Electrocatalytic material based on solid waste of opencast coal mine as well as preparation method and application of electrocatalytic material

Abstract

The invention belongs to the technical field of open-pit coal mine solid waste high-value utilization, and discloses an electro-catalytic material based on open-pit coal mine solid waste and a preparation method and application of the electro-catalytic material. The electro-catalysis material is prepared from the following preparation raw materials in parts by weight through hydrothermal reaction: 5 to 40 parts of modified open pit coal mine solid waste powder slag, 20 to 60 parts of molybdenum amino acid tetrahydrate, 10 to 25 parts of anhydrous dextrose and 20 to 35 parts of water, the modified open pit coal mine solid waste powder slag is prepared by the following steps: crushing and grinding open pit coal mine waste stone, uniformly mixing with sodium carbonate, and calcining to obtain calcined powder slag; standing the calcined powder slag in a hydrofluoric acid solution to obtain a mixed solution; and centrifugally washing the mixed solution until the pH is neutral, and drying to obtain the modified open pit coal mine solid waste powder slag. The electro-catalytic material disclosed by the invention has stable and efficient catalytic performance, and high-valued utilization of solid waste of the open pit coal mine is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of high-value utilization of solid waste in open-pit coal mines, and particularly to an electrocatalytic material based on solid waste in open-pit coal mines, its preparation method and application. Background Art

[0002] Lithium-air batteries are considered an ideal choice for future high-efficiency energy storage due to their energy density of up to 3500 Wh / kg, which can help resolve the contradiction between energy and environmental protection.

[0003] However, the oxygen reaction rate at the positive electrode of lithium-air batteries is relatively slow, mainly due to the low solubility of oxygen in the positive electrode electrolyte, limited diffusion rate, insufficient activity of the positive electrode catalyst leading to slow oxygen reduction reaction kinetics, and the structure of the positive electrode material being unfavorable for oxygen transport and reaction, thus affecting the cycle stability of the battery and hindering further industrial promotion and application. In addition, during the discharge process, not only is the produced lithium peroxide poorly conductive, but the accumulation of lithium carbonate by-products on the electrode further increases polarization, resulting in a significant decline in battery performance.

[0004] In recent years, research has shown that cathode catalysts play a crucial role in solving the problem of the relatively slow oxygen reaction rate at the positive electrode of lithium-air batteries. The core mechanism is that the catalyst can significantly reduce the activation energy barriers of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), providing abundant active sites, thereby effectively promoting electron transfer kinetics. By optimizing the surface structure and electronic state of the catalyst, the adsorption energy, diffusion rate, and reaction activity of oxygen on the positive electrode surface can be enhanced, thereby reshaping the reaction path, reducing the reaction impedance, and achieving a significant increase in the oxygen reaction rate. In addition, an efficient cathode catalyst can effectively inhibit the occurrence of side reactions, improve the selectivity and stability of the reaction, and provide a strong guarantee for the efficient and stable operation of lithium-air batteries.

[0005] However, currently existing cathode catalysts are mainly prepared from carbon materials, transition metal oxides, noble metals, and other composite materials. Although the prepared cathode catalysts have a certain stability, their main active component is a noble metal, and the price of noble metals is expensive, resulting in a high preparation cost of the cathode catalyst and being unfavorable for popularization and use. Therefore, how to reduce the preparation cost of the cathode catalyst on the basis of avoiding too rapid a decline in the performance of lithium-air batteries has become a technical problem in this field. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an electrocatalytic material based on solid waste in open-pit coal mines, its preparation method and application.

[0007] The electrocatalytic material based on solid waste in open-pit coal mines, its preparation method and application of the present invention are achieved through the following technical solutions:

[0008] The first object of the present invention is to provide an electrocatalytic material based on solid waste from surface coal mines, which is prepared by hydrothermal reaction from the following raw materials in parts by weight:

[0009] 5 to 40 parts of modified solid waste powder from surface coal mines, 20 to 60 parts of molybdic acid tetrahydrate, 10 to 25 parts of anhydrous glucose, and 20 to 35 parts of water.

