Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst and its application in piezophotocatalytic H2 production

Abstract

The application belongs to the field of piezoelectric photocatalysts, and particularly relates to a Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst and application thereof to piezoelectric photocatalytic H2 production. 0.5 Cd 0.5 S is synthesized, Cu7S4 is synthesized, and finally, the Mn 0.5 Cd 0.5 S / Cu7S4 heterojunction composite catalyst is prepared by the impregnation method. The catalyst is used for piezoelectric photocatalytic H2 production under the synergistic action of sunlight irradiation and ultrasonic vibration. The catalyst is simple to synthesize, green, pollution-free and easy to operate. The prepared catalyst has rich active sites and excellent stability, and does not produce secondary pollution.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of piezophotocatalysts, and particularly relates to a Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst and application thereof to piezophotocatalytic H2 production. BACKGROUND

[0002] In recent years, energy shortage and environmental problems have attracted widespread attention due to economic development and population growth, so it is particularly important to develop sustainable clean energy. Among various energies, hydrogen energy is highly concerned due to its high energy and green environmental protection. Since Fujishima and Honda discovered the photoelectrochemical water splitting reaction using semiconductors in 1972, photocatalysis has made rapid progress as one of the technologies for converting photon energy and environmental remediation. In the past few decades, a variety of photocatalysts have been discovered, such as metal oxides, metal sulfides, organic polymers, etc., and CdS has attracted great attention due to its suitable conduction band and valence band position, but the serious photocorrosion phenomenon and the rapid recombination of photo-generated carriers limit the large-scale application of CdS.

[0003] Mn x Cd 1-x S solid solution has great application prospects due to its controllable band gap and better photocatalytic activity and corrosion resistance than CdS. For example, patent CN 110586137 A discloses a preparation method of a Mn 0.5 Cd 0.5 S and Au supported photocatalyst, and the prepared catalyst has higher photocatalytic activity and stability. Patent CN 108855138 A discloses a Z-type structure Mn 0.5 Cd 0.5 S / Ag / Bi2WO6 composite photocatalyst and a preparation method thereof, and the prepared catalyst reduces the recombination rate of photo-generated electrons and holes, improves the quantum efficiency and photocatalytic activity. However, the above-mentioned catalyst preparation methods are complicated, have high energy consumption, and use noble metals, which have high cost. SUMMARY

[0004] The application aims to provide a Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst, and apply it to piezophotocatalytic H2 production, which has higher catalytic activity and stronger corrosion resistance.

[0005] The Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst provided by the application has the following preparation method:

[0006] (1) Mn 0.5 Cd 0.5Preparation of S:

[0007] Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O were dissolved in distilled water at a molar ratio of 1:1, stirred for 30 min to make them fully dissolved, then thioacetamide C2H5NS (TAA) was added and stirred to make them uniformly mixed, then the mixed solution was transferred to a reaction kettle with a polytetrafluoroethylene lining, the reaction kettle was placed in an oven at 160°C for 24 h, after the reaction was completed, it was cooled to room temperature, the solid in the reaction kettle was washed with deionized water and anhydrous ethanol three times, and dried at 60°C overnight to obtain orange Mn 0.5 Cd 0.5 S (referred to as: MCS) powder.

[0008] (2) Preparation of Cu7S4:

[0009] Cu(NO3)2·6H2O was dissolved in an ethylenediamine solution, stirred for 20 min to make it fully dispersed, then thiourea was added and stirred for 30 min, then the mixed solution was transferred to a reaction kettle with a polytetrafluoroethylene lining, the reaction kettle was placed in an oven at 120°C for 2 h, after the reaction was completed, it was cooled to room temperature, the solid in the reaction kettle was washed with deionized water and anhydrous ethanol three times, and dried at 60°C overnight to obtain black Cu7S4 powder.

[0010] Among them, the molar ratio of Cu(NO3)2·6H2O and thiourea is 1:1.

[0011] (3) Preparation of Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst:

[0012] Mn 0.5 Cd 0.5 S catalyst and Cu7S4 catalyst were dissolved in deionized water, ultrasonic stirring was performed, and then filtered, washed and dried at room temperature to obtain orange powder, which was Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst. The mass of Cu7S4 added is 1% to 7% of the mass of Mn 0.5 Cd 0.5 S.

[0013] Among them, the ultrasonic power is 240 W, the ultrasonic time is 1 h, the stirring speed is 400 r / min, and the stirring time is 4 h.

