Preparation method of ultrathin LDH confinement ruthenium monatomic catalyst for defect engineering regulation and control and application of ultrathin LDH confinement ruthenium monatomic catalyst in photocatalytic CO2 reduction

Abstract

The invention provides a preparation method of a defect engineering regulation ultrathin LDH confinement ruthenium monatomic catalyst and application of the defect engineering regulation ultrathin LDH confinement ruthenium monatomic catalyst to photocatalytic CO2 reduction, and relates to the technical field of catalyst preparation, the catalyst adopts ultrathin cobalt-aluminum layered double hydroxide (CoAl-LDH) rich in metal vacancies as a carrier, Ru monatomic is anchored at the metal vacancies through a wet impregnation process, and the catalyst is prepared through a hydrothermal method. Ru atoms and a surrounding matrix form an unsaturated coordination environment, so that adsorption and activation of CO2 are effectively enhanced; meanwhile, highly dispersed Ru active sites not only provide abundant catalytic centers, but also regulate and control the distribution of photo-generated charges on the surface of the catalyst, promote the separation and migration of charges, and significantly inhibit electron-hole recombination. Through the mode, the invention provides a construction strategy of a monatomic catalytic material, and a brand new technical path is provided for efficient CO2 photoreduction reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to a method for preparing a defect-engineered ultrathin LDH-confined ruthenium single-atom catalyst and its application in photocatalytic CO2 reduction. Background Technology

[0002] With the acceleration of industrialization, the massive combustion of fossil fuels has led to a sharp increase in carbon dioxide (CO2) emissions, significantly exacerbating the greenhouse effect and profoundly impacting the global climate system. To address the increasingly severe climate change and energy crisis, developing green and efficient CO2 conversion technologies has become a cutting-edge research direction in the energy and environment fields. Inspired by the mechanism of natural photosynthesis, utilizing solar energy to drive the photocatalytic reduction reaction of CO2 into renewable fuels or high-value-added chemicals, while possessing potential for both environmental governance and sustainable energy development, is considered a strategic technology with great application prospects. However, the stable molecular structure and strong chemical inertness of CO2 make it difficult to activate under conventional conditions, and the reaction process often faces high thermodynamic and kinetic barriers, greatly limiting the efficiency and practical application of catalysis. Therefore, constructing catalytic materials with high activity and high stability is key to promoting the development of CO2 photocatalytic conversion technology.

[0003] In recent years, single-atom catalysts (SACs) have become a research hotspot in the field due to their superior catalytic performance in the photoreduction reaction of CO2, exhibiting maximized metal atom utilization, unsaturated coordination structures, and unique electronic properties. Isolated metal atoms can serve as electron enrichment and transfer centers, promoting the adsorption and activation of CO2 molecules and the stabilization of key reaction intermediates, thereby effectively improving reaction efficiency. However, limited by the high surface energy and thermodynamic instability of single atoms, they are prone to migration and aggregation during the reaction, transforming into metal nanoparticles, resulting in a reduction of catalytic active sites and a significant decrease in catalytic performance. Therefore, achieving stable anchoring and uniform dispersion of single atoms is a core challenge in constructing high-performance SACs. Current research has shown that utilizing metal vacancies in support materials as anchoring points, strong interactions can effectively achieve spatial confinement of single atoms. Among these, two-dimensional materials, due to their abundant defect structures and control space, have been used to construct various stable SAC systems. Nevertheless, existing metal vacancy construction methods often rely on complex precursor designs, high-temperature treatments, or harsh reaction conditions, making it difficult to achieve large-scale, controllable preparation and limiting their widespread application. Furthermore, due to the high surface energy of metal atoms, they are prone to aggregation, and the stable and efficient development of SACs remains a significant challenge.

[0004] In view of this, it is necessary to design an improved method for preparing ultrathin LDH-confined ruthenium single-atom catalysts with defect engineering control and their application in photocatalytic CO2 reduction to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a defect-engineered ultrathin LDH-confined ruthenium single-atom catalyst and its application in photocatalytic CO2 reduction.

[0006] To achieve the above-mentioned objectives, in a first aspect, the present invention provides a method for preparing a defect-engineered, LDH-confined ruthenium single-atom catalyst, comprising the following steps:

[0007] S1. Dissolve cobalt salt and aluminum salt in water, add formamide solution dropwise to the resulting solution, adjust the pH of the mixed solution to 10, and perform hydrothermal reaction at 100-120℃ for 12 hours to obtain ultrathin LDH precursor;

[0008] S2. Under stirring conditions, the ruthenium precursor solution is added dropwise to the LDH precursor solution, and the reaction is carried out at 60°C for 10 h to obtain the ultrathin LDH confined ruthenium single-atom catalyst.

