A bismuth-based metal organic nanosheet material, a preparation method and application thereof

Abstract

The application discloses a bismuth-based metal organic nanosheet material and a preparation method and application thereof, relates to the field of inorganic synthesis and the field of energy electrocatalysis technology. The preparation method is to use bismuth salt as a metal source, use amino succinic acid as an organic ligand, and prepare the bismuth-based metal organic nanosheet (Bi-MON) material by using a hydrothermal method. The Bi-MON material synthesized by the application presents an ultrathin nanosheet morphology, and the thickness is only 3 nm. Moreover, the preparation method is simple, does not need to add any surfactant or regulator, and does not use any organic solvent in the whole synthesis and post-processing process, so that green synthesis in the whole process is realized, the condition is mild, and the method is suitable for mass synthesis. Finally, the Bi-MON material synthesized by the application exhibits excellent electrocatalytic carbon dioxide reduction performance, and the faradic efficiency of formate generated under an industrial current density of 0.4 A·cm 2 -2 can reach 97.1%, and the Bi-MON material has a potential application prospect.

Description

Technical Field

[0001] This invention relates to the fields of inorganic synthesis and energy electrocatalysis, specifically to a bismuth-based organometallic nanosheet material, its preparation method, and its applications. Background Technology

[0002] Renewable electricity-driven electrocatalytic carbon dioxide reduction (CO2RR) offers a promising strategic pathway. However, its key technical challenges lie not only in the slow reaction kinetics due to the thermodynamic stability of the CO2 molecule, but also in the low selectivity resulting from its complex electron and proton transfer processes. Therefore, developing efficient electrocatalysts is crucial for improving the activity, selectivity, and stability of CO2RR. Formate is one of the most techno-economically advantageous basic chemicals among various reduction products. Researchers have devoted considerable effort to developing efficient electrocatalysts to achieve the efficient conversion of carbon dioxide to formate. Among these, bismuth-based materials have become important candidates due to their ability to suppress competing proton reduction. Although the performance of bismuth-based materials has been improved to some extent through morphology modulation, defect engineering, and / or elemental doping, their catalytic activity and selectivity still need to be enhanced. Developing new pathways to improve the performance of bismuth-based materials in electrocatalyzing the conversion of CO2 to formate remains a formidable challenge.

[0003] In recent years, the functionalization of organic molecules has been considered an effective strategy to enhance the electrocatalytic CO2 reduction to formate production by regulating the electronic structure / coordination environment of metal sites and their adsorption behavior on reaction intermediates. Metal-organic frameworks or coordination polymers are organic-inorganic hybrid materials assembled from metal ions and organic ligands, possessing high specific surface areas and customizable structures, giving them a natural advantage in integrating organic molecules to modify electrocatalytic performance. Among these, ultrathin metal-organic nanosheets (MONs) exhibit highly exposed catalytic active sites and superior conductivity, making them promising electrocatalysts; however, their controllable synthesis presents significant challenges. Therefore, developing a controllable synthesis strategy for bismuth-based metal-organic nanosheets (Bi-MONs) to achieve highly efficient electrocatalytic CO2 reduction to formate production has significant application value. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a bismuth-based metal-organic nanosheet material, its preparation method and application, so as to solve the problem of controllable synthesis of ultrathin metal-organic nanosheets and the technical bottlenecks of insufficient activity and low formate selectivity of bismuth-based materials in electrocatalytic CO2RR.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing bismuth-based metal-organic nanosheet materials, comprising the following steps: Bismuth-based organometallic nanosheets were prepared by a one-step hydrothermal method using aminosuccinic acid and bismuth salt as raw materials.

[0006] In a preferred embodiment of the present invention, the preparation method includes the following specific steps: S1. Dissolve aminosuccinic acid in water to prepare a ligand solution; S2. Add the bismuth salt to the ligand solution and mix thoroughly to prepare a mixed solution; S3. The mixed solution is reacted under heating conditions. After the reaction is completed, the product is collected, washed, and dried to obtain bismuth-based organometallic nanosheet material.

[0007] This invention uses aminosuccinic acid as a ligand to prepare an ultrathin bismuth-based metal-organic nanosheet material. Compared with the prior art which uses other amino acids as ligands, the aminosuccinic acid in this invention has a strong coordination ability and is more likely to form a stable coordination structure with bismuth ions. This is beneficial for the controllable growth of two-dimensional nanosheets and the regulation of the thickness of ultrathin bismuth-based metal-organic nanosheets, thereby helping to obtain an ultrathin bismuth-based metal-organic nanosheet structure with a thickness of only about 3 nm.

[0008] In a preferred embodiment of the present invention, in step S1, the concentration of the ligand solution is 0.1 mol / L to 1 mol / L.

