An Ag2S / Mn 0.5 Cd 0.5 S-composite catalysts, their preparation methods and applications

Abstract

This invention belongs to the field of piezoelectric photocatalysis, specifically relating to an Ag2S / Mn... 0.5 Cd 0.5 S-composite catalysts, their preparation methods, and applications. Preparation of Mn via hydrothermal synthesis. 0.5 Cd 0.5 Ag₂S / Mn nanoparticles and Ag₂S were combined using an impregnation method to form a heterojunction, thus preparing Ag₂S / Mn nanoparticles. 0.5 Cd 0.5 S-composite catalyst. This catalyst is used for piezoelectric photocatalytic reduction of H2 and CO2 under the synergistic effect of sunlight irradiation and ultrasonic vibration. The catalyst synthesis method of this invention is simple, green and pollution-free, and highly operable. The prepared catalyst has abundant active sites and excellent catalytic effect.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric photocatalysis, specifically relating to an Ag2S / Mn... 0.5 Cd 0.5 S-composite catalysts, their preparation methods, and applications. Background Technology

[0002] In recent years, with the booming economy and the continuous expansion of the population, energy shortages and environmental protection issues have become increasingly prominent, attracting global attention. Against this backdrop, promoting the development of sustainable and clean energy is particularly urgent and important. Among numerous candidate energy sources, hydrogen energy stands out due to its high energy density and environmental friendliness, becoming a research hotspot. In particular, CdS, as a metal sulfide photocatalyst, has received widespread attention and research over the past few decades due to its suitable bandgap characteristics. However, despite its great potential, CdS faces the challenge of rapid recombination of photogenerated holes and electrons in practical applications, which greatly limits its efficiency in photocatalytic hydrogen production. To overcome this problem, scientists have turned their attention to Mn... x Cd 1-x S solid solution. This material achieves flexible control of the band gap by adjusting the ratio of Mn to Cd, not only retaining the excellent properties of CdS but also significantly improving photocatalytic activity and corrosion resistance. Therefore, Mn x Cd 1-x S solid solutions are considered a highly promising alternative, expected to play an important role in future energy conversion and environmental protection, and show broad application prospects.

[0003] Ag₂S exhibits high chemical stability, maintaining its structural and property stability under various environmental conditions. Furthermore, Ag₂S is low in toxicity or non-toxic, making its applications safer and more environmentally friendly. Ag₂S can absorb light across a wide spectral range, including visible and near-infrared light. This invention combines Ag₂S with Mn... x Cd 1-x S-composite catalysts are designed to provide catalysts with superior photocatalytic performance. Summary of the Invention

[0004] The purpose of this invention is to provide an Ag2S / Mn 0.5 Cd 0.5 The S composite catalyst was applied to piezoelectric photocatalytic hydrogen production or CO2 reduction to CO, and the resulting catalyst exhibited higher catalytic performance and stronger light absorption capacity.

[0005] The Ag2S / Mn provided by this invention 0.5 Cd 0.5 S composite catalyst, composed of Mn 0.5 Cd0.5 The heterojunction structure formed by the composite of S and Ag2S, where Ag2S is Mn 0.5 Cd 0.5 The content of S is 1-7% (preferably 1-3%) by mass. The preparation method includes the following steps:

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

[0007] Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O were dissolved in deionized water and stirred until completely dissolved. Then, C2H5NS(TAA) was added and stirred until homogeneous. The mixture was then transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 160°C for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the solid in the reaction vessel was washed three times with deionized water and anhydrous ethanol and dried at 60°C to obtain orange Mn. 0.5 Cd 0.5 S powder (abbreviated as: MCS).

[0008] Furthermore, the molar ratio of Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O is 1:1;

[0009] Furthermore, the molar ratio of Mn(CH3COO)2·4H2O and C2H5NS is 1:2.

[0010] (2) Preparation of Ag2S

[0011] AgNO3 and TAA were dispersed in H2O and stirred for 20 minutes to mix them evenly. The mixture was then transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 150°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solid in the reaction vessel was washed and dried to obtain Ag2S.

