A method for electron beam-induced and hot field-assisted fabrication of novel PdO x / Pd heterojunction materials

Abstract

The application provides a method for preparing a novel PdO x / Pd heterojunction material by electron beam induction and thermal field cooperation, and relates to the fields of irradiation chemistry and nanomaterial preparation technology. The method comprises the steps of electron beam irradiation on the [001] crystal band axis of a substrate palladium with a face-centered cubic structure, and heating the substrate target to 600-750 DEG C while the electron beam irradiation is performed, and keeping the temperature for 1-60 min. The preparation process of the application is simple, the product is high in purity, good in repeatability, short in reaction period, and the synergistic effect of electron beam irradiation and heating is used to induce surface reconstruction and oxidation of the substrate palladium, and in-situ synthesis of PdO x / Pd heterojunction material. The application realizes visual synthesis and controllable preparation of the PdO x / Pd heterojunction material, and has important research value and wide application prospect in the fields of catalysis, gas sensor, hydrogen storage material and corrosion-resistant coating.

Description

Technical Field

[0001] This invention relates to the fields of radiation chemistry and nanomaterial preparation technology, and particularly to a novel PdO preparation method using electron beam induction and thermal field synergy. x / Pd heterojunction material method. Background Technology

[0002] Noble metal nanocatalysts play an irreplaceable role in catalysis, energy, and electronic devices due to their unique electronic structure, superior chemical stability, and tunable catalytic activity. The physical and chemical properties of these materials largely depend on the local coordination environment of the metal center, such as its oxidation state, coordination number, and specific coordination configuration. Some noble metals, such as Au, Rh, and Ru, can control their atomic arrangement under electron beam irradiation, achieving controlled structural transformations.

[0003] The noble metal Pd (palladium) has demonstrated key application value in energy and catalysis fields due to its unique electronic structure and excellent catalytic performance. Currently, the traditional wet chemical method for preparing oxide / metal heterostructure materials inevitably introduces impurities, and it is difficult to control the size and morphology uniformity of the products, making it difficult to observe the formation process of heterostructures in situ at the atomic scale.

[0004] Furthermore, studies have shown that electron beam irradiation can induce the decomposition of icosahedral Pd nanocrystals into small-particle metastable hexagonal Pd. Although electron beam irradiation technology has been extensively studied as an effective means of inducing phase transitions in materials, existing techniques largely focus on transitions between known phases. More importantly, under a single external field, palladium typically tends to maintain its thermodynamically stable face-centered cubic structure or undergo known grain coarsening. This general understanding of stability limits the initiative in exploring new structures and phases.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a novel method for preparing PdO using a combination of electron beam induction and thermal field synergy. x / Pd heterojunction material method.

[0007] In a first aspect, the present invention provides a novel method for the synergistic preparation of PdO by electron beam induction and thermal field. x A method for producing Pd heterojunction materials includes the step of irradiating the

[001] zone axis of a palladium substrate having a face-centered cubic structure with an electron beam, wherein the substrate target is heated to 600~750°C and held at that temperature for 1~60 min during the electron beam irradiation.

[0008] The preparation process of this invention is simple, employing a one-step in-situ process. The entire process of morphological transformation, surface reconstruction, and oxidation can be completed within a single device simply by loading the raw materials onto a chip and placing it under a transmission electron microscope. During preparation, the substrate target is simultaneously subjected to electron beam irradiation and heating. The synergistic effect of electron beam irradiation and heating induces surface reconstruction and oxidation of the palladium on the substrate, resulting in the in-situ synthesis of novel PdO. x / Pd heterojunction material, whose crystal structure differs from that of palladium and its compounds in existing technologies, is a novel stable PdO. x / Pd heterojunction material; newly formed PdO x The structure can be labeled as: Pd(001)-(√10×√10)R18.4°-O.

[0009] This method eliminates the need for additional chemical reagents during preparation, thus avoiding the presence of external impurities and ensuring the high purity of the final heterojunction material product. The reaction pathway is mainly controlled by electron beam irradiation and temperature, without relying on harsh chemical environments or complex kinetic equilibrium, resulting in excellent reproducibility. Furthermore, the entire process of in-situ synthesis of heterojunction materials through electron beam irradiation and synergistic heating can typically be completed within 1-2 hours, significantly improving preparation efficiency.

