Single-atom catalyst particles and manufacturing method therefor

Abstract

The present invention relates to catalyst particles and a manufacturing method therefor. In the film, the catalyst enables the control of oxygen vacancies acting as catalytic active sites, enables a single-atom catalyst to be synthesized, and enables one or more single atoms to be bonded to a metal oxide having micropores through a spray pyrolysis process, thereby improving catalytic activity.

Description

Monatomic catalyst particles and method for manufacturing the same

[0001] The present invention relates to a single-atom catalyst particle produced using a spray pyrolysis process and a method for producing the same.

[0002] Catalytic technology has played a key role in various industrial fields, such as chemical processes, energy conversion, and environmental remediation. In particular, metal-based catalysts are essential for providing high activity and selectivity in chemical reactions. However, traditional nanoparticle-based catalysts frequently suffer from problems such as high metal usage and reduced active surface area or decreased selectivity due to metal particle aggregation during the reaction process. These limitations have raised the need for new approaches to maximize catalytic efficiency and increase the utilization of metal resources.

[0003] Single-atom catalysts (SACs) are attracting attention as a groundbreaking technology capable of solving these problems. SACs feature a structure in which each metal atom is individually immobilized on a support surface; compared to nanoparticle catalysts, they maximize the atomic efficiency of the metal and can significantly enhance the activity and selectivity of chemical reactions due to their unique electronic structures. Furthermore, the dispersion of single atoms acts as unique activation centers in catalysis, offering the potential to selectively promote specific reaction pathways.

[0004] The development of single-atom catalysts is advancing rapidly in tandem with advancements in materials science and nanotechnology. Designing supports to stably maintain the single-atom state, structural stabilization through strong metal-support interactions, and controlling activity and selectivity targeting specific reactions have become key directions in current research. Single-atom catalysts are demonstrating their potential in a wide range of applications, such as fuel cells, carbon dioxide conversion, hydrogen generation, and selective chemical reactions, and are emerging as a core technology for addressing environmental and energy challenges.

[0005] The objective of the present invention is to provide catalyst particles in which one or more monatomic metal catalysts are bonded to a porous metal oxide using a spray pyrolysis process, and a method for manufacturing the same.

[0006] To achieve the above objective, the present invention provides a porous three-dimensional structure formed of a metal oxide comprising one or more first metals; and catalyst particles dispersed in a monatomic state inside and on the surface of the three-dimensional structure, comprising one or more second metals different from the first metal.

[0007] In addition, the present invention comprises a first step of preparing a mixed solution in which a first metal precursor and a second metal precursor are dissolved; and

[0008] A method for manufacturing catalyst particles is provided, comprising: a second step of manufacturing catalyst particles by spray pyrolyzing the above mixed solution at a temperature of 500 to 1000 ℃.

[0009] According to the present invention, the catalyst of the present invention can control oxygen defects acting as catalytic active sites, can synthesize a single-atom unit catalyst, and can improve catalytic activity by bonding one or more single atoms to a metal oxide having micropores through a spray pyrolysis process.

[0010] FIG. 1 is a schematic diagram showing a method for manufacturing catalyst particles according to one embodiment of the present invention.

[0011] FIG. 2 is a flowchart showing a method for manufacturing catalyst particles according to one embodiment of the present invention.

[0012] Figure 3 is an image confirming the morphology of catalyst particles according to one embodiment of the present invention through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS).

[0013] Figure 4 is an image confirming the morphology of catalyst particles according to one embodiment of the present invention through a scanning electron microscope (SEM).

[0014] Figure 5 is an image confirming the morphology of catalyst particles according to one embodiment of the present invention through transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS).

[0015] FIG. 6 is a photographic image of a catalyst particle according to one embodiment of the present invention and an image taken with a high-resolution transmission electron microscope (HR-TEM).

[0016] FIG. 7 is a scanning transmission electron microscope (STEM) image and an energy dispersive spectroscopic mapping image of catalyst particles according to one embodiment of the present invention.

[0017] FIG. 8 is a scanning electron microscope (SEM) and transmission electron microscope (TEM) image of catalyst particles according to one embodiment of the present invention.

