Monatomic mo loaded titanium dioxide hollow sphere and preparation method and application thereof

Abstract

This invention relates to the field of low-carbon metallurgical CO2 reduction catalyst technology, specifically disclosing a single-atom Mo-supported hollow titanium dioxide sphere, its preparation method, and its applications. This invention inhibits CO from occupying the active center at the adsorption energy level through electronic regulation of the Mo sites, while simultaneously utilizing the hollow confinement structure of TiO2 to hinder CO from approaching the active center at the mass transfer level. The synergistic effect of these two methods significantly improves the stability and selectivity of the catalyst in a low-concentration CO2 atmosphere. Experiments show that in a simulated industrial low-concentration CO2 atmosphere (CO2 volume fraction 15%), the catalyst's activity did not significantly decrease after 16 hours of continuous reaction, and no obvious CO poisoning deactivation was observed at the Mo sites after the reaction. This demonstrates that the catalyst of this invention has broad application prospects and industrial promotion value in the fields of CO2 resource utilization from CO-containing industrial tail gas and syngas purification.

Description

Technical Field

[0001] This invention relates to the field of low-carbon metallurgical CO2 reduction catalyst technology, and in particular to a single-atom Mo-supported titanium dioxide hollow sphere, its preparation method and application. Background Technology

[0002] With the increasing urgency of global carbon emission reduction demands, the resource utilization of low-concentration CO2 in metallurgical flue gas has become a research hotspot. In the metallurgical industry, flue gas emitted from steelmaking, coking, and other fields not only contains low-concentration CO2 but also often contains high-concentration CO. This complex composition poses a severe challenge to traditional CO2 catalytic conversion technologies. Currently widely used catalysts, whether single noble metal catalysts or transition metal oxide-based catalysts, are prone to poisoning and deactivation in CO-containing environments. This is mainly because CO molecules have extremely strong adsorption properties, preferentially occupying the active sites of the catalyst. Simultaneously, these catalysts exhibit slow reaction kinetics at low temperatures (<300℃), severely limiting their practical application efficiency.

[0003] To address this issue, various anti-CO poisoning schemes have been proposed in the existing technology, but all of them have obvious limitations: (1) Catalysts using alloying strategies (such as Pt-Ru) can only reduce the concentration of CO in the feed gas by promoting CO oxidation, and cannot fundamentally prevent CO from adsorbing onto the active sites of the catalyst; (2) Schemes that achieve anti-CO poisoning through structural regulation methods such as mesoporous supports mainly rely on mass transfer limitation, and have limited effect on treating low concentrations of CO, making it difficult to adapt to the complex CO concentration scenarios in metallurgical flue gas; (3) The method of introducing CO2-loving groups to design competitive adsorption sites still fails to change the intrinsic characteristic that CO adsorption energy is higher than that of CO2, and cannot completely solve the contradiction of adsorption competition between CO and active sites.

[0004] In current research in this field, some schemes use precious metals (such as Pd, Pt, Ru, etc.) as active components and load them on the surface of a support. Although such catalysts can achieve strong resistance to CO poisoning and high catalytic activity, precious metal resources are scarce and expensive. Large-scale industrial applications will significantly increase the preparation cost of the catalyst, thus limiting its industrial promotion.

[0005] Therefore, developing a composite catalyst that combines high activity, strong resistance to CO poisoning, excellent stability, and simple and low-cost preparation process has become an urgent technical problem to be solved in the field of CO2 resource utilization. Summary of the Invention

[0006] To address the problems of catalysts being easily poisoned and deactivated in CO-containing atmospheres, high dependence on precious metals, and the difficulty in balancing anti-poisoning performance and catalytic activity in non-precious metal catalysts, this invention provides a single-atom Mo-supported hollow titanium dioxide sphere, its preparation method, and its applications. This invention significantly improves the photoreduction activity and CO poisoning resistance in low-concentration CO2 through the synergistic effect of electronic modulation of Mo atoms and the spatial confinement of the hollow titanium dioxide spheres, making it particularly suitable for the resource utilization of CO2 from CO-containing metallurgical flue gas.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing single-atom Mo-supported hollow titanium dioxide spheres, the method comprising the following steps:

[0009] S1, Disperse carbon template spheres in water to obtain a carbon template sphere dispersion; Adjust the pH of the carbon template sphere dispersion to weakly acidic, and perform solid-liquid separation to obtain positively charged carbon template spheres;

[0010] S2, add the titanium source to the alcohol solvent, then add the acidic chelating agent and water in sequence, and pre-hydrolyze to obtain negatively charged TiO2 sol;

[0011] S3, the positively charged carbon template spheres are dispersed in an alcohol solvent, the negatively charged TiO2 sol is added, the mixture is mixed evenly and allowed to stand, the solid and liquid are separated, dried, and calcined to remove the carbon template spheres to obtain TiO2 hollow spheres;

[0012] S4, the TiO2 hollow spheres and molybdenum source are dispersed in n-octanol and subjected to a solvothermal reaction to obtain single-atom Mo-supported titanium dioxide hollow spheres.

