CN108421545A - Manganese dioxide composite material and its preparation method and application - Google Patents

Abstract

A manganese dioxide composite material, comprising nano secondary particles assembled by δ- _MnO2 nanosheets and nano carbon, the nano secondary particles have a porous structure. The invention also provides a preparation method of the manganese dioxide composite material and its application in removing formaldehyde. The manganese dioxide composite material provided by the invention can quickly catalyze the degradation of formaldehyde at low temperature/room temperature, and has a high removal rate of formaldehyde. The preparation method of the manganese dioxide composite material provided by the invention is simple and easy to operate, and has low production cost.

Description

Manganese dioxide composite material and its preparation method and application

technical field

The invention relates to the field of materials, in particular to a manganese dioxide composite material and its preparation method and application.

Background technique

As an important chemical raw material, formaldehyde is widely used in various fields of life, especially decoration, decoration materials and furniture. Therefore, formaldehyde is widely exposed to indoor environments such as our life, work, and leisure. Formaldehyde in indoor environments pollution is widely concerned by the public. Based on a large number of human and animal experiments, the International Agency for Research on Cancer found that formaldehyde is extremely harmful to the human body and classified it as a class I carcinogen. Therefore, the level of formaldehyde in indoor air directly affects the health of people who have been active indoors for a long time. healthy. Aiming at the characteristics of low concentration and long release cycle of formaldehyde, people have done a lot of research on how to remove indoor formaldehyde, among which catalytic oxidation technology is considered to be the most effective method for removing formaldehyde.

Commonly used catalysts for catalyzing formaldehyde oxidation fall into two categories, noble metal catalysts and non-noble metal catalysts. Among them, noble metal catalysts can completely convert formaldehyde into carbon dioxide and water at room temperature, but the practical application of noble metal catalysts is limited due to the high cost of noble metals, lack of raw material resources, and easy deactivation during use. Therefore, the use of non-noble metal catalysts is an important direction for the degradation of formaldehyde. Transition metal oxides, especially manganese oxides, have been proven to degrade formaldehyde. However, the conversion rate of manganese dioxide to formaldehyde at room temperature is very low, which seriously limits its practical application.

Researchers have taken a lot of measures to improve the catalytic performance of manganese dioxide, for example, doping manganese dioxide with transition metals, etc. However, the conversion rate of manganese dioxide to formaldehyde at room temperature is still not ideal, such as Tian et al. The prepared MnO _x -CeO ₂ mixed oxide has a conversion rate of only 27% (HCHO: 580ppm) to formaldehyde at 60°C and a space velocity of 21L/gcat h (Appl.Catal.B:Environ., 2006,62,265); when the doping ratio of Ce-doped MnO ₂ is 1:10, the conversion rate of formaldehyde is only ~23% at 50°C and the space velocity is 90L/gcat·h ( Appl. Catal. B: Environ., 2017, 211, 212).

Contents of the invention

Based on this, it is necessary to provide a manganese dioxide composite material with high catalytic activity and its preparation method and application.

A manganese dioxide composite material includes nano secondary particles assembled by δ- _MnO2 nanosheets and nano carbon, and the nano secondary particles have a porous structure.

In one of the embodiments, the carbon nanometers are attached to the surface of the δ-MnO ₂ nanosheets.

In one embodiment, manganese vacancies exist in the δ-MnO ₂ nanosheets, and the molar ratio of the manganese vacancies to the Mn element in the δ-MnO ₂ nanosheets is 1:49˜8:42.

In one of the embodiments, the thickness of the δ- _MnO2 nanosheets is 1nm-5nm, the length is 10nm-40nm, the particle size of the nano-carbon is 1nm-10nm, and the particle size of the nano-secondary particles is 30nm ~ 200nm.

In one embodiment, the average pore diameter of the secondary nano particles is 3 nm to 13 nm, and the specific surface area is 100 m ² /g to 240 m ² /g.

In one embodiment, the nanocarbon is graphitized nanocarbon.

In one embodiment, manganese vacancies exist in the δ-MnO ₂ nanosheets, and the molar ratio of the manganese vacancies to Mn in the δ-MnO ₂ nanosheets is 4:46 to 8:42.