[0010] It should be noted that in order to avoid the situation that the by-products of lithium peroxide and lithium carbonate are generated during the discharge process of the cathode material of the lithium-air battery currently used in the prior art, which leads to the decline of the battery performance of the lithium-air battery, the present invention preferably uses solid waste from surface coal mines as the raw material for preparing the catalyst. It can not only reduce the preparation cost of the lithium-air battery catalyst, but also improve the high-value utilization rate of solid waste from surface coal mines, and can also slow down or solve the serious threat posed by the open-air stacking of solid waste from surface coal mines to land resources and the ecological environment.

[0011] It should also be noted that considering the defects of complex components and low activity of solid waste from surface coal mines, it is difficult to directly use it as the raw material for preparing electrocatalysts. Therefore, the modified solid waste powder from surface coal mines used in the present invention is prepared by the following steps:

[0012] 1) Crushing and grinding the waste stone from surface coal mines to obtain solid waste powder from surface coal mines.

[0013] 2) Mixing the solid waste powder from surface coal mines with sodium carbonate and then grinding and mixing them evenly to obtain a mixed powder.

[0014] 3) Calcining the mixed powder to obtain a calcined powder residue.

[0015] 4) Dispersing the calcined powder residue in a hydrofluoric acid solution and then standing to obtain a mixed solution.

[0016] 5) Centrifugally washing the mixed solution, centrifugally washing until the pH is neutral and then drying to obtain the modified solid waste powder from surface coal mines.

[0017] Among them, it should be noted that in some preferred embodiments of the present invention, the waste stone from surface coal mines is crushed and ground to a particle size ≤ 200 μm to obtain solid waste powder from surface coal mines, so as to ensure that the obtained solid waste powder from surface coal mines can effectively pass through subsequent treatments to obtain modified solid waste powder from surface coal mines. In some more preferred embodiments of the present invention, the waste stone from surface coal mines is crushed and ground to a particle size of 50 μm to 200 μm to improve the utilization rate of waste stone, optimize subsequent treatment processes and enhance overall economic benefits.

[0018] The present invention uses sodium carbonate as the first modifier. First, it is mixed with the solid waste powder residue of the opencast coal mine by grinding to achieve the purpose of promoting the uniform mixing of the solid waste powder residue and sodium carbonate and facilitating the subsequent reaction. Then, the mixed powder obtained by grinding is calcined, so that the mixed powder undergoes physical and chemical changes with sodium carbonate during the alkali calcination process, achieving the purpose of optimizing the powder properties and improving its application value, and obtaining the calcined powder residue.

[0019] Among them, in some more preferred embodiments of the present invention, the addition amount of the sodium carbonate is 1 / 4 - 2 / 3 of the mass of the solid waste powder residue of the opencast coal mine, so as to achieve the purpose of full reaction, improving the modification effect and avoiding the increase in cost caused by excessive addition.

[0020] In some more preferred embodiments of the present invention, the calcination temperature of the calcination treatment is 850°C - 900°C, and the calcination time is 2h - 3h, so as to achieve the purpose of ensuring complete calcination reaction, forming a stable modified product and avoiding the performance decline caused by overcalcination.

[0021] In some more preferred embodiments of the present invention, when grinding the solid waste powder residue of the opencast coal mine and sodium carbonate, the grinding time is 10min - 20min.

[0022] The present invention uses hydrofluoric acid solution as the second modifier. By dispersing the calcined powder residue in the hydrofluoric acid solution and standing, the hydrofluoric acid solution can fully contact the calcined powder residue, thereby achieving the purpose of further removing impurity metal elements in the calcined powder residue.

[0023] In some preferred embodiments of the present invention, the addition amount of the hydrofluoric acid solution is 4 - 8 times the mass of the calcined powder residue, so as to achieve the purpose of completely removing impurity metal elements in the calcined powder residue. Among them, in some more preferred embodiments of the present invention, the mass concentration of hydrofluoric acid in the hydrofluoric acid solution is 40%.

[0024] In some preferred embodiments of the present invention, the temperature of the standing treatment is room temperature, and the standing time is 18h - 30h, so as to achieve the purpose of fully removing impurities.