[0014] The composite catalyst prepared by the above method is used for piezophotocatalytic hydrogen production, and the specific application method is as follows: Mn 0.5 Cd 0.5S / Cu7S4 composite catalyst is added into water, uniformly dispersed by ultrasonic, then Na2S, Na2SO3 aqueous solution is added as a sacrificial agent, N2 is passed, and H2 is produced under the condition of ultrasonic and light irradiation.

[0015] The ultrasonic power is 240 W, and the light irradiation power is 55 W.

[0016] Mn 0.5 Cd 0.5 The amount of S / Cu7S4 composite catalyst used in water is 2 mg to 5 mg / 18 mL.

[0017] The present application has the advantages of:

[0018] (1) The present application provides Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst, which has the characteristics of simple synthesis conditions, easy operation, fast and efficient, energy saving and environmental protection.

[0019] (2) The introduction of Cu7S4 does not change the crystal structure of Mn 0.5 Cd 0.5 S, and no other diffraction peaks appear, indicating that Mn 0.5 Cd 0.5 S / Cu7S4 composite material has excellent crystallinity and purity.

[0020] (3) Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst produces H2 under the action of photocatalysis, piezoelectric catalysis and piezoelectric light synergy, and the catalytic performance under the condition of piezoelectric light is the best, which is 2.9 times of that of pure Mn 0.5 Cd 0.5 S catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the scanning electron microscope image of the Mn 0.5 Cd 0.5 S / Cu7S4 catalyst synthesized in Example 1.

[0022] Figure 2 is the XRD pattern of CuS and Cu9S5 synthesized in Comparative Examples 5 and 6.

[0023] Figure 3 is the XRD pattern of Mn 0.5 Cd 0.5 S / Cu7S4 composite material and Mn 0.5 Cd 0.5 S, Cu7S4 synthesized in Examples 1, 2, 3, 4 and Comparative Examples 3 and 4.

[0024] Figure 4 are the different ratios of Mn synthesized in Example 1, 2, 3, 4 and Comparative Example 3, 4 under the simultaneous piezoelectric and light action 0.5 Cd 0.5 S / Cu7S4 composite, Mn 0.5 Cd 0.5 S and Cu7S4 H2 production performance graph.

[0025] Figure 5 are the different ratios of Mn synthesized in Example 1, 2, 3, 4 under the piezoelectric action only 0.5 Cd 0.5 S / Cu7S4, Mn 0.5 Cd 0.5 S and Cu7S4 H2 production performance graph.

[0026] Figure 6 are the different ratios of Mn synthesized in Example 1, 2, 3, 4 under the light action only 0.5 Cd 0.5 S / Cu7S4, Mn 0.5 Cd 0.5 S and Cu7S4 H2 production performance graph.

[0027] Figure 7 are the different ratios of Mn synthesized in Example 1, 2, 3, 4 under the piezoelectric and light action, 5 mg 0.5 Cd 0.5 S / Cu7S4 catalyst H2 production performance graph.

[0028] Figure 8 are the different ratios of Mn synthesized in Example 1, 2, 3, 4 under the piezoelectric and light action, 3.5 mg 0.5 Cd 0.5 S / Cu7S4 catalyst H2 production performance graph. DETAILED DESCRIPTION

[0029] The present application is not limited to the following detailed description, and those skilled in the art can implement the present application in other various embodiments according to the disclosure of the present application, or fall within the scope of the present application by using the design structure and idea of the present application with simple changes or modifications. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The H2 production efficiency is calculated according to the following formula:

[0030]

[0031] R: H2 production rate, unit: μmol / (g·h), V: hydrogen volume, unit: μL, m: catalyst mass, unit: g, t: reaction time, unit: h.

[0032] Example 1

[0033] Dissolve 1.2254 g Mn(CH3COO)2·4H2O and 1.3326 g Cd(CH3COO)2·2H2O in distilled water, stir for 30 min to make them fully dissolved, then add 0.7513 g thioacetamide (TAA) and continue stirring to make them mix evenly, then transfer the mixture into a reaction kettle lined with polytetrafluoroethylene, and place the reaction kettle in an oven at 160°C for 24 h. After the reaction is completed, cool to room temperature, wash the solid in the reaction kettle with deionized water and anhydrous ethanol three times, and dry at 60°C overnight to obtain orange Mn 0.5 Cd 0.5 S powder.

