阅读说明：本技术 一种电化学还原辅助制备超薄氧化锌纳米片的方法 (Method for preparing ultrathin zinc oxide nanosheet with assistance of electrochemical reduction ) 是由 张利利 路盼盼 肖晨辰 于 2021-08-24 设计创作，主要内容包括：本发明涉及一种电化学还原辅助制备超薄氧化锌纳米片的方法,属于纳米材料制备领域。本发明以导电材料为基底,通过恒电流沉积得到氧化锌纳米棒阵列；再利用电化学方法还原氧化锌纳米棒阵列,得到单质锌复合的氧化锌纳米棒阵列；最后在超纯水中静置,锌纳米粒子与水反应生成超薄氧化锌纳米片。本发明采用的方法绿色高效、简便温和、可规模化生产。所制备的超薄氧化锌纳米片在气体传感器、光催化领域具有较好的应用前景。(The invention relates to a method for preparing an ultrathin zinc oxide nano-sheet by electrochemical reduction assistance, belonging to the field of nano-material preparation. The invention takes a conductive material as a substrate, and obtains a zinc oxide nanorod array by constant current deposition; reducing the zinc oxide nanorod array by an electrochemical method to obtain a zinc oxide nanorod array compounded by simple substance zinc; and finally, standing in ultrapure water, and reacting the zinc nanoparticles with water to generate the ultrathin zinc oxide nanosheets. The method adopted by the invention is green, efficient, simple, convenient and mild, and can be used for large-scale production. The prepared ultrathin zinc oxide nano-sheet has better application prospect in the fields of gas sensors and photocatalysis.)

1. A method for preparing an ultrathin zinc oxide nano-sheet by electrochemical reduction assistance is characterized by comprising the following steps:

(1) immersing the polished titanium sheet in a mixed aqueous solution of zinc nitrate and ammonium nitrate, performing constant-current electrodeposition in a double-electrode electrolytic cell at 70-90 ℃ with a graphite electrode as a counter electrode to obtain a zinc oxide nanorod array vertically growing on a conductive substrate;

(2) placing the zinc oxide nanorod array obtained in the step (1) in a conductive salt solution, adjusting the pH to 2-8, and performing electrochemical reduction at room temperature to obtain a simple substance zinc composite zinc oxide nanorod array;

(3) and (3) placing the simple substance zinc composite zinc oxide nanorod array obtained in the step (2) into ultrapure water, and reacting zinc nanoparticles with water to obtain the ultrathin zinc oxide nanosheet.

2. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: the concentration of zinc nitrate in the mixed water solution in the step (1) is 0.01-0.5M, and the concentration of ammonium nitrate is 0.01-1M.

3. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: the conductive substrate used in the step (1) comprises a titanium sheet, a copper sheet, a nickel net, a copper net, carbon cloth, carbon paper or conductive glass.

4. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: the current of the constant current electrodeposition in the step (1) is-0.5 mA/cm² ~-5 mA/cm²The electrodeposition time is 30-180 min.

5. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: the conductive salt solution is extracted in the step (2)Using KCl, KBr, KI, KF, NH₄Cl、NH₄F、K₂SO₄、K₂S₂O₈、K₂CO₃Or KNO₃An aqueous solution of (a).

6. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: the concentration of the conductive salt solution in the step (2) is 1 mM-100 mM.

7. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: the current of the electrodeposition in the step (2) is-0.1 mA/cm² ~ -10 mA/cm²The electrodeposition time is 10-300 min.

8. The method for preparing the ultrathin zinc oxide nano-sheet by the electrochemical reduction assistance of claim 1, which is characterized in that: and (3) the reaction time of the zinc nanoparticles and water in the step (3) is 0.5-20 h.

9. An ultra-thin zinc oxide nanoplatelet prepared by the method of any of claims 1-8.

Technical Field

The invention belongs to the field of nano material preparation, and particularly relates to a preparation method of an ultrathin zinc oxide nano sheet.

