Electrochemically reconstructed bismuth-based molecular catalyst as well as preparation method and application thereof
By electrochemically reconstructing bismuth-based molecular catalysts on conductive substrates, the problems of high toxicity and poor activity of Pb-based catalysts were solved, enabling the preparation of glyoxylic acid with high efficiency and low toxicity, and improving the current density and Faraday efficiency of the oxalic acid electroreduction reaction.
Patent Information
- Application Number
- CN202511892015.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-02-10
AI Technical Summary
Existing Pb-based catalysts suffer from high toxicity and poor activity at industrial current densities, making it difficult to meet the requirements of high efficiency and environmental protection in the electrochemical reduction of oxalic acid to glyoxylic acid.
Bismuth-based molecular catalysts with electrochemical reconstruction are formed by loading metallic bismuth organic framework molecules on a conductive substrate and electrochemically reducing and reconstructing them under acidic conditions to create modified bismuth materials, thus forming porous bismuth-based catalysts.
It improves the reactivity and selectivity of the catalyst, reduces toxicity, and increases the current density and Faraday efficiency of the electroreduction of oxalic acid to glyoxylic acid. Moreover, the preparation method is simple and inexpensive.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, and particularly relates to an electrochemically reconstructed bismuth-based molecular catalyst, its preparation method and application. Background Technology
[0002] Glyoxylic acid, as an important reactive organic compound, has wide applications in many fine chemical fields. However, current main chemical synthesis methods for glyoxylic acid suffer from high production costs and environmental pollution. Therefore, there is an urgent need to find an efficient and environmentally friendly method for preparing glyoxylic acid.
[0003] The electrochemical reduction of oxalic acid to glyoxylic acid is a green and sustainable glyoxylic acid production process that utilizes intermittent electrical energy as a driving force. This process offers high product selectivity, and oxalic acid, as a raw material, is inexpensive, significantly reducing production costs. Currently, the electrocatalytic reduction of oxalic acid to glyoxylic acid primarily uses Pb-based catalysts, which exhibit high selectivity and Faraday efficiency. Existing Pb-based catalysts are generally prepared through chemical reduction or electrodeposition (commonly using commercial lead foil as the working electrode), producing nanoscale lead particles with porous / sponge-like structures, dendritic / dendritic structures, etc. To further improve performance, other elements are often introduced to form alloys or composite catalysts.
[0004] However, Pb-based catalysts still suffer from high toxicity and poor activity at industrial current densities. Therefore, developing a catalyst with low toxicity and high reactivity is of great significance. Summary of the Invention
[0005] In view of this, the technical problem to be solved by the present invention is to provide a bismuth-based molecular catalyst, its preparation method and application. The bismuth-based catalyst has low toxicity, high reactivity and good selectivity, which is beneficial for application in the electrochemical reduction of oxalic acid to prepare glyoxylic acid, etc.
[0006] This invention provides an electrochemically reconstructed bismuth-based molecular catalyst, comprising a conductive substrate having a porous structure and a bismuth-containing material supported on the conductive substrate; the bismuth-containing material comprises a modified bismuth substance formed by electrochemical reduction and reconstruction of metallic bismuth organic framework molecules under acidic conditions.
[0007] Preferably, the conductive substrate is a carbon fiber substrate; the loading of the modified bismuth material in the bismuth-based molecular catalyst is 0.2~0.8 mg / cm³. 2 .
[0008] This invention provides a method for preparing an electrochemically reconstructed bismuth-based molecular catalyst, comprising the following steps:
[0009] S1. Provide bismuth-metallic organic framework materials;
[0010] S2. Using the aforementioned bismuth organic framework material as a precursor, a dispersion is obtained by mixing it with a binder and a solvent, and then coated onto a conductive substrate.
[0011] S3. The conductive substrate coated with the dispersion is electroreduced under acidic conditions to obtain an electrochemically reconstructed bismuth-based molecular catalyst.
[0012] Preferably, the bismuth-metallic organic framework material is obtained by dissolving pyromellitic acid and bismuth nitrate in a methanol solution under stirring conditions to obtain a mixed solution; and then heating the mixed solution to react, thereby obtaining the final product.
[0013] Preferably, the molar ratio of bismuth nitrate to trimesic acid is 0.8~1.2:20; the heating reaction temperature is 110~130 °C, and the reaction time is 20~24 h.