[0013] Compared to existing technologies, the method for preparing single-atom Mo-supported hollow titanium dioxide spheres provided by this invention involves stepwise control of the charge properties of the carbon template spheres and TiO2 sol, enabling electrostatic interactions between the positively charged carbon template spheres and the negatively charged TiO2 sol. This electrostatic assembly effect achieves a uniform and dense coating of TiO2 on the surface of the carbon template spheres. Subsequently, calcination removes the carbon template, yielding TiO2 hollow spheres with complete morphology and uniform shell thickness. This hollow structure not only increases the specific surface area and provides sufficient active sites but also improves mass transfer efficiency, alleviating the problem of slow reaction kinetics at low temperatures. Simultaneously, during the rapid oxidation and removal of the carbon template, the TiO2 hollow... The surface of the core sphere generates abundant surface oxygen vacancies in situ. These oxygen vacancies can serve as ideal anchoring sites, providing a structural basis for the stable loading of Mo single atoms and effectively solving the problems of easy agglomeration and unstable loading of single-atom active components. Furthermore, using n-octanol as a high-boiling-point coordination solvent for a solvothermal reaction, Mo was successfully and stably anchored in the TiO2 lattice in single-atom form by utilizing its steric hindrance effect and coordination synergy, forming a Mo-O-Ti local electronic structure. This local electronic structure can enhance the electron transfer efficiency between the Mo active sites and the TiO2 support, significantly improving the catalyst's resistance to CO poisoning and CO2 catalytic conversion activity.

[0014] The single-atom Mo-supported titanium dioxide hollow spheres prepared by this invention have both excellent stability and applicability, and can be adapted to the complex scenario of high concentration CO in metallurgical flue gas, providing feasible technical support for the industrial promotion of CO2 low-temperature catalytic conversion technology.

[0015] As a specific embodiment of the present invention, the method for preparing the carbon template spheres specifically includes the following steps:

[0016] Dissolve glucose in water to obtain a glucose solution;

[0017] The pH of the glucose solution was adjusted to weakly alkaline, and a hydrothermal reaction was carried out at 170℃~190℃. After solid-liquid separation, washing, and drying, carbon template spheres were obtained.

[0018] Furthermore, the concentration of the glucose solution is 0.5 mol / L to 0.6 mol / L.

[0019] Furthermore, the term "weakly alkaline" refers to a pH value of 9.5 to 10.5.

[0020] Specifically, the pH was adjusted to 9.5-10.5 using an aqueous sodium hydroxide solution.

[0021] Furthermore, the hydrothermal reaction time is 3 to 4 hours.

[0022] The carbon templates prepared by the above method have regular spherical morphology and good dispersibility, and can be used as ideal templates for subsequent uniform coating of TiO2, further ensuring the structural and performance stability of the final catalyst.

[0023] Furthermore, in S1, the mass-to-volume ratio of the carbon template sphere to water is (100~300) mg: (10~30) mL.

[0024] Further, in S1, the weak acidity refers to the pH value of the carbon template ball dispersion being 3~4.

[0025] Specifically, the pH value is adjusted to 3-4 using a 0.1mol / L~0.2mol / L hydrochloric acid solution.

[0026] Further, in S1, after adjusting the pH of the carbon template ball dispersion to weakly acidic, the mixture is stirred for 15 min to 30 min.

[0027] Furthermore, in S2, the titanium source is tetrabutyl titanate.

[0028] Furthermore, in S2, the alcohol solvent is anhydrous ethanol.

[0029] Furthermore, in S2, the acidic chelating agent is glacial acetic acid.

[0030] Furthermore, in S2, the ratio of the titanium source to the alcohol solvent is (5~8) mmol:10mL.

[0031] Furthermore, in S2, the ratio of the titanium source to the acidic chelating agent is (5~8) mmol: (0.1~0.3) mL.

[0032] Furthermore, in S2, the ratio of the titanium source to water is (5~8) mmol: (0.5~1.0) mL.

[0033] Furthermore, in S2, the pre-hydrolysis temperature is 40℃~50℃, and the time is 2h~3h.

[0034] The optimal pre-hydrolysis temperature and time ensure that the titanium source is fully hydrolyzed to form a uniformly dispersed and stable negatively charged TiO2 sol, thus ensuring the electrostatic attraction coating effect between the sol and the positively charged carbon template spheres.

[0035] Furthermore, in S3, the alcohol solvent is anhydrous ethanol.

[0036] Furthermore, in S3, the mass-to-volume ratio of the positively charged carbon template sphere to the alcohol solvent is (3~5) mg:1 mL.