Background

Zinc oxide (ZnO), a direct band gap semiconductor material, has the characteristics of high electron mobility, good chemical/physical stability, no toxicity, rich content, low price and the like, and can be widely applied to the fields of gas sensors, photocatalysis, light emitting diodes and the like. Zinc oxide can be constructed into various nanostructures (Nanoscale Research Letters, 2016, 11, 175), such as nanorods, nanowires, nanotubes, nanobelts, nanofibers, nanospheres, nanosheets, and the like.

The two-dimensional nano-sheet has larger specific surface area, can expose more active sites, is an ideal nano-material shape, and can be better applied to various fields by preparing the ultrathin zinc oxide nano-sheet. The two-dimensional zinc oxide Nano-sheet has reduced response and recovery time due to the increase of the proportion of the exposed active plane, and has good gas sensing performance (Nano-Micro Lett., 2015, 7, 97-120). The two-dimensional zinc oxide nanosheet can shorten the migration path of a photogenerated carrier and realize rapid transportation, and is considered to be an effective way for improving the photocatalytic performance (RSC adv, 2016, 6, 78846-78851). The method for preparing the two-dimensional zinc oxide nanoplatelets includes a hydrothermal method (ACS Applied. Mater. Interfaces, 2019, 11, 24757-. These synthesis methods often require harsh conditions such as high temperature, high pressure, organic reagent treatment, etc., belong to energy-intensive production processes, and are not conducive to ecological environment protection. Therefore, it is necessary to find a method for preparing the ultrathin zinc oxide nano-sheet, which is environment-friendly, mild in condition and simple in operation.

Disclosure of Invention

Aiming at the problems of the existing method for preparing the zinc oxide nano-sheet, the invention provides a method for preparing the ultrathin zinc oxide nano-sheet by electrochemical reduction assistance. The invention provides a renewable energy driven electrochemical reduction method for preparing zinc oxide nano-sheets, which has the characteristics of greenness, high efficiency, simplicity, convenience, mildness, strong operability and planned production.

In order to solve the technical problems, the invention adopts the following technical scheme:

the invention provides a method for preparing an ultrathin zinc oxide nano-sheet by electrochemical reduction assistance, which comprises the following steps:

(1) immersing the polished titanium sheet in a mixed aqueous solution of zinc nitrate and ammonium nitrate, and carrying out constant-current electrodeposition at 70-90 ℃ to obtain a zinc oxide nanorod array growing on a titanium sheet substrate;

(2) immersing the zinc oxide nanorod array obtained in the step (1) in a conductive salt solution, adjusting the pH to 2-8, and performing constant-current electrodeposition at room temperature to obtain a zinc oxide nanorod array compounded by simple substance zinc;

(3) and (3) placing the simple substance zinc composite zinc oxide nanorod array obtained in the step (2) into ultrapure water, and reacting the simple substance zinc nanoparticles with the water to generate the ultrathin zinc oxide nanosheet.

Further, the concentration of zinc nitrate in the mixed aqueous solution in the step (1) is 0.01-0.5M, preferably 0.01M, and the concentration of ammonium nitrate is 0.01-1M, preferably 0.05M.

Further, the current of the constant current electrodeposition in the step (1) is-0.5 mA/cm²~-5mA/cm²Preferably-1 mA/cm²The electrodeposition time is 30-180 min, preferably 90 min, and the ZnO nanorod prepared under the conditions is hexagonal prism in shape. The ZnO nano-rod is in a conical shape when the electrodeposition time is too short or the current is too small.

Further, the conductive substrate used in the step (1) comprises a titanium sheet, a copper sheet, a nickel net, a copper net, carbon cloth, carbon paper or conductive glass.

Further, the conductive salt solution in the step (2) adopts KCl, KBr, KI, KF and NH₄Cl、NH₄F、K₂SO₄、K₂S₂O₈、K₂CO₃Or KNO₃An aqueous solution of (a).

Further, the concentration of the conductive salt solution in the step (2) is 1 mM-100 mM.

Further, the electric current of the electrodeposition in the step (2) is-0.1 mA/cm² ~ -10 mA/cm²The electrodeposition time is 10-300 min.

Further, the reaction time of the zinc nanoparticles and water in the step (3) is 0.5-20 h.

