Titanium dioxide photocatalyst modified by agbi alloy, and preparation method and application thereof
By loading AgBi alloy onto a titanium dioxide support to construct heterogeneous bimetallic active sites, the problems of selectivity and low yield of photocatalytic reduction of CO2 to methane were solved, and a highly efficient process for converting CO2 to CH4 was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI GEO UNIVERSITY
- Filing Date
- 2026-04-13
- Publication Date
- 2026-07-03
Smart Images
Figure CN122321856A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials preparation technology, specifically relating to an AgBi alloy-modified titanium dioxide photocatalyst, its preparation method, and its application. Background Technology
[0002] The photocatalytic reduction of carbon dioxide (CO2) to methane (CH4) can not only effectively alleviate greenhouse gas emissions, but also utilize carbon dioxide to produce high-value chemical raw materials. Therefore, the photocatalytic reduction technology of carbon dioxide is a promising technology.
[0003] However, the photocatalytic reduction of CO2 using solar energy still faces challenges such as low catalytic activity and complex products. In the process of photocatalytically reducing CO2 to produce methane, the high selectivity of CH4 from CO2 remains a significant challenge due to the involvement of an eight-electron transfer process and competition between CO and H2 products. Summary of the Invention
[0004] The purpose of this invention is to provide an AgBi alloy-modified titanium dioxide photocatalyst, its preparation method, and its application, in order to overcome the problems of low selectivity and low yield in the photocatalytic reduction of CO2 to produce methane in related technologies.
[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0006] In a first aspect, the present invention provides an AgBi alloy-modified titanium dioxide photocatalyst, wherein the AgBi alloy-modified titanium dioxide photocatalyst comprises a titanium dioxide support and AgBi alloy loaded on the surface of the titanium dioxide support. x Bi y Alloy; wherein at least a portion of Ag x Bi y The alloy is connected to titanium dioxide by chemical bonds, x:y = (0.5~2):1.
[0007] In one optional embodiment, the AgBi alloy-modified titanium dioxide photocatalyst is used as a basis, wherein the Ag... x Bi y The alloy has a weight percentage of 20-70%.
[0008] Secondly, the present invention provides a method for preparing the above-mentioned AgBi alloy-modified titanium dioxide photocatalyst, comprising the following steps:
[0009] S01. React the silver source and bismuth source according to the specified ratio to obtain Ag. x Bi y Alloy precursor;
[0010] S02. The Ag x Bi y The alloy precursor is dispersed in a reducing agent solution to allow the Ag to... x Bi y The alloy precursor undergoes a reduction reaction to obtain Ag. x Bi y Alloy dispersion;
[0011] S03. According to the dosage ratio, add the Ag... x Bi y Titanium dioxide was added to the alloy dispersion, and after the reaction was complete, the mixture was washed and dried.
[0012] In one optional implementation, step S01, the reaction of the silver source and the bismuth source, includes:
[0013] S011. Disperse the silver source and bismuth source in an aqueous nitric acid solution to obtain the raw material solution;
[0014] S012. The raw material solution is added dropwise to an alkaline solution with a pH of 13-14 and the reaction is carried out. The resulting product is washed until neutral.
[0015] In one optional embodiment, step S012 includes aging the mixture in a constant temperature water bath at 40–50°C for 1–3 hours.
[0016] In one optional embodiment, in step S01, the silver source is silver nitrate;
[0017] And / or, the bismuth source includes at least one of bismuth nitrate, basic bismuth carbonate, bismuth trichloride, and bismuth citrate.
[0018] In one optional embodiment, in step S02, the reduction reaction includes: placing the mixed solution in an ice-water bath and stirring for 3 to 5 hours;
[0019] And / or, the reducing agent includes sodium borohydride and / or potassium borohydride.