[0009] Preferably, in step S2, the concentration of the ruthenium precursor solution is 1.98 mmol / L, which is obtained by dissolving a ruthenium salt in methanol, wherein the ruthenium salt is one of ruthenium nitrate, ruthenium acetate, and ruthenium chloride.

[0010] Preferably, in step S2, the volume ratio of the ruthenium precursor solution to the LDH precursor solution is 1:8; the LDH precursor solution is obtained by dispersing the LDH precursor in a dispersion, and the dispersion is obtained by mixing methanol and ammonia in a volume ratio of 3:1.

[0011] Preferably, in step S1, the mass ratio of cobalt salt to aluminum salt is 2:1.

[0012] Preferably, the cobalt salt is one of cobalt nitrate, cobalt acetate, and cobalt chloride, and the aluminum salt is one of aluminum nitrate, aluminum acetate, and aluminum chloride.

[0013] Preferably, the formamide solution has a volume fraction of 20% and a dropping rate of 2 mL / min.

[0014] Secondly, the present invention provides an ultrathin LDH-confined ruthenium single-atom catalyst, which is composed of an ultrathin LDH and ruthenium atoms supported thereon, wherein the mass percentage of ruthenium atoms in the catalyst is 0.5-1.5%, preferably, the mass percentage of ruthenium atoms in the catalyst is 1%.

[0015] Thirdly, this invention provides an application of an ultrathin LDH-confined ruthenium single-atom catalyst in photocatalytic CO2 reduction.

[0016] The beneficial effects of this invention are:

[0017] 1. The present invention provides a method for preparing a defect-engineered, ultrathin LDH-confined ruthenium single-atom catalyst, comprising the steps of preparing an ultrathin LDH precursor and supporting ruthenium single atoms. Ultimately, ruthenium single atoms can be supported on the surface of a sheet-like ultrathin LDH to obtain a catalyst material applicable to photocatalytic CO2 reduction. Through this method, the present invention proposes a single-atom catalytic material construction strategy, providing a novel technical route for efficient CO2 photoreduction reactions, and laying an important theoretical foundation and technical support for the design and application of single-atom photocatalysts.

[0018] 2. The catalyst provided by this invention uses an ultrathin cobalt-aluminum layered double hydroxide (CoAl-LDH) rich in metal vacancies as a support. Through a simple wet impregnation process, Ru single atoms are anchored at their metal vacancies. The Ru atoms form an unsaturated coordination environment with the surrounding matrix, which effectively enhances the adsorption and activation of CO2. At the same time, the highly dispersed Ru active sites not only provide abundant catalytic centers, but also regulate the distribution of photogenerated charges on the catalyst surface, promote charge separation and migration, and significantly inhibit electron-hole recombination.

[0019] 3. The catalyst provided by this invention, by introducing a metal vacancy structure, achieves confined anchoring of Ru single atoms on the ultrathin LDH surface, thereby constructing highly dispersed and stable unsaturated catalytic active sites on the catalyst surface. The appearance of the metal vacancy structure not only improves the adsorption and activation capacity of CO2 molecules, but also effectively regulates the separation and transport process of photogenerated carriers, significantly enhancing the photocatalytic reduction efficiency. Experimental results show that the prepared u-1.0wt%Ru-LDH photocatalyst (Ru loading rate of 1%) achieves a CO yield as high as 4663.34 μmol g under 300W xenon lamp irradiation. -1 h -1 It outperforms the performance of most current LDH-based catalysts. Attached Figure Description

[0020] Figure 1 The nanostructure characterization results of u-LDH prepared in Example 1 of this invention are shown below.

[0021] Figure 2 This is a microstructure diagram of u-1.0wt%Ru-LDH obtained in Example 1 of the present invention;

[0022] Figure 3 The image shows a STEM image of u-1.0wt%Ru-LDH obtained in Example 1 of this invention.

[0023] Figure 4The XRD patterns are of the catalysts prepared in Examples 1 and 2 of this invention.

[0024] Figure 5 The IR spectra of the catalysts prepared in Examples 1 and 2 of this invention are shown.