The invention also provides the ultrathin zinc oxide nano-sheet prepared by the method.

The invention has the beneficial effects that: in the synthesis process, the zinc oxide nanorod array is prepared by adopting constant current electrodeposition, and the nanorod arrays with different sizes and appearances are obtained by regulating and controlling the deposition temperature and the deposition time; reducing a part of zinc oxide into simple substance zinc nano particles by utilizing an electrochemical reduction technology, and regulating the reduction amount of the simple substance zinc nano particles by regulating and controlling the current, the deposition time, the pH value of electrolyte and the type of the electrolyte so as to obtain zinc oxide nano rod arrays compounded by simple substance zinc with different amounts; the simple substance zinc nano particles react with water to generate the ultrathin zinc oxide nano sheet. The zinc oxide is reduced into simple substance zinc by adopting an electrochemical reduction technology, the solution is kept stand in ultrapure water, and the ultrathin zinc oxide nanosheet is generated through the reaction of simple substance zinc nanoparticles and water. In terms of the process, the preparation method is green, mild, simple, efficient, good in repeatability, low in equipment requirement and easy to realize industrial production.

Drawings

FIG. 1 is a scanning electron microscope image of the zinc oxide nanorod array prepared in example 1 and a zinc oxide nanorod array composited with elemental zinc (a-zinc oxide nanorod array, b-zinc oxide nanorod array composited with elemental zinc);

FIG. 2 is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array prepared in example 1 standing in ultrapure water for 0.5 h, 1 h, 2 h, and 5 h;

FIG. 3 is a transmission electron micrograph and a surface scanning result of an X-ray energy spectrum of the ultra-thin zinc oxide nanoplatelets prepared in example 1;

fig. 4 is an atomic force microscope picture and a thickness analysis picture of the ultra-thin zinc oxide nanoplatelets manufactured in example 1;

FIG. 5 is an X-ray diffraction pattern of the material prepared in example 1;

FIG. 6 is a scanning electron microscope image of the zinc oxide nanorod array prepared in example 2;

FIG. 7 is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array prepared in example 3;

FIG. 8 is a scanning electron microscope image of the composite zinc oxide nanorod array of elemental zinc prepared in example 4;

FIG. 9 is a scanning electron microscope image of the composite zinc oxide nanorod array of elemental zinc prepared in example 5;

FIG. 10 is a scanning electron microscope image of the composite zinc oxide nanorod array of elemental zinc prepared in example 6;

FIG. 11 is a scanning electron microscope image of the zinc oxide nanorod array with a surface loaded with potassium chloride prepared in example 7;

fig. 12 is a scanning electron microscope image of the zinc oxide nanorod array with the surface loaded with potassium chloride prepared in example 8.

Detailed Description

The present invention will be further described with reference to the following examples. It is to be understood that the following examples are illustrative only and are not intended to limit the scope of the invention, which is to be given numerous insubstantial modifications and adaptations by those skilled in the art based on the teachings set forth above.

Example 1

In this example, the method for preparing the zinc oxide nanoplatelets by using electrochemical reduction assistance comprises the following steps:

(1) immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) the obtained zinc oxide nanorod array was placed in a 10 mM potassium chloride aqueous solution (pH adjusted to 6) at room temperature using-1 mA/cm²Depositing for 120 min at constant current to obtain a zinc oxide nanorod array compounded with simple substance zinc;

(3) and placing the obtained zinc oxide nanorod array compounded with the simple substance zinc in ultrapure water, standing for 0.5-5 h, and reacting the simple substance zinc nanoparticles with the water to obtain the ultrathin zinc oxide nanosheet.

The scanning electron microscope image of the zinc oxide nanorod array obtained in step (1) of this example is shown in fig. 1a, and it can be seen from the image that the nanorod array has a hexagonal prism shape, a diameter of about 250 and 300 nm, and a length of about 1.5 μm. In the present embodiment, a scanning electron microscope image of the simple substance zinc composite zinc oxide nanorod array obtained in step (2) is shown in fig. 1b, which shows that a large amount of particles are stacked on the surface of the zinc oxide nanorod, indicating that the zinc oxide is successfully reduced to the simple substance zinc.