[0012] Furthermore, the molar ratio of AgNO3 to TAA is 1:1.

[0013] (3)Ag2S / Mn 0.5 Cd 0.5 Preparation of S composite catalyst:

[0014] Mn 0.5 Cd 0.5 The S catalyst and Ag₂S catalyst were dissolved in a solvent and subjected to ultrasonication and stirring. After filtration, washing, and drying at room temperature, an orange powder was finally obtained, which is the Ag₂S / Mn catalyst. 0.5 Cd 0.5 S composite catalyst.

[0015] Furthermore, the solvent is: deionized water, anhydrous ethanol, or a mixture of anhydrous ethanol and water; the amount of Ag₂S added is Mn 0.5 Cd 0.5 S content is 1% to 7% (preferably 5%) of the mass.

[0016] Furthermore, the ultrasonic power was 240W, the ultrasonic time was 1 hour, the stirring speed was 400 r / min, and the stirring time was 4 hours.

[0017] The composite catalyst prepared above is used for piezoelectric photocatalytic hydrogen production. The specific application method is as follows: Weigh Ag₂S / Mn... 0.5 Cd 0.5 The S composite catalyst is added to water and ultrasonically dispersed. Then, Na2S and Na2SO3 aqueous solutions are added as sacrificial agents, and N2 is passed through. H2 is produced in a sealed environment under the combined conditions of ultrasound and light irradiation.

[0018] The composite catalyst prepared above is used for CO2 reduction to CO production. The specific application method is as follows: Weigh Ag2S / Mn... 0.5 Cd 0.5 The S composite catalyst is added to water and ultrasonically dispersed. Then, Na2S and Na2SO3 aqueous solutions are added as sacrificial agents, and CO2 is passed through. CO is produced in a sealed environment under the combined conditions of ultrasound and light.

[0019] The ultrasonic power was 240W, and the light irradiation power was 55W. The concentrations of Na₂S and Na₂SO₃ in the sacrificial agent solution were 0.35M and 0.25M, respectively. The amount of composite catalyst used in water was 2 mg / 18 mL.

[0020] The advantages of this invention are:

[0021] (1) Ag2S / Mn synthesized in this invention 0.5 Cd 0.5 The S composite catalyst has simple synthesis conditions, is easy to operate, and has the characteristics of being fast, efficient, energy-saving and environmentally friendly.

[0022] (2) Ag₂S exhibits high chemical stability, maintaining its structural and performance stability under various environments. Furthermore, Ag₂S is characterized by low or non-toxicity, making its application safer and more environmentally friendly. Ag₂S can absorb a wide range of light, including visible and near-infrared light, indicating that the composite catalyst possesses good crystallinity and purity.

[0023] (3) Ag2S and Mn of the present invention x Cd 1-x S has a different band structure and a wider light absorption range, thus improving light energy utilization. The separation of photogenerated electrons and holes at the interface is also due to the interaction between Ag₂S and Mn.x Cd 1-x The tight binding of S improves photocatalytic efficiency.

[0024] (4) Ag2S / Mn synthesized in this invention 0.5 Cd 0.5 S exhibits lower overpotential, smaller impedance, and a smaller Tafel slope, indicating that Ag₂S / Mn 0.5 Cd 0.5 In S, the separation efficiency of photogenerated carriers and holes is higher. Attached Figure Description

[0025] Figure 1 Mn synthesized by hydrothermal synthesis 0.5 Cd 0.5 S, Ag2S, and X% Ag2S / Mn synthesized by impregnation method 0.5 Cd 0.5 XRD pattern of S (where X is the proportion of Ag2S) composite catalyst;

[0026] Figure 2 It is Mn 0.5 Cd 0.5 S(MCS), Ag2S and 3% Ag2S / Mn 0.5 Cd 0.5 SEM image of the S composite catalyst;

[0027] Figure 3 It is pure MCS and 3% Ag2S / Mn 0.5 Cd 0.5 S's LSV curve;

[0028] Figure 4 It is pure MCS and 3% Ag2S / Mn 0.5 Cd 0.5 S's EIS curve;

