Alpha-type manganese dioxide with pore channels filled with hydrogen ions and preparation method thereof
Technical Field
The invention belongs to the field of inorganic nano material synthesis, and particularly relates to alpha-manganese dioxide (alpha-MnO) with hydrogen ions filling pore channels2) And a method for preparing the same.
Background
Among the many common manganese oxides, manganese dioxide (MnO)2) The crystal form is the most complex structure and the most crystal form. MnO2Is manganese oxygen octahedron [ MnO ]6]The structure unit is one of Mn in the center of octahedron and 6O in the vertex angle of the octahedron, and octahedron chains are formed between the octahedrons in a co-edge mode and form different crystal structures in an edge/vertex combination mode. Manganese dioxide of different crystal forms, such as alpha-MnO, can be formed according to different manganese-oxygen octahedral connection modes2,β-MnO2,γ-MnO2,δ-MnO2And the like. Wherein, alpha-MnO2The manganese dioxide has better activity than other crystal manganese dioxide in the fields of environmental catalysis (such as VOCs catalytic combustion and DeNOx), electrochemistry (such as ORR and OER) and the like.
α-MnO2Has a 2 × 2 pore channel structure, pore channel size of 0.46nm, and cation (K) in the pore channel+、Na+、NH4 +、Ba2+Etc.) to maintain the cell structure. alpha-MnO2The preparation method can influence the species and distribution of the cations in the pore channels, and further influence the activity of the material in different application fields. Common preparation methods, such as low-temperature liquid phase method, hydrothermal method, sol-gel method, reflux method and the like, for preparing alpha-MnO2Generally all have K+、Na+、NH4 +Etc. basic cations fill the pores. These cations may mask the acid sites of the material, allowing alpha-MnO2The use of acid sites as reactive sites is limited. The existing alpha-MnO for filling the pore channel with hydrogen ions2All reports are based on the use of NH4 +alpha-MnO for filling pore channel2Obtained by calcination, but the prior experiments can not prove NH4 +The ions are completely removed. Therefore, in order to avoid the interference of other alkaline cations, the alpha-MnO of a hydrogen ion filled pore channel is researched2The preparation method has very important significance.
Disclosure of Invention
In order to overcome the disadvantages of the prior art andthe invention aims to provide alpha-manganese dioxide (alpha-MnO) with hydrogen ions filling pore channels2) The preparation method of (1). Firstly preparing amorphous manganese oxide precursor by low-temperature liquid phase method, and then further converting the amorphous manganese oxide precursor into alpha-MnO of hydrogen ion filled pore channel under the condition of strong acid2The preparation method is simple and convenient to control.
The invention also aims to provide alpha-manganese dioxide (alpha-MnO) with hydrogen ions filling the pore channels, which is prepared by the preparation method2)。
The purpose of the invention is realized by the following technical scheme:
a preparation method of alpha-type manganese dioxide with hydrogen ion filled pore channels comprises the following steps:
s1, preparing amorphous manganese oxide: completely dissolving manganese salt in pure water, then adding a permanganate solution, standing at room temperature after ultrasonic oscillation, carrying out suction filtration, washing and drying to obtain amorphous manganese oxide;
s2, preparing alpha-MnO of hydrogen ion filling pore channel2: and (4) adding and dispersing the amorphous manganese oxide obtained in the step (S1) into an aqueous solution, adding concentrated sulfuric acid, carrying out ultrasonic oscillation and uniform dispersion, standing for reaction, carrying out suction filtration, washing and drying to obtain the alpha-manganese dioxide with hydrogen ion filled pore channels.
Preferably, the manganese salt in step S1 is manganese sulfate monohydrate; the mass ratio of the manganese salt to the pure water is 1: 50-1: 30.
Preferably, the permanganate solution in step S1 is a 40 wt.% sodium permanganate solution, and the mass ratio of the sodium permanganate solution to pure water is 1: 30-1: 20.
Preferably, the molar ratio of the manganese salt to the permanganate in the permanganate solution described in step S1 is 3:2 or less.
Preferably, the standing time at room temperature in the step S1 is 12-24 h.
Preferably, the mass ratio of the amorphous manganese oxide to the aqueous solution in the step S2 is 1:200 to 1: 300.
Preferably, the volume ratio of the concentrated sulfuric acid to the aqueous solution in the step S2 is 1: 10-1: 5.
Preferably, the temperature of the standing reaction in the step S2 is 60-90 ℃, and the time is 8-24 h.
The alpha-type manganese dioxide with hydrogen ions filling the pore channels is prepared by the preparation method.
The principle of the invention is as follows:
common preparation methods, such as low-temperature liquid phase method, hydrothermal method, sol-gel method, reflux method and the like, for preparing alpha-MnO2Generally all have K+、Na+、NH4 +Equibasic cations fill the pores, which may mask the acidic sites of the material, so that α -MnO2The use of acid sites as reactive sites is limited. The invention provides alpha-MnO of hydrogen ion filling pore channel2The preparation method can effectively avoid the interference of other alkaline cations and can be used for alpha-MnO2The application field has great extension significance.
Compared with the prior art, the invention has the following advantages and effects:
the preparation method provided by the invention is simple and convenient to control, and can be used for industrial scale-up production, and the prepared alpha-MnO of the hydrogen ion filling pore channel2Can effectively avoid the interference of other alkaline cations to alpha-MnO2The application field has great extension significance.