Scanning electron micrographs of the elemental zinc composite zinc oxide nanorod array standing in ultrapure water for different times are shown in fig. 2, wherein fig. 2a is the scanning electron micrograph of the elemental zinc composite zinc oxide nanorod array prepared in example 1 standing in ultrapure water for 0.5 h; FIG. 2b is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array prepared in example 1 standing in super water for 1 h; FIG. 2c is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array prepared in example 1 standing in super water for 2 hours; FIG. 2d is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array prepared in example 1 standing in super water for 5 hours; it can be observed that the zinc oxide nanorod arrays gradually transform into a sheet structure and are connected with each other with the increase of the soaking time in the ultrapure water, and after 5 hours, the zinc oxide nanorod arrays completely transform into the sheet structure. The simple substance zinc nano particles react with water in the process of standing in ultrapure water, so that an interconnected ultrathin zinc oxide nano sheet structure is formed.

FIG. 3a is a transmission electron microscope image of the ultrathin zinc oxide nanoplate prepared in example 1; FIG. 3b is a high resolution TEM image of the ultrathin ZnO nanosheet prepared in example 1; fig. 3c is the result of surface scanning of the X-ray energy spectrum of the ultra-thin zinc oxide nanoplatelets prepared in example 1.

From the transmission electron micrograph of fig. 3a, it can be seen that the synthesized material is an ultrathin nanosheet structure, and the lattice spacing of the high-magnification transmission electron micrograph of fig. 3b is 0.275 nm and 0.276 nm, which correspond to the (100) crystal plane of ZnO. The surface scanning result of the X-ray energy spectrum is shown in FIG. 3c, and Zn and O elements are uniformly distributed on the nano-chip.

Fig. 4a is an atomic force microscope image of the ultra-thin zinc oxide nanoplatelets prepared in example 1, and fig. 4b is a thickness analysis image of the ultra-thin zinc oxide nanoplatelets prepared in example 1; from the atomic force microscope and thickness analysis chart of fig. 4, it is illustrated that the thickness of the ultra-thin ZnO nanoplates is about 5 nm. The composition of the material is further determined by an XRD (X-ray diffraction) spectrum, as shown in figure 5, the uppermost ZnO nanorod array in the figure corresponds to a diffraction peak of ZnO, the middle ZnO nanorod array compounded by simple substance zinc corresponds to a diffraction peak of ZnO and simple substance Zn, and the condition that a part of ZnO is reduced into simple substance Zn by applying current is shown, and the lowest ultrathin ZnO nanosheet only has the diffraction peak of ZnO and shows that the simple substance zinc completely reacts with water in the standing process in water.

Example 2

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Depositing for 30 min under constant current to obtain zinc oxide nanorod array;

(2) the obtained zinc oxide nanorod array was placed in a 10 mM potassium chloride aqueous solution (pH adjusted to 6) at room temperature using-1 mA/cm²Depositing for 120 min at constant current to obtain a zinc oxide nanorod array compounded with simple substance zinc;

(3) and placing the obtained zinc oxide nanorod array compounded with the simple substance zinc in ultrapure water, standing for 5-10 h, and reacting the simple substance zinc nanoparticles with the water to generate the zinc oxide nanosheet.

The scanning electron microscope image of the zinc oxide nanorod array obtained in the embodiment is shown in fig. 6a, and it can be seen that the prepared zinc oxide nanorod array is conical and is different from zinc oxide with a hexagonal prism shape for 90 min through electrodeposition.

Fig. 6b is a scanning electron microscope image of the zinc oxide nanorod array composited with elemental zinc obtained in this embodiment, which shows that a large number of particles are deposited on the surface of the zinc oxide nanorod, indicating that the zinc oxide is successfully reduced to elemental zinc.

FIG. 6c is a scanning electron microscope image of the composite elemental zinc array obtained in this example after standing in ultrapure water for 5h, wherein the zinc oxide nanorods are partially changed into sheets.