In one of the embodiments, the thickness of the δ- _MnO2 nanosheets is 3nm-5nm, the length is 10nm-30nm, the particle size of the graphitized nano-carbon is 2nm-6nm, and the particle size of the nano-secondary particles is The diameter is 30nm ~ 80nm.

In one embodiment, the average pore diameter of the secondary nano particles is 8 nm to 13 nm, and the specific surface area is 180 m ² /g to 240 m ² /g.

A method for preparing a manganese dioxide composite material, comprising: providing permanganate, a saccharide compound and a solvent, wherein the permanganate and the saccharide compound are all dissolved in the solvent; Manganate, the saccharide compound and the solvent are mixed to form a reaction liquid, and the reaction liquid is reacted at 40° C. to 100° C. to obtain the manganese dioxide composite material.

In one embodiment, the carbohydrate compound is at least one of monosaccharides, disaccharides and polysaccharides.

In one embodiment, the carbohydrate compound is a reducing sugar.

In one of the embodiments, the carbohydrate compound is glyceraldehyde, erythrose, thulose, arabinose, ribose, xylose, lyxose, glucose, mannose, fructose, galactose, lactose and maltose at least one of .

In one embodiment, in the reaction solution, the molar ratio of the permanganate to the sugar compound is 2:1 to 20:1.

In one embodiment, the concentration of the permanganate in the reaction solution is 0.01mol/L to 0.15mol/L.

In one of the embodiments, the permanganate includes potassium permanganate, sodium permanganate, calcium permanganate, lithium permanganate, barium permanganate, zinc permanganate and magnesium permanganate At least one, the solvent is water.

An application of the manganese dioxide composite material in removing formaldehyde.

In one embodiment, the manganese dioxide composite material is used to catalyze the oxidative degradation of formaldehyde at room temperature.

The manganese dioxide composite material provided by the invention is a secondary nanoparticle formed by assembling δ- _MnO2 nanosheets and nanocarbons generated substantially simultaneously during the reaction process. The nano-carbon can be attached to the surface of the δ-MnO ₂ nano-sheets and hinder the agglomeration between the δ-MnO ₂ nano-sheets, thereby obtaining porous nano-secondary particles with a larger specific surface area. The secondary nano particles have strong catalytic activity to formaldehyde.

Further, since the presence of the nano-carbon affects the crystallization and growth of the δ- _MnO2 nanosheets, defects and vacancies may exist in the δ- _MnO2 nanosheets, thereby having more active sites, further improving the resistance to formaldehyde. catalytic activity.

Further, when the nanocarbon is graphitized nanocarbon, the δ- _MnO2 nanosheets can have more defects and vacancies, and the degree of agglomeration between the δ- _MnO2 nanosheets is smaller, and the nanometer2 The pore diameter and specific surface area of the secondary particles are larger. In addition, the graphitized structure is conducive to the rapid transfer of electrons in the formaldehyde oxidation process, which can accelerate the catalytic oxidation rate of formaldehyde. Therefore, the catalytic activity of the manganese dioxide composite material is further improved. .

The manganese dioxide composite material provided by the invention can quickly catalyze and degrade formaldehyde at low or normal temperature, has good application prospects, and is prepared by a one-step method, which is simple and easy to operate, has low preparation cost, and is easy to realize industrial production.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) spectrum of the manganese dioxide composite material that the embodiment of the present invention 1 and embodiment 2 provide;

Fig. 2a to Fig. 2d are scanning electron micrograph (SEM), transmission electron micrograph (TEM), high magnification transmission electron micrograph (HR-TEM) and X-ray energy dispersive element distribution of the manganese dioxide composite material provided by Example 1 of the present invention respectively Figure (EDX mapping); Fig. 2e to Fig. 2h are scanning electron micrograph (SEM), transmission electron micrograph (TEM), high magnification transmission electron micrograph (HR-TEM) and X-ray energy dispersive element distribution (EDX mapping);

Fig. 3 is the Fourier transform infrared spectrum (FTIR) figure of the manganese dioxide composite material that the embodiment of the present invention 1 and embodiment 2 provide;

