A hafnium zirconium oxide nanowire, a nano hafnium zirconium oxide powder, a preparation method and application thereof

Abstract

The application provides a hafnium zirconium oxide nanowire, a nanometer hafnium zirconium oxide powder, a preparation method and application thereof, and belongs to the technical field of material synthesis and catalysis. x Zr 1‑x O2,x ranges from 0.1 to 0.9; the hafnium zirconium oxide nanowire is sub-nanometer size (diameter less than 1 nanometer), has the polymer-like flexibility of easy bending and curling, and has superior ferroelectricity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of synthesis and catalysis technology, and particularly relates to a hafnium-zirconium oxide nanowire, a nanometer hafnium-zirconium oxide powder and a preparation method and application thereof. BACKGROUND

[0002] Piezocatalysis is a kind of catalysis mode of converting mechanical energy into chemical energy, which can use renewable friction, water waves, noise and other mechanical vibrations to make piezoelectric materials produce piezoelectric potential to drive charge transfer of reaction substrates to produce redox reactions. The ferroelectric body with broken symmetry has spontaneous polarization, and the polarization direction and size can be changed by external field (electric field, force field, etc.), which produces high piezoelectric potential and is commonly used as a piezocatalyst.

[0003] At present, the most widely studied is to prepare a nanometer ferroelectric body with high electromechanical conversion coefficient by regulating structure, composition and morphology, and to induce high piezoelectric potential under mechanical field, so as to increase the electron transfer rate from the thermodynamic point of view and improve the catalytic performance.

[0004] It is found that if the ferroelectric body has super flexibility, it will have a sensitive response to external mechanical force, and when it is used as a catalyst, it can achieve high activity. Based on the analysis of sub-nanometer inorganic materials, if the ferroelectric body is made into a nanowire with a diameter of less than 1 nm, the above expectation will be realized. However, the commonly used piezocatalyst is a ferroelectric body with perovskite ABO3 structure, and its size effect (ferroelectricity will weaken or even disappear with the decrease of size) limits its high piezocatalytic activity.

[0005] Hafnium-based ferroelectric body has attracted much attention because its ferroelectricity increases with the decrease of size, but these hafnium-based ferroelectric bodies with ferroelectricity are found in thin films and cannot be used as catalysts, and there is no hafnium-zirconium oxide nanowire and powder formed at present stage. SUMMARY

[0006] Therefore, the technical problem to be solved by the present application is to overcome the defect that there is no hafnium-zirconium oxide nanowire with ferroelectricity in the prior art, so as to provide a hafnium-zirconium oxide nanowire.

[0007] The present application also provides a nanometer hafnium-zirconium oxide powder.

[0008] The present application also provides a preparation method of the nanometer hafnium-zirconium oxide powder.

[0009] The present application also provides an application of the nanometer hafnium-zirconium oxide powder.

[0010] To solve the above technical problems, the present application provides a hafnium-zirconium oxide nanowire, which has a chemical formula of HfxZr 1-x O2,x is in the range of 0.1-0.9.

[0011] As a preferred solution, the x is 0.5.

[0012] As a preferred solution, the diameter of the hafnium zirconium oxide nanowire is less than 1 nm.

[0013] The application further provides a nanometer hafnium zirconium oxide powder.

[0014] The application further provides a preparation method of the nanometer hafnium zirconium oxide powder, comprising the following steps: mixing a hafnium source, a zirconium source, a mineralizer, a surfactant and a solvent in an inert environment, degassing, then heating to react, adding a precipitant after the reaction is completed, and separating to obtain the nanometer hafnium zirconium oxide powder.

[0015] As a preferred solution, the mineralizer is one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide; the molar ratio of the mineralizer to the total molar quantity of the zirconium source and the hafnium source is 1:1.5-2.5, the surfactant is oleic acid and / or oleylamine, the solvent is at least one of octadecene, octane and benzyl ether, and the volume ratio of the surfactant to the solvent is 1:1.5-2.

[0016] As a preferred solution, the hafnium source is hafnium acetylacetonate, and the zirconium source is zirconium acetylacetonate.