Fig. 6d is a scanning electron microscope image of the elemental zinc composite array obtained in this example standing in ultrapure water for 10h, the zinc oxide nanorods are basically flaky, but the formed nanosheets are thicker and coarser. The zinc oxide nanorods prepared in example 1 have a hexagonal prism shape, and the top thereof is: (101) the crystal face is more flat and smooth. In contrast, the zinc oxide nanorods with the hexagonal pyramid morphology synthesized by the same method in a shorter time have sharp and rough tops and are not beneficial to forming an ultrathin nanosheet structure.

Example 3

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in0.01M zinc nitrate and 0.05M ammonium nitrate in a mixed aqueous solution at 70 ℃ under a pressure of-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) the obtained zinc oxide nanorod array was placed in a 10 mM ammonium chloride aqueous solution (pH adjusted to 6) at room temperature using-1 mA/cm²Depositing for 10 min at constant current to obtain a zinc oxide nanorod array compounded with simple substance zinc;

(3) and placing the obtained zinc oxide nanorod array compounded with the simple substance zinc in ultrapure water, standing for 5-10 h, and reacting the simple substance zinc nanoparticles with the water to generate the ultrathin zinc oxide nanosheet.

The scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array obtained in the embodiment is shown in fig. 7a, a small amount of particles are arranged on the surface of the zinc oxide nanorod, and the amount of the elemental zinc reduced to elemental zinc is small when the electrodeposition time is short.

Fig. 7b is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array obtained in the embodiment standing in ultrapure water for 5 hours, wherein the hexagonal prism surface of the zinc oxide nanorod forms a sheet shape and is connected with adjacent nanorods. When the mixture is kept still for 10 hours, as shown in figure 7c, the zinc oxide nano rods basically and completely form the interconnected ultrathin zinc oxide nano sheets. Indicating that the reaction of elemental zinc nanoparticles with water is a slow process.

Example 4

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) the obtained zinc oxide nanorod array was placed in a 10 mM potassium chloride aqueous solution (pH adjusted to 3) at room temperature using-1 mA/cm²Depositing for 120 min at constant current to obtain a zinc oxide nanorod array compounded with simple substance zinc;

(3) and placing the obtained zinc oxide nanorod array compounded with the simple substance zinc in ultrapure water, standing for 5-10 h, and reacting the simple substance zinc nanoparticles with the water to generate the ultrathin zinc oxide nanosheet.

The scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array obtained in the embodiment is shown in fig. 8a, and a small amount of particles are on the surface of the zinc oxide nanorod. It can be seen that when the pH =3 of the potassium chloride aqueous solution, the resistance of the solution is small, and the voltage is small at a constant current, so the amount of nanoparticles reduced to elemental zinc is small.

Fig. 8b is a scanning electron microscope image of the elemental zinc composite zinc oxide nanorod array obtained in the embodiment standing in ultrapure water for 5 hours, wherein the surface of the zinc oxide nanorod is flaky and connected with adjacent nanorods. When the mixture is kept still for 10 hours, as shown in figure 8c, the zinc oxide nano-rods form the interconnected ultrathin zinc oxide nano-sheets.

Example 5

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) the obtained zinc oxide nanorod array was placed in a 5 mM potassium chloride aqueous solution (pH adjusted to 6) at room temperature using-0.5 mA/cm²Depositing for 60 min at constant current to obtain a zinc oxide nanorod array compounded with simple substance zinc;

(3) and placing the obtained zinc oxide nanorod array compounded with the simple substance zinc in ethanol, and standing for 5 hours.

FIG. 9a is a scanning electron microscope image of the composite zinc oxide nanorod array of elemental zinc prepared in example 5; FIG. 9b is a scanning electron microscope image of the zinc oxide nanorod array compounded with elemental zinc obtained in example 5 standing in ethanol for 5 h.

As shown in the scanning electron microscope image of fig. 9, the zinc oxide nanorod array compounded with the elemental zinc stands in ethanol for 5 hours, the material morphology does not change significantly, the elemental zinc nanoparticles cannot react with water, and a sheet structure cannot be formed.

