Preparation method of formic acid
By using titanium-doped bismuth-based materials with nanorod morphology as electrocatalysts, the problems of hydrogen evolution interference and poor stability of bismuth-based catalysts in electrochemical reduction reactions were solved, and the efficient preparation of formic acid was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- EAST CHINA UNIV OF SCI & TECH
- Filing Date
- 2026-02-09
- Publication Date
- 2026-05-08
AI Technical Summary
Bismuth-based catalysts exhibit competitive hydrogen evolution reactions in electrochemical reduction reactions, severely interfering with formic acid formation, and have poor stability, making it impossible to carry out reactions for extended periods.
Titanium-doped Bi4Ti3O12 materials were prepared by hydrothermal and calcination methods using nanorod-shaped titanium-doped bismuth-based materials as electrocatalysts to suppress hydrogen evolution reaction and improve formic acid selectivity.
The formic acid faradaic efficiency reaches over 90% over a wide current density range, significantly improving catalytic performance and stability. It can stably produce formic acid in a fluid electrolyzer and efficiently prepare pure formic acid in a solid electrolyzer.
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Figure CN121992441A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon dioxide electrochemical reduction technology, specifically to a method for preparing formic acid. Background Technology
[0002] Carbon dioxide conversion technologies have attracted widespread attention. Among them, carbon dioxide electrocatalytic reduction technology, as a highly efficient carbon capture and utilization method, has become one of the key technologies for addressing climate change and reducing greenhouse gas emissions. Formic acid, as one of the main products of carbon dioxide reduction, has important applications in chemical synthesis and energy storage. Formic acid is not only an important raw material in the chemical industry, but it can also serve as an effective hydrogen source and energy carrier, playing a crucial role in fuel cells and energy storage. Compared to other carbon dioxide reduction products, formic acid has a higher energy density and a lower environmental impact, thus it is considered an ideal target product in carbon dioxide reduction technologies.
[0003] Bismuth-based catalysts have been shown to have catalytic activity for the reduction of CO2 to formic acid. The bismuth-oxygen bond (Bi-O) is the key active site of bismuth-based catalysts. However, bismuth-based catalysts exhibit competitive hydrogen evolution reaction in electrochemical reduction reactions, which seriously interferes with the formation of formic acid. Furthermore, due to their poor stability, bismuth-based catalysts cannot undergo reactions for extended periods. Summary of the Invention
[0004] The purpose of this invention is to overcome the technical problems of existing bismuth-based catalysts, such as the competitive hydrogen evolution reaction in electrochemical reduction reactions, which seriously interferes with the formation of formic acid, and the poor stability of bismuth-based catalysts, which prevents them from undergoing long-term reactions. This invention provides a method for preparing formic acid. The present invention uses titanium-doped bismuth-based materials with a nanorod morphology as electrocatalysts, which suppresses the hydrogen evolution reaction in electrochemical reduction reactions, significantly improves the selectivity of formic acid, and has long-term stability in electrolytic cells. In particular, it can efficiently reduce carbon dioxide to pure formic acid in solid-state electrolytic cells.
[0005] To achieve the above objectives, the present invention provides a method for preparing formic acid, comprising electrochemically reducing a material containing carbon dioxide; wherein the cathode electrode used during the electrochemical reduction comprises a titanium-doped bismuth-based material having a nanorod morphology.
