Bismuth-based Bi2S3-Bi2O3 heterojunction catalyst as well as preparation method, catalytic electrode and application thereof

Abstract

The invention provides a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst as well as a preparation method, a catalytic electrode and application thereof, and belongs to the technical field of electro-catalysis. The preparation method of the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst comprises the following steps: dissolving trimethyl ammonium bromide and thioacetamide in ultrapure water, and carrying out ultrasonic stirring to obtain a sulfonation reagent; the preparation method comprises the following steps: adding bismuth nitrate pentahydrate and concentrated nitric acid into deionized water to form a suspension, and homogenizing the suspension; and slowly dropwise adding the suspension liquid into the sulfonating reagent, carrying out stirring treatment, and centrifuging, cleaning and drying the precipitate to obtain the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst. According to the method, Bi (NO3) 3.5 H2O and TAA are used as reactants, ultrapure water is used as a solvent, raw materials are economical and easy to obtain, a solvothermal method is adopted as a synthesis strategy, the synthesis strategy is easy to operate, reaction conditions are mild and easy to control, the catalyst material stable in performance is obtained, and the method has wide application prospects in the field of ammonia generation through electrochemical reduction of nitrate.

Description

Technical Field

[0001] The present disclosure belongs to the field of electrocatalytic technology, and particularly relates to a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, a preparation method thereof, a catalytic electrode, and an application. Background Art

[0002] Ammonia (NH3) is a versatile key platform chemical, which is widely used in modern industry for the production of fertilizers, nutrients, pharmaceuticals, and future high-energy-density solar fuels, and is also a potential hydrogen carrier, playing a crucial role in sustainable energy systems. Global ammonia production heavily relies on the Haber-Bosch process, which uses an iron-based catalyst to catalyze the reaction of nitrogen and hydrogen at high temperature and high pressure. However, the above technology requires huge energy consumption and generates a greater environmental burden. Considering the increasing energy demand for ammonia in future industrial development, there is an urgent need to explore green and sustainable ammonia production strategies that can replace the traditional Haber-Bosch process. In this context, environmentally electrocatalytic ammonia synthesis driven by renewable energy is gradually becoming a promising alternative strategy. NO3 − is highly soluble in water, and the relevant dissociation energy of N-O is relatively low, which may result in high NH3 selectivity and low overpotential. The above advantages make the electrochemical nitrate reduction reaction an attractive route for ammonia electrosynthesis. In fact, nitrate is one of the most abundant nitrogen-containing pollutants in groundwater and can be used as a nitrogen source, which holds great promise for the production of a significant amount of NH3. From a thermodynamic perspective, the desired nitrate reduction is a proton-coupled 8-electron transfer process, and various by-products such as NO2 − , NO, and N2O can also be formed in the reduction reaction, resulting in extremely low NH3 activity and selectivity. Generally speaking, the performance of electrocatalytic NH3 synthesis is mainly determined by the electrocatalyst used. Therefore, the rational design of the catalyst is crucial for initiating and maintaining the reaction. Summary of the Invention

[0003] The present disclosure aims to solve at least one of the technical problems existing in the prior art, and provides a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, a preparation method thereof, a catalytic electrode, and an application.

[0004] In one aspect of the present disclosure, a preparation method of a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst is provided, and the preparation method includes: Dissolving trimethylammonium bromide and thioacetamide in ultrapure water, and performing ultrasonic stirring to obtain a sulfonating reagent; Adding bismuth nitrate pentahydrate and concentrated nitric acid to deionized water to form a suspension, and homogenizing the suspension; The suspension is slowly added drop by drop into the sulfonation reagent, stirred, and the precipitate is centrifuged, washed, and dried to obtain a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst.

[0005] Optionally, the content ratio of trimethylammonium bromide, thioacetamide, and ultrapure water is (0.02 - 0.03):(0.01 - 0.02):(10 - 13) g:g:mL.

[0006] Optionally, the content ratio of bismuth nitrate pentahydrate, concentrated nitric acid, and deionized water is (0.2 - 0.3):(0.1 - 0.3):(4 - 7) g:mL:mL.

[0007] Optionally, trimethylammonium bromide and thioacetamide are dissolved in ultrapure water, and the ultrasonic stirring time is 10 - 30 minutes.

[0008] Optionally, the suspension is slowly added drop by drop into the sulfonation reagent, and the stirring time is 3 - 4 hours; the drying temperature is 50 - 70 °C.

