A Cu-Ni3S4 / Mn 0.5 Cd 0.5 S-composite photocatalysts, their preparation methods, and applications.
By constructing a Cu-Ni3S4/Mn0.5Cd0.5S composite photocatalyst, reverse migration of photogenerated electrons and electronic structure regulation were achieved, solving the problem of low photocatalyst efficiency and improving the efficiency and stability of photocatalytic water splitting for hydrogen production. This method is suitable for visible light photocatalytic water splitting for hydrogen production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANAN UNIV
- Filing Date
- 2026-03-24
- Publication Date
- 2026-05-26
AI Technical Summary
Existing photocatalysts suffer from high recombination rates of photogenerated electron-hole pairs, low visible light utilization, and slow reaction kinetics on the catalyst surface, which limit the efficiency of photocatalytic water splitting for hydrogen production.
A Cu-Ni3S4/Mn0.5Cd0.5S composite photocatalyst was constructed, and a Mott-Schottky heterojunction was formed through self-assembly to realize the reverse migration of photogenerated electrons from the metalloid Cu-Ni3S4 to the semiconductor Mn0.5Cd0.5S. Combined with Cu doping to regulate the electronic structure, the interfacial charge separation efficiency and surface reaction kinetics were improved.
It significantly improves the rate of hydrogen production from photocatalytic water splitting, reaching 9 times the activity of pure Mn0.5Cd0.5S catalyst, and is low in cost, which is in line with the development direction of green and sustainable energy technology.
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Figure CN122076529A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photocatalyst preparation technology, specifically to a Cu-Ni3S4 / Mn... 0.5 Cd 0.5 S-composite photocatalysts, their preparation methods, and applications. Background Technology
[0002] Hydrogen energy is considered an ideal green energy carrier due to its high energy density and the fact that its combustion product is only water. Solar photocatalytic water splitting technology can directly convert abundant solar energy into chemical energy (hydrogen), making it one of the ideal ways to achieve green and sustainable hydrogen production. However, the key bottleneck for the large-scale application of this technology lies in the efficiency of the photocatalyst. Its core challenges include: rapid recombination of photogenerated electron-hole pairs, low utilization of the visible light portion of the solar spectrum, and slow reaction kinetics on the catalyst surface.
[0003] To address these challenges, researchers have developed various strategies. Among them, constructing heterojunctions, particularly Mott-Schottky heterojunctions (formed by the contact between a metal or metalloid and a semiconductor), is an effective means of promoting photogenerated charge separation. Traditional Mott-Schottky heterojunctions rely on a built-in electric field formed at the interface, which typically drives photogenerated electrons to migrate from the semiconductor to the metal (or metalloid), while holes remain on the semiconductor side, thus suppressing recombination. However, this unidirectional migration mode is limited by the interface barrier and carrier transport path, resulting in limited improvement in charge separation efficiency.
[0004] Mn 0.5 Cd 0.5 S, as a ternary metal sulfide solid solution, exhibits a band structure that can be tuned by the Mn / Cd ratio, thus possessing excellent visible light response and a matched conduction band position, which is beneficial for the thermodynamic driving of photocatalytic hydrogen production, making it a promising photocatalyst for hydrogen production. However, its relatively high recombination rate of photogenerated carriers significantly restricts further improvement in quantum yield, becoming a key bottleneck limiting its practical application. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a Cu-Ni3S4 / Mn 0.5 Cd 0.5 S-composite photocatalyst, its preparation method and application, Cu-Ni3S4 / Mn of the present invention 0.5 Cd 0.5 S-composite photocatalyst is composed of Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles are formed through self-assembly composites, Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5S nanoparticles form atomically close contacts at the interface, creating a Mott-Schottky heterojunction. This invention constructs a Cu-Ni3S4 / Mn... 0.5 Cd 0.5 The S-heterojunction breaks through the traditional charge migration mode of Schottky junctions, realizing the "reverse migration" of photogenerated electrons from metalloids to semiconductors. This migration mechanism greatly improves the interface charge separation efficiency, effectively suppresses electron-hole recombination, and overcomes the limitations of single Mnn... 0.5 Cd 0.5 The technical bottlenecks of S photocatalysts, such as easy carrier recombination, limited charge separation efficiency of traditional Mott-Schottky heterojunctions, and slow surface reaction kinetics, provide a new approach for designing high-efficiency heterojunction photocatalysts.
