A hollow core-shell Cu / TiO2 catalyst based on Murray's law, its preparation method and application

Abstract

The application discloses a hollow core-shell structure Cu / TiO2 catalyst based on a Murray-like law and a preparation method and application thereof, and belongs to the technical field of plasma catalysis and carbon dioxide resource utilization. The catalyst is a spherical hierarchical structure with a hollow interior and a mesoporous shell layer, the shell layer is composed of a TiO2 skeleton and a Cu active component, and the ratio of the cavity diameter to the shell layer thickness Dc / Ls is 2.6-4.0. The catalyst is prepared by adopting a SiO2 hard template, through shell coating, Cu component loading, meso-structurization, calcination and alkali etching to remove the core. The catalyst is used for a dielectric barrier discharge assisted reverse water gas shift reaction, shortens a mass transfer path of plasma active species, strengthens a local electric field and active species enrichment, improves CO2 conversion rate and energy utilization efficiency, and is suitable for CO2 hydrogenation resource conversion.

Description

Technical Field

[0001] This invention belongs to the field of plasma catalysis and carbon dioxide resource utilization technology, specifically relating to a hollow core-shell Cu / TiO2 catalyst based on Murray's law, its preparation method and application. Background Technology

[0002] The greenhouse effect caused by excessive CO2 emissions, along with the continued increase in global energy and environmental pressures, has driven the rapid development of CO2 resource utilization technologies. The CO2 molecule has a linear structure and high thermodynamic stability; the C=O bond energy is approximately 750 kJ / mol, and its direct activation requires a large energy input. The reverse water-gas shift reaction (RWGS) can convert CO2 into the platform molecule CO, serving as an important pathway connecting CO2 utilization with downstream Fischer-Tropsch synthesis and syngas chemistry.

[0003] Traditional RWGS thermocatalysis typically relies on bulk heating to overcome the energy barriers of CO2 activation and surface reactions. This high reaction temperature easily leads to catalyst sintering and deactivation, resulting in limited energy utilization efficiency. Non-thermal plasma (NTP) technologies, such as dielectric barrier discharge (DBD), can activate molecules through high-energy electron collisions at lower gas temperatures. However, the core challenge for further development of NTP-assisted RWGS systems lies in how to maintain the advantages of non-equilibrium plasma activation while improving the utilization efficiency of active species generated by discharge at the interface through rational catalyst design.

[0004] Currently, catalyst design in DBD plasma-catalyst systems still follows traditional thermocatalysis principles, focusing on active site regulation, defect engineering, and metal-support interactions. However, unlike traditional thermocatalysis, molecular activation in plasma systems does not occur solely on the catalyst surface but is deeply coupled with gas-phase discharge, local electric field distribution, migration of key active species (such as vibrationally excited CO2(v)), and interfacial reaction processes. Existing solid or conventional porous catalysts cannot effectively coordinate the enrichment of the discharge space with mass transfer within the mesopores, causing short-lived active species to relax or quench before reaching the active site, severely limiting energy and mass conversion efficiency.

[0005] To address the aforementioned technical deficiencies, this invention proposes a hollow core-shell Cu / TiO2 catalyst based on Murray's law, along with its preparation method and applications. By cross-scale matching of the internal cavity, shell diffusion path, and mesoporous channels, efficient coupling of discharge activation and mass transfer reaction is achieved. Summary of the Invention

[0006] To address the technical problems of limited partial discharge space, long mass transfer distances for active species, and susceptibility to quenching in existing plasma catalysis systems, this invention proposes a hollow core-shell Cu / TiO2 catalyst based on Murray's law, its preparation method, and its applications. This invention achieves efficient coupling of discharge activation and mass transfer reactions through cross-scale geometric matching of the catalyst's internal cavity, shell diffusion path, and mesoporous channels. The objective of this invention is to provide a hollow core-shell Cu / TiO2 catalyst based on a Murray-like law, its preparation method, and its applications. This catalyst has a spherical hierarchical structure with a hollow interior and a continuous mesoporous shell on the outside. The outer shell consists of a TiO2 framework and Cu active components supported thereon. The key feature is that the ratio of the internal cavity diameter (Dc) to the shell thickness (Ls) is between 2.6 and 4.0. This ratio conforms to the optimal mass transport matching relationship revealed by the generalized Murray's law, minimizing the cross-shell mass transfer time.