[0009] In a preferred embodiment of the present invention, in step S2, the bismuth salt includes bismuth nitrate, chloride, sulfate, acetate, and hydrate of the salt.

[0010] In a preferred embodiment of the present invention, the molar ratio of bismuth atoms to aminosuccinic acid in the bismuth salt is 1:1 to 1:10.

[0011] In a preferred embodiment of the present invention, in step S3, the reaction temperature is 120°C to 160°C, and the reaction time is 8 h to 24 h.

[0012] Specifically, this invention provides a method for preparing bismuth-based organometallic nanosheet materials, comprising the following steps: (1) Dissolve the aminosuccinic acid ligand in deionized water; (2) Add the bismuth metal salt to the ligand solution obtained in step (1) above and stir until homogeneous; (3) Transfer the mixed solution obtained in step (2) above to a stainless steel reactor with a polytetrafluoroethylene liner, and react it in a constant temperature oven at 120℃~160℃ for 8 h~24 h. After cooling, filter, wash with deionized water, and dry to obtain the product.

[0013] Secondly, the present invention provides a bismuth-based metal-organic nanosheet material, which is obtained by the preparation method described above.

[0014] In a preferred embodiment of the present invention, the bismuth-based metal-organic nanosheet material exhibits an ultrathin nanosheet morphology with a thickness of 1~4 nm.

[0015] Thirdly, the present invention provides the application of the bismuth-based organometallic nanosheet material in the electrocatalytic reduction of carbon dioxide to prepare formate.

[0016] In a preferred embodiment of the present invention, the method of application includes: fabricating the bismuth-based metal-organic nanosheet material into a working electrode, using a three-electrode system, with KHCO3 solution as the electrolyte, and introducing CO2 gas into the cathode chamber to prepare formate; The method for preparing the working electrode includes: mixing the bismuth-based metal-organic nanosheet material with isopropanol and Nafion solution to obtain a mixed solution; ultrasonically dispersing the mixed solution to prepare a catalyst ink; uniformly coating the catalyst ink onto a glassy carbon electrode and drying it to form a uniform thin film to prepare the working electrode.

[0017] In a preferred embodiment of the present invention, the loading amount of bismuth-based metal-organic nanosheets on the glassy carbon electrode is 0.5~1 mg / cm³. 2 , Furthermore, electrochemical tests were conducted in an H-type electrolytic cell or a flow cell, employing a typical three-electrode system. The working electrode was a bismuth-based metal-organic nanosheet-loaded material, the reference electrode was an Ag / AgCl electrode, and the counter electrode was a platinum sheet. High-purity N2 or high-purity CO2 gas was continuously introduced into the cathode chamber to obtain N2- or CO2-saturated electrolyte solutions, which were then used to test the electrocatalytic performance.

[0018] This invention has at least one of the following beneficial effects: (1) This invention develops a one-step hydrothermal method for the direct preparation of bismuth-based organometallic nanosheets. The solvent used in this method is water, without the need for any surfactants or modifiers. Furthermore, no organic solvents are used in the entire synthesis and post-processing, achieving a green synthesis throughout the entire process. This method also has the advantages of mild and controllable reaction conditions, simple process flow, and high reproducibility.

[0019] (2) The bismuth-based metal-organic nanosheets prepared by the present invention have a thickness of only 3.1 nm, which can expose abundant active sites and is beneficial to improving electronic conductivity.

[0020] (3) The bismuth-based organometallic nanosheets prepared in this invention exhibit good electrocatalytic CO2RR activity and selectivity at 0.4 A·cm 2 The Faraday efficiency for generating formate at industrial-grade current densities can reach 97.1%, showing potential for future applications. Attached Figure Description

[0021] Figure 1 This is the X-ray powder diffraction pattern of Bi-MON in Example 1 of the present invention.

[0022] Figure 2 This is a scanning electron microscope image of Bi-MON in Embodiment 1 of the present invention.

[0023] Figure 3 This is a transmission electron microscope image of Bi-MON in Embodiment 1 of the present invention.

[0024] Figure 4 This is an atomic force microscope image of Bi-MON in Embodiment 1 of the present invention.

[0025] Figure 5 This is a linear sweep voltammetry curve of CO2RR for Bi-MON in Embodiment 2 of the present invention.

[0026] Figure 6 This is a Faraday efficiency diagram of the electrolysis of formate by Bi-MON at different potentials in Example 3 of the present invention.

[0027] Figure 7 This is a graph showing the electrocatalytic CO2RR stability test of Bi-MON in Example 3 of the present invention.

[0028] Figure 8 This is a linear sweep voltammetry curve of CO2RR for Bi-MON in Example 4 of the present invention.

