A copper-based molecular sieve photocatalyst, a preparation method and application thereof
By introducing Cu-SACs into the channels of L-type molecular sieves and functionalizing copper single-atom catalysts with thioacetamide, the problems of high overpotential and low stability of copper-based catalysts in CO2 reduction reaction were solved, and the efficient photocatalytic reduction of carbon dioxide to formic acid was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGXI NORMAL UNIV
- Filing Date
- 2024-03-12
- Publication Date
- 2026-04-10
AI Technical Summary
Existing copper-based catalysts suffer from high overpotential, poor selectivity, and low stability in CO2 reduction reactions. Furthermore, the activity of constructing single-atom catalysts is not high, making it difficult to effectively promote charge separation and transport.
Cu2+ was introduced into the channels of an L-type molecular sieve using a hydrothermal method. Thioacetamide was used as a sulfur source to functionalize the single-atom active centers of copper, thus preparing Cu-SACs. This process promoted charge separation and electron transfer, forming a highly efficient Cux-S@L-type photocatalyst.
A copper-based molecular sieve photocatalyst with high catalytic activity and stability has been developed. It can reduce carbon dioxide to formic acid without the need for other agents, with low cost, high yield, and multiple catalytic active sites. The yield of photocatalytic reduction of carbon dioxide to formic acid reaches 69.7 μmol g-1h-1.
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Figure CN118059935B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of catalysts, and particularly relates to a copper-based molecular sieve photocatalyst and a preparation method and application thereof. BACKGROUND
[0002] The photocatalytic CO2 reduction reaction (CO2RR) converts CO2 into high-value chemicals and carbon-neutral fuels, which is a key way to reduce the concentration of CO2 in the atmosphere and solve the energy crisis. In the past few decades, important progress has been made in the research of photocatalytic materials. Most catalysts can photocatalytically reduce CO2 to CO, but it is still a challenge to photocatalytically reduce CO2 to products other than CO due to the linear structure of CO2 and the high C-O bond energy (806 kJ mol -1 ).
[0003] Copper-based catalysts are currently the "star" materials for catalyzing the reduction of CO2 to hydrocarbons and C2+ products. Introducing effective catalytic sites (co-catalysts) to promote charge separation is a common strategy to meet the demand for efficient photocatalysis. However, due to the formation of C-C bonds and hydrogenation deoxidation during the reaction, copper metal and oxides have high overpotential, poor selectivity, and low stability, which limit their application. Single-atom catalysts (SACs) are a powerful heterogeneous catalyst with maximum atomic efficiency. Constructing Cu-SACs on supports to promote charge separation and transmission is an effective way. Significant progress has been made in the construction of SACs, such as the team of Sun Chengyong of Sun Yat-Sen University, which has successfully realized SACs with crystalline MOFs as supports (Chem. Sci. 2017, 8, 775; Appl. Catal. B 2018, 231, 173; Chem. Sci., 2019, 10, 10577; J. Am. Chem. Soc. 2020, 142, 14548; ACS Catal. 2022, 12, 3604; J. Am. Chem. Soc. 2022, 144, 22747). Although these works have constructed strong metal-support interactions, there are great obstacles in the further modification and microenvironment regulation of single-atom active centers, resulting in low activity of the catalysts. Therefore, it is very important and significant to develop a catalyst with high catalytic activity and stability. SUMMARY
[0004] The purpose of the present application is to solve the problems of the prior art, and to provide a copper-based molecular sieve photocatalyst and a preparation method and application thereof. The technical solutions adopted are as follows:
[0005] In one aspect of the present application, a preparation method of a copper-based molecular sieve photocatalyst is provided, comprising the following steps:
[0006] S1: uniformly mix a copper nitrate solution with L-type molecular sieves, then react at a temperature of 60-90 DEG C for 6-24 hours, after the reaction, centrifuge, wash until neutral, dry, and obtain Cu-L-type molecular sieves;
[0007] S2: under N2 atmosphere, place the above Cu-L-type molecular sieves in N,N-dimethylformamide, then add thioacetamide, react at 115-130 DEG C for 1-2 hours, after the reaction, centrifuge, dry, after the drying, calcine at 200-300 DEG C for 2-4 hours, and finally obtain the copper-based molecular sieve photocatalyst.