[0020] In an optional implementation, in step S03, the step of sending the Ag... x Bi y Titanium dioxide is added to the alloy dispersion, and after sufficient reaction, it is washed and dried, including:
[0021] To the Ag x Bi y Add titanium dioxide to the alloy dispersion, continue stirring for 8–10 h, wash away residual reducing agent, and then vacuum dry at 60–80 °C for 6–10 h.
[0022] Thirdly, the present invention provides the application of the above-mentioned AgBi alloy-modified titanium dioxide photocatalyst in the photocatalytic preparation of methane from carbon dioxide.
[0023] The technical solution of this invention has the following advantages:
[0024] The AgBi alloy-modified titanium dioxide photocatalyst provided by this invention (hereinafter referred to as AgBi-TiO2 photocatalyst) includes a titanium dioxide support and Ag supported on the surface of the titanium dioxide support. x Bi y Alloy. Experimental studies have shown that the AgBi alloy-modified titanium dioxide photocatalyst can significantly reduce the types of byproducts in the CO2-CH4 conversion, while significantly improving the selectivity and formation rate of CH4.
[0025] In the aforementioned composite material, Ag nanocrystals and Bi nanocrystals are mutually doped to construct heterogeneous bimetallic active sites for TiO2 photocatalysts. This allows for precise control of photogenerated electron migration and synergistic enhancement of the conversion efficiency and selectivity of the CO2 reduction reaction. This bifunctional design operates through two key mechanisms: (i) the formation of the heterogeneous bimetallic Ag-Bi alloy modulates the interfacial electron transfer barrier between the metal and semiconductor components; and (ii) the spatial confinement of highly dispersed Ag nanocrystals within the Bi matrix enables a synergistic effect between CO hydrogenation at the Ag active sites and CO2 activation at the Bi sites. Attached Figure Description
[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0027] Figure 1 The XRD patterns of the AgBi-TiO2 photocatalyst prepared in Example 1 of this invention, the TiO2 prepared in step (2) of Example 1, the Bi-TiO2 photocatalyst prepared in Comparative Example 3, and the Ag-TiO2 photocatalyst prepared in Comparative Example 4 are shown.
[0028] Figure 2 The above are the HRTEM spectra of the AgBi alloy prepared in step (3) of Example 1 of the present invention; wherein, (a) is the elemental surface distribution map of the AgBi alloy, and (b) is the HRTEM spectra of the AgBi alloy.
[0029] Figure 3The image shows the HRTEM spectrum of the AgBi-TiO2 photocatalyst prepared in Example 1 of this invention.
[0030] Figure 4 The following are X-ray photoelectron spectroscopy (XPS) spectra of various materials in Example 1 of this invention; wherein, (a) is the XPS spectrum of Ti in TiO2 and AgBi-TiO2; (b) is the XPS spectrum of Ag in AgBi-TiO2 and AgBi alloy; (c) is the XPS spectrum of Bi in AgBi-TiO2 and AgBi alloy; and (d) is the XPS spectrum of O in TiO2 and AgBi-TiO2.
[0031] Figure 5 The figure shows the experimental results of Experiment Example 2 of this invention. Detailed Implementation
[0032] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0033] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0034] Example 1
[0035] AgBi-TiO2 photocatalyst was prepared according to the following method:
[0036] (1) Preparation of AgBi alloy precursor:
[0037] Under magnetic stirring, 1.5 mmol of Bi(NO3)3·5H2O was dispersed in a solution containing 48.3 mL of deionized water and 1.7 mL of HNO3 (12 mol·L⁻¹). -1 The raw material solution was prepared by sonication in a nitric acid aqueous solution for 10 min, followed by the addition of 1.5 mmol of AgNO3 under continuous stirring until completely dissolved. Then, 11.87 g of potassium hydroxide was dissolved in 50 mL of deionized water under stirring to obtain an alkaline solution with a pH of 13.5. The raw material solution was then slowly added dropwise to the alkaline solution, while the resulting mixture was aged in a constant temperature water bath at 45 °C for 1 h. After filtration to neutrality, the AgBi alloy precursor was obtained and lyophilized for storage.