[0014] Preferably, the adhesive is a Nafion solution, the solvent is ethanol, and the conductive substrate is carbon fiber paper.
[0015] Preferably, the ratio of the precursor to the solvent is 3~9 mg:1~2 mL.
[0016] Preferably, the acidic conditions are achieved using an acidic solution with a pH not higher than 0.7.
[0017] Preferably, the electroreduction uses a relative standard hydrogen electrode with a voltage of -1.0 V to -1.2 V; the electroreduction time is 0.5 to 1 h.
[0018] This invention provides a method for electrocatalytic reduction of oxalic acid, using the bismuth-based molecular catalyst described above, or the bismuth-based molecular catalyst obtained by the preparation method described above.
[0019] This invention provides an electrochemically reconstructed bismuth-based molecular catalyst, on which a modified bismuth material is mainly supported on a conductive substrate, formed by the electrochemical reduction and reconstruction of metallic bismuth organic framework molecules under acidic conditions. Compared with the prior art, this invention uses a bismuth-based molecular catalyst for the electrocatalytic reduction of oxalic acid to glyoxylic acid. The electrochemical reconstruction method improves the current density and Faradaic efficiency in the electrocatalytic reduction of oxalic acid to glyoxylic acid, thus enhancing the catalyst's reactivity and selectivity. Furthermore, the bismuth-based molecular catalyst exhibits low toxicity.
[0020] Meanwhile, the preparation method of the bismuth-based molecular catalyst provided by this invention is simple, easy to synthesize in large quantities, and low in cost. Attached Figure Description
[0021] Figure 1This is a scanning electron microscope image of the Bi-MOF precursor in Embodiment 1 of the present invention;
[0022] Figure 2 This is a scanning electron microscope image of the electrochemically reconstructed bismuth-based catalyst in Example 1 of this invention;
[0023] Figure 3 This is a scanning electron elemental image of the bismuth-based catalyst electrochemically reconstructed in Example 1 of this invention;
[0024] Figure 4 This is a Faraday efficiency diagram of the electrochemically reconstructed bismuth-based catalyst and the bismuth-based catalyst without ligand modification structure in Example 2 of the present invention for the production of glyoxylic acid at different set potentials;
[0025] Figure 5 This is an effective current density diagram of glyoxylic acid production at different set potentials for the electrochemically reconstructed bismuth-based catalyst and the bismuth-based catalyst that has lost its reconstructed structure in Example 2 of the present invention.
[0026] Figure 6 The bismuth-based catalyst reconstructed by electrochemical methods in Example 2 of this invention operates at a current density of 0.2 A / cm². 2 Cyclic performance under certain conditions;
[0027] Figure 7 This is a Faraday efficiency diagram of the electrodeposited bismuth catalyst of Comparative Example 1 of this invention. Detailed Implementation
[0028] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0029] The present invention provides an electrochemically reconstructed bismuth-based molecular catalyst, comprising a conductive substrate having a porous structure, and a bismuth-containing material supported on the conductive substrate;
[0030] The bismuth-containing material includes: modified bismuth substances formed by electrochemical reduction and reconstruction of metallic bismuth organic framework molecules under acidic conditions.
[0031] This invention provides a bismuth-based catalyst with low toxicity, high activity, and high selectivity, which is beneficial for its application in the electrocatalytic reduction of oxalic acid.
[0032] The bismuth-based molecular catalyst provided in this invention includes: a conductive substrate with a porous structure, preferably a carbon fiber substrate, which performs well in electrocatalytic systems; other porous conductive substrates that do not have a detrimental effect on the above reaction can also be used. In this invention, the porous carbon fiber paper substrate provides gas diffusion channels for the bismuth-based molecular catalyst material.
[0033] The conductive substrate is loaded with an active bismuth-containing material, which includes a modified bismuth substance formed by electrochemical reduction and reconstruction of a bismuth-organic framework molecule (which may be represented as Bi-MOF) under acidic conditions. In the bismuth-based molecular catalyst described in this embodiment of the invention, the modified bismuth substance is mainly bismuth particles modified with surface ligands after reconstruction, with a size of about 5-10 micrometers. These particles can serve as stable active sites and have low toxicity.