[0008] The present application adopts the hydrothermal method to introduce Cu 2+ into the limited nanospace of L-type molecular sieves, and uses thioacetamide as a sulfur source to perform sulfur functionalization on the copper single-atom (Cu-SACs) active center, which can not only promote charge separation but also provide effective electron transfer; wherein the L-type molecular sieves selected in the present application are prepared by a specific preparation process, and the L-type molecular sieves have perfect morphology and uniform size, which not only have excellent chemical stability and thermal stability, but also have good optical properties. In addition, the catalyst prepared by the present application shows excellent catalytic performance in the reduction of carbon dioxide, without adding other sacrificial agents and photosensitizers, and compared with the traditional carbon dioxide gas-liquid photocatalytic reaction, this method has low cost, high yield and less waste liquid.
[0009] As a further preferred embodiment, the preparation process of the L-type molecular sieves is as follows:
[0010] Dissolve aluminum hydroxide, sodium hydroxide and potassium hydroxide in water to obtain an aluminum source solution; dissolve silicon powder and potassium hydroxide in water to obtain a silicon source solution; mix the aluminum source solution and the silicon source solution to obtain a synthesis sol, then ultrasonic aging at 25 DEG C for 30 minutes, hydrothermal crystallization at 175 DEG C for 2 hours, centrifugation to obtain crystals, washing until neutral, and drying to obtain L-type molecular sieves;
[0011] The molar ratio of the oxides of the components in the synthesis sol is n (SiO2): n (Al2O3): n (Na2O): n (K2O): n (H2O)=1:0.05:0.086:0.25:18.
[0012] The particle size of the L-type molecular sieves prepared by the above preparation method is 500 nm.
[0013] As a further preferred embodiment, the ratio of the amount of the copper nitrate solution to the L-type molecular sieve in step S1 is 10:1, and the reaction time is 6-12 hours.
[0014] As a further preferred embodiment, the ratio of the amount of the Cu-L type molecular sieve to the thioacetamide is 0.3 g:(1.0-2.0) g. More preferably, the ratio of the amount of the Cu-L type molecular sieve to the thioacetamide is 0.3 g:1.5 g.
[0015] As a further preferred embodiment, the concentration of the copper nitrate solution is 0.5 mol L -1 -2 mol L -1 .
[0016] As a further preferred embodiment, the drying is performed by vacuum drying, the drying temperature is 80℃, and the drying time is 12 hours.
[0017] Another aspect of the present application also provides a copper-based molecular sieve photocatalyst prepared by the above preparation method, which can be applied in catalyzing the reduction of CO2, specifically in the reduction of carbon dioxide in a carbon dioxide and water gas-liquid reaction.
[0018] The present application has the following advantages:
[0019] (1) The preparation method of the present application is simple and easy to operate, and has low cost. The copper ions are introduced into the L-type molecular sieve channel by the hydrothermal method, and the ion modification in the molecular sieve channel is realized in one step.
[0020] (2) The present application develops a new type of high-efficiency Cux-S@L photocatalyst based on the highly ordered structure of L-type molecular sieve. The high performance is attributed to the atomic-level dispersed active located near the photosensitive unit, the regulation of the coordination environment of the monatomic site, and the advantages of further promoting the charge transfer efficiency and reducing the proton activation barrier compared with the catalyst prepared by the traditional method.
[0021] (3) The catalyst prepared by the present application has the characteristics of multiple catalytic active sites, and has high catalytic activity and stability. It is a very promising catalyst. In the application of carbon dioxide photocatalytic gas-liquid reaction, no other sacrificial agent or photosensitizer is needed. According to the experimental data of the present embodiment, the catalyst prepared by the present application innovatively obtains formic acid in the photocatalytic reduction of carbon dioxide, and the yield is 69.7 μmol g -1 h -1 , which has a broad application prospect compared with the traditional reaction. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1The scanning electron microscope (SEM) images and the corresponding X-ray diffraction (XRD) images of the self-made molecular sieves in Example 1 and Comparative Examples 1 and 2 are shown.
