MoO2 / moP modified octahedral CdIn2S4 composite photocatalyst and application thereof

Abstract

The application discloses a MoO2 / MoP modified octahedral CdIn2S4 composite photocatalyst and application thereof, and is characterized in that a non-noble metal cocatalyst MoO2 / MoP nanosheet is synthesized by a calcination method, and is loaded on the surface of octahedral CdIn2S4 by a hydrothermal method, so as to obtain a composite catalyst. With the heterojunction effect of MoO2 / MoP and CdIn2S4, the MoO2 / MoP-CdIn2S4 composite obtained by the application exhibits better photocatalytic degradation activity of dyes than MoO2 / MoP and CdIn2S4 monomers, and has a better application prospect in the aspect of hydrogen production by photolysis of water.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterial preparation and photocatalysis technology, specifically to a novel catalyst material for application in the fields of environmental and energy photocatalysis. Background Technology

[0002] With the depletion of fossil fuels such as coal and oil and the deterioration of the human living environment, research into new alternative energy sources and clean environmental technologies has attracted increasing attention. Environment and energy have become major problems facing humanity and urgently need to be addressed. Therefore, researchers worldwide are actively exploring and searching for effective solutions. Photocatalytic water splitting technology, which converts solar energy into clean hydrogen, has the potential to completely solve the crisis of fossil fuel depletion, while photocatalytic degradation and removal of toxic organic pollutants may also become a cheap and feasible way to solve environmental problems. Therefore, photocatalysis technology holds promise as an effective way to solve environmental and energy issues.

[0003] Binary and ternary sulfides, such as CdS, In₂S₃, ZnIn₂S₄, and CdIn₂S₄ (CIS), are typical narrow bandgap semiconductors and exhibit excellent photocatalytic activity under visible light irradiation. However, CdS suffers from photocorrosion during irradiation, leading to its deactivation during reactions and limiting its widespread application. As compounds of CdS and In₂S₃, CIS possesses a bandgap suitable for visible light absorption (approximately 2.4 eV). Existing research results indicate that CIS exhibits good activity for photocatalytic degradation of organic pollutants and hydrogen production from water splitting under visible light irradiation. To improve the photocatalytic performance of CIS, researchers have made numerous attempts, such as controlling the morphology of CIS (e.g., nanotubes, nanoribbons, nanowires, and flower-like microspheres), doping with noble metals, and designing CIS-based composite materials. Semiconductor modification using noble metals (Pt, Au, and Ag) as cocatalysts has attracted increasing research attention. However, from a resource-saving perspective, their scarcity and high cost have already created significant obstacles in manufacturing. Therefore, it is necessary to explore low-cost non-precious metal cocatalysts and modify existing cocatalysts (transition metal phosphides), such as MoP, Co2P, and Ni2P. Modification of these cocatalysts can enhance their ability to capture electrons or remove holes from the catalyst, thereby improving the photocatalytic activity of the photocatalyst. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for preparing a novel MoO2 / MoP modified octahedral CdIn2S4 (MOP / CIS) composite photocatalyst, and applies it to photocatalytic degradation and hydrogen production. The technical problem to be solved is how to improve the photocatalytic performance of the MOP / CIS composite to construct a highly efficient and stable photocatalyst.

[0005] To achieve the objective, the present invention adopts the following technical solution:

[0006] This invention first discloses a method for preparing MoO2 / MoP modified octahedral CdIn2S4 composite photocatalysts, which involves loading MoO2 / MoP nanosheets onto the surface of octahedral CIS using a hydrothermal method. Specifically, the method includes the following steps:

[0007] Step 1: Preparation of MoO3 nanoblocks

[0008] Ammonium molybdate was weighed and placed in a mortar. After being ground evenly, it was transferred to a covered crucible and calcined to obtain MoO3 nanoblocks.

[0009] Step 2: Preparation of MOP nanosheets

[0010] The MoO3 nanoblocks and NaH2PO2·H2O obtained in step 1 were added to a mortar and ground evenly. The resulting mixture was then placed in a covered porcelain boat and calcined to obtain MoO2 / MoP nanosheets, denoted as MOP nanosheets.