[0007] The second objective of this invention is to provide a method for preparing the above-mentioned catalyst, which combines a hard template method with a confined growth strategy. The specific steps include: (1) synthesizing SiO2 nanosphere templates using tetraethyl orthosilicate as a precursor; (2) coating its surface with TiO2 to form a shell, and precisely controlling the shell thickness by adjusting the amount of titanium source; (3) loading copper-containing precursors using a urea-assisted deposition precipitation method; (4) introducing CTAB and PVP for mesoscopic structuring treatment, creating pores and improving surface accessibility; (5) calcining at 600℃ to stabilize the crystal form; (6) etching with NaOH solution at 90℃ for 6 hours to completely remove the internal SiO2 hard template, and obtaining a Cu / TiO2 catalyst (Thin sample) with thin shell and large cavity characteristics.

[0008] A third objective of this invention is to provide the application of this catalyst in nonthermal plasma (NTP) assisted reverse water-gas shift (RWGS) reactions. It catalyzes the reaction of CO2 with H2 to produce CO under a dielectric barrier discharge (DBD) system.

[0009] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A hollow core-shell Cu / TiO2 catalyst based on Murray's law, wherein the catalyst is a spherical hierarchical structure with a hollow interior and a mesoporous outer shell, the outer shell being composed of a TiO2 framework and Cu active components supported thereon, and the ratio of the internal cavity diameter to the shell thickness, Dc / Ls, of the catalyst is 2.6 to 4.0.

[0010] Further specified, the TiO2 shell has continuous mesoporous channels distributed in it, the mesoporous pore size dm is 8-12nm, and the nano-building unit size db of the TiO2 is 18-23nm.

[0011] Further specifying, the Cu active component is on the catalyst surface in the form of Cu 0 It exists in the chemical state of Cu⁺.

[0012] A method for preparing a hollow core-shell Cu / TiO2 catalyst based on a Murray-like law includes the following steps: S1 Synthesis of Hard Templates: Using tetraethyl orthosilicate as a precursor, SiO2 nanospheres were synthesized as hard templates. S2 shell coating: The SiO2 nanospheres are dispersed in a mixed system of ethanol, acetonitrile and ammonia, and hydrolysis is controlled by tetrabutyl titanate to coat the SiO2 surface with a TiO2 shell to obtain a SiO2@TiO2 core-shell intermediate; S3 Active Metal Loading: Using copper nitrate as a copper precursor and urea as a slow-release alkali agent, Cu components are introduced onto the shell surface of the intermediate through a urea-assisted deposition precipitation method. S4 mesoscopic structuring treatment: Hexadecyltrimethylammonium bromide and polyvinylpyrrolidone were added to improve shell porosity and surface accessibility. S5 calcination fixation: The treated material is calcined at 600℃ for 2 hours to stabilize the TiO2 framework and remove residual organic matter; S6 etching for core removal: The SiO2 core template was removed by etching with sodium hydroxide solution at 90°C for 6 hours. After washing and drying, a hollow core-shell Cu / TiO2 catalyst was obtained.

[0013] Further specifying that in S2, the thickness of the TiO2 shell is controlled by adjusting the amount of tetrabutyl titanate added, thereby controlling the final catalyst cavity-to-shell ratio Dc / Ls to be 2.6 to 4.0.

[0014] Application of a hollow core-shell Cu / TiO2 catalyst based on Murray's law in non-thermal plasma-assisted conversion of greenhouse gases.

[0015] Further specifying, the reaction is a dielectric barrier discharge-assisted reverse water-gas shift reaction, which converts CO2 and H2 into CO and water.

[0016] The beneficial effects of this invention are: Cross-scale geometric mass transfer optimization: The thin-shell hollow structure of the present invention (Dc / Ls between 2.6 and 4.0) constructs a hierarchical transport network of "internal cavity - mesoporous shell - outer surface", which greatly shortens the cross-shell diffusion path of gaseous molecules and plasma active species, and reduces the quenching loss of short-lived species such as vibrationally excited state CO2(v) during migration.