[0038] (2) Preparation of TiO2:
[0039] A mixture of 45 mL tetrabutyl titanate (Ti(OC4H9)4) and 7.2 mL hydrofluoric acid (HF) was vigorously stirred at room temperature for 15 minutes to obtain a homogeneous solution. The homogeneous solution was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and subjected to hydrothermal treatment at 200 °C for 24 h. The resulting precipitate was collected and repeatedly washed with deionized water until neutral, then filtered and freeze-dried to obtain the TiO2 product.
[0040] (3) Synthesis of AgBi-TiO2 photocatalyst:
[0041] Take 0.1g of the AgBi alloy precursor prepared in step (1), re-disperse it ultrasonically in 20 mL of 1mol / L NaBH4 solution, and stir continuously in an ice-water bath for 4h to carry out the reduction reaction. After the reaction, wash until neutral to obtain AgBi alloy dispersion. Add 0.1g of TiO2 prepared in step (2) to the above AgBi alloy dispersion while stirring continuously overnight. After the reaction, wash the suspension repeatedly with deionized water to completely remove residual NaBH4, and then vacuum dry at 60℃ for 8h to obtain AgBi-TiO2 photocatalyst.
[0042] In the AgBi-TiO2 photocatalyst synthesized in this embodiment, the weight percentage of AgBi alloy is 50%.
[0043] Example 2
[0044] The AgBi2-TiO2 photocatalyst was prepared according to the method of Example 1. The difference is that in step (1) of this example, the amount of Bi(NO3)3·5H2O used is about 1.5 mmol and the amount of AgNO3 used is about 0.75 mmol.
[0045] Example 3
[0046] The Ag2Bi-TiO2 photocatalyst was prepared according to the method of Example 1. The difference is that in step (1) of this example, the amount of Bi(NO3)3·5H2O used is about 0.75 mmol and the amount of AgNO3 used is about 1.5 mmol.
[0047] Example 4
[0048] The AgBi-TiO2 photocatalyst was prepared according to the method of Example 1, except that the amount of TiO2 used in step (3) of this example is about 0.4g.
[0049] In this embodiment, the AgBi alloy content in the synthesized AgBi-TiO2 photocatalyst is 20% by weight.
[0050] Example 5
[0051] The AgBi-TiO2 photocatalyst was prepared according to the method of Example 1, except that the amount of TiO2 used in step (3) of this example is about 0.043g.
[0052] In this embodiment, the AgBi alloy content in the synthesized AgBi-TiO2 photocatalyst is 70% by weight.
[0053] Comparative Example 1
[0054] The Ag4Bi-TiO2 photocatalyst was prepared according to the method of Example 1. The difference is that in step (1) of this comparative example, the amount of Bi(NO3)3·5H2O used was about 0.75 mmol and the amount of AgNO3 used was about 3 mmol.
[0055] Comparative Example 2
[0056] The AgBi3-TiO2 photocatalyst was prepared according to the method of Example 1. The difference is that in step (1) of this comparative example, the amount of Bi(NO3)3·5H2O used was about 2.25 mmol and the amount of AgNO3 used was about 0.75 mmol.
[0057] Comparative Example 3
[0058] Bi-TiO2 photocatalyst was prepared according to the following method:
[0059] (1) Preparation of Bi precursor:
[0060] Under magnetic stirring, 3 mmol of Bi(NO3)3·5H2O was dispersed in a solution containing 48.3 mL of deionized water and 1.7 mL of HNO3 (12 mol·L⁻¹). -1 The raw material solution was obtained by sonication in a nitric acid aqueous solution for 10 min. Under stirring, 11.87 g of potassium hydroxide was dissolved in 50 mL of deionized water to obtain an alkaline solution with a pH of 13.5. The raw material solution was then slowly added dropwise to the alkaline solution, while the resulting mixture was aged in a constant temperature water bath at 45 °C for 1 h. The mixture was then filtered until neutral to obtain the Bi precursor, which was then lyophilized and stored.
