WO2019196104A1 - Nanomaterial having self-supporting nanosheet, preparation method therefor and use thereof - Google Patents

Abstract

Disclosed are a nanomaterial having a self-supporting nanosheet, a preparation method therefor and a use thereof. The core of the material is a metal core with a particle size of 0.05 μm-20 μm, and the surface of the metal core is a self-supporting nanostructure formed by a corresponding metal hydroxide and/or metal oxide nanosheet. The metal hydroxide and/or metal oxide nanosheet of the present invention are formed based on self-crosslinking assembly between a sheet layer and a metal inner core and between the sheet layers, have a higher specific surface area and a stable three-dimensional network structure, and combine the excellent physical and chemical properties of the metal hydroxide and the ultra-thin property of the nanosheets.

Description

 Nano material with self-supporting nanosheet and preparation method and application thereof

A method for preparing a nano material having a plurality of layers of self-supporting metal hydroxide and/or metal oxide nanosheets, comprising the steps of:

1) mixing metal flakes or metal particles having an average particle size of 1 μm to 100 μm with an aqueous solution, and the reaction is sufficient not higher than 80 ° C;

2) After the reaction is completed, it is filtered, washed, and dried at not higher than 100 ° C to obtain a nanomaterial having a self-supporting metal hydroxide and/or metal oxide nanosheet.

As a further improvement of the above production method, the thickness of the metal piece is preferably from 0.1 μm to 50 μm.

When the raw material metal particle size used is less than 0.1 μm, the specific surface area is too large, the reaction is too intense, and the oxide or hydroxide does not completely follow the surface growth with the lowest surface energy, so that the nanosheet structure cannot be formed; and the raw material metal particles When the size exceeds 100 μm, the specific surface area is too small, the reaction rate is very slow, the nanosheet cannot grow continuously, and it changes to other morphology during the growth process, and it cannot form a self-supporting metal hydroxide and/or metal on the core surface. Oxide nanosheets; when the thickness of the metal sheet used is less than 0.1 μm, the specific surface area is too large, the reaction is too intense, and the oxide or hydroxide does not completely follow the surface growth with the lowest surface energy, so the nanosheet structure cannot be formed. When the thickness of the metal sheet exceeds 50 μm, the specific surface area is too small, the reaction rate is very slow, the nanosheet cannot grow continuously, and it changes to other morphology during the growth process, and it cannot form a multilayer self-supporting metal hydroxide on the core surface. And/or metal oxide nanosheets.

Neutral or alkaline conditions can promote the production and growth of metal hydroxides/oxides, which facilitate the formation of multiple layers of self-supporting metal hydroxide and/or metal oxide nanosheets on the surface of the metal core. However, when the concentration of OH- in the solution is too high, the corrosion is too strong, and the metal is directly etched, and even the nanostructures that have been formed are destroyed. As a further improvement of the above preparation method, the pH of the aqueous solution is from 7 to 14.

Increasing the temperature within a certain range helps to accelerate the oxidation reaction of the metal, but at temperatures above 80 ° C, the reaction may cause the reaction to form the nanostructures excessively. In order to obtain a multilayer self-supporting metal hydroxide and/or metal oxide nanosheet excellent in morphology, the reaction is preferably carried out at a temperature not exceeding 80 °C. The further modified reaction temperature as the above production method is preferably from 15 to 45 °C.

In order to avoid destruction of the metal hydroxide/oxide nanosheet during drying, the drying temperature is further preferably not more than 80 ° C, and the metal hydroxide/oxide nanosheet may be better prevented from being destroyed below 60 ° C.

Stirring can make the reaction more uniform and rapid, but at high speeds, a large shear force is generated, causing the resulting nanosheets to fall off the metal core. As a further improvement of the above preparation method, the stirring rate is 50-500 Rpm.

As a further improvement of the above preparation method, the metal is an alloy formed of a transition metal element or a transition metal. Further, the metal is selected from at least one of cobalt, nickel, copper, iron, zinc, manganese, molybdenum, or an alloy of at least two metal elements. Alloys include, but are not limited to, nickel-cobalt alloys, nickel-iron alloys, copper-nickel alloys, iron-cobalt-nickel alloys, cobalt-zinc alloys, and the like.

As a further improvement of the above preparation method, the particle size of the metal core after the reaction is 0.05 μm to 20 Mm. Further, after the reaction, the particle diameter of the granular metal core is 0.05 μm to 10 μm; and the particle size of the sheet metal core is 0.05 μm to 10 μm.