[0023] Figure 2 The X-ray diffraction (XRD) images of the photocatalysts in Examples 1-3 are shown.
[0024] Figure 3 The scanning electron microscope (SEM) images of the photocatalysts in Examples 1-3 are shown.
[0025] Figure 4 The transmission electron microscope (TEM) and element distribution images of the photocatalyst in Example 1 are shown.
[0026] Figure 5 The ultraviolet-visible absorption spectrum images of the photocatalysts in Examples 1-3 are shown.
[0027] Figure 6 The X-ray photoelectron spectroscopy (XPS) images of the photocatalyst Cu 2p in Examples 1, 4-5 and Comparative Example 3 are shown.
[0028] Figure 7 The catalytic performance images of the photocatalysts in Examples 1-3 are shown. DETAILED DESCRIPTION
[0029] The concept, specific structure and generated technical effects of the present application will be described clearly and completely in combination with the embodiments and the drawings below, so as to fully understand the purpose, scheme and effect of the present application. 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.
[0030] Example 1
[0031] A preparation method of a copper-based molecular sieve photocatalyst, which specifically comprises the following steps:
[0032] Step 1: Dissolve aluminum hydroxide, sodium hydroxide and potassium hydroxide in deionized water, and at the same time, dissolve silicon powder and potassium hydroxide in deionized water, after the mixed solutions of the two are clarified, drop the silicon source into the aluminum source, and the ratio (molar ratio) of the oxides of each component is n (SiO2): n (Al2O3): n (Na2O): n (K2O): n(H2O) =1:0.05:0.086:0.25:18, ultrasonic aging for 30 min to obtain a synthesis sol. The mixed gel was placed in a blast oven, the crystallization temperature was 175 ℃, the crystallization time was 2 h, and the synthesis liquid was obviously separated into solid and liquid phases. The obtained lower solid phase was boiled with deionized water, washed with deionized water, centrifuged until the pH value was neutral, and dried at 100 ℃ for 12 h to obtain the self-made L-type molecular sieve;
[0033] Step 2: 12.1 g of Cu(NO3)2 . 3H2O was added to 50.0 mL of deionized water to form a copper nitrate solution; 1.0 g of the self-made L-type molecular sieve was added, and the mixture was uniformly mixed and then placed in a dynamic reaction kettle and reacted at 80 ℃ for 12 h, and then washed with deionized water, centrifuged until the pH value was 7, and dried at 80 ℃ for 12 h to obtain a Cu-L sample;
[0034] Step 3: 0.3 g of the Cu-L sample obtained above was added to 15.0 ml of DMF, and 1.5 g of thioacetamide was added. The mixture was heated at 120 ℃ in an oil bath under N2 atmosphere for 1 h, and then dried in a vacuum drying oven at 80 ℃ for 12 h, and then calcined at 200 ℃ in a tube furnace under N2 atmosphere for 2 h, to finally obtain a copper-based molecular sieve photocatalyst (Cu 0.70 -S 0.30 @L).
[0035] Example 2
[0036] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the example, except that the amount of Cu(NO3) 2.3 H2O in step 1 of Example 1 is changed to 6.0 g, and finally a copper-based molecular sieve photocatalyst (Cu 0.55 -S 0.45 @L).
[0037] Example 3
[0038] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the example, except that the amount of Cu(NO3) 2.3 H2O in step 1 of Example 1 is changed to 24.2 g, and finally a copper-based molecular sieve photocatalyst (Cu 0.85 -S 0.15 @L).
[0039] Example 4
[0040] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the embodiment, except that the amount of thioacetamide in step 2 of the embodiment 1 is changed to 1.0 g, and finally a copper-based molecular sieve photocatalyst (Cu 0.80 -S 0.20 @L).
