Preparation of hexagonal close-packed (2H) rhodium and rhodium alloy nanomaterials

Abstract

The invention provides a compound derivation method for synthesizing 2H rhodium (Rh) and 2H rhodium-based alloy nano materials. The method comprises the following steps: preparing orthorhombic crystal phase Rh2C nanosheets (NPLs); the pure 2H rhodium nanosheet is obtained by extracting C atoms from the Rh2C nanosheet; and obtaining the 2H rhodium-based alloy nanosheet by simultaneously reducing the second metal during the C atom extraction process.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202511034798.6 (22) Application Date 2025.07.25 (30) Priority Data 63 / 675,447 2024.07.25 US (71) Applicant The Chinese University of Hong Kong Address Sha Tin, New Territories, Hong Kong, China (72) Inventors Chen Ye Zheng Long Shu Chenhao (74) Patent Agency Guangdong Nanyue Commercial Intellectual Property Agency Co., Ltd. 44809 Patent Attorney Tian Xiaoqian (51) Int.Cl. B22F 9 / 24 (2006.01) B22F 1 / 054 (2022.01) B22F 1 / 068 (2022.01) (54) Invention Title: Preparation of Hexagonal Close-Packed (2H) Rhodium and Rhodium Alloy Nanomaterials (57) Abstract: This invention provides a compound derivatization method for synthesizing 2H rhodium (Rh) and 2H rhodium-based alloy nanomaterials. The method includes: preparing orthorhombic Rh2C nanosheets (NPLs); obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets; and obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing a second metal during the C atom extraction process. Claims: 2 pages Description: 9 pages Drawings: 32 pages CN 121402641 A 2026.01.27 CN 1 21 40 26 41 A 1. A compound derivatization method for synthesizing 2H rhodium and 2H rhodium-based alloy nanomaterials, comprising: preparing orthorhombic Rh2C nanosheets; obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets; and obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing a second metal during the C atom extraction process. 2. The method of claim 1, wherein preparing orthorhombic Rh2C nanosheets comprises: dissolving a first predetermined amount of Rh(acac)3 or RhCl3 in a container in a mixed solution containing a second predetermined amount of oleylamine and a third predetermined amount of oleic acid, and subjecting the solution to sonication for a first predetermined time; adding a fourth predetermined amount of formaldehyde to the mixed solution; sealing the container and subjecting the container to sonication for a second predetermined time; heating the container at a first predetermined temperature for a third predetermined time; and cooling the container to room temperature. 3. The method of claim 2, further comprising: collecting the obtained product by centrifugation at 14000 rpm for 5 minutes; washing the obtained product once or multiple times with a mixture of cyclohexane and ethanol (v / v = 1:2); and dispersing the obtained product in cyclohexane. 4. The method of claim 1, wherein obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets comprises:5. The method of claim 1, wherein obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing the second metal during C atom extraction comprises: redispersing the Rh2C nanosheets in a fifth predetermined amount of oleylamine and dissolving a sixth predetermined amount of the first predetermined metal precursor in a fifth predetermined amount of oleylamine by ultrasonic treatment; and heating the solution in an oil bath at a third predetermined temperature for a fifth predetermined time, while simultaneously introducing an Ar / H2 mixture having a first predetermined percentage of H2 volume content into the solution in a bubbling manner at the first predetermined flow rate. 6. The method of claim 4, further comprising: collecting the obtained product by centrifugation at 14,000 rpm for 5 minutes; washing the obtained product three times with a mixture of cyclohexane and ethanol (v / v = 1:2); and dispersing the obtained product in cyclohexane. 7. The method of claim 5, further comprising: collecting the obtained product by centrifugation at 14,000 rpm for 5 minutes; washing the obtained product three times with a mixture of cyclohexane and ethanol (v / v = 1:2); and dispersing the obtained product in cyclohexane. 8. The method of claim 2, wherein the first predetermined amount is in the range of 1 to 3 mg. 9. The method of claim 2, wherein the second predetermined amount is approximately 2.25 mL. 10. The method of claim 2, wherein the third predetermined amount is in the range of 0.1 to 0.3 mL. 11. The method of claim 2, wherein the first predetermined time is approximately 5 minutes. Claims 1 / 2 page 2 CN 121402641 A 12. The method of claim 2, wherein the fourth predetermined amount is in the range of 0.7 to 0.8 mL. 13. The method of claim 2, wherein the second predetermined time is in the range of 5 to 10 minutes. 14. The method of claim 2, wherein the first predetermined temperature is in the range of 160 to 200°C. 15. The method of claim 2, wherein the third predetermined time is approximately 12 hours. 16. The method of claim 4, wherein the fifth predetermined amount is in the range of 2.0 to 4.0 mL. 17. The method of claim 4, wherein the second predetermined temperature is in the range of 130 to 160°C. 18. The method of claim 4, wherein the fourth predetermined time is in the range of 16 to 24 hours. 19. The method of claim 4, wherein the first predetermined percentage is approximately 10%.20. The method of claim 4, wherein the first predetermined flow rate is approximately 50 ml / min. 21. The method of claim 5, wherein the sixth predetermined amount is in the range of 0.1 to 1 mg. 22. The method of claim 5, wherein the first predetermined metal precursor is a Ru precursor or a Pt precursor. 23. The method of claim 5, wherein the third predetermined temperature is in the range of 140 to 200 °C. 24. The method of claim 5, wherein the fifth predetermined time is in the range of 14 to 20 hours. 25. The method of claim 1, wherein the obtained 2H rhodium nanosheets are constructed having an edge length range of 5 to 50 nm and an edge width range of 2 to 20 nm. 26. The method of claim 1, wherein the obtained 2H rhodium nanosheets are constructed having a thickness of approximately 1 to 4 nm. Claims 2 / 2 Page 3 CN 121402641 A Preparation of Hexagonal Close-Packed (2H) Rhodium and Rhodium Alloy Nanomaterials Cross-Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 675,447, filed July 25, 2024, the entire contents of which (including any pictures, tables or figures) are incorporated herein by reference. Background Art

[0002] Rhodium (Rh) nanomaterials exhibit excellent catalytic properties and have attracted considerable research interest from academia and industry due to their great potential in various application areas, including the traditional automotive industry, electric vehicles and fine chemicals.