[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a Cu-Ni3S4 / Mn 0.5 Cd 0.5 S-composite photocatalyst, composed of Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles are formed through self-assembly composites, Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles form atomically close contacts at the interface, forming Mott-Schottky heterojunctions. The self-assembly is essentially a spontaneous process driven by interfacial interactions. It utilizes the differences in physicochemical properties (such as charge and surface energy) on the nanoparticle surface to form structurally stable heterojunctions with electronic interactions under thermodynamic drive, rather than a mechanical mixture forced by external forces.
[0007] Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 The mass ratio of S nanoparticles is 1~4:10. If the ratio is too low, the Cu-Ni3S4 / Mn ratio will be affected. 0.5 Cd 0.5 The heterojunction effect in the S composite photocatalyst is not significant; however, if the proportion is too high, the Cu-Ni3S4 / Mn ratio will decrease due to Cu-Ni3S4 shielding visible light. 0.5 Cd 0.5 The overall light absorption and utilization rate of S composite photocatalyst.
[0008] Cu-Ni3S4 nanoparticles are Cu-doped Ni3S4 nanoparticles with a Cu doping amount of 1 mol% to 10 mol%. At this doping amount, the electronic structure can be effectively controlled, while avoiding damage to the crystal structure and metal-like properties of Ni3S4 due to excessive doping.
[0009] Among them, Cu-Ni3S4 nanoparticles are metal-like, and Mn 0.5 Cd 0.5 S nanoparticles are semiconductors; DFT calculations revealed that the band structure of Cu-Ni3S4 crosses the Fermi level, classifying it as a metalloid. Whether the band structure crosses the Fermi level is used as the criterion for determining metalloids.
[0010] Preferably, in Cu-Ni3S4, the Cu doping amount is 5 mol%, and the Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 When the mass ratio of S nanoparticles is 2:10, the Cu-Ni3S4 / Mn 0.5 Cd 0.5 The S composite photocatalyst exhibits the best photocatalytic hydrogen production activity.
[0011] Preferably, Cu-Ni3S4 nanoparticles are prepared according to the following steps: Water and ethylene glycol were mixed to obtain a mixed solvent; soluble nickel salt and soluble copper salt were dissolved together in the mixed solvent to obtain a first solution; a sulfur source was dissolved in the mixed solvent to obtain a second solution; the second solution was added dropwise to the first solution, and the mixture was stirred at room temperature for 4 to 6 hours to obtain a suspension; the suspension was then subjected to a solvothermal reaction at 170°C to 180°C for 8 to 10 hours. After the reaction was completed, the product was washed and vacuum dried to obtain black Cu-Ni3S4 nanoparticles.
[0012] Preferably, the volume ratio of water to ethylene glycol is 1:1~2.
[0013] Preferably, the molar ratio of soluble nickel salt, soluble copper salt and sulfur source is 100:1~10:200~300; a ratio higher or lower than this range will result in a decrease in effectiveness.
[0014] Preferably, the soluble nickel salt is selected from nickel sulfate hexahydrate, nickel nitrate hexahydrate, or nickel chloride hexahydrate.
[0015] Preferably, the soluble copper salt is selected from copper nitrate trihydrate, copper sulfate pentahydrate, or copper chloride dihydrate.
[0016] Preferred, Mn 0.5 Cd 0.5 S nanoparticles were prepared according to the following steps: Soluble cadmium salt, soluble manganese salt, and sulfur source were dissolved or dispersed in water to obtain a precursor solution. The precursor solution was then subjected to a hydrothermal reaction. After natural cooling, the product was centrifuged, washed repeatedly with deionized water and ethanol, and dried at 60°C to obtain a pale yellow MnO2 solution. 0.5 Cd 0.5 S nanoparticles.
[0017] The molar ratio of soluble cadmium salt, soluble manganese salt, and sulfur source is 1:1:4~6; the hydrothermal reaction conditions are: hydrothermal reaction at 160℃~180℃ for 20h~24h. In this invention, when the molar ratio of Mn to Cd is 1:1, Mn... 0.5 Cd 0.5 S nanoparticles exhibit the best performance.
[0018] Preferably, the soluble cadmium salt is selected from cadmium acetate dihydrate, cadmium nitrate tetrahydrate, or cadmium chloride pentahydrate.
[0019] Preferably, the soluble manganese salt is selected from manganese acetate tetrahydrate, manganese nitrate hexahydrate, or manganese chloride tetrahydrate.
[0020] Preferably, the sulfur source is selected from thioacetamide or thiourea.
