A method for preparing Cu2S-CdS heterojunction nanosheets
By using non-toxic solvents such as CuSCN and oleylamine to prepare Cu2S-CdS heterojunction nanosheets at room temperature, the problems of high-temperature thermal reduction and toxic thiols were solved, achieving low-cost, high-efficiency nanosheet preparation and improved electrocatalytic performance.
Patent Information
- Application Number
- CN202411220793.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-02
- Publication Date
- 2025-12-19
- Estimated Expiration
- 2044-09-02
AI Technical Summary
Existing methods for preparing Cu2S-CdS nanosheets typically require high-temperature thermal reduction and toxic thiols as the sulfur source, resulting in high energy consumption and environmental unfriendliness, making it difficult to achieve large-scale production.
Cu2S hexagonal nanosheets were prepared at room temperature by using CuSCN as a non-toxic S and Cu source, combined with solvents such as oleylamine, toluene and methanol, and reacted with Cd(NO3)2·4H2O to form Cu2S-CdS heterojunction nanosheets, thus avoiding high-temperature treatment.
We have achieved non-toxic, low-cost, and easily scalable Cu2S-CdS heterojunction nanosheets with good morphology control and electrocatalytic CO2 reduction performance, which significantly improves the current density and stability of the catalyst.
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Figure CN119332283B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of electrocatalytic reduction, in particular to a preparation method of Cu2S-CdS heterojunction nanosheets. BACKGROUND
[0002] Nanoheterostructures (NHs) are composed of two or more components fused into a nanoparticle (NP). There is growing interest in fabricating these structures, which will play a greater role in important applications such as chemical catalysis and solar energy. At present, existing synthesis methods are manufactured by top-down, surface growth, template or nanoreactor technology, which usually requires special equipment and can only produce microgram quantities of NPs.
[0003] The cation exchange (CE) method is a general and effective method for preparing new colloidal nanoheterostructures (NHs) and is widely used. When making heterojunctions, since it handles multiple elements and multiple materials with good interfaces, an appropriate method design must be adopted, and it is found that the ion exchange method is very effective in this case. The performance of the catalytic reaction can be further improved by improving the surface environment of the catalyst and providing catalytic sites.
[0004] The conditions required for nanocrystal cation exchange to occur are mild, as the reaction occurs within seconds to minutes, at temperatures ranging from below room temperature to several hundred degrees, much lower than the temperatures usually required to produce crystalline nanoparticles or bulk powders. Therefore, the anion sublattice structure does not rearrange as the cations diffuse, resulting in a product that retains key features of the precursor crystal structure. The size of the anion is much larger than that of the cation, and the sublattice of the anion remains unchanged, which can well ensure the continuity of the morphology. In some cases, this sublattice structure retention will lead to the formation of crystal structures that are not the thermodynamically preferred phase, as they are kinetically trapped during the cation exchange process.
[0005] Most of the existing cation exchange methods for preparing Cu2S-CdS nanosheets use double-tube, high-temperature thermal reduction, which has high energy consumption and requires a certain temperature, and most of the current Cu2S synthesis methods use toxic S sources such as mercaptans including tertiary dodecanethiol or dodecanethiol.
[0006] Therefore, how to develop a new preparation method of Cu2S-CdS heterojunction nanosheets is a problem that those skilled in the art need to solve. SUMMARY
[0007] Therefore, the purpose of the present application is to provide a preparation method of Cu2S-CdS heterojunction nanosheets, which can prepare size-controllable nanocatalysts by a simple method.
[0008] In order to achieve the above object, the present application adopts the following technical solutions:
[0009] A preparation method of Cu2S-CdS heterojunction nanosheet, specifically comprising the following steps:
[0010] (1) vacuum heating CuSCN (cuprous thiocyanate) and oleylamine (cis-oleyl primary amine), saturated Ar is introduced, heating reaction is carried out, and the system is cooled to room temperature, then toluene and methanol are added, centrifugation, washing, and drying are carried out to obtain Cu2S hexagonal nanosheet;
[0011] (2) mixing Cd(NO3)2 4H2O (cadmium nitrate tetrahydrate) methanol solution, tetrahydrofuran, TOP (trioctylphosphine) and Cu2S hexagonal nanosheet toluene solution, degassing treatment, reaction in inert gas atmosphere, centrifugation, washing, ultrasonic, centrifugation, washing, dispersion, centrifugation, and drying are carried out to obtain Cu2S-CdS heterojunction nanosheet.