[0010] Furthermore, during the heating process, the substrate target is first heated to a temperature of 400~650℃ and held for 1~60 minutes, and then the temperature is further increased to a temperature of 600~750℃ and held for 1~60 minutes; and the temperature of the substrate target after the first heating is lower than the temperature after the second heating.

[0011] Furthermore, the electron beam irradiation is performed in a vacuum degree ≤9×10⁻⁶. -6 Performed at Pa.

[0012] Preferably, the vacuum degree is 4×10⁻⁶. -6 ~7×10 -6 Pa.

[0013] Furthermore, the parameters of the electron beam irradiation also include: an electron beam current of 68~285pA, and / or an electron beam accelerating voltage of 80~300kV.

[0014] Furthermore, the base palladium is elemental palladium, and its average particle size is 21.98 nm ± 2.85 nm, preferably 22 nm.

[0015] Preferably, the palladium substrate is a nanoparticle, nanowire, nanoribbon, nanotube, or thin film.

[0016] The palladium substrate of the present invention can be any material with the above-mentioned characteristics found in the prior art. In one optional embodiment of the present invention, the substrate target is obtained by methods including but not limited to the following preparation methods: First, polyvinylpyrrolidone, potassium bromide, L-ascorbic acid and water are mixed and dissolved to obtain a mixed solution; then sodium tetrachloropalladium(II) is dissolved in water to obtain a sodium tetrachloropalladium solution; then the sodium tetrachloropalladium solution and the mixed solution are mixed evenly and reacted in an oil bath at 80°C for 8 h; after cooling, the mixture is centrifuged, the precipitate is collected and washed with washing solution, and then dried.

[0017] Preferably, the amount of polyvinylpyrrolidone is 105 mg, the amount of potassium bromide is 900 mg, the amount of L-ascorbic acid is 40 mg, and the amount of water used to mix polyvinylpyrrolidone, potassium bromide, and L-ascorbic acid is 8 mL.

[0018] Preferably, the temperature during the mixing and dissolution process is 80°C, and the time is 15 minutes.

[0019] Preferably, the mass-to-volume ratio of sodium tetrachloropalladium(II) to water is 40 mg: 3 mL.

[0020] Preferably, the centrifugation speed is 10,000 rpm and the time is 10 min.

[0021] Preferably, the washing liquid comprises ethanol and water in a volume ratio of 1:1.

[0022] Preferably, the drying temperature is 80°C and the drying time is 12 hours.

[0023] Furthermore, the method includes the following steps: (1) The base palladium was dispersed in ethanol to obtain a Pd suspension; (2) The Pd suspension is coated onto the carrier chip and then dried; (3) The substrate target mounted on the carrier chip is subjected to electron beam irradiation, and the substrate target is subjected to the heating treatment at the same time during the electron beam irradiation.

[0024] Furthermore, the palladium base is provided in powder form, and its mass-to-volume ratio with the ethanol is 1~10 mg:1 mL, preferably 10 mg:1 mL.

[0025] Furthermore, the drying temperature is 60~90℃, and the drying time is 8~12h.

[0026] Preferably, the drying temperature is 80°C and the drying time is 12 hours.

[0027] In one optional embodiment of the present invention, the method includes the following steps: S1, ultrasonically dispersing the substrate target in ethanol to obtain a Pd suspension; S2. Take 2.5 μL of the Pd suspension, drop it onto the carrier chip, and then dry it; S3. Mount the carrier chip loaded with the substrate target onto the in-situ heating rod of the transmission electron microscope, under a vacuum degree ≤9×10⁻⁶. -6 Under the condition of Pa, the substrate target is tilted to the direction of the zone axis; S4. Electron beam irradiation is performed along the

[001] zone axis of the substrate target using an electron microscope. Under electron beam irradiation, the substrate target is first heated to a temperature of 400~650℃ and held for 1~60min to induce morphological evolution of cubic palladium. S5. Subsequently, the temperature is further increased, and the substrate target is heated a second time to 600~750℃, with the temperature of the substrate target after the first heating being higher than that after the second heating. Electron beam irradiation continues, causing further oxidation and reconstruction of cubic palladium, completing the evolution of morphology and structure, and forming PdO in situ. x / Pd heterojunction material.

