Preparation method and application of copper-doped bismuth sulfide catalyst

Abstract

The application relates to a preparation method and application of a copper-doped bismuth sulfide catalyst, and belongs to the field of electrochemical catalysis. The preparation method comprises the following steps: in the first step, bismuth salt and copper salt are dissolved in a mixed solution of methanol and N,N-dimethylformamide to serve as precursor A, and 3-mercapto-1 propane sulfonic acid sodium (MPS) is dissolved in a mixed solution of methanol and N,N-dimethylformamide to serve as precursor B. In the second step, a high-pressure piston pump is used to pump the precursors A and B into a premixer, the precursors are preheated through a preheating pipeline, and then enter a micro-channel reactor and react. In the third step, the catalyst is collected, cleaned and dried. The catalyst has porous nano corrugations on the surface and a hollow structure in the inside, has a larger specific surface area and electrochemical active area compared to general catalysts, exposes more active sites, and improves the catalytic activity. The catalyst can be applied to electrocatalytic reduction of carbon dioxide to generate formic acid, the preparation operation is simple, the cost is low, the catalyst has industrial amplification feasibility, high practical value and high popularization value.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis, specifically relating to a method for preparing copper-doped bismuth sulfide catalysts, based on a microchannel reactor, and the application of the catalyst in carbon dioxide reduction. Background Technology

[0002] Developing novel catalytic materials with both high efficiency and stability, along with their supporting continuous preparation technologies, has become a core driving force for the advancement of electrocatalytic CO2 reduction reaction (CO2RR). Among the various reduction products of CO2RR, formic acid has attracted much attention due to its broad industrial application potential and significant economic value. Existing literature has confirmed that bismuth (Bi)-based materials can selectively generate formic acid during electrochemical CO2 reduction, while also possessing the outstanding advantages of abundant resources and environmental friendliness. However, the reaction kinetics of this type of catalyst in the CO2RR process are relatively slow, requiring a high overpotential to generate the target product, which limits further improvement in its catalytic activity and selectivity. Formic acid (HCOOH) is widely used as a basic chemical raw material in industries such as pesticides, leather, and rubber, and also plays an important role in renewable energy. It is more environmentally friendly, non-toxic, and more readily biodegradable than other acids. Electrocatalytic reduction of CO2 to HCOOH, while simultaneously realizing the resource utilization of CO2 and the clean and efficient conversion of electricity, is a very promising strategy for solving energy and environmental problems related to the continuous consumption of fossil fuels. Naturally abundant bismuth-based catalysts have attracted widespread attention in the field of electrocatalytic reduction of carbon dioxide to formate due to their low toxicity and low cost. Metal oxide nanocatalysts are also gaining increasing attention due to their abundant surface sites, high atom utilization efficiency, and enhanced catalytic performance for many reactions. These nanocatalysts can achieve reliable and efficient continuous electrocatalytic conversion of CO2 to formate.

[0003] In recent years, heteroatom doping, as a means to effectively control electronic structure, has shown promising application prospects in enhancing the catalytic activity of CO2 reduction. Studies have shown that sulfur (S) doping can not only optimize the electronic structure of bismuth but also enhance its... The adsorption stability of intermediates on the catalyst surface improves the selectivity of the target product. Furthermore, the binding of sulfur (S) to metal edge sites weakens the adsorption strength of hydrogen (H), effectively suppressing the hydrogen evolution side reaction. To further enhance performance, the introduction of other metal elements to construct bimetallic doping systems has also attracted widespread attention, particularly the doping of transition metals such as copper (Cu). The introduction of Cu not only modulates the electronic structure of the catalyst but also provides additional active sites, promoting CO2 activation and... Intermediate formation. The above studies indicate that the synergistic doping of S and Cu may produce significant synergistic enhancement effects in regulating electronic structure and reaction pathways. However, achieving uniform multi-element doping and controllable structural construction remains a challenge. Traditional synthesis methods based on batch reactors, such as hydrothermal methods, are easily limited by uneven mass transfer and thermodynamic conditions during multi-component co-doping, often leading to problems such as uneven doping distribution and poor batch repeatability. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying copper-doped bismuth sulfide catalysts. The copper-doped bismuth sulfide catalysts are prepared using microchannel reactor technology, and multi-copper-doped bismuth sulfide catalysts are used for the efficient electrocatalytic reduction of carbon dioxide to formic acid. Microfluidic synthesis technology, with its excellent mass transfer efficiency and precise residence time control, can achieve rapid and uniform nucleation of multiple components at the nanoscale, thereby significantly improving doping uniformity and material structural stability.