[0034] In some embodiments, the loading of the modified bismuth substance may be 0.2~0.8 mg / cm³. 2 Further, the concentration was 0.3–0.6 mg / cm³. 2 The bismuth-based molecular catalyst described in this invention embodiment can be referred to as an r-Bi-MOF catalyst, which exhibits high activity in the electroreduction of oxalic acid to prepare glyoxylic acid, at 200 mA / cm². 2 Under certain conditions, the Faraday efficiency can reach 85%.
[0035] This invention provides a method for preparing an electrochemically reconstructed bismuth-based molecular catalyst, comprising the following steps:
[0036] S1. Provide bismuth-metallic organic framework materials;
[0037] S2. Using the aforementioned bismuth organic framework material as a precursor, a dispersion is obtained by mixing it with a binder and a solvent, and then coated onto a conductive substrate.
[0038] S3. The conductive substrate coated with the dispersion is electroreduced under acidic conditions to obtain an electrochemically reconstructed bismuth-based molecular catalyst.
[0039] This invention first synthesizes a bismuth-based organic framework material, and then uses it as a precursor to prepare a bismuth-based catalyst. In a specific embodiment of this invention, under stirring conditions, pyromellitic acid reagent is added to a methanol solution to obtain solution A. Bismuth nitrate is added to solution A and dissolved by ultrasonication to obtain a mixed solution. The mixed solution is then heated to react and prepare the Bi-MOF precursor.
[0040] The bismuth-based organometallic framework material is a bismuth-based metal-organic framework, preferably using trimellitic acid ligand, which has better performance. In the above-mentioned Bi-MOF precursor synthesis process, the molar ratio of bismuth nitrate to trimellitic acid is preferably 0.8~1.2:20. Furthermore, in this embodiment of the invention, the obtained mixed solution is transferred to a stainless steel autoclave lined with polytetrafluoroethylene and placed in an oven to obtain the Bi-MOF precursor through a hydrothermal reaction. The temperature of the oven is preferably 110~130 °C, and the reaction time can be 20~24 h. In some embodiments, the Bi-MOF is a 2-micrometer-long columnar structure.
[0041] In this embodiment of the invention, a Bi-MOF precursor is sprayed onto a carbon paper substrate with a porous structure. Specifically, the Bi-MOF precursor can be mixed with a binder and a solvent to obtain a dispersion, which is then coated onto a conductive substrate. More specifically, the precursor is ultrasonically dispersed in ethanol, and Nafion solution is added as a binder to obtain a dispersion; the prepared ethanol dispersion containing the Bi-MOF precursor is then sprayed onto a carbon fiber substrate.
[0042] In some embodiments, the Bi-MOF precursor loading can be 0.5~1.5 mg / cm³. 2 Preferably, the amount of ethanol used is 1-2 mL, and the amount of Bi-MOF precursor is 3-9 mg; the amount of Nafion solution added is 35 µL of Nafion per 10 mg of precursor, and the carbon paper area can be 6 cm². 2 Nafion solution is a perfluorosulfonic acid resin solution, a homogeneous system with perfluorosulfonic acid resin as the solute and a specific organic solvent (such as alcohols or water-alcohol mixtures) as the dispersion medium. The embodiments of this invention use commercially available Nafion solution, CAS number: 31175-20-9; the supplier can be Aladdin Company, product number: P400486-25ml.
[0043] In a preferred embodiment of the present invention, under acidic conditions, a Bi-MOF precursor sprayed on a carbon fiber substrate is electroreduced to obtain an electrochemically reconstructed bismuth-based molecular catalyst r-Bi-MOF. The electrochemical reconstruction involves applying a reduction potential under acidic conditions after spraying the precursor onto the substrate, causing a change in its morphology and structure. This facilitates control over the morphology and size of the bismuth particles.
[0044] In embodiments of the present invention, the substrate is carbon paper, commonly used in electrocatalytic systems. Preferably, the electroreduction uses an acidic solution with a pH not higher than 0.7, and more preferably 0-0.5; the electroreduction uses a voltage of -1.0 V to -1.2 V relative to a standard hydrogen electrode, and the electroreduction time can be 0.5-1 hour to achieve complete reconstruction. This invention prepares a low-toxicity bismuth-based molecular catalyst through electrochemical reconstruction, which exhibits high reactivity and selectivity, and can improve its current density and Faradaic efficiency in the electrocatalytic reduction of oxalic acid to glyoxylic acid.