[0034] Dissolve 1 mmol Cu(NO3)2·6H2O in 20 mL ethylenediamine solution (commercially available), stir for 20 min to make them fully dispersed, then add 1 mmol thiourea and stir for 30 min, then transfer the mixture into a reaction kettle lined with polytetrafluoroethylene, and place the reaction kettle in an oven at 120°C for 2 h. After the reaction is completed, cool to room temperature, wash the solid in the reaction kettle with deionized water and anhydrous ethanol three times, and dry at 60°C overnight to obtain black Cu7S4 powder.

[0035] Dissolve the above Mn 0.5 Cd 0.5 S catalyst and Cu7S4 catalyst in deionized water, ultrasonic at 240 W for 1 h, and stir at a speed of 400 r / min for 4 h. Filter, wash, and dry at room temperature to obtain orange powder, which is Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst. The mass of Cu7S4 is 3% of the mass of Mn 0.5 Cd 0.5 S.

[0036] The application method of Mn 0.5 Cd 0.5 S-3% Cu7S4 composite catalyst is as follows:

[0037] Take 2 mg Mn 0.5 Cd 0.5 S-3% Cu7S4 composite catalyst, add 18 mL water, and ultrasonic disperse for half an hour to make the catalyst uniformly dispersed in water. Then add 2 mL of a mixed solution of 0.35 M Na2S and 0.25 M Na2SO3 as a sacrificial agent, then pass N2 for half an hour, and finally seal under ultrasonic (240 W) and light (55 W xenon lamp simulating sunlight) conditions for 2 h. After the experiment is completed, draw 0.5 mL of gas into a tube, detect the peak area by a gas chromatograph, calculate the H2 production rate, and the H2 production rate is 16.24 mmol / (g·h) through analysis and calculation.

[0038] Example 2

[0039] The difference between Example 1 and Example 2 is that 1% of Cu7S4 by mass of Mn 0.5 Cd 0.5 S is added during preparation, and the other preparation methods are the same as those of Example 1.

[0040] The application method is the same as that of Example 1, and the Mn 0.5 Cd 0.5 S-1% Cu7S4 composite catalyst has a H2 production rate of 12.11 mmol / (g·h).

[0041] Example 3

[0042] The difference between Example 1 and Example 3 is that 5% of Cu7S4 by mass of Mn 0.5 Cd 0.5 S is added during preparation, and the other preparation methods are the same as those of Example 1.

[0043] The application method is the same as that of Example 1, and the Mn 0.5 Cd 0.5 S-5% Cu7S4 composite catalyst has a H2 production rate of 10.76 mmol / (g·h).

[0044] Example 4

[0045] The difference between Example 1 and Example 4 is that 7% of Cu7S4 by mass of Mn 0.5 Cd 0.5 S is added during preparation, and the other preparation methods are the same as those of Example 1.

[0046] The application method is the same as that of Example 1, and the Mn 0.5 Cd 0.5 S-7% Cu7S4 composite catalyst has a H2 production rate of 9.17 mmol / (g·h).

[0047] Example 5

[0048] The difference between Example 1 and Example 5 is that 2 mg of catalyst is changed to 5 mg of catalyst in the application method, and the other is the same as that of Example 1. Mn 0.5 Cd 0.5 S-3% Cu7S4 catalyst has a H2 production rate of 4.45 mmol / (g·h).

[0049] Example 6

[0050] The difference between Example 1 and Example 6 is that 2 mg of catalyst is changed to 3.5 mg of catalyst in the application method, and the other is the same as that of Example 1. Mn 0.5 Cd0.5 The H2 production rate of S-3% Cu7S4 catalyst was 12.38 mmol / (g h).

[0051] mmol / (g h).

[0052] Example 7

[0053] Compared with Example 1, the difference is that 2 mg of catalyst in the method is changed to 1 mg of catalyst, and the others are the same as Example 1. Mn 0.5 Cd 0.5 The H2 production rate of S-3% Cu7S4 catalyst was 13.32 mmol / (g h).

[0054] Comparative Example 1

[0055] Compared with Example 1, the difference is that the ultrasonic (240 W) and light (55 W xenon lamp simulating sunlight) in the method is changed to only ultrasonic (240 W), and the others are the same as Example 1. Mn 0.5 Cd 0.5 The H2 production rate of S-3% Cu7S4 catalyst was 32.09 mmol / (g h).