[0005] To achieve this objective, the technical solution adopted by the present invention is as follows: a method for preparing a copper-doped bismuth sulfide catalyst, comprising the following steps:

[0006] (1) Dissolve bismuth salt and copper salt in a solvent as precursor A; dissolve sodium 3-mercapto-1-propanesulfonate in a solvent as precursor B;

[0007] (2) The high-pressure plunger pump pumps precursors A and B into the premixer, and after preheating through the preheating pipe, they enter the microchannel reactor. The premixer is a Y-type mixer with a channel size of 1~5 mm. The preheating temperature is 80~130℃. The flow rate ratio of precursor A to precursor B is 1:1-1:3.

[0008] (3) The mixed solution is reacted in a microchannel reactor at a temperature of 80-130℃, a pressure of 1-4 MPa, and a time of 2-5 min to obtain a mixture of copper-doped bismuth sulfide solid powder.

[0009] (4) The above mixture is cooled in a tubular cooler and then collected, washed and dried to obtain a copper-doped bismuth sulfide catalyst.

[0010] In the precursor A, the molar ratio of bismuth salt to copper salt is 0.7:(0.1-0.25), and the concentration of bismuth salt is 5-7 mmol / L.

[0011] In the precursor B, the molar concentration of sodium 3-mercapto-1-propanesulfonate is 0.8-1.2 mmol / L. The molar ratio of the bismuth salt to the sodium 3-mercapto-1-propanesulfonate is 0.6-0.8:1.

[0012] Specifically:

[0013] (1) Bismuth salt and copper salt were dissolved in a mixed solution of methanol and N,N-dimethylformamide as precursor A; sodium 3-mercapto-1-propanesulfonate (MPS) was dissolved in a mixed solution of methanol and N,N-dimethylformamide as precursor B;

[0014] (2) The high-pressure plunger pump pumps precursors A and B into the premixer, and after preheating through the preheating pipe, they enter the microchannel reactor. The premixer is a Y-type mixer with a channel size of 1~5 mm. The preheating temperature is 80~130℃. The flow rate ratio of precursor A to precursor B is 1:1-1:3.

[0015] (3) The mixed solution is reacted in a microchannel reactor at a temperature of 80-130℃, a pressure of 1-4 MPa, and a time of 2-5 min to obtain a mixture of copper-doped bismuth sulfide solid powder.

[0016] (4) The above mixture is cooled in a tubular cooler and then collected, washed and dried to obtain copper-doped bismuth sulfide catalyst.

[0017] In the precursor A, the amount of bismuth salt is 0.7 mmol and the amount of copper salt is 0.1-0.25 mmol.

[0018] In precursor B, the amount of sodium 3-mercapto-1-propanesulfonate (MPS) is 1 mmol.

[0019] The bismuth salt is a trivalent bismuth salt, selected from bismuth nitrate pentahydrate, bismuth trichloride, bismuth sulfate, bismuth acetate, etc.

[0020] The copper salts mentioned are copper nitrate, copper nitrate trihydrate, copper sulfate, etc.

[0021] The electrode contains copper-doped bismuth sulfide prepared by any of the above methods.

[0022] A method for preparing a copper-doped bismuth sulfide electrode involves ultrasonically dispersing copper-doped bismuth sulfide in a mixture of Nafion and isopropanol, dropping the suspension onto hydrophilic carbon paper, and vacuum drying to obtain the copper-doped bismuth sulfide electrode.

[0023] The copper-doped bismuth sulfide is used in the electrochemical reduction of carbon dioxide.

[0024] A copper-doped bismuth sulfide electrode is used in the electrochemical reduction of carbon dioxide.

[0025] Furthermore, in step (1), the trivalent bismuth salt is bismuth nitrate pentahydrate, and the amount of substance is 0.7 mmol.

