Multi-grain-boundary In2O3 catalyst and application thereof in co-production of formic acid by electrocatalytic CO2 reduction coupling biomass oxidation
A polycrystalline In2O3 catalyst was prepared by electrospinning-calcination. By combining it with a Co electrocatalyst and KOH solution, the grain boundary density was optimized, which solved the problems of high energy consumption and low efficiency of existing catalysts in the CO2 reduction coupled biomass oxidation co-production of formic acid system. This achieved low-energy consumption and high-yield CO2 and biomass co-production of formic acid conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-27
- Publication Date
- 2026-03-31
AI Technical Summary
Existing catalysts in electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid suffer from insufficient catalyst activity, support structure, and interface regulation, resulting in high system energy consumption and low efficiency, which limits their industrial application.
A polycrystalline In2O3 catalyst was prepared by electrospinning-calcination. Combined with a Co electrocatalyst and KOH solution, an electrolysis system was constructed. By controlling the calcination temperature to regulate the oxygen vacancy concentration and optimize the grain boundary density, a highly efficient coupling of CO2 reduction and biomass oxidation was achieved.
It significantly reduces system energy consumption, increases yield, and achieves efficient utilization of CO2 and biomass, with broad prospects for industrial applications.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalytic reduction of CO2, and in particular to a polycrystalline In2O3 catalyst and its application in electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid. Background Technology
[0002] With the rapid development of modern industry and economy, human society's demand for energy continues to rise. This over-reliance not only exacerbates the risk of energy depletion but also leads to massive CO2 emissions, which in turn triggers a series of environmental problems such as global warming. Electrocatalytic CO2 reduction reaction, as a highly promising carbon-negative technology, has received widespread attention in recent years. However, traditional CO2RR systems typically rely on the oxygen evolution reaction (OER) at the anode as a pairing reaction. This process is not only kineticly slow (high overpotential) but also produces O2 with low economic value, severely restricting the improvement of system energy efficiency and economy.
[0003] In recent years, biomass-derived molecular oxidation reactions (BERs) have been considered an ideal alternative to OERs due to their low thermodynamic potential (typically <1.0 V vs. RHE), diverse products (such as formic acid, gluconic acid, and lactic acid), and high added value. Formic acid, in particular, has attracted significant attention due to its broad application prospects in fuel cells, hydrogen storage, and chemical synthesis. Therefore, in CO2RR formic acid production systems, replacing OERs with glucose oxidation formic acid production and constructing a coupled CO2RR and biomass oxidation formic acid co-production system can reduce energy consumption and improve economic efficiency.
[0004] Although biomass oxidation is considered an ideal alternative anode, existing catalysts have not been optimized for this type of reaction, particularly in terms of catalyst activity, support structure, and interface control. This has hindered the efficient operation and industrial application of CO2 reduction coupled with biomass oxidation systems. Therefore, developing suitable anode catalysts and constructing low-energy, continuous, and high-yield CO2RR coupled with biomass oxidation systems to achieve efficient utilization of CO2 and biomass has broad industrial application prospects. While existing technologies, such as "Efficient Electrochemical Reduction of CO2 to HCOOH over Sub-2 nm SnO2 Quantum Wires with Exposed Grain Boundaries" (Subiao Liu, Jing Xiao, et al., Angew. Chem. Int. Ed. 10.1002 / anie.201903613), disclose the hydrothermal synthesis of sub-2 nm SnO2 quantum wires for the electrochemical reduction of CO2 to prepare HCOOH, [the remaining text is incomplete and requires further context]. It forms a multi-grain boundary structure by relying on the aggregation and coupling of quantum dots through the path of "quantum dot → quantum dot connection → quantum wire". However, this method focuses on the self-assembly connection of quantum dots to form grain boundaries and does not establish a direct relationship between temperature and grain boundary density. Summary of the Invention
[0005] To address the aforementioned limitations of existing technologies, the present invention aims to provide a polycrystalline In₂O₃ catalyst and its application in the electrocatalytic CO₂ reduction coupled with biomass oxidation to co-produce formic acid. This invention employs an electrospinning-calcination method to prepare a polycrystalline In₂O₃ catalyst, which is then used as the cathode catalyst. Sulfuric acid is used to treat the biomass feedstock to obtain an organic electrolyte, which is then mixed with KOH solution to serve as the anolyte. A Co electrocatalyst is used as the anolyte, and KOH solution as the cathode electrolyte. CO₂ gas is then introduced into the cathode side for electrolysis. After electrolysis, the resulting product undergoes phosphoric acidification and crystallization to obtain high-purity formic acid. This invention utilizes the polycrystalline In₂O₃ catalyst to improve cathode efficiency and reduce the full-cell operating voltage of the coupled system, thereby driving the efficient oxidation of the anode biomass under mild conditions. Ultimately, this achieves efficient coupling and synergistic enhancement of the conversion of cathode CO₂ reduction and anode biomass oxidation to formic acid. The method of this invention can significantly reduce cell voltage and energy consumption, simultaneously increase system yield, and achieve efficient utilization of CO₂ and biomass, possessing broad industrial application prospects.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a polygrain boundary In2O3 catalyst, which is prepared by the following method: (1) Polyacrylonitrile and polyvinylpyrrolidone were mixed and dissolved in N,N-dimethylformamide to obtain solution A; indium nitrate hydrate was dissolved in N,N-dimethylformamide and stirred to obtain solution B; solution A and solution B were mixed to obtain precursor solution; the precursor solution was electrospun and dried to obtain nanofiber membrane; the nanofiber membrane was calcined in air atmosphere to obtain In2O3 catalyst; (2) Place the In2O3 catalyst under an inert atmosphere and calcine it at 250-350℃ for 1.5-2.5h to obtain a polycrystalline In2O3 catalyst.