[0018] Figures 9 and 10 are graphs of the X-ray diffraction (XRD) analysis results of catalyst particles according to one embodiment of the present invention.

[0019] FIG. 11 is a graph of Raman spectroscopic analysis of catalyst particles according to one embodiment of the present invention.

[0020] FIGS. 12 and FIGS. 13 are UV-Vis absorbance graphs and tauc plots of catalyst particles according to one embodiment of the present invention.

[0021] FIGS. 14 and 15 are graphs showing the experimental results of the physical properties (nitrogen adsorption, pore size) of a catalyst according to one embodiment of the present invention.

[0022] FIG. 16 is a graph of the carbon dioxide hydrogenation reaction of catalyst particles according to one embodiment of the present invention.

[0023] FIG. 17 is a Raman spectrophotometer of a metal oxide contained in a catalyst particle according to one embodiment of the present invention, a Fourier transform infrared spectrophotometer (FT-IR) after a catalytic reaction, a hydrogen adsorption graph, and a carbon dioxide desorption graph.

[0024] Figure 18 is experimental data on the catalytic properties according to the monatomic composition of catalyst particles according to a comparative example.

[0025] FIG. 19 is a graph of the XANES and EXAFS spectra of catalyst particles according to one embodiment of the present invention.

[0026] FIG. 20 is an in-situ CO-DRIFTS spectrum graph of catalyst particles according to one embodiment of the present invention.

[0027] FIG. 21 is a graph showing the catalytic activity of catalyst particles according to one embodiment of the present invention.

[0028] FIG. 22 is a graph of potential energy profiles of catalyst particles according to one embodiment of the present invention.

[0029] FIG. 23 is the result of a long-term stability test of catalyst particles according to one embodiment of the present invention.

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing. In the attached drawings, the dimensions of the structures are shown enlarged compared to the actual dimensions for the clarity of the present invention.

[0031] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0032] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0033] Meanwhile, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0034]

[0035] The catalyst particles according to the present invention include a porous three-dimensional structure formed of a metal oxide comprising one or more first metals; and one or more second metals different from the first metal, dispersed in a monatomic state inside and on the surface of the three-dimensional structure.

[0036] The catalyst particles may be single-atom catalyst particles or heterogeneous single-atom catalyst particles. Specifically, the catalyst particles may be catalysts for the carbon dioxide hydrogenation reaction.

[0037] The first metal may include one or more selected from the group consisting of cerium (Ce), silicon (Si), titanium (Ti), and zirconium (Zr).

[0038] Specifically, the metal oxide containing the first metal may be CeO2-x.

[0039] By including the metal oxide as described above, excellent carbon dioxide adsorption / desorption characteristics can be exhibited.

[0040] The second metal may include one or more selected from the group consisting of platinum (Pt), palladium (Pd), cobalt (Co), and nickel (Ni). Specifically, the second metal may include two or more selected from the group consisting of platinum (Pt), palladium (Pd), cobalt (Co), and nickel (Ni).

[0041] The above three-dimensional structure has a spherical shape having an average size of 400 to 600 nm or 450 to 550 nm and may include pores with a size of 1 to 20 nm, 1 to 10 nm, or 1 to 5 nm inside.

[0042] The above pores have an interconnected network structure, and the second metal disposed inside the three-dimensional structure may be exposed through the pores.

[0043] The content of the second metal may be 0.5 to 5 at%, 1 to 5 at%, or 1 to 2 at%.

[0044]

[0045] FIG. 1 is a schematic diagram showing a method for manufacturing catalyst particles according to the present invention. FIG. 2 is a flowchart showing a method for manufacturing catalyst particles.

[0046] Referring to FIG. 2, the method for manufacturing catalyst particles according to the present invention may include: a first step (S110) of preparing a mixed solution in which a first metal precursor and a second metal precursor are dissolved; a second step (S120) of manufacturing catalyst particles by spray pyrolysis of the mixed solution at a temperature of 500 to 1000 ℃; and a third step (S130) of heat-treating the catalyst particles for 10 to 60 minutes in an air atmosphere at a temperature of 300 to 500 ℃.

[0047] In the first step (S110) above, the first metal precursor may include one or more acetate, nitrate, chloride, or sulfate selected from the group consisting of cerium (Ce), silicon (Si), titanium (Ti), and zirconium (Zr).