[0029] Figure 5 It is pure MCS and 3% Ag2S / Mn 0.5 Cd 0.5 Tafel slope plot of S;

[0030] Figure 6 It is pure MCS, Ag2S and 3% Ag2S / Mn 0.5 Cd 0.5 UV-vis spectrum of S;

[0031] Figure 7 It is pure MCS and Ag2S / Mn under piezoelectric light. 0.5 Cd 0.5 H2 production performance diagram of S composite catalyst;

[0032] Figure 8 It is pure MCS under piezoelectric effect only and Ag2S / Mn ratios. 0.5 Cd 0.5 H2 production performance diagram of S composite catalyst;

[0033] Figure 9 It is pure MCS under light-only irradiation and different ratios of Ag2S / Mn 0.5 Cd 0.5 H2 production performance diagram of S composite catalyst;

[0034] Figure 10 It is 3% Ag2S / Mn with different Mn / Cd ratios under piezoelectric light. x Cd 1-x S's H2 production performance diagram;

[0035] Figure 11 It is pure MCS and different proportions of Ag2S / Mn 0.5 Cd 0.5 Performance diagram of CO2 reduction to CO production by S composite catalyst. Detailed Implementation

[0036] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or variations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The H2 and CO production efficiencies are calculated using the following formulas:

[0037]

[0038] R: H2 / CO production rate, unit: μmol / (g·h), V: hydrogen / carbon monoxide volume, unit: μL, m: catalyst mass, unit: g, t: reaction time, unit: h.

[0039] Example 1

[0040] 5 mmol of Mn(CH3COO)2·4H2O and 5 mmol of Cd(CH3COO)2·2H2O were dissolved in distilled water and stirred for 30 min until fully dissolved. Then, 10 mmol of thioacetamide (TAA) was added and stirred until homogeneous. The mixture was then transferred to a polytetrafluoroethylene-lined reactor and placed in an oven at 160 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature. The solid in the reactor was washed three times with deionized water and anhydrous ethanol and dried at 60 °C to obtain orange Mn. 0.5 Cd 0.5 S powder (MCS).

[0041] 1 mmol AgNO3 and 1 mmol TAA were dispersed in 40 mL H2O and stirred for 20 min to mix them evenly. The mixture was then transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 150 °C for 2 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid in the reaction vessel was washed and dried to obtain Ag2S.

[0042] The above Mn 0.5 Cd 0.5 The S catalyst and Ag₂S catalyst were dissolved in 10 mL of deionized water and subjected to ultrasonication at 240 W for 1 h followed by stirring at 400 rpm for 4 h. The mixture was then filtered, washed, and dried at room temperature to obtain an orange powder, which is the Ag₂S / Mn catalyst. 0.5 Cd 0.5 S composite catalyst. The mass of Ag₂S is Mn. 0.5 Cd 0.5 3% of the S mass.

[0043] 3% Ag2S / Mn 0.5 Cd 0.5 Application methods of S composite catalysts:

[0044] (1) Weigh 2 mg of 3% Ag2S / Mn 0.5 Cd 0.5 The S composite catalyst was added to 18 mL of water and ultrasonically dispersed for half an hour to ensure uniform dispersion. Then, a mixed solution 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 to calculate the H₂ production rate. The calculated H₂ production rate was 26.25 mmol / (g·h).

[0045] Using the same method, the H2 production rate of MCS was measured to be 5.57 mmol / (gh), and the CO production rate was 3.21 μmol / (g·h).

[0046] (2) Weigh 2 mg of 3% Ag2S / Mn 0.5 Cd 0.5The S composite catalyst was added to 18 mL of water and ultrasonically dispersed for half an hour to ensure uniform dispersion. Then, a mixed solution of 0.35 M Na₂S and 0.25 M Na₂SO₃ was added as a sacrificial agent, followed by CO₂ passage 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 to calculate the CO production rate. The calculated CO production rate was 14.49 μmol / (g·h).

[0047] Example 2

[0048] The difference compared to Example 1 is that the mass of Ag2S added during the preparation process is Mn. 0.5 Cd 0.5 S is 1% of the mass, and other preparation methods are the same as in Example 1.