[0012] Further, in the step (1), the mass concentration of CuSCN is 95%-99%, preferably 99%; the mass concentration of oleylamine is 98%-99.99%, preferably 98%; and the amount ratio of CuSCN, oleylamine, toluene and methanol is 2.5mmol:15.20mmol:15mL:25mL.
[0013] The above further beneficial effects are adopted, and the CuSCN can serve as a Cu source and provide S, and is non-toxic, replacing the toxic and irritating-smelling mercaptan.
[0014] Oleylamine: used as a complexing agent and a solvent, can form a metal and oleylamine complex with CuSCN, and further exchange the metal to form a ligand.
[0015] Toluene: used as an organic solvent, has good solubility, and is used for dissolving Cu2S, and has good solubility.
[0016] Methanol: used as an organic solvent, can quickly dissolve Cd(NO3)2 4H2O, has good dispersibility, and is beneficial to better dissolution.
[0017] Further, in the step (1), the vacuum heating temperature is 95-105℃, preferably 100℃, the time is 5-15min, preferably 10min; the heating reaction temperature is 220-250℃, preferably 240℃, the time is 25-35min, preferably 30min; and the centrifugation speed is 4000-10000rpm, preferably 4000rpm, the time is 2-10min, preferably 5min.
[0018] Further, in the step (1), the reagent for washing is ethanol / toluene mixture; the ratio of ethanol and toluene is (9-11) mL:(4-6) mL, preferably 10 mL:5 mL.
[0019] Further, in the step (1), the drying temperature is 60-75℃, preferably 70℃, and the time is 3-6h, preferably 3h.
[0020] Further, in the step (2), the concentration of Cd(NO3)2·4H2O methanol solution is 0.1 mol / L; the concentration of Cu2S hexagonal nanosheet toluene solution is 0.0786 mol / L (2 mL toluene is added to 25 mg Cu2S hexagonal nanosheet); the ratio of Cd(NO3)2·4H2O methanol solution, tetrahydrofuran, TOP and Cu2S hexagonal nanosheet toluene solution is (0.8-1.2) mL:(0.8-1.2) mL:(0.5-1) mL:(1.5-2.5) mL, preferably 1 mL:1 mL:0.5 mL:2 mL.
[0021] The above further beneficial effects are used in that Cd(NO3)2·4H2O is used to provide Cd source. According to the soft and hard acid base theory, soft acid Cu + is extracted and replaced by hard acid, for example, metal chalcogenide Cd 2+ as soft base. TOP as an extractant extracts soft acid Cu + , and Cd 2+ can form complex with oleylamine; at the same time, TOP is also a reducing agent. These compounds can provide P lone pair electrons and form monodentate terminal metal-PR3 group (σ bonding to bind metal ions. Unlike amine ligands that can only form σ bonds, phosphines can also be good π acceptors, so they can coordinate metal cations through π bonds, the degree of which depends on the nature of the R groups. For these reasons, phosphines can be very high field ligands and can form strong metal-ligand (ML) bonds. Oleylamine (OA) promotes the extraction of Cd 2+ ions by forming stable Cd-OA complexes.
[0022] Further, in the step (2), the reaction time is 22-24h, preferably 23h.
[0023] Further, in the step (2), the reagent for washing is toluene, and the amount is 1-2 mL, preferably mL.
[0024] Further, in the step (2), the dispersing reagent is toluene, and the amount is 0.5-1 mL, preferably 1 mL.
[0025] Further, in the step (2), the temperature for drying is 60-75 DEG C, preferably 70 DEG C, and the time is 5-8h, preferably 6h.
