CN103496733A - Method for preparing carbon doped zinc oxide - Google Patents

Abstract

The invention provides a method for preparing carbon-doped zinc oxide, dissolving zinc gluconate in water to obtain a zinc gluconate solution, and then adjusting the pH value of the zinc gluconate solution to 6-8; Put the acid zinc solution into a microwave hydrothermal synthesizer, carry out the synthesis reaction at 180 ° C ~ 250 ° C, and then naturally cool to room temperature to obtain the product; the product is centrifuged to collect the solid, and then the solid is washed and dried to obtain Brown zinc oxide precursor; the brown zinc oxide precursor is calcined to obtain carbon-doped zinc oxide. The invention has the characteristics of short reaction time, high efficiency and good repeatability; zinc gluconate is used as raw material to be environmentally friendly and pollution-free; the carbon-doped zinc oxide prepared by the invention has uniform particle size, loose porous structure, high specific surface area and high purity High carbon doping, good controllability, and excellent visible light absorption.

Description

A method for preparing carbon-doped zinc oxide

technical field

The invention belongs to the technical field of semiconductor material preparation, and in particular relates to a preparation method of carbon-doped zinc oxide.

Background technique

ZnO is a new type of direct bandgap semiconductor material. Its forbidden band width is 3.2eV, and the exciton binding energy is 60meV. It has excellent photoelectric properties and can be widely used in light-emitting diodes, photocatalysis, solar cells, and gas sensors. , biosensors and other fields have attracted the attention of scientific and technological workers. In recent years, with the rapid development of nanotechnology, nano-ZnO with different shapes has been prepared by various methods, showing many unique physical and chemical properties. Among them, the photocatalytic properties of nano-ZnO are favored by researchers. At present, people have done a lot of research on it, but they mainly focus on controlling the morphology of ZnO, increasing its specific surface area, and only improving the catalytic activity of the material under ultraviolet light irradiation. Ultraviolet light only accounts for 5% of sunlight. Although these works are innovative, they are still far away from practical applications. Visible light makes up 46% of sunlight compared to ultraviolet light. Therefore, on the basis of preparing high specific surface area morphology, it is of great significance to develop ZnO photocatalytic materials with high visible light catalytic activity for its practical application.

At present, metal element ion doping such as Fe, Cr, Sb, Co, Mn, and Ni or non-metal element N, C, and S doping is usually used to improve the absorption capacity of semiconductor oxides for visible light, and certain results have been achieved. However, compared with transition metal ion-based cation doping, the research on anion doped photocatalysts is less and the method is more complicated. Chinese invention patent 201210466728.4 reports a simple method for preparing carbon-doped mesoporous ZnO Hamburg structure nanoassemblies. In this method, ethylene glycol is used as the reaction solvent, the transition metal inorganic salt zinc acetate and excess alkali source are used as the reaction precursor, and the structure-directing agent glucose is added to achieve carbon doping by inducing polymerization and twinning polar field drive. Self-assembly of ZnO nanoparticles. Chinese invention patent 201110332997.7 reports a carbon-doped semiconductor oxide with visible light catalytic activity and its preparation method. Metal salt, urea and carbon source are dissolved in distilled water and stirred to obtain a precursor solution, which is placed in a high-pressure reactor and sealed for reaction. ; Cooling, washing with deionized water, drying in vacuum; then roasting to obtain carbon-doped semiconductor oxide. The above-mentioned preparation methods all need to add a structure-directing agent to the reaction system or add substances such as urea and carbon source to participate in the synthesis. The conditions are harsh and the process is complicated, which is not conducive to industrialization.

Contents of the invention

The object of the present invention is to provide a method for preparing carbon-doped zinc oxide, which has the advantages of short reaction time, low reaction temperature, simple operation and good repeatability.

