A photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction, its preparation method and application
By constructing a Cu2O@Bi2O3/Si pnp junction photocathode, the defects of Bi2O3 and Cu2O in photoelectrocatalytic CO2 reduction were solved, achieving efficient CO2 reduction to formic acid and improving photoelectrocatalytic performance and CO2 adsorption capacity.
Patent Information
- Application Number
- CN202410967218.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-18
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2044-07-18
AI Technical Summary
Bi2O3 materials suffer from defects such as wide bandgap, low carrier mobility and high overpotential in photoelectrocatalytic CO2 reduction, which limits their application. In addition, Cu2O, as an active site, is severely photocorroded, affecting its CO2 reduction efficiency.
A Cu2O@Bi2O3/Si pnp junction photocathode was constructed by hydrothermal and static Czochralski methods. By combining Cu2O and Bi2O3 heterojunctions, the electron transfer rate and CO2 adsorption capacity were improved, and electron-rich sites were formed to promote CO2 reduction.
It significantly improved the photoelectrocatalytic CO2 reduction performance, enhanced the CO2 enrichment capacity and reduction efficiency, reduced the onset potential, and achieved the ability to efficiently reduce CO2 to formic acid.
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Figure CN118957654B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalysis technology, and relates to a photocathode, its preparation method and application, specifically to a Bi2O3@Cu2O / Si photocathode for photocatalytic carbon dioxide reduction, its preparation method and application. Background Technology
[0002] Photoelectrocatalysis effectively combines the advantages of photocatalysis and electrocatalysis. Using a semiconductor as the photocathode or photoanode, electron-hole pairs are generated at the semiconductor electrode under illumination and applied to the CO2 reduction reaction. Simultaneously, an additional negative potential is added to the system (which can be provided by clean energy sources such as wind and solar power). This effectively separates the photogenerated electron-hole pairs in the semiconductor, promoting the reaction, and also allows for effective control of the reaction products by altering the potential. Therefore, photoelectrocatalysis is an effective way to utilize solar energy, reducing carbon dioxide in the air into more economically valuable liquid fuels such as formic acid, acetic acid, and ethanol.
[0003] Currently, bismuth-based materials have been proven to be ideal materials for the reduction of formic acid from CO2 due to their flexible and varied coordination structures and low HER activity. In particular, Bi2O3 derived from bismuth-based metal-organic frameworks (Bi-MOFs) not only retains highly dispersed active sites, but the derived carbon substrate also alleviates the intrinsic low conductivity of Bi2O3. However, the inherent defects of Bi2O3, such as wide bandgap, low carrier mobility, and high overpotential, have not been effectively overcome, hindering its application in PEC-CO2RR. Therefore, it is urgent to construct reasonable heterojunctions to improve the photoelectric properties of Bi2O3. Cu2O, with its narrow bandgap and high carrier density, is an excellent photoelectron donor, but when used as an active site, its diverse crystal planes lead to numerous reduction products, and Cu2O is easily reduced by untransferred photoelectrons, resulting in severe photocorrosion. Inspired by this, if a reasonable close-packed pn heterojunction is constructed, utilizing the rapid electron transfer mechanism at the contact interface, the transfer of Cu2O photoelectrons to Bi2O3 for CO2 reduction can be accelerated. Simultaneously, by utilizing the atomic localization effect at the pn junction interface to construct electron-rich sites, it is possible to simultaneously improve the photoelectric performance of the catalyst and its CO2 adsorption capacity. Summary of the Invention
[0004] To address the low performance and low adsorption capacity of current photocathodes for photoelectrocatalytic CO2 reduction, this invention provides a Cu2O@Bi2O3 / Si photocathode derived from a bismuth-based metal-organic framework material, which enhances CO2 adsorption performance and improves CO2 photoelectrochemical reduction. This photocathode exhibits stronger carbon dioxide enrichment capacity, accelerates the adsorption and activation of carbon dioxide molecules, stabilizes key intermediates in the CO2 reduction process, and possesses excellent photoelectrochemical properties, showing promising application prospects in the field of photoelectrocatalytic CO2 reduction.
[0005] The objective of this invention is achieved by at least one of the following technical solutions.
[0006] A method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction is disclosed, which is prepared by hydrothermal method and carbonized in an inert atmosphere.
[0007] This invention discloses a method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction, the specific preparation steps of which are as follows:
[0008] (1) Preparation of bismuth-based metal-organic framework material Bi-MOF as a precursor: The active metal source and organometallic ligand 1,3,5-pyromellitic acid were added to the organic solution and stirred continuously until completely dissolved. The resulting precursor solution was transferred to a polytetrafluoroethylene liner and placed in a stainless steel reactor under an electric heating oven for reaction. After the reaction was completed, the reactor was removed and cooled at room temperature. The product after the reaction was repeatedly washed with deionized water, dried, crushed and sieved to obtain bismuth-based metal-organic framework material.