[0045] This invention also provides the application of the bismuth-based molecular catalyst described above in the electrocatalytic reduction of oxalic acid; that is, it provides a method for electrocatalytic reduction of oxalic acid, using the bismuth-based molecular catalyst described above, or the bismuth-based molecular catalyst obtained by the preparation method described above.
[0046] In some embodiments, in the H-type cell system, a Nafion 115 membrane is used as the ion exchange membrane, and the obtained electrochemically reconstructed bismuth-based molecular catalyst, a platinum electrode, and a silver / silver chloride electrode are used as the working electrode, counter electrode, and reference electrode, respectively. Oxalic acid is selected as the electrolyte for the cathode catalytic reaction, with a concentration of 1-2 mol / L, and sulfuric acid, specifically 1 mol / L H₂SO₄, is used at the anode. Constant potential testing is employed, with the potential set at -1.0V relative to the standard hydrogen electrode, and constant current testing is performed for 1 hour. Argon gas is introduced into the cathode electrolyte to purge the cathode air, and oxygen generated at the anode during the reaction is released into the air. Gas chromatography is used to monitor the hydrogen content in the cathode catalytic products online, and nuclear magnetic resonance spectroscopy is used to analyze the liquid products.
[0047] The results show that the electrochemical reconstruction of the bismuth-based catalytic material in the embodiments of the present invention improves the reaction activity and selectivity of the catalytic material, thereby improving the Faraday efficiency, current density and stability of the bismuth-based catalyst in the electrocatalytic reduction of oxalic acid to glyoxylic acid.
[0048] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. The substances used in the embodiments of this invention can be purchased commercially or prepared; wherein, Nafion solution, CAS number: 31175-20-9; can be supplied by Aladdin Company, product number: P400486-25ml; the carbon paper area is 6 cm². 2 .
[0049] Example 1
[0050] Under stirring conditions, 1250 mg of trimesic acid was dissolved in 60 mL of methanol to obtain solution A. 150 mg of bismuth nitrate was added to solution A, and the mixture was ultrasonically dissolved to obtain a mixed solution. The mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and placed in an oven at 120 °C for 20–24 h. After washing and drying, the Bi-MOF precursor was obtained. The Bi-MOF precursor was ultrasonically dispersed in 1.5 mL of ethanol, followed by the addition of an appropriate amount of Nafion aqueous solution and ultrasonic dispersion to obtain an ethanol dispersion of the Bi-MOF precursor (the binder dosage was 3.5 μL Nafion per 1 mg of precursor). The prepared ethanol dispersion of the Bi-MOF precursor was sprayed onto a carbon fiber substrate, with a Bi-MOF precursor loading of 1 mg / cm³ on the carbon fiber substrate. 2 In an acidic solution with pH = 0.7, the Bi-MOF precursor sprayed on a carbon fiber substrate was electroreduced at a reduction voltage of -1.0 V relative to a standard hydrogen electrode for 2400 s to obtain the bismuth-based catalyst r-Bi-MOF. The carbon paper area was 6 cm². 2 The precursor weight was 6 mg, the total weight was 68.94 mg, and the total weight after electrochemical reconstruction was 64.86 mg. Therefore, the calculated bismuth-based catalyst loading was 0.32 mg / cm³. 2 .
[0051] Scanning electron microscopy was used to analyze the Bi-MOF precursor in Example 1 and the bismuth-based catalyst r-Bi-MOF obtained by electrochemical reconstruction. The scanning electron microscope image of the Bi-MOF precursor is shown below. Figure 1 See the r-Bi-MOF scanning electron microscope image. Figure 2 EDS chart (see) Figure 3 .
[0052] from Figure 1 The scanning electron microscope image of the Bi-MOF precursor shows that the precursor has a columnar structure of 2 micrometers in length. Figure 2 It can be seen that the morphology of the r-Bi-MOF catalyst obtained after electroreduction reconstruction changes, with a more aggregated central area and fibrous strands extending outwards, with a size of 5-10 micrometers. Figure 3 This indicates that its main component is bismuth, and because of ligand modification, oxygen can be detected on its surface.