To achieve the above object, the present invention adopts the following technical solutions:

The present invention comprises the following steps:

1) Dissolving zinc gluconate in water to obtain a zinc gluconate solution, and then adjusting the pH of the zinc gluconate solution to 6-8; wherein, the concentration of zinc gluconate in the zinc gluconate solution is 0.1-1mol/L;

2) Put the pH-adjusted zinc gluconate solution into a microwave hydrothermal synthesizer, carry out the synthesis reaction at 180°C to 250°C, and then naturally cool to room temperature to obtain the product;

3) Centrifuge the product, collect the solid, then wash and dry the solid to obtain a brown zinc oxide precursor;

4) Calcining the brown zinc oxide precursor at 200-400° C., and naturally cooling to room temperature to obtain carbon-doped zinc oxide.

The pH value in step 1) is adjusted by KOH solution, NaOH solution or ammonia water.

The concentrations of the KOH solution, NaOH solution and ammonia water are all 0.2-1mol/L.

The synthesis reaction time in the step 2) is 1h-3h.

The washing in step 3) specifically includes washing the solid with deionized water and absolute ethanol respectively.

The calcining time in the step 4) is 0.5-2 hours.

The present invention has the following beneficial effects: the present invention uses zinc gluconate as the raw material, without adding other inducers or carbon sources, utilizes microwave-assisted hydrothermal method to synthesize the precursor of zinc oxide, and then synthesizes the precursor of zinc oxide by low-temperature calcination. Carbon doped zinc oxide. In the present invention, the calcination temperature is low, and carbon doping can be completed at a temperature of 200-400°C; the microwave-assisted hydrothermal synthesis method makes the present invention have the characteristics of short reaction time, high efficiency, and good repeatability; Zinc acid is a raw material that is environmentally friendly and pollution-free; the carbon-doped zinc oxide prepared by the present invention has a uniform particle size, a loose porous structure, a high specific surface area, high purity, good controllability of carbon doping, and excellent visible light absorption. It is applied in the fields of visible light photocatalysis and solar energy utilization.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) spectrum of the carbon-doped zinc oxide prepared by the present invention; Wherein Fig. 1 (a) is the XRD comparison of the product before and after calcination; Fig. 1 (b) is the XRD partial enlarged view of the product after calcination ;

Figure 2 is a scanning electron microscope (SEM) photo of carbon-doped zinc oxide prepared in the present invention; wherein Figure 2 (a) is the morphology of carbon-doped zinc oxide 5000 times; Figure 2 (b) is carbon-doped zinc oxide 20000 Figure 2(c) is the morphology of carbon-doped zinc oxide 100000 times;

Fig. 3 is the ultraviolet-visible absorption spectrum of the carbon-doped zinc oxide prepared in the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 0.2mol/L NaOH solution as a pH regulator to adjust the pH of the zinc gluconate solution to 6; among them, gluconic acid in the zinc gluconate solution The concentration of zinc is 0.1mol/L;

2) Add the pH-adjusted zinc gluconate solution into a microwave digestion tank, then move the microwave digestion tank into a microwave hydrothermal synthesizer, perform a synthesis reaction at 180°C for 3 hours, and then cool naturally to room temperature to obtain the product;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined in an air atmosphere at 200°C for 2 hours, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

The visible light absorption intensity of the carbon-doped zinc oxide obtained in this example is 0.23.

Example 2

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 1mol/L NaOH solution as a pH regulator to adjust the pH of the zinc gluconate solution to 8; among them, zinc gluconate in the zinc gluconate solution The concentration is 1mol/L;

2) Add the pH-adjusted zinc gluconate solution into a microwave digestion tank, then move the microwave digestion tank into a microwave hydrothermal synthesizer, perform a synthesis reaction at 250°C for 1 hour, and then cool naturally to room temperature to obtain the product;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined at 400°C in an air atmosphere for 0.5 hours, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

The visible light absorption intensity of the carbon-doped zinc oxide obtained in this example is 0.15.