[0009] (2) Disperse the precursor material obtained in step (1) in deionized water, slowly add the metal source solution, and after stirring, centrifuge to obtain the precipitate. Wash repeatedly with deionized water and dry to obtain the metal-modified bismuth-based metal-organic framework material; the metal source contains at least one element of Bi and Cu.
[0010] (3) The metal-modified bismuth-based metal-organic framework material obtained in step (2) is carbonized in an inert gas atmosphere to obtain Cu2O@Bi2O3 catalyst;
[0011] (4) Prepare a Cu2O@Bi2O3 ethanol (containing 1% Nafion) dispersion solution, and load Cu2O@Bi2O3 onto a Si wafer by static coating method to obtain a Cu2O@Bi2O3 / Si photocathode for photoelectrocatalytic CO2 reduction.
[0012] More preferably, in step (1), the active metal salt is either bismuth nitrate or bismuth acetate.
[0013] More preferably, in step (1), the amount of the active metal source added is 0.5 to 1.0 mmol; the amount of the organometallic ligand 1,3,5-pyromellitic acid added is 0.1 to 0.3 mmol; the temperature of the electric heating oven is 100 to 150°C, and the reaction time is 8 to 16 h.
[0014] More preferably, in step (2), the concentration of the precursor powder is 1-5 g / L, the concentration of the metal source solution is 5-20 mmol / L, the amount of metal source solution added is 50-100 mL, and the stirring time is 6-12 h.
[0015] More preferably, in step (2), the copper source is copper nitrate, the concentration of the copper source is 5-20 mmol, and the amount added is 50-100 mL.
[0016] More preferably, in step (3), the carbonization temperature is 200-500℃, the time is 1-4h, the inert gas is N2, and the flow rate is 180ml / min.
[0017] More preferably, in step (4), the concentration of the Cu2O@Bi2O3 ethanol dispersion solution is 0.2 to 1.0 mg / mL.
[0018] More preferably, in step (4), the Cu2O@Bi2O3 ethanol dispersion solution contains 1% Nafion.
[0019] More preferably, in step (4), the number of static coating applications is 20 to 50.
[0020] More preferably, in step (4), the concentration of Cu2O@Bi2O3 powder solution is 0.2-1.0 mg / mL, and the number of static lifting cycles is 20-50.
[0021] The present invention also provides that, in a low potential range, the photocathode reduces carbon dioxide to formic acid in the potential range of -0.1 to -0.55 V vs RHE.
[0022] Compared with the prior art, the advantages of the present invention are:
[0023] (1) Compared with the original Bi2O3 / Si photocathode, the Cu2O@Bi2O3 / Si pnp junction photocathode constructed in this invention has a current density that is increased by about 5 times under a bias voltage of -0.3V vs RHE, and has better photoelectrocatalytic reduction performance of carbon dioxide and a lower reduction initiation potential.
[0024] (2) The Cu2O@Bi2O3 / Si pnp junction photocathode constructed in this invention has a better local CO2 enrichment ability, which is about 5 times that of the original Bi2O3 / Si photocathode.
[0025] (3) The present invention uses hydrothermal method and static pulling method to prepare photocathode, without the need for complicated coating process. The prepared photocathode has excellent photoelectrochemical performance and the ability to reduce carbon dioxide to formic acid. Attached Figure Description
[0026] Figure 1 SEM image of the Cu2O@Bi2O3 / Si photocathode prepared for photoelectrocatalytic CO2 reduction in Example 1.
[0027] Figure 2 TEM image of Cu2O@Bi2O3 prepared for photoelectrocatalytic CO2 reduction in Example 1.
[0028] Figure 3 The ultraviolet-visible absorption spectrum of the Cu2O@Bi2O3 / Si photocathode prepared for photoelectrocatalytic CO2 reduction in Example 2 is shown.
[0029] Figure 4 Transient photocurrent curves of Cu2O@Bi2O3 / Si photocathodes for photoelectrocatalytic CO2 reduction were prepared for Example 2.
[0030] Figure 5 LSV curves of Cu2O@Bi2O3 / Si photocathodes for photoelectrocatalytic CO2 reduction were prepared for Example 2.
[0031] Figure 6 The Bi2O3@Cu2O / Si photocathode prepared in Example 3 was used to measure the Faraday efficiency of the photoelectrocatalytic reduction of CO2 to formic acid.
[0032] Figure 7 The nuclear magnetic resonance spectrum of the Cu2O@Bi2O3 / Si photocathode prepared in Example 3 for photoelectrocatalytic reduction of carbon dioxide to produce formic acid is shown.
[0033] Figure 8 CO2-TPD image of Cu2O@Bi2O3 / Si photocathode active component Cu2O@Bi2O3 for photoelectrocatalytic carbon dioxide reduction prepared in Example 3. Detailed Implementation
[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.