[0009] On the other hand, the present disclosure provides a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, which is prepared by the preparation method described above.

[0010] On the other hand, the present disclosure provides a catalytic electrode, which includes: carbon cloth and ink loaded on the carbon cloth; wherein, the ink includes a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, Nafion solution, isopropanol, and ultrapure water.

[0011] Optionally, the content of the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst is 1 - 3 parts by mass; the content of the Nafion solution is 20 - 40 parts by volume; the content of isopropanol is 450 - 500 parts by volume; the content of ultrapure water is 450 - 550 parts by volume.

[0012] On the other hand, the present disclosure provides an application of the catalytic electrode, and the catalytic electrode described above is used in electrocatalytic nitrate reduction.

[0013] Optionally, the catalytic electrode is used as the working electrode, a carbon rod electrode is used as the counter electrode, an Ag / AgCl electrode is used as the reference electrode, the cathode electrolyte is a mixed solution formed by KNO3 and KHCO3, the anode electrolyte is a KHCO3 solution, the reaction time at a single potential is 1 h, and the cathode electrolyte product is collected.

[0014] The present disclosure provides a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, a preparation method thereof, a catalytic electrode, and an application. The preparation method includes: dissolving trimethylammonium bromide and thioacetamide in ultrapure water, and performing ultrasonic stirring to obtain a sulfonating reagent; adding bismuth nitrate pentahydrate and concentrated nitric acid to deionized water to form a suspension, and homogenizing the suspension; slowly dropping the suspension into the sulfonating reagent drop by drop, performing stirring treatment, and centrifuging, washing, and drying the precipitate to obtain a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst. The present disclosure uses Bi(NO3)3·5H2O and TAA as reactants and ultrapure water as a solvent. The raw materials are economically available and easy to obtain. The solvothermal method is adopted as the synthesis strategy. The synthesis strategy is simple to operate, and the reaction conditions are mild and easy to control, obtaining a catalyst material with stable performance. The powder of this material is formulated with other components into an ink, which is drop-coated on the surface of carbon cloth and air-dried naturally to make a catalytic electrode. The catalytic electrode achieves a high ammonia production rate and Faraday efficiency at -0.4V vs. RHE, effectively inhibiting the side reaction of nitrate reduction, and has broad application prospects in the field of electrochemical reduction of nitrate to ammonia. Description of the Drawings

[0015] Figure 1 is a flowchart of the preparation method of the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst according to the specific embodiment of the present disclosure; Figure 2 is a schematic diagram of the synthesis principle of the Bi2S3-Bi2O3 heterojunction catalyst in Example 1 of the present disclosure; Figure 3 is an SEM image of the Bi2S3-Bi2O3 heterojunction catalyst powder prepared in Example 1 of the present disclosure; Figure 4 is an XRD pattern of the Bi2S3-Bi2O3 heterojunction catalyst powder prepared in Example 1 of the present disclosure; Figure 5 is an LSV curve of the catalytic electrode of the carbon cloth-supported bismuth-based Bi2S3-Bi2O3 heterojunction catalyst in Ar gas and nitrate in Example 1 of the present disclosure; Figure 6 is a standard curve for detecting ammonia concentration by the indophenol blue method in Example 1 of the present disclosure; Figure 7 is the ammonia production rate and Faraday efficiency of the catalytic electrode of the carbon cloth-supported bismuth-based Bi2S3-Bi2O3 heterojunction catalyst in Example 1 of the present disclosure; Figure 8 is a test result graph of the catalytic stability of the catalytic electrode of the carbon cloth-supported bismuth-based Bi2S3-Bi2O3 heterojunction catalyst in Example 1 of the present disclosure. Specific Embodiments

[0016] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure, which are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0017] As Figure 1 shown, in one aspect of the present disclosure, a preparation method S100 of a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst is provided, which specifically includes the following steps S110 to S130: S110: Dissolve trimethylammonium bromide and thioacetamide in ultrapure water, and perform ultrasonic stirring to obtain a sulfonating reagent.

[0018] Specifically, weigh trimethylammonium bromide (CTAB) and thioacetamide (TAA), dissolve them in ultrapure water, and prepare a sulfonating reagent by ultrasonic wave and stirring for 10 - 30 minutes. For example, stir for 10 minutes, 20 minutes, 30 minutes, etc.