[0017] As a preferred solution, the degassing is performed at 80-120 DEG C, and the degassing time is 20-40 minutes.

[0018] As a preferred solution, the heating is performed at a constant rate, the rate is 3-8 DEG C / min, the heating is performed to 280-320 DEG C to react, and the reaction time is 2-4 hours.

[0019] As a preferred solution, the precipitant is methanol, ethanol or acetone.

[0020] The application further provides an application of the nanometer hafnium zirconium oxide powder in the piezocatalytic decomposition of water to produce hydrogen.

[0021] As a preferred solution, the nanometer hafnium zirconium oxide powder is put into a reaction container containing a reaction solution, and then the reaction container is shaken or the reaction solution is stirred to decompose water to produce hydrogen.

[0022] The technical solution of the application has the following advantages:

[0023] The present application first synthesizes hafnium zirconium oxide nanowires, which have good ferroelectricity, and the polarization direction of which is easily reversed by external field (electric field or force field). The nanometer hafnium zirconium oxide powder containing the hafnium zirconium oxide nanowires is very suitable as a piezoelectric catalyst, and has good catalytic effect in the field of hydrogen production by water decomposition. Further, sub-nanometer size (diameter less than 1 nanometer) hafnium zirconium oxide nanowires are also synthesized, which have a high molecular-like flexibility of easy bending and curling when reaching sub-nanometer size. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0025] Figure 1 X-ray diffraction (XRD) pattern of the nanometer hafnium zirconium oxide powder prepared for Example 1-Example 5.

[0026] Figure 2 Low-power transmission electron microscopy (TEM) of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0027] Figure 3 Negative spherical aberration correction electron microscopy of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0028] Figure 4 Oxygen k-edge x-ray absorption spectroscopy (XAS) of the hafnium zirconium oxide nanowires of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0029] Figure 5 X-ray photoelectron spectroscopy (XPS) of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0030] Figure 6 Transmission electron microscopy stress distribution of a single sub-nanowire of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0031] Figure 7 Phase inversion hysteresis loop and piezoelectric force response curve of the hafnium zirconium oxide nanowires of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0032] Figure 8 First-principles calculation diagram of force-induced polarization reversal of the nanometer hafnium zirconium oxide powder prepared for Example 3.

[0033] Figure 9 Picture of the nanometer hafnium zirconium oxide powder prepared for Example 3 being volatilized into a gel.

[0034] Figure 10a A first transmission electron microscope (TEM) image of the sample of the nano hafnium zirconium oxide particles prepared for Comparative Example 1.

[0035] Figure 10b A second transmission electron microscope (TEM) image of the sample of the nano hafnium zirconium oxide particles prepared for Comparative Example 1.

[0036] Figure 10c An X-ray diffraction (XRD) pattern of the sample of the nano hafnium zirconium oxide particles prepared for Comparative Example 1.

[0037] Figure 11a A first transmission electron microscope (TEM) image of the sample of the nano hafnium zirconium oxide particles prepared for Comparative Example 2.

[0038] Figure 11b A second transmission electron microscope (TEM) image of the sample of the nano hafnium zirconium oxide particles prepared for Comparative Example 2.

[0039] Figure 11c An X-ray diffraction (XRD) pattern of the sample of the nano hafnium zirconium oxide particles prepared for Comparative Example 2.

[0040] Figure 12 A schematic diagram of the amount of hydrogen produced by piezocatalytic decomposition of water under stirring for the nano hafnium zirconium oxide powder prepared for Example 3.

[0041] Figure 13 A schematic diagram of the amount of hydrogen produced by piezocatalytic decomposition of water under ultrasonic vibration for the nano hafnium zirconium oxide powder prepared for Example 3. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0043] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0044] In the description of the present application, it is to be noted that the terms "mounting", "connection", "connecting" should be understood in a broad sense unless otherwise clearly specified and limited, for example, they can mean fixed connection, or detachable connection, or integral connection; they can mean mechanical connection, or electrical connection; they can mean direct connection, or indirect connection via an intermediate medium; they can mean the communication inside two elements. The specific meanings of the above terms in the present application can be understood according to the specific circumstances for those skilled in the art.