[0037] Furthermore, in S3, the mass ratio of the negatively charged TiO2 sol to the positively charged carbon template spheres is (1.5~3):1.

[0038] Within the aforementioned preferred range, it is possible to ensure that the TiO2 sol forms a complete and moderately thick coating layer on the surface of the carbon template sphere, while retaining a rich mesoporous structure, which is beneficial for the subsequent anchoring of Mo single atoms and mass transfer and diffusion during the reaction process.

[0039] Specifically, in S3, the negatively charged TiO2 sol is added dropwise, and after the addition is complete, it is stirred for 1 to 3 hours and then allowed to stand for 2 to 3 hours.

[0040] Specifically, in S3, the drying is carried out by vacuum freeze drying, with a freeze drying temperature of -70℃ to -50℃, a vacuum degree of 2Pa to 4Pa, and a drying time of 20h to 24h.

[0041] Furthermore, in S3, the calcination temperature is 400℃~500℃, and the calcination time is 2h~4h.

[0042] Furthermore, the heating rate is 1℃ / min to 3℃ / min.

[0043] Under these calcination conditions, the carbon template can be fully oxidized and removed to form a complete hollow spherical shell structure, while avoiding the excessive transformation of TiO2 crystal form from anatase to rutile or the collapse of the sintered shell due to excessive temperature. In addition, this temperature range is conducive to the in-situ generation of abundant and stable surface oxygen vacancies during the rapid oxidation and removal of the carbon template, providing key capture sites for the subsequent chemical anchoring of Mo single atoms.

[0044] Furthermore, in S4, the molybdenum source is ammonium molybdate.

[0045] Furthermore, in S4, the molar ratio of Mo in the molybdenum source to Ti in the TiO2 hollow sphere is (0.005~0.02):1.

[0046] Within the above-mentioned ratio range, high-density loading of Mo single-atom sites can be achieved while avoiding the aggregation of Mo atoms, thus balancing catalytic activity and anti-poisoning performance.

[0047] Furthermore, in S4, the temperature of the solvothermal reaction is 180℃~200℃, and the reaction time is 20h~24h.

[0048] Secondly, the present invention also provides a single-atom Mo-supported hollow titanium dioxide sphere, wherein the material is prepared by the preparation method of the single-atom Mo-supported hollow titanium dioxide sphere described in any one of the above claims.

[0049] Thirdly, the present invention also provides the application of the above-mentioned single-atom Mo-supported titanium dioxide hollow spheres as a catalyst for the catalytic conversion of CO2 in a CO-containing atmosphere.

[0050] The applications include, but are not limited to, CO2 hydrogenation to methanol, methanation, or reverse water-gas shift reaction.

[0051] This invention anchors atomically dispersed Mo sites within a TiO2 lattice, utilizing the hybridization of unoccupied d orbitals of Mo atoms with oxygen orbitals in the TiO2 lattice to construct localized electron-trapping states around the active sites. This electronic state modulation, on the one hand, makes the Mo sites exhibit a strong affinity for CO2 molecules, promoting CO2 activation and bending configuration transformation; on the other hand, due to the weak d-π* backbonding of CO products at the Mo sites, the adsorption energy of CO molecules at the active sites is significantly reduced, thereby suppressing strong CO adsorption and occupation at the electronic level, achieving intrinsic anti-CO poisoning properties.

[0052] Meanwhile, the internal cavity of the hollow TiO2 forms a micro / nano reactor, which has a significant enrichment effect on low-concentration CO2 molecules, enhancing the gas-solid phase mass transfer process by prolonging the residence time of CO2 molecules around the active sites. In addition, the inherent mesoporous channels of the hollow spherical shell, through geometric constraint effect, exert differentiated diffusion barriers on CO and CO2 molecules, preferentially blocking the reverse diffusion and re-adsorption of CO, thus achieving anti-poisoning performance at the spatial level.

[0053] In summary, this invention inhibits CO from occupying the active site at the adsorption energy level by electronically modulating the Mo sites, while simultaneously hindering CO from approaching the active site at the mass transfer level by utilizing the hollow confinement structure of TiO2. The synergistic effect of these two methods significantly improves the stability and selectivity of the catalyst in a low-concentration CO2 atmosphere. Experiments show that in a simulated industrial low-concentration CO2 atmosphere (15% CO2 volume fraction), the catalyst's activity did not significantly decrease after 16 hours of continuous reaction, and no obvious CO poisoning deactivation was observed at the Mo sites after the reaction. This demonstrates that the catalyst of this invention has broad application prospects and industrial promotion value in the fields of CO2 resource utilization from CO-containing industrial tail gas and syngas purification. Attached Figure Description

[0054] Figure 1 The image shows a scanning electron microscope (SEM) image of the carbon template spheres prepared in step a of Example 2.