[0017] Enhanced coupling between discharge activation and interface enrichment: The hollow structure endows the catalyst with superior local dielectric response. Simulation and in-situ spectroscopy tests show that this structure can form a stronger and more continuous local high electric field region near the catalyst, significantly improving the enrichment density of near-surface active species CO2(v) and high-energy electrons.

[0018] Excellent catalytic performance and energy utilization: In a 50W input power atmospheric pressure plasma DBD system, the catalyst of this invention can achieve a CO2 conversion rate of up to 37.11%, which is significantly better than the thick-shell control group (31.77%) and the solid control group. (22.06%), and has excellent energy efficiency and good cycle stability. Attached Figure Description

[0019] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a schematic diagram of the preparation process of a hollow core-shell Cu / TiO2 catalyst based on a Murray-like law according to the present invention. Figure 2 The images show scanning electron microscope (SEM) and transmission electron microscope (TEM) images of a hollow core-shell structure Cu / TiO2 catalyst based on a Murray-like law, its preparation method, application examples, and comparative catalysts of this invention. Figure 3 The figures show the CO2 conversion rate and discharge power response of each catalyst in the plasma-assisted RWGS reaction in an example of a hollow core-shell Cu / TiO2 catalyst based on a Murray-like law, its preparation method, and its application. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0021] like Figure 1 As shown, this invention discloses a hollow core-shell Cu / TiO2 catalyst based on Murray's law, its preparation method, and its application. The catalyst is a spherical hierarchical structure with a hollow interior and a mesoporous shell. The outer shell is composed of a TiO2 framework and Cu active components supported thereon. The ratio of the internal cavity diameter to the shell thickness, Dc / Ls, of the catalyst is 2.6 to 4.0.

[0022] In the practical application of this embodiment, the TiO2 shell has continuous mesoporous channels distributed in it, the mesoporous pore size dm is 8-12nm, and the nano-building unit size db of the TiO2 is 18-23nm.

[0023] In the practical application of this embodiment, the Cu active component is in the form of Cu on the catalyst surface. 0 It exists in the chemical state of Cu⁺.

[0024] A method for preparing a hollow core-shell Cu / TiO2 catalyst based on a Murray-like law includes the following steps: S1 Synthesis of Hard Templates: Using tetraethyl orthosilicate as a precursor, SiO2 nanospheres were synthesized as hard templates. S2 shell coating: The SiO2 nanospheres are dispersed in a mixed system of ethanol, acetonitrile and ammonia, and hydrolysis is controlled by tetrabutyl titanate to coat the SiO2 surface with a TiO2 shell to obtain a SiO2@TiO2 core-shell intermediate; S3 Active Metal Loading: Using copper nitrate as a copper precursor and urea as a slow-release alkali agent, Cu components are introduced onto the shell surface of the intermediate through a urea-assisted deposition precipitation method. S4 mesoscopic structuring treatment: Hexadecyltrimethylammonium bromide and polyvinylpyrrolidone were added to improve shell porosity and surface accessibility. S5 calcination fixation: The treated material is calcined at 600℃ for 2 hours to stabilize the TiO2 framework and remove residual organic matter; S6 etching for core removal: The SiO2 core template was removed by etching with sodium hydroxide solution at 90°C for 6 hours. After washing and drying, a hollow core-shell Cu / TiO2 catalyst was obtained.

[0025] In the practical application of this embodiment, in step S2, the thickness of the TiO2 shell is controlled by adjusting the amount of tetrabutyl titanate added, thereby controlling the final catalyst cavity-to-shell ratio Dc / Ls to be 2.6 to 4.0.

[0026] Application of a hollow core-shell Cu / TiO2 catalyst based on Murray's law in nonthermal plasma (NTP)-assisted conversion of greenhouse gases.

[0027] In the practical application of this embodiment, the reaction is a dielectric barrier discharge (DBD) assisted reverse water-gas shift (RWGS) reaction, which converts CO2 and H2 into CO and water.

