CN113161562A

CN113161562A - Defective P3 manganese oxide electro-catalytic material and electro-catalyst

Info

Publication number: CN113161562A
Application number: CN202110544507.3A
Authority: CN
Inventors: 马吉伟; 钟雪鹏; 黄云辉
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-05-20
Filing date: 2021-05-19
Publication date: 2021-07-23
Anticipated expiration: 2041-05-19
Also published as: CN111640955A; CN113161562B

Abstract

The invention provides a defective P3 manganese oxide electrocatalyst, belonging to the field of inorganic materials. The chemical formula of the defect type P3 manganese oxide electrocatalyst provided by the invention is as follows: h_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11. The invention provides an electrocatalyst made of H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Grinding and mixing with carbon powder. The preparation method is simple and efficient, has mild reaction conditions, is easy to popularize and apply, can provide larger active surface area and more active sites for the contact of the electrolyte and the catalyst, can effectively improve the oxygen reduction activity of the catalyst, can also improve the stability of a layered structure, and can prevent the circulation of the electrolyteThe layered structure is destroyed during the looping process. Meanwhile, oxygen vacancies generated in the acid etching process and the reduced interlayer spacing can be catalyzed cooperatively, so that the oxygen reduction performance of the material is improved.

Description

Defective P3 manganese oxide electro-catalytic material and electro-catalyst

Technical Field

The invention relates to a defective P3 manganese oxide electro-catalytic material and an electro-catalyst, belonging to the field of inorganic materials.

Background

With the exacerbation of fossil energy crisis and the worsening of ecological environment, the demand of human beings for clean energy storage systems is increasing, and the development and application of new energy conversion and storage systems are important challenges facing the sustainable and healthy development of society. The fuel cell is a clean and efficient hydrogen energy power generation mode, is not limited by Carnot cycle, has high energy conversion efficiency, and can directly convert chemical energy into electric energy. The metal-air battery has high theoretical energy density and great development potential. Both of these two types of batteries with broad prospects for development will undergo oxygen reduction reactions.

The oxygen reduction reaction is an electrochemical process in which oxygen is reduced to hydroxide (alkaline medium) or water (acidic medium) on the cathode surface. Oxygen reduction reactions play a key role in various energy storage and conversion technologies. The reaction kinetics of the process is slow, and the reaction process is complex. At present, the cathode oxygen reduction catalyst is mainly a platinum noble metal catalyst. However, the large-scale application of fuel cells, metal-air cells and the like is severely restricted by the characteristics of scarce platinum reserves, high price, easy poisoning and the like. Therefore, the research for developing the non-noble metal catalyst with high activity, high stability and low cost is very important for the field of electrochemical catalysis.

Manganese oxide is widely concerned by researchers because of the advantages of high abundance of elements, small influence on environment, low cost and the like. Among the various crystal structures of manganese dioxide, layered manganese dioxide has been widely studied because its unique layered structure provides a highly efficient transport path for oxygen reduction reactions. Compared with noble metal catalysts, manganese oxides have limited electronic conductivity and lower oxygen reduction activity, mainly reflected in the overpotential and the ability to catalyze four-electron reduction. Many methods for improving the electrocatalytic activity of manganese oxides have been proposed, such as controlling the nanostructure of manganese oxides, multi-step synthesis increasing active sites, etc., and although these methods are effective, they require complicated synthetic steps or lack long-term stability in air. Therefore, it is necessary to develop a simple method for improving the oxygen reduction activity of manganese oxide.

By utilizing structural transformation to construct a high-performance defective P3 manganese oxide, compared with a precursor, the electro-catalytic material after structural transformation has better electrochemical performance. However, in the field of electrocatalysis, such methods for stabilizing the material structure and changing the intrinsic catalytic activity thereof through structural transformation are rarely reported.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide an oxygen-deficient electrocatalytic material which is simple, efficient, and excellent in universality, and an electrocatalyst containing the electrocatalytic material.

The invention provides a defective P3 manganese oxide electrocatalytic material, which is characterized by the following chemical formula: h_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11□ represents an atomic defect, (abbreviated as HLM).