[0055] Figure 2 XRD patterns of TiO2 hollow spheres and Mo / TiO2 hollow spheres prepared in Example 2;

[0056] Figure 3 Transmission electron microscope (TEM) image of the TiO2 hollow spheres prepared in Example 2;

[0057] Figure 4 High-resolution high-angle annular dark-field scanning transmission electron microscope (HRTEM-HADDF) image of the TiO2 hollow spheres prepared in Example 2;

[0058] Figure 5 Aberration-corrected transmission electron microscope (AC-TEM) image of the Mo / TiO2 hollow spheres prepared in Example 2;

[0059] Figure 6 The graph shows a comparison of the catalytic performance of the Mo / TiO2 hollow spheres prepared in Example 2 under conditions of no light, no catalyst, argon gas as a substitute for the reaction gas, and anhydrous conditions.

[0060] Figure 7 The image shows a photocatalytic reduction cycle test of CO2 by the Mo / TiO2 hollow spheres prepared in Example 2. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0062] As a specific embodiment of the present invention, this embodiment provides a method for preparing single-atom Mo-supported hollow titanium dioxide spheres, comprising the following steps:

[0063] S1, Disperse carbon template spheres in water to obtain a carbon template sphere dispersion; Adjust the pH of the carbon template sphere dispersion to weakly acidic, and perform solid-liquid separation to obtain positively charged carbon template spheres;

[0064] S2, add the titanium source to the alcohol solvent, then add the acidic chelating agent and water in sequence, and pre-hydrolyze to obtain negatively charged TiO2 sol;

[0065] S3, the positively charged carbon template spheres are dispersed in an alcohol solvent, the negatively charged TiO2 sol is added, the mixture is mixed evenly and allowed to stand, the solid and liquid are separated, dried, and calcined to remove the carbon template spheres to obtain TiO2 hollow spheres;

[0066] S4, the TiO2 hollow spheres and molybdenum source are dispersed in n-octanol and subjected to a solvothermal reaction to obtain single-atom Mo-supported titanium dioxide hollow spheres.

[0067] The above method uses an electrostatic assembly strategy to uniformly coat negatively charged TiO2 sol onto positively charged carbon template spheres. After calcination to remove the template, oxygen-vacancy-rich hollow TiO2 spheres are obtained. Then, using n-octanol as a solvent, Mo is anchored in the TiO2 lattice in single-atom form via a solvothermal method, forming a Mo-O-Ti localized electronic structure. This invention utilizes the electronic regulation of Mo single atoms to suppress the strong adsorption of CO to active sites at the adsorption energy level, endowing the catalyst with intrinsic resistance to CO poisoning. Simultaneously, the confinement effect of the hollow TiO2 spheres enhances the enrichment and mass transfer of low-concentration CO2, and further blocks CO re-adsorption through sieving of shell pore size. The synergistic effect of electronic regulation and structural confinement significantly improves the catalyst's CO2 photoreduction activity and long-term stability in CO-containing atmospheres. This method is simple, low-cost, and has high atom utilization, showing broad application prospects in the resource utilization of CO2 from iron and steel metallurgical flue gas, syngas purification, and biogas purification.

[0068] To better illustrate the present invention, further examples are provided below.

[0069] Example 1

[0070] This embodiment provides a method for preparing single-atom Mo-supported hollow titanium dioxide spheres, comprising the following steps:

[0071] Step a: Dissolve anhydrous glucose in deionized water to obtain a glucose solution with a concentration of 0.5 mol / L; slowly add 0.5 mol / L NaOH solution to the glucose solution to adjust the pH to 9.5; transfer the solution to a hydrothermal reactor and react at 170℃ for 4 hours; allow it to cool naturally to room temperature; centrifuge, wash, and dry to obtain carbon template spheres.

[0072] Step b: Disperse 100 mg of the carbon template spheres prepared above in 10 mL of deionized water, adjust the pH to 3 with 0.1 mol / L hydrochloric acid solution, stir for 15 min, centrifuge, and dry to obtain positively charged carbon template spheres;

[0073] Step c: Add 5 mmol of tetrabutyl titanate to 10 mL of anhydrous ethanol, add 0.1 mL of glacial acetic acid, stir for 10 min, add 0.5 mL of deionized water, and pre-hydrolyze at 40 °C for 3 h to obtain negatively charged TiO2 sol.

[0074] Step d: The positively charged carbon template spheres prepared above are dispersed in anhydrous ethanol at a concentration of 3 mg / mL. Negatively charged TiO2 sol is added under vigorous stirring. The mass ratio of negatively charged TiO2 sol to positively charged carbon template spheres is 1.5:1. After stirring for 1 h, the mixture is allowed to stand for 2 h and centrifuged. The resulting solid is freeze-dried at -50℃ and 2 Pa for 24 h. The freeze-dried product is then placed in a muffle furnace and calcined at 400℃ for 4 h at a rate of 1℃ / min to obtain TiO2 hollow spheres.