[0007] Preferably, in step (1), the ratio of polyacrylonitrile, polyvinylpyrrolidone and N,N-dimethylformamide in solution A is (1.0-1.5) g: (0.15-0.25) g: 10 mL.
[0008] Preferably, in step (1), the ratio of indium nitrate hydrate to N,N-dimethylformamide in solution B is (1.5-2.5) mmol: 5 mL.
[0009] Preferably, in step (1), the stirring time is 4-6 hours.
[0010] Preferably, in step (1), the ratio of the amount of polyacrylonitrile in solution A to the amount of indium nitrate hydrate in solution B is (1.0-1.5) g: (1.5-2.5) mmol.
[0011] Preferably, in step (1), the distance between the needle and the collector during electrospinning is 8-12cm and the working voltage is 11-12kV.
[0012] Preferably, in step (1), the drying method is vacuum drying, and the drying temperature is 50-70℃.
[0013] Preferably, in step (1), the calcination temperature is 450-550℃ and the calcination time is 1.5-2.5h.
[0014] Preferably, in step (2), the inert atmosphere is an argon atmosphere.
[0015] In a second aspect, the present invention provides the application of the above-mentioned polycrystalline In2O3 catalyst in the electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid.
[0016] A third aspect of the present invention provides a method for electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid, comprising the following steps: (i) After mixing biomass powder and sulfuric acid, heat to carry out hydrolysis reaction. After the reaction, filter and collect the filtrate. Add a precipitant to the filtrate to adjust the pH. After precipitation is complete, centrifuge and collect the supernatant to obtain organic electrolyte. Add KOH solution to the organic electrolyte and mix to obtain a mixed solution. (ii) An electrolysis system is constructed by using the mixed solution as the anolyte, KOH solution as the cathode electrolyte, Co electrocatalyst as the anolyte, and the above-mentioned polycrystalline In2O3 catalyst as the cathode catalyst; CO2 gas is introduced into the cathode for electrolysis; after electrolysis, the anolyte and cathode electrolyte are collected and combined to obtain an electrolyte containing potassium formate. (iii) After the electrolyte containing potassium formate is concentrated, pH adjusted and acidified, it is crystallized, filtered and washed to obtain formic acid.
[0017] Preferably, in step (i), the biomass powder is one or more of corn stalks, wheat stalks, and rice straw, with a particle size ≤0.5mm.
[0018] Preferably, in step (i), the concentration of sulfuric acid is 1-20 wt%, and the ratio of biomass powder to sulfuric acid is 1:(20-30).
[0019] Preferably, in step (i), the heating temperature is 80-200℃; during the hydrolysis process, the rotation speed is 200-800 rpm and the time is 1-5h.
[0020] Preferably, in step (i), the precipitant is a saturated solution of Ca(OH)2 or Ba(OH)2, with the pH adjusted to 6.5-7.0.
[0021] Preferably, in step (i), the concentration of the KOH solution is 0.8-1.2M, the volume ratio of the organic electrolyte to the KOH solution is 1:(1-3), and the pH of the mixture is 12-14.
[0022] Preferably, in step (ii), the concentration of the KOH solution is 1-2M.
[0023] Preferably, in step (ii), the Co electrocatalyst is prepared by the following method: A 0.1-0.2 M Co(NO3)3·9H2O solution was used as the electrodeposition solution. Nickel foam was placed in the electrodeposition solution for electrodeposition to obtain a Co electrocatalyst.
