CN108940259B - Hierarchical porous MoO2Photocatalyst microsphere and preparation method thereof - Google Patents

Abstract

_A hierarchically structured porous MoO2 photocatalyst microsphere and a preparation method thereof belong to photocatalyst microspheres and a preparation method thereof. _The porous MoO2 photocatalyst microspheres of the present invention are composed of a porous outer shell and an inner reticulated porous skeleton; the method uses citric acid as fuel, ammonium paramolybdate as raw material, water as solvent, and is configured by magnetic stirring to form The solution is mixed, and then sprayed into a tube furnace at 400-500° C. by ultrasonic spraying to prepare hierarchically structured hollow porous MoO ₂ photocatalyst microspheres. The preparation system of the invention has the advantages of simple process method, cheap raw materials, economical feasibility and the like. The catalyst prepared by the invention has a special hierarchical structure, and also has the characteristics of hollow and porous morphology, small particle size, uniform distribution without agglomeration, microsphere diameter between 0.5-2 μm, good photocatalytic performance and good hydrophilicity. , which is beneficial to applications in photocatalysis, water pollution treatment, lithium-ion batteries, supercapacitors, gas sensors and other fields.

Description

A kind of hierarchical structure porous MoO2 photocatalyst microsphere and preparation method thereof

technical field

The invention relates to a photocatalyst microsphere and a preparation method thereof, in particular to a hierarchical structure porous MoO2 photocatalyst microsphere and a preparation method thereof.

Background technique

Photocatalytic oxidation technology is considered to be one of the most promising technologies to solve the problem of environmental pollution. So far, more than 3,000 refractory organic compounds have been found to be rapidly degraded by photocatalytic oxidation. Among the semiconductors commonly used in photocatalysis technology, MoO2 has relatively low preparation cost, low crystallization and growth temperature, and is easy to prepare various morphologies and structures, which has attracted more and more attention. However, the preparation of MoO2 is difficult, and it is easily oxidized to MoO3 during the preparation process, reducing its purity. Moreover, MoO2 still has the problems of low solar energy utilization and high carrier recombination rate in practical applications. At present, in order to further improve the photocatalytic performance, the main methods used include morphology control, construction of composite systems, doping, and surface modification of additives.

For traditional semiconductor oxide photocatalytic materials, the modification of the morphology and size of the catalyst is the simplest and most effective method to improve the photocatalytic performance. At present, there are many preparation methods for controlling the morphology of MoO2. Among them, solution combustion synthesis is one of the most widely studied and widely used catalyst preparation methods. The solution combustion method is a wet chemical synthesis method. It uses external energy to induce a chemical reaction of the reactants, and the released heat promotes the automatic spread of the reaction in the form of a combustion wave. It has the advantages of simple preparation process, low synthesis temperature, short time and synthesis powder size. Small and other advantages. The synthesis technology mainly regulates the phase composition, particle size, microscopic morphology and other properties of the synthesized powder by adjusting the heat released during the combustion process and its rate. However, the above methods have uncontrollable preparation temperature, and the prepared catalyst is easy to agglomerate and has poor reusability, resulting in poor photocatalytic performance of the catalyst synthesized by solution combustion, which limits the application of photocatalytic technology in practical production.

Because solution combustion synthesis relies on the heat released by the combustion of organic matter to maintain the reaction, most of the research work is focused on the effect of the choice of organic fuel on the morphology of the product. However, no matter what organic matter is selected, the final product is a foamy oxide powder with serious agglomeration, which has little effect on the morphology of the product.

SUMMARY OF THE INVENTION

In view of the above defects, the purpose of the present invention is to provide a hierarchically structured porous MoO2 photocatalyst microsphere and a preparation method thereof, so as to solve the problems of difficulty in preparing MoO2 catalyst by the existing solution combustion method, uncontrollable temperature, easy agglomeration and poor recycling rate.

The purpose of the present invention is achieved in this way, including: porous MoO2 photocatalyst microspheres and a preparation method of porous MoO2 photocatalyst microspheres.

The porous MoO2 photocatalyst microspheres are composed of a porous outer shell and an inner reticulated porous skeleton.

The diameter of the porous MoO2 photocatalyst microspheres is 0.5-2 μm.

The inner mesh-like porous pore diameter of the porous MoO2 photocatalyst microsphere is 50-200 nm.

