Bi / bi2o2co3 nanoflower sheet derived from bi / biobr and preparation method and application thereof
By preparing Bi/Bi2O2CO3 nanoflowers derived from Bi/BiOBr reconstruction, the problems of narrow selectivity and difficulty in identifying active sites of Bi-based catalysts were solved, achieving highly efficient electrocatalytic reduction of carbon dioxide to formic acid with high activity and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN UNIV
- Filing Date
- 2025-01-22
- Publication Date
- 2026-07-21
AI Technical Summary
Existing Bi-based catalysts suffer from narrow selectivity, low current density, and difficulty in identifying active sites during electrocatalytic carbon dioxide reduction, and are prone to remodeling, which limits their industrial-scale application.
By preparing Bi/BiOBr reconstructed Bi/Bi2O2CO3 nanoflowers, Bi-MOF was synthesized by solvothermal method, Bi/BiOBr structure was formed by high-temperature pyrolysis, and Bi/Bi2O2CO3 nanoflowers were reconstructed by electrochemical reduction method, providing more active sites and stability.
It achieves stable catalytic reduction of carbon dioxide to formate under high current density within a wide potential window, exhibiting high selectivity and activity, good stability, and the ability to be recycled for more than 100 hours.
Smart Images
Figure CN119980330B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalysts, specifically relating to a Bi / Bi2O2CO3 nanoflower-like structure derived from Bi / BiOBr reconstruction, its preparation method, and its application. Background Technology
[0002] In recent years, electrocatalytic carbon dioxide reduction (CO2RR) technology has become one of the important ways to realize CO2 resource utilization due to its advantages such as environmental friendliness, energy efficiency and low raw material cost.
[0003] Among the many CO2 reduction products, while intuitively we might want to control selectivity to obtain higher-value products such as ethylene, ethanol, and n-propanol, economic and technical analysis clearly indicates that, overall, those C2+ products do not necessarily achieve the greatest economic benefits. Instead, the two-electron products of electrochemical CO2 reduction, such as CO or HCOOH, are the most economically feasible. Formic acid is an important chemical intermediate in many industrial processes, widely used in the leather, pesticide, pharmaceutical, dye, and rubber industries. It can also be used directly as a chemical fuel for formic acid (or formate) fuel cells. The industrial production of formic acid is typically achieved through the carbonylation of methanol and subsequent hydrolysis of methyl formate. However, this process is energy-intensive and is usually limited by reaction rate, byproducts, and investment costs. Therefore, direct electrochemical CO2 reduction to formic acid under mild conditions with high energy conversion efficiency is very attractive. In recent years, bismuth (Bi) electrocatalysts have attracted considerable attention due to their excellent formate selectivity, high hydrogen evolution reaction (HER) overpotential, low toxicity, and low cost. However, bismuth-based catalysts also have some drawbacks. Although Bi-based catalysts exhibit high selectivity, their high-selectivity potential range is narrow, and their bias current density is low. Furthermore, Bi-based catalysts are prone to remodeling during the electrocatalytic reduction of carbon dioxide, making the active sites difficult to identify. Therefore, designing and preparing low-cost bismuth-based catalysts with high selectivity and activity over a wide potential range and elucidating their active sites is of great significance for promoting the practical application of electroreduction of carbon dioxide on an industrial scale. Summary of the Invention
[0004] The purpose of this invention is to provide a Bi / Bi2O2CO3 nanoflower derived from Bi / BiOBr reconstruction, its preparation method, and its application.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction includes the following steps:
[0007] Step 1: Disperse the bismuth source and ligand in a solvent, stir and mix evenly, and carry out a thermal reaction to generate Bi-MOF;
[0008] Step 2: Add the obtained Bi-MOF to a brominating reagent for hydrothermal bromination to obtain the brominated Bi-MOF;
[0009] Step 3: The brominated Bi-MOF is pyrolyzed in an inert gas atmosphere to form the Bi / BiOBr precursor;
[0010] Step 4: Prepare the Bi / BiOBr precursor into a working electrode, and reconstruct and reduce it under an applied voltage to obtain a Bi / Bi2O2CO3 composite material.
[0011] In step 1, the molar ratio of bismuth source to ligand is 1:(9-13); preferably 1:11.7.
[0012] Preferably, the temperature of the thermal reaction is 100-150℃; more preferably, it is 120℃.
