Preparation method of silver and cobalt bimetallic monatomic loaded titanium carbide / titanium dioxide photocatalyst and application of silver and cobalt bimetallic monatomic loaded titanium carbide / titanium dioxide photocatalyst in selective photocatalytic reduction of carbon dioxide into methane
By loading Ag and Co single atoms onto a Ti3C2/TiO2 support, an AgCo-TT catalyst was constructed, which solved the problems of slow reaction kinetics and selectivity control in the reduction of CO2 to CH4, achieving efficient and low-cost photocatalytic effects. The catalyst exhibits good metal atom dispersion, significantly improving activity and selectivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIANGTAN UNIV
- Filing Date
- 2026-03-02
- Publication Date
- 2026-06-02
AI Technical Summary
Existing photocatalysts exhibit slow reaction kinetics, difficulty in selective control, and insufficient activity under mild conditions for the reduction of CO2 to CH4. Furthermore, the construction and stability of bimetallic single-atom sites are difficult to control, which limits their practical application.
Using Ti3C2/TiO2 as a support, AgCo-TT catalysts were constructed by loading Ag and Co single atoms through a self-reduction process. Taking advantage of the titanium defects and reduction ability of Ti3C2, combined with heat treatment, Ti3C2/TiO2 materials loaded with Ag and Co single atoms were formed, which promoted interfacial charge transfer and photogenerated carrier separation.
A low-cost, low-energy-consumption, and highly efficient photocatalytic reduction of CO2 to CH4 was achieved. The good dispersion of metal atoms on the catalyst significantly improved the catalytic activity and methane selectivity, achieving a product rate of 71.84 μmol g-1 h-1 and a selectivity of 91.7%.
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Figure CN122124829A_ABST
Abstract
Description
[0002] A method for preparing a silver-cobalt bimetallic single-atom supported titanium carbide / titanium dioxide photocatalyst and its application in selective photocatalytic carbon dioxide reduction to methane.
[0003] Technical Field: This invention relates to bimetallic single-atom synergistic catalytic materials, and particularly to a method for preparing silver and cobalt single atoms loaded on the surface of titanium carbide / titanium dioxide (Ti3C2 / TiO2) and their application in selective photocatalytic reduction of carbon dioxide to methane. Background Technology
[0004] With rapid economic and technological development, energy consumption and environmental pollution have become increasingly prominent issues, making the development of sustainable and clean energy conversion and utilization technologies an urgent need. Solar energy, due to its abundant and clean renewable resources, has attracted widespread attention. Among these, utilizing solar energy to convert carbon dioxide into high-value-added fuels is considered an effective way to alleviate energy and environmental problems. The main gaseous products of photocatalytic carbon dioxide (CO2) reduction include carbon monoxide (CO) and methane (CH4). Methane, with its high energy density and good compatibility with existing energy systems, is therefore more valuable for application. Photocatalytic methanation using water and CO2 as reactants holds promise for reducing dependence on hydrogen and thermal energy, and improving the safety and sustainability of the process. However, compared to the two-electron transfer process of CO2 reduction to CO, the conversion of CO2 to CH4 involves multi-electron and multi-proton coupling transfer steps, resulting in slow reaction kinetics and difficulty in selective control. Achieving efficient conversion under mild conditions still faces significant challenges. Although various semiconductor materials have been used for photocatalytic CO2 reduction, they generally suffer from insufficient activity, low product selectivity, and unclear reaction mechanisms, limiting their practical application. Therefore, developing photocatalyst systems that combine high activity and high selectivity is of great significance.
[0005] Studies have shown that stabilizing the key C1 intermediate and suppressing photogenerated carrier recombination can help improve the selectivity of CO2 to CH4 conversion. Bimetallic single-atom catalysts exhibit unique advantages in enhancing catalytic activity and selectivity due to their ability to regulate electronic structure and reaction pathways through the synergistic effect of adjacent metal single atoms. However, the precise construction and stability control of bimetallic single-atom sites are challenging, and their structural evolution mechanism in photocatalysis still requires further investigation. Ti3C2MXene, with its two-dimensional layered structure and high electrical conductivity, shows promising application prospects in photocatalysis. Ti3C2MXene obtained by selectively etching the precursor readily forms titanium vacancy defects in its structure. These defects not only possess reduction capabilities but also facilitate the stable anchoring of single-atom or dual-single-atom metal species. Furthermore, Ti3C2, as a titanium-containing material, can be converted in situ to TiO2 during subsequent processing, thereby constructing a tightly coupled Ti3C2 / TiO2 heterostructure, effectively promoting interfacial charge transfer and photogenerated carrier separation.