[0003] Recent advances in nanomaterial phase engineering (PEN) have sparked widespread interest in the synthesis and properties of noble metal nanomaterials, especially Rh nanomaterials with unconventional crystalline phases. Despite significant progress, obtaining pure hexagonal close-packed (hcp, 2H type) Rh nanomaterials remains extremely difficult. Current research has only synthesized 2H / face-centered cubic (fcc or 3C) heterogeneous Rh nanomaterials, such as 2H / 3CRh nanoparticles (Rong Yu et al., J. Am. Chem. Soc., 2017, 139, 575), 2H / 3CAu@Rh core-shell nanosheets (Hua Zhang et al., J. Am. Chem. Soc., 2021, 143, 4387), and 2H / 3CPd@Rh core-shell nanostructures (Hua Zhang et al., Nat Sci., 2022; 2: e20220026). Since there are currently no reports of successfully preparing pure 2H rhodium nanomaterials, synthesizing pure 2H rhodium nanomaterials remains a significant challenge.

[0004] With the development of PEN, the crystal phase of nanomaterials has been considered an important parameter for regulating their physicochemical properties. 2HThe structure is an unconventional crystalline phase of Rh, with its close-packed planes exhibiting a characteristic "ABAB" stacking pattern along the

[0001] h crystal direction. However, pure 2H rhodium nanomaterials have not yet been published.

[0005] Furthermore, there are few published studies on the synthesis of 2H-containing heterogeneous Rh nanomaterials, and the 2H content is low and difficult to control. It remains very difficult to prepare Rh nanocrystals with high crystalline phase purity and unconventional 2H phase without template agents. Therefore, it is of great significance to develop new routes or formulations for synthesizing 2H rhodium nanomaterials and to study their phase-dependent catalytic properties. Summary of the Invention

[0006] There is still a need in the art to improve the design and techniques for preparing 2H rhodium nanosheets (NPLs).

[0007] According to embodiments of the present invention, a compound derivatization method for synthesizing pure 2H rhodium and 2H rhodium-based alloy nanomaterials is provided. The method includes: preparing orthorhombic Rh2C nanosheets; obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets; and obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing a second metal during the C atom extraction process. The preparation of orthorhombic Rh2C nanosheets includes: dissolving a first predetermined amount of Rh(acac)3 or RhCl3 in a container in a mixed solution containing a second predetermined amount of oleylamine and a third predetermined amount of oleic acid, and subjecting it to sonication for a first predetermined time; adding a fourth predetermined amount of formaldehyde to the mixed solution; sealing the container and subjecting it to sonication for a second predetermined time; heating the container at a first predetermined temperature for a third predetermined time; and cooling the container to room temperature. The method further includes: collecting the obtained product by centrifugation at 14000 rpm for 5 minutes; washing the obtained product once or multiple times with a mixture of cyclohexane and ethanol (v / v = 1:2); and dispersing the obtained product in cyclohexane. Furthermore, obtaining pure 2H rhodium nanosheets by extracting C atoms from Rh2C nanosheets includes: redispersing Rh2C nanosheets in a fifth predetermined amount of oleylamine by ultrasonic treatment; and heating the solution in an oil bath at a second predetermined temperature for a fourth predetermined time, while simultaneously introducing a mixture of Ar / H2 with a first predetermined H2 volume content into the solution in a bubbling manner at a first predetermined flow rate. Obtaining 2H rhodium-based alloy nanosheets includes: redispersing Rh2C nanosheets in a fifth predetermined amount of oleylamine by ultrasonic treatment and dissolving a sixth predetermined amount of a first predetermined metal precursor; and heating the solution in an oil bath at a third predetermined temperature for a fifth predetermined time, while simultaneously introducing a mixture of Ar / H2 with a first predetermined H2 volume content into the solution in a bubbling manner at a first predetermined flow rate. The first predetermined amount can be in the range of 1 to 3 mg. The second predetermined amount can be approximately 2.25 mL. The third predetermined amount can be in the range of 0.1 to 0.3 mL. The first reservation time can be approximately 5 minutes. The fourth reservation...The amount can be in the range of 0.7 to 0.8 mL. The second predetermined time can be in the range of 5 to 10 minutes. The first predetermined temperature is in the range of 160 to 200 °C. The third predetermined time can be approximately 12 hours. The fifth predetermined amount can be in the range of 2.0 to 4.0 mL. The second predetermined temperature is in the range of 130 to 160 °C. The fourth predetermined time is in the range of 16 to 24 hours. The first predetermined percentage can be approximately 10%. The first predetermined flow rate can be approximately 50 mL / min. The sixth predetermined amount can be in the range of 0.1 to 1 mg. The first predetermined metal precursor can be a Ru precursor or a Pt precursor. The third predetermined temperature is in the range of 140 to 200 °C. The fifth predetermined time is in the range of 14 to 20 hours. Furthermore, the obtained 2H rhodium nanosheets can be constructed with an edge length in the range of 5 to 50 nm, an edge width in the range of 2 to 20 nm, and a thickness of approximately 1 to 4 nm. The elemental composition of the obtained 2H rhodium-based alloy nanosheets includes RhRu and RhPt.

[0008] Figure 1 is a schematic diagram of the transformation process of orthorhombic rhodium carbide (Rh2C) nanocrystals of different morphologies and sizes into hexagonal close-packed (hcp, 2H type) Rh nanosheets (NPLs) and face-centered cubic (fcc, or 3C) Rh nanoflowers (NFs) according to embodiments of the present invention.