Fig. 4 is the Raman (Raman) spectrum of the manganese dioxide composite material that the embodiment of the present invention 1 and embodiment 2 provide;

Figure 5a and Figure 5b are respectively the cyclic voltammetry curve and the constant current charge and discharge curve of the manganese dioxide composite material provided by Example 1 and Example 2 of the present invention;

Figure 6a and Figure 6b are respectively the H ₂ temperature programmed reduction (H ₂ -TPR) curve and the O ₂ temperature programmed oxidation (O ₂ -TPD) curve of the manganese dioxide composite materials provided in Example 1 and Example 2 of the present invention picture;

Fig. 7a and Fig. 7b are respectively the graph of formaldehyde and carbon dioxide concentration changing with time in the manganese dioxide composite material provided by embodiment 1 and embodiment 2 of the present invention during the formaldehyde static test;

Fig. 8 is the graph that the formaldehyde removal efficiency of the manganese dioxide composite material provided by Example 1 of the present invention changes with time during the formaldehyde dynamic test process;

Fig. 9 is a curve diagram of the formaldehyde removal efficiency of the manganese dioxide composite material provided by Example 1 of the present invention under different relative humidity during the formaldehyde dynamic test process;

Figure 10 is a graph showing the formaldehyde removal efficiency of the manganese dioxide composite material in Example 2 of the present invention as a function of time during the formaldehyde dynamic test;

Figure 11a and Figure 11b are the scanning electron microscope (SEM) and high power transmission electron microscope (HR-TEM) images of the manganese dioxide composite material provided in Example 3 of the present invention, respectively.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail through the following embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

A manganese dioxide composite material includes nano secondary particles assembled by δ- _MnO2 nanosheets and nano carbon, and the nano secondary particles have a porous structure.

The manganese dioxide composite material provided by the invention is a secondary nanoparticle formed by assembling δ- _MnO2 nanosheets and nanocarbons generated substantially simultaneously during the reaction process. The nano-carbon can be attached to the surface of the δ-MnO ₂ nano-sheets and hinder the agglomeration between the δ-MnO ₂ nano-sheets, thereby obtaining porous nano-secondary particles with a larger specific surface area. The secondary nano particles have strong catalytic activity to formaldehyde.

Further, since the presence of the nano-carbon affects the crystallization and growth of the δ- _MnO2 nanosheets, defects and vacancies may exist in the δ- _MnO2 nanosheets, thereby having more active sites, further improving the resistance to formaldehyde. catalytic activity. Preferably, manganese vacancies may exist in the δ-MnO ₂ nanosheets. More preferably, the molar ratio of the manganese vacancies in the δ-MnO ₂ nanosheets to the Mn element in the δ-MnO ₂ nanosheets may be 1:49˜8:42.

The thickness of the δ-MnO ₂ nanosheets may be 1nm-5nm, and the length may be 10nm-40nm. The particle diameter of the nano carbon may be 1nm to 10nm. The particle size of the secondary nano particles may be 30nm-200nm. The average pore diameter of the secondary nano particles is 3 nm to 13 nm, and the specific surface area may be 100 m ² /g to 240 m ² /g.

Preferably, the nano-carbon is graphitized nano-carbon, and the graphitized nano-carbon can make the δ- _MnO2 nanosheets have more defects and vacancies and a smaller size, and make the δ- _MnO2 nanosheets less It is easy to agglomerate, so as to obtain nano secondary particles with larger pore diameter and specific surface area. In addition, the graphitized structure is conducive to the rapid transfer of electrons during the oxidation of formaldehyde, which can accelerate the catalytic oxidation of formaldehyde. Preferably, the molar ratio of the manganese vacancies in the δ-MnO ₂ nanosheets with graphitized nanocarbon to the Mn element in the δ-MnO ₂ nanosheets may be 4:46˜8:42. Preferably, the thickness of the δ-MnO ₂ nanosheets may be 3nm-5nm, and the size may be 10nm-30nm. Preferably, the particle diameter of the nano-carbon may be 1nm to 6nm. The particle size of the secondary nano particles may be 30nm-80nm. The average pore diameter of the secondary nano particles is 8 nm to 13 nm, and the specific surface area may be 180 m ² /g to 240 m ² /g.