[0019] In some preferred embodiments, the content ratio of trimethylammonium bromide, the thioacetamide, and the ultrapure water is (0.02 - 0.03):(0.01 - 0.02):(10 - 13) g:g:mL.

[0020] As a further preferred scheme, the content ratio of trimethylammonium bromide, the thioacetamide, and the ultrapure water is 0.025:0.015:12 g:g:mL.

[0021] As an even further preferred scheme, the content of trimethylammonium bromide can be preferably 0.125 g, the content of thioacetamide can be preferably 0.075 g, the content of ultrapure water can be preferably 60 mL, etc. Of course, in other preferred embodiments, the above components can also be preferably other contents, and no specific limitation is made thereto.

[0022] In this embodiment, thioacetamide is used as a sulfiding agent, while concentrated nitric acid can be used as a strong oxidant, which can oxidize part of Bi2S3 to Bi2O3, thereby forming a Bi2S3-Bi2O3 heterojunction. At the same time, concentrated nitric acid can also provide a strong acidic environment, promote the dissolution of reactants and the release of ions, and contribute to the formation of the heterojunction.

[0023] S120: Add bismuth nitrate pentahydrate and concentrated nitric acid to deionized water to form a white suspension, and homogenize the white suspension.

[0024] In some preferred embodiments, the content ratio of bismuth nitrate pentahydrate, the concentrated nitric acid, and the deionized water is (0.2 - 0.3):(0.1 - 0.3):(4 - 7) g:mL:mL.

[0025] As a further preferred embodiment, the content ratio of bismuth nitrate pentahydrate, the concentrated nitric acid, and the deionized water is 0.243:0.125:5 g:mL:mL.

[0026] As an even further preferred embodiment, the content of bismuth nitrate pentahydrate can be preferably 0.243 g, the content of the concentrated nitric acid can be preferably 0.125 mL, the content of the deionized water can be preferably 5 mL, etc. Of course, in other preferred embodiments, the above components can also be preferably other contents, which are not specifically limited herein.

[0027] S130. Slowly and dropwise add the suspension into the sulfonation reagent, stir, centrifuge the precipitate, wash it several times alternately with ultrapure water and ethanol, collect it under vacuum and dry it overnight to obtain the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst. In some preferred embodiments, the stirring time is 3 - 4 hours, for example, 3 hours, 3.5 hours, 4 hours, etc. The drying temperature is 50 - 70 °C, for example, 50 °C, 60 °C, 70 °C, etc.

[0028] This embodiment uses Bi(NO3)3·5H2O and TAA as reactants, uses ultrapure water as a solvent, and uses the solvothermal method as the synthesis strategy. The synthesis strategy is simple to operate, the reaction conditions are mild and easy to control, and the raw materials are economically available.

[0029] On the other hand, the present disclosure provides a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, which is prepared by the preparation method described above.

[0030] On the other hand, the present disclosure provides a catalytic electrode, which includes: a carbon cloth and an ink loaded on the carbon cloth; wherein, the ink includes the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst described above, Nafion solution, isopropanol, and ultrapure water. That is to say, the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, Nafion solution, isopropanol, and ultrapure water are mixed and formulated to form an ink, and the ink is dropped onto the carbon cloth using a pipette and air-dried naturally to obtain a carbon cloth-supported bismuth-based Bi2S3-Bi2O3 heterojunction catalytic electrode.

[0031] In some preferred embodiments, the content of the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst is 1 - 3 parts by mass, for example, 1 part by mass, 2 parts by mass, 3 parts by mass, etc.

[0032] In some other preferred embodiments, the content of the Nafion solution is 20 - 40 parts by volume, for example, 20 parts by volume, 30 parts by volume, 40 parts by volume, etc.

[0033] In some other preferred embodiments, the content of isopropanol is 450 - 500 parts by volume, for example, 450 parts by volume, 470 parts by volume, 500 parts by volume, etc.

[0034] In some other preferred embodiments, the content of ultrapure water is 450 - 550 parts by volume, for example, 450 parts by volume, 470 parts by volume, 500 parts by volume, 550 parts by volume, etc.

[0035] It should be noted that the units of parts by mass and parts by volume described in this embodiment can be adjusted according to actual needs. For example, when 1 part by mass represents 1 milligram, 1 part by volume can represent 1 microliter; when 1 part by mass represents 1 gram, 1 part by volume can represent 1 milliliter.