[0048] The second metal precursor may include one or more acetates, nitrates, or sulfates selected from the group consisting of platinum (Pt), palladium (Pd), cobalt (Co), and nickel (Ni). Specifically, the second metal precursor may include two or more acetates, nitrates, or sulfates selected from the group consisting of platinum (Pt), palladium (Pd), cobalt (Co), and nickel (Ni).

[0049] In the first step (S110) above, the mixed solution may further include one or more dispersants selected from the group consisting of citric acid, polyvinylpyrrolidone (PVP), sucrose, and oleic acid.

[0050] In the first step (S110) above, the concentration of the first metal precursor may be 0.01 to 0.1 M.

[0051] In the first step (S110) above, the first metal precursor and the second metal precursor may be included in a molar ratio of 100:1 to 5 or 100:1 to 3.

[0052] In the second step (S120) above, the spray pyrolysis can drop the mixed solution into droplets through a droplet generating device and then pass it through a pyrolysis reactor.

[0053] The second step (S120) above can form a catalyst in which a single atom is evenly dispersed and bonded to a metal oxide by spray pyrolysis of the mixed solution under an inert gas atmosphere at a temperature of 500 to 1000°C or 500 to 800°C.

[0054] In the second step (S120) above, catalyst particles can be produced by spray pyrolysis and then recovered through a collection filter.

[0055] In the third step (S130) above, the catalyst particles may be heat-treated for 10 to 60 minutes or 20 to 40 minutes under air atmosphere and temperature conditions of 400 to 600°C or 450 to 550°C.

[0056]

[0057] Hereinafter, the present invention will be described in detail with reference to examples to aid in understanding. However, the following examples are merely illustrative of the content of the present invention and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[0058]

[0059] <Example>

[0060] Porous CeO2-x and porous CeO2-x supported with a metal catalyst were synthesized via spray pyrolysis. The spray precursor solution was prepared by dissolving 0.05 M cerium acetate hydrate (Ce(CH3CO2)3·xH2O, 99.9%, Sigma-Aldrich) in distilled water and then adding 0.1 M citric acid (HOC(COOH)(CH2COOH)2, 99.9%, Sigma-Aldrich). Citric acid was used as a complexing agent to uniformly disperse single and heterogeneous monatoms in the CeO2-x structure and to prevent aggregation. The metal catalyst-supported ceria contained Pt, Ni, and Co, which were supplied by platinum chloride hexahydrate (H2PtCl6·6H2O, distillation, Sigma-Aldrich), nickel(II) acetate tetrahydrate (Ni(OCOCH3)2·4H2O, 99%, Sigma-Aldrich), and cobalt(II) acetate tetrahydrate (Co(OCOCH3)2·4H2O, 98%, Sigma-Aldrich). For single monatomic Pt (Pt1 and Pt2) on CeO2-x, 1 and 2 mol% of platinum precursor (H2PtCl6·6H2O) were added to the solution to prepare catalysts with metal-to-cerium molar ratios of 1:99 and 2:98. For the Pt and Ni of the heteroatom catalyst CeO2-x(Pt1Ni1) and the Pt and Co of the heteroatom catalyst CeO2-x(Pt1Co1), 1 mol% of a platinum precursor (H2PtCl6·6H2O) and 1 mol% of a nickel (Ni(OCOCH3))2·4H2O) or cobalt (Co(OCOCH3)2·4H2O) precursor were added, and the total metal-cerium molar ratio was 2:98. The mixed solution was stirred using a magnetic stirrer at 300 rpm for 1 hour to ensure homogeneity and dispersibility. Droplets generated by an ultrasonic atomizer (frequency: 1.7 MHz, power: 30 W, 6 transducers) were transferred to a quartz tube (length: 1 m, inner diameter: 50 mm) and reacted by supplying N2 carrier gas at a rate of 10 L / min.The tubular furnace (model: Lindberg / Blue M) was set to 600°C, and the product was collected in powder form in a bag filter (material: Teflon, pore size: 0.2 μm). Then, catalyst particles were prepared by performing heat treatment in a box furnace (model: Thermo Scientific Lindberg / Blue M) at 500°C in air, a heating rate of 5°C / min, and a holding time of 30 minutes.