[0075] Step e: The TiO2 hollow spheres and ammonium molybdate prepared above are dispersed in 10 mL of n-octanol at a Ti / Mo molar ratio of 1:0.005. The dispersion is ultrasonically uniform, transferred to a high-pressure reactor, and reacted at 180 °C for 24 h. After centrifugation, washing, and drying, single-atom Mo-supported titanium dioxide hollow spheres are obtained, denoted as Mo / TiO2 hollow spheres.

[0076] Example 2

[0077] This embodiment provides a method for preparing single-atom Mo-supported hollow titanium dioxide spheres, comprising the following steps:

[0078] Step a: Dissolve anhydrous glucose in deionized water to obtain a glucose solution with a concentration of 0.55 mol / L; slowly add 0.5 mol / L NaOH solution to the glucose solution to adjust the pH to 10.0; transfer the solution to a hydrothermal reactor and react at 180℃ for 3.5 h; allow it to cool naturally to room temperature; centrifuge, wash, and dry to obtain carbon template spheres.

[0079] Step b: Disperse 200 mg of the carbon template spheres prepared above in 20 mL of deionized water, adjust the pH to 3.5 with 0.1 mol / L hydrochloric acid solution, stir for 20 min, centrifuge, and dry to obtain positively charged carbon template spheres;

[0080] Step c: Add 7 mmol of tetrabutyl titanate to 10 mL of anhydrous ethanol, add 0.2 mL of glacial acetic acid, stir for 10 min, add 0.8 mL of deionized water, and pre-hydrolyze at 45 °C for 2.5 h to obtain negatively charged TiO2 sol.

[0081] Step d: The positively charged carbon template spheres prepared above are dispersed in anhydrous ethanol at a concentration of 4 mg / mL. Negatively charged TiO2 sol is added under vigorous stirring. The mass ratio of negatively charged TiO2 sol to positively charged carbon template spheres is 2:1. After stirring for 2 h, the mixture is allowed to stand for 2.5 h and centrifuged. The resulting solid is freeze-dried at -60℃ and 3 Pa for 22 h. The freeze-dried product is then placed in a muffle furnace and calcined at 450℃ for 3 h at a rate of 2℃ / min to obtain TiO2 hollow spheres.

[0082] Step e: The TiO2 hollow spheres and ammonium molybdate prepared above are dispersed in 20 mL of n-octanol at a Ti / Mo molar ratio of 1:0.01. The dispersion is ultrasonically uniform, transferred to a high-pressure reactor, and reacted at 190 °C for 22 h. After centrifugation, washing, and drying, single-atom Mo-supported titanium dioxide hollow spheres are obtained, denoted as Mo / TiO2 hollow spheres.

[0083] Example 3

[0084] This embodiment provides a method for preparing single-atom Mo-supported hollow titanium dioxide spheres, comprising the following steps:

[0085] Step a: Dissolve anhydrous glucose in deionized water to obtain a glucose solution with a concentration of 0.6 mol / L; slowly add 0.5 mol / L NaOH solution to the glucose solution to adjust the pH to 10.5; transfer the solution to a hydrothermal reactor and react at 190℃ for 3 hours; allow it to cool naturally to room temperature; centrifuge, wash, and dry to obtain carbon template spheres.

[0086] Step b: Disperse 300 mg of the carbon template spheres prepared above in 30 mL of deionized water, adjust the pH to 4 with 0.1 mol / L hydrochloric acid solution, stir for 30 min, centrifuge, and dry to obtain positively charged carbon template spheres;

[0087] Step c: Add 8 mmol of tetrabutyl titanate to 10 mL of anhydrous ethanol, add 0.3 mL of glacial acetic acid, stir for 10 min, add 1.0 mL of deionized water, and pre-hydrolyze at 50 °C for 2 h to obtain negatively charged TiO2 sol.

[0088] Step d: The positively charged carbon template spheres prepared above are dispersed in anhydrous ethanol at a concentration of 5 mg / mL. Negatively charged TiO2 sol is added under vigorous stirring. The mass ratio of negatively charged TiO2 sol to positively charged carbon template spheres is 3:1. After stirring for 3 h, the mixture is allowed to stand for 3 h and centrifuged. The resulting solid is freeze-dried at -70 °C and 4 Pa ​​for 20 h. The freeze-dried product is then placed in a muffle furnace and calcined at 500 °C for 2 h at a rate of 3 °C / min to obtain TiO2 hollow spheres.