[0041] Example 5
[0042] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the embodiment, except that the amount of thioacetamide in step 2 of the embodiment 1 is changed to 2.0 g, and finally a copper-based molecular sieve photocatalyst (Cu 0.65 -S 0.35 @L).
[0043] Comparative Example 1
[0044] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the embodiment, except that the ratio of the self-made L-type molecular sieve (L2) synthesis sol in step 1 of the embodiment 1 is changed to n (H2O) / n (SiO2)=12, and the results are shown in Figure 1 b. From the corresponding XRD pattern, it can be seen that the characteristic peaks are consistent with the standard L-type molecular sieve, indicating that it is a pure phase L-type crystal, and from the SEM pattern, it can be seen that the crystal morphology is "date kernel-like" and the particle size is about 300 nm. Finally, a copper-based molecular sieve photocatalyst is obtained, and the average yield of HCOOH is 3.7 μmol g -1 h -1 , which indicates that its catalytic performance is not high.
[0045] Comparative Example 2
[0046] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the embodiment, except that the ratio of the self-made L-type molecular sieve (L3) synthesis sol in step 1 of the embodiment 1 is changed to n (Na2O): n (K2O)=0.09:0.27, and the results are shown in Figure 1 c. From the corresponding XRD pattern, it can be seen that the characteristic peaks are consistent with the standard L-type molecular sieve, indicating that it is a pure phase L-type crystal, and from the SEM pattern, it can be seen that the crystal morphology is close to "spherical", and the particle size is about 50 nm. Finally, a copper-based molecular sieve photocatalyst is obtained, and the performance test of photocatalytic reduction of carbon dioxide shows no performance.
[0047] Comparative Example 3
[0048] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the examples, except that in Example 1, step 2 does not add thioacetamide, and finally obtains a copper-based molecular sieve photocatalyst (Cu 1.0 S 0.0 @L), which is tested for the performance of photocatalytic reduction of carbon dioxide, and has no performance.
[0049] Comparative Example 4
[0050] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the examples, except that in Example 1, step 3 adds sodium sulfide, and finally obtains a copper-based molecular sieve photocatalyst, which is tested for the performance of photocatalytic reduction of carbon dioxide, and has no performance.
[0051] Comparative Example 5
[0052] A preparation method of a copper-based molecular sieve photocatalyst, which has the same steps as the examples, except that in Example 1, step 3 adds thiourea, and finally obtains a copper-based molecular sieve photocatalyst, which is tested for the performance of photocatalytic reduction of carbon dioxide, and has no performance.
[0053] Example 6
[0054] The copper-based molecular sieve photocatalysts prepared in Examples 1-5 and Comparative Example 3 are detected by ICP, and the detection results are shown in Table 1 below.
[0055] Table 1 ICP-MS test of photocatalysts of Examples 1-5 and Comparative Example 3
[0056]
[0057] As can be seen from the above table, Cu and S are present in the photocatalysts prepared in the present application, but the content is not high, and the actual Cu and S loadings of the catalyst in Example 1 are analyzed by ICP as n(Cu) / n(S)=0.6; the actual Cu and S loadings of the catalyst in Example 2 are analyzed by ICP as n(Cu) / n(S)=1.2; the actual Cu and S loadings of the catalyst in Example 3 are analyzed by ICP as n(Cu) / n(S)=0.8; the actual Cu and S loadings of the catalyst in Example 4 are analyzed by ICP as n(Cu) / n(S)=0.7; and the actual Cu and S loadings of the catalyst in Example 5 are analyzed by ICP as n(Cu) / n(S)=0.6.
