethanol and water is 1-8mmol:1-6mmol:20-50mL:20-50mL, the pH is adjusted to 8-12, the temperature of the hydrothermal reaction is 100-180℃ and the time is 8-24h; the calcination atmosphere is air, the calcination temperature is 250-500℃, and the calcination time is 60-150min.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention prepares FeIn2S4-Co3O4 heterojunction photocatalyst for the first time. The preparation method of the catalyst is simple, the raw material price is low, it is environmentally friendly, and it is easy to industrialize.

[0018] (2) During the calcination process, FeIn2S4 reacts with ammonia in the mixed gas, which increases the unsaturated S vacancies in its crystal phase structure, thereby promoting the subsequent reaction with the Co3O4 precursor to form a large number of S-Co covalent bonds, resulting in a high degree of heterogeneous coupling and a significant improvement in the efficiency of photogenerated carrier separation in the photocatalytic reaction;

[0019] (3) The FeIn2S4-Co3O4 heterojunction photocatalyst prepared by the present invention has high visible light activity and has high practical value and application prospects in the field of environmental governance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the XRD characterization diagram of the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3;

[0021] Figure 2 (a) and (b) are the S 2p high-resolution XPS characterization images of the FeIn2S4 / Co3O4 heterojunction photocatalyst prepared in Comparative Example 1 and the FeIn2S4-Co3O4 photocatalyst prepared in Example 3, respectively;

[0022] Figure 3 The photocurrent response diagrams of the FeIn2S4-Co3O4 photocatalyst prepared in Example 3 and the FeIn2S4 / Co3O4 mass junction photocatalyst prepared in Comparative Example 1;

[0023] Figure 4 Electrochemical impedance spectroscopy (EIS) measurements of the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3 and the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1.

[0024] Figure 5 This is a comparison chart of the photocatalytic activities of the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3 and the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example 1

[0027] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 140°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0028] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (10% ammonia) and calcined at 250°C for 20 min to obtain an activated FeIn2S4 photocatalyst.

[0029] 4 mmol of the activated FeIn2S4 prepared above and 1 mmol of Co(NO3)2·6H2O were added to a mixture of 20 mL of ethanol and 40 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 8; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 100°C for 10 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace and calcined at 250°C in an air atmosphere for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0030] Example 2

[0031] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 160°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0032] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (20% ammonia) and calcined at 250°C for 30 min to obtain an activated FeIn2S4 photocatalyst.

[0033] 4 mmol of the activated FeIn2S4 prepared above and 1.5 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 40 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 9; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 110°C for 12 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace at 300°C in an air atmosphere for calcination for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0034] Example 3

[0035] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0036] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (30% ammonia) and calcined at 300°C for 60 min to obtain an activated FeIn2S4 photocatalyst.

[0037] 4 mmol of the activated FeIn2S4 prepared above and 2.5 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 10; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace and calcined at 350°C in an air atmosphere for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0038] Example 4

[0039] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0040] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (30% ammonia) and calcined at 350°C for 60 min to obtain an activated FeIn2S4 photocatalyst.

[0041] 4 mmol of the activated FeIn2S4 prepared above and 3 mmol of Co(NO3)2·6H2O were added to a mixture of 40 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 11; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace and calcined at 350°C in an air atmosphere for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0042] Comparative Example 1

[0043] The difference from Example 3 is that the FeIn2S4 photocatalyst is not activated;

[0044] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0045] 4 mmol of the FeIn2S4 prepared above and 2.5 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 10; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace and calcined at 350°C in an air atmosphere for 60 minutes to obtain a FeIn2S4 / Co3O4 photocatalyst.

[0046] Comparative Example 2

[0047] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0048] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (15% ammonia) and calcined at 300°C for 60 min to obtain an activated FeIn2S4 photocatalyst.