[0024] Furthermore, during the electrodeposition process, a saturated calomel electrode was used as the reference electrode, with a deposition potential of -1.5 to -0.5V and a deposition time of 250-350s.
[0025] Preferably, in step (ii), the cathode catalyst needs to be loaded onto the gas diffusion electrode at a loading of 0.2-2 mg / cm³. 2 .
[0026] Preferably, in step (ii), the CO2 gas introduction rate is 15-25 mL / min.
[0027] Preferably, in step (ii), the current density during electrolysis is -50 to -1000 mA / cm². 2 .
[0028] Preferably, in step (iii), the specific operation of pH adjustment and acidification is as follows: add 80%-90% phosphoric acid by mass to the concentrated solution to adjust the pH to 1.5-2.0 for acidification reaction.
[0029] Preferably, in step (iii), the crystallization temperature is 0-5℃.
[0030] The beneficial effects of this invention are: This invention employs an electrospinning-calcination method to prepare a polycrystalline In2O3 catalyst, which is used as the cathode catalyst. An organic electrolyte is obtained by hydrolyzing biomass feedstock with sulfuric acid, and this electrolyte is mixed with KOH solution to serve as the anolyte. A Co electrocatalyst is obtained by electrodepositing Co onto nickel foam, which is used as the anolyte, and the KOH solution is used as the cathode electrolyte. CO2 gas is then introduced through the cathode side for electrolysis. After electrolysis, the resulting formic acid is obtained through phosphoric acid treatment and crystallization, yielding high-purity formic acid.
[0031] The method of this invention can significantly reduce tank pressure and energy consumption, simultaneously improve system yield, and achieve efficient utilization of CO2 and biomass, with broad industrial application prospects. Attached Figure Description
[0032] Figure 1 Flowchart of the electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid; Figure 2 In Application Example 1, the characteristic spectrum of the prepared formic acid in high performance liquid chromatography (a), the Faraday efficiency spectrum of formic acid production at the cathode (b), and the Faraday efficiency spectrum of formic acid production at the anode (c) are shown. Figure 3 In Application Example 2, the characteristic spectrum of the prepared formic acid in high performance liquid chromatography (a), the Faraday efficiency spectrum of formic acid production at the cathode (b), and the Faraday efficiency spectrum of formic acid production at the anode (c) are shown. Figure 4 In Application Example 3, the characteristic spectrum of the prepared formic acid in high performance liquid chromatography (a) and the Faraday efficiency diagram of formic acid production at the cathode (b) are shown. Figure 5In Application Example 4, the characteristic spectrum of the formic acid obtained in high performance liquid chromatography (a) and the Faraday efficiency diagram of formic acid production at the cathode (b) are shown. Figure 6 In Application Example 5, the characteristic spectrum of the formic acid obtained in high performance liquid chromatography (a) and the Faraday efficiency diagram of formic acid production at the cathode (b) are shown. Figure 7 Electron paramagnetic resonance (EPR) images of the catalysts (In2O3-300, In2O3-200 and In2O3-400) prepared in Example 1 and Comparative Examples 1-2; Figure 8 High-resolution transmission electron microscope (HRTEM) image of the polygrain boundary In2O3 catalyst In2O3-300 prepared in Example 1; Figure 9 Nuclear magnetic resonance spectrum of formic acid prepared using polygrain boundary In2O3-300 catalyst in Experimental Example 2; Figure 10 : High performance liquid chromatogram of formic acid prepared using polycrystalline In2O3-300 catalyst in Experimental Example 2; Figure 11 Example 2: Faraday efficiency of the catalyst In2O3-200 prepared in Comparative Example 1 at different current densities for the production of formic acid at the cathode. Figure 12 Example 2: The Faraday efficiency of the In2O3-300 catalyst prepared in Example 1 at different current densities for the production of formic acid at the cathode. Figure 13 Example 2: The Faraday efficiency of the formic acid production at the cathode of the catalyst In2O3-200 prepared in Comparative Example 2 under different current densities. Detailed Implementation
[0033] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0034] Although existing technologies disclose the electrocatalytic coupling of CO2 with biomass oxidation to produce formic acid, no suitable catalysts have been designed for this coupling system. Significant deficiencies exist in catalyst activity, support structure, and interface regulation, hindering the efficient operation and industrial application of the CO2 reduction-coupled biomass oxidation system.
[0035] Based on this, the present invention provides a polycrystalline In2O3 catalyst, which is prepared by electrospinning combined with calcination. Specifically, indium nitrate hydrate, polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) are used as raw materials, and the catalyst is obtained by electrospinning and calcination under a nitrogen atmosphere. The In2O3 catalyst is then placed under an inert atmosphere and calcined at 250-350°C to prepare the polycrystalline In2O3 catalyst.