[0061]

[0062] <Comparative Example>

[0063] Porous CeO2-x and porous CeO2-x supported with a metal catalyst were synthesized via spray pyrolysis. The spray precursor solution was prepared by dissolving 0.05 M cerium acetate hydrate (Ce(CH3CO2)3·xH2O, 99.9%, Sigma-Aldrich) in distilled water and then adding 0.1 M citric acid (HOC(COOH)(CH2COOH)2, 99.9%, Sigma-Aldrich). Citric acid was used as a complexing agent to uniformly disperse single and double metal atoms in the CeO2-x structure and to prevent aggregation. The metal catalyst-supported ceria contained Pd, Cu, Mn, Zn, Zr, Rh, and In, respectively, which were supplied by Palladium(II) acetylacetonate, Copper acetate monohydrate, Mrganese(II) acetate tetrahydrate, Zinc acetate dihydrate, Zirconium acetate hydrate, Rhodium(III) chloride hydrate, and Indium acetate hydrate, respectively. For single atoms on the CeO2-x phase, 2 mol% of the precursor was added to the solution to prepare the catalyst such that the molar ratio of metal to cerium was 2:98. The mixed solution was stirred using a magnetic stirrer at 300 rpm for 1 hour to ensure homogeneity and dispersibility. Droplets generated by an ultrasonic nebulizer (frequency: 1.7 MHz, power: 30 W, 6 transducers) were transferred to a quartz tube (length: 1 m, inner diameter: 50 mm) and reacted by supplying N2 carrier gas at a rate of 10 L / min. The tubular furnace (model: Lindberg / Blue M) was set to 600°C, and the product was collected in powder form in a bag filter (material: Teflon, pore size: 0.2 μm). Then, catalyst particles were prepared by performing heat treatment in a box furnace (model: Thermo Scientific Lindberg / Blue M) at 500°C in air, a heating rate of 5°C / min, and a holding time of 30 minutes.

[0064]

[0065] <Experimental Example 1>

[0066] To confirm the morphology of the catalyst particles according to the present invention, photographs, scanning electron microscopes (SEM), transmission electron microscopes (TEM), and high-resolution transmission electron microscopes (HR-TEM) were taken, and energy dispersive spectroscopic mapping was performed, and the results are shown in FIGS. 3 to 8.

[0067] Figure 3 shows scanning electron microscope (SEM) and transmission electron microscope (TEM) images of mesoporous (internal pores 5 nm or less) metal oxide particles having oxygen defects, (a) and (b) are scanning electron microscope (SEM) images, (c) is a transmission electron microscope (TEM) image, (d) is a crystal phase image, and (e) is an EDS mapping image. Looking at Figure 3, it was confirmed that the average particle size is 560 nm and the mesoporous particles have a uniform particle composition.

[0068] Figure 4 shows a photograph (a) and a transmission electron microscope (TEM) image (b) of catalyst particles in which a monatomic metal is uniformly dispersed in a mesoporous metal oxide having oxygen defects.

[0069] Figure 5 is a transmission electron microscope (TEM) image (top) and EDS mapping image (below) of catalyst particles in which a monatomic metal is uniformly dispersed in a mesoporous metal oxide having oxygen defects, and images of catalyst particles of (a) PtSA-CeO2-x, (b) PdSA-CeO2-x, and (c) CuSA-CeO2-x.

[0070] Looking at Figures 4 and 5, it was confirmed that the catalyst particles containing CeO2-x combined with platinum, palladium, and copper monatomic metals had the monatomic metals uniformly dispersed throughout the catalyst particles.

[0071] Figure 6 shows a photograph (a) and a transmission electron microscope (TEM) image (b) of catalyst particles in which two or more monatomic metals are uniformly dispersed in a mesoporous metal oxide having oxygen defects.

[0072] Figure 7 shows scanning transmission electron microscope (lines 1-2) and EDS mapping images (line 3) of catalyst particles in which two or more monatomic metals are uniformly dispersed in a mesoporous metal oxide having oxygen defects, and images of catalyst particles of (a,e) Pt1-CeO2-x, (b,f) Pt2-CeO2-x, (c,g) Pt1Ni1-CeO2-x and (d,h) Pt1Co1-CeO2-x.