[0025] Figure 6 The EPR diagrams are of the catalysts prepared in Examples 1 and 2 of this invention.

[0026] Figure 7 XPS images of the catalysts prepared in Examples 1 and 2 of this invention;

[0027] Figure 8 The adsorption energy of CO2 by the catalysts prepared in Examples 1 and 2 of this invention;

[0028] Figure 9 This refers to the Gibbs free energy of the reaction intermediate on the catalyst during the reduction of CO2 by the catalysts prepared in Examples 1 and 2 of this invention.

[0029] Figure 10 The results show the catalytic reduction activity and CO selectivity of the catalysts prepared in Examples 1 and 2 of this invention for CO2 reduction.

[0030] Figure 11 The results show the cycle stability of the photocatalytic reduction of CO2 by the catalysts prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0033] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] On the one hand, the present invention provides a defect-engineered ultrathin LDH confined ruthenium single-atom catalyst, which is composed of an ultrathin LDH and ruthenium atoms supported thereon. The thickness of the ultrathin LDH is 0.9 nm, and the mass percentage of ruthenium atoms in the catalyst is 0.5-1.5%, preferably 1%.

[0035] By controlling the loading of ruthenium atoms within the above range, the optimal catalytic activity of the catalyst can be ensured. If the loading is too high, Ru will easily aggregate into metal clusters, affecting the catalytic efficiency of the catalyst. If the loading is too low, the number of CO2 activation sites in the catalyst will be reduced, thereby limiting the catalytic performance of the catalyst.

[0036] Furthermore, this invention provides a method for preparing the above-mentioned defect-engineered ultrathin LDH-confined ruthenium single-atom catalyst, comprising the following steps:

[0037] S1. Dissolve cobalt salt and aluminum salt in water, add formamide solution dropwise to the resulting solution, adjust the pH of the mixed solution to 10, and perform hydrothermal reaction at 110℃ for 12 h; after centrifugation, the resulting product is washed with deionized water and methanol in sequence, and then freeze-dried to obtain an ultrathin LDH precursor.

[0038] S2. Under stirring conditions, the ruthenium precursor solution was added dropwise to the LDH precursor solution, and the mixture was heated and stirred in a water bath at 60°C for 10 hours to obtain the catalyst.

[0039] In the above technical solution, the catalyst formation mechanism is as follows: Under alkaline conditions (pH=10), it can promote the formation of metal ions (Co). 2+ Al 3+ The co-precipitation of ruthenium ions and the formation of LDH precursors are achieved by formamide, which can not only regulate crystal growth kinetics but also inhibit nanosheet stacking, providing an excellent growth environment for the formation of ultrathin LDH precursors. Subsequently, the heating process can promote the full migration and anchoring of ruthenium ions on the LDH support surface, and through strong coordination with the support surface groups, ruthenium is finally stably loaded on the LDH nanosheet surface in a single-atom-level dispersion, thus obtaining the catalyst.

[0040] In some embodiments, in step S1, the cobalt salt and aluminum salt are corresponding soluble salts, such as cobalt nitrate, cobalt acetate, cobalt chloride, aluminum nitrate, aluminum acetate, aluminum chloride, etc., and the mass ratio of cobalt salt to aluminum salt is 2:1. The specific types of substances can be selected according to the actual experimental needs, and are not limited to this.

[0041] In some embodiments, in step S1, the formamide solution has a volume fraction of 20% and is added at a dropping rate of 2 mL / min. The pH of the mixed solution in this step is adjusted by adding an appropriate amount of NaOH solution. The concentration and amount of NaOH solution added can be controlled according to the desired pH value; therefore, the concentration and amount of NaOH solution added are not described in detail here.

[0042] In the above technical solution, by using formamide solution as a solvent, the formation of LDH precursor crystals under hydrothermal conditions can be controlled, and nanosheet stacking can be suppressed, which is beneficial for obtaining ultrathin structures. Secondly, by adjusting the pH of the solution to alkaline conditions, it is beneficial for the formation of metal ions (Co... 2+ Al 3+ The co-precipitation of ) forms the LDH precursor.

[0043] In some embodiments, in step S1, the freeze-drying conditions are: temperature -10 to -20°C, time 24-48 hours. Freeze-drying maintains the ultrathin structure of the nanosheets and prevents aggregation.