Drawings
FIG. 1 is an X-ray diffraction pattern of catalysts prepared in example 1 of the present invention and comparative example 1.
FIG. 2 is a scanning electron micrograph of a catalyst prepared in example 1 of the present invention.
Detailed Description
The invention is further illustrated by the following examples. These examples are intended to illustrate the invention and are not intended to limit the scope of the invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like. Any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.
Example 1
alpha-MnO of hydrogen ion filling pore channel2The preparation method comprises the following steps:
s1, preparing amorphous manganese oxide: adding 3mmol of MnSO4Completely dissolving the manganese oxide into 50mL of distilled water solution, adding 2mmol of 40 wt.% sodium permanganate water solution, carrying out ultrasonic oscillation for 5 minutes, standing at room temperature for 24 hours to obtain black precipitate, carrying out suction filtration and washing until filtrate is transparent, and drying to obtain amorphous manganese oxide;
s2, preparing alpha-MnO of hydrogen ion filling pore channel2: adding 0.5g of amorphous manganese oxide obtained from S1 into 50mL of distilled water solution, then adding 6mL of concentrated sulfuric acid, ultrasonically oscillating for 5 minutes to uniformly disperse, standing at 80 ℃ for reaction for 24 hours, and then filtering, washing and drying to obtain alpha-MnO of the hydrogen ion filled pore channel2。
We then synthesized α -MnO for step S2 above2The test characterization is carried out, and the XRD diffraction pattern is shown in figure 1. From the figure, the manganese oxide prepared and the alpha-MnO indicated by JCPDF Standard card PDF #44-0141 are known2Correspondingly, no other miscellaneous peak exists, which indicates that the alpha-MnO with the pure phase 2x2 structure is synthesized2And no K is used in the present invention+、Na+And NH4 +And alkaline cations, which indicates that only hydronium ions may exist in the pore channels. And the diffraction peak position of the whole body is shifted to a low angle by 0.9 degrees, which shows that the pore channels are enlarged when the pore channels only contain hydronium ions. alpha-MnO prepared from this example2The alpha-MnO can be seen in the scanning electron micrograph (FIG. 2)2The nano-rod has the shape of a nano-rod with the diameter of 20nm and the length of about 200 nm.
Example 2
alpha-MnO of hydrogen ion filling pore channel2The preparation method comprises the following steps:
s1, preparing amorphous manganese oxide: adding 3mmol of MnSO4Completely dissolved in 50mL of distilled water, followed by addition of 3mmol of 40 wt.% aqueous sodium permanganate solution and sonicationShaking for 5 minutes, standing for 24 hours at room temperature to obtain black precipitate, and then performing suction filtration and washing until filtrate is transparent and dried to obtain amorphous manganese oxide;
s2, preparing alpha-MnO of hydrogen ion filling pore channel2: adding 0.5g of amorphous manganese oxide obtained from S1 into 50mL of distilled water solution, then adding 10mL of concentrated sulfuric acid, ultrasonically oscillating for 5 minutes to uniformly disperse, standing at 90 ℃ for reaction for 8 hours, and then filtering, washing and drying to obtain alpha-MnO of the hydrogen ion filled pore channel2。
Example 3
alpha-MnO of hydrogen ion filling pore channel2The preparation method comprises the following steps:
s1, preparing amorphous manganese oxide: adding 3mmol of MnSO4Completely dissolving the manganese oxide into 50mL of distilled water solution, adding 2mmol of 40 wt.% sodium permanganate water solution, carrying out ultrasonic oscillation for 5 minutes, standing at room temperature for 24 hours to obtain black precipitate, carrying out suction filtration and washing until filtrate is transparent, and drying to obtain amorphous manganese oxide;
s2, preparing alpha-MnO of hydrogen ion filling pore channel2: adding 0.5g of amorphous manganese oxide obtained from S1 into 50mL of distilled water solution, then adding 8mL of concentrated sulfuric acid, ultrasonically oscillating for 5 minutes to uniformly disperse, standing at 65 ℃ for reacting for 18 hours, and then filtering, washing and drying to obtain alpha-MnO of the hydrogen ion filled pore channel2。
Comparative example 1
MnO (MnO)2The preparation method comprises the following steps:
s1, preparing amorphous manganese oxide: adding 3mmol of MnSO4Completely dissolving the manganese oxide into 50mL of distilled water solution, adding 2mmol of 40 wt.% sodium permanganate water solution, carrying out ultrasonic oscillation for 5 minutes, standing at room temperature for 24 hours to obtain black precipitate, carrying out suction filtration and washing until filtrate is transparent, and drying to obtain amorphous manganese oxide;
s2, preparing alpha-MnO of hydrogen ion filling pore channel2: adding and dispersing 0.5g of amorphous manganese oxide obtained in S1 into 50mL of distilled water solution, then adding 1mL of concentrated sulfuric acid, ultrasonically oscillating for 5 minutes to uniformly disperse, standing at 80 ℃ for reaction for 24 hours, and then carrying out suction filtration, washing and drying to obtain MnO2。
The XRD diffractogram of the product of this comparative example is shown in FIG. 1, which shows that the manganese oxide prepared is gamma-MnO indicated by JCPDF Standard card PDF #14-06152Correspondingly, it is shown that alpha-MnO cannot be generated under the condition of non-strong acid2。
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.