The manganese dioxide composite material provided by the invention has high catalytic activity and can rapidly catalyze and degrade formaldehyde at low or normal temperature.

The present invention further provides a preparation method of manganese dioxide composite material, comprising:

S1, providing permanganate, a saccharide compound and a solvent in which both the permanganate and the saccharide compound can be dissolved; and

S2, mixing the permanganate, the saccharide compound and the solvent to form a reaction solution, and reacting the reaction solution at 40°C to 100°C to obtain the manganese dioxide composite material.

In step S1, the permanganate may include at least one of potassium permanganate, sodium permanganate, calcium permanganate, lithium permanganate, barium permanganate, zinc permanganate and magnesium permanganate A sort of. Preferably, the permanganate may be at least one of potassium permanganate, sodium permanganate and calcium permanganate. More preferably, the permanganate may be potassium permanganate.

The saccharide compound may be at least one of monosaccharides, disaccharides and polysaccharides. The monosaccharide may be at least one of glyceraldehyde, erythrose, thulose, arabinose, ribose, xylose, lyxose, glucose, mannose, fructose and galactose. The disaccharide may be at least one of maltose, sucrose and lactose. The polysaccharide can be small molecule glycogen and the like.

The solvent may be water.

In step S2, the step of mixing the permanganate, the saccharide compound and the solvent may include:

S21, dissolving the permanganate in the solvent to form a permanganate solution; and

S22, adding the saccharide compound into the permanganate solution for mixing to obtain the reaction solution.

It can be understood that the permanganate, the saccharide compound and the solvent may also be mixed in other ways, for example, the manganate and the saccharide compound may be added to the solvent at the same time for mixing. Preferably, the permanganate, the saccharide compound and the solvent are mixed quickly before heating to prevent the permanganate and the saccharide compound from reacting before heating.

When the reaction solution is reacted at 40° C. to 100° C., the manganese dioxide crystals obtained by the reduction of the permanganate are obtained to obtain δ-MnO ₂ nanosheets, and at the same time, the saccharides are oxidized to obtain nano-carbons. The nano-carbons On the one hand, it can prevent the growth of δ-MnO ₂ nanosheets, so that the resulting δ-MnO ₂ nanosheets have a smaller size and have more defects and vacancies; on the other hand, the nanocarbon can prevent δ-MnO 2 Agglomeration of _MnO2 nanosheets and self-assembly with the δ- _MnO2 nanosheets to form nanosecondary particles with a porous structure, that is, the synthesis and self-assembly of δ- _MnO2 nanosheets and nanocarbons into nanosecondary The particles are obtained in one step during the heating of the reaction solution. The nanocarbons may be attached to the surface of the δ-MnO ₂ nanosheets. On the one hand, _the nano-secondary particles have a porous structure and a larger specific surface area, which can absorb more formaldehyde; point, the catalytic speed of formaldehyde is accelerated, therefore, the manganese dioxide composite material has high catalytic activity and can degrade formaldehyde quickly and efficiently.

Preferably, the saccharide compound is a reducing sugar, such as a monosaccharide and some reducing disaccharides. When the sugar compound is a reducing sugar, on the one hand, the reducing sugar can form graphitized nano-carbon when being oxidized; on the other hand, the δ- _MnO2 nanosheets have more defects and vacancies, and are smaller , the degree of mutual agglomeration is also smaller, and the pore size and specific surface area of the formed nano secondary particles are larger, so that the catalytic activity of the manganese dioxide composite material and the degradation efficiency of formaldehyde can be further improved.

In the reaction solution, the molar ratio of the carbohydrate compound to the permanganate may be 2:1 to 20:1, more preferably 4:1 to 12:1. The concentration of the permanganate in the reaction solution may be 0.01mol/L to 0.15mol/L, more preferably 0.05mol/L to 0.10mol/L. The reaction time may be 1 min to 12 h. Preferably, the reaction time is from 1 min to 360 min.