[0006] Through the above technical solution, the present invention has at least the following beneficial effects: 1. This invention discovers that using titanium-doped bismuth-based materials with a nanorod morphology as an electrocatalyst for the electrochemical reduction of carbon dioxide to formic acid results in high formic acid selectivity at a current density of 100 mA·cm⁻¹. -2 Up to 300 mA·cm -2Over a wide current density range, the Faradaic efficiency of formic acid can reach over 90%. 2. This invention discovers that using titanium-doped bismuth-based materials with a nanorod morphology as an electrocatalyst for the electrochemical reduction of carbon dioxide to formic acid can undergo a structural transformation to generate basic bismuth carbonate. This structural transformation process endows the material with excellent durability and stable catalytic selectivity during the reaction, significantly improving the overall electrocatalytic performance. 3. The method for preparing formic acid according to the present invention can be used in a fluidized bed electrolyzer, wherein the titanium-doped bismuth-based material is used in the fluidized bed electrolyzer at a current density of 100 to 300 mA·cm⁻¹. -2 Formic acid Faradaic efficiency exceeding 90% can be achieved within a wide range. This is achieved at a current density of 200 mA·cm⁻¹. -2 When the formic acid is in use, it can maintain a Faraday efficiency of over 90% for more than 24 hours, demonstrating excellent selectivity and stability. 4. The method for preparing formic acid according to the present invention can be used in a solid-state electrolytic cell at a current density of 100 mA·cm⁻¹. -2 When the formic acid is stabilized, the formic acid faradaic efficiency is higher than 70% for more than 48 hours, which can efficiently prepare pure formic acid. Attached Figure Description
[0007] Figure 1 The Bi4Ti3O prepared in Example 1 12 TEM images of the sample and SEM images of Bi2O3 obtained in Preparation Example 1 are shown. Figure 1 a is the Bi4Ti3O obtained in Preparation Example 1 12 TEM images, Figure 1 b is a SEM image of Bi2O3 obtained in Comparative Preparation Example 1; Figure 2 These are the XRD spectra of the materials obtained from Preparation Examples 1-3 and Comparative Preparation Example 1, where... Figure 2 a represents the Bi4Ti3O obtained in Preparation Example 1. 12 XRD pattern, Figure 2 b is the XRD pattern of -1 obtained in Preparation Example 2. Figure 2 c is the XRD pattern of -2 obtained in Preparation Example 3. Figure 2 d is the XRD pattern of Bi2O3 obtained from Comparative Preparation Example 1; Figure 3 The Bi4Ti3O prepared in Example 1 12 The graph shows the Faradaic efficiency test results of the electrochemical reduction of carbon dioxide by Bi2O3 obtained in Preparation Example 1 in a fluid electrolytic cell, specifically for hydrogen and formic acid. Figure 3 a represents the load used: Bi4Ti3O 12 The graph shows the Faraday efficiency results of hydrogen and formic acid obtained by using the working electrode as the cathode. Figure 3 b is a graph showing the Faraday efficiency results of hydrogen and formic acid obtained by using a working electrode loaded with Bi2O3 as the cathode. Figure 4 Bi4Ti3O is a loaded Bi4Ti3O that is used for the electrochemical reduction of carbon dioxide in a fluid electrolyzer. 12 In-situ XRD pattern of the working electrode; Figure 5 It uses Bi4Ti3O load 12 Figure 1 shows the monitoring results of the voltage and formic acid Faraday efficiency of the electrochemical reduction of carbon dioxide using the working electrode as the cathode in a fluid electrolytic cell. Figure 6 It uses Bi4Ti3O load 12 The full cell voltage and formic acid Faraday efficiency monitoring results for the electrochemical reduction of carbon dioxide in a solid-state electrolytic cell, with the working electrode as the cathode, are shown in the figure. Detailed Implementation
[0008] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0009] This invention provides a method for preparing formic acid, comprising electrochemically reducing a material containing carbon dioxide; wherein the cathode electrode used during the electrochemical reduction comprises a titanium-doped bismuth-based material having a nanorod morphology.
[0010] In the titanium-doped bismuth-based material of the present invention, titanium atoms are doped into the lattice of bismuth oxide. The interaction between titanium atoms, bismuth atoms, and oxygen atoms enables the construction of highly active sites in the titanium-doped bismuth-based material for the electrochemical reduction of carbon dioxide to formic acid, and reduces the competitive hydrogen evolution reaction in the electrochemical reduction reaction.
[0011] Nanorods are one-dimensional anisotropic rod-shaped structural materials at the nanoscale, with the axial direction as the dominant growth direction and an overall rod-like configuration. A key parameter of nanorods is their aspect ratio, which is the ratio between the axial length and the cross-sectional diameter, typically ranging from 1 to 100. In this invention, as long as the axial direction of the titanium-doped bismuth-based material is the dominant growth direction, nanorods with an aspect ratio >1 theoretically possess highly active sites for the electrochemical reduction of carbon dioxide to formic acid, and can stably undergo structural transformation to generate high-current-density, highly stable basic bismuth carbonate. Therefore, any one-dimensional anisotropic rod-shaped morphology with an aspect ratio >1 falls under the category of nanorods of this invention.