[0036] Furthermore, the carbon cloth in this embodiment can be a pretreated carbon cloth. For example, the carbon cloth is cut into a rectangle with a size of 1 cm × 2 cm, soaked successively in acetone, absolute ethanol, and concentrated sulfuric acid, ultrasonicated for 30 minutes each time during soaking, and repeatedly washed with ultrapure water. Then the carbon cloth is placed in a vacuum drying oven for drying to obtain the pretreated carbon cloth.

[0037] On the other hand, the present disclosure proposes an application of a catalytic electrode, applying the catalytic electrode described above to electrocatalytic nitrate reduction.

[0038] Specifically, the carbon cloth supported bismuth - based Bi2S3 - Bi2O3 heterojunction catalytic electrode is used as the working electrode, which is the cathode, the carbon rod electrode is used as the counter electrode, which is the anode, and the reference electrode uses an Ag / AgCl reference electrode. The cathode electrolyte is 60 mL of a 0.05 - 0.1 M KNO3 and 0.1 M KHCO3 solution, the anode electrolyte is 60 mL of a 0.1 M KHCO3 solution, the reaction time at a single potential is 1 h, and the cathode electrolyte products are collected.

[0039] The catalytic electrode obtained in the present disclosure is used for electrocatalytic ammonia production. The catalyst has excellent electrocatalytic activity and selectivity. After continuous electrolysis for 10 h using chronoamperometry, the current density does not change significantly, showing good catalytic stability and effectively improving the ammonia production rate and Faraday efficiency.

[0040] Next, the bismuth - based Bi2S3 - Bi2O3 heterojunction catalyst, catalytic electrode and their applications will be further illustrated with specific examples: Example 1 The preparation method of the bismuth - based Bi2S3 - Bi2O3 heterojunction catalyst in this example includes the following steps: S1. 0.125 g of hexadecyltrimethylammonium bromide (CTAB) and 0.075 g of thioacetamide (TAA) were added to 60 mL of deionized water, and a sulfonation reagent was prepared by ultrasonic treatment and stirring for 20 minutes. S2. 0.243 g of Bi(NO3)3·5H2O and 0.125 mL of aqueous HNO3 (14 M) were added to 5 mL of deionized water to form a white suspension, and the suspension was homogenized by ultrasonic treatment and stirring. S3. The white suspension was slowly added dropwise to the sulfonation reagent, and the entire solution was stirred at room temperature for 3.5 hours. The resulting precipitate was centrifuged and washed several times alternately with ultrapure water and ethanol. The product was collected and dried overnight under vacuum at 60 °C to obtain a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst.

[0041] As Figure 2 shown, in Example 1 under the above conditions, a Bi2S3-Bi2O3 heterojunction catalyst was generated, and its appearance and morphology were as Figure 3 shown, and the XRD pattern was as Figure 4 shown. By comparison, it can be seen that the substance synthesized in Example 1 was Bi2S3-Bi2O3.

[0042] Further, 2 mg of the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst powder, 30 μL of Nafion solution, 470 μL of isopropanol, and 500 μL of ultrapure water were added, and the above materials were mixed to form an ink. The carbon cloth was cut into a rectangle with a size of 1 cm × 2 cm, soaked in acetone, absolute ethanol, and concentrated sulfuric acid in sequence, ultrasonically treated for 30 minutes each time, and repeatedly washed with ultrapure water, and then the carbon cloth was placed in a vacuum drying oven for drying. The ink was coated on the treated carbon cloth to form a bismuth-based Bi2S3-Bi2O3 heterojunction catalytic electrode, and this catalytic electrode was used as the working electrode, as the cathode, the anode was a carbon rod electrode, and the reference electrode used an Ag / AgCl reference electrode. All potentials were converted to a reversible hydrogen electrode (RHE). The cathode electrolyte was 60 mL of a 50 mM KNO3 and 0.1 M KHCO3 solution, and the anode electrolyte was 60 mL of a 0.1 M KHCO3 solution. The reaction time at a single potential was 1 h, and the cathode electrolyte product was collected. As Figure 5 shown, the LSV curve was used to test and compare the current density of the heterojunction catalyst material in the presence and absence of nitrate. Compared with the KNO3-free electrolyte, the Bi2S3-Bi2O3 heterostructure showed a significantly enhanced current density in the KNO3 electrolyte.