[0045] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0046] Example 1

[0047] In a glove box filled with helium, 0.1 mmol hafnium acetylacetonate, 0.9 mmol zirconium acetylacetonate, and 2.5 mmol lithium hydroxide were mixed uniformly and added to a mixture of 5 ml of oleic acid and 7.5 ml of octyl ether in a 50 ml three-necked flask to obtain a reaction mixture;

[0048] The reaction mixture was degassed at 120℃ for 20 min in a glove box filled with helium, and then heated to 320℃ at a constant rate of 8℃ / min, and kept for 2 hours to obtain an emulsion containing hafnium zirconium oxide nanowires;

[0049] After the emulsion containing hafnium zirconium oxide nanowires was cooled to room temperature, it was taken out of the glove box, and ethanol was added to the emulsion. After centrifugal separation, a hafnium zirconium oxide nanowire powder was obtained. The chemical formula of the hafnium zirconium oxide nanowire is Hf 0.1 Zr 0.9 O2.

[0050] Example 2

[0051] In an argon-filled glove box, 0.2 mmol hafnium acetylacetonate, 0.8 mmol zirconium acetylacetonate, and 1.5 mmol potassium hydroxide were mixed uniformly and added to a mixture containing 1 ml of oleic acid, 5 ml of oleylamine, and 12 ml of octane solvent in a 50 ml three-necked flask to obtain a reaction mixture;

[0052] The reaction mixture was degassed at 80℃ for 40 min in an argon-filled glove box, and then heated to 280℃ at a constant rate of 3℃ / min, and kept for 4 hours to obtain an emulsion containing hafnium zirconium oxide nanowires;

[0053] After the emulsion containing hafnium zirconium oxide nanowires is cooled to room temperature, the emulsion is taken out of the glove box, methanol is added to the emulsion, and after centrifugal separation, a nanometer hafnium zirconium oxide powder is obtained, and the chemical formula of the hafnium zirconium oxide nanowires is Hf 0.2 Zr 0.8 O2.

[0054] Example 3

[0055] In an argon-filled glove box, 0.5 mmol of hafnium acetylacetonate, 0.5 mmol of zirconium acetylacetonate, and 2 mmol of sodium hydroxide are uniformly mixed and added to a mixed solution containing 1 ml of oleic acid, 4.5 ml of oleylamine, and 10 ml of octadecene, and the mixture is uniformly mixed in a 50 ml three-necked flask to obtain a reaction mixture;

[0056] The reaction mixture is degassed at 100°C for 30 min in an argon-filled glove box, and after degassing is completed, the reaction mixture is heated to 300°C at a constant rate of 5°C / min and maintained for 3 hours to obtain an emulsion containing hafnium zirconium oxide nanowires;

[0057] After the emulsion containing hafnium zirconium oxide nanowires is cooled to room temperature, the emulsion is taken out of the glove box, methanol is added to the emulsion, and after centrifugal separation, a nanometer hafnium zirconium oxide powder is obtained, and the chemical formula of the hafnium zirconium oxide nanowires is Hf 0.5 Zr 0.5 O2.

[0058] Example 4

[0059] In an argon-filled glove box, 0.8 mmol of hafnium acetylacetonate, 0.2 mmol of zirconium acetylacetonate, and 2.5 mmol of sodium hydroxide are uniformly mixed and added to a mixed solution containing 6 ml of oleylamine and 12 ml of octadecene solvent, and the mixture is uniformly mixed in a 50 ml three-necked flask to obtain a reaction mixture;

[0060] The reaction mixture is degassed at 120°C for 30 min in an argon-filled glove box, and after degassing is completed, the reaction mixture is heated to 310°C at a constant rate of 6°C / min and maintained for 2.5 hours to obtain an emulsion containing hafnium zirconium oxide nanowires;

[0061] After the emulsion containing hafnium zirconium oxide nanowires is cooled to room temperature, the emulsion is taken out of the glove box, methanol is added to the emulsion, and after centrifugal separation, a nanometer hafnium zirconium oxide powder is obtained, and the chemical formula of the hafnium zirconium oxide nanowires is Hf 0.8 Zr 0.2 O2.