[0011] Step 3: Preparation of MOP / CIS composite photocatalyst

[0012] MOP nanosheets, Cd(CH3COO)2·2H2O, InCl3 and Na2S·9H2O were dissolved in deionized water and stirred until homogeneous. The resulting suspension was transferred to a stainless steel autoclave lined with polytetrafluoroethylene for hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature, and the resulting product was washed and dried to obtain a MoO2 / MoP modified octahedral CdIn2S4 composite photocatalyst, denoted as MOP / CIS composite photocatalyst.

[0013] Furthermore, in step 1, the calcination temperature is 450–600°C, the calcination time is 1 hour, and the calcination atmosphere is air.

[0014] Furthermore, in step 2, the molar ratio of the MoO3 nanoblocks to NaH2PO2·H2O is 1:1 to 10, the calcination temperature is 450 to 550°C, the calcination time is 2 hours, and the calcination atmosphere is argon.

[0015] Furthermore, in step 3, the molar ratio of Cd(CH3COO)2·2H2O, InCl3, and Na2S·9H2O is 1:2:4, and the mass percentage of MOP nanosheets in the obtained MOP / CIS composite photocatalyst is 1-10%.

[0016] Furthermore, in step 3, the hydrothermal reaction temperature is 160°C and the reaction time is 12 hours.

[0017] This invention designs and prepares a MOP / CIS composite photocatalyst. Under visible light irradiation, MOP / CIS shows promising potential applications in environmental applications (such as photocatalysts for the degradation of dyes like tetracycline and methyl orange) and in energy photocatalysis (such as photocatalytic hydrogen production).

[0018] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0019] 1. This invention employs calcination and hydrothermal methods to load MOP nanosheets onto the surface of an octahedral CIS catalyst. Leveraging the co-catalytic effect of MOP and the heterogeneous interaction between MOP and CIS, the MOP / CIS composite exhibits superior photocatalytic degradation and hydrogen generation capabilities compared to MOP and CIS alone, while also enhancing the catalyst's charge separation efficiency. Notably, the phosphide introduced into the photocatalyst serves as a high-performance charge separation center for photogenerated electron-hole pairs and an active site for photocatalytic degradation.

[0020] 2. The MOP / CIS composite of the present invention exhibits excellent photocatalytic activity in the degradation of pollutants (tetracycline and methyl orange) and hydrogen production: After 1 hour of visible light irradiation, the MOP / CIS obtained by the present invention exhibits excellent photocatalytic degradation performance, with degradation rates of 83.86% and 88.79% for tetracycline and methyl orange, respectively. The MOP / CIS obtained by the present invention has an activity of 5.96 mmol·g in the benzyl alcohol oxidation hydrogen production system. -1 ·h -1 The values ​​are MOP (0.008 mmol·g⁻¹). -1 ·h -1 ) and CIS (0.21 mmol·g -1 ·h -1 745 times and 28 times.

[0021] 3. The preparation method of the present invention is simple and the hydrothermal method can realize the loading of MOP on octahedral CIS, providing a simple and referable new method for the synthesis of other non-precious metal co-catalysts. Attached Figure Description

[0022] Figure 1 The XRD pattern of MoO3 synthesized in Example 1 is shown below. Figure 1 a) and SEM image ( Figure 1 b).

[0023] Figure 2 The image shows the XRD pattern of the MOP nanosheets synthesized in Example 2.

[0024] Figure 3 The image shows the XRD pattern of the MOP / CIS composite material synthesized in Example 3.

[0025] Figure 4SEM images of MOP synthesized in Example 2 and CIS synthesized in Example 3, and 7% MOP / CIS, are shown. Figure 4 a and Figure 4 b corresponds to the CIS sample. Figure 4 c and Figure 4 d corresponds to the MOP sample. Figure 4 e and Figure 4 f corresponds to a 7% MOP / CIS sample.