[0025] In some more preferred embodiments of the present invention, when centrifugally washing the mixed solution, the rotation speed of each centrifugation is 8000rpm - 11000rpm, the centrifugation time of each time is 3min - 5min. Each time of centrifugal washing is first washed with water as the washing solvent until the pH is 7, and then centrifugally washed once with anhydrous ethanol as the washing solvent.

[0026] In some more preferred embodiments of the present invention, when drying the product after centrifugal washing, the drying temperature is 55°C - 65°C, and the drying time is 16h - 30h.

[0027] In some more preferred embodiments of the present invention, in order to avoid the agglomeration of the solid waste powder residue of the open-pit coal mine during the calcination treatment and drying process, the dried product is also ground to reduce its particle size to ≤200 μm. More preferably, it is 50 μm to 200 μm.

[0028] The second object of the present invention is to provide a preparation method of the above-mentioned electrocatalytic material based on the solid waste of the open-pit coal mine, including the following steps:

[0029] Step 1, prepare the raw materials for preparation:

[0030] Weigh the corresponding masses of the modified solid waste powder residue of the open-pit coal mine, molybdic acid ammonium tetrahydrate, anhydrous glucose and water according to the composition of the raw materials for preparing the electrocatalytic material and set them aside.

[0031] Step 2, hydrothermal reaction:

[0032] After mixing the weighed modified solid waste powder residue of the open-pit coal mine, molybdic acid ammonium tetrahydrate and anhydrous glucose evenly, add the weighed water and mix well, and then carry out the hydrothermal reaction.

[0033] Step 3, post-treatment:

[0034] Centrifuge and wash the reaction solution of the hydrothermal reaction, dry it after centrifuging and washing until the pH is neutral to obtain the electrocatalytic material.

[0035] The present invention uses the modified solid waste powder residue of the open-pit coal mine and molybdic acid ammonium tetrahydrate as the source materials, and uses anhydrous glucose as the dispersant, complexing agent, dispersant and structure-directing agent source. When anhydrous glucose is mixed and dispersed in water for hydrothermal reaction, the glucose molecules act as template agents and have a certain spatial structure, which can be used as template agents in the hydrothermal reaction to guide the formation of specific structures, such as preparing metal oxides or carbon materials with specific morphologies. At the same time, glucose can also be used as a complexing agent: the hydroxyl groups in glucose can form complexes with metal ions, thereby affecting the solubility, precipitation and crystallization behavior of metal ions. Moreover, glucose can also be used as a dispersant: glucose can improve the dispersibility of the reactants, prevent agglomeration, and contribute to the formation of a uniform product. In addition, glucose can also be used as a structure-directing agent: in the solvothermal synthesis reaction, glucose can play a role in structure direction and affect the crystal phase and morphology of the nano-products.

[0036] In some preferred embodiments of the present invention, the temperature of the hydrothermal reaction is 175°C to 185°C, and the reaction time is 8 h to 16 h to achieve the purpose of fully activating the modification.

[0037] In some preferred embodiments of the present invention, the modified open-pit coal mine solid waste powder residue, ammonium molybdate tetrahydrate and anhydrous glucose are mixed evenly by grinding, and the grinding time is 10 min to 20 min.

[0038] In some preferred embodiments of the present invention, when centrifugally washing the reaction solution of the hydrothermal reaction, the rotation speed of each centrifugation is 8000 rpm to 11000 rpm, the centrifugation time for each time is 3 min to 5 min, and when centrifugally washing each time, water is used as the washing solvent first to wash until the pH is 7, and then anhydrous ethanol is used as the washing solvent for centrifugal washing once. Among them, in some more preferred embodiments of the present invention, when drying the product after centrifugal washing, the drying temperature is 55 °C to 65 °C, and the drying time is 16 h to 30 h.

[0039] The third object of the present invention is to provide an application of the above-mentioned electrocatalytic material based on open-pit coal mine solid waste in the preparation of a lithium-oxygen battery.