The preparation method of the porous MoO2 photocatalyst microspheres comprises the following steps:

Step 1. Prepare a solution: dissolve ammonium paramolybdate and citric acid into water, and magnetically stir to configure a mixed solution; wherein water 10 mL; ammonium paramolybdate 1.5-2.5 mmol; citric acid 1-3 mmol; The purity of ammonium paramolybdate was 99.6%; the purity of citric acid was analytically pure; the water was deionized water.

Step 2. Put the mixed solution prepared in step 1 into the ultrasonic atomizer, and the mixed solution is atomized by the ultrasonic atomizer; the atomized mixed solution is blown into the tubular heating furnace through air, and the air carries the atomization. The flow rate of the mixed solution is 20-40 mL/h; porous MoO2 photocatalyst microspheres are obtained at the outlet end of the tube furnace.

The tube furnace has a working lumen, the inlet end of the working lumen is provided with a tee, one end is connected to the working lumen, one end is connected to the output end of the ultrasonic atomizer, and one end is connected to the air output end; There is a heating device outside, the temperature at the middle position of the working lumen is 400-500°C, and the temperature at both ends is room temperature; the outlet end of the working lumen is the product outlet.

Beneficial effect, because the above scheme is adopted, in the solution, water is used as solvent, ammonium paramolybdate is used as molybdenum source, and citric acid is used as fuel; In the tube furnace at a temperature of 400-500 °C, the entire spraying process is carried out in an air atmosphere. During the combustion process, ammonium paramolybdate is reduced by citric acid to generate fine MoO2 nanoparticles. After the combustion is completed, it is cooled with the furnace. During the process, nanoparticles aggregate and crystallize on the surface of the microspheres to form a hierarchical structure, and finally generate porous MoO2 photocatalyst microspheres.

The invention creatively combines ultrasonic spraying and solution combustion, reduces the agglomeration between catalysts, and prepares uniformly dispersed porous oxides. After rough calculation, 10 mL of solution is atomized into countless 1 μm droplets through ultrasonic spraying, which is equivalent to The solution is refined into 239 billion reaction units, which will greatly improve the rate and degree of homogenization of the reaction. Ultrasonic spraying is combined with solution combustion for the preparation of photocatalysts. There is no report on the synthesis of ultrasonic spraying solution combustion.

Compared with the traditional solution combustion synthesis, the hierarchically structured porous MoO2 microspheres prepared by the ultrasonic spray solution combustion synthesis method of the present invention have a faster and more complete reaction because the solution exists in the form of ultra-fine mist droplets. The prepared catalyst is not easy to agglomerate, and also has the special morphology of hierarchical structure and porous.

(1) The solution combustion is refined to the micron level by ultrasonic spraying. Compared with traditional solution combustion, the reaction time of ultrasonic spraying solution combustion is shorter and more sufficient, the microscopic size of the product is smaller, it is not easy to agglomerate, and the hydrophilicity is better.

(2) Under the condition that no combustion aid is added, the solution combustion reaction of ammonium paramolybdate will not occur. The present invention atomizes the solution to the micron level, shortens the distance of reaction diffusion, and makes some reactions that are difficult to be synthesized by solution combustion can be Prepared by ultrasonic spray solution combustion synthesis.

(3) The prepared MoO2 has a hierarchical structure and a special porous morphology. The catalyst advantages of this structure are: the hierarchical structure can be more conducive to the transport of substances on the basis of maintaining the nanostructure characteristics; the porous structure can improve the catalyst. The selectivity increases the reaction rate, provides more low-coordination atoms to promote catalysis, and increases light scattering and absorption.

Advantages: the preparation system process method of the present invention is simple to operate, and the raw materials are cheap and economically feasible. The photocatalyst microspheres prepared by the invention have a special hierarchical structure, and also have hollow and porous morphological characteristics, small particle size, uniform distribution without agglomeration, the diameter of the microspheres is between 0.5 and 2 μm, and the photocatalytic performance is good. It has good water quality and is beneficial to applications in photocatalysis, water pollution treatment, lithium-ion batteries, supercapacitors, gas sensors and other fields.

Description of drawings

Fig. 1 is the preparation process schematic diagram of the present invention;

Fig. 2 is the XRD pattern of the phase composition of porous MoO photocatalyst microspheres of the present invention;

Figure 3(a) is the SEM image of MoO2 prepared at 400°C;

Figure 3(b) is the SEM image of MoO2 prepared at 500°C;

Fig. 3(c) is a partial enlarged view of Fig. 3(a);

Fig. 3(d) is a partial enlarged view of Fig. 3(b);

Figure 4 (a) is methylene blue and rhodamine B at 30 mg/L;

Figure 4(b) The photocatalytic curves of MoO2 and commercial TiO2 measured with 30 mg/L methylene blue as the pollutant.