[0028] In the above scheme, under the synergistic effect of electron beam irradiation and heating in a high vacuum environment, the entire process of morphological transformation, surface reconstruction, and oxidation is completed under a microscope, realizing a novel PdO. x The visualized synthesis and controllable preparation of Pd heterojunction materials have significant research value and broad application prospects in fields such as catalysis, gas sensors, hydrogen storage materials, and anti-corrosion coatings.

[0029] Preferably, the ultrasonic dispersion time in S1 is 20-30 minutes.

[0030] A second aspect of the present invention provides a novel PdO obtained by the above method. x / Pd heterojunction materials or novel PdO prepared by the above method x Composite materials of Pd heterojunction materials.

[0031] This invention, driven by a combination of heating and electron beam irradiation, forms a reconstructed structure (PdO) on the surface of a substrate target with a crystal plane spacing of approximately 1.26 nm and an angle of approximately 18.29° with the Pd(001) substrate. x Newly formed PdO x The structure can be labeled as: Pd(001)-(√10×√10)R18.4°-O.

[0032] A third aspect of the present invention provides a novel PdO prepared by the above-described preparation method. xApplications of Pd heterojunction materials in the preparation of catalysts, gas sensors, hydrogen storage materials and anti-corrosion coatings.

[0033] This invention provides a novel PdO preparation method using electron beam induction and thermal field synergy. x The beneficial effects of the method for preparing Pd heterojunction materials are at least as follows: the preparation process of this invention is simple, the product has high purity, good reproducibility, and a short reaction cycle. It utilizes the synergistic effect of electron beam irradiation and heating to induce surface reconstruction and oxidation of the substrate palladium, achieving in-situ synthesis of PdO. x / Pd heterojunction materials, realizing PdO x The visualized synthesis and controllable preparation of Pd heterojunction materials have significant research value and broad application prospects in fields such as catalysis, gas sensors, hydrogen storage materials, and anti-corrosion coatings. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 This describes the size and morphology of cubic palladium nanoparticles.

[0036] Figure 2 This is the X-ray diffraction (XRD) pattern of cubic palladium nanoparticles.

[0037] Figure 3 The HAADF-STEM characterization and FFT diffraction pattern of cubic palladium nanoparticles are shown.

[0038] Figure 4 This is an EDS elemental surface distribution analysis of cubic palladium nanoparticles.

[0039] Figure 5 The novel PdO prepared in the examples x Schematic diagram of the apparatus and method for Pd heterojunction materials.

[0040] Figure 6 These are in-situ series diagrams of the surface reconstruction process of cubic target nanoparticles in Example 1.

[0041] Figure 7 This is the evolution of the surface structure of the cubic target nanoparticles in Example 1 before and after heating and electron beam irradiation treatment.

[0042] Figure 8 This is the calibration of surface reconstruction Pd(001)-(√10×√10)R18.4°-O in Example 1.

[0043] Figure 9 It is the novel PdO in Example 1 x / Pd heterojunction material composition distribution.

[0044] Figure 10 This is the in-situ morphological evolution process of cubic Pd nanoparticles in Comparative Example 1 under the synergistic effect of heating and electron beam irradiation.

[0045] Figure 11 This describes the in-situ morphological evolution of cubic Pd nanoparticles in Comparative Example 2 after being heated and then irradiated with an electron beam.

[0046] Figure 12 This describes the in-situ morphological evolution of cubic Pd nanoparticles in Comparative Example 3 after irradiation followed by heat treatment. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0048] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0049] All chemical reagents used in this experiment were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and were not further purified before use. Specific reagent information is as follows: Polyvinylpyrrolidone (PVP, powder, average Mw ~55000, CAS: 9003-39-8); Sodium tetrachloropalladium (Na2PdCl4, purity ≥99.99%, CAS: 13820-53-6); L-ascorbic acid (ultra-pure grade, ≥99.5%, CAS: 50-81-7); Potassium bromide (purity ≥99.99%, CAS: 7758-02-3); Deionized water (GC grade, CAS: 7732-18-5); Ethanol (HPLC grade, ≥99.8%, CAS: 64-17-5).