[0040] In some preferred embodiments of the present invention, the electrocatalytic material is sprayed on the surface of the cathode of the lithium-oxygen battery, and after curing, an electrocatalytic material layer is formed on the surface of the cathode of the lithium-oxygen battery, so as to achieve the purpose of preparing an integrated lithium-air battery cathode with a catalyst coating.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention uses open-pit coal mine solid waste as the raw material for preparing the catalyst, and uses sodium carbonate as the first modifier. By first mixing it with the open-pit coal mine solid waste powder residue by grinding, the purpose of promoting the uniform mixing of the solid waste powder residue and sodium carbonate and promoting the subsequent reaction is achieved. Then, the mixed powder obtained by grinding is subjected to calcination treatment, so that physical and chemical changes occur between the mixed powder and sodium carbonate during the alkali burning process. Then, hydrofluoric acid solution is used as the second modifier. By dispersing the calcined powder residue in the hydrofluoric acid solution and standing, the hydrofluoric acid solution can fully contact the calcined powder residue, thereby further removing the impurity metal elements in the calcined powder residue to obtain a modified open-pit coal mine solid waste powder residue. The modified open-pit coal mine solid waste powder residue, ammonium molybdate tetrahydrate, anhydrous glucose and water are jointly used to prepare the electrocatalytic material, which can not only reduce the preparation cost of the lithium-air battery catalyst, but also improve the high-value utilization rate of the open-pit coal mine solid waste, and can also slow down or solve the serious threat caused by the open-air stacking of the open-pit coal mine solid waste to land resources and the ecological environment.

[0043] The present invention uses modified solid waste powder residue from open-pit coal mines and ammonium molybdate tetrahydrate as raw materials, and anhydrous glucose as a dispersant, complexing agent, dispersant and structure-directing agent source. By adopting hydrothermal reaction, an electrocatalytic material with nanoscale size is successfully prepared. The preparation process is simple and the cost is low, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 XRD patterns of the solid waste powder residue from open-pit coal mines, ammonium molybdate tetrahydrate and the modified solid waste powder residue from open-pit coal mines used in Example 1.

[0045] Figure 2 SEM image of the solid waste powder residue from open-pit coal mines used in Example 1.

[0046] Figure 3 SEM image of ammonium molybdate tetrahydrate used in Example 1.

[0047] Figure 4 SEM image of the modified solid waste powder residue from open-pit coal mines prepared in Example 1.

[0048] Figure 5 SEM image of the electrocatalytic material prepared in Comparative Example 1.

[0049] Figure 6 SEM image of the electrocatalytic material prepared in Comparative Example 2.

[0050] Figure 7 Test results of the rate performance of the lithium-air battery assembled with the electrocatalytic material of Example 1 as the negative electrode.

[0051] Figure 8 Test results of the cycle performance of the lithium-air battery assembled with the electrocatalytic material of Example 1 as the negative electrode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0053] Example 1

[0054] This example provides an electrocatalytic material based on solid waste from open-pit coal mines, which is prepared by the following steps:

[0055] Step 1, prepare the raw materials for preparation:

[0056] 1.1) Prepare the modified solid waste powder residue from open-pit coal mines:

[0057] 1.1.1) Crush and grind the waste stone after coal mining and stripping in open-pit coal mines, and screen it through a sieve with a pore size of 200 μm to obtain solid waste powder residue from open-pit coal mines with a particle size < 200 μm.

[0058] 1.1.2) Mix the solid waste powder residue from the surface coal mine with sodium carbonate according to the addition amount of sodium carbonate being 2 / 3 of the mass of the solid waste powder residue from the surface coal mine, and then grind for 15 min to obtain a mixed powder.

[0059] 1.1.3) Calcinate the mixed powder at 875 °C for 2.5 h to obtain a calcined powder residue.

[0060] 1.1.4) Add the calcined powder residue to a hydrofluoric acid solution with a corresponding mass according to the addition amount of the hydrofluoric acid solution being 4 times the mass of the calcined powder residue, stir for 15 min, and then carry out a static treatment at room temperature for 24 h to obtain a mixed solution.

[0061] 1.1.5) Centrifuge and wash the mixed solution. The rotation speed for each centrifugation is 9500 rpm, and the centrifugation time for each time is 3 min - 5 min. When centrifuging and washing each time, first use water as the washing solvent to wash until the pH is 7, and then use absolute ethanol as the washing solvent for centrifugal washing once to obtain a centrifuged and washed product. Then place the centrifuged and washed product in an oven at 60 °C and dry for 24 h, grind it, and pass it through a sieve with a pore size of 200 μm to obtain a modified solid waste powder residue from the surface coal mine with a particle size <200 μm.