[0026] Furthermore, in step (1), the copper salt is copper nitrate trihydrate, and the amount of substance is 0.1-0.25 mmol.

[0027] Furthermore, in step (1), the volume of the methanol and N,N-dimethylformamide mixed solution is 50 ml each.

[0028] Furthermore, in step (1), the amount of sodium 3-mercapto-1-propanesulfonate (MPS) is 1 mmol.

[0029] Furthermore, in step (2), the flow rate ratio of precursor solutions A and B is 1:1, 1:2, and 1:3.

[0030] Furthermore, the premixer in step (2) is a Y-type mixer with a channel size of 1~5 mm;

[0031] The microreactor includes a CPMM separation and recombination reactor and a pipeline reactor. The CPMM reactor has a structure with a size of 50 to 500 micrometers and can cut the passing reaction liquid into a liquid film with a thickness of 50 to 500 micrometers and mix the reaction uniformly.

[0032] Further, in step (3), as a preferred technical solution of the present invention, the temperature of the microchannel reactor is 80℃~130℃, for example 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, etc.; the reaction temperature is one of the important factors affecting the morphology of the reaction products. The reaction pressure is 1~4MPa, for example 1.0MPa, 1.5MPa, 2.0MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, etc., preferably 1~2MPa.

[0033] Furthermore, in step (3), to ensure a more complete reaction and a low content of reaction impurities, the reaction time in this invention is 2-5 minutes, for example, 2 minutes, 3 minutes, 4 minutes, 5 minutes, etc. If the reaction time is too long, it will lead to an increase in the size of the synthesized catalyst and unevenness. If the reaction time is too short, it will not be possible to ensure that the raw materials react completely, resulting in waste of raw materials.

[0034] Furthermore, in step (4), the temperature of the vacuum drying oven is 60°C and the drying time is 12 hours.

[0035] Compared with existing technologies, the beneficial effects of this invention are as follows: Microfluidics, as a mature microfluidic manipulation technology, is not simply introduced into the bismuth-based catalyst synthesis system. This invention leverages the advantages of the reaction mechanism in traditional hydrothermal coordination synthesis, innovatively coupling millisecond-level mass transfer, continuous parameter control, and modular reaction design in microfluidics. This solves key problems in traditional batch synthesis, such as uneven nucleation of bismuth-based materials, poor doping dispersion, difficulty in precise control of crystal phase, and poor batch-to-batch reproducibility. While retaining classical synthetic chemistry, it achieves refined controllability of the bismuth-based composite catalyst structure and continuous upgrading of the preparation process, possessing both mechanism inheritance and process innovation value. Compared with general catalysts, it has a larger specific surface area and electrochemical active area, exposing more active sites and improving catalytic activity. During the catalytic process, the electrode maintains a high Faradaic efficiency in the electrocatalytic reduction of carbon dioxide to formic acid over a wide potential range.

[0036] The preparation method provided by this invention has a short reaction time, completing the reaction within 5 minutes, which significantly improves the reaction efficiency. This invention employs microfluidic technology, using a microchannel reactor to prepare the catalyst. By adjusting and optimizing various reaction parameters, the particle size of the product is controlled to avoid excessively large product particles clogging the channels. The preparation method is simple, easy to operate, and easy to scale up; simply increasing the number of microreactors is sufficient, making it suitable for industrial production.

[0037] The porous hollow nanosphere bismuth oxide catalyst prepared by morphology control in this invention exhibits excellent electrocatalytic carbon dioxide reduction performance. After electrolysis at -1.8V for 7 hours, the catalyst consistently maintains a Faradaic efficiency of over 90% in reducing carbon dioxide to formic acid. Attached Figure Description

[0038] Figure 1 Scanning electron microscope image of copper-doped bismuth sulfide catalyst in nanosheets.

[0039] Figure 2 Scanning electron microscope (SEM) images of the morphology of copper-doped bismuth sulfide catalysts obtained under different microchannel reaction conditions.

[0040] Figure 3 Scanning transmission electron microscopy image of copper-doped bismuth sulfide catalyst in nanosheets.