[0009] Figures 2A to 2G show the characterization of orthorhombic Rh2C nanosheets according to embodiments of the present invention, wherein Figure 2A is a low-magnification transmission electron microscope (TEM) image, and Figure 2B is an X-ray diffraction (XRD) pattern image of orthorhombic Rh2C nanosheets, wherein the insets in Figures 2A and 2B are schematic diagrams of orthorhombic Rh2C nanosheets and schematic diagrams of orthorhombic Rh2C nanosheet unit cells, respectively, wherein Figure 2C is a high-angle ring with atomic resolution aberration correction of a representative Rh2C nanosheet viewed from the front. Dark-field scanning transmission electron microscopy (HAADF-STEM) images, where Figure 2D is a magnified image of a selected area from Figure 2C, Figure 2E shows the corresponding fast Fourier transform (FFT) spectra, where Figure 2F is an image of a simulated crystal structure based on the projection of orthorhombic phases along the

[001] zone axis, and Figure 2G shows the corresponding simulated FFT spectra, where the simulated data for orthorhombic Rh2C are based on published lattice parameters and (J. Am. Chem. Soc., 2020, 142, 1247).

[0010] Figures 3A to 3B: According to an embodiment of the invention, Figure 3A shows a histogram of the size distribution of the edge width of the orthorhombic Rh2C nanosheets measured from Figure 2A, and Figure 3B shows a histogram of the size distribution of the edge length of the orthorhombic Rh2C nanosheets measured from Figure 2A.

[0011] Figures 4A to 4J show the characterization of 2H rhodium nanosheets according to an embodiment of the invention, where Figure 4A is a low-magnification HAADF-STEM images, Figure 4B is a selected area electron diffraction (SAED) image, Figure 4C shows the XRD pattern of 2H rhodium nanosheets, where the inset in Figure 4A is a schematic diagram of 2H rhodium nanosheets, Figure 4D is an atomic resolution aberration-corrected HAADF-STEM image of a representative 2H rhodium nanosheet viewed from the front, Figure 4E is a magnified image of a selected area in Figure 4D, Figure 4F shows the corresponding FFT pattern, where the inset in Figure 4F is a regular hexagonal dashed line, Figure 4G is an atomic resolution aberration-corrected HAADF-STEM image of a representative 2H rhodium nanosheet loaded on a 2.3 nm thick C nanotube viewed from the side, Figure 4H is a magnified image of a selected area in Figure 4G, Figure 4I shows the corresponding FFT pattern, Figure 4J shows the crystallographic model of the top view (left) and side view (top and right) of the 2H rhodium nanosheet, where the close-packed plane along the

[0001] h direction shows the ABAB characteristic. (Note: This last part is a reference to a document, likely a product description, and doesn't need a direct translation. It can be left as is.) A. The stacking order, simulated XRD patterns of orthorhombic Rh2C are based on published lattice parameters and (J. Am. Chem. Soc., 2020, 142, 1247), simulated XRD patterns of 2H rhodium are based on lattice parameters, and XRD patterns of 3C rhodium are based on data from PDF#05-0685.

[0012] Figures 5A to 5B: According to an embodiment of the present invention, Figure 5A shows a histogram of the edge width size distribution of 2H rhodium nanosheets measured from Figure 4A, and Figure 5B shows a histogram of the edge length size distribution of 2H rhodium nanosheets measured from Figure 4A.

[0013] Figures 6A to 6F show the thickness measurement results of 2H rhodium nanosheets according to an embodiment of the present invention, wherein Figure 6A is a low-magnification TEM image of 2H rhodium nanosheets loaded on C nanotubes, wherein Figures 6B to 6E are high-resolution TEM (HRTEM) images of different 2H rhodium nanosheets loaded on C nanotubes viewed from the side, and wherein Figure 6F shows a bar graph of the thickness statistics of 2H rhodium nanosheets measured from Figures 6B to 6E and Figure 4G.

[0014] Figures 7A to 7C illustrate the characterization of orthorhombic Rh2C nanoflowers according to embodiments of the present invention, wherein Figure 7A is a low-magnification TEM image, Figure 7B is an XRD pattern image, and Figure 7C is a size distribution histogram of orthorhombic Rh2C nanoflowers. The inset in Figure 7A is a schematic diagram of a typical orthorhombic Rh2C nanoflower, and the simulated XRD pattern of orthorhombic Rh2C is based on published lattice parameters and (J. Am. Chem. Soc., 2020, 142, 1247).

[0015] Figures 8A to 8C illustrate the characterization of 3C rhodium nanoflowers according to embodiments of the present invention, wherein Figure 8A is a low-magnification TEM image.TEM images, wherein Figure 8B is an XRD image, and Figure 8C is a SAED pattern of 3C rhodium nanoflowers, wherein the inset in Figure 8A is a schematic diagram of 3C rhodium nanoflowers and size distribution histograms, wherein the simulated XRD pattern of orthorhombic Rh2C is based on published lattice parameters and (J. Am. Chem. Soc., 2020, 142, 1247), and wherein the XRD pattern of 3C rhodium is based on data from PDF#05-0685.

[0016] Figure 9 shows the crystal structure characterization of a single 3C rhodium nanoflower according to an embodiment of the present invention, wherein Figure 9A is a low-magnification TEM image of a single 3C rhodium nanoflower, wherein Figures 9B1, 9C1, and 9D1 are HRTEM images of selected regions (labeled as b, c, and d, respectively) in Figure 9A, and their corresponding FFT patterns are shown in Figures 9B2, 9C2, and 9D2.

[0017] Figures 10A to 10E illustrate the coordination environment and chemical state characterization of 2H rhodium nanosheets, 3C rhodium nanoflowers, and orthorhombic Rh2C nanosheets according to embodiments of the present invention. Figure 10A shows the K-edge X-ray absorption near-edge structure (XANES) spectrum of rhodium, and Figure 10B shows the Fourier transform rhodium k3-weighted K-edge extended X-ray absorption fine structure (EXAFS) spectra of Rh bulk foil, orthorhombic Rh2C nanosheets, 2H rhodium nanosheets, 3C rhodium nanoflowers, and Rh2O3 powder. The inset in Figure 10A shows the magnified XANES spectrum obtained from a selected region of Figure 10A. Figure 10C is an X-ray photoelectron spectroscopy (XPS) image. Figure 10D is a magnified XPS spectral image taken from a selected region of the orthorhombic Rh2C nanosheets, 2H rhodium nanosheets, and 3C rhodium nanoflowers in Figure 10C. Figure 10E shows 2H rhodium nanosheets, 3C rhodium nanoflowers, and orthorhombic Rh2C nanosheets according to embodiments of the present invention. The unit cells of H-rhodium nanocrystals, with lattice parameters as follows:

[0018] Figures 11A to 11C: According to an embodiment of the present invention, Figure 11A shows the low-frequency Raman spectrum of orthorhombic Rh2C nanosheets, Figure 11B shows the low-frequency Raman spectrum of 2H rhodium nanosheets, and Figure 11C shows the low-frequency Raman spectrum of 3C rhodium nanoflowers.