[0089] Step e: The TiO2 hollow spheres and ammonium molybdate prepared above are dispersed in 30 mL of n-octanol at a Ti / Mo molar ratio of 1:0.02. The dispersion is ultrasonically uniform, transferred to a high-pressure reactor, and reacted at 200 °C for 20 h. After centrifugation, washing, and drying, single-atom Mo-supported titanium dioxide hollow spheres are obtained, denoted as Mo / TiO2 hollow spheres.

[0090] Structural and morphological characterization

[0091] Figure 1The image shows a scanning electron microscope (SEM) image of the carbon template spheres prepared in step a of Example 2. As can be seen from the image, the particle size distribution of the carbon template spheres is 0.4~1μm, and the morphology is relatively uniform.

[0092] Figure 2 The XRD patterns of TiO2 hollow spheres and Mo / TiO2 hollow spheres prepared in Example 2 are shown. The characteristic peaks of the TiO2 hollow spheres in the figure are in perfect agreement with the anatase TiO2 standard card (PDF#73-1764), indicating that anatase TiO2 was successfully prepared. Meanwhile, the Mo / TiO2 hollow spheres retain the characteristic diffraction peaks of TiO2 at positions 25.4°, 37.1°, and 48.2°, and no diffraction peaks belonging to metallic Mo are observed, indicating that Mo species are highly dispersed on the TiO2 surface, or that their loading is low and does not reach the XRD detection limit.

[0093] Figure 3 and Figure 4 The images show transmission electron microscopy (TEM) and high-resolution high-angle annular dark-field scanning transmission electron microscopy (HRTEM-HADDF) images of the TiO2 hollow spheres prepared in Example 2. The images clearly show the uniform hollow sphere structure and abundant mesoporous channels. The particle size distribution of the hollow spheres is in the range of 100–200 nm. This structure provides a favorable structural basis for multiple reflections of light and the diffusion transport of reactant molecules.

[0094] Figure 5 The image shown is an aberration-corrected transmission electron microscope (AC-TEM) image of the Mo / TiO2 hollow spheres prepared in Example 2. It can be seen that the catalyst still maintains the complete hollow sphere structure after being loaded with Mo.

[0095] Comparative Example 1

[0096] This comparative example provides a method for preparing single-atom Mo-supported hollow titanium dioxide spheres, which differs from Example 2 only in that it uses a solvent etching method, and includes the following steps:

[0097] Step a: Dissolve anhydrous glucose in deionized water to obtain a glucose solution with a concentration of 0.55 mol / L; slowly add 0.5 mol / L NaOH solution to the glucose solution to adjust the pH to 10.0; transfer the solution to a hydrothermal reactor and react at 180℃ for 3.5 h; allow it to cool naturally to room temperature; centrifuge, wash, and dry to obtain carbon template spheres.

[0098] Step b: Disperse 200 mg of the carbon template spheres prepared above in 20 mL of anhydrous ethanol, sonicate for 1 min, then place the dispersion on a magnetic stirrer and stir for 1 h. Then add 7 mmol of tetrabutyl titanate and continue stirring for 2 h. Then let it stand at room temperature for 24 h to age, collect the precipitate, centrifuge and wash 3 times with anhydrous ethanol, and dry in a vacuum drying oven at 60 °C for 5 h to obtain CS@TiO2 powder.

[0099] Step c: Disperse the CS@TiO2 powder prepared above in 0.5 mol / L NaOH solution, stir for 12 h in a water bath at 80 °C, centrifuge, collect the precipitate, wash with deionized water until neutral, wash three times with anhydrous ethanol, dry the obtained product in a vacuum drying oven at 80 °C for 4 h, place it in a muffle furnace, and calcine it at 450 °C for 3 h at a rate of 2 °C / min to obtain TiO2 hollow spheres;

[0100] In step d, the TiO2 hollow spheres and ammonium molybdate prepared above were dispersed in 20 mL of n-octanol at a Ti / Mo molar ratio of 1:0.01. The dispersion was ultrasonically uniform, transferred to a high-pressure reactor, and reacted at 190 °C for 22 h. After centrifugation, washing, and drying, single-atom Mo-supported titanium dioxide hollow spheres were obtained, denoted as Mo / TiO2 hollow spheres.

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing single-atom Ni-supported hollow titanium dioxide spheres, which differs from Example 2 only in the loading of the active metal element. Specifically, it includes the following steps:

[0103] Steps a to d are the same as in Example 2, and will not be repeated here;

[0104] Step e: The TiO2 hollow spheres and nickel acetate tetrahydrate prepared above are dispersed in 20 mL of n-octanol at a Ti / Ni molar ratio of 1:0.01. The dispersion is ultrasonically uniform, transferred to a high-pressure reactor, and reacted at 190 °C for 22 h. After centrifugation, washing, and drying, single-atom Ni-supported titanium dioxide hollow spheres are obtained, denoted as Ni / TiO2 hollow spheres.