[0050] In this invention, the substrate target can be prepared using the solution method in the prior art, with an average particle size of 21.98 nm ± 2.85 nm and a face-centered cubic structure, such as M. Jin, H. Liu, H. Zhang, Z. Xie, J. Liu, Y. Xia. Synthesis of Pd nanocrystals enclosed by {100} facets and with sizes < 10 nm for application in CO oxidation [J]. Nano Research, 2011, 4(1): 83-91.

[0051] For further illustration, the substrate targets used in the following embodiments and comparative examples were prepared using methods including, but not limited to, the following preparation methods: Add 105 mg of polyvinylpyrrolidone, 900 mg of potassium bromide, 40 mg of L-ascorbic acid, and 8 mL of deionized water to a 20 mL glass bottle. Place the solution in an oil bath at 80 °C and stir magnetically for 15 min until the reagents are completely dissolved, obtaining a mixed solution. Next, dissolve 40 mg of sodium tetrachloropalladium(II) in 3 mL of deionized water and sonicate for 5 min to obtain a sodium tetrachloropalladium solution. Pour the sodium tetrachloropalladium solution into the mixed solution and react in an oil bath at 80 °C for 8 h. After cooling to room temperature, centrifuge at 10000 rpm for 10 min to collect the precipitate. Wash the product three times with 5 mL of ethanol and 5 mL of water. Finally, dry in an oven at 80 °C for 12 h to obtain a palladium substrate with a face-centered cubic structure, named cubic palladium nanoparticles.

[0052] The size and morphology characterization of the cubic palladium nanoparticles are as follows: Figure 1 As shown, Figure 1 Image a is a low-magnification TEM image of cubic palladium nanoparticles, showing that the synthesized particles are basically cubic in morphology. Figure 1 b is a statistical histogram of particle size distribution based on a. Statistical results show that the particle size distribution is uniform, with an average particle size of approximately 22 nm.

[0053] The X-ray diffraction (XRD) pattern of the cubic palladium nanoparticles is as follows: Figure 2 As shown, the position and intensity of its diffraction peaks indicate that the product is a well-crystallized face-centered cubic (fcc) structure metallic palladium.

[0054] The HAADF-STEM characterization and FFT diffraction pattern of the cubic palladium nanoparticles are as follows: Figure 3 As shown, Figure 3 Image a is a low-magnification HAADF-STEM image of cubic palladium particles. Figure 3b and c are magnified images of the orange dashed box region in a and their corresponding FFT diffraction patterns, respectively, where the orange circles mark the diffraction spots of the

[001] zone axis.

[0055] The EDS elemental surface distribution analysis of the cubic palladium nanoparticles is as follows: Figure 4 As shown. Figure 4 a and b are EDS elemental surface distribution diagrams of cubic palladium, which intuitively show the two-dimensional spatial distribution of the elements. Figure 4 The 'c' represents the corresponding EDS energy spectrum. The spectrum shows the presence of four elements in the sample: Pd, C, Cu, and Al. The C signal primarily originates from the ethanol dispersant used in the preparation process, the Cu signal comes from the copper mesh supporting the TEM, and the Al signal typically originates from the detector window material of the EDS spectrometer, representing a common instrument background signal.

[0056] The following examples demonstrate the preparation of novel PdO using electron beam induction and thermal field synergy. x A schematic diagram of the apparatus and method for Pd heterojunction materials is shown below. Figure 5 As shown.

[0057] Example 1 This embodiment provides a novel PdO preparation method using electron beam induction and thermal field synergy. x The method for using Pd heterojunction materials includes the following steps: (1) 10 mg of the above cubic palladium nanoparticles (substrate target) were directly dispersed in 1 mL of ethanol and sonicated for 30 min to form a uniform Pd suspension. (2) Take 2.5 μL of the Pd suspension and drop it onto the heating chip (specifically SiN). x Heat the chip, then place it in an 80℃ oven to dry for 12 hours; (3) The heated chip loaded with the substrate target was mounted on the in-situ heating rod of the transmission electron microscope, and accelerated at 300kV and 6.5×10 -6 Under a vacuum environment, the substrate target is tilted to the

[001] zone axis direction; (4) Under 115pA electron beam irradiation, the substrate target was heated from room temperature to 650°C and held for 15 min to induce a morphological transformation of cubic Pd particles from cubic to spherical. (5) Then, the temperature was raised to 700°C and irradiated with an electron beam of 115 pA for 15 min to further oxidize the cubic palladium and convert it in situ into a novel PdO. x / Pd heterojunction materials; (6) After irradiation, turn off the heating program and electron beam, and remove the heating chip.