[0019] Figures 12A to 12B: According to an embodiment of the present invention, Figure 12A shows the XRD spectra of Rh2C nanosheet derivatives with different C extraction reaction times, and Figure 12B shows the XRD spectra of Rh2C nanoflower derivatives with different C extraction reaction times, wherein the simulated XRD pattern of orthorhombic Rh2C is based on published lattice parameters and (J. Am. Chem. Soc., 2020, 142, 1247), wherein the simulated XRD pattern of 2H rhodium is based on lattice parameters and wherein the XRD pattern of 3C rhodium is based on data from PDF#05-0685.

[0020] Figure 13 shows the results of a thermal stability study of the 2H rhodium nanosheet crystal structure according to an embodiment of the present invention, which is shown on page 6 of 3 / 9 of the specification.CN 121402641 A shows the XRD patterns of 2H rhodium nanosheets loaded on C powder after annealing for 1 hour at different temperatures ranging from 300°C to 700°C in an argon gas flow containing 10% H2. Notably, the broadened peak at approximately 44°C in the Rh / C-700°C XRD pattern is attributed to the graphitized C support. The XRD pattern of 3C rhodium is based on data from PDF#05-0685, while the simulated XRD pattern of 2H rhodium is based on lattice parameters.

[0021] Figures 14A to 14H show the results of the thermal stability study of the morphology and crystal structure of 2H rhodium nanosheets according to embodiments of the present invention, showing the results of annealing at 300°C (Figure 14A), 400°C (Figure 14B), and 500°C in an argon gas flow containing 10% H2. Low-magnification TEM images of 2H rhodium nanosheets loaded on C powder after annealing at 600℃ (Fig. 14C), 600℃ (Fig. 14D), and 700℃ (Fig. 14F) for 1 hour; HRTEM images of individual 2H / 3C heterogeneous rhodium nanoparticles (NPs) after annealing at 600℃ (Fig. 14E); and HRTEM images of individual 3C rhodium nanoparticles after annealing at 700℃ (Fig. 14G). The inset in Fig. 14G shows the corresponding FFT spectra. Fig. 14H is a schematic diagram of the transformation process from individual 2H rhodium nanosheets to 2H / 3C heterogeneous rhodium nanoparticles and then to 3C rhodium nanoparticles.

[0022] Figures 15A to 15D illustrate the structure and composition characterization of 2H rhodium (Rh) ruthenium (Ru) nanosheets according to embodiments of the present invention, wherein Figure 15A is a low-magnification TEM image, Figure 15B is a SAED image, Figure 15C is an energy-dispersive X-ray spectroscopy (EDS) elemental mapping image of Ru and Rh and their overlapping image, and Figure 15D is a line scan through three 2H rhodium ruthenium nanosheets, wherein the formation of the RhRu alloy is confirmed.

[0023] Figures 16A to 16C illustrate the structure and composition characterization of 2H rhodium (Rh) platinum (Pt) nanosheets according to embodiments of the present invention, wherein Figure 16A is a low-magnification TEM image, Figure 16B is a SAED image, and Figure 16C is a line scan through 2H rhodium platinum nanosheets, wherein the formation of the RhPt alloy is confirmed. Detailed Description

[0024] Embodiments of the present invention relate to a compound derivatization method for synthesizing 2H rhodium nanomaterials.

[0025] The terminology used herein is for describing specific embodiments only and is not intended to limit the invention. The term “and / or” as used herein includes any and all combinations of one or more of the related listed items. The singular forms “a,” “an,” and “the” as used herein are intended to include both plural and singular forms unless the context clearly indicates otherwise. It will be further understood that the terms “comprising” and / or “including” as used herein specify the described features, steps, operations, elements.The presence of and / or components, but does not preclude the presence or addition of one or more other features, steps, operations, elements, components and / or combinations thereof.

[0026] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms (e.g., terms as defined in common dictionaries) shall be interpreted as consistent with their meaning in the relevant field and in the context of this disclosure, and shall not be interpreted in an idealized or overly formal manner unless expressly defined herein.

[0027] When the term “about” is used herein in conjunction with a numerical value, it shall be understood that the value may be in the range of 90% to 110% of that value, i.e., the value may be + / - 10% of the described value. For example, “about 1 kg” means 0.90 kg to 1.1 kg.

[0028] In describing the invention, it should be understood that a variety of techniques and steps are disclosed. Each of these techniques and steps has its own advantages, and each technique and step may be used in combination with one or more (in some cases all) other disclosed techniques. Therefore, for clarity, this specification will avoid repeating all possible combinations of the steps unnecessarily. However, it should be understood upon reading the specification and claims that such combinations are entirely within the scope of this invention and its claims.

[0029] Studying the catalytic properties of metal nanomaterials with unconventional crystalline phases is of great significance for developing new materials and technologies that can drive the development of energy conversion, catalysis, and other applications. However, synthesizing high-purity metal nanomaterials with unconventional crystalline phases remains a major challenge. For example, pure 2H rhodium nanomaterials have not yet been successfully prepared.