[0036] This patent innovatively utilizes oxygen vacancies (O2) V Using calcination temperature as a key link, this invention quantitatively correlates calcination temperature with the grain boundary density of the catalyst, thereby systematically revealing the influence mechanism of grain boundary density differences on the performance of multi-grain boundary In2O3 catalysts under temperature control. Specifically, this invention controls the oxygen vacancy (Ov) concentration by controlling the calcination temperature of the In2O3 catalyst under an inert atmosphere, resulting in a catalyst exhibiting high-density grain boundaries. A moderate concentration of Ov... V It can suppress grain coarsening, promote heterogeneous nucleation, and form abundant grain boundaries (GBs). Grain boundaries are regions of atomic mismatch in the crystal structure, containing a large number of unsaturated atoms and strain. These characteristics create a unique local electronic structure, providing high active sites and thus improving catalytic performance. When the calcination temperature is too low, O... V The concentration is also too low, resulting in insufficient atomic diffusion and migration energy, which reduces the driving force for grain nucleation and slows the nucleation rate, thus leading to a significant decrease in grain boundary density; when the calcination temperature is too high, O V Excessive concentration increases the strain energy accumulated within the crystal lattice, leading to abnormal grain coarsening and a sharp decrease in the number of grain boundaries.
[0037] Then, an electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid was constructed using a poly-grain-bound In₂O₃ catalyst. The high-density grain boundaries of the poly-grain-bound In₂O₃ catalyst endow it with a unique electronic structure, enabling it to optimize key intermediates. The adsorption of OCHO acts as an electron-rich region, accelerating charge transport. This enables the reduction of CO2 to formic acid at the cathode with low overpotential, high selectivity, and high activity. Simultaneously, the improved cathode efficiency significantly reduces the full-cell operating voltage of the coupled system, thereby driving efficient oxidation of the anode biomass under mild conditions. Ultimately, this system achieves highly efficient coupling and synergistic enhancement of cathode CO2 reduction and anode biomass oxidation to formic acid.
[0038] like Figure 1As shown, an organic electrolyte containing glucose was obtained by acidifying and hydrolyzing biomass raw materials with sulfuric acid. This electrolyte was then mixed with KOH solution and used as the anolyte and the KOH solution as the catholyte. The polycrystalline In2O3 catalyst was used as the catholy catalyst and the Co catalyst obtained by electrodeposition of Co from nickel foam was used as the anolyte. This constructed an electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid. The low-energy-consumption and high-value co-conversion of the coupled system was achieved through CO2 reduction and glucose oxidation.
[0039] During electrolysis, CO2 is reduced to formic acid via two-electron reduction at the cathode according to formula (I); CO2 + 2H⁺ + 2e⁻ → HCOOH (Formula I); The anode oxidizes glucose to formic acid according to formula (II); C6H 12 O6+8OH⁻→6HCOO⁻ +2H2O +6e⁻ Formula (II).
[0040] After electrolysis, the cathode electrolyte and anolyte are collected and combined to obtain an electrolyte containing potassium formate; after concentration, phosphoric acid acidification, crystallization, filtration and washing, pure formic acid is obtained.
[0041] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.
[0042] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels.
[0043] Example 1: Preparation of polygrain boundary In2O3 catalyst (1) Mix 1.2 g polyacrylonitrile and 0.2 g polyvinylpyrrolidone, dissolve them in 10 mL of N,N-dimethylformamide, and stir magnetically for 5 h to ensure complete dissolution, to obtain solution A; dissolve 2.0 mmol indium nitrate hydrate in 5 mL of N,N-dimethylformamide, stir for 5 h to obtain solution B; mix solution A and solution B, stir overnight to mix evenly, remove air bubbles, and obtain precursor solution; The precursor solution was transferred into a syringe, and the distance between the needle and the collector was fixed at 10 cm. Electrospinning was performed at a working voltage of 11 kV to 12 kV to collect nanofibers on an aluminum foil. After electrospinning, the aluminum foil was removed, and the nanofibers were dried under vacuum at 60 °C to obtain a nanofiber membrane. The nanofiber membrane was then placed in an air atmosphere and calcined at 500 °C for 2 h to obtain an In2O3 catalyst. (2) The In2O3 catalyst was placed under an argon atmosphere and calcined at 300°C for 2 hours to obtain a polycrystalline In2O3 catalyst, denoted as In2O3-300.