[0026] Figure 5 TEM and HRTEM images of MOP synthesized in Example 2 and CIS synthesized in Example 3, 7% MOP / CIS, are shown. Figure 5 a and Figure 5 d corresponds to the CIS sample. Figure 5 b and Figure 5 e corresponds to the MOP sample. Figure 5 c and Figure 5 f corresponds to the MOP / CIS sample.

[0027] Figure 6 The diagram shows the activity of each catalyst synthesized in the examples in degrading tetracycline.

[0028] Figure 7 The diagram shows the activity of each catalyst synthesized in the examples in degrading methyl orange.

[0029] Figure 8 The diagram shows the catalytic activity of each catalyst synthesized in the examples for hydrogen production from benzyl alcohol.

[0030] Figure 9 The current-time response diagrams for each catalyst synthesized in the examples are shown.

[0031] Figure 10 The electrochemical impedance spectroscopy diagrams are shown for each catalyst synthesized in the examples. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. The description of the specific embodiments is merely an example. The following embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] In this embodiment, MoO3 nanobulbs were prepared according to the following steps:

[0035] Ammonium molybdate was placed in a mortar and ground evenly. Then it was transferred to a covered crucible and heated to 500°C at a rate of 5°C / min under air atmosphere. The mixture was then kept at this temperature for 1 hour to obtain MoO3 nanoblocks.

[0036] Example 2

[0037] In this embodiment, MOP nanosheets were prepared according to the following steps:

[0038] The MoO3 nanoblocks obtained in Example 1 and NaH2PO2·H2O were ground evenly in a mortar at a molar ratio of 1:6. The mixture was then placed in a covered porcelain boat. Under an argon atmosphere, the temperature was increased to 500°C at a rate of 5°C / min and calcined for 2 hours to obtain MOP nanosheets. During calcination, the lid of the porcelain boat was not completely sealed to ensure that the raw materials were in contact with the gas but would not be blown away by the gas.

[0039] Example 3

[0040] In this embodiment, the MOP / CIS composite material is synthesized according to the following steps:

[0041] MOP nanosheets, 1 mmol Cd(CH3COO)2·2H2O, 2 mmol InCl3, and 4 mmol Na2S·9H2O were dissolved in 50 mL of deionized water and stirred for 40 minutes. The suspension was then transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene and kept at 160 °C for 12 hours. The precipitate was cooled to room temperature, washed several times with deionized water and anhydrous ethanol by centrifugation, and dried in a vacuum oven at 60 °C for 12 hours to obtain the MOP / CIS composite photocatalyst. The sample was denoted as x%MOP / CIS, where x% represents the mass percentage of MOP nanosheets in the obtained MOP / CIS composite photocatalyst. For comparison, pure CIS (without MOP) was synthesized using the same method.

[0042] The samples obtained in the above embodiments were subjected to the following characterization tests on morphology and performance.

[0043] I. Morphological characteristics:

[0044] 1. XRD and morphology characterization of MoO3 nanoblocks: X-ray diffraction can identify the type, crystal form, and crystallinity of a substance. In the diffraction pattern of MoO3 ( Figure 1 a) Major diffraction peaks were observed at 13.14°, 23.72°, 26.11°, 27.78°, 34.20°, 39.43°, and 49.68°, corresponding to the (020), (110), (040), (021), (111), (060), and (002) crystal planes, respectively. This is consistent with the PDF standard card (JCPDS No. 35-0609) for MoO3. Figure 1 In b, the morphology of MoO3 can be observed to be a blocky structure.

[0045] 2. XRD characterization of MOP nanosheets: In the diffraction pattern of MOP ( Figure 2Diffraction peaks of MoO2 and MoP were observed, with 26.34°, 37.41°, and 53.94° belonging to MoO2, and 32.06°, 43.36°, and 57.62° belonging to MoP. Therefore, MOP is a mixture containing both MoO2 and MoP.