[0030] This invention provides a compound derivatization method for synthesizing pure 2H rhodium and 2H rhodium-based alloy nanomaterials in a two-step process. Specifically, orthorhombic Rh2C nanosheets are first prepared. Then, pure 2H rhodium nanosheets are obtained by extracting C atoms from the Rh2C nanosheets, and 2H rhodium-based alloy nanosheets are obtained by reducing a second metal during the extraction of C atoms. Importantly, the 2H rhodium nanosheets exhibit excellent thermal stability, maintaining the 2H phase and two-dimensional (2D) morphology for up to 1 hour at 300°C in an inert atmosphere. This indicates their applicability to various industrial conditions, such as the traditional automotive industry, electric vehicles, and the fine chemical industry. Furthermore, this compound derivatization method can also provide guidance for the synthesis of other nanomaterials with unconventional crystalline phases.

[0031] In the first step of the synthesis, the orthorhombic Rh2C nanosheets were prepared as follows. First, 1 to 3 mg of Rh(acac)3 or RhCl3 was dissolved in a glass pressure-resistant tube containing 2.25 mL of oleylamine and 0.1 to 0.3 mL of [unclear text - likely a typo, should be removed].In a mixed solution of oleic acid, 0.7 to 0.8 mL of formaldehyde was added to the above solution. Next, the glass pressure tube was sealed and sonicated for 5 to 10 minutes. Then, the glass pressure tube was placed in an oven and allowed to stand at 160 to 200 °C for 12 hours, and then allowed to cool naturally to room temperature. The product was collected by centrifugation at 14,000 rpm for 5 minutes, and the product was washed three times with a mixture of cyclohexane and ethanol (v / v = 1:2) and finally dispersed in cyclohexane.

[0032] In the second step of the synthesis, 2H phase rhodium nanosheets were obtained by extracting C atoms from the Rh2C compound. Specifically, the pre-synthesized Rh2C nanosheets were redispersed in 2.0 to 4.0 mL of oleylamine in a three-necked flask by sonication. The solution was then heated in an oil bath at 130 to 160 °C for 16 to 24 hours. Simultaneously, an Ar / H2 mixture with a H2 volume content of 10% was continuously bubbled into the solution at a flow rate of 50 ml / min. The resulting product was collected by centrifugation at 14,000 rpm for 5 minutes, washed three times with a mixture of cyclohexane and ethanol (v / v = 1:2), and finally dispersed in cyclohexane. Rhodium-based alloy nanosheets with a 2H phase were obtained by simultaneously reducing the second metal during C atom extraction. Specifically, pre-synthesized Rh2C nanosheets and 0.1 to 1 mg of Ru(acac)3 or Pt(acac)2 were dissolved in 2.0 to 4.0 mL of oleylamine in a three-necked flask by sonication. The solution was then heated in an oil bath at 140 to 200 °C for 14 to 20 hours. Simultaneously, an Ar / H2 mixture with a H2 volume content of 10% was continuously bubbled into the solution at a flow rate of 50 ml / min. The product was collected by centrifugation at 14000 rpm for 5 minutes. The product was washed three times with a mixture of cyclohexane and ethanol (v / v = 1:2) and finally dispersed in cyclohexane. Note that the Ru precursor can be replaced by RuCl3 and the Pt precursor can be replaced by H2PtCl6.

[0033] In the control experiment, larger orthorhombic Rh2C nanoflowers were prepared by reducing the amount of formaldehyde to 0.25 ml in the orthorhombic Rh2C nanosheet synthesis formulation while keeping other conditions unchanged. In addition, 3C rhodium nanoflowers derived from Rh2C nanoflowers were obtained by using a C atom extraction method similar to that used for 2H rhodium nanosheets and extending the reaction time (e.g., 27 to 32 hours).

[0034] The present invention provides a compound derivatization method that can prepare pure 2H rhodium and 2H rhodium-based alloy nanosheets in high yield. In addition, the prepared 2H rhodium nanosheets are extremely small in size, have uniform morphology, and have excellent thermal stability.

[0035] Comparison with the prior art

[0036] The following are some literature related to the synthesis of orthorhombic Rh2C nanocompounds and 2H / 3C heterogeneous Rh nanomaterials, and are compared with the embodiments of the present invention.

[0037] 1. In the previous publication "Formation of Hexagonal-Close Packed (HCP) Rhodium as a Size Effect" (Rong Yu, J. Am. Chem. Soc., 2017, 139, 575), 2H / 3C heterogeneous rhodium nanoparticles were prepared by solvothermal reaction or electron beam-induced decomposition of monolayer rhodium. However, in the powder XRD pattern, the 2H signal was too weak to be detected, while the observed 3C signal was very strong, indicating the presence of abundant 3C byproducts.

[0038] In contrast, the embodiments of the present invention develop a compound derivatization method to synthesize 2H rhodium nanosheets, achieving high yield and crystal phase purity. Furthermore, the phase-dependent properties of Rh were systematically analyzed for electrocatalytic reactions, revealing its intrinsic mechanism.

[0039] 2. In the previously published paper "Selective Epitaxial Growth of Rh Nanorods on 2H / fcc Heterophase Au Nanosheets to Form 1D / 2D Rh–Au Heterostructures for Highly Efficient Hydrogen Evolution" (Hua Zhang, J. Am. Chem. Soc., 2021, 143, 4387), a 2H / 3C heterophase Rh shell was formed by epitaxial growth on square 2H / 3C heterophase Au nanosheets. Since the 2H / 3C heterophase Au template is mainly 3C phase, the main phase of the deposited Rh shell is also 3C. The prepared 2H / 3C heterogeneous Au@Rh core-shell nanosheets exhibited higher hydrogen evolution reaction (HER) activity in acidic electrolytes, which was superior to commercial 3CRh / C, indicating that unconventional crystalline phase Rh has great potential in catalytic applications.

[0040] 3. Preparation of 2D / OD hierarchical heterostructures on 2H-Pd nanoparticles by face-selective epitaxial growth of triangular Rh nanosheets (Nat. Sci., 2022; 2:e20220026). Professor Hua Zhang's team published on pure 2H palladium (Pd) nanoparticles2H / 3C heterogeneous Rh shells are epitaxially grown on the seed. Due to the face-selective epitaxial growth of the Rh shell, 3C rhodium is obtained when grown on the (0002)h face of the 2H palladium seed, while 2H rhodium is prepared when deposited on other faces of the 2H palladium seed, thus obtaining 2H / 3C heterogeneous Rh shells. The 2H / 3C heterogeneous Pd@Rh core-shell nanostructure exhibits good hydrogen evolution activity in alkaline electrolyte, which is superior to commercial 3CRh / C.