[0044] In some embodiments, in step S2, the concentration of the ruthenium precursor solution is 1.98 mmol / L, which is obtained by dissolving a ruthenium salt in methanol. The ruthenium salt is a soluble salt, such as ruthenium nitrate, ruthenium acetate, ruthenium chloride, etc., and the dropping rate of the ruthenium precursor solution is 2 mL / min.

[0045] In some embodiments, in step S2, the LDH precursor solution is obtained by dispersing the LDH precursor in a dispersion, which is obtained by mixing methanol and ammonia at a volume ratio of 3:1, and the volume ratio of the ruthenium precursor solution to the LDH precursor solution is 1:8. The ammonia has a mass fraction of 25%, and the methanol has a mass fraction greater than 99.5%. The concentration of methanol used in this scheme is greater than 99.5%.

[0046] The following specific embodiments further illustrate the preparation method of the defect-engineered ultrathin LDH-confined ruthenium single-atom catalyst proposed in this invention and its application in photocatalytic CO2 reduction:

[0047] Example 1

[0048] This embodiment provides a method for preparing an ultrathin LDH-confined ruthenium single-atom catalyst controlled by defect engineering, comprising the following steps:

[0049] S1. Dissolve 0.291 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 0.187 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in 25 mL of deionized water and stir under magnetic stirring until the solids are completely dissolved. Then, slowly add 25 mL of 20% (v / v) formamide solution to the above mixed solution at a rate of 2 mL / min and continue stirring until homogeneous. Next, add 0.1 mol of NaOH solution dropwise to adjust the pH of the solution to 10, and then stir magnetically for 30 min at room temperature. Transfer the resulting solution to a closed reaction vessel and hydrothermally react at 110 °C for 12 h. After the reaction is completed, centrifuge to collect the solid product, and wash thoroughly with deionized water and methanol (analytical grade, mass fraction greater than 99.5%) to remove unreacted substances and surface impurities. Finally, freeze-dry the solid product under vacuum at -20 °C for 24 h to obtain an ultrathin LDH precursor, named u-LDH.

[0050] S2. Dissolve 2.23 mg of ruthenium trichloride hydrate (RuCl3·H2O) in 5 mL of methanol (analytical grade, mass fraction greater than 99.5%) to prepare a Ru precursor solution; disperse the u-LDH obtained in step S1 in 40 mL of dispersion and sonicate for 30 min to ensure uniform dispersion to obtain u-LDH solution; wherein, the dispersion is obtained by mixing methanol (analytical grade, mass fraction greater than 99.5%) and ammonia water at a volume ratio of 3:1;

[0051] The Ru precursor solution was slowly added dropwise to the u-LDH solution at a dropping rate of 2 mL / min, and the mixture was magnetically stirred at room temperature for 1 h. Then, the mixture was stirred for another 10 h in a 60 °C water bath. After stirring, the solid product was collected by centrifugation. Finally, the product was thoroughly washed with deionized water and methanol to remove unreacted precursors and surface impurities. The product was then freeze-dried under vacuum at -20 °C for 24 h to obtain an ultrathin LDH photocatalytic material with a Ru loading of 1.0 wt%, named u-1.0 wt% Ru-LDH.

[0052] It should be noted that the cobalt nitrate, aluminum nitrate, sodium hydroxide, formamide, urea, ammonia, and methanol used in the embodiments of the present invention were purchased from Aladdin Biochemical Technology Co., Ltd., and ruthenium chloride was purchased from Yuanye Biotechnology Co., Ltd.; unless otherwise specified, all raw materials used are of analytical grade.

[0053] The characterization results of the u-LDH nanostructure obtained in step S1 of this embodiment are as follows: Figure 1 As shown, Figure 1 Figure A in the diagram is an AFM diagram. Figure 1Figure B in Figure A shows a height profile. As can be seen from Figure A, u-LDH exhibits a sheet-like structure with a thickness of 0.9 nm and obvious surface undulations. The numbers 1, 2, and 3 in the figure correspond to the measurement path (white dashed line) in the right-hand line graph. The red circle (red part in the figure) represents the shaded background, and the white circle (yellow part in the figure) represents the catalyst. The brighter the yellow part, the thicker the catalyst. As can be seen from Figure B, there is a single plateau structure in region 1 with a peak height of 0.95 nm and small fluctuations in peak height. The plateau height in region 2 is slightly lower with steep edges and a peak height of 0.89 nm. The plateau structure in region 3 is clear with a central height and a peak height of 0.93 nm. The peak heights of the three regions are all close to 1 nm, indicating that the single-layer thickness or interlayer distance of u-LDH is stable at the nanoscale, which is consistent with the characteristics of layered materials.