[0049] The application method is the same as in Example 1, and the 1% Ag2S / Mn prepared in Example 2 is as follows. 0.5 Cd 0.5 The S composite catalyst produced H2 at a rate of 18.76 mmol / (g·h) and CO at a rate of 8.12 μmol / (g·h).

[0050] Example 3

[0051] Compared with Example 1, the difference is that the mass of Ag2S added during the preparation process is Mn 0.5 Cd 0.5 S is 5% of the mass, and other preparation methods are the same as in Example 1.

[0052] The application method is the same as in Example 1 and Example 3, which prepared 5% Ag2S / Mn. 0.5 Cd 0.5 The S composite catalyst produced H2 at a rate of 15.38 mmol / (g·h) and CO at a rate of 7.08 μmol / (g·h).

[0053] Example 4

[0054] Compared with Example 1, the difference is that the mass of Ag2S added during the preparation process is Mn 0.5 Cd 0.5 S is 7% of the mass, and other preparation methods are the same as in Example 1.

[0055] The application method is the same as in Example 1 and Example 4 for the 7% Ag2S / Mn preparation. 0.5 Cd 0.5 The S composite catalyst produced H2 at a rate of 11.81 mmol / (g·h) and CO at a rate of 5.17 μmol / (g·h).

[0056] Comparative Example 1

[0057] Compared to Example 1, the difference is that the ultrasonic (240W) and light (55W xenon lamp simulating sunlight) application methods were changed to ultrasonic only (240W), otherwise the same as Example 1. 3% Ag2S / Mn 0.5 Cd 0.5 The S catalyst produces H2 at a rate of 76.85 μmol / (g·h).

[0058] Comparative Example 2

[0059] Compared to Example 1, the difference is that the application method was changed from ultrasonic (240W) and light irradiation (55W xenon lamp simulating sunlight) to light irradiation only (55W xenon lamp simulating sunlight), otherwise the same as Example 1. 3% Ag2S / Mn 0.5 Cd 0.5 The S catalyst produces H2 at a rate of 16.61 mmol / (g·h).

[0060] Comparative Example 3

[0061] Compared with Example 1, the difference is that the molar ratio of Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O added is 0.2:0.8, and the prepared composite catalyst is designated as 3%Ag2S / Mn. 0.2 Cd 0.8 S.

[0062] The application method is the same as in Example 1, and the prepared 3% Ag2S / Mn 0.2 Cd 0.8 The S composite catalyst produces H2 at a rate of 0.43 mmol / (g·h).

[0063] Comparative Example 4

[0064] Compared with Example 1, the difference is that the molar ratio of Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O added is 0.3:0.7, and the prepared composite catalyst is designated as 3%Ag2S / Mn. 0.3 Cd 0.7 S.

[0065] The application method is the same as in Example 1, and the prepared 3% Ag2S / Mn 0.3 Cd 0.7 The hydrogen production rate of the S composite catalyst is 0.5 mmol / (g·h).

[0066] Comparative Example 5

[0067] Compared with Example 1, the difference is that the molar ratio of Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O added is 0.4:0.6, and the prepared composite catalyst is designated as 3%Ag2S / Mn. 0.4 Cd 0.6 S.

[0068] The application method is the same as in Example 1, and the prepared 3% Ag2S / Mn 0.4 Cd 0.6 The hydrogen production rate of the S composite catalyst is 0.56 mmol / (g·h).

[0069] Comparative Example 6

[0070] Compared with Example 1, the difference is that the molar ratio of Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O added is 0.6:0.4, and the prepared composite catalyst is designated as 3%Ag2S / Mn. 0.6 Cd 0.4 S.

[0071] The application method is the same as in Example 1, and the prepared 3% Ag2S / Mn 0.6 Cd 0.4 The hydrogen production rate of the S composite catalyst is 19.47 mmol / (g·h).

[0072] Comparative Example 7

[0073] Compared with Example 1, the difference is that the molar ratio of Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O added is 0.7:0.3, and the prepared composite catalyst is designated as 3%Ag2S / Mn. 0.7 Cd 0.3 S.