[0041] Unlike the methods published in references 2 and 3, according to the embodiments of the present invention, a template-free method for synthesizing pure 2H rhodium nanosheets is developed, which has high yield and great potential for crystal phase-promoted catalysis applications.

[0042] 4. Rational synthesis of noble metal carbides (J. Am. Chem. Soc., 2020, 142, 1247). Professor Hiroshi Kitagawa's team published a study on the synthesis of orthorhombic Rh2C nanocompounds via a solvothermal reaction. However, the morphology of the Rh2C nanocrystals is irregular and the size distribution is uneven. In their work, they extracted C atoms from Rh2C compounds by heating Rh2C loaded on C powder in a tube furnace at 150°C for 2 hours under an H2 atmosphere at 1 atm. However, only 3C rhodium nanomaterials were obtained.

[0043] In contrast to this work, according to embodiments of the present invention, the morphology and size of Rh2C nanocompounds can be controlled by adjusting the reaction conditions, thereby obtaining larger-sized Rh2C nanoflowers and Rh2C nanosheets. Furthermore, it was found that the size and morphology of the Rh2C compound play an important role in determining the crystal phase of Rh2C-derived rhodium nanomaterials. When extracting C atoms from larger-sized Rh2C nanoflowers, 3C rhodium nanoflowers can be obtained. However, when extracting C atoms from Rh2C nanosheets, 2H rhodium nanosheets can be synthesized. These findings provide guidance for the preparation of nanomaterials with unconventional crystalline phases.

[0044] 5. Introducing ordered vacancies into metal nanostructures to construct vacancy Barlow fillers for high-performance hydrogen evolution (Sci. Adv., 2021, 7, eabd6647). Professor Hua Zhang's team published the synthesis of C-doped 2H rhodium nanostructures with ordered vacancies. However, interstitial C atoms exist in this 2H rhodium-based nanomaterial. Furthermore, the 2H rhodium nanostructure containing interstitial C atoms has poor thermal stability and undergoes a phase transformation to 3C rhodium at temperatures above 250°C in an inert atmosphere.

[0045] According to embodiments of the present invention, the 2H rhodium nanosheets we synthesized do not contain interstitial C atoms, which has been confirmed by a series of characterizations. In addition, the 2H rhodium nanosheets have excellent thermal stability, and the highest temperature at which the 2H rhodium nanosheets maintain thermal stability in an inert atmosphere can reach about 300°C. Specification 6 / 9 pages 9CN 121402641 A

[0046] According to embodiments of the present invention, a compound derivatization method is provided to synthesize 2H rhodium nanosheets with high yield and high crystalline phase purity. Due to the novel stacking order of Rh atoms in Rh₂C and the relatively weak interaction between Rh and C atoms, Rh₂C nanosheets are used as starting materials, allowing C atoms to be extracted from the Rh lattice under relatively mild conditions. After C atom extraction, the orthorhombic Rh₂C nanosheets are transformed into 2H rhodium nanosheets. This method successfully yields rhodium nanomaterials with a pure 2H phase for the first time. Furthermore, by adding a second metal during the C atom extraction process, 2H rhodium-based alloy nanosheets can be obtained. The edge length of the 2H rhodium nanosheets ranges from 5 nm to 50 nm, and the edge width ranges from 2 nm to 20 nm. The thickness of the rhodium nanosheets is approximately 1 to 4 nm. Furthermore, control experiments show that the ultrasmall size and 2D morphology of Rh₂C play an important role in stabilizing the 2H phase in the derived Rh nanomaterials. When large-sized Rh2C nanoflowers with an average diameter of 66.5 nm are used as starting materials, only 3C rhodium products are obtained after C atom extraction. Note that thermal stability studies show that 2H rhodium nanosheets remain stable after annealing at 300 °C for 1 hour in an inert atmosphere, indicating that 2H rhodium nanosheets are expected to be applied in various industrial fields under relatively harsh conditions.

[0047] Exemplary Embodiments

[0048] Example 1. A compound derivatization method for synthesizing pure 2H rhodium nanomaterials, comprising:

[0049] preparing orthorhombic Rh2C nanosheets;

[0050] obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets; and

[0051] obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing a second metal during the C atom extraction process.

[0052] Example 2. The method according to Example 1, wherein the preparation of orthorhombic Rh2C nanosheets comprises:

[0053] dissolving a first predetermined amount of Rh(acac)3 or RhCl3 in a container in a mixed solution containing a second predetermined amount of oleylamine and a third predetermined amount of oleic acid, and subjecting it to ultrasonic treatment for a first predetermined time;

[0054] adding a fourth predetermined amount of formaldehyde to the mixed solution;

[0055] sealing the container and subjecting the container to ultrasonic treatment for a second predetermined time;

[0056] heating the container at a first predetermined temperature for a third predetermined time; and

[0057] cooling the container to room temperature.

[0058] Example 3. The method according to any of the preceding embodiments, further comprising:

[0059] collecting the obtained product by centrifugation at 14000 rpm for 5 minutes;

[0060] washing the obtained product once or multiple times with a mixture of cyclohexane and ethanol (v / v = 1:2); and

[0061] dispersing the obtained product in cyclohexane.

[0062] Example 4According to any of the foregoing embodiments, obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets comprises:

[0063] redispersing the Rh2C nanosheets in a fifth predetermined amount of oleylamine by ultrasonic treatment; and

[0064] heating the solution in an oil bath at a second predetermined temperature for a fourth predetermined time, while simultaneously introducing a mixture of Ar / H2 having a first predetermined H2 volume content into the solution in a bubbling manner at a first predetermined flow rate.