[0054] The microstructure diagram of u-1.0wt%Ru-LDH obtained in this embodiment is shown below. Figure 2 As shown, the STEM image is as follows Figure 3 As shown, Figure 2 Figure a in the image is a TEM image. Figure 2 Figure b in the image is the HRTEM plot. From... Figure 2 As can be seen, u-1.0wt%Ru-LDH exhibits a typical layered nanosheet structure. HRTEM images clearly show defect regions induced by the exfoliation process, resulting in vacancy formation. Darker areas represent vacancy-rich defect regions, while lighter areas correspond to well-preserved crystal regions. From... Figure 3 Isolated ruthenium atoms can be observed to be highly dispersed in the LDH lattice.

[0055] Example 2

[0056] This embodiment provides a method for preparing an ultrathin LDH-confined ruthenium single-atom catalyst controlled by defect engineering, comprising the following steps:

[0057] S1. Dissolve 0.291g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O), 0.187g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O), and 1.8g of urea (CO(NH2)2) in 25mL of deionized water and stir under magnetic stirring until the solid is completely dissolved. Then, add 0.1mol of NaOH solution dropwise to adjust the pH of the solution to 10, and stir magnetically for 30min at room temperature. Transfer the resulting solution to a closed reaction vessel and hydrothermally react at 110℃ for 12h. After the reaction, centrifuge to collect the solid product, and wash thoroughly with deionized water and methanol (analytical grade, mass fraction greater than 99.5%) to remove unreacted substances and surface impurities. Finally, freeze-dry the solid product under vacuum at -20℃ for 24h to obtain the bulk LDH precursor (block form), named b-LDH.

[0058] S2. Dissolve 2.23 mg of ruthenium trichloride hydrate (RuCl3·H2O) in 5 mL of analytical grade (mass fraction greater than 99.5%) to prepare a Ru precursor solution; disperse the b-LDH obtained in step S1 in 40 mL of dispersion and sonicate for 30 min to ensure uniform dispersion to obtain u-LDH solution; wherein, the dispersion is obtained by mixing methanol (analytical grade, mass fraction greater than 99.5%) and ammonia water at a volume ratio of 3:1;

[0059] The Ru precursor solution was slowly added dropwise to the u-LDH solution at a dropping rate of 2 mL / min, and the mixture was magnetically stirred at room temperature for 1 h. Then, the mixture was stirred for another 10 h in a 60 °C water bath. After stirring, the solid product was collected by centrifugation. Finally, the product was thoroughly washed with deionized water and methanol to remove unreacted precursors and surface impurities. The product was then freeze-dried under vacuum at -20 °C for 24 h to obtain a bulk LDH photocatalyst material with a Ru loading of 1.0 wt%, named b-1.0 wt% Ru-LDH.

[0060] The XRD patterns of u-LDH and u-1.0wt%Ru-LDH in Example 1, and b-LDH and b-1.0wt%Ru-LDH in Example 2 are shown below. Figure 4 As shown in the figure, the diffraction peaks of u-LDH and b-LDH are completely different, indicating that there is an essential difference in their crystal structures. Specifically, b-LDH has the characteristics of good crystallization and orderly layered stacking, while u-LDH shows significant nano-sizing, small crystallite size, and poor stacking order (few-layer / monolayer characteristics). The diffraction peaks of u-1.0wt%Ru-LDH are basically consistent with those of u-LDH, indicating that the Ru (1.0wt%) loading did not significantly change the crystal structure of u-LDH, indicating that Ru exists only in the lattice of u-LDH in the form of highly dispersed single atoms. Compared with b-LDH, the peak intensity of b-1.0wt%Ru-LDH changes significantly, especially the (003) peak shifts to the right and the peak intensity increases sharply. This result indicates that Ru in b-1.0wt%Ru-LDH is loaded on the LDH surface in the form of metal clusters. The above results show that the loading behavior of Ru in u-1.0wt%Ru-LDH and b-1.0wt%Ru-LDH is completely different. Ru is dispersed in u-1.0wt%Ru-LDH in the form of single atoms, while it is in the form of metal clusters in b-1.0wt%Ru-LDH. This difference is determined by the physical state of LDH (ultra-thin, bulk). The ultra-thin structure is conducive to the formation of Ru single atoms.