[0006] Based on the above characteristics, a photocatalyst system with Ti3C2 / TiO2 as the support and bimetallic single-atom active sites was constructed, providing a new technical approach for achieving efficient and highly selective photocatalytic CO2 reduction to methane. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing a silver and cobalt bimetallic single-atom supported titanium carbide / titanium dioxide photocatalyst that is low in cost, low in energy consumption, and simple in preparation process, and its application in selective photocatalytic carbon dioxide reduction to methane.
[0008] The technical solution of the present invention is as follows:
[0009] A method for preparing a silver and cobalt bimetallic single-atom supported titanium carbide / titanium dioxide photocatalyst, using Ti3C2 material as a support, utilizes its abundant titanium defects and reducing ability to load Ag and Co single atoms onto titanium carbide nanosheets through a simultaneous self-reduction stabilization process, and then introduces TiO2 through heat treatment to obtain AgCo-TT material supported on Ag3C2 / TiO2. The specific steps include the following:
[0010] (1) Add Ti3AlC2 slowly to the etching agent at a mass-to-volume ratio of 1-2 g: 8-12 mL and stir at room temperature for 16-30 h. Wash the resulting suspension with deionized water and centrifuge 2-6 times to remove residual impurities until the pH of the suspension is 6-7.
[0011] (2) The washed suspension obtained in step (1) is filtered and dried to obtain titanium carbide powder, namely Ti3C2;
[0012] (3) Ti3C2 and metal salt solution were subjected to ultrasonic conditions to obtain Ti3C2 aqueous solution and metal salt solution respectively. Then, the metal salt solution was slowly added dropwise to Ti3C2 aqueous solution and magnetically stirred at room temperature for 6-10 h.
[0013] (4) The mixed solution obtained in step (3) is precipitated with acetone for 1-2 h; the resulting suspension is washed with deionized water, filtered and dried to obtain the silver and cobalt bimetallic single-atom supported Ti3C2 material, namely AgCo-TC;
[0014] (5) Disperse the powder obtained in step (4) uniformly in water under ultrasonic conditions to obtain AgCo-TC solution. Place the obtained solution in the polytetrafluoroethylene liner of the hydrothermal reactor and then perform hydrothermal reaction in an oven at 80-100 °C.
[0015] (6) After the hydrothermal reaction in step (5) is completed, the suspension is naturally cooled to room temperature. The resulting suspension is washed with deionized water, filtered and dried to obtain a silver and cobalt bimetallic single-atom supported titanium carbide / titanium dioxide (Ti3C2 / TiO2) photocatalyst, namely AgCo-TT.
[0016] Further, in step (1), the etching agent is lithium fluoride + hydrochloric acid or hydrofluoric acid.
[0017] Furthermore, in step (2), the drying is vacuum drying, with a temperature of 50–70 °C and a time of 12–36 h.
[0018] Furthermore, in step (3), the ultrasonic time for Ti3C2 is 50-60 min, and the ultrasonic time for the metal salt is 8-15 min.
[0019] Further, in step (3), the mass ratio of Ti3C2 to metal salt is 23-55:0-1, and the metal salt solution is any one or two of CoCl2·6H2O and AgNO3, or no metal salt is added to prepare a control sample.
[0020] Further, in step (4), the drying is vacuum drying at a temperature of 50-70 °C for 12-36 h; the acetone precipitation is carried out at a low temperature of 2-8 °C.
[0021] Furthermore, in step (5), the sonication time of the AgCo-TC suspension is 8 to 15 minutes.
[0022] Furthermore, in step (5), the hydrothermal temperature of the AgCo-TC suspension is 80–100 °C, and the hydrothermal time is 2–6 h.
[0023] Furthermore, in step (6), the drying is vacuum drying, with a temperature of 50–70 °C and a time of 12–36 h.
[0024] The silver and cobalt bimetallic single-atom supported titanium carbide / titanium dioxide photocatalyst prepared by the above method is used in the selective photocatalytic reduction of carbon dioxide to methane, and includes the following steps:
[0025] In the photocatalytic reaction system, AgCo-TT was used as the photocatalyst. The catalyst and deionized water were mixed at a mass-volume ratio of 10 mg: 2 mL, placed in a magnetic stirrer, and the photocatalytic reaction system was evacuated to a vacuum by a vacuum pump. Then, carbon dioxide was introduced into the photocatalytic reaction system until the system pressure reached 0 kPa. Under magnetic stirring, a xenon lamp was used as the light source, equipped with a 420 nm cutoff filter, to conduct the photocatalytic reduction of carbon dioxide. The atmosphere in the photocatalytic reaction system was measured once at the same time interval, and quantitative analysis was performed using gas chromatography to determine the content of the product.