[0013] Preferably, the bismuth source is one or a mixture of bismuth nitrate, bismuth chloride, or bismuth acetate; preferably, the ligand is 1,3,5-pyromellitic acid.
[0014] In step 2, the mass ratio of Bi-MOF to the brominizing agent is 1:(1-3); preferably 1:1.6.
[0015] Preferably, the brominating agent is NH4Br;
[0016] The preferred heating temperature is 80-100℃; preferably 90℃.
[0017] In step 3, the pyrolysis temperature is 400–700℃, and the pyrolysis time is 1–2 hours.
[0018] Preferably, the pyrolysis temperature is 500℃.
[0019] The specific steps in step 4 are as follows: Prepare the obtained Bi / BiOBr into an ink solution (5mg Bi / BiOBr + 1000μL water + 960μL isopropanol + 40μL nafion solution), take 200μL of ink solution and spray it onto the electrode, perform cyclic voltammetry scanning (CV) in a CO2-saturated 0.5M KHCO3 electrolyte with a potential range of 0.68 to -1.22V vs. RHE, and electrolyze for 0 to 30 minutes at -0.72 to -1.12V vs. RHE to obtain Bi / Bi2O2CO3 nanoflowers.
[0020] Preferably, electrolysis is performed at -0.82V vs. RHE for 0–30 min.
[0021] The present invention also includes a Bi / Bi2O2CO3 nanoflower obtained by the preparation method described above.
[0022] The present invention also includes an application of the Bi / Bi2O2CO3 nanoflowers described above.
[0023] It is used in the electrocatalytic reduction of carbon dioxide to formic acid.
[0024] Compared with the prior art, the beneficial effects of the present invention are:
[0025] This invention synthesizes brominated Bi-MOF using a simple solvothermal method. Utilizing the carbon element contained in the Bi-MOF ligands, partial Bi is removed through high-temperature pyrolysis under inert gas conditions. 3+ Restored to Bi 0 A Bi / BiOBr structure is generated in one step, and then reconstructed into a Bi / Bi2O2CO3 composite nanoflower structure through electrochemical reduction.
[0026] In the course of this study, the structural evolution of Bi-based catalysts was explored. The changes in their reconstruction were mainly recorded by XRD and SEM, which provides a certain reference for speculating on the mechanism of evolution of Bi-based materials in electrocatalytic carbon dioxide reduction.
[0027] This invention can stably catalyze the reduction of carbon dioxide to formate under a wide potential window and high current density. Attached Figure Description
[0028] Figure 1 A schematic diagram of the synthesis of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction;
[0029] Figure 2 Scanning electron microscope image of Bi / Bi2O2CO3 nanoflowers (reduced at -0.82V vs. RHE for 30 min);
[0030] Figure 3 Transmission electron microscope image of Bi / Bi2O2CO3 nanoflowers (reduced at -0.82V vs. RHE for 30 min);
[0031] Figure 4 XRD structures of Bi-MOF precursors after pyrolysis and bromination at different temperatures;
[0032] Figure 5 The image shows the XRD pattern of the precursor after calcination at 500°C in Example 2.
[0033] Figure 6 This is a scanning electron microscope image of the precursor after calcination at 500℃ in Example 2;
[0034] Figure 7 This is a transmission electron microscope image of the precursor after calcination at 500°C in Example 2;
[0035] Figure 8 Scanning electron microscope images of samples prepared for Examples 1, 2, 3-6 are shown, recording the changes in the morphology of the precursor Bi / BiOBr with reduction time under the condition of -0.82V vs. RHE potential.
[0036] Figure 9 Crystal structure diagrams of the catalysts prepared in Examples 1, 2, 3-6;
[0037] Figure 10 Scanning electron microscope images of the catalysts prepared for comparative examples 1-6;
[0038] Figure 11 XRD patterns of the catalysts prepared for comparative examples 1-6.
[0039] Figure 12 Raman spectra of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr before and after derivation, and comparison samples;
[0040] Figure 13 A comparison of the electrochemically active area of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction with that of the control sample;
[0041] Figure 14 LSV curves and formic acid partial current density curves of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction;
[0042] Figure 15 The product Faraday efficiency diagram of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction;
[0043] Figure 16 This is a stability test diagram of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction. Detailed Implementation
[0044] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.