[0035] Example 1
[0036] Fabrication of Cu2O@Bi2O3 / Si photocathode
[0037] (1) First, bismuth-based metal-organic framework materials are prepared as precursors using the existing hydrothermal method. The specific steps are as follows:
[0038] 1) Weigh 1.2g of trimesic acid and 0.89g of bismuth nitrate pentahydrate, stir and dissolve them in 60mL of organic solvent (methanol:N,N-dimethylformamide = 3:1), stir vigorously, then transfer to a polytetrafluoroethylene liner, heat at 120℃ for 12 hours, centrifuge, wash, and vacuum dry at 80℃ overnight to obtain bismuth-based metal-organic framework material as precursor material.
[0039] 2) Weigh 0.2 g of bismuth-based metal-organic framework precursor powder and ultrasonically disperse it in 100 ml of deionized water. Add 5-20 mmol / L copper nitrate solution dropwise. Stir vigorously for 6 h, centrifuge to collect the precipitate, wash with deionized water, and vacuum dry at 80 °C for 12 h.
[0040] 3) The copper-supported bismuth-based metal-organic framework precursor powder was placed in a tube furnace and calcined at 300°C for 3 hours in a N2 atmosphere to obtain the metal-organic framework derivative, denoted as Cu2O@Bi2O3.
[0041] Figure 1 This is a TEM image of the Cu2O@Bi2O3 heterojunction material prepared in this embodiment. Cu2O is uniformly anchored on the surface of Bi2O3 derived from bismuth-based metal-organic framework material, and the Cu2O particle size is about 50 nm.
[0042] (2) Cu2O@Bi2O3 is loaded onto the Si surface to form a Cu2O@Bi2O3 / Si photocathode.
[0043] 1) Weigh 0.01g of Cu2O@Bi2O3 powder and disperse it in 5ml of anhydrous ethanol (50ul 5% Nafion). Sonicate for 30min until completely dispersed. At this point, the concentration of Cu2O@Bi2O3 powder is 0.2mg / ml.
[0044] 2) A layer of Cu2O@Bi2O3 was coated onto the surface of the Si electrode using a static dip-coating apparatus, with the number of dip-coating cycles being 20–50. This ultimately yielded a Cu2O@Bi2O3 / Si photocathode for photoelectrocatalytic carbon dioxide reduction.
[0045] Figure 2 This is a SEM image of the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment. Smaller Cu2O@Bi2O3 particles are uniformly loaded in the porous Si electrode, while larger Cu2O@Bi2O3 particles are loaded on the surface of the Si electrode.
[0046] Example 2
[0047] Photoelectrochemical performance of Cu2O@Bi2O3 / Si photocathode
[0048] The Cu2O@Bi2O3 / Si photocathode prepared in Example 1 was tested using a UV-Vis spectrophotometer. Its photoelectrochemical performance was tested using an electrochemical workstation in a three-electrode system. The Cu2O@Bi2O3 / Si photocathode was used as the working electrode, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode. Electrolysis was performed using a CO2-saturated 0.5M KHCO3 solution, with a 300W xenon lamp providing the light source at an intensity of 200 mW / cm². -2 .
[0049] Figure 3 The UV-Vis absorption spectrum of the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment shows that the light absorption intensity of the Bi2O3 / Si photocathode without Cu2O loading is lower than that of the Cu2O@Bi2O3 / Si photocathode. The Cu2O@Bi2O3 / Si photocathode, however, exhibits full-spectrum absorption and a stronger light absorption intensity.
[0050] Figure 4 This is the transient photocurrent spectrum of the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment. As can be seen from the figure, at 200 mW / cm²... -2 Under visible light irradiation, at -0.3V vs RHE conditions, the photocurrent of the Bi2O3 / Si photocathode without Cu2O load is only 2.4 mA cm⁻¹. -2 The photocurrent of Cu2O@Bi2O3 / Si is 6.7 mA / cm. -2 This indicates that the Cu2O@Bi2O3 / Si photocathode prepared in this example has excellent photoelectric conversion efficiency.
[0051] Example 3
[0052] Photoelectrocatalytic CO2 reduction performance of Cu2O@Bi2O3 / Si photocathode
[0053] The photoelectrochemical CO2 reduction performance of the Cu2O@Bi2O3 / Si photocathode prepared in Example 1 was tested in a closed H-Cell electrolytic cell. High-purity CO2 gas was continuously introduced during the test to saturate the electrolyte. The Cu2O@Bi2O3 / Si photocathode was used as the working electrode, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode. The product Faradaic efficiency of the reduction reaction was analyzed by measuring the concentration of the reduction product.