[0026] Via the technical solution, compared with the prior art, the application has the following beneficial effects:
[0027] The application does not use toxic S source, but uses CuSCN as S source and Cu source to prepare Cu2S matrix, and applies the Cu2S matrix to cation exchange of electrocatalytic CO2 reduction Cu2S, and uses room temperature stirring to prepare hexagonal nanosheet with good morphology, uniform size and stability. BRIEF DESCRIPTION OF DRAWINGS
[0028] Figure 1 It is a flowchart of the preparation method of Cu2S-CdS heterojunction nanosheet;
[0029] Figure 2 It is a scanning electron microscope image of Cu2S-CdS-2 heterojunction nanosheet;
[0030] Figure 3 It is an LSV curve;
[0031] Figure 4 It is a gaseous and liquid product distribution diagram, CO and H2 faradic efficiency diagram and current density diagram;
[0032] Figure 5 It is a FE CO and i-t data, in-situ XRD diagram, Cu Auger spectrum, electron microscope image and high-resolution characterization diagram. DETAILED DESCRIPTION
[0033] The technical solutions in the embodiments of the application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.
[0034] Embodiment 1
[0035] The preparation method of Cu2S-CdS heterojunction nanosheet, as shown in Figure 1 , specifically includes the following steps:
[0036] (1) Put 2.5 mmol of CuSCN with a mass concentration of 99% and 15.20 mmol of oleylamine with a mass concentration of 98% into a 100 mL three-necked flask, heat under vacuum at 100°C for 10 min, introduce saturated Ar, then place in a preheated hot oil bath at 240°C to heat for 30 min, cool to room temperature, add 15 mL of toluene and 25 mL of methanol, centrifuge at a speed of 4000 rpm for 5 min, wash with 10 mL of ethanol / 5 mL of toluene, and finally dry in a vacuum drying box at 70°C for 3 h to obtain Cu2S hexagonal nanosheets;
[0037] (2) Mix 1 mL of Cd(NO3)2 4H2O methanol solution with a concentration of 0.1 mol / L, 1 mL of tetrahydrofuran, 0.5 mL of TOP, and 2 mL of Cu2S hexagonal nanosheet toluene solution with a concentration of 0.0786 mol / L, degas to prevent oxidation, react in an inert atmosphere of nitrogen and argon for 23 h, centrifuge, wash with 2 mL of toluene, ultrasonic, centrifuge to remove organic residues, wash with 2 mL of toluene twice to remove excess cationic salt, disperse in 1 mL of toluene, centrifuge, and finally dry in a vacuum drying box at 70°C for 6 h to obtain Cu2S-CdS heterojunction nanosheets.
[0038] Example 2
[0039] The preparation method of the Cu2S-CdS heterojunction nanosheets, as shown in Figure 1 , specifically includes the following steps:
[0040] (1) Put 2.5 mmol of CuSCN with a mass concentration of 95% and 15.20 mmol of oleylamine with a mass concentration of 98% into a 100 mL three-necked flask, heat under vacuum at 95°C for 5 min, introduce saturated Ar, then place in a preheated hot oil bath at 220°C to heat for 25 min, cool to room temperature, add 15 mL of toluene and 25 mL of methanol, centrifuge at a speed of 4000 rpm for 2 min, wash with 9 mL of ethanol / 6 mL of toluene, and finally dry in a vacuum drying box at 60°C for 3 h to obtain Cu2S hexagonal nanosheets;
[0041] (2) 0.8 mL of Cd(NO3)2 4H2O methanol solution with a concentration of 0.1 mol / L, 0.8 mL of tetrahydrofuran, 0.5 mL of TOP and 1.5 mL of Cu2S hexagonal nanosheet toluene solution with a concentration of 0.0786 mol / L were mixed, degassed to prevent oxidation, reacted for 22 h in an inert atmosphere of nitrogen and argon, centrifuged, washed with 1 mL of toluene, ultrasonicated, centrifuged to remove organic residues, washed with 1 mL of toluene twice to remove excess cationic salts, dispersed in 0.5 mL of toluene, centrifuged and finally dried in a vacuum drying box at 60°C for 5 h to obtain Cu2S-CdS heterojunction nanosheets.