The defect type P3 manganese oxide electrocatalytic material provided by the invention also has the characteristics that the preparation method comprises the following steps: step 1, stirring and mixing lithium hydroxide and manganese carbonate, and then placing the mixture in a muffle furnace to react for 36-48 h at 400-500 ℃ to obtain layered lithium manganate; step 2, dispersing the layered lithium manganate in a sulfuric acid solution with the concentration of 2M-3M, stirring for 6H-24H at room temperature, washing and drying to obtain H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11。

The defective P3 manganese oxide electrocatalytic material provided by the invention can also be characterized in that the molar ratio of lithium hydroxide to manganese carbonate is (1.8-2.5):1, and preferably 2.05: 1.

The defective P3 manganese oxide electrocatalytic material provided by the present invention may further have a feature that the sintering gas in the muffle furnace in step 1 is air.

The defective P3 manganese oxide electrocatalytic material provided by the invention can also have the characteristic that the sintering temperature in a muffle furnace in the step 1 is 450 ℃.

The deficient P3 manganese oxide electrocatalytic material provided by the invention can also have a characteristic that the concentration of sulfuric acid solution in step 2 is 2.5M.

The defective P3 manganese oxide electrocatalytic material provided by the invention can also have the characteristic that the stirring time at room temperature in the step 2 is 12 h.

The invention also provides an electrocatalyst, characterized by the formula_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Grinding and mixing with carbon powder.

In the electrocatalyst provided by the invention, there may also be provided a feature wherein H is_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The mass ratio of the carbon powder to the carbon powder is 10 percent to 90 percent to 30 percent to 70 percent.

The electrocatalyst provided by the invention can also have the characteristic that the model of the carbon powder is VulcanXC-72R.

Action and Effect of the invention

According to the defect type P3 manganese oxide electro-catalytic material, the layered O3 type lithium manganate (Li) with mature process and good thermal stability is selected₂MnO₃) As a precursor, the non-noble metal cathode catalyst with high oxygen reduction activity is prepared by simple acid etching, so the method has the advantages of simple and efficient preparation method, mild reaction conditions, easy popularization and application and the like.

The defect P3 manganese oxide electrocatalytic material is related to because of the defect P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The catalyst has larger specific surface area, so that larger active surface area and more active sites can be provided for the contact of the electrolyte and the catalyst, and the oxygen reduction activity of the catalyst can be effectively improved.

According to the defective P3 manganese oxide electrocatalytic material of the present invention, the lithium is present in the transition metal layer, so that the stability of the layered structure can be improved, and the layered structure can be prevented from being damaged during the cycle. Meanwhile, oxygen vacancies generated in the acid etching process and the reduced interlayer spacing can be catalyzed cooperatively, so that the oxygen reduction performance of the material is improved.

Drawings

FIG. 1 is a schematic structural diagram of a layered lithium manganate precursor of O3 type according to example 1 of the present invention;

FIG. 2 is a schematic structural diagram of a deficient P3 manganese oxide catalytic material in example 1 of the present invention;

FIG. 3 shows example 1 of the present invention (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) And comparative example 2 (Li)₂MnO₃) X-ray diffractometer (XRD) to resemble HCrO form P3₂Is used as a control;

FIG. 4 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The neutron powder diffraction spectrum and the simulation spectrum of (1);

FIG. 5 comparative example 1 (Birnessite-typeMnO)₂) An X-ray diffractometer plot;

FIG. 6 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) Comparison example 1 (Birnessite-typeMnO)₂) Comparative example 2 (Li)₂MnO₃) A graph of oxygen reduction performance for the corresponding samples;

FIG. 7 shows example 1 (defective type)P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) Comparison example 1 (Birnessite-typeMnO)₂) Comparative example 2 (Li)₂MnO₃) A graph of the percentage of hydrogen peroxide and the number of transferred electrons;

FIG. 8 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) The prepared catalyst is in a stability chart after 10000 cycles of cyclic voltammetry at the sweep rate of 100 mV/s; and

FIG. 9 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) Assembled into a performance map of a microfluidic fuel cell.

Detailed Description

In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the invention is specifically described below by combining the embodiment and the attached drawings.