[0021] A second objective of this invention is to provide the aforementioned Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of S composite photocatalyst includes the following steps: Using a solution mixing-self-assembly method, Cu-Ni3S4 nanoparticles and Mn... 0.5 Cd 0.5 The mass ratio of S nanoparticles to Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 Cu-Ni3S4 nanoparticles were co-dispersed in a solvent and first subjected to ultrasonic treatment for 10-30 minutes to allow the Cu-Ni3S4 nanoparticles and Mn nanoparticles to disperse together. 0.5 Cd 0.5 S nanoparticles were fully dispersed in the solvent; then magnetic stirring was performed for 4-6 hours to promote the reaction of Cu-Ni3S4 nanoparticles with Mn. 0.5 Cd 0.5 The two-phase interface of the S nanoparticles is in close contact, and then the solvent is completely evaporated by heat treatment to obtain Cu-Ni3S4 / Mn. 0.5 Cd 0.5 S composite photocatalyst.
[0022] Preferably, the heat treatment temperature is 70℃~85℃.
[0023] Preferably, the solvent is selected from anhydrous ethanol or water.
[0024] A third objective of this invention is to provide the aforementioned Cu-Ni3S4 / Mn 0.5 Cd 0.5 Application of S composite photocatalyst in visible light photocatalytic water splitting for hydrogen production.
[0025] Preferably, Cu-Ni3S4 / Mn is reacted in an airless, sealed quartz reactor. 0.5Cd 0.5 The S-composite photocatalyst was dispersed in an aqueous solution containing 0.25 mol / L Na2S and 0.35 mol / L Na2SO3, and irradiated under a 300W xenon lamp visible light source. Hydrogen gas was then measured by online gas chromatography. The Cu-Ni3S4 / Mn composite photocatalyst was used. 0.5 Cd 0.5 The mass-to-volume ratio of the S composite photocatalyst to an aqueous solution containing 0.25 mol / L Na2S and 0.35 mol / L Na2SO3 is 20 mg to 30 mg: 100 mL.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a Cu-Ni3S4 / Mn 0.5 Cd 0.5 S-composite photocatalyst, composed of Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles are formed through self-assembly composites, Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles form atomically close contacts at the interface, creating a Mott-Schottky heterojunction. This invention constructs a Cu-Ni3S4 / Mn... 0.5 Cd 0.5 The S-heterojunction breaks through the traditional charge migration mode of Schottky junctions, achieving a "reverse migration" of photogenerated electrons from metalloids to semiconductors. This unique behavior was confirmed through a combination of advanced characterization methods, significantly improving the interface charge separation efficiency, effectively suppressing electron-hole recombination, and overcoming the limitations of single Mnn... 0.5 Cd 0.5 The technical bottlenecks of S photocatalysts, such as easy carrier recombination, limited charge separation efficiency of traditional Mott-Schottky heterojunctions, and slow surface reaction kinetics, provide a new approach for designing high-efficiency heterojunction photocatalysts.
[0027] Specifically, under photoexcitation conditions, photogenerated electrons in this Mott-Schottky heterostructure move laterally from metalloid Cu-Ni3S4 nanoparticles with a high work function to semiconductor Mn with a low work function. 0.5 Cd 0.5 The lateral migration of S nanoparticles, also known as "reverse migration," is coupled with the upward shift of the d-band center of Ni3S4 caused by Cu doping (from Ni3S4 / Mn). 0.5 Cd 0.5 The 0.69 eV of S shifts upward to Cu-Ni3S4 / Mn 0.5 Cd 0.5The 0.57 eV of S together result in extremely high interfacial charge separation efficiency and enhanced adsorption and activation capacity for water molecules.
[0028] 2. This invention cleverly combines heterojunction engineering with electronic structure control, and the synergistic effect of the two endows Cu-Ni3S4 / Mn 0.5 Cd 0.5 The S-composite photocatalyst exhibits ultra-high photocatalytic activity. On one hand, the heterojunction structure ensures efficient bulk charge separation; on the other hand, Cu-Ni3S4 nanoparticles and Mn... 0.5 Cd 0.5 After S nanoparticles form a heterojunction at the interface, the d-band center of Mn shifts further upward, enhancing the Cu-Ni3S4 / Mn composite structure. 0.5 Cd 0.5 The S composite photocatalyst's ability to chemically adsorb and activate water molecules improves surface reaction kinetics.