[0042] Example 3
[0043] The preparation method of Cu2S-CdS heterojunction nanosheets, as shown in Figure 1 , specifically includes the following steps:
[0044] (1) 2.5 mmol of CuSCN with a mass concentration of 99% and 15.20 mmol of oleylamine with a mass concentration of 99.99% were put into a 100 mL three-necked flask, heated under vacuum at 105°C for 15 min, saturated Ar was introduced, then heated in a preheated hot oil bath at 250°C for 35 min, cooled to room temperature, 15 mL of toluene and 25 mL of methanol were added, centrifuged at a speed of 10000 rpm for 10 min, washed with 11 mL of ethanol / 4 mL of toluene and finally dried in a vacuum drying box at 75°C for 6 h to obtain Cu2S hexagonal nanosheets;
[0045] (2) 1.2 mL of Cd(NO3)2 4H2O methanol solution with a concentration of 0.1 mol / L, 1.2 mL of tetrahydrofuran, 1 mL of TOP and 2.5 mL of Cu2S hexagonal nanosheet toluene solution with a concentration of 0.0786 mol / L were mixed, degassed to prevent oxidation, reacted for 24 h in an inert atmosphere of nitrogen and argon, centrifuged, washed with 2 mL of toluene, ultrasonicated, centrifuged to remove organic residues, washed with 2 mL of toluene twice to remove excess cationic salts, dispersed in 1 mL of toluene, centrifuged and finally dried in a vacuum drying box at 75°C for 8 h to obtain Cu2S-CdS heterojunction nanosheets.
[0046] Performance test
[0047] The Cu2S prepared in Example 1, Cu2S-CdS-1 prepared in Example 1, Cu2S-CdS-2 prepared in Example 2, Cu2S-CdS-3 prepared in Example 3 and a certain commercially available CdS were respectively subjected to the following tests.
[0048] 1. Scanning electron microscope image
[0049] The scanning electron microscope image of Cu2S-CdS-2 heterojunction nanosheet is shown in Figure 2 .
[0050] It can be seen from Figure 2 that Cu2S-CdS-2 is well-dispersed and uniform in size, and is an ultrathin hexagonal nanosheet. It is proved that the method is stable, and can prepare uniform and stable hexagonal nanosheets.
[0051] 2, LSV curve
[0052] Linear sweep voltammetry (LSV) is used to detect the electrochemical activity of the catalyst, and the scanning rate is 10 mV s -1 , and the scanning range is 0V-1.2V vs.RHE.
[0053] The LSV curves of Cu2S, Cu2S-CdS-1, Cu2S-CdS-2, Cu2S-CdS-3 and CdS are shown in Figure 3 a, and the LSV curves of Cu2S-CdS-2 in CO2 and N2 are shown in Figure 3 b.
[0054] It can be seen from Figure 3 a that compared with Cu2S and CdS, the current density of the Cu2S-CdS heterojunction nanosheet of the application is significantly increased. In addition, with the increase of the CdS content during the cation exchange, the activity shows a volcano trend, which is attributed to the effect of the moderate heterojunction. That is, by constructing a moderate heterojunction interface of Cu2S-CdS, the surface charge distribution of the material is significantly changed, thereby affecting the adsorption energy of the reaction intermediates. The moderate heterojunction promotes the charge transfer between the active substances, and shows good electrocatalytic CO2 activity.
[0055] It can be seen from Figure 3 b that under the CO2 atmosphere, the current density of the Cu2S-CdS-2 heterojunction catalyst is significantly higher than that under the N2 atmosphere, indicating that it has excellent CO2 reduction capacity.
[0056] 3, gaseous and liquid product distribution diagram, CO and H2 faradaic efficiency diagram and current density diagram
[0057] The gaseous and liquid product distribution diagrams of Cu2S, Cu2S-CdS-2 and CdS are shown in Figure 4 a-c, respectively, and the CO faradaic efficiency diagram, H2 faradaic efficiency diagram and partial current density diagram of the CO application potential of Cu2S, Cu2S-CdS-1, Cu2S-CdS-2, Cu2S-CdS-3 and CdS are shown in Figure 4 d-f, respectively.
[0058] It can be seen fromFigure 4 It can be seen that the CO2RR activity of the Cu2S-CdS heterojunction nanosheet of the application is significantly enhanced compared with Cu2S and CdS, and the overall HER is significantly inhibited.