Detailed ways

As shown in Figure 1, the hierarchically structured porous MoO2 photocatalyst microspheres of the present invention include:

The porous MoO2 photocatalyst microspheres are composed of a porous outer shell and an inner reticulated porous skeleton.

The diameter of the porous MoO2 photocatalyst microspheres is 0.5-2 μm.

The inner mesh-like porous pore diameter of the porous MoO2 photocatalyst microsphere is 50-200 nm.

A preparation method of porous MoO2 photocatalyst microspheres comprises the following steps:

Step 1. Prepare a solution: dissolve ammonium paramolybdate and citric acid into water, and magnetically stir to configure a mixed solution; wherein water 10 mL; ammonium paramolybdate 1.5-2.5 mmol; citric acid 1-3 mmol; The purity of ammonium paramolybdate was 99.6%; the purity of citric acid was analytically pure; the water was deionized water.

Step 2. Put the mixed solution prepared in step 1 into the ultrasonic atomizer, and the mixed solution is atomized by the ultrasonic atomizer; the atomized mixed solution is blown into the tubular heating furnace through air, and the air carries the atomization. The flow rate of the mixed solution is 20-40 mL/h; porous MoO2 photocatalyst microspheres are obtained at the outlet end of the tube furnace.

As shown in Figure 2, the tube furnace has a working lumen, the inlet end of the working lumen has a tee, one end is connected to the working lumen, one end is connected to the output end of the ultrasonic atomizer, and one end is connected to the air output end Connection; there is a heating device outside the working lumen, the temperature in the middle of the working lumen is 400-500°C, and the temperature at both ends is room temperature; the outlet end of the working lumen is the product outlet.

The technical solutions of the present invention are further described below through some embodiments, but these embodiments should not be construed as limitations on the technical solutions.

Example 1: Weigh 1.5 mmol of ammonium paramolybdate and 1 mmol of citric acid respectively, dissolve them in 10 mL of deionized water, stir magnetically for 1 h at room temperature, and then move the prepared solution to an ultrasonic sprayer. The temperature was raised to 400 °C, and then the solution was ultrasonically sprayed into the tube furnace at a rate of 20 mL/h. The entire sintering process was completed in an air atmosphere, and no protective gas was required. MoO2 photocatalyst microspheres.

Fig. 3(a) is the SEM image of MoO2 prepared under the condition of 400°C, and Fig. 3(a) is a partial enlarged view of Fig. 3(c).

Figure 4(a) MoO2 prepared under the condition of 400 ℃ to methylene blue light catalytic curve, (b) photocatalytic curve of Rhodamine B and the photocatalytic performance comparison with commercial TiO2.

Example 2: Weigh 2mmol of ammonium paramolybdate and 2mmol of citric acid respectively, dissolve them in 10mL of deionized water, stir magnetically for 1h at room temperature, then move the configured solution to an ultrasonic sprayer, and heat up the tube furnace in advance to 400 °C, and then ultrasonically sprayed the solution into the tube furnace at a rate of 30 mL/h. The entire sintering process was completed in an air atmosphere, and no protective gas was required. MoO2 photocatalyst microspheres.

Example 3: Weigh 2.5 mmol of ammonium paramolybdate and 3 mmol of citric acid respectively, dissolve them in 10 mL of deionized water, stir magnetically for 1 h at room temperature, and then move the prepared solution to an ultrasonic sprayer. The temperature was raised to 450 °C, and then the solution was ultrasonically sprayed into the tube furnace at a rate of 40 mL/h. The entire sintering process was completed in an air atmosphere, and no protective gas was required. MoO2 photocatalyst microspheres.

Example 4: Weigh 1.5 mmol of ammonium paramolybdate and 1 mmol of citric acid respectively, dissolve them in 10 mL of deionized water, stir magnetically for 1 h at room temperature, and then move the prepared solution to an ultrasonic sprayer. The temperature was raised to 450 °C, and then the solution was ultrasonically sprayed into the tube furnace at a rate of 20 mL/h. The entire sintering process was completed in an air atmosphere, and no protective gas was required. MoO2 photocatalyst microspheres.