[0041] Figure 4 The image shows the X-ray diffraction pattern of the copper-doped bismuth sulfide catalyst in nanosheets.

[0042] Figure 5 X-ray photoelectron spectra of copper-doped bismuth sulfide catalysts on nanosheets.

[0043] Figure 6 Linear voltammetric curve of copper-doped bismuth sulfide catalyst in nanosheets.

[0044] Figure 7Faraday efficiency diagram of copper-doped bismuth sulfide catalyst in H-cell.

[0045] Figure 8 Potential electrolysis diagram and Faraday efficiency diagram of copper-doped bismuth sulfide catalyst in H-cell.

[0046] Figure 9 Long-term potentiostatic electrolysis diagram of copper-doped bismuth sulfide catalyst in H-cell.

[0047] Figure 10 CV curves and C-values ​​of copper-doped bismuth sulfide catalysts on nanosheets dl curve. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments. This embodiment is a method for preparing nanocatalysts based on a microchannel reactor and its application in electrocatalytic carbon dioxide reduction.

[0049] Example 1

[0050] This embodiment provides a bismuth sulfide catalyst (Bi - A method for preparing MPS, the method comprising the following steps:

[0051] (1) Dissolve 340 mg Bi(NO3)3·5H2O in a 50 mL DMF + 50 mL methanol mixture and sonicate until homogeneous to name solution A. Dissolve 178 mg sodium 3-mercapto-1 propanesulfonate (MPS) in a 50 mL DMF + 50 mL methanol mixture and sonicate until homogeneous to name solution B.

[0052] (2) A high-pressure plunger pump pumps precursors A and B into the premixer at a flow rate ratio of 1:1. After being preheated through a preheating pipe, they enter the microchannel reactor. The premixer is a Y-type mixer with a preheating temperature of 120℃.

[0053] (3) The mixed solution was reacted in a microchannel reactor to obtain a mixture of copper-doped bismuth sulfide solid powder; the reaction temperature was 120℃, the reaction pressure was 2MPa, and the reaction time was 3min;

[0054] (4) The mixture of copper-doped bismuth sulfide solid powder was cooled in a tube cooler and then collected. The catalyst was washed with deionized water and ethanol and then dried in a vacuum drying oven at 60°C for 12 hours.

[0055] (5) Weigh the copper-doped bismuth sulfide and ultrasonically disperse it in a mixture of Nafion and isopropanol. Drop the suspension onto... Copper-doped bismuth sulfide electrodes were prepared by vacuum drying on hydrophilic carbon paper.

[0056] Scanning electron microscope images of the copper-doped bismuth sulfide catalyst obtained in this embodiment are as follows: Figure 1 As shown, the materials are mostly in the shape of nanosheets.

[0057] The high-angle annular dark-field image of the copper-doped bismuth sulfide catalyst obtained in this embodiment is shown in the scanning transmission electron microscope image. Figure 3 As shown, the surface morphology of the material is a porous nanosphere shape, and the lattice fringes correspond to the X-ray diffraction pattern results.

[0058] The X-ray diffraction pattern of the copper-doped bismuth sulfide catalyst obtained in this embodiment is as follows: Figure 4 As shown, obvious diffraction peaks of bismuth oxide can be observed.

[0059] The X-ray photoelectron spectrum of the copper-doped bismuth sulfide catalyst obtained in this embodiment is as follows: Figure 5 As shown.

[0060] Examples 2-5:

[0061] The difference from Example 1 is that in this example, copper nitrate trihydrate was added to precursor solution A at mass levels of 24 mg (Example 2), 37 mg (Example 3), 48 mg (Example 4), and 60 mg (Example 5). The catalyst morphologies obtained in Examples 2-5 are as follows. Figure 2 As shown in the middle (ad).

[0062] Examples 6-8:

[0063] The difference from Example 1 is that the residence time of the reaction solution in this example is 2 min (Example 6), 4 min (Example 7), and 5 min (Example 8). The catalyst morphology obtained in Examples 6-8 is as follows. Figure 2 As shown in eg.