[0062] Example 5

[0063] In a glove box filled with helium, 0.9 mmol hafnium acetylacetonate, 0.1 mmol zirconium acetylacetonate, 2 mmol potassium hydroxide were mixed uniformly, and then added into a mixed solution containing 6 ml of oleic acid and 11 ml of octane solvent, and mixed uniformly in a 50 ml three-necked flask to obtain a reaction mixture;

[0064] The reaction mixture was degassed at 90°C for 25 min in a glove box filled with helium, and then heated to 300°C at a constant rate of 7°C / min, and kept for 2.5 hours to obtain an emulsion containing hafnium zirconium oxide nanowires;

[0065] After the emulsion containing hafnium zirconium oxide nanowires was cooled to room temperature, it was taken out of the glove box, and methanol was added to the emulsion. After centrifugal separation, a hafnium zirconium oxide nanowire powder was obtained. The chemical formula of the hafnium zirconium oxide nanowire is Hf 0.9 Zr 0.1 O2.

[0066] Comparative Example 1

[0067] In a glove box filled with helium, 0.9 mmol hafnium acetylacetonate, 0.1 mmol zirconium acetylacetonate, 2 mmol potassium hydroxide were mixed uniformly, and then added into a mixed solution containing 6 ml of oleic acid and 11 ml of octane solvent, and mixed uniformly in a 50 ml three-necked flask to obtain a reaction mixture;

[0068] The reaction mixture was degassed at 90°C for 25 min in a glove box filled with helium, and then heated to 300°C at a constant rate of 7°C / min, and kept for 0.5 hours to obtain hafnium zirconium oxide nanometer quantum dots of 1-2 nm, and the hafnium zirconium oxide nanometer quantum dots of this size were in tetragonal phase (t phase).

[0069] Comparative Example 2

[0070] Hafnium zirconium oxide was prepared by a hydrothermal method, and the specific steps were as follows:

[0071] 0.05 g of HfCl4 and 0.0364 g of ZrCl4 were mixed in 22.5 mL of benzyl alcohol, and sealed in a stainless steel autoclave with a polytetrafluoroethylene inner liner. The stainless steel autoclave with a polytetrafluoroethylene inner liner was heated at 220°C for 48 h. After the reaction, the reaction kettle was cooled to room temperature, and the product was collected by centrifugation with ethanol, and then dispersed with ethanol, and washed twice with n-hexane as a poor solvent, and the precipitate was dried to obtain a hafnium zirconium oxide powder of 3-5 nm, and the molecular formula was Hf 0.5 Zr 0.5 O2, and the hafnium zirconium oxide nanoparticles of this size were in orthorhombic phase (m phase).

[0072] Figure 1 X-ray diffraction (XRD) patterns, the abscissa is the scanning angle (2θ), the ordinate is the diffraction peak intensity, the patterns in the figure are the nanometer hafnium zirconium oxide powder prepared in Example 1-Example 5 from bottom to top; all the diffraction peaks can be scaled according to Pca21 (o phase), the peaks at 2θ = 30.4°, 50.1°, 50.7°, 59.1° and 60.1° can correspond to the (011), (112), (020), (013) and (121) faces of the tetragonal P42 / nmc phase (o phase) of the hafnium zirconium oxide nanoparticles one by one, and the new peak at 2θ = 23° of the hafnium zirconium oxide nanowire prepared in the scheme is the typical characteristic (110) peak of the orthorhombic Pca21 (o phase). This orthorhombic phase (Pca21, o phase) has non-central symmetry, and dipole appears in the crystal, that is, ferroelectricity appears, so the XRD analysis shows that the hafnium zirconium oxide nanowire has the orthorhombic phase with ferroelectricity. And the XRD of hafnium zirconium doped in different proportions is Pca21 (o phase) structure with ferroelectricity.

[0073] Table 1 is an inductively coupled plasma emission spectrum (ICP-AES), which tests the element ratio of hafnium and zirconium in the hafnium zirconium oxide nanowire doped in different proportions, and the element mass ratio obtained is consistent with the ratio of hafnium and zirconium in the chemical formula.