[0026] Furthermore, the xenon lamp described herein retains only visible light as its light source, with a wavelength of 420-780 nm.
[0027] As controls, pure Ti3C2, samples without metal single atoms (Ti3C2 / TiO2), and samples with only Co single atoms (Co-Ti3C2 / TiO2) were used as control photocatalysts, denoted as TC, TT, and Co-TT.
[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0029] (1) The preparation method of the present invention is simple, the reaction conditions are mild, the energy consumption is low, and the cost is low.
[0030] (2) This invention successfully constructed a photocatalyst supported on Ag and Co bimetallic single atoms (AgCo-TT). The metal active centers exist in a highly dispersed form at the atomic level, avoiding agglomeration and significantly improving the utilization efficiency of metal atoms.
[0031] (3) The AgCo-TT prepared by this invention has been applied for the first time in the field of photocatalytic CO2 reduction, showing good photocatalytic activity and high selectivity for methane products, which has high scientific significance and application value. Attached Figure Description
[0032] Table 1 shows the ICP composition of silver and cobalt atoms in AgCo-TT obtained in Example 1 and Co-TT obtained in Example 3. The mass fraction of cobalt atoms in Co-TT is 0.1141, and the mass fractions of silver and cobalt atoms in AgCo-TT are 0.6897 and 0.1413, respectively, indicating the successful loading of metal atoms on the catalyst.
[0033] Figure 1 The image shows an HRTEM image of AgCo-TT obtained in Example 1, which contains lattice fringes of Ti3C2 and TiO2, illustrating the formation of Ti3C2 / TiO2.
[0034] Figure 2 The image shows the AC HAADF-STEM image of AgCo-TT obtained in Example 1. The circles in the image represent individual metal atoms. The brighter ones are silver atoms, and the darker ones are cobalt atoms, indicating that silver and cobalt atoms are dispersed on the catalyst in the form of single atoms and have not agglomerated.
[0035] Figure 3 The Ag K-side Fourier transform (FT) k in the R space of the AgCo-TT obtained in Example 1 is... 2 The EXAFS spectra of the sample and the control sample indicate that the silver atoms in the catalyst did not agglomerate or oxidize, but were coordinated with carbon atoms and loaded onto the catalyst in the form of single atoms.
[0036] Figure 4 For the Fourier transform (FT) of Co K-side in the R space of AgCo-TT obtained in Example 1, 2 EXAFS spectra and comparison samples indicate that cobalt atoms in the catalyst did not agglomerate or oxidize, but were coordinated with carbon atoms and loaded onto the catalyst in the form of single atoms.
[0037] Figure 5 The graphs showing the production rates of carbon monoxide and methane and the methane selectivity of the products obtained from AgCo-TT in Example 1 indicate that TC and TT have almost no activity or selectivity in the photocatalytic reduction of carbon dioxide to methane. Co-TT shows a significant improvement in the photocatalytic reduction of carbon dioxide, but its methane selectivity is low. The highest photocatalytic reduction activity of AgCo-TT for CO2 reached 71.84 μmol g. -1 h -1 Furthermore, the methane selectivity is as high as 91.7%. Detailed Implementation
[0038] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.
[0039] Example 1
[0040] Preparation of silver and cobalt single-atom supported Ti3C2 / TiO2 (i.e., preparation of AgCo-TT)
[0041] (1) Add Ti3AlC2 slowly to the etching agent at a mass-volume ratio of 1 g: 12 mL and stir at room temperature for 24 h. Wash the resulting suspension with deionized water and centrifuge 2 to 6 times to remove residual impurities until the pH value of the suspension is 6.
[0042] (2) The washed suspension obtained in step (1) was filtered and dried under vacuum at 60 °C for 24 h to obtain titanium carbide powder, namely Ti3C2.
[0043] (3) Prepare 50 mL of solution with a mass concentration of 0.6 mg / mL. -1 A Ti3C2 solution, 50 mL, with a mass concentration of 0.1 mg / mL. -1 50 mL of AgNO3 solution with a mass concentration of 0.1 mg / mL -1 The CoCl2·6H2O solution was ultrasonically treated for 60, 10, and 10 min respectively, and labeled as solutions A, B, and C. 12.5 mL of solution B and 12.5 mL of solution C were accurately measured and slowly added dropwise to solution A, and the mixture was magnetically stirred at room temperature for 8 h.