[0029] 3. The Cu-Ni3S4 / Mn of the present invention 0.5 Cd 0.5 The S composite photocatalyst was applied to the photocatalytic water splitting reaction for hydrogen production. Under visible light irradiation, the photocatalytic water splitting hydrogen production rate reached as high as 13.1 mmol / g·h, achieving the desired effect for pure Mn. 0.5 Cd 0.5 The activity of S catalyst is approximately 9 times that of Mn catalyst, and its performance is superior to most previously reported Mn catalysts. 0.5 Cd 0.5 S-based composite materials. Meanwhile, the Cu-Ni3S4 / Mn composite material of the present invention... 0.5 Cd 0.5 The S composite photocatalyst maintained good stability in multiple consecutive cycle tests, demonstrating its potential for practical application.
[0030] 4. The Cu-Ni3S4 / Mn of the present invention 0.5 Cd 0.5 The S composite photocatalyst system does not contain any precious metals (such as Pt and Au). Its main components are Cu, Ni, Mn, Cd, and S, which are relatively abundant. It has a low cost and is in line with the development direction of green and sustainable energy technologies.
[0031] 5. This invention also provides Cu-Ni3S4 / Mn 0.5 Cd 0.5 A method for preparing S-composite photocatalysts is presented, which is simple, reproducible, and easy to scale up. Attached Figure Description
[0032] Figure 1The images show the XRD patterns of Cu-NS, MCS, Cu-NS / MCS of Example 1 and NS of Comparative Example 1, where a represents Cu-NS of Example 1 and NS of Comparative Example 1, and b represents Cu-NS, MCS, and Cu-NS / MCS of Example 1.
[0033] Figure 2 The images shown are SEM and TEM images of MCS, Cu-NS, and Cu-NS / MCS from Example 1, where (a) is Mn 0.5 Cd 0.5 SEM image of S, (b) SEM image of Cu-Ni3S4, (c) SEM image of Cu-Ni3S4 / Mn 0.5 Cd 0.5 SEM image of the S composite photocatalyst, (d) is Mn 0.5 Cd 0.5 TEM images of S, (e) is the TEM image of Cu-Ni3S4, and (f) is the TEM image of Cu-Ni3S4 / Mn. 0.5 Cd 0.5 TEM images of the S composite photocatalyst, (g) represents S, (h) represents Cd, (i) represents Mn, (j) represents Cu, and (k) represents Ni.
[0034] Figure 3 XPS plots, DFT calculated work function plots, UPS plots, and differential charge plots of MCS, Cu-NS, and Cu-NS / MCS in Example 1 are shown, where (a) represents Mn element in MCS and Cu-NS / MCS, (b) represents Cd element in MCS and Cu-NS / MCS, (c) represents Cu element in MCS and Cu-NS / MCS, (d) represents Ni element in MCS and Cu-NS / MCS, (e) represents S element in MCS, Cu-NS, and Cu-NS / MCS, (f) represents the calculated work function plot of MCS, (g) represents the calculated work function plot of Cu-NS, (h) represents the UPS plot of MCS and Cu-NS, and (i) represents the differential charge density plot of MCS and Cu-NS.
[0035] Figure 4 The figures show the photocatalytic hydrogen production performance, catalytic effect comparison, and cycle experiment results of MCS, Cu-NS / MCS in Examples 1-4 and Examples 6-8, NS in Comparative Example 1, and NS / MCS 2:10 in Comparative Example 2. Specifically, (a) shows the hydrogen production rate of MCS, NS, and Cu-NS / MCS in Examples 1-4; (b) shows the hydrogen production rate of MCS and NS. 、Hydrogen production rate graphs for Cu-NS / MCS in Examples 1, 6-8 and NS / MCS 2:10 in Comparative Example 2, (c) shows the hydrogen production rate graphs for MCS, NS, Cu-NS / MCS in Examples 1 and 6-8, (d) shows the comparison of the catalytic effect of Cu-NS / MCS in Example 1 with existing catalysts, and (e) shows the cycle experiment results of Cu-NS / MCS in Example 1.
[0036] Figure 5 The images show in-situ XPS and TDDFT plots of MCS, Cu-NS, and Cu-NS / MCS in Example 1, where (a) is Mn 2p, (b) is Cd 3d, (c) is Cu 2p, (d) is Ni 2p, and (e) is the TDDFT plot of Cu-NS / MCS.
[0037] Figure 6 The proposed Cu-Ni3S4 / Mn is based on theoretical calculations and experimental characterization. 0.5 Cd 0.5 Schematic diagram of the band structure and carrier migration of the Mott-Schottky heterojunction in the S composite photocatalyst under darkness and illumination. Detailed Implementation
[0038] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0039] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased on the market or prepared by existing methods.