[0058] The novel PdO prepared in Example 1 xThe / Pd heterojunction material was tested, and the test results are as follows: Figures 6-8 As shown. Figure 6 The surface reconstruction process of the cubic target nanoparticles in Example 1 is demonstrated. Figure 6 The face-centered cubic Pd structure is transformed into a novel PdO by continuous irradiation along the

[001] band axis. x A series of in-situ HAADF-STEM images of the / Pd heterojunction material. Below each sub-image is the FFT diffraction pattern of the corresponding region, where the red circles indicate the diffraction spots of Pd in ​​the

[001] direction. Figure 6 In the image: a was taken when heated to 650℃; b was taken after holding at that temperature for 1024s based on a; c and d were taken after heating to 700℃ and holding at that temperature for 121s, 736s, 742s, and 749s, respectively. PdO was measured from f. x The structure forms an angle of approximately 18.29° with the Pd(001) substrate.

[0059] Figure 7 The evolution of the surface structure of the cubic target nanoparticles in Example 1 before and after heating and electron beam irradiation treatment is shown. Figure 7 a and b represent the transformation of face-centered cubic Pd into novel PdO. x HAADF-STEM image of / Pd heterojunction material. Figure 7 c is Figure 7 The magnified HAADF plot corresponding to a shows that the measured interplanar spacing of 0.20 nm is consistent with the {001} crystal plane family of Pd. Figure 7 d is Figure 7 The magnified view corresponding to b shows that the 1.26 nm lattice spacing corresponds to the novel PdO. x The reconstructed surface structure.

[0060] Figure 8 PdO in Example 1 is shown x The calibration result of the structure is named Pd(001)-(√10×√10)R18.4°-O. Figure 8 a and b are magnified images of the high-angle annular dark field (HAADF) after surface reconstruction and their corresponding Fast Fourier Transform (FFT) plots, respectively. Orange and red in the figures represent PdO₂ and PdO₂, respectively. x With Pd phase. The orange dashed box in Figure a represents a typical reconstruction unit, and the lattice basis vectors of the surface reconstruction are calculated (a s , b s It is √10 times the size of the substrate lattice (a, b). Figure 8In sample b, a reconstructed structure was observed on the surface of the Pd nanocube with an interplanar spacing of approximately 1.26 nm and an angle of approximately 18.29° with the Pd(001) substrate. According to Wood's nomenclature (WOOD E A. Vocabulary of surface crystallography[J].Journal of Applied Physics, 1964, 35(4): 1306-1312.), the newly formed PdO... x The structure can be labeled as: Pd(001)-(√10×√10)R18.4°-O.

[0061] Figure 9 The novel PdO in Example 1 x / Pd heterojunction material composition distribution. Figure 9 At high magnification, α represents a novel PdO4 material in heterojunctions. x Perforations are formed by targeted etching of the surface area. Figure 9 b represents the FFT analysis performed on the red dashed area in a, and the results show that the perforated lower layer still maintains the face-centered cubic structure of Pd. Figure 9 c is a pair Figure 9 FFT analysis of the blue dashed area in region a confirmed that the surface reconstruction product is a novel type of PdO. x . Figure 9 The df is Figure 9 The electron energy loss spectrum corresponding to a is shown, where red and green represent the elemental distribution of O and Pd, respectively, characterizing the elemental distribution and chemical state of the heterojunction material. Figure 9 g represents the EELS line scan spectrum across the heterojunction material interface (scanning direction as shown in the image). Figure 9 (As shown in diagram a, from A to C). Point A (SiN) x No O signal was detected at point A (substrate) and point B (face-centered cubic Pd), while no O signal was detected at point C (novel PdO). x The presence of a distinct OK edge characteristic peak at this location directly confirms that oxygen is specifically enriched in the surface reconstruction product PdO. x middle.