Example 3

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 0.5mol/L NaOH solution as a pH regulator to adjust the pH of the zinc gluconate solution to 7; among them, the gluconic acid in the zinc gluconate solution The concentration of zinc is 0.5mol/L;

2) Add the pH-adjusted zinc gluconate solution into a microwave digestion tank, then move the microwave digestion tank into a microwave hydrothermal synthesizer, perform a synthesis reaction at 200°C for 2 hours, and then cool naturally to room temperature to obtain the product;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined in an air atmosphere at 300°C for 1 hour, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

The visible light absorption intensity of the carbon-doped zinc oxide obtained in this example is 0.45.

Example 4

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, then use 0.8mol/L NaOH solution as a pH regulator to adjust the pH of the zinc gluconate solution to 7; among them, the gluconic acid in the zinc gluconate solution The concentration of zinc is 0.3mol/L;

2) Add the zinc gluconate solution after adjusting the pH value into the microwave digestion tank, then move the microwave digestion tank into the microwave hydrothermal synthesizer, carry out the synthesis reaction at 220°C for 2 hours, and then naturally cool to room temperature to obtain the product;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined in an air atmosphere at 350°C for 0.5 hours, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

The visible light absorption intensity of the carbon-doped zinc oxide obtained in this example is 0.30.

Example 5

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 0.2mol/L KOH solution as a pH regulator to adjust the pH of the zinc gluconate solution to 6.5; among them, gluconic acid in the zinc gluconate solution The concentration of zinc is 0.6mol/L;

2) Add the zinc gluconate solution after adjusting the pH value into the microwave digestion tank, then move the microwave digestion tank into the microwave hydrothermal synthesizer, carry out the synthesis reaction at 190°C for 1.5h, and then naturally cool to room temperature to obtain the product ;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined in an air atmosphere at 250°C for 1.5 hours, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

Example 6

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 1mol/L ammonia water as a pH regulator to adjust the pH of the zinc gluconate solution to 7.5; wherein, the zinc gluconate in the zinc gluconate solution The concentration is 0.8mol/L;

2) Add the zinc gluconate solution after adjusting the pH value into the microwave digestion tank, then move the microwave digestion tank into the microwave hydrothermal synthesizer, carry out the synthesis reaction at 235°C for 2.5 hours, and then cool naturally to room temperature to obtain the product ;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined in an air atmosphere at 200°C for 2 hours, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

Example 7

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 1mol/L KOH solution as a pH regulator to adjust the pH of the zinc gluconate solution to 6; among them, zinc gluconate in the zinc gluconate solution The concentration is 0.6mol/L;

2) Add the pH-adjusted zinc gluconate solution into a microwave digestion tank, then move the microwave digestion tank into a microwave hydrothermal synthesizer, perform a synthesis reaction at 180°C for 3 hours, and then cool naturally to room temperature to obtain the product;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined at 400°C in an air atmosphere for 1 hour, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

Example 8

1) Dissolve zinc gluconate in water to obtain a zinc gluconate solution, and then use 0.2mol/L ammonia water as a pH regulator to adjust the pH of the zinc gluconate solution to 8; among them, zinc gluconate in the zinc gluconate solution The concentration is 0.8mol/L;

2) Add the pH-adjusted zinc gluconate solution into a microwave digestion tank, then move the microwave digestion tank into a microwave hydrothermal synthesizer, perform a synthesis reaction at 250°C for 1 hour, and then cool naturally to room temperature to obtain the product;

3) Centrifuge the product to collect the solid, then wash the solid with deionized water and absolute ethanol, and dry it to obtain a brown zinc oxide precursor;

4) The product was calcined in an air atmosphere at 200°C for 2 hours, and cooled naturally to room temperature to obtain carbon-doped zinc oxide.