[0105] Comparative Example 3

[0106] This comparative example provides a method for preparing single-atom Co-supported hollow titanium dioxide spheres, which differs from Example 2 only in the loading of the active metal element. The specific steps include:

[0107] Steps a to d are the same as in Example 2, and will not be repeated here;

[0108] Step e: The TiO2 hollow spheres and cobalt nitrate hexahydrate prepared above are dispersed in 20 mL of n-octanol at a Ti / Co molar ratio of 1:0.01. The dispersion is ultrasonically uniform, transferred to a high-pressure reactor, and reacted at 190 °C for 22 h. After centrifugation, washing, and drying, single-atom Co-supported titanium dioxide hollow spheres are obtained, denoted as Co / TiO2 hollow spheres.

[0109] Performance testing

[0110] Take 10 mg of the catalyst prepared in Examples 1-3 and Comparative Examples 1-3 above and place it in a 100 mL gas-phase reactor. Add 5 mL of deionized water, seal the reaction system, and evacuate for 20 min. Then, backfill with reaction gas (65% CO, 15% CO2, 20% Ar). Repeat this process three times to ensure that the reactor is under atmospheric pressure. Turn on the circulating condensate system to maintain a stable reaction temperature. Use a 300 W xenon lamp as the light source and irradiate the reaction for 1 h. Then, extract the reaction gas from the device. Inject 1 mL of the reaction gas into a gas chromatograph for analysis. H2, O2, N2, etc., are detected using a TCD detector, while CO, CH4, etc., are detected using an FID detector. Qualitative analysis of the products is performed based on retention time, and quantitative analysis of the products is performed using a commercially available standard gas mixture.

[0111] The yield and selectivity are calculated using the following formula, where R (μmol / g / h) refers to the amount of product generated per gram of catalyst per unit time under light irradiation.

[0112]

[0113] The product concentration is expressed in μmol, the light irradiation reaction time in h, and the mass of catalyst added in the reaction in g.

[0114] Testing showed that, using the catalyst prepared in Example 2 of this invention, after photocatalytic reaction in a simulated industrial atmosphere (65% CO, 15% CO2, 20% Ar), the CO concentration in the outlet gas increased from the initial 65% to 69.2%, indicating that CO2 was effectively converted into CO, thereby significantly increasing the calorific value of the mixed gas. This demonstrates that the catalyst of this invention exhibits high CO2 conversion rate, low CO adsorption capacity, and good operational stability under these reaction conditions.

[0115] The results of CO and CH4 yields in the photocatalytic reduction of CO2 in each embodiment and comparative example are shown in Table 1.

[0116] Table 1. Performance tests of photocatalytic CO2 reduction in examples and comparative cases.

[0117]

[0118] To verify the photocatalytic performance of the catalyst and its condition-dependent effects, a control experiment was set up to examine the performance of the reaction system under conditions of no light, no catalyst, argon gas instead of reactant gas, and anhydrous conditions. All other conditions in the control experiments were the same as those in the aforementioned photocatalytic CO2 reduction performance test experiments. The test results are shown in Table 2 and... Figure 6 As shown.

[0119] Table 2 Control Experiment

[0120]

[0121] Experimental results show that no CH4 or CO was detected under conditions of no light, no catalyst, and argon gas as a substitute for the reactant gas. Under anhydrous conditions, although no CH4 was detected, trace amounts of CO were detected. This indicates that water plays a crucial role in the reduction and conversion of CO2 in the reaction system, while light and a catalyst are necessary conditions for effective catalytic reduction.

[0122] The Mo / TiO2 hollow sphere catalyst prepared in Example 2 was subjected to four cycles of stability testing under the same conditions as the aforementioned photocatalytic reduction of CO2 performance test. Each cycle involved 4 hours of light irradiation. The test results are shown in Table 3 and... Figure 7 As shown.

[0123] Table 3 Cyclic Experiment

[0124]

[0125] The results showed that after four cycles, the CO2 conversion rate and CO product selectivity of the catalyst did not decrease significantly and maintained high catalytic activity, proving that the composite catalyst has good cycle stability and anti-deactivation ability.