[0065] Example 5. The method according to any of the preceding embodiments, wherein obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing the second metal during C atom extraction comprises:

[0066] redispersing Rh2C nanosheets in a fifth predetermined amount of oleylamine and dissolving a sixth predetermined amount of the first predetermined metal precursor by ultrasonic treatment; and

[0067] heating the solution in an oil bath at a third predetermined temperature for a fifth predetermined time, while simultaneously introducing a mixture of Ar / H2 having a first predetermined percentage of H2 volume content into the solution by bubbling at a first predetermined flow rate. Specification 7 / 9 pages 10 CN 121402641 A

[0068] Example 6. The method according to any of the preceding embodiments, further comprising:

[0069] collecting the obtained product by centrifugation at 14000 rpm for 5 minutes;

[0070] washing the obtained product three times with a mixture of cyclohexane and ethanol (v / v = 1:2); and

[0071] dispersing the obtained product in cyclohexane.

[0072] Example 7. The method according to any of the preceding embodiments, wherein the first predetermined amount is in the range of 1 to 3 mg.

[0073] Example 8. The method according to any of the preceding embodiments, wherein the second predetermined amount is about 2.25 mL.

[0074] Example 9. The method according to any of the preceding embodiments, wherein the third predetermined amount is in the range of 0.1 to 0.3 mL.

[0075] Example 10. The method according to any of the preceding embodiments, wherein the first predetermined time is about 5 minutes.

[0076] Example 11. The method according to any of the preceding embodiments, wherein the fourth predetermined amount is in the range of 0.7 to 0.8 mL.

[0077] Example 12. The method according to any of the preceding embodiments, wherein the second predetermined time is in the range of 5 to 10 minutes.

[0078] Example 13. The method according to any of the preceding embodiments, wherein the first predetermined temperature is in the range of 160 to 200 °C.

[0079] Example 14. The method according to any of the preceding embodiments, wherein the third predetermined time is about 12 hours.

[0080] Example 15. The method according to any of the foregoing embodiments, wherein the fifth predetermined amount is between 2.0 and 4.0 mL.

[0081] Example 16. The method according to any of the preceding embodiments, wherein the second predetermined temperature is in the range of 130 to 160 °C.

[0082] Example 17. The method according to any of the preceding embodiments, wherein the fourth predetermined time is in the range of 16 to 24 hours.

[0083] Example 18. The method according to any of the preceding embodiments, wherein the first predetermined percentage is about 10%.

[0084] Example 19. The method according to any of the preceding embodiments, wherein the first predetermined flow rate is about 50 ml / min.

[0085] Example 20. The method according to any of the preceding embodiments, wherein the sixth predetermined amount is in the range of 0.1 to 1 mg.

[0086] Example 21. The method according to any of the preceding embodiments, wherein the first predetermined metal precursor is a Ru precursor or a Pt precursor.

[0087] Example 22. The method according to any of the preceding embodiments, wherein the fifth predetermined time is in the range of 14 to 20 hours.

[0088] Example 23. The method according to any of the preceding embodiments, wherein the third predetermined temperature is in the range of 140 to 200 °C.

[0089] Example 24. The method according to any of the preceding embodiments, wherein the resulting 2H rhodium nanosheet is constructed having an edge length range of 5 to 50 nm and an edge width range of 2 to 20 nm.

[0090] Example 25. The method according to any of the preceding embodiments, wherein the resulting 2H rhodium nanosheet is constructed having a thickness of about 1 to 4 nm.

[0091] All patents, patent applications, provisional applications and publications mentioned or cited herein are incorporated in their entirety by reference, including all figures and tables, provided that they do not conflict with the express teachings of this specification.

[0092] It should be understood that the examples and embodiments described herein are for illustrative purposes only, and various modifications or changes can be made by those skilled in the art based thereon, and such modifications or changes should be included within the spirit and scope of this application. Furthermore, any element or limitation of any invention or embodiment thereof disclosed herein may be combined with any and / or all other elements or limitations disclosed herein (alone or in any combination) or any other invention or embodiment thereof, and all such combinations are covered within, but not limited to, the scope of this invention. Specification 9 / 9 pages 12 CN 121402641 A Figure 1 Figure 2A Specification Drawings 1 / 32 pages 13 CN 121402641 A Figure 2B Figure 2C Specification Drawings 2 / 32 pages 14 CN 121402641 A Figure 2D Figure 2E Specification Drawings 3 / 32 pages 15 CN 121402641 A Figure 2FFigure 2G, Appendix 4 / 32, Page 16, CN 121402641 A; Figure 3A, Figure 3B, Appendix 5 / 32, Page 17, CN 121402641 A; Figure 4A, Figure 4B, Appendix 6 / 32, Page 18, CN 121402641 A; Figure 4C, Figure 4D, Appendix 7 / 32, Page 19, CN 121402641 A; Figure 4E, Figure 4F, Appendix 8 / 32, Page 20, CN 121402641 A; Figure 4G, Appendix 9 / 32, Page 21, CN 121402641 A; Figure 4H, Figure 4I, Appendix 10 / 32, Page 22, CN 121402641 A; Figure 4J, Figure 5A, Appendix 11 / 32, Page 23, CN 121402641 A; Figure 5B, Figure 6A, Appendix 12 / 32, Page 24, CN 121402641 A Figure 6B Figure 6C Appendix 13 / 32 Page 25 CN 121402641 A Figure 6D Figure 6E Appendix 14 / 32 Page 26 CN 121402641 A Figure 6F Figure 7A Appendix 15 / 32 Page 27 CN 121402641 A Figure 7B Figure 7C Appendix 16 / 32 Page 28 CN 121402641 A Figure 8A Figure 8B Appendix 17 / 32 Page 29 CN 121402641 A Figure 8C Figure 9 Appendix 18 / 32 Page 30 CN 121402641 A Figure 10A Figure 10B Appendix 19 / 32 Page 31 CN 121402641 A Figure 10C Figure 10D Appendix 20 / 32 Page 32 CN 121402641 A Figure 10E, Appendix to the Instruction Manual, Page 21 / 32, 33 CN 121402641 A; Figure 11A, Figure 11B, Appendix to the Instruction Manual, Page 22 / 32, 34 CN 121402641 A; Figure 11C, Figure 12A, Appendix to the Instruction Manual, Page 23 / 32, 35 CN 121402641 A; Figure 12B, Figure 13, Appendix to the Instruction Manual, Page 24 / 32, 36 CN 121402641 A; Figure 14A, Figure 14B, Appendix to the Instruction Manual, Page 25 / 32, 37 CN 121402641 A; Figure 14C, Figure 14D, Appendix to the Instruction Manual, Page 26 / 32, 38 CN121402641 A Figure 14E Figure 14F Appendix 27 / 32 Page 39 CN 121402641 A Figure 14G Figure 14H Appendix 28 / 32 Page 40 CN 121402641 A Figure 15A Figure 15B Appendix 29 / 32 Page 41 CN 121402641 A Figure 15C Figure 15D Appendix 30 / 32 Page 42 CN 121402641 A Figure 16A Figure 16B Appendix 31 / 32 Page 43 CN 121402641 A Figure 16C Appendix 32 / 32 Page 44 CN 121402641 A ABSTRACT A compounds-derived method for synthesizing 2H R and 2H Rh-based alloy nanomaterials is provided. The method includes preparing orthorhombic phase Rh2C NPLs; obtaining This invention provides a compound derivatization method for synthesizing 2H rhodium (Rh) and 2H rhodium-based alloy nanomaterials. The method includes: preparing orthorhombic Rh₂C nanosheets (NPLs); obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh₂C nanosheets; and obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing the second metal during the C atom extraction process.