[0062] 1.2) Weigh the respective corresponding masses:

[0063] Weigh the respective corresponding masses of the modified solid waste powder residue from the surface coal mine, ammonium molybdate tetrahydrate, anhydrous glucose, and deionized water for standby according to the following component composition by weight:

[0064] 16 parts of modified solid waste powder residue from the surface coal mine, 60 parts of ammonium molybdate tetrahydrate, 24 parts of anhydrous glucose, and 35 parts of deionized water.

[0065] Step 2: After uniformly mixing the weighed modified solid waste powder residue from the surface coal mine, ammonium molybdate tetrahydrate, and anhydrous glucose, add the weighed water and mix well, and then carry out a hydrothermal reaction at 180 °C for 12 h.

[0066] Step 3: Centrifuge and wash the reaction solution of the hydrothermal reaction. The rotation speed for each centrifugation is 9500 rpm, and the centrifugation time for each time is 3 min - 5 min. When centrifuging and washing each time, first use water as the washing solvent to wash until the pH is 7, and then use absolute ethanol as the washing solvent for centrifugal washing once to obtain a centrifuged and washed product. Then place the centrifuged and washed product in an oven at 60 °C and dry for 24 h to obtain an electrocatalytic material.

[0067] Example 2

[0068] This example provides an electrocatalytic material based on solid waste from a surface coal mine, which is prepared through the following steps:

[0069] Step 1, Prepare raw materials for preparation:

[0070] 1.1) Prepare modified solid waste powder residue from open-pit coal mines:

[0071] 1.1.1) Crush and grind the waste stone after coal stripping in open-pit coal mining, and sieve it through a sieve with a pore size of 200 μm to obtain solid waste powder residue from open-pit coal mines with a particle size < 200 μm.

[0072] 1.1.2) According to the addition amount of sodium carbonate being 1 / 4 of the mass of the solid waste powder residue from open-pit coal mines, mix the solid waste powder residue from open-pit coal mines with sodium carbonate, and then grind for 15 min to obtain a mixed powder.

[0073] 1.1.3) Calcinate the mixed powder at 850 °C for 3 h to obtain a calcined powder residue.

[0074] 1.1.4) According to the addition amount of hydrofluoric acid solution being 6 times the mass of the calcined powder residue, add the calcined powder residue to the corresponding mass of hydrofluoric acid solution, stir for 10 min, and then carry out static treatment at room temperature for 18 h to obtain a mixed solution.

[0075] 1.1.5) Centrifuge and wash the mixed solution. The rotation speed for each centrifugation is 8000 rpm, and the centrifugation time for each time is 3 min - 5 min. When centrifuging and washing each time, first use water as the washing solvent to wash until the pH is 7, and then use absolute ethanol as the washing solvent to carry out centrifugal washing once to obtain a centrifuged and washed product. Then place the centrifuged and washed product in an oven at 55 °C and dry for 16 h, grind it, and sieve it through a sieve with a pore size of 200 μm to obtain modified solid waste powder residue from open-pit coal mines with a particle size < 200 μm.

[0076] 1.2) Weigh each corresponding mass:

[0077] Weigh each corresponding mass of modified solid waste powder residue from open-pit coal mines, ammonium molybdate tetrahydrate, anhydrous glucose, and deionized water for standby according to the following component composition by weight:

[0078] 5 parts of modified solid waste powder residue from open-pit coal mines, 20 parts of ammonium molybdate tetrahydrate, 10 parts of anhydrous glucose, and 20 parts of deionized water.

[0079] Step 2, After uniformly mixing the weighed modified solid waste powder residue from open-pit coal mines, ammonium molybdate tetrahydrate, and anhydrous glucose, add the weighed water and mix well, and then carry out hydrothermal reaction at 175 °C for 8 h.