[0073] Looking at Figures 6 and 7, it was confirmed that the catalyst particles containing CeO2-x, in which Pt, PtCo, and PtNi single atoms are bonded, have two types of metal single atoms uniformly dispersed throughout the catalyst particles.

[0074] Figure 8 shows scanning electron microscope (SEM) and transmission electron microscope (TEM) images of catalyst particles in which two or more metal atoms are bonded to a metal oxide, (ad) a scanning electron microscope image at different magnifications, and (e) images of catalyst particles of Pt1-CeO2-x, (f) Pt2-CeO2-x, (g) Pt1Ni1-CeO2-x, and (h) Pt1Co1-CeO2-x. It was confirmed that two or more metal atoms were uniformly distributed in a metal oxide with an average size of 500 nm and an average pore size of 5 nm using a spray pyrolysis process.

[0075]

[0076] <Experimental Example 2>

[0077] X-ray diffraction (XRD), Raman spectroscopy, and UV-Vis spectroscopy were performed to measure the chemical properties of the catalyst particles according to the present invention, and the results are shown in Figures 9 to 13 and Table 1.

[0078] Figure 9 is an XRD graph of catalyst particles that are metal oxides bonded with monoatoms of type 1 metal. Looking at Figure 9, no specific monoatom peak is found, indicating that the monoatom species are bonded in a size smaller than the crystal slit, i.e., in a monoatom form. Additionally, there is a peak shift of about 0.35 degrees to the right compared to pure CeO2-x, which indicates that this is due to atomic defects / bondings formed by the monoatoms.

[0079] Figure 10 shows the X-ray diffraction (a), Raman spectroscopy (b), Tauc plots (c), X-ray photoelectron spectroscopy (d), H2-TPR profile (e), and CO2-TPD profile (f) of catalyst particles of Pt1-CeO2-x, Pt2-CeO2-x, Pt1Ni1-CeO2-x, and Pt1Co1-CeO2-x. Looking at Figure 10, it was confirmed that the monatomic metal atoms altered the oxygen defects of the CeO2-x metal oxide support, and that CeO2-x acts as a CO2-activated adsorption site as a support without metal doping, and that the monatomic metal atoms participate in a manner that is reducible mainly to the H2 adsorption site, and that the reaction pathway changes depending on the adsorption and desorption sites based on the MO-Ce chemical bond.

[0080] Figure 11 shows the Raman spectroscopic graphs of catalyst particles of CeO2-x, Pt1-CeO2-x, Pt1Ni1-CeO2-x, Pt1Co1-CeO2-x, and Pt2-CeO2-x, in the ranges of a) 100–900, b) 350–550, c) 125–275, and d) 530–770 cm⁻¹. Raman spectroscopy is an essential method for identifying structural changes associated with oxygen defects. Looking at Figure 11, each catalyst exhibits a peak at 461 cm⁻¹, which corresponds to the F2g vibrational mode associated with the local octahedral symmetry around the cubic fluorite structure of CeO2. Additionally, a metal-oxygen-cerium (MO-Ce) bonding peak is observed in the 350–550 cm-1 range (b), and a peak corresponding to oxygen defects within the CeO2 lattice is observed in the 530–770 cm-1 range (d). The 461 cm-1 peak shifts to a lower wavenumber and weakens in intensity when metal atoms are added to CeO2 (see Fig. 11b). In particular, the CeO2-x peaks of Pt1-based catalysts (Pt1, Pt1Co1, Pt1Ni1) show more pronounced shifts and intensity changes than those of Pt2, Ni2, and Co2 catalysts. This indicates that larger defect changes occurred in the CeO2 lattice structure and confirms that each metal element formed a different bonding mode with the CeO2 lattice. The coupled MO-Ce peak is also observed in the 125–275 cm⁻¹ (c) and 530–770 cm⁻¹ (d) ranges, which are associated with vibrational modes related to oxygen defects, such as oxygen vacancies (Ov) resulting from the presence of Ce³⁺ in the CeO₂ lattice. Each metal atom exhibits different overlapping peaks in the 125–275 cm⁻¹ range (c), indicating that Pt and TM (Ni or Co) are coupled with Ce and O in the CeO₂-x structure. The Ce³⁺ state within the CeO₂ lattice can be confirmed through the peak in the 530–770 cm⁻¹ (d) range.