< example 1>

The embodiment provides a defective P3 manganese oxide electrocatalytic material, and the preparation method comprises the following steps:

step 1, putting 3g of manganese carbonate and 1.28g of anhydrous lithium hydroxide into an agate mortar for grinding, uniformly mixing, putting into a planetary ball milling tank for ball milling at 400rpm for 12 hours, putting the obtained uniform powder into a muffle furnace after ball milling, and reacting at 450 ℃ for 40 hours to obtain reddish brown powder, namely O3 type layered lithium manganate precursor (Li 3 type layered lithium manganate precursor)₂MnO₃) The structural formula is shown in figure 1;

step 2, preparing 2.5M sulfuric acid solution, and adding 100mg of O3-type layered lithium manganate precursor (Li)₂MnO₃) Dissolving in 10ml of 2.5M sulfuric acid solution, stirring with magneton at room temperature for 12 hr, centrifuging, washing with ultrapure water and ethanol four times, and drying in vacuum drying oven to obtain defective P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Which isThe structural formula is shown in figure 2.

FIG. 4 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) Neutron powder diffraction pattern and fitting pattern.

The data in fig. 4 are refined to verify that Li exists in the transition metal layer and oxygen defects are introduced, so that the construction of the lithium/manganese mixed material structure of the transition metal layer is verified.

< comparative example 1>

The preparation method of the Birnessite-type layered manganese dioxide in the comparative example 1 is as follows:

dissolving 10mmol of potassium permanganate in 65ml of deionized water, stirring with a magneton for 20 minutes to obtain a uniform mauve solution, transferring the solution to a reaction kettle with a Teflon lining, reacting for 48 hours at 220 ℃, after the solution is cooled, centrifugally washing a product with ultrapure water and ethanol for four times, placing the product in a vacuum drying box, and drying to obtain the Birnessite-type layered manganese dioxide.

< comparative example 2>

The comparative example 2 provides O3 type layered lithium manganate, and the preparation method is as follows:

putting 3g of manganese carbonate and 1.28g of anhydrous lithium hydroxide into an agate mortar for grinding, uniformly mixing, putting into a planetary ball milling tank for ball milling at 400rpm for 12 hours, putting the obtained uniform powder into a muffle furnace after ball milling, and reacting for 40 hours at 450 ℃ to obtain reddish brown powder, namely O3 type layered lithium manganate (Li 3 type layered lithium manganate)₂MnO₃)。

< test example 1>

Characterization by X-ray diffraction

The compounds obtained in example 1 and comparative examples 1 to 2 were subjected to X-ray diffraction. The characterization results are shown in FIGS. 3-5.

FIG. 3 shows an example of the present invention, example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) And comparative example 2 (Li)₂MnO₃) X-ray diffractometer (XRD),in the form of HCrO like P3₂As a control.

As shown in fig. 3, compared to comparative example 2 (Li)₂MnO₃) Defective P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11After acid treatment, the phase transition occurs and simultaneously the HCrO of P3 type₂The structure is similar.

FIG. 4 shows example 1 of the present invention (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11) Neutron powder diffraction experimental spectrum and simulation spectrum.

As shown in FIG. 4, the deficient type P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The structure of (2) is refined by the Rietveld method (Rietveld,1969), but the defect type P3H is obtained after the refinement_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The space group is still C2/m. The refined result shows that atoms Li, H and Mn share the special position of the transition metal layer in the crystallography model, the occupancy rates of Li, H and Mn are respectively 17%, 13% and 67%, and the final chemical formula of the material is H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Deletion of 0.11O^2-. The coincidence between the experimental map and the calculation map after the structure is refined is good.

FIG. 5 comparative example 1 (Birnessite-typeMnO)₂) X-ray diffractometer images.

As shown in FIG. 5, comparative example 1 (Birnessite-typeMnO)₂) The method is in good agreement with PDF standard card PDF #52-0556, and shows that the synthesized comparative example 1(Birnessite-type MnO)₂) Has good compatibility and good crystallinity.