[0012] Nanorods differ significantly from other nanoscale morphologies: nanospheres or nanoparticles are isotropic with no clear axial or radial distinction; nanosheets are two-dimensional sheet-like structures with the two-dimensional planes being the dominant growth direction; nanopolyhedra or nanoframeworks are three-dimensional structures, also without a clear axial or radial distinction. Based on these differences, nanorods can be distinguished from other nanoscale morphologies under an electron microscope.
[0013] The titanium-doped bismuth-based materials of this invention have a nanorod morphology. This invention has found that titanium-doped bismuth-based materials with sheet-like or other morphologies do not improve, and may even reduce, the selectivity for formic acid during electrochemical reduction compared to bismuth oxide.
[0014] It is worth noting that although basic bismuth carbonate has catalytic activity, there are currently almost no technical solutions for directly using basic bismuth carbonate. This is because directly using basic bismuth carbonate results in low current density and poor stability. Obtaining basic bismuth carbonate by using a precursor to undergo structural transformation can relatively improve the current density and stability.
[0015] It is understandable that the microscopic particle arrangement of basic bismuth carbonate obtained from structural transformations of different precursors is usually different, and the structural transformation of the precursor is usually not complete. Electrocatalysts undergoing structural transformations typically contain both the precursor and basic bismuth carbonate, resulting in different catalytic activities after structural transformations of different precursors. For example, several studies have shown that electrocatalysts obtained from precursor structural transformations have current densities of less than 30 mA·cm⁻¹. -2 The previous method could not sustain electrolysis for more than 10 hours; however, this application uses titanium-doped bismuth-based materials with a nanorod morphology as a precursor, and the current density of the electrocatalyst after structural transformation can reach 300 mA·cm⁻¹. -2 It can be continuously electrolyzed for at least 48 hours, and its current density and stability far exceed those of existing materials.
[0016] Typically, the current density for the electrochemical reduction of carbon dioxide to formic acid does not exceed 200 mA·cm⁻¹. -2 Because when it exceeds 200 mA·cm -2 At that time, the selectivity of formic acid decreased significantly, while the titanium-doped bismuth-based material of the present invention can achieve a selectivity of 250 mA·cm⁻¹. -2 It maintains a formic acid faradaic efficiency greater than 95% at current densities up to 300 mA·cm⁻¹. -2 The formic acid faradaic efficiency remains above 90%.
[0017] In the process of structural transformation of other existing precursors, the catalytic activity usually decreases significantly because the original active sites are destroyed during the structural transformation and new active sites have not yet been generated. However, the titanium-doped bismuth-based material of the present invention still retains extremely high formic acid Faradaic efficiency during the structural transformation process. It is speculated that the doping of titanium atoms enables the material to maintain a stable active structure during the structural transformation.
[0018] In some embodiments, the titanium-doped bismuth-based material includes bismuth titanate (Bi4Ti3O4). 12 ).
[0019] In some embodiments, the method for preparing the titanium-doped bismuth-based material includes: S1, a suspension is obtained by mixing a bismuth source, a titanium source and an inorganic alkaline solution; S2, the suspension is subjected to a hydrothermal reaction to obtain the hydrothermal reaction product; S3, calcining the product of the hydrothermal reaction.
[0020] Preferably, the molar ratio of the bismuth source to the titanium source is (0.5-2):1, and more preferably (0.8-1.5):1.
[0021] When preparing bismuth titanate, the molar ratio of bismuth source to titanium source affects the electrochemical reduction performance of carbon dioxide to formic acid by the final prepared bismuth titanate nanorods. The preferred molar ratio of bismuth source to titanium source is (0.5-2):1. If the molar ratio of bismuth source to titanium source is higher than the above range, some bismuth oxide will be generated, which will reduce the overall catalytic activity and the selectivity of the target product to a certain extent. If the molar ratio of bismuth source to titanium source is lower than the above range, some sodium titanate will be generated, which will also reduce the overall catalytic activity and the selectivity of the target product to a certain extent. The preferred molar ratio of bismuth source to titanium source is (0.8-1.5):1, at which point the overall catalytic activity and the selectivity of the target product are further improved.