After the reaction is completed to obtain the manganese dioxide composite material, the steps of separating, washing and drying the manganese dioxide composite material may be further included. The manganese dioxide composite material can be separated by filtration, centrifugation and the like. The drying temperature of the manganese dioxide composite material may be less than 300° C., so as to prevent crystal forms of manganese dioxide and nano-graphite carbon from changing. After the drying step, the step of grinding the manganese dioxide composite material may be further included.

The preparation method provided by the invention can obtain the manganese dioxide composite material in one step, is simple and easy to operate, and has low preparation cost.

The invention also provides an application of the manganese dioxide composite material in removing formaldehyde. The manganese dioxide composite material can be used as a catalyst to quickly oxidize and degrade formaldehyde at low temperature/room temperature, and has a high conversion rate to formaldehyde. The oxidative degradation mechanism of described formaldehyde is as follows:

It can be understood that the manganese dioxide composite material can be used not only to catalyze the oxidative degradation of formaldehyde, but also to catalyze other redox reactions or ion exchange reactions.

Example 1:

Weigh 1.2g of potassium permanganate and dissolve it in an Erlenmeyer flask containing 100mL of water, then weigh 0.18g of glucose and add it to the above solution, and place the Erlenmeyer flask containing the reaction solution in a water bath at 80°C for 15 minutes to react. After the reaction, the solid in the Erlenmeyer flask was washed by centrifugation, dried at 105° C. for 12 hours, and then ground to obtain a manganese dioxide composite material powder (GLC-MnO ₂ ).

The performance of the GLC- _MnO2 was characterized, and the results are shown in Figures 1 to 6 and Table 1.

Static degradation test of formaldehyde:

Take by weighing GLC-MnO _100mg , place in the plexiglass reactor of 3.5L, and described catalyst is sealed with airtight lid, pour into a certain amount of formaldehyde in the plexiglass reactor, make the formaldehyde concentration after equilibrium be about 200ppm. Open the sealing cover, make the catalyst and formaldehyde contact with each other, record the change of formaldehyde concentration and carbon dioxide concentration with time, the results are shown in Figure 7.

Dynamic degradation test of formaldehyde:

Weigh 100 mg of GLC-MnO ₂ , fill it into a glass tube with an inner diameter of 6 mm, and control the relative humidity of the reaction gas by adjusting the different gas distribution ratios of the dry and wet gas paths, so that the relative humidity of the reaction gas is 55%. The initial concentration of formaldehyde is controlled by controlling the flow rate of formaldehyde, so that the initial concentration is 0.5-1.0mg/m ³ , and the concentration of formaldehyde at the inlet and outlet is measured by the phenol reagent in the national standard. The curve of formaldehyde removal efficiency with time is shown in Figure 8 As shown; keep the initial concentration of formaldehyde at 0.5mg/m ³ , respectively control the relative humidity of the reaction gas at 1% to 100%, test the concentration of formaldehyde at the inlet and outlet, and the curve of formaldehyde removal efficiency with time is shown in Figure 9 .

As shown in Figure 1, the 12.3 °, 24.6 °, 36.5 ° and 65.5 ° peaks of the XRD spectrum of the manganese dioxide composite material powder of embodiment 1 correspond to δ- _MnO crystal faces (001), (002), (100) and (110). As shown in Figure 2a, the manganese dioxide composite material is nano secondary particles with a particle size of 30nm to 80nm, and the nano secondary particles include a plurality of MnO ₂ nanosheet structures. As shown in Figure 2b, the secondary nanoparticle has an obvious porous structure with an average pore diameter of 5nm and a measured specific surface area of 216m ² /g. Further observe its microstructure, as shown in Figure 2c, the manganese dioxide composite material has fine lattice fringes, wherein the fringe spacing of 0.24nm corresponds to the crystal plane (110) of δ- _MnO2 , and the fringe spacing of 0.21nm The spacing corresponds to the crystal plane (110) of graphite, that is, graphitized nanocarbon is attached to the surface of the MnO ₂ nanosheet, and the particle size of the graphitized nanocarbon shown is 2nm to 6nm. As shown in Figure 2d, the manganese dioxide composite material contains C, Mn, O and K, and the C element is the same as the Mn element, O element and K element, and has a relatively uniform for the distribution. From the above analysis results, it can be seen that in the above reaction process, while potassium permanganate converts manganese dioxide, glucose is converted into graphitized nano-carbon particles in situ, and the graphitized nano-carbon rice particles and manganese dioxide nanosheets Co-assembled to form secondary nano-particles with a porous structure.