[0059] 4、FE CO and i-t data, in-situ XRD pattern, Cu Auger spectrum, electron microscopy image and high-resolution characterization image
[0060] FE of Cu2S-CdS-2 electrolyzed at-0.77V vs.RHE potential for 45h CO and i-t data as shown in a of Figure 5 , the in-situ XRD pattern, Cu Auger spectrum, electron microscopy image and high-resolution characterization image of Cu2S-CdS-2 after electrolysis in CO2-saturated 0.5M KHCO3 solution are shown in b-e of Figure 5 , respectively.
[0061] It can be seen from a of Figure 5 that Cu2S-CdS-2 can be stably operated in H-type electrolytic cell at a current density of about 10mA cm -2 for at least 45h. After 45h consumption at-0.77V vs.RHE, the CO content was measured, and the FE from 5h to 45h was basically unchanged (84% at 5h and 80% at 45h), which indicates that Cu2S-CdS-2 has good stability and excellent electrochemical activity.
[0062] It can be seen from b-c of Figure 5 that XRD is further used to prove the stability of the crystal structure of Cu2S-CdS-2 during electrolysis. The spectrum of Cu2S-CdS-2 shows that 32.0° and 46.0° belong to (200)(220) crystal face (PDF#02-1280), and the new 2θ diffraction peaks at 43.91° and 51.91° belong to (110) and (112) crystal face of CdS (PDF#02-0549), which confirms that Cu2S-CdS catalyst is successfully synthesized by cation exchange, and no phase transition occurs during the entire electrolysis process, which further indicates that the catalyst has good stability.
[0063] It can be seen from d-e of Figure 5 that Cu2S-CdS-2 can still maintain stable hexagonal nanosheet morphology after electrolysis.
[0064] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. Use of Cu2S-CdS heterojunction nanoplatelets in electrocatalytic CO2 reduction, characterized in that, The preparation method of the Cu2S-CdS heterojunction nanosheet specifically comprises the following steps: (1) vacuum heating of CuSCN and oleylamine, saturated Ar is introduced, heating reaction is carried out, cooling to room temperature, adding toluene and methanol, centrifugation, washing, drying, obtaining Cu2S hexagonal nanosheet; (2) mixing Cd(NO3)2 4H2O methanol solution, tetrahydrofuran, TOP and Cu2S hexagonal nanosheet toluene solution, degassing treatment, reaction in inert gas atmosphere, centrifugation, washing, ultrasonic, centrifugation, washing, dispersion, centrifugation, drying, obtaining the Cu2S-CdS heterojunction nanosheet.
2. Use of a Cu2S-CdS heterojunction nanosheet in electrocatalytic CO2 reduction according to claim 1, characterized in that, In step (1), the mass concentration of CuSCN is 95%-99%; the mass concentration of oleylamine is 98%-99.99%; the amount ratio of CuSCN, oleylamine, toluene and methanol is 2.5 mmol:15.20 mmol:15 mL:25 mL.
3. Use of a Cu2S-CdS heterojunction nanosheet in electrocatalytic CO2 reduction according to claim 1, characterized in that, In step (1), the temperature of vacuum heating is 95-105℃, and the time is 5-15 min; the temperature of heating reaction is 220-250℃, and the time is 25-35 min; the rotation speed of centrifugation is 4000-10000 rpm, and the time is 2-10 min.
4. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (1), the reagent for washing is ethanol / toluene mixed solution; the amount ratio of ethanol and toluene is (9-11) mL:(4-6) mL.
5. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (1), the drying temperature is 60-75℃, and the time is 3-6 h.
6. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (2), the concentration of Cd(NO3)2 4H2O methanol solution is 0.1 mol / L; the concentration of Cu2S hexagonal nanosheet toluene solution is 0.0786 mol / L; the amount ratio of Cd(NO3)2 4H2O methanol solution, tetrahydrofuran, TOP and Cu2S hexagonal nanosheet toluene solution is (0.8-1.2) mL:(0.8-1.2) mL:(0.5-1) mL:(1.5-2.5) mL.
7. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (2), the reaction time is 22-24 h.
8. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (2), the reagent for washing is toluene, and the amount is 1-2 mL.
9. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (2), the reagent for dispersion is toluene, and the amount is 0.5-1 mL.
10. Use of a Cu2S-CdS heterojunction nanosheet according to claim 1 in electrocatalytic CO2 reduction, characterized in that, In step (2), the drying temperature is 60-75℃, and the time is 5-8 h.