Preparation method of zinc oxide nano material with high specific surface area

Abstract

The invention discloses a preparation method of a zinc oxide nano material with a high specific surface area. The method comprises the following steps: firstly, mixing a zinc source and a growth adjuvant according to a molar ratio of 1: 1, preparing a growth base solution with the total concentration of 0.01-0.1 mol / L, adding ammonia water, and adjusting the pH value to 9-11; then adding sodium cholate into the solution, stirring, transferring the solution into a reaction kettle, and growing in a constant-temperature drying box; and finally, taking out the solution from the reaction kettle, adding sodium cholate into the solution again, stirring, transferring the solution into the reaction kettle, and growing in a constant-temperature drying box to obtain the zinc oxide nano material with high specific surface area. The crystal surface energy is controlled by adding sodium cholate in multiple stages, and the specific surface area of the zinc oxide nano material is remarkably increased. The increase of the specific surface area provides a larger active surface for the application of the material in a gas sensitive sensor, so that the sensitivity and response speed of the sensor are improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a nano material, in particular to a method for preparing a zinc oxide nano material with a high specific surface area, and belongs to the field of nano materials and gas sensors. Background Art

[0002] Zinc oxide (ZnO) is an important semiconductor material with a wide band gap, high chemical stability, and excellent optical and electrical properties. Therefore, it has broad application prospects in optoelectronic devices, catalysts, gas sensors, etc. Especially in the field of gas sensors, zinc oxide has become one of the hot research materials due to its unique surface properties and sensitive gas detection capabilities.

[0003] The specific surface area of ​​zinc oxide is one of the important factors affecting its performance, especially in gas sensors, where a high specific surface area can provide more active sites, which is conducive to the adsorption and reaction of gas molecules and improves the sensitivity and response speed of the sensor. Therefore, the preparation of zinc oxide nanomaterials with high specific surface area has become a key issue in the current technological development.

[0004] In the prior art, the method for preparing zinc oxide nanomaterials mainly includes solution method, precipitation method, hydrothermal method, etc., which can effectively synthesize nano-scale zinc oxide materials. However, there are some shortcomings in the traditional method, such as the inability to effectively control the growth process of the crystal, resulting in a limited or uneven specific surface area of ​​the material, thereby affecting its gas-sensitive performance. At the same time, the positively charged ions in the solution will also corrode or nanorods, affecting crystal growth. In addition, the crystal is prone to agglomeration during the growth process, which also makes the specific surface area of ​​the nanomaterial finally obtained unsatisfactory. Therefore, how to accurately control the growth direction and surface energy of zinc oxide crystals during the preparation process and further improve the specific surface area of ​​the material is still a problem to be solved in the current technical field. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a zinc oxide nano material with a high specific surface area. The prepared zinc oxide nano material has a high specific surface area.

[0006] In order to solve the above problems, the present invention provides a method for preparing a zinc oxide nanomaterial with a high specific surface area, and the preparation of zinc oxide with a high specific surface area is achieved by controlling the crystal surface energy at different growth stages. The specific steps are as follows:

[0007] First, a zinc source and a growth aid are mixed in a molar ratio of 1:1, deionized water is added to prepare a growth base solution with a total concentration of 0.01-0.1 mol / L, ammonia water with a concentration of 5-20 wt% is added, and the pH is adjusted to 9-11;

[0008] Then, 0.005-0.01% sodium cholate is added to the solution, and then stirred, and the solution is transferred to a reaction kettle, and grown in a constant temperature drying oven at a temperature of 83-97° C. for 2-3 hours;

[0009] Finally, the solution was taken out from the reactor, and sodium cholate with a mass fraction of 0.001-0.004% was added to the solution again, and then stirred. The solution was transferred to the reactor and grown in a constant temperature drying oven at a temperature of 95-99°C for 4-6 hours to obtain a zinc oxide nanomaterial with a high specific surface area.

[0010] Particularly, in step 1, the zinc source is one of zinc nitrate and zinc acetate, and the growth aid is one of hexamethylenetetramine and sodium hydroxide.

[0011] Particularly, in step 2, the stirring rate is 120-180 rpm, and the stirring time is 0.5-3 h.

[0012] Particularly, in step three, the stirring rate is 300-450 rpm, and the stirring time is 1-4 h.

[0013] The present invention also provides application of the high specific surface area zinc oxide nanomaterial prepared by the preparation method in a gas sensor.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The present invention controls the crystal surface energy by adding sodium cholate in multiple stages, significantly increasing the specific surface area of ​​the zinc oxide nanomaterial. The increase in specific surface area provides a larger active surface for the application of the material in the gas sensor, thereby improving the sensitivity and response speed of the sensor.

[0016] 2. By precisely controlling the concentration of sodium cholate at different growth stages, the surface energy of the growing crystals can be controlled, which can effectively regulate the growth dynamics of the crystals. At the same time, sodium cholate is very easy to adsorb on the surface of the crystal prism, promoting nucleation, and also effectively occupying the site to avoid agglomeration and irregular growth, thereby obtaining a uniform nanoparticle structure. Different from the traditional single addition, the multi-stage addition process of the present invention ensures the stability and uniformity of the material at each growth stage.

[0017] 3. Since zinc oxide nanomaterials with high specific surface area have more active sites, they can significantly improve the capture ability and detection sensitivity of gas-sensitive materials to gas molecules, and are particularly suitable for use in gas sensors, thereby improving the detection accuracy and response time of the sensor.

[0018] 4. The preparation process adopted by the present invention is simple and easy to operate, suitable for industrial-scale production, and has mild reaction conditions, low cost and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a graph of the specific surface area of ​​the materials prepared in Examples 1-3 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] The raw materials used in the following examples are all commercially available powders with a purity greater than 98%.