[0081] Figure 12 shows the UV-Vis absorbance graphs and tauc plots of catalyst particles of PtSA-CeO2-x, PdSA-CeO2-x, CuSA-CeO2-x, and CeO2-x, and Figure 13 shows the UV-Vis absorbance graphs and tauc plots of catalyst particles of CeO2-x, Pt1-CeO2-x, Pt1Ni1-CeO2-x, Pt1Co1-CeO2-x, and Pt2-CeO2-x. Table 1 shows the results of Figures 12 and 13.

[0082] SampleCeO2-xPtSA-CeO2-xPdSA-CeO2-xCuSA-CeO2-xPt1-CeO2-xPt1Ni1-CeO2-xPt1Co1-CeO2-xBand-gap Energy (eV)3.002.812.873.002.762.782.83

[0083] Various optical properties were investigated in the wavelength range of 300–800 nm using UV-Vis spectroscopy, thereby deriving the bandgap energies of each composition. The UV-Vis absorbance graphs and Tauc plots for CeO2x samples added with Pt, Pd, and Cu are shown in Fig. 12, while the UV-Vis absorbance graphs and Tauc plots for CeO2x samples added with Pt1, Pt1Ni1, Pt1Co1, and Pt2 are shown in Fig. 13. Based on these data, the bandgap energies of each sample were calculated as shown in Table 1. Examining Figs. 12, 13, and Table 1, the bandgap of CeO2-x coupled with monoatomic catalysts was generally reduced compared to CeO2-x. This reduction in bandgap is attributed to changes in the MO-Ce bonding state in the metal-CeO2-x system, which leads to changes in oxygen defects and Ce3+ states, forming free electron transfer pathways.

[0084] In particular, Pt1-CeO2-x and the heteroatom catalysts Pt1Ni1-CeO2-x and Pt1Co1-CeO2-x exhibit lower band gaps than other catalysts, indicating that the electron transport pathway is more activated. The reduction of the band gap is directly related to increased electron transport, and generally, a smaller band gap indicates improved chemical reactivity. Through these results, it was confirmed that metal addition plays an important role in controlling the electronic and optical properties of CeO2-x.

[0085]

[0086] <Experimental Example 3>

[0087] To confirm the physical properties of the catalyst particles according to the present invention, nitrogen adsorption, pore size, carbon dioxide hydrogenation reaction, Raman spectroscopy, Fourier transform infrared spectroscopy, hydrogen adsorption, and carbon dioxide desorption were analyzed, and the results are shown in Figures 14 to 17, Table 2, and Table 3.

[0088] Sample / CeO2-xCeO2-xPtSAPdSACuSABET surface area (m2 / g)58.5676.2181.4870.37Total pore volume (cm2 / g)0.17880.16890.18290.1765Pore size (nm)9.96.46.36.6

[0089]

[0090] Sample / CeO2-xCeO2-xPt1Pt1Ni1Pt1Co1Pt2BET surface area (m2 / g)58.5680.3777.3278.5576.21Total pore volume (cm2 / g)0.17880.18120.23630.22290.1689Pore size (nm)9.96.210.06.96.4

[0091] Figure 14 is a graph showing the nitrogen adsorption curve (a) and pore size distribution (b) of catalyst particles of PtSA-CeO2-x, PdSA-CeO2-x, CuSA-CeO2-x, and CeO2-x, and Table 2 shows the BET specific surface area data.

[0092] Looking at Figure 14 and Table 2, the catalyst particles bonded with metal single atoms show increased specific surface area values ​​compared to pure CeO2-x, and the average pore size decreased, which indicates that the increase in internal defects due to atomic bonding influenced the increase in specific surface area.