[0053] Example 2
[0054] According to Example 1, a bismuth-based catalyst r-Bi-MOF was obtained by electrochemical reduction and reconstruction, with a loading of 0.3~0.6 mg / cm³ on a carbon fiber substrate. 2 The carbon paper has an area of 6 cm². 2The precursor weight was 6 mg, the total weight was 66.35 mg, and the total weight after electrochemical reconstruction was 62.73 mg. Therefore, the calculated bismuth-based catalyst loading was 0.397 mg / cm³. 2 .
[0055] Example 3
[0056] According to Example 1, a bismuth-based catalyst r-Bi-MOF was obtained by electrochemical reduction and reconstruction, with a loading of 0.3~0.6 mg / cm³ on a carbon fiber substrate. 2 The carbon paper has an area of 6 cm². 2 The precursor weight was 6 mg, the total weight was 70.31 mg, and the total weight after electrochemical reconstruction was 66.54 mg. The calculated bismuth-based catalyst loading was 0.372 mg / cm³. 2 .
[0057] Example 4
[0058] Product selectivity test of the electrochemically reconstructed bismuth-based molecular catalyst in the electrocatalytic reduction of oxalic acid to glyoxylic acid; the bismuth-based catalyst r-Bi-MOF, namely the electrochemically reconstructed bismuth-based molecular catalyst obtained in Example 2, was tested under the following conditions for the electrocatalytic reduction of oxalic acid to glyoxylic acid:
[0059] In the H-type cell system, a Nafion 115 membrane was used as the ion exchange membrane, and the electrochemically reconstructed bismuth-based molecular catalyst, platinum electrode, and silver / silver chloride electrode obtained in Example 2 were used as the working electrode, counter electrode, and reference electrode, respectively. For the cathode catalytic reaction, 1.5 mol / L oxalic acid was used as the electrolyte, and 1 mol / L H₂SO₄ was used as the anode.
[0060] A constant potential test was conducted. The potential was set to -1.0V relative to the standard hydrogen electrode, and a constant current test was performed for 1 hour. Argon gas was introduced into the cathode electrolyte to purge the cathode air, and the oxygen generated at the anode during the reaction was released into the air. The hydrogen content in the cathode catalytic products was monitored online using gas chromatography, and the liquid products were analyzed using nuclear magnetic resonance spectroscopy.
[0061] After the test was completed, the total current was set to -1.2, -1.4, -1.6, -1.8 and -2.0 V relative to the standard hydrogen electrode in sequence, while keeping other conditions unchanged.
[0062] Meanwhile, a bismuth-based catalyst (with the same loading) without corresponding ligand modification structure was prepared under alkaline conditions. This catalyst mainly consisted of bismuth nanoparticles and lacked ligands (the precursor was uniformly sprayed onto carbon paper and then reduced in 1M KOH at a reduction voltage of -1.0 V to -1.2 V relative to the standard hydrogen electrode). It was compared with the electrochemically reconstructed bismuth-based catalyst r-Bi-MOF under the same conditions. The Faradaic efficiencies of the two catalysts in the electrocatalytic preparation of glyoxylic acid from oxalic acid are shown in [Figure / Reference]. Figure 4 The current density of glyoxylic acid is shown in [reference needed]. Figure 5 .
[0063] Figure 4 , Figure 5 This indicates that the ligand-modified catalyst obtained after reconstruction exhibits significantly better performance than the catalyst without corresponding ligand-modified structures, reflecting the role of the ligand-modified structure obtained through electrochemical reconstruction. The catalyst described in this application currently demonstrates performance comparable to commonly used Pb-based catalysts in the reduction of oxalic acid to glyoxylic acid. Compared to other commercially available metal catalysts, this catalyst shows better performance in the electrocatalytic reduction of oxalic acid to glyoxylic acid.
[0064] Example 5
[0065] Set the constant current density to 200 mA / cm 2 Electrolysis was performed to test the cycle stability of the bismuth-based catalyst r-Bi-MOF, i.e., the electrochemically reconstructed bismuth-based catalyst in Example 2, for the electrocatalytic reduction of oxalic acid to glyoxylic acid.
[0066] Under the reaction conditions of Example 4, a constant current density test was conducted. The constant current density was set to 200 mA / cm². 2 Constant current electrolysis for 3 hours, cyclically 40 times, the resulting glyoxylic acid Faraday efficiency and selectivity are shown in [see figure]. Figure 6 . Figure 6 The graph shows the catalytic cycle performance. The performance can be maintained after 120 hours of cycling, reflecting the good stability of the catalyst.