[0074] The application method is the same as in Example 1, and the prepared 3% Ag2S / Mn 0.7 Cd 0.3 The hydrogen production rate of the S composite catalyst is 7.59 mmol / (g·h).

[0075] Although the invention has been described in conjunction with preferred embodiments, the invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the invention. Guided by the inventive concept, those skilled in the art should recognize that any modifications made to the various embodiments of the invention will be covered by the spirit and scope of the claims.

Claims

1. An Ag2S / Mn 0.5 Cd 0.5 The S composite catalyst, characterized in that, The composite catalyst is made of Mn 0.5 Cd 0.5 The heterojunction structure formed by the composite of S and Ag2S, where Ag2S is Mn 0.5 Cd 0.5 S quality is 1-7%.

2. An Ag2S / Mn as described in claim 1 0.5 Cd 0.5 The preparation method of the S composite catalyst is characterized by, Mn 0.5 Cd 0.5 S and Ag₂S were dissolved in a solvent, and after sonication and stirring, the mixture was filtered, washed, and dried to obtain Ag₂S / Mn. 0.5 Cd 0.5 S composite catalyst; the solvent is deionized water, anhydrous ethanol, or a mixture of deionized water and anhydrous ethanol; the ultrasonic power is 240 W, and the ultrasonic time is 1 h; the stirring speed is 400 r / min, and the stirring time is 4 h.

3. The Ag2S / Mn as described in claim 2 0.5 Cd 0.5 The preparation method of the S composite catalyst is characterized by, The Mn 0.5 Cd 0.5 The preparation method of S is as follows: Mn(CH3COO)2·4H2O and Cd(CH3COO)2·2H2O are dissolved in deionized water and stirred until completely dissolved. Then, C2H5NS is added and stirred until the mixture is homogeneous. The mixture is then transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 160℃ for 24 hours. After the reaction is completed, the mixture is cooled to room temperature. The solid in the reaction vessel is washed and dried to obtain orange Mn. 0.5 Cd 0.5 S powder.

4. The Ag2S / Mn as described in claim 3 0.5 Cd 0.5 The preparation method of the S composite catalyst is characterized by, The molar ratio of Mn(CH3COO)2·4H2O, Cd(CH3COO)2·2H2O, and C2H5NS is 1:1:

2.

5. The Ag2S / Mn as described in claim 2 0.5 Cd 0.5 The preparation method of the S composite catalyst is characterized by, The method for preparing Ag2S is as follows: AgNO3 and TAA are dispersed in H2O and stirred until homogeneous. The mixture is then transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 150°C for 2 hours. After the reaction is completed, the mixture is cooled to room temperature, and the solid in the reaction vessel is washed and dried to obtain Ag2S.

6. The Ag2S / Mn as described in claim 5 0.5 Cd 0.5 The preparation method of the S composite catalyst is characterized by, The mass ratio of AgNO3 to TAA is 1:

1.

7. An Ag2S / Mn as described in claim 1 0.5 Cd 0.5 The application of S composite catalyst is characterized by... The catalyst is used for piezoelectric photocatalytic production of H2; or for piezoelectric photocatalytic reduction of CO2 to CO.

8. The Ag2S / Mn as described in claim 7 0.5 Cd 0.5 The application of S composite catalyst is characterized by... Ag2S / Mn 0.5 Cd 0.5 The S composite catalyst is added to the solvent and dispersed evenly. Then, a sacrificial agent solution is added, followed by the introduction of N2 or CO2. Under ultrasonic and light irradiation conditions, piezoelectric photocatalysis is carried out to produce H2 or CO2 to reduce CO.

9. The Ag2S / Mn as described in claim 8 0.5 Cd 0.5 The application of S composite catalyst is characterized by... The solvent is: deionized water, anhydrous ethanol, or a mixture of anhydrous ethanol and water. The concentrations of Na₂S and Na₂SO₃ in the sacrificial agent solution are 0.35 M and 0.25 M, respectively. The ultrasonic power is 240 W, and the illumination is simulated by a 55 W xenon lamp.

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