[0044] (4) The suspension obtained in step (3) was precipitated with acetone at 2-8 °C for 2 h (the volume ratio of acetone to suspension was 2:1); the suspension was washed with deionized water, filtered, and vacuum dried at 60 °C for 24 h to obtain Ti3C2 material supported by silver and cobalt single atoms.
[0045] (5) Mix the powder obtained in step (4) with deionized water at a mass-volume ratio of 10 mg: 20 mL, sonicate for 10 min, place the resulting suspension in a polytetrafluoroethylene liner in a hydrothermal reactor, and then perform a hydrothermal reaction in an oven at 90 °C for 3 h.
[0046] (6) After the hydrothermal reaction in step (5) is completed, the suspension is naturally cooled to room temperature. The resulting suspension is washed with deionized water, filtered, and vacuum dried at 60 °C for 24 h to obtain silver and cobalt single-atom supported Ti3C2 / TiO2 material, namely AgCo-TT.
[0047] Example 2
[0048] AgCo-TT photocatalytic reduction of carbon dioxide test
[0049] In the photocatalytic reaction system, AgCo-TT was used as the photocatalyst. The catalyst and deionized water were mixed at a mass-volume ratio of 10 mg: 2 mL. A magnetic stir bar was placed in the mixture, and a vacuum pump was used to evacuate the photocatalytic reaction system to a vacuum. High-purity carbon dioxide was then introduced until the pressure inside the photocatalytic reaction system reached 0 kPa. Under magnetic stirring, a xenon lamp was used as the light source, and a 420 nm cutoff filter was used to conduct the photocatalytic reduction of carbon dioxide. The atmosphere in the photocatalytic reaction system was measured at the same time intervals, and quantitative analysis was performed using gas chromatography to determine the content of the product.
[0050] Example 3
[0051] Preparation of cobalt single-atom supported Ti3C2 / TiO2 (i.e., preparation of Co-TT)
[0052] (1) Add Ti3AlC2 slowly to the etching agent at a mass-volume ratio of 1 g: 12 mL and stir at room temperature for 24 h. Wash the resulting suspension with deionized water and centrifuge 2 to 6 times to remove residual impurities until the pH value of the suspension is 6.
[0053] (2) The washed suspension obtained in step (1) was filtered and dried under vacuum at 60 °C for 24 h to obtain titanium carbide powder, namely Ti3C2.
[0054] (3) Prepare 50 mL of solution with a mass concentration of 0.6 mg / mL. -1 A Ti3C2 solution, 50 mL, with a mass concentration of 0.1 mg / mL. -1 The CoCl2·6H2O solution was ultrasonicated for 60 and 10 min respectively, and labeled as solution A and solution B. 12.5 mL of solution B was accurately measured and slowly added dropwise to solution A, and the mixture was magnetically stirred at room temperature for 8 h.
[0055] (4) The suspension obtained in step (3) was precipitated with acetone at 2-8 °C for 2 h (the volume ratio of acetone to suspension was 2:1); the suspension was washed with deionized water, filtered, and vacuum dried at 60 °C for 24 h to obtain cobalt single-atom supported Ti3C2 material.
[0056] (5) Mix the powder obtained in step (4) with deionized water at a mass-volume ratio of 10 mg: 20 mL, sonicate for 10 min, place the resulting suspension in a polytetrafluoroethylene liner in a hydrothermal reactor, and then perform a hydrothermal reaction in an oven at 90 °C for 3 h.
[0057] (6) After the hydrothermal reaction in step (5) is completed, the suspension is naturally cooled to room temperature. The resulting suspension is washed with deionized water, filtered, and vacuum dried at 60 °C for 24 h to obtain cobalt single-atom supported Ti3C2 / TiO2 material, namely Co-TT.
[0058] Example 4
[0059] Preparation of Ti3C2 / TiO2 without metal atoms (i.e., preparation of TT)
[0060] (1) Add Ti3AlC2 slowly to the etching agent at a mass-volume ratio of 1 g: 12 mL and stir at room temperature for 24 h. Wash the resulting suspension with deionized water and centrifuge 2 to 6 times to remove residual impurities until the pH value of the suspension is 6.
[0061] (2) The washed suspension obtained in step (1) was filtered and dried under vacuum at 60 °C for 24 h to obtain titanium carbide powder, namely Ti3C2.
[0062] (3) The powder obtained in step (2) is mixed with deionized water at a mass-volume ratio of 10 mg: 20 mL, and ultrasonically treated for 10 min. The resulting suspension is placed in the polytetrafluoroethylene liner of the hydrothermal reactor and then hydrothermally reacted in an oven at 90 °C for 3 h.