[0080] Step 3: Centrifuge and wash the reaction solution of the hydrothermal reaction. The rotation speed for each centrifugation is 8000 rpm, and the centrifugation time for each time is 3 min to 5 min. When performing centrifugal washing each time, first use water as the washing solvent to wash until the pH reaches 7, and then use absolute ethanol as the washing solvent for centrifugal washing once to obtain a centrifugally washed product. Then place the centrifugally washed product in an oven at 22 °C and dry it for 16 h to obtain an electrocatalytic material.

[0081] Example 3

[0082] This example provides an electrocatalytic material based on solid waste from open-pit coal mines, which is prepared through the following steps:

[0083] Step 1: Prepare the raw materials for preparation:

[0084] 1.1) Prepare modified solid waste powder residue from open-pit coal mines:

[0085] 1.1.1) Crush and grind the waste stone after coal extraction from open-pit coal mines, and pass it through a sieve with a pore size of 200 μm to obtain solid waste powder residue from open-pit coal mines with a particle size < 200 μm.

[0086] 1.1.2) According to the addition amount of sodium carbonate being 1 / 3 of the mass of the solid waste powder residue from open-pit coal mines, mix the solid waste powder residue from open-pit coal mines with sodium carbonate and then grind for 20 min to obtain a mixed powder.

[0087] 1.1.3) Calcinate the mixed powder at 900 °C for 2 h to obtain a calcined powder residue.

[0088] 1.1.4) According to the addition amount of hydrofluoric acid solution being 8 times the mass of the calcined powder residue, add the calcined powder residue to the corresponding mass of hydrofluoric acid solution, stir for 20 min, and then carry out static treatment at room temperature for 30 h to obtain a mixed solution.

[0089] 1.1.5) Centrifuge and wash the mixed solution. The rotation speed for each centrifugation is 11000 rpm, and the centrifugation time for each time is 3 min to 5 min. When performing centrifugal washing each time, first use water as the washing solvent to wash until the pH reaches 7, and then use absolute ethanol as the washing solvent for centrifugal washing once to obtain a centrifugally washed product. Then place the centrifugally washed product in an oven at 65 °C and dry it for 30 h, grind it, and pass it through a sieve with a pore size of 200 μm to obtain modified solid waste powder residue from open-pit coal mines with a particle size < 200 μm.

[0090] 1.2) Weigh each corresponding mass:

[0091] Weigh each corresponding mass of modified solid waste powder residue from open-pit coal mines, ammonium molybdate tetrahydrate, anhydrous glucose, and deionized water for standby according to the following component composition by weight:

[0092] 40 parts of modified solid waste powder residue from open-pit coal mine, 40 parts of molybdic acid ammonium tetrahydrate, 25 parts of anhydrous glucose, and 30 parts of deionized water.

[0093] Step 2: After uniformly mixing the weighed modified solid waste powder residue from open-pit coal mine, molybdic acid ammonium tetrahydrate, and anhydrous glucose, add the weighed water and mix well. Then, carry out hydrothermal reaction at 185 °C for 16 h.

[0094] Step 3: Centrifuge and wash the reaction solution of the hydrothermal reaction. The rotation speed for each centrifugation is 11,000 rpm, and the centrifugation time for each time is 3 min to 5 min. When centrifuging and washing each time, first use water as the washing solvent to wash until the pH is 7, and then use anhydrous ethanol as the washing solvent to carry out centrifugal washing once to obtain the centrifuged and washed product. Then, place the centrifuged and washed product in an oven at 65 °C and dry it for 30 h to obtain the electrocatalytic material.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 1 is only that:

[0097] In this comparative example, according to the following component composition by weight, weigh the corresponding masses of modified solid waste powder residue from open-pit coal mine, molybdic acid ammonium tetrahydrate, anhydrous glucose, and deionized water for standby:

[0098] 16 parts of modified solid waste powder residue from open-pit coal mine, 80 parts of molybdic acid ammonium tetrahydrate, 24 parts of anhydrous glucose, and 35 parts of deionized water.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 1 is only that:

[0101] In this comparative example, according to the following component composition by weight, weigh the corresponding masses of modified solid waste powder residue from open-pit coal mine, molybdic acid ammonium tetrahydrate, anhydrous glucose, and deionized water for standby:

[0102] 25 parts of modified solid waste powder residue from open-pit coal mine, 60 parts of molybdic acid ammonium tetrahydrate, 24 parts of anhydrous glucose, and 35 parts of deionized water.