[0064] Examples 9-10:

[0065] The difference from Example 1 is that the reaction pressure in this example is 1 MPa (Example 9) and 3 MPa (Example 10). The catalyst morphology obtained in Examples 9-11 is as follows. Figure 2 As shown in the middle of the image.

[0066]

[0067] Example 11:

[0068] The electrocatalytic carbon dioxide reduction reaction was carried out in a three-electrode H-type electrolytic cell, with the cathode and anode separated by a proton exchange membrane. Two portions of the copper-doped bismuth sulfide catalyst prepared in Examples 1-5 were mixed with 200 μL of ethanol and 10 μL of Nafion solution (5 wt%), respectively, and ultrasonically mixed to form two uniform inks. The inks were then drop-coated onto the two portions of ethanol. The working electrode is formed on hydrophilic carbon paper, the reference electrode is a silver-silver chloride electrode, the counter electrode is a platinum sheet electrode, and the electrolyte is a CO2-saturated 0.1M potassium bicarbonate aqueous solution. Linear voltammetry tests are performed in the voltage range of -0.1V to -2V. Figure 6 Bi-MPS-Ar, Bi 0.7 Cu 0.1 -MPS-Ar, Bi 0.7 Cu 0.15 -MPS-Ar, Bi 0.7 Cu 0.2 -MPS-Ar, Bi 0.7 Cu 0.25 -MPS-Ar represent the catalysts prepared in Examples 1, 2, 3, 4, and 5, respectively. The results in the figure show that the copper-doped bismuth sulfide catalyst in Example 3 (Bi...) 0.7 Cu 0.15 Bi-MPS is more sensitive to the carbon dioxide reduction reaction than the undoped bismuth sulfide catalyst of Example 1 (Bi-MPS).

[0069] Example 12:

[0070] The electrocatalytic carbon dioxide reduction reaction was carried out in a three-electrode H-type electrolytic cell, with the cathode and anode separated by a proton exchange membrane. Two portions of the copper-doped bismuth sulfide catalyst prepared in Examples 1 and 3 were mixed with 200 μL of ethanol and 10 μL of Nafion solution (5 wt%), respectively, and ultrasonically mixed to form two uniform inks. The inks were then drop-coated onto the two portions of ethanol. The working electrode is formed on hydrophilic carbon paper, the reference electrode is a silver-silver chloride electrode, the counter electrode is a platinum sheet electrode, and the electrolyte is a CO2-saturated 0.1M potassium bicarbonate aqueous solution. The electrolytic reduction reaction is carried out under a constant voltage of -1.6V to -2.0V, with carbon dioxide gas continuously introduced during the reaction. Figure 7 (a) shows the time-current curve of the nanosheet catalyst (Bi-MPS) shown in Example 1 for the electrocatalytic reduction of carbon dioxide for 1 hour under a constant voltage of -1.6V to -2.0V; (b) shows the time-current curve of the nanosheet catalyst (Bi-MPS) shown in Example 3. 0.7 Cu 0.15 Time-current curves of electrocatalytic carbon dioxide reduction for 1 hour under a constant voltage of -1.6V to -2.0V (MPS). Figure 8(a) shows the Faradaic efficiency of the undoped copper bismuth sulfide catalyst of Example 1 in the electrocatalytic reduction of carbon dioxide for 1 hour under a constant voltage of -1.6V to -2.0V, and it reaches the highest formic acid production Faradaic efficiency of 91.42% at -1.8V. (b) shows the nanosheet catalyst (Bi) shown in Example 3. 0.7 Cu 0.15 The Faradaic efficiency of the electrocatalytic reduction of carbon dioxide for 1 hour under a constant voltage of -1.6V to -2.0V (MPS) was measured, and Bi... 0.7 Cu 0.15 -MPS achieves its highest formic acid production efficiency of 94.14% at -1.8 V.