[0062] Example 2 This embodiment provides a novel PdO preparation method using electron beam induction and thermal field synergy. x The method for using Pd heterojunction materials includes the following steps: (1) 10 mg of the above cubic palladium nanoparticles (substrate target) were directly dispersed in 1 mL of ethanol and sonicated for 30 min to form a uniform Pd suspension. (2) Take 2.5 μL of the Pd suspension and drop it onto the heating chip (specifically SiN). xHeat the chip, then place it in an 80℃ oven to dry for 12 hours; (3) The heated chip loaded with the substrate target was mounted on the in-situ heating rod of the transmission electron microscope, and accelerated at 300kV and 6.0×10 -6 Under a vacuum environment, the substrate target is tilted to the

[001] zone axis direction; (4) Under 115pA electron beam irradiation, the substrate target was heated from room temperature to 550°C and held for 25 min to induce a morphological transformation of cubic Pd particles from cubic to spherical. (5) Then, the temperature was raised to 680°C and irradiated with a 115 pA electron beam for 18 min to further oxidize the cubic palladium and convert it in situ into a novel PdO. x / Pd heterojunction material.

[0063] Example 3 This embodiment provides a novel PdO preparation method using electron beam induction and thermal field synergy. x The method for using Pd heterojunction materials includes the following steps: (1) 10 mg of the above cubic palladium nanoparticles (substrate target) were directly dispersed in 1 mL of ethanol and sonicated for 20 min to form a uniform Pd suspension. (2) Take 2.5 μL of the Pd suspension and drop it onto the heating chip (specifically SiN). x Heat the chip, then place it in an 80℃ oven to dry for 12 hours; (3) The heated chip loaded with the substrate target was mounted on the in-situ heating rod of the transmission electron microscope, and accelerated at 300kV and 5.4×10 -6 Under a vacuum environment, the substrate target is tilted to the

[001] zone axis direction; (4) Under 115pA electron beam irradiation, the substrate target was heated from room temperature to 580℃ and held for 20 min to induce the cubic Pd particles to undergo a morphological transformation from cubic to spherical. (5) Then, the temperature was raised to 670°C and irradiated with a 115 pA electron beam for 20 min to further oxidize the cubic palladium and convert it in situ into a novel PdO. x / Pd heterojunction material.

[0064] Comparative Example 1 This comparative example is basically the same as Example 1, except for the following steps: (4) Under 115pA electron beam irradiation, the substrate target was heated to 400℃ and held for 14 min; (5) Then heat to 500°C and continue to irradiate with an electron beam of 115pA for 18 minutes.

[0065] Figure 10 The in-situ morphological evolution of cubic Pd nanoparticles in Comparative Example 1 under the synergistic effect of heating and electron beam irradiation is shown. Figure 10 The ac images are a series of in-situ images showing the gradual evolution of the morphology of cubic Pd particles from cubic to spherical during continuous irradiation along the

[001] belt axis. Figure 10 The df values ​​are respectively Figure 10 The ac corresponds to the diffraction pattern of the FFT plot, where the orange circle indicates the diffraction spot in the

[001] direction. Figure 10 In the images: a was taken when heated to 400℃, b was taken after holding the temperature for 14 minutes based on a, and c was taken after heating to 500℃ and holding the temperature for 18 minutes.

[0066] Experimental results show that, compared to Examples 1, 2, and 3, even under the synergistic effect of heating and electron beam irradiation, heating and irradiation below 600°C only induces the particle morphology to change from cubic to spherical, resulting in morphological evolution. The STEM images and corresponding FFT signals do not show new diffraction points, indicating that no new crystal structure is formed. Therefore, below 600°C, simply extending the heating and holding time and the electron beam irradiation time cannot induce PdO… x The formation of the structure.

[0067] Comparative Example 2 This comparative example is basically the same as Example 1, except for the following steps: (4) No irradiation treatment is performed during heating. The substrate target is directly heated from room temperature to 600°C and held for 1 hour and 28 minutes, and then heated to 700°C and held for 4 hours and 19 minutes.