[0044] Example 2: Preparation of polygrain boundary In2O3 catalyst (1) Mix 1.0 g polyacrylonitrile and 0.15 g polyvinylpyrrolidone, dissolve them in 10 mL N,N-dimethylformamide, and stir magnetically for 5 h to ensure complete dissolution, to obtain solution A; dissolve 1.5 mmol indium nitrate hydrate in 5 mL N,N-dimethylformamide, stir for 4 h to obtain solution B; mix solution A and solution B, stir overnight to mix evenly, remove air bubbles, and obtain precursor solution; The precursor solution was transferred into a syringe, and the distance between the needle and the collector was fixed at 8 cm. Electrospinning was performed at a working voltage of 11 kV to 12 kV to collect nanofibers on an aluminum foil. After electrospinning, the aluminum foil was removed, and the nanofibers were vacuum dried at 50 °C to obtain a nanofiber membrane. The nanofiber membrane was then placed in an air atmosphere and calcined at 450 °C for 1.5 h to obtain an In2O3 catalyst. (2) The In2O3 catalyst was placed under an argon atmosphere and calcined at 250°C for 1.5 h to obtain a polycrystalline In2O3 catalyst.
[0045] Example 3: Preparation of polygrain boundary In2O3 catalyst (1) Mix 1.5 g polyacrylonitrile and 0.25 g polyvinylpyrrolidone, dissolve them in 10 mL N,N-dimethylformamide, and stir magnetically for 5 h to ensure complete dissolution, to obtain solution A; dissolve 2.5 mmol indium nitrate hydrate in 5 mL N,N-dimethylformamide, stir for 6 h to obtain solution B; mix solution A and solution B, stir overnight to mix evenly, remove air bubbles, and obtain precursor solution; The precursor solution was transferred into a syringe, and the distance between the needle and the collector was fixed at 12 cm. Electrospinning was performed at a working voltage of 11 kV to 12 kV to collect nanofibers on an aluminum foil. After electrospinning, the aluminum foil was removed, and the nanofibers were vacuum dried at 70 °C to obtain a nanofiber membrane. The nanofiber membrane was then placed in an air atmosphere and calcined at 550 °C for 2.5 h to obtain an In2O3 catalyst. (2) The In2O3 catalyst was placed under an argon atmosphere and calcined at 350°C for 2.5 h to obtain a polycrystalline In2O3 catalyst.
[0046] Comparative Example 1: The difference between this comparative example and Example 1 is that in step (2), the calcination temperature is 200°C, and the catalyst obtained is denoted as In2O3-200.
[0047] Comparative Example 2: The difference between this comparative example and Example 1 is that in step (2), the calcination temperature is 400℃, and the catalyst obtained is denoted as In2O3-400.
[0048] Application Example 1: A method for co-producing formic acid by electrocatalytic CO2 reduction coupled with biomass oxidation. (i) Mix corn stalk powder with a particle size ≤0.5 mm and sulfuric acid with a concentration of 8 wt% at a mass ratio of 1:20, heat to 100 °C, and react at 200 rpm for 5 h to fully hydrolyze hemicellulose and cellulose into monosaccharides, etc., and quench in water to room temperature to terminate hydrolysis; then filter to remove insoluble lignin and large particle residues, collect the filtrate, add saturated Ba(OH)2 solution dropwise to the filtrate while stirring until the pH reaches 6.8, and after precipitation is complete, centrifuge at 7000 rpm for 10 min, collect the supernatant to obtain organic electrolyte; mix organic electrolyte and 1M KOH solution at a volume ratio of 1:1 to obtain a mixture with a pH of 12.5; (ii) Use 0.15M Co(NO3)3·9H2O solution as electrodeposition solution; soak nickel foam in 2M hydrochloric acid and anhydrous ethanol in sequence and sonicate for 2h to remove surface impurities, and then clean the surface with deionized water; place the cleaned nickel foam in the electrodeposition solution and deposit it for 300s at a deposition potential of -1V (the reference electrode is a saturated calomel electrode) to obtain Co electrocatalyst; Electrolysis was carried out in a two-chamber electrolytic cell containing an ion-exchange membrane. The mixture obtained in step (i) was used as the anolyte and 1M KOH solution as the catholyte. The polygrain-bound In₂O₃ catalyst prepared in Example 1 was used as the catholy catalyst and Co electrocatalyst was used as the anolyte to construct the electrolysis system. The polygrain-bound In₂O₃ catalyst was loaded onto the gas diffusion electrode at a loading of 0.2 mg / cm³. 2 CO2 gas is introduced into the cathode side at a rate of 20 mL / min, with an A / cm range of -50 to -250 mA / cm. 2 Electrolysis was carried out at a current density of ; after electrolysis, the cathode electrolyte and the anolyte were collected and combined to obtain an electrolyte containing potassium formate; (iii) After the electrolyte containing potassium formate is concentrated under reduced pressure, 85% phosphoric acid is added to adjust the pH to 2.0 for acidification reaction. After the reaction, the formic acid is obtained by cooling crystallization, filtration and washing.