[0040] For existing Mn 0.5 Cd 0.5 To address the insufficient charge separation efficiency of S-based photocatalysts and the potential limitations of traditional Schottky heterojunction charge migration modes, this invention provides a novel Cu-Ni3S4 / Mn... 0.5 Cd 0.5 S composite photocatalyst. This Cu-Ni3S4 / Mn 0.5 Cd 0.5The S composite photocatalyst achieves "reverse migration" of charge carriers from metalloid components to semiconductor components under light illumination by constructing a unique Mott-Schottky heterojunction, and couples the regulation effect of Cu doping on the d-band center, thereby synergistically realizing efficient photogenerated charge separation and surface catalytic reaction.
[0041] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will provide a detailed description in conjunction with specific embodiments: Example 1 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of S composite photocatalyst includes the following steps: Preparation of S1 and Cu-Ni3S4 nanoparticles: S11. Dissolve 6.0 mmol nickel sulfate hexahydrate and 0.3 mmol copper nitrate trihydrate together in a mixed solvent of 20 mL water and 20 mL ethylene glycol to obtain the first solution; dissolve 18 mmol thioacetamide in a mixed solvent of 10 mL water and 10 mL ethylene glycol to obtain the second solution.
[0042] S12. Under stirring, the second solution is added dropwise to the first solution. After stirring at room temperature for 4 hours, a suspension is obtained. The suspension is then transferred to a 100 mL reaction vessel and subjected to a solvothermal reaction at 180 °C for 8 hours. The product is washed and dried under vacuum at 60 °C to obtain a black 5% Cu-Ni3S4 powder, denoted as Cu-NS, or 5% Cu-NS.
[0043] S2, Mn 0.5 Cd 0.5 Preparation of S nanoparticles: 0.267 g of Cd(CH3COO)2·2H2O, 0.245 g of Mn(CH3COO)2·4H2O, and 0.451 g of thioacetamide (TAA) were co-dispersed in 35 mL of deionized water and stirred at room temperature for 1 h. The mixture was then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE) and hydrothermally reacted at 180 °C for 24 h. After the reaction, the precipitate was centrifuged and washed three times with deionized water and ethanol, then dried in an oven at 60 °C for 24 h to obtain Mn. 0.5 Cd 0.5 S is denoted as MCS.
[0044] S3. Weigh 0.02 g of 5% Cu-NS and 0.10 g of MCS, add them together to 40 mL of anhydrous ethanol, sonicate for 10 min, stir at room temperature for 4 h, then heat in an 85 °C water bath until the solvent is completely evaporated. After grinding, obtain Cu-Ni3S4 / Mn. 0.5 Cd0.5 S composite photocatalyst, denoted as Cu-NS / MCS, or 5% Cu-NS / MCS 2:10.
[0045] Example 2 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the mass ratio of 5% Cu-NS to MCS in S3 is replaced from 2:10 to 1:10, resulting in Cu-Ni3S4 / Mn. 0.5 Cd 0.5 S composite photocatalyst, denoted as 5% Cu-NS / MCS 1:10.
[0046] Example 3 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the mass ratio of 5% Cu-NS to MCS in S3 is changed from 2:10 to 3:10, resulting in Cu-Ni3S4 / Mn. 0.5 Cd 0.5 S composite photocatalyst, denoted as 5% Cu-NS / MCS 3:10.
[0047] Example 4 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the mass ratio of 5% Cu-NS to MCS in S3 is changed from 2:10 to 4:10, resulting in Cu-Ni3S4 / Mn. 0.5 Cd 0.5 S composite photocatalyst, denoted as 5% Cu-NS / MCS 4:10.
[0048] Example 5 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the molar amount of copper nitrate trihydrate in S11 is replaced from 0.3 mmol to 0.06 mmol, resulting in 1% Cu-Ni3S4 powder, denoted as 1% Cu-NS; finally, Cu-Ni3S4 / Mn is obtained. 0.5 Cd 0.5 S composite photocatalyst, denoted as 1% Cu-NS / MCS 2:10.
[0049] Example 6 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the molar amount of copper nitrate trihydrate in S11 is replaced from 0.3 mmol to 0.18 mmol, resulting in 3% Cu-Ni3S4 powder, denoted as 3% Cu-NS; finally, Cu-Ni3S4 / Mn is obtained. 0.5 Cd 0.5 S composite photocatalyst, denoted as 3% Cu-NS / MCS 2:10.