As a further improvement of the above production method, the average thickness of the sheet metal core after the completion of the reaction is 0.01 to 1 μm.

As a further improvement of the above preparation method, the average thickness of the nanosheets after the end of the reaction is from 1 nm to 50 nm.

As a further improvement of the above preparation method, the length of the nanosheet after the end of the reaction is from 100 nm to 100 μm.

The reaction time can be adjusted accordingly depending on the size of the starting metal particles used, the reaction temperature, and the characteristics of the nanomaterials including, but not limited to, the particle size of the metal core, the thickness of the nanosheet, and the length. In general, the reaction time is at least 2 hours, preferably 5 hours or more, such as 5 to 15 hours, 5 to 10 hours.

As a further improvement of the above preparation method, the preparation method of the metal sheet comprises: mixing metal particles having an average particle size of 1 to 50 μm and a surfactant, and ball milling to obtain a metal piece.

As a further improvement of the above preparation method, the surfactant is polyethylene glycol added in an amount of 0.5 to 5% by mass of the metal particles.

By adding polyethylene glycol as a surfactant in the process of preparing a metal piece by ball milling, the specific surface area of the metal or alloy can be greatly increased at a low cost, and a large number of dislocations and defects are introduced, and the corrosion process of the metal or alloy is accelerated. Since the thickness of the flake metal powder can easily reach the nanometer order, the electrochemical potential generated during the corrosion process is strengthened, and the corrosion is further accelerated. In addition, some metal-soluble transition products are produced during the metal corrosion process, resulting in a continuous growth process of the surface nanosheets, forming a large number of interdigitated metal hydroxide nanosheets on the surface of the metal or alloy. It is advantageous to obtain multilayer self-supporting metal hydroxide and/or metal oxide nanosheets with superior performance.

The above multilayer self-supporting metal hydroxide and/or metal oxide nanosheets are used as catalytic, adsorption or energy storage materials.

The invention only uses the transition metal or its alloy powder as a raw material, and the aqueous solution is a solvent, and the material can be prepared on a large scale by the corrosion reaction of water on the metal. The preparation method is simple and easy to operate, green and environmentally friendly, does not require any chemical reagents, and utilizes the principle of metal corrosion to accelerate the corrosion process by utilizing the large specific surface area of the metal particles at the micro scale. At the same time, the high curvature of the small metal particles exacerbates the stress between the corrosion product (metal hydroxide) and the original metal particles, thereby ensuring the metal hydroxide and/or metal oxide nanosheets and metal surfaces generated by the corrosion. Uninterrupted separation. In addition, a partially soluble water-soluble transition product is produced during the metal corrosion process, resulting in a continuous growth process of the surface nanosheets, forming a large number of interdigitated metal hydroxides and/or metal oxide nanoparticles on the surface of the metal particles. sheet.

Example 1

1) Will be 30g The 300-mesh reduced cobalt powder and 0.2 g of polyethylene glycol and 40 stainless steel balls of 1 cm diameter were mixed and placed in a ball mill, ball milled at 300 rpm for half an hour, and then ball milled at 500 rpm for 5 hours to obtain a sheet. Cobalt powder

2) mixing the flake cobalt powder and 15 ml of deionized water, and letting stand at 20 to 25 ° C for 48 hours;

3) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting cobalt hydroxide/oxide nanosheets.

Fig. 1 is an electron micrograph of a cobalt powder raw material used in the present example, and it can be seen that the powder is a spherical powder having an average size of 1 μm.

Fig. 2 is an electron micrograph of the flake cobalt powder prepared in the present example.

3 is an electron micrograph of the cobalt hydroxide nanosheet prepared in the present embodiment. It can be seen that the self-supporting cobalt hydroxide nanosheet has a large gap between the sheet and the sheet, and the overall shape is good. The prepared cobalt hydroxide/oxide multi-stage nanosheet has an average thickness of 1 micrometer, a size of 10 to 100 micrometers, a cobalt metal sheet core thickness of less than 0.1 micrometer, and an average thickness of the cobalt hydroxide/oxide nanosheet. 5 nanometers.

4 is an X-ray diffraction spectrum of the cobalt hydroxide nanosheet prepared in the present embodiment. It can be seen that the self-supporting cobalt hydroxide nanosheet contains a large amount of metallic cobalt, and the core is an uncorroded metallic cobalt sheet. .