[0049] The high-performance liquid chromatogram of formic acid prepared in this application example, and the Faradaic efficiency plots of formic acid production at the cathode and anode, are as follows: Figure 2 As shown in (a)-(c). By Figure 2 It can be seen that the Faraday efficiency of formic acid production at the cathode is 98%, and the Faraday efficiency of formic acid production at the anode is 97%.
[0050] Application Example 2: A method for co-producing formic acid by electrocatalytic CO2 reduction coupled with biomass oxidation. The difference between this application example and application example 1 is that in step (i), when corn stalks and sulfuric acid are mixed and hydrolyzed, the heating temperature is 130°C and the reaction time is 4 hours.
[0051] The high-performance liquid chromatogram of formic acid prepared in this application example, and the Faradaic efficiency plots of formic acid production at the cathode and anode, are as follows: Figure 3 As shown in (a)-(c). By Figure 3 It can be seen that the Faraday efficiency of formic acid production at the cathode is 96%, and the Faraday efficiency of formic acid production at the anode is 95%.
[0052] Application Example 3: A method for co-producing formic acid by electrocatalytic CO2 reduction coupled with biomass oxidation. The difference between this application example and application example 1 is that in step (i), when corn stalks and sulfuric acid are mixed and hydrolyzed, the concentration of sulfuric acid is 4 wt% and the reaction time is 4 h.
[0053] The high-performance liquid chromatogram of formic acid prepared in this application example and the Faraday efficiency graph of formic acid production at the cathode are shown below. Figure 4 As shown in (a)-(b). From Figure 4 It can be seen that the Faraday efficiency of formic acid production at the cathode is 94%.
[0054] Application Example 4: A method for co-producing formic acid by electrocatalytic CO2 reduction coupled with biomass oxidation. The difference between this application example and Application Example 1 is that in step (ii), the current density during electrolysis is -200 to -1000 mA / cm². 2 .
[0055] The high-performance liquid chromatogram of formic acid prepared in this application example and the Faraday efficiency graph of formic acid production at the cathode are shown below. Figure 5 As shown in (a)-(b). From Figure 5 It can be seen that the formic acid production efficiency at the cathode is as high as 93%, and the results at high current density also suggest the industrial feasibility of the system.
[0056] Application Example 5: A method for co-producing formic acid by electrocatalytic CO2 reduction coupled with biomass oxidation. The difference between this application example and application example 1 is that in step (ii), a 2M KOH solution is used as the cathode electrolyte.
[0057] The high-performance liquid chromatogram of formic acid prepared in this application example and the Faraday efficiency graph of formic acid production at the cathode are shown below. Figure 6 As shown in (a)-(b). From Figure 6 It can be seen that the Faraday efficiency of formic acid production at the cathode is as high as 92%.
[0058] Experimental Example 1: Electron paramagnetic resonance analysis was performed on the catalysts prepared in Example 1 and Comparative Examples 1-2, and the results are as follows: Figure 7 As shown. High-resolution transmission electron microscopy analysis was performed on the polygrainite In2O3 catalyst In2O3-300 prepared in Example 1, and the results are as follows. Figure 8 As shown.
[0059] In the EPR diagram ( Figure 7 A distinct signal can be observed (g = 2.003), characterized by electrons trapped in O. V The signal gradually strengthens with increasing calcination temperature. O at different calcination temperatures... V The change in concentration confirmed the preparation of O-rich materials by Ar atmosphere heat treatment. V The feasibility of In2O3.
[0060] HRTEM image (8) shows clear lattice fringes with a spacing of 0.27 nm, corresponding to the (101) plane of metallic In. More importantly, the In2O3-300 catalyst exhibits a high density of grain boundaries (yellow areas), a feature that is hardly observed in the other catalysts.