[0050] Example 7 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the molar amount of copper nitrate trihydrate in S11 is replaced from 0.3 mmol to 0.42 mmol, resulting in 7% Cu-Ni3S4 powder, denoted as 7% Cu-NS; finally, Cu-Ni3S4 / Mn is obtained. 0.5 Cd 0.5 S composite photocatalyst, denoted as 7% Cu-NS / MCS 2:10.
[0051] Example 8 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of the S composite photocatalyst is the same as that in Example 1, except that the molar amount of copper nitrate trihydrate in S11 is replaced from 0.3 mmol to 0.6 mmol, resulting in 9% Cu-Ni3S4 powder, denoted as 9% Cu-NS; finally, Cu-Ni3S4 / Mn is obtained. 0.5 Cd 0.5 S composite photocatalyst, denoted as 9% Cu-NS / MCS 2:10.
[0052] Example 9 A Cu-Ni3S4 / Mn 0.5 Cd 0.5 The preparation method of S composite photocatalyst includes the following steps: Preparation of S1 and Cu-Ni3S4 nanoparticles: S11. Dissolve 6.0 mmol nickel sulfate hexahydrate and 0.6 mmol copper nitrate trihydrate together in a mixed solvent of 20 mL water and 40 mL ethylene glycol to obtain the first solution; dissolve 27 mmol thioacetamide in a mixed solvent of 10 mL water and 10 mL ethylene glycol to obtain the second solution.
[0053] S12. Under stirring, the second solution is added dropwise to the first solution. After stirring at room temperature for 6 hours, a suspension is obtained. The suspension is then transferred to a 100 mL reactor and subjected to a solvothermal reaction at 170 °C for 10 hours. The product is washed and dried under vacuum at 60 °C to obtain a black 5% Cu-Ni3S4 powder, denoted as Cu-NS, or 5% Cu-NS.
[0054] S2, Mn 0.5 Cd 0.5 Preparation of S nanoparticles: 0.267 g of Cd(CH3COO)2·2H2O, 0.245 g of Mn(CH3COO)2·4H2O, and 0.5412 g of TAA were dispersed in 35 mL of deionized water and stirred at room temperature for 1 h. The mixture was then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE) and hydrothermally reacted at 160 °C for 20 h. After the reaction, the precipitate was centrifuged and washed three times with deionized water and ethanol, then dried in an oven at 60 °C for 24 h to obtain Mn. 0.5 Cd 0.5 S is denoted as MCS.
[0055] S3. Weigh 0.02 g of 5% Cu-NS and 0.10 g of MCS, add them together to 40 mL of anhydrous ethanol, sonicate for 10 min, stir at room temperature for 4 h, then heat in a 70 °C water bath until the solvent is completely evaporated. After grinding, obtain Cu-Ni3S4 / Mn. 0.5 Cd 0.5 S-composite photocatalyst, denoted as Cu-NS / MCS.
[0056] Comparative Example 1 A method for preparing Ni3S4 includes the following steps: S1. Dissolve 6.0 mmol of nickel sulfate hexahydrate in a mixed solvent consisting of 20 mL of water and 20 mL of ethylene glycol to obtain the first solution; dissolve 18 mmol of thioacetamide in a mixed solvent consisting of 10 mL of water and 10 mL of ethylene glycol to obtain the second solution.
[0057] S2. Under stirring, the second solution was added dropwise to the first solution. After stirring at room temperature for 4 hours, a suspension was obtained. The suspension was then transferred to a 100 mL reactor and subjected to a solvothermal reaction at 180 °C for 8 hours. The product was washed and dried under vacuum at 60 °C to obtain Ni3S4 powder, denoted as NS.
[0058] Comparative Example 2 A Ni3S4 / Mn 0.5 Cd 0.5The preparation method of the S composite photocatalyst is the same as that in Example 1, except that Cu-NS in S3 is replaced with NS obtained in Comparative Example 1 to obtain Ni3S4 / Mn 0.5 Cd 0.5 S composite photocatalyst, denoted as NS / MCS 2:10.
[0059] application: Cu-Ni3S4 / Mn was prepared in Examples 1 to 8 of this invention. 0.5 Cd 0.5 The S composite photocatalyst exhibits parallel effects, and its photocatalytic performance in water splitting for hydrogen production was first investigated: With Cu-Ni3S4 / Mn 0.5 Cd 0.5 Using S composite photocatalyst, NS, MCS, and NS / MCS as catalysts, 30 mg of catalyst was dispersed in 100 mL of aqueous solution containing 0.25 mol / L Na2S and 0.35 mol / L Na2SO3 in a 150 mL sealed quartz reactor. Before the reaction, the air was purged with nitrogen. Subsequently, a 300 W xenon lamp (equipped with a 420 nm filter) was used as a visible light source for irradiation. The generated hydrogen gas was quantitatively analyzed by online gas chromatography (TCD detector). The test duration was 2.5 h.