[0046] 3. XRD characterization of MOP / CIS composite materials: Figure 3 XRD diffraction patterns of CIS and 7% MOP / CIS are shown. Several relatively distinct diffraction peaks can be clearly observed in the figures. The peaks at 23.58°, 27.65°, 33.48°, 43.86°, and 47.92° correspond to the (220), (311), (400), (511), and (440) crystal planes of CIS, respectively, consistent with the PDF standard card (JCPDS No. 27-0060). In the composite material spectrum, three characteristic peaks belonging to CIS and a characteristic peak at 28.0° belonging to the (001) crystal plane of MOP can be clearly observed, indicating the successful composite of the two substances. However, due to the low MOP loading, the crystallinity of some characteristic peaks in the composite material is weak. However, the presence of MOP in the composite material can be fully confirmed by subsequent scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM).

[0047] 4. Morphological characterization of CIS, MOP, and MOP / CIS composites: The morphology of CIS, MOP, and 7% MOP / CIS photocatalysts was analyzed using SEM, TEM, and HRTEM. The CIS photocatalyst exhibited an octahedral morphology with a smooth surface and a particle size between 200-400 nm. Figure 4 (a and 4b). Due to calcination phosphating, when the material transforms from MoO3 to MoP, the morphology of MOP also changes to a porous structure. Figure 4 c and 4d). For the 7% MOP / CIS composite, the MOP nanostructures are distributed on the surface of the octahedral CIS ( Figure 4 e and 4f). TEM images also confirmed CIS ( Figure 5 a) octahedron and MOP ( Figure 5 b) has a nanoporous sheet-like structure, while 7% MOP / CIS ( Figure 5 c) The morphology consists of MOP nanosheets encapsulated on the octahedral surface of CIS. Figure 5 d and Figure 5 In equation e, the lattice spacings of 0.37 nm and 0.27 nm correspond to the crystal planes of CIS(220) and MOP(100), respectively, which is consistent with the XRD results above. HRTEM results for 7% MOP / CIS ( Figure 5In f), 0.37 nm corresponds to the CIS(220) crystal plane, and 0.27 nm corresponds to the MOP(100) crystal plane. The results of SEM and TEM confirm that the MOP / CIS heterojunction has indeed been formed. Furthermore, the tight interface between the materials facilitates rapid charge separation and transfer, thereby enhancing photocatalytic performance.

[0048] II. Catalytic activity test of MOP / CIS complex:

[0049] 1. Activity in degrading antibiotics and dyes

[0050] The photocatalytic activity of the catalyst was tested at room temperature by degrading tetracycline / methyl orange. Specifically, 10 mg of the catalyst sample was dispersed in 50 mL of tetracycline (50 mg / L) or 50 mL of methyl orange (20 mg / L) solution in a 100 mL beaker. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, the suspension was irradiated with a xenon lamp (λ>420 nm). After certain time intervals, 5 mL of sample was taken, centrifuged, and the absorbance of the tetracycline and methyl orange solutions was analyzed at 357 nm and 464 nm using a UV-Vis spectrophotometer.

[0051] Figure 6 The activity of various catalysts for tetracycline degradation after 1 hour of illumination was shown, with MOP and CIS showing degradation rates of 24.59% and 42.73%, respectively. The 7% MOP / CIS combination exhibited excellent photocatalytic degradation performance, degrading 83.86% of tetracycline, which was 3.4 times and 1.9 times that of MOP and CIS, respectively. Figure 7 As shown, the prepared catalyst can also photocatalytically degrade the dye methyl orange. The degradation rate of methyl orange by 7% MOP / CIS is 88.79%, while the degradation rates of methyl orange by MOP and CIS are 30.82% and 22.43%, respectively. Through the degradation of the two substances, it can be found that 7% MOP / CIS has better photocatalytic degradation activity.