[0049] 4 mmol of the activated FeIn2S4 prepared above and 2 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 10; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace under air atmosphere and calcined at 300°C for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0050] Comparative Example 3

[0051] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0052] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (25% ammonia) and calcined at 350°C for 60 min to obtain an activated FeIn2S4 photocatalyst.

[0053] 4 mmol of the activated FeIn2S4 prepared above and 2 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 10; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace under air atmosphere and calcined at 300°C for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0054] Comparative Example 4

[0055] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0056] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (20% ammonia) and calcined at 350°C for 60 min to obtain an activated FeIn2S4 photocatalyst.

[0057] 4 mmol of the activated FeIn2S4 prepared above and 2 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 10; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace under air atmosphere and calcined at 300°C for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0058] Comparative Example 5

[0059] 1.5 mmol FeCl2·6H2O, 3 mmol InCl3·4H2O and 10 mmol thiourea were added to 70 mL deionized water and stirred to form a mixed solution. The mixed solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 180°C for 6 h. The obtained product was washed with anhydrous ethanol and deionized water and dried to obtain FeIn2S4 photocatalyst.

[0060] 3 mmol of the FeIn2S4 prepared above was placed in a tube furnace in a mixed atmosphere of argon and ammonia (20% ammonia) and calcined at 350°C for 60 min to obtain an activated FeIn2S4 photocatalyst.

[0061] 4 mmol of the activated FeIn2S4 prepared above and 4 mmol of Co(NO3)2·6H2O were added to a mixture of 30 mL of ethanol and 50 mL of deionized water, stirred evenly to form a mixture, and 1 mol / L of sodium hydroxide solution was added dropwise to the mixture to adjust the pH of the mixture to 10; the above-obtained solution was transferred into a 100 mL reactor and subjected to hydrothermal reaction at 120°C for 16 hours. The obtained product was washed and dried with anhydrous ethanol and deionized water, and then placed in a tubular furnace under air atmosphere and calcined at 300°C for 60 minutes to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

[0062] Cr(VI) was used as the target for pollutant removal, and the photocatalytic reduction capabilities of the heterojunction photocatalysts prepared in Examples 1-4 and Comparative Examples 1-5 on Cr(VI) in water were measured respectively.

[0063] The test method is as follows: 500 mL of Cr(VI) solution with an initial concentration of 50 mg / L was taken, and 0.5 g of the heterojunction photocatalyst prepared in Examples 1-4 and Comparative Examples 1-5 was added respectively. The mixture was oscillated at a constant temperature for 30 min. After the adsorption reached equilibrium, a visible light source was turned on for 60 min to perform a photocatalytic reduction experiment. After the experiment was completed, the solution was taken out and centrifuged in a high-speed centrifuge. The concentration of Cr(VI) in the supernatant was determined according to the following formula: (1) Calculate the removal rate, (1) where: R is the removal rate (%), C0 is the initial concentration of Cr(VI) in the solution (mg / L), C e is the concentration of Cr(VI) in the solution after the photocatalytic reaction (mg / L), and the results are shown in Table 1;

[0064] Table 1 Removal efficiency of Cr(VI) by heterojunction photocatalysts prepared in Examples 1-4 and Comparative Examples 1-5

[0065] Selected materials Residual concentration of Cr(VI) in solution (mg / L) Removal rate (%) Example 1 14.5 71.1 Example 2 8.8 82.4 Example 3 1.6 96.9 Example 4 5.9 88.2 Comparative Example 1 18.3 63.4 Comparative Example 2 11.5 77.1 Comparative Example 3 7.2 85.6 Comparative Example 4 6.4 87.2 Comparative Example 5 12.9 74.3