[0060] Depend on Figure 1 It is concluded that the Cu-Ni3S4 / Mn of the present invention 0.5 Cd 0.5 The S composite photocatalyst is a pure phase, and there is no possibility of physical mixing.
[0061] Depend on Figure 2 It is concluded that Mn 0.5 Cd 0.5 S, Cu-Ni3S4 and Cu-Ni3S4 / Mn 0.5 Cd 0.5 S exhibits an irregular nanosheet morphology. This morphological feature originates from the synergistic effect of the intrinsic driving force of the material's layered crystal structure and the external driving force of the hydrothermal synthesis environment: the inherent anisotropic growth tendency of the layered structure drives the crystal to preferentially orient along specific crystal planes, while factors such as temperature field, solvent polarity, and surfactants in the hydrothermal system regulate the nucleation rate and crystal plane growth kinetics. The coupling of the two ultimately forms a two-dimensional sheet morphology.
[0062] Performance results: Depend on Figure 4 From (a), we find that the hydrogen production rate of MCS is approximately 1.44 mmol / g·h, and the hydrogen production rate of NS / MCS 2:10 increases to 7.7 mmol / g·h; from Figure 4As shown in (b) and (c), 5% Cu-NS / MCS 2:10 exhibits optimal activity, with a hydrogen production rate as high as 13.1 mmol / g·h, approximately nine times that of MCS. Further comparison reveals that the Cu-Ni3S4 / Mn provided by this invention... 0.5 Cd 0.5 The S-composite photocatalyst has the highest hydrogen production efficiency.
[0063] Depend on Figure 4 From (d), it is concluded that Cu-NS / MCS performs significantly better than Mn-NS / MCS. 0.5 Cd 0.5 Other existing catalysts based on S.
[0064] like Figure 4 As shown in (e), by comparing Mn 0.5 Cd 0.5 S, Cu-Ni3S4 and Cu-Ni3S4 / Mn 0.5 Cd 0.5 S was found to contain 5% Cu-Ni3S4 / Mn 0.5 Cd 0.5 S (2:10) showed the best hydrogen production effect, maintaining a high hydrogen production efficiency even after 5 cycles, indicating good stability.
[0065] Depend on Figure 3 It is concluded that, by comparing Mn 0.5 Cd 0.5 S and Cu-Ni3S4 were found to have Cu-Ni3S4 / Mn in the ground state. 0.5 Cd 0.5 The direction of electron transfer in S is from Mn. 0.5 Cd 0.5 S is transferred to Cu-Ni3S4 and Mn. 0.5 Cd 0.5 The work functions of S and Cu-Ni3S4 are 4.78 eV and 5.81 eV, respectively.
[0066] like Figure 5 As shown, calculations using in-situ XPS and TDDFT yielded the following results for Cu-Ni3S4 / Mn in the excited state. 0.5 Cd 0.5 In the S heterojunction, electrons are transferred from Cu-Ni3S4 to Mn. 0.5 Cd 0.5 S, which is related to Figure 3 In XPS, electron transfer occurs in the opposite direction. However, in traditional Schottky junctions, electrons should transfer from the semiconductor to the metal-like state in both the ground and excited states. Based on these results, a theory of reverse electron migration is proposed.
[0067] Figure 6 Cu-Ni3S4 / Mn0.5 Cd 0.5 Theoretical simulations of the S-type heterojunction demonstrate the changes in electron transfer behavior before and after illumination. Before contact, based on the characteristics of Schottky junctions, electrons in equilibrium should transfer from Mn, which has a lower work function. 0.5 Cd 0.5 Photogenerated electrons (S) spontaneously transfer to the Cu-NS junction, which has a higher work function. Upon illumination, in the Cu-NS / MCS heterojunction, hot electrons generated on the Cu-NS side are driven by the built-in electric field at the interface to migrate towards the valence band top (VBM) of the MCS. Simultaneously, the upward bending of the conduction band bottom (CBM) caused by the Schottky barrier, combined with the blocking effect of the strong built-in electric field, effectively suppresses the backflow of photogenerated electrons from the MCS conduction band to the Cu-NS, ensuring their stable anchoring on the CBM of the MCS. On the other hand, the upward bending of the valence band top and the built-in electric field synergistically promote the directional transfer of holes from the MCS valence band to the Cu-NS—holes migrate along the direction of the electric field to the Cu-NS side. Therefore, under the influence of the strong built-in electric field, the Cu-NS / MCS heterojunction achieves a carrier spatial distribution mode opposite to that of a traditional Schottky junction: electrons are enriched in the semiconductor MCS while holes accumulate in the metalloid Cu-NS, while maintaining high interface charge separation efficiency.