[0093] Figure 15 and Table 3 show (a) p / p0 versus Va / cm3 (STP) g-1, (b) p / po versus p / Va (P0-p), and (c) pore size distributions of catalyst particles of CeO2-x, Pt1-CeO2-x, Pt1Ni1-CeO2-x, Pt1Co1-CeO2-x, and Pt2-CeO2-x. Looking at Figure 15 and Table 3, it can be seen that the specific surface area and pore volume of the monoatomic catalyst (Pt1-CeO2-x, Pt2-CeO2-x) and heteroatomous monoatomic catalyst (Pt1Ni1-CeO2-x, Pt1Co1-CeO2-x) samples are higher than those of CeO2-x. This is because the introduction of metal atoms created oxygen vacancies and lattice defects within the CeO2 structure; these defects slightly disturbed the lattice and formed additional adsorption sites, resulting in a more open internal structure. Consequently, the pore volume of the heterogeneous single-atom catalyst sample increased by approximately 50% compared to CeO2-x. At the same time, it was confirmed that the original particle size and overall shape of CeO2-x were maintained.

[0094] Figure 16 is a graph of the CO2 hydrogenation reaction of a metal oxide (CeO2) bonded with a monatomic metal, showing an increased catalytic conversion rate and TOF compared to pure CeO2-x, and showing differences in selectivity for CO, CH4, and CH3OH depending on the type of monatomic metal. This indicates that the type of monatomic metal affects not only catalytic activity but also selectivity.

[0095] Figure 17 shows the Raman, FTIR, H2-TPR, and CO2-TPD chemioadsorption graphs of a metal oxide (CeO2) bonded with a monatomic metal. (a) Raman analysis shows the differences in oxygen and atomic defects formed in CeO2 according to each monatomic composition. (b) FTIR indicates that the differences in adsorption peaks after catalytic reaction according to monatomic composition represent differences in selectivity due to differences in bonding strength between compounds during the catalytic reaction. Additionally, (c) the differences in hydrogen adsorption peaks indicate affinity for the corresponding temperature, and higher peak intensity indicates higher hydrogen affinity. It can be confirmed that Pt exhibited high hydrogen adsorption in the temperature range where the CO2 hydrogenation reaction mainly takes place. (d) CO2 desorption is based on CeO2-x, indicating that the adsorption and desorption of CO2 occur through the defect sites of CeO2-x.

[0096]

[0097] <Experimental Example 4>

[0098] To confirm the catalytic activity of the catalyst particles according to the comparative example, carbon dioxide conversion rate, H2-TPR, Raman spectroscopy, and X-ray diffraction (XRD) analysis were performed, and the results are shown in Fig. 18.

[0099] Figure 18 shows the catalytic conversion rates, H2TPR, Raman, and XRD graphs of transition metals other than monatomic metals. (a) Different catalytic conversion rates were observed depending on the monatomic composition, and (b) it was confirmed that the hydrogen affinity was lower in the case of monatomic catalysts exhibiting low catalytic conversion rates. Additionally, (c) differences in the characteristics of atomic defect formation in CeO2 were confirmed through Raman spectroscopy, and (d) the presence of monatomic metals was confirmed through XRD.

[0100] Through this, it can be seen that the catalyst particles according to the present invention exhibit hydrogen affinity in different temperature ranges depending on the type of single atom, and that when containing platinum, palladium, copper, nickel, and cobalt, they have superior hydrogen affinity compared to other elements.

[0101]

[0102] <Experimental Example 5>

[0103] To confirm the catalytic activity of the catalyst particles according to the present invention, XANES and EXAFS spectra, in-situ CO-DRIFTS spectra, carbon dioxide conversion rate, turnover frequency, carbon monoxide selectivity, methane selectivity, potential energy profile, and long-term stability tests of the catalyst particles were performed, and the results are shown in FIGS. 19 to 23.

[0104] Looking at Fig. 19, it can be seen that in the catalyst particles containing metal oxides bonded with monatomic metals, the monatomic metals are bonded to the surface of the metal oxides, and the oxidation state of each metal and metal oxide is increased.