It can be seen from Table 1 that the Mn/O ratio of 0.44 in the manganese dioxide composite material is less than the stoichiometric Mn/O ratio of 0.5 in _MnO2 , indicating that there are vacancies in the manganese dioxide crystals, and the vacancies of manganese are easier to generate Unsaturated oxygen species, and the existence of K ⁺ for charge balance in manganese vacancies is also more conducive to the generation of active oxygen, and the manganese dioxide composite also contains 0.20 surface adsorbed oxygen, these unsaturated oxygen species and The surface adsorbed oxygen plays an important role in the catalysis of formaldehyde, which makes the manganese dioxide composite material have higher catalytic activity to formaldehyde.

As shown in Figure 7, the static formaldehyde degradation test results show that after 1 hour of reaction, the formaldehyde removal rate of the manganese dioxide composite material at room temperature reaches 93.5%. As shown in Figure 8, the dynamic formaldehyde degradation test results show that when the relative humidity is 55%, the removal rate of low-concentration formaldehyde of the manganese dioxide composite material at room temperature reaches more than 90%, and remains stable within 10 hours, and Manganese dioxide composites still have a high removal rate for low-concentration formaldehyde at room temperature and high humidity. As shown in Figure 9, in the relative humidity range of 4% to 80%, the manganese dioxide composite material has a high removal rate for low-concentration formaldehyde at room temperature.

Example 2

Weigh 1.2g of potassium permanganate and dissolve it in an Erlenmeyer flask containing 100mL of water, then weigh 0.34g of sucrose and add it to the above solution, and place the Erlenmeyer flask containing the reaction solution in a water bath at 80°C for 15min. After the reaction, the solid in the Erlenmeyer flask was washed by centrifugation, dried at 105° C. for 12 hours, and then ground to obtain a manganese dioxide composite material powder (AC-MnO ₂ ).

The performance of the AC-MnO ₂ was characterized, and the results are shown in Figures 1 to 6 and Table 1.

The static degradation test of formaldehyde was carried out by the same method as in Example 1, and the results are shown in Figure 7.

Using the same method as in Example 1, the dynamic degradation test of formaldehyde was carried out under the condition of a relative humidity of 55% and an initial formaldehyde concentration of 1.0 mg/m ³ , and the results are shown in FIG. 10 .

The 12.3 °, 24.6 °, 36.5 ° and 65.5 ° peaks of the XRD spectrum of the manganese dioxide composite material powder of embodiment 2 correspond to δ- _MnO crystal faces (001), (002), (100) and (110 ). As shown in FIG. 2e, the manganese dioxide composite material is nano secondary particles with a particle size of 150 nm to 200 nm, and the nano secondary particles include a plurality of MnO ₂ nano sheet structures. As shown in Figure 2f, the secondary nanoparticle has a porous structure with an average pore diameter of 9 nm and a measured specific surface area of 70.3 m ² /g. Further observe its microstructure, as shown in Figure 2g, the lattice fringes of the manganese dioxide composite material only have the 0.24nm fringe spacing corresponding to the crystal plane (110) of δ- _{MnO 2} Shaped nano-carbon, the particle size of amorphous nano-carbon is 5nm to 10nm. As shown in FIG. 2h , the C element in the manganese dioxide composite material is the same as the Mn element, O element and K element, and has a relatively uniform distribution in the manganese dioxide composite material. From the above analysis results, it can be seen that in the above reaction process, while potassium permanganate is converted into manganese dioxide, sucrose is converted into amorphous nano-carbon particles, and the nano-carbon rice particles and manganese dioxide nanosheets are assembled together to form a porous structure. Structured nanosecondary particles.