[0061] (2) Preparation of TiO2:
[0062] A mixture of 45 mL tetrabutyl titanate (Ti(OC4H9)4) and 7.2 mL hydrofluoric acid (HF) was vigorously stirred at room temperature for 15 minutes to obtain a homogeneous solution. The homogeneous solution was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and subjected to hydrothermal treatment at 200 °C for 24 h. The resulting precipitate was collected and repeatedly washed with deionized water until neutral, then filtered and freeze-dried to obtain the TiO2 product.
[0063] (3) Synthesis of Bi-TiO2 photocatalyst:
[0064] Take 0.1g of the Bi precursor prepared in step (1), re-disperse it ultrasonically in 20mL of NaBH4 solution with a concentration of 1mol / L, and stir continuously in an ice-water bath for 4h to carry out the reduction reaction. After the reaction is completed, wash until neutral to obtain Bi dispersion. Add 0.1g of TiO2 prepared in step (2) to the above Bi dispersion while stirring continuously overnight. After the reaction is completed, wash the suspension repeatedly with deionized water to completely remove the residual NaBH4, and then vacuum dry at 60℃ for 8h to obtain Bi-TiO2 photocatalyst.
[0065] In the Bi-TiO2 photocatalyst synthesized in this comparative example, the weight percentage of Bi metal is 50%.
[0066] Comparative Example 4
[0067] Ag-TiO2 photocatalyst was prepared according to the following method:
[0068] (1) Preparation of Ag precursor:
[0069] Under magnetic stirring, 3 mmol of AgNO3 was dispersed in a solution containing 48.3 mL of deionized water and 1.7 mL of HNO3 (12 mol·L⁻¹). -1 The raw material solution was obtained by stirring in a nitric acid aqueous solution until completely dissolved. Under stirring, 11.87 g of potassium hydroxide was dissolved in 50 mL of deionized water to obtain an alkaline solution with a pH of 13.5. Then, the raw material solution was slowly added dropwise to the alkaline solution, while the resulting mixture was aged in a constant temperature water bath at 45°C for 1 hour. The mixture was then filtered until neutral to obtain the Ag precursor, which was then lyophilized and stored.
[0070] (2) Preparation of TiO2:
[0071] A mixture of 45 mL tetrabutyl titanate (Ti(OC4H9)4) and 7.2 mL hydrofluoric acid (HF) was vigorously stirred at room temperature for 15 minutes to obtain a homogeneous solution. The homogeneous solution was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and subjected to hydrothermal treatment at 200 °C for 24 h. The resulting precipitate was collected and repeatedly washed with deionized water until neutral, then filtered and freeze-dried to obtain the TiO2 product.
[0072] (3) Synthesis of Ag-TiO2 photocatalyst:
[0073] Take 0.1g of the Ag precursor prepared in step (1), re-disperse it ultrasonically in 20mL of NaBH4 solution with a concentration of 1mol / L, and stir continuously in an ice-water bath for 4h to carry out the reduction reaction. After the reaction is completed, wash until neutral to obtain Ag dispersion. Add 0.1g of TiO2 prepared in step (2) to the above Ag dispersion while stirring continuously overnight. After the reaction is completed, wash the suspension repeatedly with deionized water to completely remove residual NaBH4, and then vacuum dry at 60℃ for 8h to obtain Ag-TiO2 photocatalyst.
[0074] In the Ag-TiO2 photocatalyst synthesized in this comparative example, the weight percentage of Ag metal is 50%.