[0071] Example 13:

[0072] The electrocatalytic carbon dioxide reduction reaction was carried out in a three-electrode H-type electrolytic cell, with the cathode and anode separated by a proton exchange membrane. 1 mg of the copper-doped bismuth sulfide catalyst prepared in Example 1, 200 μL of ethanol, and 10 μL of Nafion solution (5 wt%) were mixed and ultrasonically stirred to form a uniform ink. The ink was then drop-coated onto... The working electrode is formed on hydrophilic carbon paper, the reference electrode is a silver-silver chloride electrode, the counter electrode is a platinum sheet electrode, and the electrolyte is a CO2-saturated 0.1M potassium bicarbonate aqueous solution. The electrolytic reduction reaction is carried out under a constant voltage of -1.6V to -2.0V, with carbon dioxide gas continuously introduced during the reaction. Figure 9 The nanosheet catalyst shown is Bi 0.7 Cu 0.15 Current curves of electrocatalytic carbon dioxide reduction over a long period of time using -MPS at a constant voltage of -1.8V. Figure 10 Examples 1-5 show that the electrochemical double-layer capacitance of different catalysts in the non-Radida region was measured using cyclic voltammetry. It can be seen that the Bi in Example 3... 0.7 Cu 0.15 The Cdl of Bi-MPS was significantly higher than that of Bi-MPS in Example 1, indicating that Bi 0.7 Cu 0.15 -MPS catalysts have a larger catalytically active surface area and more CO2RR active sites.

[0073] Finally, it should be noted that the detailed description of the above embodiments and related drawings is only used to illustrate the technical solutions of the present invention and not to limit them. The present invention is not limited to the specific embodiments described above. Any modifications or equivalent substitutions made by those skilled in the art under the guidance of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a copper-doped bismuth sulfide catalyst, characterized in that, Includes the following steps: (1) Dissolve bismuth salt and copper salt in a solvent as precursor A; dissolve sodium 3-mercapto-1-propanesulfonate in a solvent as precursor B; (2) The high-pressure plunger pump pumps precursors A and B into the premixer, and after preheating through the preheating pipe, they enter the microchannel reactor. The premixer is a Y-type mixer with a channel size of 1~5 mm. The preheating temperature is 80~130℃. The flow rate ratio of precursor A to precursor B is 1:1-1:

3. (3) The mixed solution is reacted in a microchannel reactor at a temperature of 80~130℃, a pressure of 1~4MPa, and a time of 2~5min to obtain a mixture of copper-doped bismuth sulfide solid powder. (4) The above mixture is cooled in a tubular cooler and then collected, washed and dried to obtain a copper-doped bismuth sulfide catalyst.

2. The method for preparing a copper-doped bismuth sulfide catalyst according to claim 1, characterized in that: In the precursor A, the molar ratio of bismuth salt to copper salt is 0.7:(0.1-0.25), and the concentration of bismuth salt is 5-7 mmol / L.

3. The method for preparing a copper-doped bismuth sulfide catalyst according to claim 1, characterized in that: In the precursor B, the molar concentration of sodium 3-mercapto-1-propanesulfonate is 0.8-1.2 mmol, and the molar ratio of the bismuth salt to the sodium 3-mercapto-1-propanesulfonate is (0.6-0.8):

1.

4. The method for preparing a copper-doped bismuth sulfide catalyst according to claim 1, characterized in that: The bismuth salt is selected from one or more of bismuth nitrate pentahydrate, bismuth trichloride, bismuth sulfate, and bismuth acetate.

5. The method for preparing a copper-doped bismuth sulfide catalyst according to claim 1, characterized in that: The copper salts are copper nitrate, copper nitrate trihydrate, and copper sulfate.

6. A copper-doped bismuth sulfide electrode, characterized in that: The electrode contains a copper-doped bismuth sulfide catalyst prepared by any one of the preparation methods described in claims 1-5.

7. The method for preparing a copper-doped bismuth sulfide electrode according to claim 6, characterized in that: The copper-doped bismuth sulfide catalyst was ultrasonically dispersed in a mixture of Nafion and isopropanol. The suspension was then dropped onto hydrophilic carbon paper and dried under vacuum to obtain a copper-doped bismuth sulfide electrode.

8. The application of the copper-doped bismuth sulfide catalyst prepared by any one of the preparation methods according to claims 1-5, characterized in that: The copper-doped bismuth sulfide catalyst is used in the electrochemical reduction of carbon dioxide.

9. The copper-doped bismuth sulfide electrode according to claim 6 is used in the electrochemical reduction of carbon dioxide.

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