[0056] Comparative Example 2

[0057] Compared with Example 1, the difference is that the ultrasonic (240 W) and light (55 W xenon lamp simulating sunlight) in the method is changed to only light (55 W xenon lamp simulating sunlight), and the others are the same as Example 1. Mn 0.5 Cd 0.5 The H2 production rate of S-3% Cu7S4 catalyst was 12.57 mmol / (g h).

[0058] Comparative Example 3

[0059] Dissolve 1.2254 g of Mn(CH3COO)2·4H2O and 1.3326 g of Cd(CH3COO)2·2H2O in 40 mL of distilled water, stir for 30 min, then add 0.7513 g of TAA, continue to stir for 30 min, then transfer into a polytetrafluoroethylene lined hydrothermal kettle, keep the temperature at 160℃ for 24 h. After cooling to room temperature, wash with deionized water and anhydrous ethanol, and vacuum dry at 60℃ for 24 h to obtain an orange powder, which is Mn 0.5 Cd 0.5 S catalyst.

[0060] Weigh 2 mg of Mn 0.5 Cd 0.5S catalyst, 18 mL water was added, and ultrasonic dispersion was performed for 30 min. Then, 2 mL of a 0.35 M Na2S, 0.25 M Na2SO3 mixed solution was added, followed by N2 for 30 min, and finally, 2 h of sealing under ultrasonic irradiation (240 W) and light (55 W xenon lamp simulating sunlight). After the experiment was completed, the gas in a 0.5 mL tube was extracted, and the peak area was detected by a gas chromatograph to calculate the H2 production rate. Analysis and calculation showed that the H2 production rate was 5.57 mmol / (g·h).

[0061] Comparative Example 4

[0062] Cu(NO3)2·6H2O (0.2416 g) was dissolved in 20 mL of ethylenediamine, stirred for 20 min, and then stirred for 30 min after the addition of 0.0761 g of thiourea to obtain a blue solution. The solution was transferred into a Teflon-lined autoclave, and the temperature was maintained at 120°C for 2 h. After the reaction was completed, the reaction mixture was cooled to room temperature, washed with deionized water and anhydrous ethanol, and dried at 60°C under vacuum for 24 h to obtain a black powder, which was Cu7S4 catalyst.

[0063] 2 mg of Cu7S4 catalyst was added to 18 mL of water, and ultrasonic dispersion was performed for 30 min. Then, 2 mL of a 0.35 M Na2S, 0.25 M Na2SO3 mixed solution was added, followed by N2 for 30 min, and finally, 2 h of sealing under ultrasonic irradiation (240 W) and light (55 W xenon lamp simulating sunlight). After the experiment was completed, the gas in a 0.5 mL tube was extracted, and the peak area was detected by a gas chromatograph to calculate the H2 production rate. Analysis and calculation showed that the H2 production rate was 0.28 mmol / (g·h).

[0064] Comparative Example 5

[0065] Orange Mn 0.5 Cd 0.5 The S powder was prepared according to Example 1.

[0066] 1 mmol of Cu(NO3)2·6H2O was dissolved in 20 mL of water, stirred for 20 min to ensure dispersion, and then 1 mmol of thiourea was added and stirred for 30 min. Then, the mixed solution was transferred into a Teflon-lined autoclave, and the autoclave was placed in an oven at 120°C for 2 h. After the reaction was completed, the reaction mixture was cooled to room temperature, washed with deionized water and anhydrous ethanol three times, and dried at 60°C overnight to obtain a black CuS powder.

[0067] Mn 0.5 Cd 0.5 The S catalyst and CuS catalyst were dissolved in deionized water, ultrasonic irradiation was performed at 240 W for 1 h, and stirring was performed at a stirring speed of 400 r / min for 4 h. Filtration, washing, and drying were performed at room temperature to obtain an orange powder, which was Mn 0.5 Cd0.5 S / CuS composite catalyst. The mass of CuS is Mn. 0.5 Cd 0.5 3% of the S mass.

[0068] Weigh 2mg Mn 0.5 Cd 0.5 An S-3% CuS composite catalyst was added to 18 mL of water and ultrasonically dispersed for half an hour to ensure uniform dispersion. Then, a 2 mL mixture of 0.35 M Na₂S and 0.25 M Na₂SO₃ was added as a sacrificial agent, followed by N₂ purging for half an hour. Finally, the mixture was sealed for 2 hours under ultrasonic (240 W) and light irradiation (55 W xenon lamp simulating sunlight). After the experiment, 0.5 mL of gas was extracted from the tube, and the peak area was detected using gas chromatography. The H₂ production rate was calculated to be 10.24 mmol / (g·h).