[0103] Experimental part

[0104] (I) XRD test

[0105] Since the preparation raw materials used in each embodiment of the present invention are the same, taking the solid waste powder residue from open-pit coal mine, molybdic acid ammonium tetrahydrate, and the modified modified solid waste powder residue from open-pit coal mine used in Example 1 as examples, XRD tests were respectively carried out on them, and the test results are as Figure 1 shown.

[0106] Figure 1XRD patterns of the solid waste powder slag from surface coal mines, ammonium molybdate tetrahydrate, and the modified solid waste powder slag from surface coal mines used in Example 1. It can be seen that compared with the solid waste powder slag from surface coal mines, the treated solid waste powder slag from surface coal mines has fewer impurity peaks and obvious characteristic peaks of molybdenum dioxide.

[0107] (II) SEM Test

[0108] Taking the solid waste powder slag from surface coal mines, ammonium molybdate tetrahydrate, and the modified solid waste powder slag from surface coal mines used in Example 1 of the present invention as examples, SEM tests were respectively carried out on them, and the test results are respectively as Figures 2 to 4 shown.

[0109] Figure 2 SEM image of the solid waste powder slag from surface coal mines used in Example 1. It can be seen that the solid waste powder slag from surface coal mines has an uneven granular structure, and the size is distributed around 500 to 100 nanometers.

[0110] Figure 3 SEM image of ammonium molybdate tetrahydrate used in Example 1. It can be seen that molybdenum oxide exhibits a nanoscale spherical granular structure.

[0111] Figure 4 SEM image of the modified solid waste powder slag from surface coal mines prepared in Example 1. It can be seen that a layer of nanosheets is coated on the surface of the fine slag of coal gasification. Under the conditions of high temperature and high pressure solvent heat on the surface and the structure guiding effect of glucose, the structure of molybdenum oxide changes from spherical particles to nanosheet structure and uniformly covers the surface of the fine slag of coal gasification.

[0112] By observing the microstructure of the electrocatalytic material prepared in Example 1 of the present invention, it is known that the molybdenum oxide nanoparticles formed from ammonium molybdate tetrahydrate in Example 1 are uniformly loaded on the surface of the modified solid waste powder slag from surface coal mines, and no agglomeration phenomenon occurs.

[0113] Taking the electrocatalytic materials prepared in Comparative Example 1 and Comparative Example 2 of the present invention as examples, SEM tests were respectively carried out on them, and the test results are respectively as Figure 5 and Figure 6 shown.

[0114] Figure 5 SEM image of the electrocatalytic material prepared in Comparative Example 1. It can be seen that due to excessive addition of ammonium molybdate tetrahydrate, there is too much molybdenum oxide component on the surface of the generated modified solid waste powder slag from surface coal mines, and the molybdenum oxide nanoparticles agglomerate on the surface, resulting in partial active sites being covered, reducing the contact area between the catalyst and the reactants, and increasing the mass transfer resistance of the reactants and products on the surface of the catalyst, thereby reducing the catalytic efficiency.

[0115] Figure 6This is the SEM image of the electrocatalytic material prepared in Comparative Example 2. It can be seen that due to the excessive addition of modified open-pit coal mine solid waste powder and slag, the molybdenum oxide component on the surface of the final open-pit coal mine solid waste powder and slag is too little and the surface of the solid waste fine slag cannot be evenly coated. Too little molybdenum oxide component means insufficient active sites, resulting in reduced catalytic efficiency.

[0116] (III) Catalytic performance test

[0117] Since the electrocatalytic materials of Examples 1 to 3 have similar structures, those skilled in the art should know that similar structures lead to similar performances. In order to avoid redundant description, the present invention takes the electrocatalytic material prepared in Example 1 as an example, using carbon paper as the cathode of the lithium oxygen battery, and the electrocatalytic material is prepared according to 0.7 mg / cm 2 The electrocatalytic material of Example 1 is sprayed on the cathode surface of the lithium oxygen battery to obtain a negative electrode based on the electrocatalytic material of Example 1. According to the prior art in the art, the obtained negative electrode is assembled to obtain a corresponding lithium oxygen battery, and the electrocatalytic performance of the lithium oxygen battery is measured to obtain the following: Figure 7 and Figure 8 Rate performance and performance after multiple sustained cycles are shown.