It can be seen from Table 1 that the Mn/O ratio of 0.48 in the manganese dioxide composite material is less than the stoichiometric Mn/O ratio of 0.5 in _MnO2 , indicating that there are vacancies in the manganese dioxide crystals, and the vacancies of manganese are easier to generate Unsaturated oxygen species, and the existence of K ⁺ for charge balance in manganese vacancies is also more conducive to the generation of active oxygen, and the manganese dioxide composite also contains 0.15 surface adsorbed oxygen, these unsaturated oxygen species and The surface adsorbed oxygen plays an important role in the catalysis of formaldehyde, which makes the manganese dioxide composite material have higher catalytic activity to formaldehyde.

As shown in Figure 7, the static formaldehyde degradation test results show that after 1 hour of reaction, the formaldehyde removal rate of the manganese dioxide composite material at room temperature reaches 83.4%.

As shown in Figure 10, when the relative humidity is 55%, the formaldehyde removal rate of 1.0mg/ ^m3 of the manganese dioxide composite material at room temperature reaches 89.4%, and remains stable within 10h.

Example 3

Weigh 1.2g of potassium permanganate and dissolve it in an Erlenmeyer flask containing 100mL of water, then weigh 0.18g of fructose and add it to the above solution, and place the Erlenmeyer flask containing the reaction solution in a 40°C water bath for 15min. After the reaction, the solid in the Erlenmeyer flask was centrifugally washed, dried at 105° C. for 12 hours, and then ground to obtain a manganese dioxide composite material powder. After testing, the manganese dioxide composite material is a nano-secondary particle assembled from δ-MnO ₂ nanosheets and graphitized nano-carbon, the specific surface area of the manganese dioxide composite material is 230m ² /g, and the pore volume is 0.3 cm ³ /g, and the pore size is 5.2nm.

Example 4

Weigh 1.2g of potassium permanganate and dissolve it in an Erlenmeyer flask containing 100mL of water, then weigh 0.18g of lactose and add it to the above solution, and place the Erlenmeyer flask containing the reaction solution in a 95°C water bath for 360min. After the reaction, the solid in the Erlenmeyer flask was centrifugally washed, dried at 105° C. for 12 hours, and then ground to obtain a manganese dioxide composite material powder. After testing, the manganese dioxide composite material is nano secondary particles assembled from δ-MnO ₂ nanosheets and graphitized nano carbon.

Comparative example 1

Using the same method as in Example 1, the static and dynamic degradation experiments of formaldehyde were carried out on the layered manganese dioxide. Static formaldehyde degradation test results show that after 1 hour of reaction, the formaldehyde removal rate of layered manganese dioxide at room temperature is 55%. The dynamic formaldehyde degradation test results show that when the relative humidity is 55%, the removal rate of the low concentration of 1.0mg/m ³ formaldehyde at room temperature by layered manganese dioxide is 80%.

Comparative example 2

Comparative Example 1 is basically the same as Example 1, except that the reaction solution is reacted at normal temperature. After testing, the obtained product only includes manganese dioxide and does not include nano-carbon. The specific surface area of the product is 72.4m ² /g, the pore volume is 0.78cm ³ /g, and the pore size is 4.4nm.

XPS (X-ray Photoelectron Spectroscopy) and ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) analysis results of the manganese dioxide composite material of Table 1 Example 1 and Example 2

Remarks: superscript a represents data obtained from XPS analysis; superscript b represents data obtained from ICP-AES analysis; O _α represents O in Mn-O, O _β represents surface-adsorbed O, O _γ represents carbon-related O in water and O in water; AOS is the average oxidation state of Mn.

The manganese dioxide composite material provided by the invention has a better catalytic effect on formaldehyde degradation at room temperature, and has great application potential in actually degrading formaldehyde in indoor air. In addition, compared with AC-MnO ₂ , GLC-MnO ₂ has more electroactive sites, higher electroactivity, higher conductivity, more chemisorbed oxygen and more manganese vacancies, It is more conducive to the catalysis of formaldehyde, and GLC-MnO ₂ has smaller particle size and larger pore size and specific surface area, which can expose more active reaction sites, and the catalytic performance and removal efficiency of formaldehyde are higher.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (18)

1. a kind of manganese dioxide composite material, including by δ-MnO₂The nanometer second particle that nanometer sheet and nano-sized carbon assemble, institute Stating nanometer second particle has porous structure.