[0022] Preferably, the temperature of the hydrothermal reaction is 160-200℃.
[0023] Preferably, the hydrothermal reaction takes 18-24 hours.
[0024] Preferably, the calcination temperature is 400-800℃.
[0025] Preferably, the calcination time is 1-4 hours.
[0026] Under the above-preferred preparation conditions, the titanium-doped bismuth-based material prepared has high crystallinity, more regular crystals, and more active sites on the crystal surface, thus exhibiting better catalytic activity.
[0027] In some embodiments, the titanium-doped bismuth-based material has a nanorod morphology with an aspect ratio ≥ 2, preferably a nanorod morphology with a length of 300-800 nm and / or a width of 80-150 nm.
[0028] Compared with nanorod materials with low aspect ratio (1-2), nanorods with aspect ratio ≥2 have higher catalytic activity; when the length of the nanorod is 300-800 nm and the width is 80-150 nm, the catalytic activity of the nanorod can be further improved.
[0029] In some embodiments, the cathode electrode contains 0.8-1.5 mg·cm⁻¹ -2 The titanium-doped bismuth-based material.
[0030] When the loading is less than 0.8 mg·cm -2 When the catalyst layer is relatively sparse and the density of active sites is low, it is easy to lead to enhanced side reactions; while when the loading reaches or exceeds 0.8 mg·cm⁻¹, the catalyst layer is relatively sparse and the density of active sites is low, which can easily lead to enhanced side reactions; -2 Subsequently, the catalyst coverage on the electrode surface was significantly improved, which is beneficial for constructing a stable and uniform reaction interface and enhancing the stable operation of the electrode; however, the loading was higher than 1.5 mg·cm⁻¹. -2 At this point, the catalytic activity did not increase further, suggesting that a high loading rate might clog the gas diffusion layer pores, leading to limited mass transfer. The loading rate was within a reasonable range (0.8-1.5 mg·cm⁻¹). -2 Within this range, mass transfer efficiency, catalytic activity, and stability can be improved simultaneously.
[0031] In some embodiments, the cathode electrode is a carbon sheet electrode loaded with the titanium-doped bismuth-based material. The loading can be carried out in a manner commonly used in the art, such as mixing a liquid phase with the titanium-doped bismuth-based material to obtain a mixed phase, and then using the mixed phase to spray a carbon sheet. The carbon sheet electrode can be any carbon sheet substrate in the art, such as GDE (28BC).
[0032] In some embodiments, the electrochemical reduction includes performing the electrochemical reduction in a fluid electrolytic cell or a solid electrolyte electrolytic cell.
[0033] In some embodiments, the current density of the electrochemical reduction is 100-300 mA·cm⁻¹. -2 .
[0034] In a fluid electrolytic cell, the electrochemical reduction reaction occurs at the catalyst-electrolyte interface, while in a solid electrolytic cell, the electrochemical reduction reaction occurs at the catalyst-ion exchange membrane interface. The titanium-doped bismuth-based material of this invention can adapt to both of these interface environments and can stably produce formic acid at high current densities in both fluid electrolytic cells and solid electrolyte electrolytic cells.
[0035] In this invention, titanium-doped bismuth-based materials are used in a fluid electrolytic cell at a current density of 100 to 300 mA·cm⁻¹. -2 Formic acid Faradaic efficiency exceeding 90% can be achieved within a wide range. This is achieved at a current density of 200 mA·cm⁻¹. -2 When the formic acid is in use, it can maintain a Faraday efficiency of over 90% for more than 24 hours, demonstrating excellent selectivity and stability.
[0036] Specifically, in a solid electrolyte electrolytic cell, at a current density of 100 mA·cm⁻¹ -2 When the formic acid is stabilized, the formic acid faradaic efficiency is higher than 70% for more than 48 hours, which can efficiently prepare pure formic acid.
[0037] In some embodiments, the electrolyte for electrochemical reduction comprises a bicarbonate, wherein the concentration of the bicarbonate is 0.5-2 mol / L. The bicarbonate may be sodium bicarbonate or potassium bicarbonate, etc.