[0068] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.
Claims
1. A Cu-Ni3S4 / Mn 0.5 Cd 0.5 S composite photocatalyst, characterized in that... Composed of Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles are formed through self-assembly composites, Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles form Mott-Schottky junctions; Cu-Ni3S4 nanoparticles are Cu-doped Ni3S4 nanoparticles with a Cu doping concentration of 1 mol% to 10 mol%. Among them, Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 The mass ratio of S nanoparticles is 1~4:
10.
2. The Cu-Ni3S4 / Mn according to claim 1 0.5 Cd 0.5 S composite photocatalyst, characterized in that... In Cu-Ni3S4, the Cu doping concentration is 5 mol%, and the Cu-Ni3S4 nanoparticles are mixed with Mn. 0.5 Cd 0.5 The mass ratio of S nanoparticles is 2:
10.
3. The Cu-Ni3S4 / Mn according to claim 1 0.5 Cd 0.5 S composite photocatalyst, characterized in that... Cu-Ni3S4 nanoparticles were prepared according to the following steps: Water and ethylene glycol are mixed to obtain a mixed solvent; A first solution is obtained by dissolving a soluble nickel salt and a soluble copper salt together in a mixed solvent; a second solution is obtained by dissolving a sulfur source in the mixed solvent. The second solution was added dropwise to the first solution, and the mixture was stirred at room temperature for 4 to 6 hours to obtain a suspension. The suspension was then subjected to a solvothermal reaction at 170℃~180℃ for 8h~10h to obtain Cu-Ni3S4 nanoparticles.
4. The Cu-Ni3S4 / Mn according to claim 3 0.5 Cd 0.5 S composite photocatalyst, characterized in that... The volume ratio of water to ethylene glycol is 1:1~2.
5. The Cu-Ni3S4 / Mn according to claim 3 0.5 Cd 0.5 S composite photocatalyst, characterized in that... The molar ratio of soluble nickel salt, soluble copper salt and sulfur source is 100:1~10:200~300.
6. The Cu-Ni3S4 / Mn according to claim 1 0.5 Cd 0.5 S composite photocatalyst, characterized in that... Mn 0.5 Cd 0.5 S nanoparticles were prepared according to the following steps: A precursor solution was prepared by dissolving or dispersing a soluble cadmium salt, a soluble manganese salt, and a sulfur source in water; the precursor solution was then subjected to a hydrothermal reaction to obtain Mn. 0.5 Cd 0.5 S nanoparticles; wherein the molar ratio of soluble cadmium salt, soluble manganese salt and sulfur source is 1:1:4~6; The hydrothermal reaction conditions are: hydrothermal reaction at 160℃~180℃ for 20h~24h.
7. A Cu-Ni3S4 / Mn according to claim 1 0.5 Cd 0.5 The preparation method of S composite photocatalyst is characterized by, Includes the following steps: According to Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 The mass ratio of S nanoparticles to Cu-Ni3S4 nanoparticles and Mn 0.5 Cd 0.5 S nanoparticles were co-dispersed in a solvent and then heated to completely evaporate the solvent, yielding Cu-Ni3S4 / Mn. 0.5 Cd 0.5 S composite photocatalyst.
8. The preparation method according to claim 7, characterized in that, The heat treatment temperature is 70℃~85℃.
9. A Cu-Ni3S4 / Mn according to claim 1 0.5 Cd 0.5 Application of S composite photocatalyst in visible light photocatalytic water splitting for hydrogen production.
10. The application according to claim 9, characterized in that, Application method: In an airless, closed reactor, Cu-Ni3S4 / Mn 0.5 Cd 0.5 The S composite photocatalyst was dispersed in an aqueous solution containing 0.25 mol / L Na2S and 0.35 mol / L Na2SO3, irradiated under a 300W xenon lamp visible light source, and hydrogen was determined by online gas chromatography. Among them, Cu-Ni3S4 / Mn 0.5 Cd 0.5 The mass-to-volume ratio of the S composite photocatalyst to an aqueous solution containing 0.25 mol / L Na2S and 0.35 mol / L Na2SO3 is 20 mg to 30 mg: 100 mL.