[0067] Comparative Example 1
[0068] 10 mg of bismuth nitrate was dissolved in 100 mL of 0.5 M nitric acid solution, and the carbon fiber substrate was immersed in the solution. The substrate was reduced for 30 min at -1.2 V relative to the standard hydrogen electrode to obtain the electrodeposited bismuth catalyst.
[0069] The obtained electrodeposited bismuth catalyst was subjected to the conditions of Example 4, with the addition of BTC (bis(2,2,2-trifluoroethyl) carbonate) to the cathode electrolyte to eliminate the influence of ligands. A constant current test was performed for 1 hour at a potential of -1.0 V relative to the standard hydrogen electrode. Argon gas was introduced into the cathode electrolyte to purge the cathode air, and oxygen generated at the anode during the reaction was released into the air. The liquid products were analyzed using nuclear magnetic resonance spectroscopy. After the test, the total current was sequentially set to -1.2, -1.4, -1.6, -1.8, and -2.0 V relative to the standard hydrogen electrode, while keeping other conditions unchanged. The Faraday efficiency of the catalyst for the electrocatalytic preparation of glyoxylic acid from oxalic acid is shown in [reference needed]. Figure 7 Its Faraday efficiency is below 80%, which is far inferior to that of r-Bi-MOF obtained by electrochemical reconstruction.
[0070] As can be seen from the above embodiments, the embodiments of the present invention mainly obtain bismuth-based molecular catalysts through electrochemical reconstruction. When used for the electrocatalytic reduction of oxalic acid to glyoxylic acid, it can improve the current density and Faradaic efficiency in the electrocatalytic reduction of oxalic acid to glyoxylic acid, thus improving the catalyst's reactivity and selectivity. Furthermore, the bismuth-based molecular catalysts described herein exhibit low toxicity. The preparation method of the bismuth-based molecular catalysts provided by the present invention is simple, easy to synthesize in large quantities, and inexpensive.
[0071] 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. An electrochemically reconstructed bismuth-based molecular catalyst, characterized in that, It includes a conductive substrate with a porous structure, and a bismuth-containing material loaded on the conductive substrate; The bismuth-containing material includes: modified bismuth substances formed by electrochemical reduction and reconstruction of metallic bismuth organic framework molecules under acidic conditions.
2. The bismuth-based molecular catalyst according to claim 1, characterized in that, The conductive substrate is a carbon fiber substrate; the loading of the modified bismuth material in the bismuth-based molecular catalyst is 0.2~0.8 mg / cm³. 2 .
3. A method for preparing an electrochemically reconstructed bismuth-based molecular catalyst, characterized in that, Includes the following steps: S1. Provide bismuth-organic framework materials; S2. Using the aforementioned bismuth organic framework material as a precursor, a dispersion is obtained by mixing it with a binder and a solvent, and then coated onto a conductive substrate. S3. The conductive substrate coated with the dispersion is electroreduced under acidic conditions to obtain an electrochemically reconstructed bismuth-based molecular catalyst.
4. The preparation method according to claim 3, characterized in that, The bismuth-metallic organic framework material is obtained by dissolving pyromellitic acid and bismuth nitrate in methanol solution under stirring conditions to obtain a mixed solution; the mixed solution is then heated to react, thus obtaining the final product.
5. The preparation method according to claim 4, characterized in that, The molar ratio of bismuth nitrate to trimesic acid is 0.8~1.2:20; the heating reaction temperature is 110~130℃, and the reaction time is 20~24h.
6. The preparation method according to any one of claims 3-5, characterized in that, The adhesive is Nafion solution, and the solvent is ethanol; the conductive substrate is carbon fiber paper.
7. The preparation method according to claim 6, characterized in that, The ratio of the precursor to the solvent is 3~9 mg: 1~2 mL.
8. The preparation method according to claim 6, characterized in that, The acidic conditions are achieved using an acidic solution with a pH not higher than 0.
7.
9. The preparation method according to claim 8, characterized in that, The electroreduction uses a relative standard hydrogen electrode with a voltage of -1.0V to -1.2V; the electroreduction time is 0.5 to 1 hour.
10. A method for electrocatalytic reduction of oxalic acid, characterized in that, The bismuth-based molecular catalyst is prepared by any one of the methods described in claims 1-2 or 3-9.