Example 6

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) will getThe obtained zinc oxide nanorod array was placed in a 5 mM potassium chloride aqueous solution (pH adjusted to 6) at room temperature using-0.5 mA/cm²Depositing for 5 hours under constant current to obtain a zinc oxide nanorod array compounded with simple substance zinc;

as shown in the scanning electron microscope image of fig. 10, when the electrodeposition is performed in the aqueous solution of potassium chloride for 5 hours, the amount of the electrochemically reduced elemental zinc is greatly increased, but the process of the reaction of the elemental zinc and water is not performed, and the ultrathin zinc oxide nanosheet structure cannot be formed. The combination of example 5 and example 6 shows that the ultra-thin zinc oxide nano-sheet can be generated only when the simple substance zinc nano-particles react with water.

Example 7

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) placing the obtained zinc oxide nanorod array above a supersaturated potassium chloride solution, so that potassium chloride nano particles can be recrystallized on the surface of the zinc oxide nanorod to obtain the zinc oxide nanorod array with potassium chloride loaded on the surface;

(3) and placing the obtained zinc oxide nanorod array with the surface loaded with potassium chloride in ultrapure water, and standing for 1-5 hours.

FIG. 11a is a scanning electron microscope image of the zinc oxide nanorod array with a surface loaded with potassium chloride prepared in example 7; FIG. 11b is a scanning electron microscope image of the zinc oxide nanorod array with potassium chloride loaded on the surface, prepared in example 7, standing in ultrapure water for 1 h; FIG. 11c is a scanning electron microscope image of the zinc oxide nanorod array with potassium chloride loaded on the surface, prepared in example 7, standing in ultrapure water for 2 h; fig. 11d is a scanning electron microscope image of the zinc oxide nanorod array with the surface loaded with potassium chloride prepared in example 7 standing in ultrapure water for 5 h.

From the scanning electron micrograph of the zinc oxide nanorod array with potassium chloride loaded on the surface of fig. 11a, it can be seen that the surface of the zinc oxide nanorod array becomes rough. As shown in FIGS. 11b, 11c and 11d, the morphology of the sample was not changed when the sample was left to stand in ultrapure water for 1-5 hours.

Example 8

(1) Immersing the polished titanium sheet of 1.5 cm by 2.5 cm in a mixed aqueous solution of 0.01M zinc nitrate and 0.05M ammonium nitrate at 70 deg.C with-1 mA/cm²Constant current deposition is carried out for 90 min to obtain a zinc oxide nanorod array;

(2) standing the obtained zinc oxide nanorod array in a saturated KCl solution to obtain a zinc oxide nanorod array with potassium chloride loaded on the surface;

(3) and placing the obtained zinc oxide nanorod array with the surface loaded with potassium chloride in ultrapure water, and standing for 1-5 hours.

FIG. 12a is a scanning electron microscope image of the zinc oxide nanorod array with a surface loaded with potassium chloride prepared in example 8; FIG. 12b is a scanning electron microscope image of the zinc oxide nanorod array with potassium chloride loaded on the surface, prepared in example 8, standing in ultrapure water for 1 h; FIG. 12c is a scanning electron microscope image of the zinc oxide nanorod array with potassium chloride loaded on the surface, prepared in example 8, standing in ultrapure water for 2 h; FIG. 12d is a scanning electron microscope image of the zinc oxide nanorod array with the surface loaded with potassium chloride prepared in example 8 standing in ultrapure water for 5 h.

From the scanning electron micrograph of the potassium chloride-loaded zinc oxide nanorod array of fig. 12a, it can be seen that the surface of the zinc oxide nanorod array becomes rough. As shown in FIGS. 12b, 12c and 12d, the morphology of the sample was not changed when the sample was left to stand in ultrapure water for 1-5 hours. By combining example 7 and example 8, it is demonstrated that zinc oxide cannot be reduced in the absence of current to generate a zinc oxide nanorod array composited with elemental zinc, and that the reaction between elemental zinc nanoparticles and water does not occur when the zinc oxide nanorod array is allowed to stand in ultrapure water, and a nanosheet structure cannot be formed.

The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.