Claims

1. A compound derivatization method for synthesizing 2H rhodium and 2H rhodium-based alloy nanomaterials, comprising: Preparation of orthorhombic Rh2C nanosheets; Pure 2H rhodium nanosheets were obtained by extracting C atoms from the Rh2C nanosheets; as well as 2H rhodium-based alloy nanosheets were obtained by simultaneously reducing a second metal during the C atom extraction process.

2. The method according to claim 1, wherein preparing orthorhombic Rh2C nanosheets comprises: A first predetermined amount of Rh(acac)3 or RhCl3 is dissolved in a container in a mixed solution containing a second predetermined amount of oleylamine and a third predetermined amount of oleic acid, and then subjected to ultrasonic treatment for a first predetermined time. A fourth predetermined amount of formaldehyde is added to the mixed solution; The container is sealed and subjected to ultrasonic treatment for a second predetermined time; Heating the container at a first predetermined temperature for a third predetermined time; and Cool the container to room temperature.

3. The method according to claim 2, further comprising: The product was collected by centrifugation at 14,000 rpm for 5 minutes. The resulting product was washed once or multiple times with a mixture of cyclohexane and ethanol (v / v = 1:2); and The obtained product was dispersed in cyclohexane.

4. The method of claim 1, wherein obtaining pure 2H rhodium nanosheets by extracting C atoms from the Rh2C nanosheets comprises: The Rh2C nanosheets were redispersed in a fifth predetermined amount of oleylamine by ultrasonic treatment; as well as The solution is heated in an oil bath at a second predetermined temperature for a fourth predetermined time, while simultaneously a mixture of Ar / H2 having a first predetermined H2 volume content is bubbled into the solution at a first predetermined flow rate.

5. The method according to claim 1, wherein, Obtaining 2H rhodium-based alloy nanosheets by simultaneously reducing the second metal during C atom extraction includes: The Rh2C nanosheets were redispersed and the first predetermined metal precursor was dissolved in a fifth predetermined amount of oleylamine by ultrasonic treatment; and The solution is heated in an oil bath at a third predetermined temperature for a fifth predetermined time, while simultaneously a mixture of Ar / H2 having a first predetermined H2 volume content is bubbled into the solution at the first predetermined flow rate.

6. The method according to claim 4, further comprising: The product was collected by centrifugation at 14,000 rpm for 5 minutes. The obtained product was washed three times with a mixture of cyclohexane and ethanol (v / v = 1:2); and The obtained product was dispersed in cyclohexane.

7. The method according to claim 5, further comprising: The product was collected by centrifugation at 14,000 rpm for 5 minutes. The obtained product was washed three times with a mixture of cyclohexane and ethanol (v / v = 1:2); and The obtained product was dispersed in cyclohexane.

8. The method of claim 2, wherein the first predetermined amount is in the range of 1 to 3 mg.

9. The method according to claim 2, wherein the second predetermined amount is approximately 2.25 mL.

10. The method of claim 2, wherein the third predetermined amount is in the range of 0.1 to 0.3 mL.

11. The method of claim 2, wherein the first predetermined time is approximately 5 minutes.

12. The method of claim 2, wherein the fourth predetermined amount is in the range of 0.7 to 0.8 mL.

13. The method of claim 2, wherein the second predetermined time is in the range of 5 to 10 minutes.

14. The method of claim 2, wherein the first predetermined temperature is in the range of 160 to 200°C.

15. The method of claim 2, wherein the third predetermined time is approximately 12 hours.

16. The method of claim 4, wherein the fifth predetermined amount is in the range of 2.0 to 4.0 mL.

17. The method of claim 4, wherein the second predetermined temperature is in the range of 130 to 160°C.

18. The method of claim 4, wherein the fourth predetermined time is in the range of 16 to 24 hours.

19. The method of claim 4, wherein the first predetermined percentage is approximately 10%.

20. The method of claim 4, wherein the first predetermined flow rate is approximately 50 ml / min.

21. The method of claim 5, wherein the sixth predetermined amount is in the range of 0.1 to 1 mg.

22. The method of claim 5, wherein the first predetermined metal precursor is a Ru precursor or a Pt precursor.

23. The method of claim 5, wherein the third predetermined temperature is in the range of 140 to 200°C.

24. The method of claim 5, wherein the fifth predetermined time is in the range of 14 to 20 hours.

25. The method of claim 1, wherein the resulting 2H rhodium nanosheets are configured to have an edge length range of 5 to 50 nm and an edge width range of 2 to 20 nm.

26. The method of claim 1, wherein the resulting 2H rhodium nanosheets are configured to have a thickness of about 1 to 4 nm.

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