[0058] Meanwhile, with the increase of the initial amount of thioacetamide added (Examples 1, 4, and 5), the amount of sulfur introduced into the corresponding catalyst increased slightly, while the copper exchange capacity did not change much (~0.4 mol). However, the silica-to-alumina ratio of the L-type molecular sieve decreased from 2.7 to 2.5, possibly due to the removal of locally enriched silicon species outside the molecular sieve framework. When the initial amount of copper ions added increased (Examples 1, 2, and 3), the sulfur and copper loadings in the corresponding catalysts showed a trend of first decreasing and then increasing. The silica-to-alumina ratio of the L-type molecular sieve remained basically unchanged, only the Cu content increased. 0.70 S 0.30 Compared with the blank Cu-L sample, the L-type molecular sieve Si-A ratio decreased from 2.8 to 2.5 after the introduction of sulfur when both samples had the same initial copper loading. Therefore, sulfur functionalization reduces the Si-A ratio of the molecular sieve, while copper loading does not affect it.
[0059] Example 7
[0060] This embodiment analyzes the characterization data of the photocatalysts prepared in Examples 1-5, and the specific results are as follows:
[0061] Figure 2 The figures shown are X-ray diffraction patterns of the catalysts obtained in Examples 1-3 of this invention and the comparative catalysts; Figure 1 As can be seen from the data, the XRD peaks of all samples are consistent with the characteristic diffraction peaks of L-type molecular sieves, there are no other impurity phases, and the corresponding diffraction peaks have not changed significantly, indicating that the structure of L-type molecular sieves is stable after loading Cu and S.
[0062] Figure 3 The images shown are scanning electron microscope (SEM) images of the catalysts obtained in Examples 1-3 of this invention and the comparative catalysts. It can be seen from the images that the comparative blank molecular sieve... Figure 1 a. Apart from the spindle-shaped molecular sieve, no other obvious crystals were observed, and the particle size was approximately 500 nm.
[0063] Figure 4 The image shown is a transmission electron microscope image of the catalyst obtained in Example 1 of this invention. Nanosheet-like crystals, CuS, can also be seen in the image. (103) and Cu (111) The lattice fringes indicate that CuS and Cu SACs are anchored in the L-shaped molecular sieve. Elemental analysis shows that the catalyst contains seven elements: Al, Si, O, Na, K, Cu, and S.
[0064] Figure 5 The image shows the UV-Vis absorption spectra of the catalysts obtained in Examples 1-3 of this invention. (Cu) 0.55 -S 0.45 @L、Cu 0.79 -S 0.21 @L、Cu0.65 -S 0.35 @L The light absorption range of the two is wide, indicating that the Cu-L after being functionalized by sulfur has good light absorption.
[0065] Figure 6 The X-ray photoelectron spectrograms of Cu 2p of the catalysts obtained from Example 1, 4, 5 and Comparative Example 3 and the comparative catalyst are shown. As can be seen from the figure, the sample without sulfur, i.e. Cu 1.0 S 0.0 @L This is a typical Cu 2+ species signal, indicating that no redox reaction occurs in the ion modification process by the hydrothermal method, and after the sulfur-modified molecular sieve is functionalized, the binding energy is offset, indicating that the photocatalysis can have strong electronic interaction, generating a built-in electric field, which greatly promotes the separation of carriers. +
[0066] Example 8
[0067] The catalysts prepared in Examples 1-3 are applied to catalyze the gas-liquid reaction of carbon dioxide, and the specific process is as follows:
[0068] 50 mg of the photocatalyst is placed in a sealed glass reactor, and 500 mL of deionized water is added. A 250 W xenon lamp is used as the light source for the photocatalytic reaction. Before irradiation, the reactor is vacuum treated using a vacuum pump, and then high-purity CO2 gas is introduced into the water to reach the ambient pressure. The prepared photocatalyst is equilibrated in the CO2 atmosphere for several hours. The temperature of the reaction system is always maintained at 25 ℃ by circulating cooling water. During the irradiation process, 0.5 mL of liquid is extracted from the reaction bottle every hour, and subsequent analysis is performed using a liquid chromatograph (LC-20A, Shimadzu, Japan) equipped with a C18 column, a column temperature of 30 ℃, a mobile phase of 75% potassium dihydrogen phosphate solution (pH=2.9) / 25% acetonitrile, and a flow rate of 0.5 ml min -1 , a wavelength of 225 nm, and the results are shown in Figure 7 .