[0074] Table 1

[0075]

[0076] Figure 2 The low-magnification transmission electron microscopy (TEM) image is the nanometer hafnium zirconium oxide powder prepared in Example 3 as the sample for detection, from the figure it can be seen that the nanometer hafnium zirconium oxide powder presents a random curly shape, the average diameter is less than 1 nm, and the size distribution is uniform. From the transmission electron microscopy (TEM) photograph, it can be seen that the curling of the sub-nanometer wire is similar to the random curling of the polymer, which indirectly indicates that the nanometer hafnium zirconium oxide powder has the characteristics of the polymer.

[0077] Figure 3 The negative spherical aberration correction electron microscopy (TEM) image is the nanometer hafnium zirconium oxide powder prepared in Example 3 as the sample for detection, the ferroelectricity of the orthorhombic hafnium zirconium oxide is derived from the distribution of oxygen atoms in the crystal, in order to further more accurately confirm that the hafnium zirconium oxide is the orthorhombic phase with ferroelectricity, the negative spherical aberration correction transmission electron microscopy (TEM) more sensitive to oxygen atoms is used to detect the positions of hafnium / zirconium atoms and oxygen atoms. Along the

[010] projection, the arrangement of oxygen atoms (gray) related to hafnium / zirconium (white) is very consistent with the simulation model using the o orthorhombic Pca21 phase structure. According to the asymmetric arrangement of oxygen sites around the Hf / Zr column marked by the pink rectangle in the TEM image and the simulation model, it is directly confirmed that the nanometer hafnium zirconium oxide powder is the o phase ferroelectric body.

[0078] Figure 4 For the oxygen k-edge x-ray absorption spectroscopy (XAS) of the hafnium zirconium oxide nanowires, the figure is detected by taking the nanometer hafnium zirconium oxide powder prepared in Example 3 as a sample, and the oxygen k-edge x-ray absorption spectroscopy (XAS) is further used to clarify that the hafnium zirconium oxide nanowires have the o-phase structure with ferroelectricity. The XAS spectrum can measure the structure symmetry information provided by the crystal field splitting, and then judge whether the nanometer hafnium zirconium oxide is the symmetry breaking structure with ferroelectricity. First, there is a t2-e split (t2: dxy, dxz, dyz; e: dz2, dx2-y2) in the spectrum, which is Δt typical of the hafnium zirconium oxide garnet structure. In addition, a secondary crystal field splitting appears in the spectrum, which is caused by the polar rhombohedral distortion (Δr). The polar o-phase distortion makes the degenerate e orbital split to cause the structure symmetry breaking, which more clearly indicates that the hafnium zirconium oxide nanowires prepared by the scheme have ferroelectricity.

[0079] Figure 5 For the X-ray photoelectron spectroscopy (XPS) figure, the figure is detected by taking the nanometer hafnium zirconium oxide powder prepared in Example 3 as a sample, and it can be seen from the figure that the hafnium zirconium oxide nanowires contain hafnium 4f peaks and zirconium 3d peaks respectively, which confirms that the two substances successfully form a solid solution.

[0080] Figure 6 For the single sub-nanowire transmission electron microscope stress distribution figure, the figure is detected by taking the nanometer hafnium zirconium oxide powder prepared in Example 3 as a sample, and the local strain is drawn by using high-resolution HAADF-STEM, and the strain distribution is extracted from a single hafnium zirconium oxide nanowire in the TEM image. In geometric phase analysis (GPA), a large number of distorted structures can be observed. The maximum difference of the lattice spacing of a single hafnium zirconium oxide nanowire can reach 26%. In addition, the in-plane lattice is obviously stretched, and the out-of-plane lattice is compressed. Therefore, the huge local strain can make the crystal structure change from the non-polar tetragonal phase to the polar orthorhombic phase. It is directly proved that the nanowire has a large internal stress, and the internal stress is the source of inducing the ferroelectric phase.