[0063] (4) After the hydrothermal reaction in step (3) is completed, the suspension is naturally cooled to room temperature. The resulting suspension is washed with deionized water, filtered, and vacuum dried at 60 °C for 24 h to obtain Ti3C2 / TiO2 material without metal atoms, i.e. TT.
[0064] Table 1
[0065] catalyst Ag (wt%) Co (wt%) Co-TT n / a 0.1141 AgCo-TT 0.6897 0.1413
Claims
1. A method for preparing a silver-cobalt bimetallic single-atom supported titanium carbide / titanium dioxide photocatalyst, characterized in that, Includes the following steps: (1) Add Ti3AlC2 slowly to the etching agent at a mass-to-volume ratio of 1-2 g: 8-12 mL and stir at room temperature for 16-30 h. Wash the resulting suspension with deionized water and centrifuge 2-6 times to remove residual impurities until the pH of the suspension is 6-7. (2) The washed suspension obtained in step (1) is filtered and dried to obtain titanium carbide powder, namely Ti3C2; (3) Ti3C2 and metal salt solution were subjected to ultrasonic conditions to obtain Ti3C2 aqueous solution and metal salt solution respectively. Then, the metal salt solution was slowly added dropwise to Ti3C2 aqueous solution and magnetically stirred at room temperature for 6-10 h. (4) The mixed solution obtained in step (3) is precipitated with acetone for 1-2 h; the resulting suspension is washed with deionized water, filtered and dried to obtain the silver and cobalt bimetallic single-atom supported Ti3C2 material, namely AgCo-TC; (5) Disperse the powder obtained in step (4) uniformly in water under ultrasonic conditions to obtain AgCo-TC solution. Place the obtained solution in the polytetrafluoroethylene liner of the hydrothermal reactor and then perform hydrothermal reaction in an oven at 80-100 °C. (6) After the hydrothermal reaction in step (5) is completed, the suspension is naturally cooled to room temperature. The resulting suspension is washed with deionized water, filtered and dried to obtain a silver and cobalt bimetallic single-atom supported titanium carbide / titanium dioxide (Ti3C2 / TiO2) photocatalyst, namely AgCo-TT.
2. The preparation method according to claim 1, characterized in that, In step (1), the etching agent is lithium fluoride + hydrochloric acid or hydrofluoric acid.
3. The preparation method according to claim 1, characterized in that, In step (2), the drying is vacuum drying, the temperature is 50-70 °C, and the time is 12-36 h.
4. The preparation method according to claim 1, characterized in that, In step (3), the ultrasonic time for Ti3C2 is 50-60 min, and the ultrasonic time for metal salt is 8-15 min.
5. The preparation method according to claim 1, characterized in that, In step (3), the molar ratio of Ti3C2 to metal salt is 23-55:0-1, and the metal salt solution is any one or two of CoCl2·6H2O and AgNO3, or no metal salt is added to prepare a control sample.
6. The preparation method according to claim 1, characterized in that, In step (4), the drying is vacuum drying at a temperature of 50–70 °C for 12–36 h; the acetone precipitation is carried out at a low temperature of 2–8 °C.
7. The preparation method according to claim 1, characterized in that, In step (5), the sonication time of the AgCo-TC suspension is 8 to 15 minutes.
8. The preparation method according to claim 1, characterized in that, In step (5), the hydrothermal temperature of the AgCo-TC suspension is 80–100 °C, and the hydrothermal time is 2–6 h.
9. The preparation method according to claim 1, characterized in that, In step (6), the drying is vacuum drying, the temperature is 50-70℃, and the time is 12-36 h.
10. The application of the catalyst obtained by the preparation method according to any one of claims 1 to 9 in the selective photocatalytic reduction of carbon dioxide to methane.
11. The application according to claim 10, characterized in that, Includes the following steps: In the photocatalytic reaction system, AgCo-TT was used as the photocatalyst. The catalyst and deionized water were mixed at a mass-volume ratio of 10 mg: 2 mL. A magnetic stir bar was placed in the mixture, and a vacuum pump was used to evacuate the photocatalytic reaction system to a vacuum. Carbon dioxide was then introduced into the photocatalytic reaction system until the system pressure reached 0 kPa. Under magnetic stirring, a xenon lamp was used as the light source, and a 420 nm cutoff filter was used to conduct the photocatalytic reduction of carbon dioxide. The atmosphere in the photocatalytic reaction system was measured at the same time intervals, and quantitative analysis was performed using gas chromatography to determine the content of the product.
12. The application according to claim 11, characterized in that, The water described is deionized water and no sacrificial reagents were used.
13. The application according to claim 11, characterized in that, The xenon lamp described above emits only visible light with a wavelength of 420-780 nm.