[0045] Example 1
[0046] Bi / Bi₂O₂CO₃ nanoflowers were prepared by combining a pyrolysis Bi-MOF strategy and an electrochemical reduction method. The preparation process included the following steps ( Figure 1 (See flowchart)
[0047] Step 1: Dissolve 0.15 g Bi(NO3)3·5H2O and 0.75 g H3BTC (1,3,5-tristyric acid) in 60 ml of methanol solution, transfer the solution to a 100 ml reactor liner, stir for 20 min, and hydrothermally heat at 120 °C for 24 h. The resulting white powder is washed three times with methanol and then placed in a vacuum oven at 60 °C for 9 h. The product obtained is denoted as Bi-MOF.
[0048] Step 2: Immerse 600 mg Bi-MOF in 60 mL of deionized water, stir, then add 0.012 mol (1 g) NH4Br, stir for 20 min, then heat to 90 °C and stir for 1 h. After removal, filter and dry in a vacuum oven at 60 °C for 9 h to obtain brominated Bi-MOF.
[0049] Step 3: The brominated Bi-MOF was directly placed in a tube furnace and pyrolyzed at 500℃ for 2 hours under Ar (100 ml / min) conditions to obtain the final product Bi / BiOBr.
[0050] Step 4: Prepare the obtained Bi / BiOBr into an ink solution (5mg Bi / BiOBr + 1000μL water + 960μL isopropanol + 40μL nafion solution). Spray 200μL of ink onto the electrode and perform 6 cycles of cyclic voltammetry (CV) in a CO2-saturated 0.5M KHCO3 electrolyte, with a potential range of 0.68 to -1.22V vs. RHE. Electrolyze for 30 minutes at -0.82V vs. RHE to obtain Bi / Bi2O2CO3 nanoflowers.
[0051] The morphology of the material prepared in Example 1 was characterized, and the results are shown in the figure. Figure 2 and Figure 3 ,Depend on Figure 2 and Figure 3 It can be seen that Example 1 prepared a catalyst with a nano-flower shape, and the flower has abundant wrinkles.
[0052] Example 2
[0053] Only step 3 of Example 1 was performed, and the pyrolysis temperature conditions were changed to 400, 500, 600 and 700°C to investigate the structure of the generated precursor.
[0054] The crystal structures of the Bi-based compounds prepared at different pyrolysis temperatures in Example 2 were identified, and the results are shown in [Figure 2]. Figure 4 , Figure 4The images show the XRD structures of Bi-MOF precursors after pyrolysis and bromination at different temperatures. It can be seen that a Bi / BiOBr structure is formed at lower pyrolysis temperatures, while most of it transforms into Bi at temperatures exceeding 600℃. 24 Br 10 O 31 Mutually.
[0055] Figure 5 The image shows the XRD pattern of the precursor after calcination at 500°C in Example 2. It can be seen that the precursor crystal phase after calcination at 500°C consists only of Bi and BiOBr.
[0056] Figure 6 The image shown is a scanning electron microscope image of the precursor after calcination at 500℃ in Example 2. It can be seen that the precursor after calcination at 500℃ exhibits an irregular nanosheet shape.
[0057] Figure 7 The image shown is a transmission electron microscope (TEM) image of the precursor calcined at 500°C in Example 2. It can be seen that the Bi / BiOBr precursor calcined at 500°C exhibits a porous nanosheet morphology. This may be due to the reduction of Bi by C in the MOF ligands during pyrolysis. 3+ And thus formed.
[0058] Example 3
[0059] Based on Example 1, the step of electrical reduction at -0.82V vs. RHE potential is removed, and only the CV step is retained.
[0060] Example 4
[0061] Based on Example 1, only the electroreduction time was changed to 2 minutes.
[0062] Example 5
[0063] Based on Example 1, only the electroreduction time was changed to 5 minutes.
[0064] Example 6
[0065] Based on Example 1, only the electroreduction time was changed to 15 minutes.
[0066] Figure 8 Scanning electron microscope (SEM) images of the samples from Examples 1 (30 min), 2 (pyrolysis at 500 °C), and 3-6 are shown, recording the changes in the morphology of the precursor Bi / BiOBr with reduction time under a potential of -0.82 V vs. RHE. The images show that after CV, the catalyst morphology changes; irregular nanosheets transform into leaf-like nanosheets, until after 15 min, the leaf-like nanosheets connect to each other, forming a nanofloral shape.