[0068] (5) Then, the temperature was lowered to room temperature, the heating program was turned off, and the chip was irradiated for 2 hours and 11 minutes at an electron beam intensity of 115 pA. After the irradiation was completed, the electron beam was turned off and the heating chip was removed.

[0069] Figure 11 The in-situ morphological evolution of cubic Pd nanoparticles in Comparative Example 2 is shown. The process of morphological evolution under the treatment of heating followed by electron beam irradiation is demonstrated. Figure 11 The ac values ​​indicate that in this comparative example, when cubic Pd nanoparticles were heated along the

[001] zone axis at 600°C for about 1.5 hours, their morphology gradually became rounded, but the overall shape still maintained a cubic outline. Subsequently, the temperature was raised to 700°C and heated for another 4 hours, and the morphology basically transformed into a spherical shape. Figure 11 The df values ​​are respectively Figure 11 The FFT diffraction pattern corresponding to ac. The diffraction spots in the

[001] direction marked by the orange circle are clearly visible, indicating that the face-centered cubic crystal structure of the particles is maintained after long-term high-temperature heating. Figure 11gi is a sequence of HAADF images taken after the particles were cooled to room temperature and then individually irradiated with an electron beam along the

[001] zone axis for about 3 hours (the electron beam was only turned on during the image capture). An amorphous layer appeared on the outermost layer of the particles, but their crystal structure remained unchanged. Figure 11 The jm are respectively Figure 11 The FFT diffraction pattern corresponding to gi. The orange circle also indicates a clear diffraction spot in the

[001] direction, confirming that the treatment of heating before irradiation did not change the structure of the particles. Figure 11 In the image: a was taken at room temperature; b was taken after heating to 600℃ and holding for 1 hour and 28 minutes; c was taken after heating to 700℃ and holding for 4 hours and 19 minutes; g was taken after cooling to room temperature; h was taken after irradiating for 55 minutes based on g; and i was taken after irradiating for 2 hours and 11 minutes based on g.

[0070] Experimental results show that, compared to Examples 1, 2, and 3, the method of heating followed by irradiation only changes the particle morphology from cubic to spherical during heating alone. Subsequent irradiation causes some amorphous layers to appear on the particle surface. The STEM images and FFT signals of the synthesized material do not show new diffraction points, indicating that no new crystal structure is formed. Furthermore, this comparative example also shows that even at higher temperatures and with extended processing times, PdO cannot be formed. x Furthermore, this comparative example further demonstrates that, under the influence of a single external field such as thermal field or electron beam irradiation, even increasing the temperature to a higher level of 700°C and significantly extending the processing time cannot induce PdO. x The formation of the structure.

[0071] Comparative Example 3 This comparative example is basically the same as Example 1, except for the following steps: (4) Turn off the heating program and irradiate for 1 hour and 46 minutes at room temperature and an electron beam intensity of 115 pA.

[0072] (5) Then, the electron beam was turned off, and the substrate target was heated from room temperature to 700°C and held for 2 hours and 5 minutes. After heating was completed, the heating program was turned off and the heated chip was removed.

[0073] Figure 12 The in-situ morphological evolution of cubic Pd nanoparticles in Comparative Example 3 after irradiation followed by heat treatment is shown. Figure 12 'a' is the HAADF image of the initial cubic palladium particle along the

[001] zone axis. Figure 12 d is Figure 12 The FFT diffraction pattern corresponding to a is shown in orange circles, which indicate the diffraction spots in the

[001] direction. Figure 12b is a HAADF image of the particles after they have been individually irradiated with an electron beam at room temperature for about 2 hours. Figure 12 e is Figure 12 The FFT diffraction pattern corresponding to b shows that the clear diffraction spots within the orange circles indicate that the face-centered cubic structure of the particles was maintained after long-term irradiation. Figure 12 c is the HAADF image after the same particle was subsequently heated at 700°C for about 2 hours (timing started from the point of heating to 700°C). Figure 12 f is Figure 12 The FFT diffraction pattern corresponding to c, with the orange circle also indicating clear diffraction spots in the

[001] direction, confirms that the treatment of irradiation followed by heating did not change the face-centered cubic crystal structure of the particles.