< test example 2>

Testing of catalytic Properties of materials

The defective P3H obtained in example 1 was sampled_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Adding carbon black (the mass ratio is 30%: 70%) into an oxygen reduction catalyst, grinding the mixture in an agate mortar for 0.5 hour to obtain an electrocatalyst, adding 50 microliter of Nafion (5 wt.%), 1010 microliter of ethanol and 100 microliter of deionized water, carrying out ultrasonic treatment on the mixed solution for 10 minutes by using an ultrasonic cell crusher, uniformly carrying out ultrasonic treatment, coating a proper amount of the mixed solution on the surface of a glassy carbon electrode, obtaining a uniformly covered catalyst film by adopting a rotary drying method, and controlling the defect type P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The loading capacity is 0.12mg/cm². The catalytic performance of the material was characterized by a rotating disk electrode and an electrochemical workstation.

Adding carbon black (the mass ratio is 30%: 70%) into the Birnessite-type layered manganese dioxide prepared in the comparative example 1, placing the mixture into an agate mortar for grinding for 0.5 hour, adding 50 microliter of Nafion (5 wt.%), 1010 microliter of ethanol and 100 microliter of deionized water, carrying out ultrasonic treatment on the mixed solution for 10 minutes by using an ultrasonic cell crusher, taking a proper amount of the mixed solution after the ultrasonic treatment is uniform, coating the mixed solution on the surface of a glassy carbon electrode, obtaining a uniformly-covered catalyst film by adopting a rotary drying method, and controlling the loading capacity of the Birnessite-type layered manganese dioxide to be 0.12mg/cm². The catalytic performance of the material was characterized by a rotating disk electrode and an electrochemical workstation.

The O3 type layered lithium manganate (Li) obtained in comparative example 2 was used₂MnO₃) Adding carbon black (30 mass percent: 70 percent), grinding for 0.5 hour in an agate mortar, adding 50 microliter of Nafion (5 wt.%), 1010 microliter of isopropanol and 100 microliter of deionized water, carrying out ultrasonic treatment on the mixed solution for 10 minutes by using an ultrasonic cell disruptor, uniformly carrying out ultrasonic treatment, coating a proper amount of the mixed solution on the surface of a glassy carbon electrode, obtaining a uniformly-covered catalyst film by adopting a rotary drying method, and controlling O3 type layered lithium manganate (Li 3 type layered lithium manganate)₂MnO₃) The loading capacity is 0.12mg/cm². The catalytic performance of the material was characterized by a rotating disk electrode and an electrochemical workstation.

The carbon black used in this test example was VulcanXC-72R.

The test results are shown in FIGS. 6-8.

FIG. 6 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The oxygen reduction polarization curves of the catalysts prepared in the comparative examples 1-2.

As shown in FIG. 6, the deficient type P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11the/C has the maximum limit diffusion current and the minimum overpotential, and the oxygen reduction performance is optimal.

FIG. 7 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The catalyst prepared in comparative examples 1-2 and/C) the percent yield of peroxide by-product and the number of electron transfers.

As shown in FIG. 7, the potential range of 0-0.85Vvs. RHE is for defective P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11C, reaction pathway exhibiting four electrons, reaction by-product HO^2-The yield is less than 15%.

FIG. 8 shows example 1 (defective P3H)_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11/C) stability plot of the catalyst after 10000 cycles of cyclic voltammetry at a sweep rate of 100 mV/s.

As shown in FIG. 8, the deficient type P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11the/C showed excellent cycling stability.

< test example 3>

Microfluidic fuel cell performance testing

The defective P3H prepared in example 1 was used_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Assembled into a microfluidic fuel cell. Taking defective P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Adding carbon black (30 mass percent: 70 mass percent), mixing with deionized water, isopropanol and Nafion solution uniformly by ultrasonic, spraying on carbon paper as cathode, controlling defective P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The loading capacity is 2.4mg/cm². Uniformly mixing 20 wt% of Pt/C (Johnson-Matthey) with deionized water, isopropanol and Nafion solution by ultrasonic wave, spraying the mixture on carbon paper to be used as an anode, and controlling the Pt loading amount to be 0.8mg/cm². 3M potassium hydroxide solution was used as the electrolyte. The microfluidic fuel cell was subjected to performance testing, and the results are shown in fig. 9.