[0126] In summary, this invention addresses two core technical challenges in the photoreduction of CO2 in converter gas: limited mass transfer and CO poisoning. It designs and synthesizes an atomically dispersed Mo-anchored hollow TiO2 nanosphere photocatalyst. On one hand, local electronic state modulation is achieved through Mo single-atom doping, endowing the catalyst with intrinsic CO poisoning resistance at the electronic level, thereby enhancing its catalytic performance in a converter gas atmosphere. On the other hand, the hollow nanosphere structure constructs a unique micro-nano confined space, physically enhancing the rapid enrichment and efficient mass transfer of low-concentration CO2. Simultaneously, the size sieving effect of the shell channels further suppresses CO re-adsorption during the reaction, alleviating CO occupation of catalytic active sites. Through the synergistic effect of electronic modulation and spatial confinement, efficient activation and highly selective conversion of low-concentration CO2 in converter gas are achieved, while simultaneously endowing the catalyst with excellent anti-poisoning stability and long-term cycling performance. This invention not only provides a practical and feasible technical path for the efficient utilization of CO2 in converter gas, but also provides a brand-new idea and method for the design and preparation of CO poisoning resistant photocatalysts, which has important theoretical guiding significance and industrial application value.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing monatomic Mo loaded titanium dioxide hollow spheres, characterized in that, Includes the following steps: S1, Disperse carbon template spheres in water to obtain a carbon template sphere dispersion; Adjust the pH of the carbon template sphere dispersion to weakly acidic, and perform solid-liquid separation to obtain positively charged carbon template spheres; S2, add the titanium source to the alcohol solvent, then add the acidic chelating agent and water in sequence, and pre-hydrolyze to obtain negatively charged TiO2 sol; S3, the positively charged carbon template spheres are dispersed in an alcohol solvent, the negatively charged TiO2 sol is added, the mixture is mixed evenly and allowed to stand, the solid and liquid are separated, dried, and calcined to remove the carbon template spheres to obtain TiO2 hollow spheres; S4, the TiO2 hollow spheres and molybdenum source are dispersed in n-octanol and subjected to a solvothermal reaction to obtain single-atom Mo-supported titanium dioxide hollow spheres.

2. The method for preparing monatomic Mo supported titanium dioxide hollow spheres according to claim 1, characterized in that, The preparation method of the carbon template spheres specifically includes the following steps: Dissolve glucose in water to obtain a glucose solution; The pH of the glucose solution was adjusted to weakly alkaline, and a hydrothermal reaction was carried out at 170℃~190℃. After solid-liquid separation, washing, and drying, carbon template spheres were obtained.

3. The method for preparing monatomic Mo supported titanium dioxide hollow spheres according to claim 2, characterized in that, The concentration of the glucose solution is 0.5 mol / L to 0.6 mol / L; and / or The term "weakly alkaline" refers to a pH value of 9.5 to 10.5; and / or The hydrothermal reaction takes 3 to 4 hours.

4. The method for preparing monatomic Mo supported titanium dioxide hollow spheres according to claim 1, characterized in that, In S1, the mass-to-volume ratio of the carbon template spheres to water is (100~300) mg:(10~30) mL; and / or In S1, the weak acidity refers to the pH value of the carbon template sphere dispersion being 3~4; and / or In step S1, after adjusting the pH of the carbon template ball dispersion to a slightly acidic state, stir and mix for 15 to 30 minutes.

5. The method for preparing single-atom Mo-supported hollow titanium dioxide spheres as described in claim 1, characterized in that, In S2, the titanium source is tetrabutyl titanate; and / or In S2, the alcohol solvent is anhydrous ethanol; and / or In S2, the acidic chelating agent is glacial acetic acid.

6. The method for preparing single-atom Mo-supported hollow titanium dioxide spheres as described in claim 1 or 5, characterized in that, In S2, the ratio of the titanium source to the alcohol solvent is (5~8) mmol:10mL; and / or In S2, the ratio of the titanium source to the acidic chelating agent is (5~8) mmol:(0.1~0.3) mL; and / or In S2, the ratio of the titanium source to water is (5~8) mmol:(0.5~1.0) mL; and / or In S2, the pre-hydrolysis temperature is 40℃~50℃ and the time is 2h~3h.

7. The method for preparing single-atom Mo-supported hollow titanium dioxide spheres as described in claim 1, characterized in that, In S3, the alcohol solvent is anhydrous ethanol; and / or In S3, the mass ratio of the negatively charged TiO2 sol to the positively charged carbon template spheres is (1.5~3):1; and / or In S3, the calcination temperature is 400℃~500℃, and the calcination time is 2h~4h.

8. The method for preparing single-atom Mo-supported hollow titanium dioxide spheres as described in claim 1, characterized in that, In S4, the molybdenum source is ammonium molybdate; and / or In S4, the molar ratio of Mo in the molybdenum source to Ti in the TiO2 hollow spheres is (0.005~0.02):1; and / or In S4, the temperature of the solvothermal reaction is 180℃~200℃, and the reaction time is 20h~24h.

9. A single-atom Mo-supported hollow titanium dioxide sphere, characterized in that, It is prepared by the method for preparing single-atom Mo-supported titanium dioxide hollow spheres according to any one of claims 1 to 8.

10. The application of the single-atom Mo-supported titanium dioxide hollow spheres as described in claim 9 as a catalyst for the catalytic conversion of CO2 in a CO-containing atmosphere.

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