[0075] Test case
[0076] (1) XRD analysis was performed on the AgBi-TiO2 photocatalyst prepared in Example 1, the TiO2 prepared in step (2) of Example 1, the Bi-TiO2 photocatalyst prepared in Comparative Example 3, and the Ag-TiO2 photocatalyst prepared in Comparative Example 4, respectively. The results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the XRD diffraction peaks of the AgBi-TiO2 photocatalyst prepared in Example 1 correspond to the Bi standard card (JCPDS No. 44-1246), Ag standard card (JCPDS No. 04-0783), and TiO2 standard card (JCPDS No. 21-1272), indicating that AgBi in the AgBi-TiO2 photocatalyst was successfully synthesized and successfully loaded onto the TiO2 catalyst.
[0077] (2) The AgBi alloy prepared in Example 1 was subjected to HRTEM detection, and the results are as follows: Figure 2As shown in the figure, (a) is the elemental plane distribution diagram of the AgBi alloy, in which Ag and Bi metals can be clearly observed; (b) is the HRTEM spectrum of the AgBi alloy, which, after analysis and calculation by Digital Micrograph (DM) software, clearly shows the lattice fringes of metallic Ag with a lattice spacing of 0.24 nm and the lattice fringes of metallic Bi with a lattice spacing of 0.33 nm.
[0078] (3) The AgBi-TiO2 photocatalyst prepared in Example 1 was subjected to HRTEM detection, and the results are as follows: Figure 3 As shown, analysis and calculation using Digital Micrograph (DM) software clearly revealed lattice fringes of TiO2 with a lattice spacing of 0.35 nm, lattice fringes of Ag with a lattice spacing of 0.24 nm, and lattice fringes of Bi with a lattice spacing of 0.33 nm, proving that the AgBi alloy is tightly composited with the TiO2 catalyst.
[0079] (4) X-ray photoelectron spectroscopy was performed on the TiO2 prepared in step (2) of Example 1, the AgBi alloy prepared in step (3) of Example 1, and the AgBi-TiO2 photocatalyst prepared in Example 1, respectively. The test results are as follows: Figure 4 As shown in the figure, (a) is the XPS spectrum of Ti in TiO2 and AgBi-TiO2; (b) is the XPS spectrum of Ag in AgBi-TiO2 and AgBi alloy; (c) is the XPS spectrum of Bi in AgBi-TiO2 and AgBi alloy; and (d) is the XPS spectrum of O in TiO2 and AgBi-TiO2.
[0080] Depend on Figure 4 As can be seen, by comparing the energy spectra of Ag, Bi, and Ti elements before and after the AgBi alloy and TiO2 catalyst are combined, it is found that their electron binding energies have all shifted. This indicates that the AgBi alloy was successfully loaded onto TiO2 and connected to the TiO2 surface through chemical bonds, rather than a simple physical composite. This is also an important reason for the improved photocatalytic reduction performance of the AgBi-TiO2 photocatalyst.
[0081] Experimental Example 1
[0082] The composite photocatalysts, AgBi alloys, and TiO2 prepared in Examples 1-5 and Comparative Examples 1-4 were used to conduct experiments on the photocatalytic reduction of CO2 to CH4. The experimental methods are as follows:
[0083] The photocatalytic reduction of CO2 was carried out in a stainless steel reactor using a 300W xenon lamp to simulate solar radiation. 2.5 mL of deionized water was added to an open quartz container located at the bottom of the reactor. Subsequently, 10 mg of each sample was uniformly coated onto a quartz plate. The system was evacuated using a vacuum pump and purged three times with high-purity CO2 to create an inert atmosphere. High-purity CO2 was then supplied to the reactor and maintained at a pressure of 1 atm. The reactor temperature was adjusted to 20°C using a water thermostat system. Gas phase products were collected every 2 hours and analyzed using gas chromatography. The formation rates of CH4 and CO in the products (μmol·g⁻¹) were determined. -1 ·h -1 The selectivity (%) of each product was calculated, and the results are shown in Table 1.
[0084] Table 1. Formation rates of each product (μmol·g) -1 ·h -1 ) and selectivity (%)
[0085] As can be seen from Table 1, compared with other materials, the AgBi alloy-modified titanium dioxide photocatalyst provided by the present invention can significantly improve the generation rate and selectivity of CH4 in the product.