[0022] Example 1

[0023] Weigh zinc nitrate as a zinc source and hexamethylenetetramine as a growth aid, mix them in a molar ratio of 1:1, add deionized water to prepare a solution with a total concentration of 0.05 mol / L, then add 15 wt% ammonia water and adjust the pH to 10.

[0024] 0.007% sodium cholate was added to the solution with a stirring rate of 150 rpm. After stirring for 2 hours, the solution was transferred to a reaction kettle and placed in a constant temperature drying oven at 85° C. for reaction for 2.5 hours.

[0025] The solution was taken out, 0.002% sodium cholate was added, and the stirring rate was 350 rpm. After stirring for 1 hour, the solution was transferred to the reactor again and grown at 98°C for 4 hours. Finally, a high specific surface area zinc oxide nanomaterial was obtained, and the tested specific surface area was 102m 2 / g.

[0026] Example 2

[0027] Zinc acetate was used as a zinc source and sodium hydroxide was used as a growth aid, mixed at a molar ratio of 1:1, and deionized water was added to prepare a solution with a total concentration of 0.08 mol / L. 10 wt% ammonia water was added to adjust the pH to 9.5.

[0028] 0.008% sodium cholate was added to the solution with a stirring rate of 170 rpm. After stirring for 1.5 hours, the solution was transferred to a reaction kettle and placed in a constant temperature drying oven at 87° C. for reaction for 3 hours.

[0029] The solution was taken out, 0.003% sodium cholate was added, and the stirring rate was 400 rpm. After stirring for 2 hours, the solution was transferred to the reactor again and grown at 97°C for 5 hours. The specific surface area of ​​the zinc oxide nanomaterial finally obtained was 106m 2 / g.

[0030] Example 3

[0031] Zinc nitrate was used as a zinc source and hexamethylenetetramine was used as a growth aid, mixed at a molar ratio of 1:1, and deionized water was added to prepare a solution with a total concentration of 0.03 mol / L. 20 wt% ammonia water was added to adjust the pH to 11.

[0032] 0.006% sodium cholate was added to the solution with a stirring rate of 130 rpm. After stirring for 1 hour, the solution was transferred to a reaction kettle and placed in a 90° C. constant temperature drying oven for reaction for 2 hours.

[0033] The solution was taken out, 0.001% sodium cholate was added, and the stirring rate was 320 rpm. After stirring for 3 hours, the solution was transferred to the reactor again and grown at 99°C for 6 hours. The specific surface area of ​​the zinc oxide nanomaterial finally obtained was 107m 2 / g.

[0034] Comparative Example 1

[0035] Zinc nitrate was used as a zinc source and hexamethylenetetramine was used as a growth aid, mixed at a molar ratio of 1:1, and deionized water was added to prepare a solution with a total concentration of 0.03 mol / L. 20 wt% ammonia water was added to adjust the pH to 11.

[0036] The solution was stirred at a stirring rate of 130 rpm. After stirring for 1 hour, the solution was transferred to a reaction kettle and placed in a constant temperature drying oven at 90° C. for reaction for 2 hours.

[0037] The solution was taken out and continued to be stirred at a rate of 320 rpm. After stirring for 3 hours, the solution was transferred to the reactor again and grown at 99°C for 6 hours. The specific surface area of ​​the zinc oxide nanomaterial finally obtained was 65 m 2 / g.

[0038] Comparative Example 2

[0039] Zinc nitrate was used as a zinc source and hexamethylenetetramine was used as a growth aid, mixed at a molar ratio of 1:1, and deionized water was added to prepare a solution with a total concentration of 0.03 mol / L. 20 wt% ammonia water was added to adjust the pH to 11.

[0040] 0.006% sodium cholate was added to the solution with a stirring rate of 130 rpm. After stirring for 1 hour, the solution was transferred to a reaction kettle and placed in a 90° C. constant temperature drying oven for reaction for 2 hours.

[0041] The solution was taken out and continued to be stirred at a rate of 320 rpm. After stirring for 3 hours, the solution was transferred to the reactor again and grown at 99°C for 6 hours. The specific surface area of ​​the zinc oxide nanomaterial finally obtained was 79 m 2 / g.

[0042] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a high specific surface area zinc oxide nanomaterial, It is characterized in that The following steps are involved: Step 1: Mix a zinc source and a growth aid in a molar ratio of 1:1, add deionized water to prepare a growth base solution with a total concentration of 0.01 to 0.1 mol / L, add 5 to 20 wt% ammonia water, and adjust the pH to 9 to 11; Step 2, adding 0.005-0.01% sodium cholate by mass to the solution, then stirring, transferring the solution to a reaction kettle, and growing in a constant temperature drying oven at 83-97° C. for 2-3 hours; Step three, taking out the solution from the reactor, adding 0.001-0.004% sodium cholate to the solution again, and then stirring, transferring the solution to the reactor, and growing it in a constant temperature drying oven at a temperature of 95-99° C. for 4-6 hours to obtain a high specific surface area zinc oxide nanomaterial.

2. A method for preparing a high specific surface area zinc oxide nanomaterial according to claim 1, It is characterized in that In step 1, the zinc source is one of zinc nitrate and zinc acetate, and the growth aid is one of hexamethylenetetramine and sodium hydroxide.

3. A method for preparing a high specific surface area zinc oxide nanomaterial according to claim 1, It is characterized in that In step 2, the stirring rate is 120-180 rpm, and the stirring time is 0.5-3 h.

4. A method for preparing a high specific surface area zinc oxide nanomaterial according to claim 1, It is characterized in that In step three, the stirring rate is 300-450 rpm, and the stirring time is 1-4 h.

5. Application of the high specific surface area zinc oxide nanomaterial prepared by the preparation method according to any one of claims 1 to 4 in a gas sensor.

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