[0052] 2. Photocatalytic hydrogen production performance

[0053] Taking benzyl alcohol as an example, the photocatalytic generation of hydrogen was studied. The specific method was as follows: 50 mg of catalyst, 90 mL of water, and 10 mL of benzyl alcohol were added to a quartz glass reactor. The reactor was then connected to a photocatalytic reaction system and evacuated. The mixture in the reactor was stirred for half an hour in a dark adsorption environment to reach adsorption-desorption equilibrium. A 300 W xenon lamp (λ>420 nm) was used for illumination to initiate the photocatalytic reaction. During the reaction, the data were detected using an online TCD gas chromatograph. Experimental data are as follows: Figure 8With increasing MOP loading, hydrogen production initially increased and then decreased. The hydrogen production rate reached its highest at 7% MOP / CIS, approximately 5.96 mmol·g⁻¹. -1 ·h -1 The values ​​are MOP (0.008 mmol·g⁻¹). -1 ·h -1 ) and CIS (0.21 mmol·g -1 ·h -1 The activity was 745 times and 28 times that of the other two products.

[0054] 3. Electrochemical testing of the MOP / CIS complex

[0055] Photoelectrochemical methods can be used to qualitatively study the generation and transport of photogenerated carriers. This invention uses photocurrent and electrochemical impedance spectroscopy to further explore the enhanced photocatalytic activity of the prepared MOP / CIS catalyst. Typically, charge transfer properties are studied through transient photocurrent responses. Figure 9 Compared to MOP, both CIS and 7% MOP / CIS are more sensitive to light response, while 7% MOP / CIS exhibits a higher photocurrent density, indicating its strongest photogenerated carrier generation and transport capabilities. Furthermore, the current responds rapidly and instantaneously during the switching process, implying a tight interfacial contact between the MOP and CIS. Figure 10 Electrochemical impedance spectroscopy reveals the effects of photogenerated electron separation and transfer. The semicircular radii of the 7% MOP / CIS and CIS samples are smaller than those of the MOP sample, with the 7% MOP / CIS sample exhibiting the smallest semicircular radius. This reflects the lower charge transfer resistance of the 7% MOP / CIS composite material, indicating rapid separation of photogenerated charges under illumination. Based on these findings, it can be concluded that MOP, as a co-catalyst, can more effectively suppress the rapid recombination of photogenerated electron-hole pairs in CIS.

[0056] The results above show that the MOP / CIS complex has excellent degradation and hydrogen production activities, demonstrating the potential applications of MOP / CIS in the environmental and energy fields.

Claims

1. A method for preparing MoO2 / MoP modified octahedral CdIn2S4 composite photocatalyst, characterized in that, Follow these steps: Step 1: Preparation of MoO3 nanoblocks Ammonium molybdate was weighed and placed in a mortar. After being ground evenly, it was transferred to a covered crucible and calcined to obtain MoO3 nanoblocks. The calcination temperature was 450–600 °C, the calcination time was 1 h, and the calcination atmosphere was air. Step 2: Preparation of MOP nanosheets The MoO3 nanoblocks and NaH2PO2·H2O obtained in step 1 were added to a mortar and ground evenly. The resulting mixture was then placed in a covered porcelain boat and calcined to obtain MoO2 / MoP nanosheets, denoted as MOP nanosheets. The molar ratio of MoO3 nanoblocks to NaH2PO2·H2O was 1:1 to 10, the calcination temperature was 450 to 550℃, the calcination time was 2 hours, and the calcination atmosphere was argon. Step 3: Preparation of MOP / CIS composite photocatalyst MOP nanosheets, Cd(CH3COO)2·2H2O, InCl3, and Na2S·9H2O were dissolved in deionized water and stirred until homogeneous. The resulting suspension was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 160℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, and the resulting product was washed and dried to obtain a MoO2 / MoP modified octahedral CdIn2S4 composite photocatalyst, denoted as MOP / CIS composite photocatalyst. The molar ratio of Cd(CH3COO)2·2H2O, InCl3, and Na2S·9H2O was 1:2:4, and the mass percentage of MOP nanosheets in the obtained MOP / CIS composite photocatalyst was 1–10%.

2. An MOP / CIS composite photocatalyst prepared by the method described in claim 1.

3. The application of the MOP / CIS composite photocatalyst according to claim 2 in the degradation of dyes.

4. The application of the MOP / CIS composite photocatalyst according to claim 2 in photocatalytic hydrogen production.

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