[0061] The IR spectra of u-LDH and u-1.0wt%Ru-LDH in Example 1, and b-LDH and b-1.0wt%Ru-LDH in Example 2 are shown below. Figure 5 As shown, the EPR diagram is as follows: Figure 6 As shown. From Figure 5 As can be seen, at 1350cm -1 and 778cm -1 The absorption peak at that location belongs to The bending vibration, while 560cm -1 and 530cm -1 The peaks at these locations correspond to the bending vibrations of Co–O and Al–O, respectively. These absorption features are typical hallmarks of LDH, confirming the existence of the LDH structure. Figure 6 As can be seen, both oxygen vacancies and metal vacancies were detected in the LDH structure. The ultrathin LDH exhibited a significantly higher vacancy concentration compared to the original material, indicating that the ultrathin structure construction process induces abundant metal vacancies. Furthermore, the vacancy concentration increased further after loading ruthenium, suggesting that ruthenium preferentially binds at vacancy sites.

[0062] XPS spectra of u-1.0wt%Ru-LDH and b-1.0wt%Ru-LDH are shown below. Figure 7 As shown, Figure 7 Figure a in the diagram shows the Ru3p spectrum. Figure 7 Figure b shows the O1s spectrum. As can be seen from Figure a, the Ru 3p peaks at 464.8 eV and 485.9 eV in the u-1.0 wt% Ru-LDH sample are attributed to Ru. δ+ Ru 3p of species (0<δ<3) 1 / 2 and Ru 3p 1 / 2 In contrast, the Ru 3p spectrum of b-1.0 wt% Ru-LDH exhibits a negative shift of 0.46 eV, indicating that ruthenium is in a lower oxidation state. Furthermore, the absorption peaks at 462.0 eV and 463.8 eV correspond to Ru... 0 The study confirmed the preferential formation of ruthenium metal clusters in b-1.0wt%Ru-LDH. Figure b shows four characteristic peaks unconvolved at binding energies of 530.3, 531.5, 532.3, and 533.9 eV, corresponding to metal-oxygen species, lattice oxygen, oxygen vacancies, and water molecule-associated adsorbed oxygen species, respectively. The oxygen vacancy content in u-1.0wt%Ru-LDH was significantly higher than that in b-1.0wt%Ru-LDH, indicating that ruthenium loading on ultrathin LDH promotes oxygen vacancy formation and reveals different coordination environments for ruthenium atoms in ultrathin and bulk LDH.

[0063] Example 3

[0064] This embodiment provides a method for preparing an ultrathin LDH-confined ruthenium single-atom catalyst controlled by defect engineering, comprising the following steps:

[0065] S1. Dissolve 0.291 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 0.187 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in 25 mL of deionized water and stir under magnetic stirring until the solids are completely dissolved. Then, slowly add 25 mL of 20% (v / v) formamide solution to the above mixture and continue stirring until homogeneous. Next, add 0.1 mol of NaOH solution dropwise to adjust the pH of the solution to 10, and then stir magnetically for 30 min at room temperature. Transfer the resulting solution to a closed reaction vessel and hydrothermally react at 110 °C for 12 h. After the reaction is completed, centrifuge to collect the solid product, and wash thoroughly with deionized water and methanol to remove unreacted substances and surface impurities. Finally, freeze-dry the solid product under vacuum at -20 °C for 24 h to obtain an ultrathin LDH precursor, named u-LDH.

[0066] S2. Dissolve 1.115 mg of ruthenium trichloride hydrate (RuCl3·H2O) in 5 mL of methanol (analytical grade, mass fraction greater than 99.5%) to prepare a Ru precursor solution; disperse the u-LDH obtained in step S1 in 40 mL of dispersion and sonicate for 30 min to ensure uniform dispersion to obtain u-LDH solution; wherein, the dispersion is obtained by mixing methanol (analytical grade, mass fraction greater than 99.5%) and ammonia water at a volume ratio of 3:1;

[0067] The Ru precursor solution was slowly added dropwise to the u-LDH solution at a dropping rate of 2 mL / min, and the mixture was magnetically stirred at room temperature for 1 h. Then, the mixture was stirred for another 10 h in a 60 °C water bath. After stirring, the solid product was collected by centrifugation. Finally, the product was thoroughly washed with deionized water and methanol (analytical grade, mass fraction greater than 99.5%) to remove unreacted precursors and surface impurities. The product was then freeze-dried under vacuum at -20 °C for 24 h to obtain an ultrathin LDH photocatalyst material with a Ru loading of 1.0 wt%, named u-0.5 wt% Ru-LDH.