[0081] Figure 7 For the phase inversion hysteresis loop and piezoelectric force response curve of the hafnium zirconium oxide nanowires, the figure is detected by taking the nanometer hafnium zirconium oxide powder prepared in Example 3 as a sample, and the piezoelectric force microscope is the most direct way to test the ferroelectricity of the nanometer ferroelectric. In the test process of the hafnium zirconium oxide nanowires, when the probe of the piezoelectric force microscope acts on the sample under the electric field, the polarization of the hafnium zirconium oxide nanowires with ferroelectricity begins to reverse, the amplitude measured by the probe changes, and a characteristic "butterfly" curve is displayed, while the piezoelectric force microscope phase signal shows a 180° phase inversion at the coercive field (±2V), which is derived from the 180° inversion of the polarization of the hafnium zirconium oxide, which proves that the hafnium zirconium oxide nanowires have good ferroelectric response.

[0082] Figure 8 Fig. 14 is a graph of first principle calculation of stress-induced polarization reversal, which is detected by taking the nano hafnium zirconium oxide powder prepared in Example 3 as sample, in the process, a model of o-phase hafnium zirconium oxide with upward polarization is first constructed (step 1), after energy relaxation, the polarization direction is reversed downward (step 2), after 0.02 MPa stress is applied, the polarization is reversed again (step 3), and after energy relaxation and stabilization, the polarization is finally reversed from downward to upward (step 4). This theoretical calculation proves that the polarization of the nano hafnium zirconium oxide nanowire can be reversed by stress.

[0083] Figure 9 Fig. 15 is a picture of the gelation of nano hafnium zirconium oxide powder, taking the nano hafnium zirconium oxide powder prepared in Example 3 as sample, the nano hafnium zirconium oxide powder is dispersed in a non-polar solvent for a period of time to form a transparent gel. It is well known that flexible polymers are dispersed in solvents at a certain solubility, when the solvent is volatilized, the polymer forms a network structure to chelate solvent molecules to form a hydrogel, this phenomenon is usually not seen in inorganic nano powder solutions, but the inorganic hafnium zirconium oxide nanowire in the present application has a gelation property similar to that of a high polymer, indicating that the solution formed by the sample has super flexibility similar to that of a polymer. This flexibility is derived from the sudden increase in atomic rotation freedom at the sub-nanometer scale, which breaks through the plastic deformation limit of traditional inorganic oxide crystals.

[0084] Figs. 10(a) and 10(b) are transmission electron microscope images, and Fig. 10(c) is an X-ray diffraction (XRD) spectrum, taking the nano hafnium zirconium oxide particles prepared in Comparative Example 1 as sample, it can be seen from Figs. 10(a) and 10(b) that the nano particles obtained in Comparative Example 1 are uniform in size, with a size of about 1-2 nm. It can also be seen from Fig. 10(c) that no impurity phase is generated in the hafnium zirconium oxide nanoparticles, and hafnium oxide and zirconium oxide are successfully doped, confirming that the crystal phase is t-phase.

[0085] Figs. 11(a) and 11(b) are transmission electron microscope images, and Fig. 11(c) is an X-ray diffraction (XRD) spectrum, taking the nano hafnium zirconium oxide particles prepared in Comparative Example 2 as sample, it can be seen from Figs. 11(a) and 10(b) that the prepared nano particles are uniform in size and uniform in dispersion, the nano particles are small, with a size of about 3-5 nm. Under high magnification transmission electron microscope, clear crystal lattice fringes can be seen, indicating that it also has good crystallinity. It can also be seen from Fig. 11(c) that the hafnium zirconium oxide nanoparticles have good crystallinity, no impurity phase is generated, and hafnium oxide and zirconium oxide are successfully doped, confirming that the crystal phase is antiferroelectric m-phase.