Example 5: Weigh 2 mmol of ammonium paramolybdate and 2 mmol of citric acid respectively, dissolve them in 10 mL of deionized water, stir magnetically for 1 h at room temperature, then move the configured solution to an ultrasonic sprayer, and heat the tube furnace in advance to 500 °C, and then ultrasonically spray the solution into the tube furnace at a rate of 30 mL/h. The entire sintering process is completed in an air atmosphere without protective gas. MoO2 photocatalyst microspheres.

Fig. 3(b) is the SEM image of MoO2 prepared under the condition of 500°C, and Fig. 3(b) is a partial enlarged view of Fig. 3(d). Figure 4 (a) the photocatalytic curve of MoO2 prepared at 500°C for methylene blue light, (b) the photocatalytic curve of Rhodamine B and the photocatalytic performance comparison with commercial TiO2.

Example 6: Weigh 2.5 mmol of ammonium paramolybdate and 3 mmol of citric acid respectively, dissolve them in 10 mL of deionized water, stir magnetically for 1 h at room temperature, and then move the prepared solution to an ultrasonic sprayer. The temperature was raised to 500 °C, and then the solution was ultrasonically sprayed into the tube furnace at a rate of 40 mL/h. The entire sintering process was completed in an air atmosphere without protective gas. MoO2 photocatalyst microspheres.

Claims (2)

1. Hierarchical porous MoO₂Photocatalyst microspheres, characterized by: porous MoO₂The photocatalyst microsphere consists of a porous shell and a reticular porous framework inside the shell;

porous MoO₂The diameter of the photocatalyst microspheres is 1-2 mu m;

porous MoO₂The diameter of the inner reticular porous pores of the photocatalyst microspheres is 50-200 nm;

porous MoO₂The preparation method of the photocatalyst microspheres comprises the following steps:

step 1, preparing a solution, namely dissolving ammonium paramolybdate and citric acid into water to prepare a solution, wherein the water is 10m L, the ammonium paramolybdate is 1.5-2.5 mmol, and the citric acid is 1-3 mmol, wherein the purity of the ammonium paramolybdate is 99.6%, the purity of the citric acid is analytically pure, and the water is deionized water;

step 2, placing the mixed solution prepared in the step 1 into an ultrasonic atomizer, atomizing the mixed solution through the ultrasonic atomizer, blowing the atomized mixed solution into a tubular heating furnace through air, wherein the flow rate of the atomized mixed solution carried by the air is 20-40 m L/h, and obtaining the porous MoO at the outlet end of the tubular heating furnace₂Photocatalyst microspheres;

the tube furnace is provided with a working tube cavity, the inlet end of the working tube cavity is provided with a tee joint, one end of the tee joint is introduced into the working tube cavity, the other end of the tee joint is connected with the output end of the ultrasonic atomizer, and the other end of the tee joint is connected with the air output end; a heating device is arranged outside the working tube cavity, the temperature of the middle position of the working tube cavity is 400-500 ℃, and the temperatures of the two ends are room temperature; the outlet end of the working tube cavity is a product outlet.

2. A method for preparing the hierarchical porous MoO of claim 1₂The preparation method of the photocatalyst microspheres is characterized by comprising the following steps: porous MoO₂The preparation method of the photocatalyst microspheres comprises the following steps:

step 1, preparing a solution, namely dissolving ammonium paramolybdate and citric acid into water to prepare a solution, wherein the water is 10m L, the ammonium paramolybdate is 1.5-2.5 mmol, and the citric acid is 1-3 mmol, wherein the purity of the ammonium paramolybdate is 99.6%, the purity of the citric acid is analytically pure, and the water is deionized water;

step 2, placing the mixed solution prepared in the step 1 into an ultrasonic atomizer, atomizing the mixed solution through the ultrasonic atomizer, blowing the atomized mixed solution into a tubular heating furnace through air, wherein the flow rate of the atomized mixed solution carried by the air is 20-40 m L/h, and obtaining the porous MoO at the outlet end of the tubular heating furnace₂Photocatalyst microspheres;

the tube furnace is provided with a working tube cavity, the inlet end of the working tube cavity is provided with a tee joint, one end of the tee joint is introduced into the working tube cavity, the other end of the tee joint is connected with the output end of the ultrasonic atomizer, and the other end of the tee joint is connected with the air output end; a heating device is arranged outside the working tube cavity, the temperature of the middle position of the working tube cavity is 400-500 ℃, and the temperatures of the two ends are room temperature; the outlet end of the working tube cavity is a product outlet.

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