As shown in fig. 9, the catalyst obtained in example 1 has excellent catalytic performance. The defect P3 manganese oxide H provided by the invention_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The oxygen reduction catalyst has larger specific surface area, can provide larger active surface area and more active sites, and can effectively stabilize the layered structure due to the blending of positive tetravalent manganese ions and positive monovalent lithium ions in the transition metal layer, thereby effectively inhibiting the tendency of structural deformation and performance attenuation in the circulation process, and simultaneously, the generation of oxygen vacancies and the reduced interlayer spacing can be subjected to concerted catalysis in the acid etching process, thereby improving the oxygen reduction performance.

Effects and effects of the embodiments

According to the oxygen-deficient electrocatalytic material related to example 1, the layered lithium manganate (Li) with mature process and good thermal stability is selected₂MnO₃) As a precursor, a non-noble metal cathode catalyst with high oxygen reduction activity is prepared by simple acid etching, so the embodiment 1 has the advantages of simple and efficient preparation method, mild reaction conditions, easy popularization and application and the like.

The oxygen deficient electrocatalytic material according to example 1 is deficient in P3H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11Has large specific surface area, and can be used for electrolysisThe contact of the liquid and the catalyst provides larger active surface area and more active sites, and the oxygen reduction activity of the catalyst can be effectively improved.

According to the oxygen-deficient electrocatalytic material of example 1, since the transition metal layer contains doped lithium, the stability of the layered structure can be improved, and the layered structure can be prevented from being broken during the cycle. Meanwhile, oxygen vacancies generated in the acid etching process and the reduced interlayer spacing can be catalyzed cooperatively, so that the oxygen reduction performance of the material is improved.

The defective P3 manganese oxide electrocatalytic material related to example 1 is due to defective P3 manganese oxide H_1.0(H_0.13Li_0.17□_0.03Mn_0.67)O_1.89□_0.11The oxygen reduction catalyst has larger specific surface area, so larger active surface area and more active sites can be provided, and the blending of positive tetravalent manganese ions and positive monovalent lithium ions in the transition metal layer can effectively stabilize the layered structure, effectively inhibit the structural deformation and the tendency of performance attenuation in the circulation process, and simultaneously the generation of oxygen vacancies and the reduced interlayer spacing can be subjected to concerted catalysis in the acid etching process, so the oxygen reduction performance is improved.

The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.

Claims

1. A defective P3 manganese oxide electrocatalytic material is characterized by the following chemical formula:

representing an atomic defect.

2. The defective P3 manganese oxide electrocatalytic material as set forth in claim 1, wherein the preparation method comprises the steps of:

step 1, stirring and mixing lithium hydroxide and manganese carbonate, and then placing the mixture in a muffle furnace to react for 36-48 h at 400-500 ℃ to obtain layered lithium manganate;

step 2, dispersing the layered lithium manganate into a sulfuric acid solution with the concentration of 2M-3M, stirring for 6h-24h at room temperature, washing and drying to obtain the layered lithium manganate

3. The defective P3 manganese oxide electrocatalytic material according to claim 2,

wherein the molar ratio of the lithium hydroxide to the manganese carbonate is (1.8-2.5): 1.

4. The defective P3 manganese oxide electrocatalytic material according to claim 2,

wherein, in the step 1, the sintering gas in the muffle furnace is air.

5. The deficient P3 manganese oxide electrocatalytic material of claim 2, wherein:

wherein the sintering temperature in the muffle furnace in the step 1 is 450 ℃.

6. The deficient P3 manganese oxide electrocatalytic material of claim 2, wherein:

wherein the concentration of the sulfuric acid solution in the step 2 is 2.5M.

7. The deficient P3 manganese oxide electrocatalytic material of claim 2, wherein:

wherein the stirring time at room temperature in the step 2 is 12 h.

8. An electrocatalyst, characterized in that,

by

Grinding and mixing with carbon powder.

9. An electrocatalyst according to claim 8, wherein:

wherein the content of the first and second substances,

the mass ratio of the carbon powder to the carbon powder is 10 percent to 90 percent to 30 percent to 70 percent.

10. An electrocatalyst according to claim 8, wherein:

wherein the model of the carbon powder is Vulcan XC-72R.