[0069] Comparative Example 6

[0070] Orange Mn 0.5 Cd 0.5 The preparation of S powder is the same as in Example 1.

[0071] Compared with Comparative Example 5, the difference is that in the preparation process, 1 mmol Cu(NO3)2·6H2O is dissolved in a mixed solution of 4 mL ethylenediamine and 16 mL water, and the other steps are the same as those in Comparative Example 5, so as to obtain black Cu9S5 powder.

[0072] Weigh 2mg Mn 0.5 Cd 0.5 An S-3% Cu9S5 composite catalyst was added to 18 mL of water and ultrasonically dispersed for half an hour to ensure uniform dispersion. Then, a 2 mL mixture of 0.35 M Na2S and 0.25 M Na2SO3 was added as a sacrificial agent, followed by N2 purging for half an hour. Finally, the mixture was sealed for 2 hours under ultrasonic (240 W) and light irradiation (55 W xenon lamp simulating sunlight). After the experiment, 0.5 mL of gas was extracted from the tube, and the peak area was detected using gas chromatography. The H2 production rate was calculated to be 11.45 mmol / (g·h).

Claims

1. A Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst characterized by, The catalyst is formed by Mn 0.5 Cd 0.5 S and Cu7S4 form a heterojunction structure, wherein Cu7S4 is Mn 0.5 Cd 0.5 1-7% of the mass of S Mn 0.5 Cd 0.5 The preparation method of S / Cu7S4 composite catalyst is as follows: Mn 0.5 Cd 0.5 S and Cu7S4 were dissolved in water, and the mixture was subjected to ultrasonication, stirring, filtration, washing, and drying to obtain Mn. 0.5 Cd 0.5 S / Cu7S4 composite catalyst; The Mn 0.5 Cd 0.5 The method for photocatalytic production of H2 using S / Cu7S4 composite catalyst is: adding Mn 0.5 Cd 0.5 S / Cu7S4 composite catalyst into water, uniformly dispersing, then adding Na2S and Na2SO3 aqueous solution as a sacrificial agent, and then carrying out photocatalytic production of H 2； The ultrasonic power was 240 W, and the light was simulated sunlight of 55 W xenon lamp; The preparation method of Cu7S4 was as follows: Cu(NO3)2·6H2O was dissolved in ethylenediamine solution, stirred for 20 min, fully dispersed, then thiourea was added, stirred for 30 min, then the mixed solution was transferred into a reaction kettle with a polytetrafluoroethylene lining, placed in an oven at 120 DEG C for 2 h, after the reaction was completed, cooled to room temperature, the solid in the reaction kettle was washed with deionized water and anhydrous ethanol for three times, dried at 60 DEG C overnight, and black Cu7S4 powder was obtained.

2. The Mn of claim 1 0.5 Cd 0.5 S / Cu7S4 composite catalyst characterized in that, The composite catalyst was prepared, the ultrasonic power was 240 W, the ultrasonic time was 1 h, the stirring speed was 400 r / min, and the stirring time was 4 h.

3. The Mn of claim 1 0.5 Cd 0.5 S / Cu7S4 composite catalyst characterized in that, Mn 0.5 Cd 0.5 The method for preparing S is as follows: Mn(CH3COO)2-4H2O and Cd(CH3COO)2-2H2O are dissolved in distilled water at a molar ratio of 1 : 1, stirred for 30 min to make them fully dissolved, then thioacetamide is added and stirred to make them uniformly mixed, then the mixed solution is transferred into a reaction kettle with a polytetrafluoroethylene lining, placed in an oven at 160°C for 24 h, after the reaction is completed, cooled to room temperature, the solid in the reaction kettle is washed with deionized water and anhydrous ethanol for three times, dried at 60°C overnight, and orange Mn 0.5 Cd 0.5 S powder is obtained.

4. The Mn of claim 1 0.5 Cd 0.5 S / Cu7S4 composite catalyst characterized in that, Mn 0.5 Cd 0.5 The amount of S / Cu7S4 composite catalyst used in water was 2-5 mg / 18 mL.

5. The Mn of claim 1 0.5 Cd 0.5 S / Cu7S4 composite catalyst characterized in that, The molar ratio of Cu(NO3)2·6H2O to thiourea was 1:1.

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