[0029] Figure 9 This is a Faraday efficiency diagram of the electrolysis of formate by Bi-MON at different current densities in Example 4 of the present invention. Detailed Implementation

[0030] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] Example 1: Preparation of bismuth-based organometallic nanosheets (Bi-MON) materials This embodiment provides a method for preparing bismuth-based organometallic nanosheets (Bi-MON), including the following steps: Aminosuccinic acid (6 mmol) was poured into a beaker and dissolved in 20 mL of deionized water to obtain a ligand solution. Bismuth nitrate (2 mmol) was added to the ligand solution and stirred until homogeneous. The resulting liquid was then transferred to a 50 mL polytetrafluoroethylene-lined reactor, fitted with a stainless steel sleeve, and placed in a constant temperature oven at 160°C. o The reaction was carried out at C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed several times with deionized water, and dried in a drying oven to obtain the target product (Bi-MON).

[0032] The X-ray diffraction pattern of the product obtained in this embodiment is shown in the figure. Figure 1 Scanning electron microscope image (see) Figure 2 The transmission electron microscope image is shown below. Figure 3 Atomic force microscope image (see) Figure 4 The above figure demonstrates the successful preparation of ultrathin nanosheets, and it can be seen that the Bi-MON material synthesized in this embodiment exhibits an ultrathin nanosheet morphology with a thickness of only 3 nm.

[0033] Example 2: Electrocatalytic CO2RR Activity Test of Bi-MON The electrocatalytic CO2RR activity of the bismuth-based organometallic nanosheets (Bi-MON) prepared in Example 1 was tested using the following method: The electrocatalytic CO2RR performance of the Bi-MON material obtained in Example 1 was tested in an H-type electrolytic cell using a typical three-electrode system on a CHI760E electrochemical workstation. The electrochemical testing temperature was controlled at 25°C. o At room temperature, the electrolyte was a 0.5 M KHCO3 solution. Ag / AgCl and Pt sheets were used as the reference and counter electrodes of the reaction system. Working electrode preparation: 4 mg of Bi-MON catalyst was weighed, and 190 µL of isopropanol and 10 µL of Nafion solution were added. The mixture was ultrasonically dispersed to prepare Bi-MON catalyst ink. 10 µL of Bi-MON catalyst ink was uniformly coated onto a 5 mm L-shaped glassy carbon electrode and allowed to dry at room temperature to form a uniform thin film, thus preparing the working electrode.

[0034] Figure 5 As shown, linear sweep voltammetry tests were conducted in N2 and CO2-saturated electrolytes, respectively, at a scan rate of 5 mV / s. The figure shows that the catalytic current density of Bi-MON in a CO2 atmosphere is significantly higher than that in an N2 atmosphere, indicating that it possesses good electrocatalytic CO2RR activity.

[0035] Example 3: Electrocatalytic CO2RR selectivity and stability test of Bi-MON The electrocatalytic CO2RR activity of the bismuth-based organometallic nanosheets (Bi-MON) prepared in Example 1 was tested using the following method: The Bi-MON catalyst ink obtained in Example 2 was uniformly coated (10 µL) onto a glassy carbon sheet (working area 1 cm × 1 cm) to prepare a working electrode for electrocatalytic CO2RR selectivity and stability testing. Constant potential electrolysis was performed for 1 h at five potentials within the range of -0.7 V to -1.2 V versus RHE. After electrolysis, the electrolyte was collected, and the liquid products were analyzed using nuclear magnetic resonance (NMR) spectroscopy to determine product selectivity. Stability testing was conducted at a constant potential of -1 V versus RHE.

[0036] Figure 6 The Faradaic efficiency of CO2 reduction to formate at different potentials was calculated. It can be seen that the Faradaic efficiency of Bi-MON is above 80% when the applied voltage is -0.7 V to -1.2 V. Furthermore, the Faradaic efficiency of Bi-MON reaches as high as 96% when the applied voltage is -1 V, indicating that the Bi-MON prepared in this invention has excellent electrocatalytic CO2 RR performance.

[0037] Figure 7 The electrocatalytic CO2RR stability test of Bi-MON showed that it has good electrocatalytic CO2RR stability.