Please refer to FIG. 1, which is an XRD spectrum of carbon microspheres prepared by the method of the present invention. It can be seen from Fig. 1(a): ZnO before calcination has poor crystallinity and low purity, and ZnO after calcination is ZnO with pure phase and hexagonal wurtzite structure. It can be seen from Figure 1(b) that the position of the diffraction peak of the calcined zinc oxide shifts to a large angle direction, indicating that the ZnO lattice is distorted. Since the radius of the covalent carbon is 77 picometers, which is much smaller than that of the oxygen The radius of the ions is 140 picometers, indicating that carbon has successfully replaced part of the oxygen in zinc oxide and achieved doping.

Please refer to FIG. 2 . FIG. 2 is the SEM morphology of the carbon-doped zinc oxide prepared in the present invention. It can be seen from Figure 2 (a) that the carbon-doped zinc oxide prepared by the present invention has a size of about 5 μm and has a porous and loose structure; it can be seen from Figure 2 (b) that the particles of carbon-doped zinc oxide There are many nanoscale pores on the surface; it can be seen from Figure 2(c): carbon-doped zinc oxide is assembled by many nanoparticles, and the size of these particles is about 50-100nm.

Please refer to FIG. 3 . FIG. 3 is the ultraviolet-visible absorption spectrum of the carbon-doped zinc oxide prepared in the present invention. As can be seen from Figure 3: compared with pure zinc oxide, the carbon-doped zinc oxide prepared by the present invention not only has a stronger absorption capacity in the ultraviolet light region, but also has an absorption peak that can shift to the light region, and in the visible light region ( 400nm to 800nm) also exhibits strong absorption capacity, and the carbon-doped zinc oxide prepared by the present invention has excellent visible light responsiveness, and has great potential in the fields of visible light photocatalysis and solar energy utilization.

The present invention uses zinc gluconate as a raw material, dissolves it in water, adjusts the pH to 6-8, and undergoes microwave hydrothermal reaction, washing, and drying to obtain a zinc oxide precursor, which is then calcined at a low temperature (200-400°C). , and high-purity carbon-doped zinc oxide with a porous structure can be obtained. The invention uses zinc gluconate as a raw material without adding other inducers or carbon sources, utilizes a microwave-assisted hydrothermal method to synthesize a zinc oxide precursor, and then synthesizes carbon-doped zinc oxide with a loose porous structure by a low-temperature calcination method. The carbon-doped zinc oxide obtained by the invention has the characteristics of high specific surface area, high purity, good controllability of carbon doping amount and excellent visible light absorption.

Claims (6)

1. a method for preparing carbon-doped zinc oxide, is characterized in that, comprises the following steps: 1) Dissolving zinc gluconate in water to obtain a zinc gluconate solution, and then adjusting the pH of the zinc gluconate solution to 6-8; wherein, the concentration of zinc gluconate in the zinc gluconate solution is 0.1-1mol/L; 2) Put the pH-adjusted zinc gluconate solution into a microwave hydrothermal synthesizer, carry out the synthesis reaction at 180°C to 250°C, and then naturally cool to room temperature to obtain the product; 3) Centrifuge the product, collect the solid, then wash and dry the solid to obtain a brown zinc oxide precursor; 4) Calcining the brown zinc oxide precursor at 200-400° C., and naturally cooling to room temperature to obtain carbon-doped zinc oxide. 2. A method for preparing carbon-doped zinc oxide according to claim 1, characterized in that the pH value in step 1) is adjusted by KOH solution, NaOH solution or ammonia water. 3. A kind of method for preparing carbon-doped zinc oxide according to claim 2, is characterized in that, the concentration of described KOH solution, NaOH solution, ammoniacal liquor is 0.2-1mol/L. 4. A method for preparing carbon-doped zinc oxide according to claim 1, characterized in that the synthesis reaction time in the step 2) is 1 h to 3 h. 5 . The method for preparing carbon-doped zinc oxide according to claim 1 , wherein the washing in step 3) specifically washes the solid with deionized water and absolute ethanol. 5 . 6 . The method for preparing carbon-doped zinc oxide according to claim 1 , characterized in that the calcination time in step 4) is 0.5-2 hours.

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