[0028] Example 1: Preparation of a thin-shell hollow Cu / TiO2 catalyst (labeled Thin) based on a Murray-like law S1 Synthesis of Hard Templates: Using tetraethyl orthosilicate (TEOS) as a precursor, SiO2 nanospheres with an average particle size of about 200 nm were synthesized as hard templates in an ethanol, ammonia, and water system via a modified Stöber method.

[0029] S2 Shell Coating: SiO2 nanospheres are ultrasonically dispersed in a mixture of ethanol, acetonitrile and ammonia, and tetrabutyl titanate (TBOT) is added. The hydrolysis rate is controlled to allow TiO2 to be uniformly deposited on the SiO2 surface, resulting in a SiO2@TiO2 core-shell intermediate. In this step, the amount of TBOT added is controlled to make the final shell thickness relatively thin.

[0030] S3 Active Metal Loading: The above intermediate is dispersed in water, and copper nitrate (Cu(NO3)2・3H2O) and 6wt% urea are added. The alkaline substances are slowly released by heating and decomposing the urea, and the Cu component is introduced into the shell.

[0031] S4 Mesoscopic Structuring Treatment: After centrifugation and washing, the product was treated in a solution of hexadecyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) to perform mesoscopic pore-forming structural modification of the shell, thereby improving the shell porosity and surface accessibility.

[0032] S5 calcination fixation: After washing and drying, the precursor is placed in a muffle furnace and calcined at 600℃ for 2 hours to remove residual organic matter and stabilize the TiO2 anatase crystal phase.

[0033] S6 Etching and Core Removal: The calcined powder was etched in a NaOH solution at 90°C for 6 hours to completely remove the SiO2 core template; after centrifugation and washing until neutral, it was pre-reduced under a hydrogen atmosphere to obtain a thin-shell hollow Cu / TiO2 catalyst. TEM characterization showed that the cavity diameter of the sample in this embodiment was approximately 140 nm, the shell thickness was approximately 30 nm, and the Dc / Ls ratio was between 2.6 and 4.0, conforming to the optimal transport matching trend similar to Murray's law; the BET specific surface area was 178 m² / g.

[0034] Comparative Example 1: Preparation of a thick-shell hollow Cu / TiO2 catalyst (labeled Thick) The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the amount of tetrabutyl titanate (TBOT) added in S2 is increased to significantly thicken the TiO2 shell.

[0035] Characterization results: The cavity diameter of the comparative sample is approximately 90 nm, the shell thickness is approximately 50 nm, and the Dc / Ls ratio is approximately 1.7 to 2.5, which deviates from the Murray-like law matching region; the BET specific surface area is 164 m² / g.

[0036] Comparative Example 2: Preparation of Solid Dense Cu / TiO2 Catalyst (labeled as Solid) Dense Cu / TiO2 nanoparticles were prepared directly via sol-gel and precipitation methods without using a SiO2 hard template, with calcination and pre-reduction conditions consistent with those in Example 1. This comparative sample exhibited no internal cavity structure and a BET specific surface area of ​​only 84 m² / g.

[0037] Test Example: DBD Plasma-Assisted RWGS Reaction Performance Evaluation The catalysts from Example 1 (Thin), Comparative Example 1 (Thick), and Comparative Example 2 (Solid) were respectively packed into the discharge zone of a coaxial dielectric barrier discharge (DBD) reactor. The reactor outer tube was a quartz tube with an outer diameter of 20 mm and an inner diameter of 16 mm (dielectric constant 3.7), the internal high-voltage electrode diameter was 8 mm, and the discharge gap was 4 mm. The feed gas CO2 / H2 molar ratio was 1:3, and the total flow rate was 80 mL / min; the system was maintained at room temperature and pressure; AC high voltage was applied to the electrode, and the discharge input power was controlled at 50 W; the products in the outlet gas were quantitatively analyzed using online gas chromatography.

[0038] like Figure 2 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the catalysts in the examples and comparative examples are shown. Among them, the Thin sample (Example 1) has a distinct thin shell layer (about 30 nm) and large cavity (about 140 nm) structure. The Thick sample (Comparative Example 1) has a thick shell (approximately 50 nm) and a small cavity (approximately 90 nm). The solid sample (Comparative Example 2) is a solid, dense sphere.