[0105] Referring to Figure 20, the in-situ DRIFTS spectra reveal that Pt atoms exist in different bonding states on each catalyst. The main band ranges represent the Pt atomic states on CeO2. CO gas (2158–2186 cm⁻¹), CO linearly adsorbed onto single-atom Pt sites on CeO2 (2080–2115 cm⁻¹), a CO ensemble linearly bound to Pt (2063–2044 cm⁻¹), and single Pt atoms separated from CeO2 (1957–2031 cm⁻¹) can be identified. The spectrum of CO adsorbed on Pt1-CeO2-x (a) primarily showed single Pt atoms adsorbed on Pt-O and single Pt atoms separated from CeO2. In contrast, Pt2-CeO2-x exhibited not only sharp single-atom peaks but also peaks for the Pt ensemble on the catalyst (b). For the heterogeneous monoatom catalysts Pt1Ni1-CeO2-x and Pt1Co1-CeO2-x, particularly stronger bands were observed for isolated single Pt atoms and adsorbed single Pt atoms (c and d). These results indicate that the heterogeneous monoatom catalysts (Pt1Ni1-CeO2-x and Pt1Co1-CeO2-x) contain more active Pt sites than the Pt1-CeO2-x and Pt2-CeO2-x catalysts due to the presence of linearly adsorbed single atoms and isolated metallic single Pt atoms.

[0106] Looking at Figure 21, it was confirmed that catalyst particles containing metal oxides bonded with monatomic metals exhibit different catalytic activity and selectivity effects depending on the monatomic composition, and show high activity for two or more bonded monatomic metals, and that selectivity for specific products is also improved.

[0107] Looking at Figure 22, the catalytic reaction pathway varies depending on the catalyst composition, and the results of the DFT calculation for the synergistic effect by Ni and Co are shown.

[0108] Looking at Fig. 23, it was confirmed that the catalyst particles of Pt1Co1-CeO2-x maintained their catalyst conversion rate and CO selectivity for a long time as a result of the catalyst long-term stability test.

[0109]

[0110] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1.

1. A porous three-dimensional structure formed of a metal oxide comprising at least one first metal; and A catalyst particle dispersed in a monatomic state inside and on the surface of the above three-dimensional structure, comprising one or more second metals different from the first metal.

2. In Paragraph 1, The first metal comprises one or more selected from the group consisting of cerium (Ce), silicon (Si), titanium (Ti), and zirconium (Zr), and The catalyst particle comprising one or more selected from the group consisting of platinum (Pt), palladium (Pd), cobalt (Co), and nickel (Ni), wherein the second metal is a catalyst particle.

3. In Paragraph 1, The catalyst particle is characterized by having a spherical shape with an average size of 400 to 600 nm and containing pores of a size of 1 to 20 nm inside the three-dimensional structure.

4. In Paragraph 3, The above pores have an interconnected network structure, and A catalyst particle characterized in that the second metal disposed inside the above three-dimensional structure is exposed through the pore.

5. In Paragraph 1, A catalyst particle characterized by the content of the second metal being 0.5 to 5 at%.

6. A first step of preparing a mixed solution in which the first metal precursor and the second metal precursor are dissolved; and A method for manufacturing catalyst particles, comprising: a second step of manufacturing catalyst particles by spray pyrolyzing the above mixed solution at a temperature of 500 to 1000 ℃.

7. In Paragraph 6, The first metal precursor comprises one or more acetates, nitrates, chlorides, or sulfates selected from the group consisting of cerium (Ce), silicon (Si), titanium (Ti), and zirconium (Zr), and A method for manufacturing catalyst particles, characterized in that the second metal precursor comprises one or more acetates, nitrates, or sulfates selected from the group consisting of platinum (Pt), palladium (Pd), cobalt (Co), and nickel (Ni).

8. In Paragraph 7, A method for manufacturing catalyst particles, characterized in that, in the first step above, the mixed solution further comprises one or more dispersants selected from the group consisting of citric acid, polyvinylpyrrolidone (PVP), sucrose, and oleic acid.

9. In Paragraph 6, A method for manufacturing catalyst particles, characterized in that, in the first step above, the concentration of the first metal precursor is 0.01 to 0.1 M.

10. In Paragraph 6, A method for manufacturing catalyst particles, wherein in the second step above, the spray pyrolysis is characterized by atomizing the mixed solution through a droplet generating device and then passing it through a pyrolysis reactor.

11. In Paragraph 6, A method for manufacturing catalyst particles, further comprising a third step of heat-treating the catalyst particles for 10 to 60 minutes in an air atmosphere and at a temperature of 400 to 600°C.

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