[0038] The present invention will be described in detail below through preparation examples and embodiments.
[0039] In the following preparation examples and embodiments, all reagents used are commonly used in the art. The specific source of the reagents has no effect on the implementation and effect of the present invention. All reagents used in the present invention can be obtained through conventional commercial channels, for example, they can be purchased from Aladdin reagent suppliers.
[0040] In the following preparation examples and embodiments, the transmission electron microscope (TEM) instrument was a Thermo Fisher Talos F200X, the scanning electron microscope (SEM) instrument was a SU-8020, and the X-ray diffraction (XRD) instrument was a D / MAX 2550 VB / PC. The relevant test methods are as described in the instruction manuals of the above instruments.
[0041] In the following preparation examples and embodiments, the Faradaic efficiency (charge utilization efficiency) of the product is calculated according to the following formula: Faradaic efficiency (%) = nmF / Q × 100%. Where n is the number of electrons transferred, m is the amount of substance of the product, and F is the Faradaic constant 96485 C mol. -1 Q represents the total charge consumed in the reaction.
[0042] Preparation Example 1 Step (1): Mix 10 mL of 0.1 mol / L bismuth nitrate solution and 10 mL of 0.1 mol / L titanium sulfate solution evenly, and then add 10 mL of 1 mol / L NaOH solution dropwise to form a precipitate, thus obtaining a suspension.
[0043] Step (2): The suspension was subjected to hydrothermal reaction at 200℃ for 20h. After the hydrothermal reaction was completed, it was cooled to room temperature. The product was collected and washed with water and ethanol in sequence. The washed product was placed in a vacuum oven and dried at 60℃ for 6h to obtain the precursor powder.
[0044] Step (3): After transferring the precursor powder to an alumina crucible, it was placed in a muffle furnace and calcined at 800°C for 2 hours in air atmosphere to finally obtain titanium-doped bismuth-based material (denoted as Bi4Ti3O). 12 ).
[0045] Preparation Example 2 The difference from Preparation Example 1 is that the hydrothermal reaction temperature in step (2) is 180℃, and the calcination temperature in step (3) is 600℃. Finally, titanium-doped bismuth-based material-1 (denoted as Bi4Ti3O) was obtained. 12 -1).
[0046] Preparation Example 3 The difference from Preparation Example 1 is that the hydrothermal reaction temperature in step (2) is 160℃ and the hydrothermal reaction time is 18h, while the calcination temperature in step (3) is 400℃ and the calcination time is 3h. Finally, titanium-doped bismuth-based material-2 (denoted as Bi4Ti3O) was obtained. 12 -2).
[0047] Comparative Preparation Example 1 The difference from Preparation Example 1 is that step (1) involves adding 10 mL of 1 mol / L NaOH solution to 10 mL of 0.1 mol / L bismuth nitrate solution to form a precipitate and obtain a suspension; finally, bismuth oxide material (denoted as Bi2O3) is obtained.
[0048] The morphology and structure of the materials obtained from Preparation Examples 1-3 and Comparative Preparation Example 1 were characterized.
[0049] Bi4Ti3O obtained in Preparation Example 1 12 Transmission electron microscopy (TEM) imaging and scanning electron microscopy (SEM) imaging of Bi2O3 obtained in Comparative Preparation Example 1 were performed, and the results are as follows: Figure 1 As shown, where, Figure 1 a represents the Bi4Ti3O obtained in Preparation Example 1. 12 The TEM image shows Bi4Ti3O 12 The nanorods were prepared in the form of nanorods. Further measurements of the length and width of each nanorod under TEM revealed that the Bi₄Ti₃O₂ prepared in Example 1... 12 The nanorods range in length from 300 nm to 800 nm and in width from 80 nm to 150 nm. Figure 1b is a SEM image of the Bi2O3 obtained in Comparative Preparation Example 1. It can be seen that the Bi2O3 is in an irregular blocky shape, compared to... Figure 1 The morphology of nanorods in a is relatively coarse, while that of Bi2O3 is relatively rough.