[0067] Figure 9 The crystal structures of the catalysts prepared in Examples 1 (30 min), 2 (pyrolysis at 500 °C), and 3-6 are shown. The changes in crystal structure from the initial Bi / BiOBr precursor under CV and different electrolysis time conditions are recorded. As can be seen from the figure, Bi / BiOBr immediately undergoes reconstruction after CV, evolving into a mixed phase of Bi and Bi2O2CO3, and these two crystal structures are maintained throughout the subsequent electrolysis process.
[0068] Comparative Example 1
[0069] Step 1: Dissolve 0.15 g Bi(NO3)3·5H2O and 0.75 g H3BTC (1,3,5-tristyric acid) in 60 ml of methanol solution, transfer the solution to a 100 ml reactor liner, stir for 20 min, and hydrothermally heat at 120 °C for 24 h. The resulting white powder is washed three times with methanol and then placed in a vacuum oven at 60 °C for 9 h. The product obtained is denoted as Bi-MOF.
[0070] Step 2: The Bi-MOF formed in Step 1 was directly pyrolyzed at 600℃ for 1h under an Ar atmosphere (100ml / min) to generate the control sample Bi / Bi2O3.
[0071] Comparative Example 2
[0072] The sample from Comparative Example 1 was prepared as an ink solution (as above), sprayed onto the electrode, and subjected to 6 cycles of cyclic voltammetry (CV) in a CO2-saturated 0.5M KHCO3 electrolyte, with a potential range of 0.68 to -1.22 V vs. RHE.
[0073] Comparative Example 3
[0074] The sample from Comparative Example 1 was prepared as an ink solution, sprayed onto the electrode, and subjected to 6 cycles of cyclic voltammetry (CV) in a CO2-saturated 0.5M KHCO3 electrolyte with a potential range of 0.68 to -1.22 V vs. RHE. Electrolysis was then carried out for 10 min at a potential of -0.82 V vs. RHE.
[0075] Comparative Example 4
[0076] The sample from Comparative Example 1 was prepared as an ink solution, sprayed onto the electrode, and subjected to 6 cycles of cyclic voltammetry (CV) in a CO2-saturated 0.5M KHCO3 electrolyte with a potential range of 0.68 to -1.22 V vs. RHE. Electrolysis was then carried out for 20 min at a potential of -1.5 V vs. RHE.
[0077] Comparative Example 5
[0078] The sample from Comparative Example 1 was prepared as an ink solution, sprayed onto the electrode, and subjected to 6 cycles of cyclic voltammetry (CV) in a CO2-saturated 0.5M KHCO3 electrolyte, with a potential range of 0.68 to -1.22 V vs. RHE, and then electrolyzed for 30 min at a potential of -0.82 V vs. RHE.
[0079] Comparative Example 6
[0080] The sample from Comparative Example 1 was prepared as an ink solution, sprayed onto the electrode, and subjected to 6 cycles of cyclic voltammetry (CV) in a CO2-saturated 0.5M KHCO3 electrolyte, with a potential range of 0.68 to -1.22 V vs. RHE, and then electrolyzed for 1 h at a potential of -0.82 V vs. RHE.
[0081] Figure 10 Scanning electron microscopy (SEM) was used to record the morphology of the precursor Bi / Bi₂O₃ with reduction time at -0.82 V vs. RHE potential for the catalysts prepared in Comparative Examples 1-6. The figures show that the morphology remained essentially unchanged after CV and electrolysis at different times.
[0082] Figure 11 The XRD patterns of the catalyst samples prepared for Comparative Examples 1-6 are shown, recording the changes in the crystal structure of the precursor Bi / Bi₂O₃ with reduction time at -0.82 V vs. RHE potential. The figures show that the crystal structure remained essentially unchanged after CV and electrolysis at different times.
[0083] Figure 12 The images show the Raman spectra of the Bi / Bi2O2CO3 nanoflora (Example 1) before and after derivatization, and the comparative sample (Comparative Example 1), which was reconstructed from Bi / BiOBr (calcined at 500℃ in Example 2). It can be seen that after CV and electrochemical reduction, the Bi / BiOBr precursor evolved into structures of Bi and Bi2O2CO3.
[0084] Figure 13 This is a comparison diagram of the electrochemically active area of the Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction (Example 1) and the control sample (Comparative Example 1). It can be seen that the derived Bi / Bi2O2CO3 nanoflowers have a larger electrochemically active area compared to Bi / Bi2O3 and commercial Bi powder.