[0086] Experimental Example 1

[0087] The zirconium hafnium oxide nanometer powder prepared in the manner of the Example 3 was dispersed in a mixed solution of 20 ml pure water and 10 ml triethanolamine, sealed and argon was introduced, the solution was stirred by a magnetic stirrer, the temperature of the piezoelectric catalysis system was controlled at 20°C by a circulating cooling system, the generated gas was periodically and quantitatively extracted and determined by gas chromatography, and the cycle test was carried out. The piezoelectric catalysis water decomposition hydrogen production amount is shown in Fig. 2. As shown in the figure, the zirconium hafnium oxide nanometer powder prepared in the present scheme has the activity of water decomposition hydrogen production by only stirring the reaction solution. Figure 12

[0088] Experimental Example 2

[0089] The zirconium hafnium oxide nanometer powder prepared in the manner of the Example 3 was dispersed in a mixed solution of 20 ml pure water and 10 ml triethanolamine, sealed and argon was introduced, the solution was stirred by a magnetic stirrer, the temperature of the piezoelectric catalysis system was controlled at 20°C by a circulating cooling system, the generated gas was periodically and quantitatively extracted and determined by gas chromatography, and the cycle test was carried out. The piezoelectric catalysis water decomposition hydrogen production amount is shown in Fig. 2. As shown in the figure, the zirconium hafnium oxide nanometer powder prepared in the present scheme has the activity of water decomposition hydrogen production by only stirring the reaction solution. Figure 13

[0090] In summary, the sub-nanometer zirconium hafnium oxide (Hf 0.5 Zr 0.5 O2) nanowire synthesized in the present patent has the high molecular-like flexibility, and it is proved to be the Pca21 phase with ferroelectricity. By means of molecular dynamics and DFT simulation, it is proved that the polarization reversal of the sub-nanometer ferroelectric can occur, and the dynamic regulation of the reactant adsorption energy and the product desorption energy can be realized. At the same time, the sub-nanometer Hf 0.5 Zr 0.5 O2 nanowire realizes the high piezoelectric catalysis water decomposition hydrogen production performance, up to 25687 μmol g -1 h -1 . In addition, only slight stirring can promote the sub-nanometer Hf 0.5 Zr 0.5 O2 to decompose water to produce hydrogen.

[0091] Obviously, the above examples are only examples for clearly illustrating, but not limitation of the embodiments. Other different forms of changes or variations can be made on the basis of the above description for those skilled in the art. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.​​

Claims

1. A hafnium zirconium oxide nanowire, characterized by, Hf x Zr 1-x O2, x ranges from 0.1 to 0.9, and the hafnium zirconium oxide nanowire has a diameter of less than 1 nm.

2. The hafnium zirconium oxide nanowire of claim 1, wherein, The x is 0.

5.

3. A nano hafnium zirconium oxide powder, characterized by, The hafnium zirconium oxide nanowire of any one of claims 1-2.

4. A method for preparing nano-hafnium zirconium oxide powder as described in claim 3, characterized in that, The method comprises the following steps: mixing a hafnium source, a zirconium source, a mineralizer, a surfactant and a solvent in an inert environment, degassing, then heating to react, adding a precipitant after the reaction is completed, and separating to obtain the hafnium zirconium oxide nanowire powder; The mineralizer is one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide; the molar ratio of the mineralizer to the total moles of the zirconium source and the hafnium source is 1-2.5:2.5-1, the hafnium source is calculated by the element of hafnium, and the zirconium source is calculated by the element of zirconium; The surfactant is oleic acid and / or oleylamine, and the solvent is at least one of octadecene, octane and benzyl ether; the volume ratio of the surfactant to the solvent is 1:1.5-2; The hafnium source is hafnium acetylacetone, and the zirconium source is zirconium acetylacetone; the precipitant is methanol, ethanol or acetone; The degassing is performed at 80-120℃ for 20-40 minutes; The heating is performed at a constant rate of 3-8℃ / min, and the reaction is performed at 280-320℃ for 2-4 hours.

5. The application of the hafnium zirconium oxide nanowire powder of claim 3 in piezocatalytic decomposition of water to produce hydrogen.

6. The use of the nano-hafnium zirconium oxide powder according to claim 5 in the piezocatalytic decomposition of water to produce hydrogen, characterized in that, The nanometer hafnium zirconium oxide powder is put into a reaction container containing a reaction solution, and the reaction container is shaken or the reaction solution is stirred to decompose water to produce hydrogen.

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