[0086] Experimental Example 2
[0087] To evaluate the recyclability of the photocatalyst, repeated experiments were conducted under the same conditions. Following the experimental method described in Example 1, the reusability of the AgBi-TiO2 photocatalyst prepared in Example 1 was tested, and it was cycled four times. Before each cycle, the photocatalyst was dried in an oven at 60°C, followed by treatment in a vacuum oven at 150°C to remove adsorbed carbonaceous material. The formation rates (μmol·g⁻¹) of CH₄ and CO in the product were measured at 1, 2, 3, and 4 hours after the start of each experiment. -1 ·h -1 ), and calculate the selectivity (%) respectively, the results are as follows Figure 5 As shown. By Figure 5 It can be seen that the AgBi alloy-modified titanium dioxide photocatalyst provided by the present invention has good reproducibility and practicality. After being used 4 times, its CH4 yield and selectivity did not decrease significantly.
[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. 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 list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. An AgBi alloy-modified titanium dioxide photocatalyst, characterized in that, The AgBi alloy modified titanium dioxide photocatalyst comprises a titanium dioxide carrier and Ag x Bi y alloy; wherein at least part of the Ag x Bi y alloy is connected to the titanium dioxide through a chemical bond, and x:y=(0.5-2):
1.
2. The AgBi alloy-modified titanium dioxide photocatalyst according to claim 1, characterized in that, The AgBi alloy is present in an amount of 20 to 70% by weight, based on the total weight of the titanium dioxide photocatalyst modified with the AgBi alloy. x Bi y Bi Bi 3. The method for preparing the AgBi alloy-modified titanium dioxide photocatalyst according to claim 1 or 2, characterized in that, Includes the following steps: S01. React the silver source and bismuth source according to the specified ratio to obtain Ag. x Bi y Alloy precursor; S02. The Ag x Bi y The alloy precursor is dispersed in a reducing agent solution to allow the Ag to... x Bi y The alloy precursor undergoes a reduction reaction to obtain Ag. x Bi y Alloy dispersion; S03. According to the dosage ratio, add the Ag... x Bi y Titanium dioxide was added to the alloy dispersion, and after the reaction was complete, the mixture was washed and dried.
4. The preparation method according to claim 3, characterized in that, In step S01, the reaction of the silver source and the bismuth source includes: S011. Disperse the silver source and bismuth source in an aqueous nitric acid solution to obtain the raw material solution; S012. The raw material solution is added dropwise to an alkaline solution with a pH of 13-14 and the reaction is carried out. The resulting product is washed until neutral.
5. The preparation method according to claim 4, characterized in that, In step S012, the reaction includes aging the mixture in a constant temperature water bath at 40–50 °C for 1–3 h.
6. The preparation method according to claim 3, characterized in that, In step S01, the silver source is silver nitrate; And / or, the bismuth source includes at least one of bismuth nitrate, basic bismuth carbonate, bismuth trichloride, and bismuth citrate.
7. The preparation method according to claim 3, characterized in that, In step S02, the reduction reaction includes: placing the mixed solution in an ice-water bath and stirring for 3-5 hours; And / or, the reducing agent includes sodium borohydride and / or potassium borohydride.
8. The preparation method according to claim 3, characterized in that, In step S03, the step of sending to the Ag x Bi y Titanium dioxide is added to the alloy dispersion, and after sufficient reaction, it is washed and dried, including: To the Ag x Bi y Titanium dioxide was added to the alloy dispersion, and stirring was continued for 8–10 h. The residual reducing agent was washed away, and then the mixture was vacuum dried at 60–80 °C for 6–10 h.
9. The application of the AgBi alloy-modified titanium dioxide photocatalyst according to claim 1 or 2 in the photocatalytic preparation of methane from carbon dioxide.