[0085] Figure 14The LSV curves and bias current density curves of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction (Example 1) are shown. It can be seen that the derived Bi / Bi2O2CO3 nanoflowers have higher electrocatalytic activity and higher CO2 catalytic efficiency compared with Bi / Bi2O3 and commercial Bi powder.
[0086] Figure 15 The image shows the product Faradaic efficiency of Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction. It can be seen that the Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction can maintain a formic acid Faradaic efficiency exceeding 90% over a wide potential range.
[0087] Figure 16 The image shows the stability test results of Bi / Bi2O2CO3 nanoflora derived from Bi / BiOBr reconstruction. It can be seen that the catalyst can be cycled for 100 hours or more, and the current remains at 18 mA / cm² in an H cell at -0.82 V vs. RHE. -2 It exhibits excellent stability.
[0088] In summary, this invention provides a Bi / Bi₂O₂CO₃ nanofloral sheet with a high electrochemical active area, offering a large number of exposed active sites and significantly improving the efficiency of electrocatalytic CO₂ to formic acid production. In the preparation examples, we investigated the evolution of the catalyst by varying parameters such as electrolysis time, primarily using XRD and SEM characterization. Furthermore, this catalyst exhibits the following advantages during the catalytic process:
[0089] 1. Bi / Bi2O2CO3 nanoflowers have a high electrochemical active surface area (ECSA), thus providing more reaction sites and promoting the CO2 reduction reaction.
[0090] 2. Bi / Bi2O2CO3 nanoflowers exhibit a formic acid Faraday efficiency exceeding 90% over a wide potential range, thus demonstrating excellent formic acid selectivity.
[0091] 3. Bi / Bi2O2CO3 nanoflowers can be rapidly reconstructed using Bi / BiOBr. The reconstruction time is short, and complete reconstruction can occur after CV and 15 minutes of point reduction.
[0092] 4. Bi / Bi2O2CO3 nanoflowers have high stability and can be recycled for more than 100 hours.
[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction, characterized in that, Includes the following steps: Step 1: Disperse the bismuth source and ligand in a solvent, stir and mix evenly, and carry out a solvothermal reaction to generate Bi-MOF; Step 2: Add the obtained Bi-MOF to a brominating reagent for hydrothermal bromination to obtain the brominated Bi-MOF; Step 3: The brominated Bi-MOF is placed in an inert gas atmosphere for pyrolysis to form Bi / BiOBr precursor; the pyrolysis temperature is 400-700℃ and the pyrolysis time is 1-2h. Step 4: Prepare the Bi / BiOBr precursor into a working electrode, and reconstruct and reduce it under an applied voltage to obtain a Bi / Bi2O2CO3 composite material; prepare the obtained Bi / BiOBr into an ink solution and spray it onto the electrode; perform cyclic voltammetry scanning (CV) in a CO2-saturated 0.5M KHCO3 electrolyte with a potential range of 0.68 to -1.22 V vs. RHE, and electrolyze for 15 to 30 min at -0.72 to -1.12 V vs. RHE to obtain Bi / Bi2O2CO3 nanoflowers.
2. The method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction according to claim 1, characterized in that, In step 1, the molar ratio of bismuth source to ligand is 1:(9-13); The temperature of the thermal reaction is 100-150℃; The bismuth source is one or a mixture of bismuth nitrate, bismuth chloride, or bismuth acetate; The ligand is 1,3,5-trimethylbenzene acid.
3. The method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction according to claim 1, characterized in that, In step 1, the molar ratio of bismuth source to ligand is 1:11.7; the temperature of the thermal reaction is 120℃.
4. The method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction according to claim 1, characterized in that, In step 2, the mass ratio of Bi-MOF to the brominizing agent is 1:(1-3). The brominating agent is NH4Br; The heating temperature is 80-100℃.
5. The method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction according to claim 1, characterized in that, In step 2, the mass ratio of Bi-MOF to the brominizing agent is 1:1.6, and the heating temperature is 90℃.
6. The method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction according to claim 1, characterized in that, The pyrolysis temperature in step 3 is 500℃.
7. The method for preparing Bi / Bi2O2CO3 nanoflowers derived from Bi / BiOBr reconstruction according to claim 1, characterized in that, In step 4, electrolysis is performed at -0.82 V vs. RHE for 15–30 min.