[0054] Figure 5The linear sweep voltammetry curves of the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment are shown. As can be seen from the figure, the original Si electrode lacks CO2 reduction activity, thus exhibiting a poor voltage-current response. In contrast, the Cu2O@Bi2O3 / Si photocathode demonstrates superior CO2 reduction performance, with an overpotential reduction of 219 mV (10 mA cm⁻¹) compared to the Bi2O3 / Si photocathode without Cu2O anchoring. -2 ).
[0055] Figure 6 The figure shows the product Faradaic efficiency of the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment at different test potentials. As can be seen from the figure, formic acid is the main reduction product at all test potentials, with a Faradaic efficiency as high as 94.0% at -0.3V vs RHE. CO and H2 are byproducts with lower Faradaic efficiencies.
[0056] Figure 7 The 1H NMR spectrum of the liquid phase products of the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment was analyzed at a potential of -0.3V vs RHE. The figure shows that only formic acid was detected in the electrolyte after the reaction, with no other liquid phase products, indicating the photoelectrocatalytic performance of the Cu2O@Bi2O3 / Si photocathode in reducing CO2 to formic acid.
[0057] Figure 8 The image shows the CO2-TPD curve of the active component Cu2O@Bi2O3 in the Cu2O@Bi2O3 / Si photocathode prepared in this embodiment. Cu2O@Bi2O3 exhibits a higher CO2 desorption peak in the high-temperature region, indicating that it has a stronger CO2 chemisorption capacity than Bi2O3.
[0058] It should be understood that the above detailed description of the technical solutions of the present invention with reference to optimized embodiments is illustrative and not restrictive. It should not be considered that the specific implementation of the present invention is limited to this. For those skilled in the art, any modifications to the technical solutions described in the embodiments or equivalent substitutions of some technical features without departing from the concept of the present invention should be considered as falling within the scope of patent protection defined by the claims submitted by the present invention.
[0059] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction, characterized in that, It was prepared by hydrothermal method and carbonized in an inert atmosphere; The specific steps include: (1) Preparation of bismuth-based metal-organic framework (Bi-MOF) as a precursor: The active metal source and the organometallic ligand 1,3,5-pyromellitic acid were added to the organic solution and stirred continuously until completely dissolved. The resulting precursor solution was transferred to a polytetrafluoroethylene liner and placed in a stainless steel reactor under an electric heating oven. After the reaction was completed, the reactor was removed and cooled at room temperature. The product after the reaction was repeatedly washed with deionized water, dried, crushed and sieved to obtain the bismuth-based metal-organic framework. (2) The bismuth-based metal-organic framework material obtained in step (1) is dispersed in deionized water, and a metal source solution is slowly added. After stirring, the precipitate is obtained by centrifugation, washed repeatedly with deionized water, and dried to obtain a metal-modified bismuth-based metal-organic framework material; the metal source contains Cu. (3) The metal-modified bismuth-based metal-organic framework material obtained in step (2) is carbonized in an inert gas atmosphere to obtain Cu2O@Bi2O3 catalyst; (4) Prepare Cu2O@Bi2O3 ethanol dispersion solution, and load Cu2O@Bi2O3 onto Si wafer by static coating method to obtain Cu2O@Bi2O3 / Si photocathode for photoelectrocatalytic CO2 reduction.
2. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (1), the active metal salt is either bismuth nitrate or bismuth acetate.
3. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (1), the amount of the active metal source added is 0.5 ~ 1.0 mmol; the amount of the organometallic ligand 1,3,5-pyromellitic acid added is 0.1 ~ 0.3 mmol; the temperature of the electric heating oven is 100 ~ 150 ℃, and the reaction time is 8 ~ 16 h.
4. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (2), the concentration of the bismuth-based metal-organic framework material is 1-5 g / L, the concentration of the metal source solution is 5-20 mmol / L, the amount of metal source solution added is 50-100 mL, and the stirring time is 6-12 h.
5. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (3), the carbonization temperature is 200 ~ 500 ℃ and the time is 1 ~ 4 h.
6. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (4), the concentration of the Cu2O@Bi2O3 ethanol dispersion solution is 0.2~1.0 mg / mL.
7. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (4), the Cu2O@Bi2O3 ethanol dispersion solution contains 1% Nafion.
8. The method for preparing a photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction according to claim 1, characterized in that, In step (4), the static coating is applied 20 to 50 times.
9. A Cu2O@Bi2O3 / Si photocathode with CO2 adsorption capacity and photoelectrocatalytic CO2 reduction prepared by the preparation method according to any one of claims 1 to 8.
10. The application of the Cu2O@Bi2O3 / Si photocathode according to claim 9 in photoelectrocatalytic CO2 reduction, characterized in that, The photoelectrocatalytic reduction of carbon dioxide to formic acid was tested in the potential range of -0.1 to -0.55 V vs RHE.