[0038] Example 4: Electrocatalytic CO2RR performance test of Bi-MON in a flow cell The electrocatalytic CO2RR performance of the bismuth-based organometallic nanosheets (Bi-MON) prepared in Example 1 was tested in a flow cell. The test method is as follows: 4 mg of Bi-MON catalyst was weighed and added to 190 µL of isopropanol and 10 µL of Nafion solution. The mixture was then ultrasonically dispersed to prepare Bi-MON catalyst ink. The uniformly dispersed catalyst ink was then deposited onto the surface of carbon paper using a spray coating method, resulting in a 1 × 1 cm² sheet. 2 The catalyst layer serves as the gas diffusion electrode (GDE) in a flow cell configuration. Electrochemical measurements are performed in a flow cell equipped with separate cathode and anode chambers (1 cm × 1 cm × 1 cm), physically separated by a proton exchange membrane. Both chambers have dedicated electrolyte inlets and outlets, and a precision peristaltic pump maintains an electrolyte circulation rate of 5 sccm. In the three-electrode system, the Ag / AgCl reference electrode is placed in the cathode chamber, while the GDE and platinum counter electrode maintain the same geometric surface area (1 cm²). 2The CO2 reduction reaction (CO2RR) experiment was conducted systematically under ambient conditions using a 1.0 M KHCO3 electrolyte in a flow cell apparatus. During the electrochemical testing, gaseous CO2 was continuously supplied to the cathode GDE side through a dedicated gas channel at a flow rate of 5 sccm to achieve continuous CO2 saturation.

[0039] Figure 8 As shown, linear sweep voltammetry tests were conducted in N2 and CO2-saturated electrolytes, respectively, at a scan rate of 5 mV / s. The figure shows that the catalytic current density of Bi-MON in a CO2 atmosphere is significantly higher than that in an N2 atmosphere, indicating that it possesses good electrocatalytic CO2RR activity.

[0040] Figure 9 To determine the Faraday efficiency of CO2 reduction to formate at different potentials, at 0.1 A·cm 2 Up to 0.7 A·cm 2 At current densities of 0.4 A·cm⁻¹, the Faraday efficiency of Bi-MON is consistently above 91%; among them, at 0.4 A·cm⁻¹, the efficiency is even higher. 2 At a current density of 97.1%, the Faraday efficiency of Bi-MON reached a maximum of 97.1%, indicating that the Bi-MON prepared in this invention has excellent electrocatalytic CO2RR performance.

[0041] In summary, the bismuth-based organometallic nanosheets prepared in this invention exhibit good electrocatalytic CO2RR activity and selectivity at 0.4 A·cm⁻¹. 2 The Faraday efficiency for generating formate at industrial-grade current densities can reach 97.1%, thus it has good application prospects in the electrocatalytic reduction of carbon dioxide to prepare formate.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a bismuth-based metal-organic nanosheet material, characterized in that, Includes the following steps: Bismuth-based organometallic nanosheets were prepared by a one-step hydrothermal method using aminosuccinic acid and bismuth salt as raw materials.

2. The preparation method according to claim 1, characterized in that, The preparation method includes the following specific steps: S1. Dissolve aminosuccinic acid in water to prepare a ligand solution; S2. Add the bismuth salt to the ligand solution and mix thoroughly to prepare a mixed solution; S3. The mixed solution is reacted under heating conditions. After the reaction is completed, the product is collected, washed, and dried to obtain bismuth-based organometallic nanosheet material.

3. The preparation method according to claim 2, characterized in that, In step S1, the concentration of the ligand solution is 0.1 mol / L to 1 mol / L.

4. The preparation method according to claim 2, characterized in that, In step S2, the metal bismuth salt includes bismuth nitrates, chlorides, sulfates, acetates, and hydrates of the salt.

5. The preparation method according to claim 2, characterized in that, The molar ratio of bismuth atoms to aminosuccinic acid in the bismuth salt is 1:1 to 1:

10.

6. The preparation method according to claim 2, characterized in that, In step S3, the reaction temperature is 120℃~160℃, and the reaction time is 8 h~24 h.

7. A bismuth-based metal-organic nanosheet material, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 6.

8. The bismuth-based metal-organic nanosheet material according to claim 7, characterized in that, The bismuth-based metal-organic nanosheet material exhibits an ultrathin nanosheet morphology with a thickness of 1~4 nm.

9. The application of the bismuth-based organometallic nanosheet material according to any one of claims 7 to 8 in the electrocatalytic reduction of carbon dioxide to prepare formate.

10. The application according to claim 9, characterized in that, The method of application includes: fabricating the bismuth-based metal-organic nanosheet material into a working electrode, using a three-electrode system, with KHCO3 solution as the electrolyte, and introducing CO2 gas into the cathode chamber to prepare formate; The method for preparing the working electrode includes: mixing the bismuth-based metal-organic nanosheet material with isopropanol and Nafion solution to obtain a mixed solution; ultrasonically dispersing the mixed solution to prepare a catalyst ink; uniformly coating the catalyst ink onto a glassy carbon electrode and drying it to form a uniform thin film to prepare the working electrode.

Images