[0050] X-ray diffraction (XRD) tests were performed on the materials obtained from Preparation Examples 1-3 and Comparative Preparation Example 1. The results are as follows: Figure 2 As shown, where, Figure 2 a represents the Bi4Ti3O obtained in Preparation Example 1. 12 XRD pattern, Figure 2 b is the XRD pattern of -1 obtained in Preparation Example 2. Figure 2 c is the XRD pattern of -2 obtained in Preparation Example 3. Figure 2 d is the XRD pattern of Bi2O3 obtained from Comparative Preparation Example 1. Figure 2 a, Figure 2 b and Figure 2 In both c-phase, distinct bismuth titanate characteristic diffraction peaks were observed, indicating that titanium atoms are doped into the crystal lattice. Figure 2 d corresponds to the characteristic diffraction peaks of bismuth oxide. (Comparison) Figure 2 a, Figure 2 b and Figure 2 c, Figure 2 The diffraction peak of a has a higher intensity, a sharper peak shape, and a relatively narrower half-width, suggesting that the Bi4Ti3O obtained in Example 1 was prepared... 12 It has a high degree of crystallinity, and the crystals are more regular.
[0051] Example 1: Electrochemical performance testing in a flowing electrolytic cell Bi4Ti3O prepared in Preparation Example 1 12 The electrochemical reduction performance of CO2 was tested in a flow electrolyzer, with Bi2O3 from Preparation Example 1 used as a control.
[0052] Experimental group: In a flow electrolyzer separated by a Fumasep FAB-PK-130 exchange membrane, a standard three-electrode system was used with a loading of 1 mg·cm⁻¹. -2 Bi4Ti3O 12 GDE (28BC) was used as the working electrode, Ag / AgCl (3M KCl) as the reference electrode, nickel foam as the counter electrode, and 1 M KHCO3 as the electrolyte. Five sets of experiments were set up, with current densities controlled at 100, 150, 200, 250, and 300 mA·cm⁻¹, respectively. -2 Electrochemical CO2 reduction performance was tested.
[0053] Control group: The only difference from the experimental group was that it was loaded with 1 mg·cm³. -2 The GDE (28BC) of Bi2O3 is used as the working electrode.
[0054] The Faraday efficiency of hydrogen (H2) and formic acid (HCOOH) was tested in the experimental and control groups, and the results are as follows: Figure 3 As shown, where, Figure 3 a represents the load used: Bi4Ti3O 12 The graph shows the Faraday efficiency results of hydrogen and formic acid obtained by using the working electrode as the cathode. Figure 3 Figure b shows the Faraday efficiency results of hydrogen and formic acid obtained by using a working electrode loaded with Bi2O3 as the cathode.
[0055] according to Figure 3 It can be seen that using loaded Bi4Ti3O 12 When the working electrode is used as the cathode, at 100-300 mA·cm -2 Electrochemical reduction of CO2 using current densities of 250 mA·cm⁻¹ showed formic acid Faradaic efficiencies exceeding 90%, even at current densities less than or equal to 250 mA·cm⁻¹. -2 Formic acid has a Faraday efficiency of approximately 95%, with almost no hydrogen evolution reaction occurring; however, when using a working electrode supported on Bi₂O₃ as the cathode, at 100 mA·cm⁻¹... -2 At current densities, the Faraday efficiency of formic acid is approximately 50%, greater than 100 mA·cm⁻¹. -2 At that time, the Faraday efficiency of formic acid was less than 30%, and the competitive hydrogen evolution reaction was severe.
[0056] In summary, titanium doping is beneficial for constructing sites with high activity for the reduction of CO2 to formic acid.
[0057] Example 2 To further evaluate the industrial application value of the catalyst, the Bi4Ti3O4 catalyst prepared in Example 1 was tested in a flow electrolyzer. 12 Stability of electrocatalysts.
[0058] According to the method of Example 1, with the start of energization recorded as time 0, at 200 mA·cm -2 In a flow electrolytic cell at a given current density, the Bi₄Ti₃O₂ loaded on the working electrode was detected by quasi-in-situ XRD at 0 h, 0.5 h, 2 h, 12 h, and 24 h. 12 And the substances after their structural transformation, the results are as follows Figure 4 As shown, the peak elution of the carbon substrate of the working electrode is labeled "carbon sheet C(004)", indicating that as the electrochemical reduction reaction proceeds, Bi4Ti3O 12 Gradually undergoing structural reconstruction, it eventually transforms into basic bismuth carbonate; monitoring the voltage and formic acid Faraday efficiency during the above electrochemical reduction reaction yields the following results: Figure 5As shown, the structural transformation did not affect the activity and selectivity of the electrocatalyst. The Faraday efficiency of formic acid remained above 90%, and the cathode cell voltage did not fluctuate significantly.