[0118] Figure 7 The rate performance test results of the lithium-air battery assembled with the electrocatalytic material of Example 1 as the negative electrode show that the lithium-air battery exhibits good rate performance under the action of the modified open-pit coal mine solid waste slag catalyst. -1 Even under high current density conditions, it can stably supply and store electrical energy, and its charge and discharge overpotential remains at around 1.45V, and in the subsequent 500mAg -1 Under the current density test conditions, it can continue to cycle stably for 900 hours and still maintain a relatively stable overpotential of 1.72V.

[0119] Figure 8 The cycle performance test results of the lithium-air battery assembled by using the electrocatalytic material of Example 1 as the negative electrode show that under the action of the modified open-pit coal mine solid waste slag catalyst, the lithium-air battery has a cycle performance of 500 mA g -1 It can stably store energy for more than 900 hours under the current density test conditions. It can also be seen that during the 1st cycle to the 900th cycle, the discharge-charge overpotential increases from 0.5V to 1.8V, which further shows that the lithium oxygen battery based on the electrocatalytic material of open-pit coal mine solid waste of the present invention has excellent catalytic performance and stability.

[0120] Obviously, the above embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. An electrocatalytic material based on open-pit coal mine solid waste, characterized in that: Prepared by hydrothermal reaction of the following raw materials in parts by weight: 5 to 40 parts of modified open-pit coal mine solid waste powder, 20 to 60 parts of molybdenum acid tetrahydrate, 10 to 25 parts of anhydrous glucose and 20 to 35 parts of water; Wherein, the modified open-pit coal mine solid waste powder slag is prepared by the following steps: The open-pit coal mine waste rock is crushed and then ground to obtain the open-pit coal mine solid waste powder slag; The open-pit coal mine solid waste powder and slag are mixed with sodium carbonate and then ground and mixed to obtain a mixed powder; calcining the mixed powder to obtain calcined powder residue; After dispersing the calcined powder residue in a hydrofluoric acid solution, the solution is allowed to stand to obtain a mixed solution; The mixed solution is centrifuged and washed until the pH value is neutral, and then dried to obtain the modified open-pit coal mine solid waste powder slag.

2. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The added amount of the sodium carbonate is 1 / 4 to 2 / 3 of the mass of the open-pit coal mine solid waste powder slag.

3. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The amount of the hydrofluoric acid solution added is 4 to 8 times the mass of the calcined slag.

4. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The mass concentration of hydrofluoric acid in the hydrofluoric acid solution is 40%.

5. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The calcination temperature of the calcination treatment is 850° C. to 900° C., and the calcination time is 2 h to 3 h.

6. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 175° C. to 185° C., and the reaction time is 8 h to 16 h.

7. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The temperature of the static treatment is room temperature, and the static time is 18h to 30h.

8. The electrocatalytic material based on open-pit coal mine solid waste according to claim 1, characterized in that: The particle size of the open-pit coal mine solid waste powder slag is ≤200 μm.

9. A method for preparing an electrocatalytic material based on open-pit coal mine solid waste according to any one of claims 1 to 8, characterized in that: The following steps are involved: According to the composition of the raw materials for preparing the electrocatalytic material, corresponding masses of modified open-pit coal mine solid waste powder, molybdenum acid tetrahydrate, anhydrous glucose and water are weighed for later use; After the weighed modified open-pit coal mine solid waste powder, molybdenum acid tetrahydrate and anhydrous glucose are evenly mixed, the weighed water is added and mixed, and then a hydrothermal reaction is carried out; The reaction liquid of the hydrothermal reaction is centrifugally washed until the pH value is neutral and then dried to obtain the electrocatalytic material.

10. Use of the electrocatalytic material based on open-pit coal mine solid waste according to any one of claims 1 to 8 in the preparation of lithium oxygen batteries.

Images