[0043] As Figure 6As shown, chronoamperometry tests were further carried out to quantitatively evaluate the performance of Bi2S3-Bi2O3 in electrocatalytic ammonia production at different working potentials. The goodness of fit of this curve R 2 = 0.9998, indicating its high reliability and the ability to accurately calculate the ammonium ion concentration based on absorbance.

[0044] As Figure 7 shown, the ammonia production rate is the highest at -0.4 V, which is 89.83 mg / g / h. The FE of NH3 shows a volcano trend and reaches a peak at -0.4 V, which is ~94%, and it has good stability.

[0045] As Figure 8 shown, at the potential of -0.4 V, the current density remains basically stable with the change of time, without an obvious upward or downward trend, indicating that the electrode process reaches a steady state at this potential. That is, after continuous electrolysis for 10 h using the chronoamperometry method, the current density does not change significantly, and the catalyst has good stability.

[0046] The present disclosure provides a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, a catalytic electrode and an application, which have the following beneficial effects compared with the prior art: First, the present disclosure uses Bi(NO3)3·5H2O and TAA as reactants, ultrapure water as a solvent, adopts a solvothermal method as the synthesis strategy, uses carbon cloth as a carrier, and controls the reaction temperature at 100°C. The raw materials are economical and easy to obtain, the synthesis strategy is simple to operate, and the reaction conditions are mild and easy to control; Second, when the catalytic electrode obtained in the present disclosure is used for electrocatalytic ammonia production, it has a high production rate and Faraday efficiency; Third, the synthesized catalytic electrode of the present disclosure has good catalytic stability. After continuous electrolysis for 10 h using the chronoamperometry method, the current density does not change significantly. The results of the present invention have good prospects in replacing the traditional ammonia synthesis industry and the field of clean and efficient electro-synthesis of ammonia.

[0047] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present disclosure. However, the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the present disclosure.

Claims

1. A preparation method of a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, characterized in that, The preparation method includes the following steps: Dissolve trimethylammonium bromide and thioacetamide in ultrapure water, and perform ultrasonic stirring to obtain a sulfonating reagent; Add bismuth nitrate pentahydrate and concentrated nitric acid to deionized water to form a suspension, and homogenize the suspension; Slowly and dropwise add the suspension into the sulfonating reagent, perform stirring treatment, and centrifuge, wash, and dry the precipitate to obtain a bismuth-based Bi2S3-Bi2O3 heterojunction catalyst.

2. The preparation method according to claim 1, characterized in that, The content ratio of the trimethylammonium bromide, the thioacetamide, and the ultrapure water is (0.02 - 0.03):(0.01 - 0.02):(10 - 13) g:g:mL.

3. The preparation method according to claim 1, wherein The content ratio of the bismuth nitrate pentahydrate, the concentrated nitric acid, and the deionized water is (0.2 - 0.3):(0.1 - 0.3):(4 - 7) g:mL:mL.

4. The preparation method according to claim 1, wherein Dissolve trimethylammonium bromide and thioacetamide in ultrapure water, and the time for ultrasonic stirring is 10 - 30 minutes.

5. The preparation method according to claim 1, characterized in that, Slowly and dropwise add the suspension into the sulfonating reagent, the time for stirring treatment is 3 - 4 hours; the drying temperature is 50 - 70 °C.

6. A bismuth-based Bi2S3-Bi2O3 heterojunction catalyst, which is prepared by the preparation method according to any one of claims 1 to 5.

7. A catalytic electrode, characterized in that, The catalytic electrode includes: carbon cloth and the ink loaded on the carbon cloth; wherein, The ink includes the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst according to claim 6, Nafion solution, isopropanol, and ultrapure water.

8. The catalytic electrode according to claim 7, characterized in that, The content of the bismuth-based Bi2S3-Bi2O3 heterojunction catalyst is 1 - 3 mass parts; The content of the Nafion solution is 20 - 40 volume parts; The content of the isopropanol is 450 - 500 volume parts; The content of the ultrapure water is 450 - 550 volume parts.

9. An application of a catalytic electrode, characterized in that, Apply the catalytic electrode according to any one of claims 7 to 8 to electrocatalytic nitrate reduction.

10. The application according to claim 9, wherein Use the catalytic electrode as the working electrode, a carbon rod electrode as the counter electrode, an Ag / AgCl electrode as the reference electrode, the cathode electrolyte is a mixed solution formed by KNO3 and KHCO3, the anode electrolyte is a KHCO3 solution, the reaction time is 1 h at a single potential, and collect the cathode electrolyte product.

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