[0074] Experimental results show that, compared to Examples 1, 2, and 3, the irradiation-following-heat treatment only changed the particle morphology from cubic to spherical. The STEM images and corresponding FFT signals did not show any new diffraction points, indicating that no new crystal structure was formed. Furthermore, this comparative example further demonstrates that even with a significantly extended initial electron beam irradiation time of 2 hours, and subsequent treatment at temperatures as high as 700°C, the irradiation-following-heating approach could not induce PdO. x The formation of the structure.

[0075] Comparative Examples 1, 2, and 3 together illustrate that the morphological evolution from a cube to a spheroid is mainly driven by thermal effects; the introduction of an electron beam plays a secondary role in this process, its main function being to accelerate this thermal effect process rather than to provide the dominant driving force.

[0076] The above results indicate that novel PdO can be reconstructed from the surface of a face-centered cubic palladium structure. x It depends on the synergistic effect of heating and electron beam irradiation; neither can be dispensed with. The application of any single physical field, or the stepwise superposition of the two (regardless of the order), cannot induce a change in the surface reconstruction process.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel PdO preparation method using electron beam induction and thermal field synergistic synthesis x A method for producing Pd heterojunction materials, comprising the step of electron beam irradiation of the [001] zone axis of a palladium substrate having a face-centered cubic structure, characterized in that... During the electron beam irradiation, the substrate target is heated to 600~750℃ and held at that temperature for 1~60 minutes.

2. The novel PdO prepared by electron beam induction and thermal field synergistic method according to claim 1 x The method for using Pd heterojunction materials is characterized by... During heating, the substrate target is first heated to a temperature of 400~650℃ and held for 1~60 minutes. Then, the temperature is increased again to a temperature of 600~750℃ and held for 1~60 minutes. The temperature of the substrate target after the first heating is lower than the temperature after the second heating.

3. The novel PdO prepared by electron beam induction and thermal field synergistic method according to claim 1 or 2 x The method for using Pd heterojunction materials is characterized by... The electron beam irradiation is performed in a vacuum degree ≤9×10 -6 Performed under Pa; Preferably, the vacuum degree is 4×10⁻⁶. -6 ~7×10 -6 Pa.

4. The novel PdO prepared by electron beam induction and thermal field synergistic method according to any one of claims 1 to 3 x The method for using Pd heterojunction materials is characterized by... The parameters of the electron beam irradiation also include: an electron beam current of 68~285pA, and / or an electron beam accelerating voltage of 80~300kV.

5. The novel PdO prepared by electron beam induction and thermal field synergistic method according to any one of claims 1 to 4 x The method for using Pd heterojunction materials is characterized by... The base palladium is elemental palladium, and its average particle size is 21.98 nm ± 2.85 nm; Preferably, the palladium substrate is a nanoparticle, nanowire, nanoribbon, nanotube, or thin film.

6. The novel PdO prepared by electron beam induction and thermal field synergistic method according to any one of claims 1 to 5 x The method for using Pd heterojunction materials is characterized by... Includes the following steps: (1) The base palladium was dispersed in ethanol to obtain a Pd suspension; (2) The Pd suspension is coated onto the carrier chip and then dried; (3) The substrate target mounted on the carrier chip is subjected to electron beam irradiation, and the substrate target is subjected to the heating treatment at the same time during the electron beam irradiation.

7. The novel PdO prepared by electron beam induction and thermal field synergistic method according to claim 6 x The method for using Pd heterojunction materials is characterized by... The palladium base is provided in powder form, and its mass-to-volume ratio with the ethanol is 1~10 mg:1 mL.

8. The novel PdO prepared by electron beam induction and thermal field synergistic method according to claim 6 x The method for using Pd heterojunction materials is characterized by... The drying temperature is 60~90℃, and the time is 8~12h.

9. The novel PdO prepared by the method according to any one of claims 1 to 8 x / Pd heterojunction material or novel PdO prepared by the method according to any one of claims 1 to 8 x Composite materials of Pd heterojunction materials.

10. The novel PdO prepared by the method according to any one of claims 1 to 8 x Applications of Pd heterojunction materials in the preparation of catalysts, gas sensors, hydrogen storage materials and anti-corrosion coatings.

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