[0068] Example 4

[0069] S1. Dissolve 0.291 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 0.187 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in 25 mL of deionized water and stir under magnetic stirring until the solids are completely dissolved. Then, slowly add 25 mL of 20% (v / v) formamide solution to the above mixed solution and continue stirring until homogeneous. Next, add 0.1 mol of NaOH solution dropwise to adjust the pH of the solution to 10, and then stir magnetically for 30 min at room temperature. Transfer the resulting solution to a closed reaction vessel and hydrothermally react at 110 °C for 12 h. After the reaction is completed, centrifuge to collect the solid product, and wash thoroughly with deionized water and methanol (analytical grade, mass fraction greater than 99.5%) to remove unreacted substances and surface impurities. Finally, freeze-dry the solid product under vacuum at -20 °C for 24 h to obtain an ultrathin LDH precursor, named u-LDH.

[0070] S2. Dissolve 3.345 mg of ruthenium trichloride hydrate (RuCl3·H2O) in 5 mL of methanol (analytical grade, mass fraction greater than 99.5%) to prepare a Ru precursor solution; disperse the u-LDH obtained in step S1 in 40 mL of dispersion and sonicate for 30 min to ensure uniform dispersion to obtain u-LDH solution; wherein, the dispersion is obtained by mixing methanol and ammonia water at a volume ratio of 3:1;

[0071] The Ru precursor solution was slowly added dropwise to the u-LDH solution at a dropping rate of 2 mL / min, and the mixture was magnetically stirred at room temperature for 1 h. Then, the mixture was stirred for another 10 h in a water bath at 60 °C. After stirring, the solid product was collected by centrifugation. Finally, the product was thoroughly washed with deionized water and methanol (analytical grade, mass fraction greater than 99.5%) to remove unreacted precursors and surface impurities. The product was then freeze-dried under vacuum at -20 °C for 24 h to obtain an ultrathin LDH photocatalyst material with a Ru loading of 1.0 wt%, named u-1.5 wt% Ru-LDH.

[0072] Application Example 1

[0073] To explore the potential application of the catalysts prepared in Examples 1 and 2 to the photocatalytic reduction of CO2, this example first investigated the regulatory mechanism of the CO2 adsorption performance of the catalysts prepared in Examples 1 and 2 and the energy barrier differences of the catalytic reaction pathway. The results are as follows: Figures 8 to 9 As shown, Figure 8 This represents the adsorption energy of the catalyst for CO2 during the catalytic process. Figure 9 This represents the Gibbs free energy of the reaction intermediate on the catalyst. Figure 8 It can be seen that u-1.0wt%Ru-LDH exhibits the strongest CO2 adsorption capacity, significantly superior to other samples. From... Figure 9As can be seen, the energy barrier of u-1.0wt%Ru-LDH from CO2* to COOH* is significantly reduced (0.583eV), indicating that this is a more kinetically favorable pathway.