[0066] As can be seen from Table 1, the photocatalytic removal of Cr(VI) from water in Comparative Example 1 is significantly reduced compared with Examples 1-4. This is mainly because the FeIn2S4 in Comparative Example 1 has not undergone an activation reaction, and a dense heterogeneous coupling is not formed between FeIn2S4 and Co3O4 in the prepared FeIn2S4 / Co3O4, thereby failing to effectively carry out heterogeneous transport of photogenerated carriers. It can be seen from Comparative Examples 2-3 that in the activation reaction, the volume percentage of ammonia and the reaction temperature in the mixed atmosphere of argon and ammonia are important factors in the activation effect of FeIn2S4, affecting the coupling degree of FeIn2S4 and Co3O4 in the FeIn2S4-Co3O4 heterojunction and the photocatalytic activity of the final product. It can be seen from Comparative Examples 4-5 that the molar percentages of FeIn2S4 and Co3O4 in the FeIn2S4-Co3O4 heterojunction affect the photocatalytic activity of the prepared composite catalyst.

[0067] Figure 1 This is the XRD pattern of the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3. Figure 1 In the equation, 2θ is located at 14.4 o , 23.7 o , 27.8 o , 29.1 o , 33.7 o , 41.6 o , 44.3o , 48.5 o , 56.8 o , 60.3 o and 67.7 o The peaks at correspond to the (111), (220), (311), (222), (400), (422), (511), (440), (533), (444) and (731) crystal planes of the FeIn2S4 structure, which is consistent with the standard JCPDS No. 80-0608 card of FeIn2S4. o , 31.3 o , 36.9 o , 38.5 o , 59.4 o and 65.2 o The peaks at correspond to the (111), (220), (311), (222), (511) and (440) crystal planes of Co3O4, which is consistent with the standard JCPDS No. 42-1407 card of Co3O4. In addition, no other impurity peaks were observed in the figure. Figure 1 XRD characterization results show that the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in the present invention has a high crystal phase purity.

[0068] Figure 2 (a) and (b) are the S 2p high-resolution XPS spectra of the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1 and the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3, respectively. Figure 2 As shown in (a), the S2p spectrum of FeIn2S4 / Co3O4 exhibits three fitted peaks. The two stronger peaks at 161.5 eV and 162.9 eV correspond to the S-Fe and S-In bonds in the FeIn2S4 structure, while the weaker peak at 164.1 eV is the S-Co bond formed between FeIn2S4 and Co3O4. Compared with FeIn2S4 / Co3O4, the intensity of the S-Co peak at 164.1 eV in the S2p fitted peaks of FeIn2S4-Co3O4 is significantly increased, indicating that the S-Co covalent bonds between FeIn2S4 and Co3O4 in FeIn2S4-Co3O4 are increased, forming a tightly coupled heterostructure.

[0069] Figure 3The photocurrent performance test diagram of the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1 and the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3 is shown. From the test results, it can be seen that the instantaneous photocurrent intensity generated by FeIn2S4-Co3O4 is significantly higher than that of FeIn2S4 / Co3O4. This is mainly due to the increased S-Co bonds between FeIn2S4 and Co3O4 in FeIn2S4-Co3O4, which makes FeIn2S4-Co3O4 have a higher charge transfer efficiency during the photocatalytic reaction.

[0070] Figure 4 The electrochemical impedance spectroscopy test diagrams of the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1 and the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3 are shown in the figure. As can be seen from the figure, the impedance radius in the first half of the FeIn2S4-Co3O4 heterojunction impedance spectrum is smaller than that of FeIn2S4 / Co3O4, indicating that FeIn2S4-Co3O4 can better inhibit the recombination of photogenerated electrons and holes, which is consistent with the above Figure 3 The conclusions drawn from the photocurrent test results are consistent.

[0071] Figure 5 The following is a comparison chart of the activity of the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1 and the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3 for the photocatalytic reduction of Cr(VI) in water. The experimental method is as follows: take 500mL of Cr(VI) solution with an initial concentration of 50mg / L, add 0.5g of the FeIn2S4 / Co3O4 photocatalyst prepared in Comparative Example 1 and the FeIn2S4-Co3O4 heterojunction photocatalyst prepared in Example 3, respectively, oscillate at a constant temperature for 30min under light-proof conditions, and then turn on the visible light source for 60min to conduct a photocatalytic reduction experiment. The suspension was taken out at regular intervals during the experiment, centrifuged in a high-speed centrifuge, and the Cr(VI) concentration in the supernatant was measured. The removal rate was calculated according to formula (1). The results are as follows: Figure 5 shown.