[0039] Test results are as follows Figure 3 As shown, Figure 3 This demonstrates the strongest conversion performance and sensitive response to input power of the thin-shell hollow catalyst; under the same 50W discharge power: The CO2 conversion rate of the solid, dense structure is 22.06%. The CO2 conversion rate of the thick-shell hollow structure was increased to 31.77%. The thin-shell hollow structure (Thin) with geometric parameter matching based on the Murray law of this invention has the highest CO2 conversion rate, reaching 37.11%, and the CO selectivity is maintained at an extremely high level.

[0040] Furthermore, in-situ emission spectroscopy (OES) and COMSOL multiphysics simulations show that the Thin configuration of Example 1 can generate the strongest local electric field (peak value 4.8 × 10⁻⁶) around its ultrathin shell and large pores. 6 The surface density of CO2 (v / m) is increased to 2.3 times that of the solid sample.

[0041] In summary, the thin-shell hollow Cu / TiO2 catalyst prepared by the hard template method in this invention, which conforms to the Murray-like matching characteristics, successfully coordinates multiple requirements such as gas buffer space, enhanced plasma partial discharge, rapid transport of excited-state species across the shell, and surface catalytic reaction, thereby significantly improving the decarbonization conversion efficiency of the plasma-co-catalyzed system.

[0042] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A hollow core-shell Cu / TiO2 catalyst based on a Murray-like law, characterized in that: The catalyst has a spherical hierarchical structure with a hollow interior and a mesoporous outer shell. The outer shell is composed of a TiO2 framework and Cu active components supported thereon. The ratio of the internal cavity diameter to the shell thickness, Dc / Ls, of the catalyst is 2.6 to 4.

0.

2. The hollow core-shell Cu / TiO2 catalyst based on a Murray-like law according to claim 1, characterized in that, The TiO2 shell contains continuous mesoporous channels with a pore size dm of 8–12 nm and a nano-building unit size db of 18–23 nm.

3. The hollow core-shell Cu / TiO2 catalyst based on a Murray-like law according to claim 1, characterized in that, The Cu active component is in Cu form on the catalyst surface. 0 It exists in the chemical state of Cu⁺.

4. A method for preparing a hollow core-shell Cu / TiO2 catalyst based on a Murray-like law as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1 Synthesis of Hard Templates: Using tetraethyl orthosilicate as a precursor, SiO2 nanospheres were synthesized as hard templates. S2 shell coating: The SiO2 nanospheres are dispersed in a mixed system of ethanol, acetonitrile and ammonia, and hydrolysis is controlled by tetrabutyl titanate to coat the SiO2 surface with a TiO2 shell to obtain a SiO2@TiO2 core-shell intermediate; S3 Active Metal Loading: Using copper nitrate as a copper precursor and urea as a slow-release alkali agent, Cu components are introduced onto the shell surface of the intermediate through a urea-assisted deposition precipitation method. S4 mesoscopic structuring treatment: Hexadecyltrimethylammonium bromide and polyvinylpyrrolidone were added to improve shell porosity and surface accessibility. S5 calcination fixation: The treated material is calcined at 600℃ for 2 hours to stabilize the TiO2 framework and remove residual organic matter; S6 etching for core removal: The SiO2 core template was removed by etching with sodium hydroxide solution at 90°C for 6 hours. After washing and drying, a hollow core-shell Cu / TiO2 catalyst was obtained.

5. The preparation method according to claim 4, characterized in that, In step S2, the thickness of the TiO2 shell is controlled by adjusting the amount of tetrabutyl titanate added, thereby controlling the final catalyst cavity-to-shell ratio Dc / Ls to be 2.6–4.

0.

6. The application of a hollow core-shell Cu / TiO2 catalyst based on Murray's law as described in any one of claims 1 to 3 in non-thermal plasma-assisted conversion of greenhouse gases.

7. The application according to claim 6, characterized in that, The reaction is a dielectric barrier discharge-assisted reverse water-gas shift reaction, which converts CO2 and H2 into CO and water.

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