[0074] This application example explores the application of LDH-supported Ru in the photocatalytic reduction of CO2 before and after preparation in Examples 1 and 2. The specific application method is as follows: 20 mg of photosensitizer [Ru(bpy)3]Cl2·6H2O and 10 mg of catalyst were dispersed together in 40 mL of a TEOA / acetonitrile / water mixed solution (volume ratio 1:3:1) and injected into a closed reactor (Zhongjiao Jinyuan CEL-APR reactor, volume 200 mL) with a light window. Subsequently, the entire reaction system was evacuated using a vacuum pump to remove air. After evacuation, high-purity CO2 gas was introduced until the internal pressure of the reactor reached 1.8 bar, creating a CO2-saturated reaction environment (99.9% high-purity CO2). The reaction system was irradiated with a 300W xenon lamp with an irradiation wavelength range of 400-800 nm (visible light region) and a light intensity of 100 mW·cm. -2 The distance between the light source and the reactor was 10 cm. The reaction time was set to 3 hours. During the photocatalytic reaction, 1 mL of gas sample was taken from the reactor every 30 minutes using a gas sampler. The collected gaseous products were analyzed using a Fuli GC-F70 gas chromatograph equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID) to qualitatively and quantitatively determine the types and concentrations of the reaction products. The catalytic reduction activity and CO selectivity of the catalyst are shown in the following results. Figure 10 As shown in the figure, under 300W xenon lamp irradiation, the main products of CO2 photoreduction are CO and H2, with CO being the predominant product; secondly, Figure 10 This indicates that the catalyst with a Ru loading of 1.0 wt% exhibits the highest CO generation rate through photocatalysis of CO2. Furthermore, the CO yields of b-LDH, b-1.0 wt% Ru-LDH, u-LDH, u-0.5 wt% Ru-LDH, u-1.0 wt% Ru-LDH, and u-1.5 wt% Ru-LDH are 995.85, 2611.05, 1841.47, 3465.87, 4663.34, and 3827.4 μmol g, respectively. -1 h -1The photocatalytic performance of u-1.0wt%Ru-LDH is nearly 5 times higher than that of b-LDH and 2 times higher than that of b-1.0wt%Ru-LDH. This is due to the abundant metal vacancy defects in the ultrathin LDH, which allows Ru single atoms to be stably anchored within the LDH lattice. The atomic dispersion of Ru alters its coordination environment, creating more CO2 activation sites compared to the prevalent Ru clusters in b-1.0wt%Ru-LDH. Comparison of the photocatalytic performance of different Ru loadings shows that optimal Ru loading is crucial. Insufficient loading reduces the number of CO2 activation sites, thus limiting catalytic performance, while excessive loading promotes Ru aggregation into metal clusters, thereby reducing catalytic efficiency. Meanwhile, u-1.0wt%Ru-LDH exhibits good CO selectivity (70%), indicating effective suppression of the competitive hydrogen evolution reaction. The photocatalytic reduction CO2 cycle stability test results of u-1.0wt%Ru-LDH are shown below. Figure 11 As shown, the results indicate that after 5 cycles of catalysis, the CO yield of the catalyst is greater than 4000 μmol g. -1 h -1 .

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a defect-engineered, ultrathin LDH-confined ruthenium single-atom catalyst, characterized in that, Includes the following steps: S1. Dissolve cobalt salt and aluminum salt in water, add formamide solution dropwise to the resulting solution, adjust the pH of the mixed solution to 10, and perform hydrothermal reaction at 100-120℃ for 12 hours to obtain ultrathin LDH precursor; S2. Under stirring conditions, the ruthenium precursor solution is added dropwise to the LDH precursor solution, and the reaction is carried out at 60°C for 10 h to obtain the ultrathin LDH confined ruthenium single-atom catalyst.

2. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the ruthenium precursor solution is 1.98 mmol / L, which is obtained by dissolving a ruthenium salt in methanol. The ruthenium salt is one of ruthenium nitrate, ruthenium acetate, and ruthenium chloride.

3. The preparation method according to claim 1, characterized in that, In step S2, the volume ratio of the ruthenium precursor solution to the LDH precursor solution is 1:8; the LDH precursor solution is obtained by dispersing the LDH precursor in a dispersion, which is obtained by mixing methanol and ammonia in a volume ratio of 3:

1.

4. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of cobalt salt to aluminum salt is 2:

1.

5. The preparation method according to claim 4, characterized in that, The cobalt salt is one of cobalt nitrate, cobalt acetate, and cobalt chloride, and the aluminum salt is one of aluminum nitrate, aluminum acetate, and aluminum chloride.

6. The preparation method according to claim 1, characterized in that, The formamide solution has a volume fraction of 20% and a dropping rate of 2 mL / min.

7. An ultrathin LDH-confined ruthenium single-atom catalyst, characterized in that, It is prepared by any one of claims 1-6.

8. The ultrathin LDH-confined ruthenium single-atom catalyst according to claim 7, characterized in that, The catalyst is composed of an ultrathin LDH and ruthenium atoms supported thereon, wherein the mass percentage of ruthenium atoms in the catalyst is 0.5-1.5%.

9. The ultrathin LDH-confined ruthenium single-atom catalyst according to claim 7, characterized in that, The catalyst contains 1% ruthenium atoms by mass.

10. The application of an ultrathin LDH-confined ruthenium single-atom catalyst prepared by any one of claims 1-6 or the ultrathin LDH-confined ruthenium single-atom catalyst of claim 8 in photocatalytic CO2 reduction.

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