2. manganese dioxide composite material according to claim 1, which is characterized in that the nano-sized carbon is attached to the δ- MnO₂The surface of nanometer sheet.

3. manganese dioxide composite material according to claim 1, which is characterized in that the δ-MnO₂There are manganese in nanometer sheet Vacancy, the vacancy of the manganese and the δ-MnO₂The molar ratio of Mn elements is 1 in nanometer sheet:49~8:42.

4. manganese dioxide composite material according to claim 1, which is characterized in that the δ-MnO₂The thickness of nanometer sheet is 1nm~5nm, length are 10nm~40nm, and the grain size of the nano-sized carbon is 1nm to 10nm, the grain size of the nanometer second particle For 30nm~200nm.

5. manganese dioxide composite material according to claim 1, which is characterized in that the average hole of the nanometer second particle Diameter is 3nm~13nm, specific surface area 100m²/ g~240m²/g。

6. manganese dioxide composite material according to claim 1, which is characterized in that the nano-sized carbon is graphitization nano Carbon.

7. manganese dioxide composite material according to claim 6, which is characterized in that the δ-MnO₂There are manganese in nanometer sheet Vacancy, the vacancy of the manganese and the δ-MnO₂The molar ratio of Mn is 4 in nanometer sheet:46 to 8:42.

8. manganese dioxide composite material according to claim 6, which is characterized in that the δ-MnO₂The thickness of nanometer sheet is 3nm~5nm, length are 10nm~30nm, and the grain size of the graphitization nano carbon is 2nm to 6nm, the nanometer second particle Grain size is 30nm~80nm.

9. manganese dioxide composite material according to claim 6, which is characterized in that the average hole of the nanometer second particle Diameter is 8nm to 13nm, specific surface area 180m²/ g~240m²/g。

10. a kind of preparation method of manganese dioxide composite material, which is characterized in that including：

Permanganate, saccharide compound and solvent, the permanganate and the saccharide compound are provided and are dissolved in the solvent In；And

Reaction solution is formed after the permanganate, the saccharide compound and the solvent are mixed, and the reaction solution is made to exist 40 DEG C to 100 DEG C are reacted, and the manganese dioxide composite material is obtained.

11. the preparation method of manganese dioxide composite material according to claim 10, which is characterized in that the carbohydrate chemical combination Object is at least one of monosaccharide and disaccharide and polysaccharide.

12. the preparation method of manganese dioxide composite material according to claim 11, which is characterized in that the carbohydrate chemical combination Object is reducing sugar.

13. the preparation method of manganese dioxide composite material according to claim 12, which is characterized in that the carbohydrate chemical combination Object be glyceraldehyde, erythrose, Su Li sugar, arabinose, ribose, xylose, lyxose, glucose, mannose, fructose, galactolipin, At least one of lactose and maltose.

14. the preparation method of manganese dioxide composite material according to claim 10, which is characterized in that in the reaction solution In, the molar ratio of the permanganate and the saccharide compound is 2:1 to 20:1.

15. the preparation method of manganese dioxide composite material according to claim 10, which is characterized in that the permanganate A concentration of 0.01mol/L to 0.15mol/L in the reaction solution.

16. the preparation method of manganese dioxide composite material according to claim 10, which is characterized in that the permanganate Including at least one in potassium permanganate, sodium permanganate, acerdol, high manganese lithium, barium permanganate, zinc permanganate and magnesium permanganate Kind, the solvent is water.

17. a kind of application of manganese dioxide composite material as described in any one of claim 1 to 9 in removing formaldehyde.

18. application of the manganese dioxide composite material according to claim 17 in removing formaldehyde, which is characterized in that described Manganese dioxide composite material is for catalysis oxidation of formaldehyde degradation at room temperature.