[0072] Depend on Figure 5 It can be seen that the residual concentration of Cr(VI) in the supernatant of FeIn2S4-Co3O4 is lower, that is, the visible light reduction activity of FeIn2S4-Co3O4 for Cr(VI) is significantly better than that of FeIn2S4-Co3O4. 4 / Co3O4, indicating that as the S-Co covalent bond in the composite catalyst strengthens, the photocatalytic activity of the catalyst also increases. The present invention activates FeIn2S4 and then produces a FeIn2S4-Co3O4 heterojunction photocatalyst with tight S-Co bonds in the subsequent composite process, achieving good visible light reaction activity and having high practical application prospects.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description. It is intended that all variations within the meaning and range of equivalents of the claims be embraced herein, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

Claims

1. A method for preparing a FeIn2S4-Co3O4 heterojunction photocatalyst, characterized in that: The following steps are involved: S1: FeIn2S4 catalyst prepared by hydrothermal method; S2: calcining and activating the prepared FeIn2S4 catalyst in a combined atmosphere of argon and ammonia; S3: The activated FeIn2S4 catalyst is mixed with the Co3O4 precursor, and the FeIn2S4-Co3O4 heterojunction photocatalyst is prepared by hydrothermal reaction and calcination.

2. The method for preparing the FeIn2S4-Co3O4 heterojunction photocatalyst according to claim 1, characterized in that: The hydrothermal method for preparing the FeIn2S4 catalyst specifically comprises the following steps: S1: adding FeCl2·6H2O, InCl3·4H2O, and thiourea to deionized water according to the molar ratio and mixing uniformly to obtain a mixed solution; S2: The mixed solution is transferred to a reactor for hydrothermal reaction, and the obtained product is washed and dried to obtain FeIn2S4 catalyst.

3. The method for preparing the FeIn2S4-Co3O4 heterojunction photocatalyst according to claim 2, characterized in that: The molar ratio of FeCl2·6H2O, InCl3·4H2O and thiourea is 1:1-3:6-12, and the usage ratio of thiourea to deionized water is 6-12 mmol:50-80 mL; the temperature of the hydrothermal reaction is 120-220° C., and the reaction time is 4-24 h.

4. The method for preparing the FeIn2S4-Co3O4 heterojunction photocatalyst according to claim 1, characterized in that: The calcination activation is carried out in a tubular furnace at a temperature of 200-400° C. for 20-90 minutes. In the common atmosphere of argon and ammonia, the volume percentage of ammonia is 5%-50%.

5. The method for preparing the FeIn2S4-Co3O4 heterojunction photocatalyst according to claim 1, characterized in that: The hydrothermal reaction and calcination are specifically as follows: the activated FeIn2S4 catalyst and Co(NO3)2·6H2O are dissolved in an ethanol-water solution, stirred evenly to obtain a reaction solution, the pH is adjusted, and the reaction solution is transferred into a reactor for a hydrothermal reaction. The obtained product is washed, dried, and then calcined in a tubular furnace to obtain a FeIn2S4-Co3O4 heterojunction photocatalyst.

6. The method for preparing the FeIn2S4-Co3O4 heterojunction photocatalyst according to claim 5, characterized in that: The usage ratio of the activated FeIn2S4 catalyst, Co(NO3)2·6H2O, ethanol and water is 1-8mmol:1-6mmol:20-50mL:20-50mL, the pH is adjusted to 8-12, the temperature of the hydrothermal reaction is 100-180°C and the time is 8-24h; the calcination atmosphere is air, the calcination temperature is 250-500°C, and the calcination time is 60-150min.

Images