[0059] In summary, titanium doping ensures the maintenance of key active sites in the catalyst during structural transformation and reconstruction, thereby guaranteeing high-efficiency electrocatalytic CO2 reduction performance.
[0060] Example 3 Solid-state electrolytic cells can effectively reduce the cost of separating liquid-phase products. Furthermore, the Bi₄Ti₃O₂ obtained in Preparation Example 1 was tested in a solid-state electrolyte electrolytic cell. 12 The ability to produce pure formic acid solution.
[0061] In a two-electrode solid-state electrolyzer, anion exchange membranes (Fumasep FAB-PK-130) and cation exchange membranes (Nafion 117) were used for anion and cation exchange, respectively. A loading of 1 mg·cm⁻¹ was used. -2 Bi4Ti3O 12 GDE (28BC) was used as the cathode electrode, Ag / AgCl (3 M KCl) as the reference electrode, iridium-plated titanium felt as the anode electrode, and 0.5 M H₂SO₄ solution as the anolyte. A porous styrene-divinylbenzene sulfonated copolymer was used as the solid ion conductor filling the intermediate electrolytic cell chamber. Formic acid generated in the solid electrolyte was removed using deionized water. The current density was 100 mA·cm⁻¹. -2 Electrochemical CO2 reduction performance was tested.
[0062] The full cell voltage and formic acid Faraday efficiency were measured in the solid-state electrolytic cell described above, and the results are as follows: Figure 6 As shown, during the 48-hour CO2 electroreduction test, the Faraday efficiency of formic acid was approximately 70%, with a final cumulative concentration of 0.19 mol·L⁻¹. -1 A pure formic acid solution. The above demonstrates that the bismuth titanate electrocatalyst of the present invention has great potential in practical applications.
[0063] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing formic acid, characterized in that, This includes electrochemical reduction of materials containing carbon dioxide; wherein the cathode electrode used during the electrochemical reduction comprises a titanium-doped bismuth-based material having a nanorod morphology.
2. The method according to claim 1, wherein, The titanium-doped bismuth-based material includes bismuth titanate.
3. The method according to claim 1 or 2, wherein, The preparation method of the titanium-doped bismuth-based material includes: S1, a suspension is obtained by mixing a bismuth source, a titanium source and an inorganic alkaline solution; S2, the suspension is subjected to a hydrothermal reaction to obtain the hydrothermal reaction product; S3, calcining the product of the hydrothermal reaction.
4. The method according to claim 3, wherein, The molar ratio of the bismuth source to the titanium source is (0.5-2):1, preferably (0.8-1.5):1; And / or, the temperature of the hydrothermal reaction is 160-200°C; And / or, the hydrothermal reaction time is 18-24 hours; And / or, the calcination temperature is 400-800℃; And / or, the calcination time is 1-4 hours.
5. The method according to any one of claims 1-4, wherein, The titanium-doped bismuth-based material has a nanorod morphology with an aspect ratio ≥ 2.
6. The method according to any one of claims 1-5, wherein, The cathode electrode contains 0.8-1.5 mg·cm⁻¹ -2 The titanium-doped bismuth-based material.
7. The method according to claim 6, wherein, The cathode electrode is a carbon sheet electrode loaded with the titanium-doped bismuth-based material.
8. The method according to any one of claims 1-7, wherein, The electrochemical reduction includes electrochemical reduction in a fluid electrolytic cell or a solid electrolyte electrolytic cell.
9. The method according to any one of claims 1-8, wherein, The current density of the electrochemical reduction is 100-300 mA·cm⁻¹. -2 .
10. The method according to any one of claims 1-9, wherein, The electrolyte used during the electrochemical reduction includes bicarbonate; Preferably, the concentration of the bicarbonate is 0.5-2 mol / L.