[0069] Figure 7 The photocatalytic CO2 reduction performance test graphs of the three catalysts are shown, and as can be seen from the figure, the Cu-L molecular sieve without sulfur has no catalytic performance, and the Cu 0.70 -S 0.30 @L has the optimal photocatalytic CO2 reduction performance into HCOOH (the average yield of HCOOH is 69.7 μmol g -1 h -1 , which is about 8.3 μmol g 0.55 -S 0.45 @L8.3 μmol g -1 h-1 ) and Cu 0.85 -S 0.15 @L (3.5 μmol g -1 h -1 ) by 8.4 and 19.9 times, respectively.
[0070] While the description of the application has been presented in terms of embodiments thereof that are presently preferred and specifically adapted for use in a variety of applications, it will be appreciated that those skilled in the art will readily apply the principles of the application to other applications and to other embodiments without departing from the scope of the application as defined by the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the description discloses the application, including what is presently believed to be the best way to implement the application. However, various modifications and changes can be made to the application as described without departing from the scope thereof, which is defined only by the appended claims. Moreover, the description is to be read in light of the accompanying drawings and the entire written specification.
Claims
1. A method for preparing a copper-based molecular sieve photocatalyst, characterized by, The method comprises the following steps: S1: mixing a copper nitrate solution with L-type molecular sieves, and then reacting at 60-90 DEG C for 6-24 hours; after the reaction, centrifuging, washing to neutral, and drying to obtain Cu-L-type molecular sieves; S2: placing the Cu-L-type molecular sieves in N,N-dimethylformamide under N2 atmosphere, adding thioacetamide, and then reacting at 115-130 DEG C for 1-2 hours; after the reaction, centrifuging, drying, and calcining at 200-300 DEG C for 2-4 hours, a copper-based molecular sieve photocatalyst is finally obtained; The molar compositional ratio of the components in the form of oxides in the synthesis sol of the L-type molecular sieve is n (SiO2) : n (Al2O3) : n (Na2O) : n (K2O) : n (H2O) = 1 : 0.05 : 0.086 : 0.25 :
18.
2. The production method according to claim 1, characterized by, The preparation process of the L-type molecular sieves is as follows: Aluminum hydroxide, sodium hydroxide and potassium hydroxide are dissolved in water to obtain an aluminum source solution; silicon powder and potassium hydroxide are dissolved in water to obtain a silicon source solution; the aluminum source solution and the silicon source solution are mixed to obtain a synthesis sol, which is then ultrasonically aged at 25 DEG C for 30 minutes, hydrothermally crystallized at 175 DEG C for 2 hours, centrifuged to obtain crystals, washed until neutral, and dried to obtain L-type molecular sieves.
3. The production method according to claim 2, characterized by, The particle size of the L-type molecular sieves is 500 nm.
4. The method of claim 1, wherein, In step S1, the amount ratio of the copper nitrate solution to the L-type molecular sieves is 10:1, and the reaction time is 6-12 hours.
5. The preparation method according to claim 1, characterized in that, The amount ratio of the Cu-L-type molecular sieves to thioacetamide is 0.3 g:(1.0-2.0) g.
6. The method of claim 1, wherein, The concentration of the copper nitrate solution was 0.5 mol L -1 2 mol L -1 .
7. The preparation method according to claim 1, characterized in that, The drying is performed by vacuum drying, the drying temperature is 80 DEG C, and the drying time is 12 hours.
8. A copper-based molecular sieve photocatalyst, characterized in that, Prepared by the preparation method of any one of claims 1-7.
9. The application of the copper-based molecular sieve photocatalyst of claim 8 in catalyzing CO2 reduction reaction.
10. Use according to claim 9, characterized in that, The copper-based molecular sieve photocatalyst is used in the gas-liquid reaction of carbon dioxide and water to reduce carbon dioxide to form formic acid.