[0061] Experimental Example 2: The catalysts prepared in Example 1 and Comparative Examples 1-2 were used for electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid. The specific preparation method is as follows: (i) Mix corn stalk powder with a particle size ≤0.5 mm and sulfuric acid with a concentration of 8 wt% at a mass ratio of 1:25, heat to 140 °C, and react at 500 rpm for 3 h to fully hydrolyze hemicellulose and cellulose into monosaccharides, etc., and quench in water to room temperature to terminate hydrolysis; then filter to remove insoluble lignin and large particle residues, collect the filtrate, add saturated Ba(OH)2 solution dropwise to the filtrate while stirring until the pH reaches 6.8, and after precipitation is complete, centrifuge at 7000 rpm for 10 min, collect the supernatant to obtain organic electrolyte; mix organic electrolyte and 1M KOH solution at a volume ratio of 1:2 to obtain a mixed solution with a pH of 13; (ii) Use 0.2M Co(NO3)3·9H2O solution as electrodeposition solution; soak nickel foam in 2M hydrochloric acid and anhydrous ethanol in sequence and sonicate for 2h to remove surface impurities, and then clean the surface with deionized water; place the cleaned nickel foam in the electrodeposition solution and deposit it for 300s at a deposition potential of -1V (the reference electrode is a saturated calomel electrode) to obtain Co electrocatalyst; Electrolysis was carried out in a two-chamber electrolytic cell containing an ion-exchange membrane. The mixture obtained in step (i) was used as the anolyte and 1M KOH solution as the catholyte. The polygrain-bound In₂O₃ catalyst prepared in Example 1 was used as the catholy catalyst and Co electrocatalyst was used as the anolyte to construct the electrolysis system. The polygrain-bound In₂O₃ catalyst was loaded onto the gas diffusion electrode at a loading of 1.1 mg / cm³. 2 CO2 gas is introduced into the cathode side at a rate of 20 mL / min, with an A / cm range of -200 to -600 mA / cm. 2 Electrolysis was carried out at a current density of ; after electrolysis, the cathode electrolyte and the anolyte were collected and combined to obtain an electrolyte containing potassium formate; (iii) After the electrolyte containing potassium formate is concentrated under reduced pressure, 85% phosphoric acid is added to adjust the pH to 2.0 for acidification reaction. After the reaction, the formic acid is obtained by cooling crystallization, filtration and washing.
[0062] The nuclear magnetic resonance spectrum and high-performance liquid chromatography (HPLC) chromatogram of formic acid prepared using polycrystalline In₂O₃-300 catalyst are shown below. Figure 9 and Figure 10 As shown. Simultaneously, the performance of different catalysts was measured at -200 to -600 mA / cm². 2 The cathode formic acid production Faraday efficiency within the current range is shown in the following results. Figures 11-13 As shown.
[0063] Depend on Figure 11 It can be seen that when the catalyst In2O3-200 prepared in Comparative Example 1 is used for electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid, the effect is only achieved at -400 mA / cm². 2 and -500 mA / cm 2 At a current density of [value missing], the Faradaic efficiency for formic acid production at the cathode is ≥90%. Figure 12 It can be seen that when the catalyst In2O3-300 prepared in Example 1 is used for electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid, the efficiency is within the range of -200 to -500 mA / cm². 2 This wide current density range maintains a Faraday efficiency of over 90%. Figure 13 It can be seen that when the catalyst In2O3-400 prepared in Comparative Example 2 is used for electrocatalytic CO2 reduction coupled with biomass oxidation to co-produce formic acid, the performance is good in the range of -300 to -500 mA / cm². 2 At the specified current density, the faradaic efficiency for formic acid production at the cathode is ≥90%. Therefore, the polygrain-boundary In₂O₃ catalyst prepared in this invention can maintain high faradaic efficiency over a wide current density range.
[0064] Furthermore, the catalyst In2O3-300 prepared by this invention exhibits a performance of -400 mA / cm².2 At a current density of -500 mA / cm², the highest Faradaic efficiency for formic acid production at the cathode was 97%; the catalyst In₂O₃-200 prepared in Comparative Example 1 achieved a current density of -500 mA / cm². 2 At a current density of -300 mA / cm², the cathode exhibits the highest Faradaic efficiency for formic acid production, at only 91%; the catalyst In₂O₃-400 prepared in Comparative Example 2 achieves this efficiency at -300 mA / cm². 2 At the specified current density, the faradaic efficiency of formic acid production at the cathode is the highest, at only 92%. Therefore, the polycrystalline In₂O₃ catalyst prepared in this invention can improve the faradaic efficiency of formic acid production at the cathode.
[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A polycrystalline boundary In2O3 catalyst characterized in that, Prepared by the following method: (1) polyacrylonitrile, polyvinylpyrrolidone mixed after dissolving in N, N- dimethylformamide, get solution A; indium nitrate hydrate is dissolved in N, N- dimethylformamide, stirring, get solution B; Solution A and solution B are mixed, get precursor solution; The precursor solution is subjected to electrospinning treatment and dried to obtain a nanofiber membrane; the nanofiber membrane is placed in an air atmosphere and subjected to calcination treatment to obtain an In2O3 catalyst; (2) In2O3 catalyst is placed in an inert atmosphere, calcined at 250-350 ℃ for 1.5-2.5 h to obtain a polycrystalline In2O3 catalyst.
2. The polycrystalline boundary In203 catalyst of claim 1, wherein In step (1), in solution A, the liquid ratio of polyacrylonitrile, polyvinylpyrrolidone and N, N-dimethylformamide is (1.0-1.5) g: (0.15-0.25) g: 10 mL; In solution B, the liquid ratio of indium nitrate hydrate and N, N-dimethylformamide is (1.5-2.5) mmol: 5 mL; The addition amount ratio of polyacrylonitrile in solution A and indium nitrate hydrate in solution B is (1.0-1.5) g: (1.5-2.5) mmol.
3. The polycrystalline boundary In2O3 catalyst of claim 1, wherein In step (1), during electrospinning, the distance between the needle and the collector is 8-12 cm, and the working voltage is 11-12 kV; The calcination temperature is 450-550 ℃, and the calcination time is 1.5-2.5 h.
4. The polycrystalline boundary In2O3 catalyst of claim 1, wherein In step (2), the inert atmosphere is an argon atmosphere.
5. The polycrystalline In2O3 catalyst of claim 1 is used in the electrocatalytic reduction of CO2 coupled with biomass oxidation to co-produce formic acid.
6. A method of electrocatalytic CO2 reduction coupled with biomass oxidation co-producing formic acid, characterized in that, Comprising the following steps: (i) Biomass powder and sulfuric acid are mixed and heated to perform hydrolysis reaction, after reaction, filtration is performed, the filtrate is collected, a precipitant is added to the filtrate to adjust pH, after complete precipitation, centrifugation is performed and the supernatant is collected to obtain an organic electrolyte, KOH solution is added to the organic electrolyte and mixed to obtain a mixed solution; (ii) The mixed solution is used as an anode electrolyte, KOH solution is used as a cathode electrolyte, Co electrocatalyst is used as an anode catalyst, and the above polycrystalline In2O3 catalyst is used as a cathode catalyst to construct an electrolysis system; CO2 gas is introduced into the cathode to perform electrolysis, after electrolysis, the anode electrolyte and the cathode electrolyte are collected and combined to obtain an electrolyte containing potassium formate; (iii) The electrolyte containing potassium formate is concentrated, acidified by adjusting pH, and then crystallized, filtered and washed to obtain formic acid.
7. The method of electrocatalytic CO2 reduction coupled with biomass oxidation co-producing formic acid according to claim 6, wherein, In step (i), the biomass powder is one or more of corn straw, wheat straw and rice straw; the concentration of sulfuric acid is 1-20 wt%, and the liquid ratio of biomass powder and sulfuric acid is 1: (20-30); The heating temperature is 80-200 ℃, during hydrolysis, the rotation speed is 200-800 rpm, and the time is 1-5 h; The precipitant is a saturated Ca(OH)2 solution or a saturated Ba(OH)2 solution, and the pH is adjusted to 6.5-7.
0. The concentration of KOH solution is 0.8-1.2 M, the volume ratio of organic electrolyte and KOH solution is 1: (1-3), and the pH of the mixed solution is 12-14.
8. The method of electrocatalytic CO2 reduction coupled with biomass oxidation co-producing formic acid according to claim 6, wherein, In step (ii), the Co electrocatalyst is prepared by the following method: Co(NO3)3·9H2O solution with a concentration of 0.1-0.2 M is used as the electrodeposition solution; the foamed nickel is placed in the electrodeposition solution to perform electrodeposition, thereby obtaining a Co electrocatalyst; During the electrodeposition process, a saturated calomel electrode is used as a reference electrode, the deposition potential is-1.5~-0.5 V, and the deposition time is 250-350 s.
9. The method of electrocatalytic CO2 reduction coupled with biomass oxidation co-producing formic acid of claim 6, wherein, The concentration of the KOH solution is 1-2 M, the flow rate of the CO2 gas is 15-25 mL / min, and the current density during electrolysis is -50 ~ -1000 mA / cm 2 .
10. The method of electrocatalytic CO2 reduction coupled with biomass oxidation co-producing formic acid of claim 6, wherein, In step (iii), the specific operation of pH adjustment and acidification is that 80-90% phosphoric acid by mass fraction is added to the concentrated solution to adjust the pH to 1.5-2.0; the crystallization temperature is 0-5 ℃.