The cobalt hydroxide/oxide nanosheets prepared in this example were subjected to a current test to further characterize the energy storage characteristics of the nanosheets. The specific test method is as follows: the self-supporting metal hydroxide/oxide nanosheet prepared in Example 1 is dispersed in deionized water at a concentration of 2 mg/ml, and then 10 μl of the suspension is uniformly dropped at 0.07 cm ^{2 .} The glassy carbon electrode is equipped as a three-electrode system as a positive electrode, the counter electrode is a platinum wire, the reference electrode is a Hg/HgO electrode, and the electrolyte is a 1 mol/L potassium hydroxide solution, and the OER performance is tested by an electrochemical workstation. The scanning speed is 5mV/s, the accuracy is 1mV, and the voltage window is 0.3~1V. The self-supporting cobalt hydroxide/oxide nanosheet current-voltage curve prepared in Test Example 1 is shown in Fig. 11 (voltage is a standard hydrogen electrode voltage). It can be seen that the nanosheets have better electrocatalytic properties.

Example 2:

1) 15g 300 mesh reduced cobalt powder, 15g Reduced nickel powder less than 5 microns (Fig. 5) and 40 stainless steel balls of 1 cm diameter were mixed into a ball mill and ball milled at 500 rpm for 7 hours;

2) Adding 0.4 g of polyethylene glycol to the ball mill jar and ball milling for 30 hours at 300 rpm, and then ball milling for 3 hours at 500 rpm to obtain a cobalt nickel alloy sheet (Fig. 6);

3) mixing the cobalt-nickel alloy powder prepared by ball milling with 15 ml of deionized water, and letting it stand at 35 to 45 ° C for 24 hours;

4) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting cobalt nickel hydroxide/oxide nanosheets (Fig. 7).

The prepared cobalt hydroxide/oxide nanosheet has an average thickness of 200 nm, a size of 1 to 10 μm, a nickel-cobalt metal sheet core thickness of less than 20 nm, and a cobalt nickel hydroxide/oxide nanosheet average thickness of 5 Nano.

Example 3:

1) 10g 300 mesh reduced cobalt powder, 10g reduced nickel powder less than 5 microns, 10g Iron powder of less than 300 mesh and 40 stainless steel balls of 1 cm diameter were mixed and placed in a ball mill, and ball milled at 500 rpm for 3 hours;

2) Adding 0.15 g of polyethylene glycol to the ball mill jar and ball milling for 30 hours at 300 rpm, and then ball milling for 3 hours at 500 rpm to obtain a cobalt nickel iron alloy sheet;

3) mixing the cobalt-nickel alloy powder prepared by ball milling with 15 ml of deionized water, and letting it stand at 70-80 ° C for 5 hours;

4) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting cobalt nickel hydroxide/oxide nanosheets.

The prepared cobalt-nickel-iron hydroxide/oxide nanosheet has an average thickness of 2 μm and a size of 5 to 50 μm, and the core thickness of the cobalt-nickel-iron metal sheet is less than 100 nm, and the cobalt-nickel hydroxide/oxide nanosheet average The thickness is 20 nm.

Example 4:

1) 15g 300 mesh zinc powder, 15g Reduced nickel powder of less than 5 microns and 40 stainless steel balls of 1 cm diameter were mixed into a ball mill and ball milled at 500 rpm for 3 hours;

2) 0.8 g of polyethylene glycol was added to the ball mill jar and ball milled at 300 rpm for half an hour, and then ball milled at 500 rpm for 3 hours to obtain a nickel-zinc alloy sheet;

3) mixing the ball-milled nickel-zinc alloy powder with 15 ml of deionized water, and letting stand at 15 to 20 ° C for 48 hours;

4) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting nickel zinc hydroxide/oxide nanosheets.

The prepared nickel zinc hydroxide/oxide nanosheet has an average thickness of 1 micrometer and a size of 5 to 50 micrometers, a nickel-zinc metal foil core thickness of less than 100 nanometers, and an average thickness of the cobalt nickel hydroxide/oxide nanosheet. 10 nanometers.

Example 5:

1) 15g 300 mesh zinc powder, 15g 300 mesh copper powder and 40 stainless steel balls with a diameter of 1 cm were mixed and put into a ball mill, and ball milled at 500 rpm for 3 hours;

2) Adding 1.5 g of polyethylene glycol to the ball mill jar, ball milling at 300 rpm for half an hour, and then ball milling for 3 hours at 500 rpm to obtain a copper-zinc alloy sheet;

3) mixing the copper-zinc alloy powder prepared by ball milling with 15 ml of deionized water, and letting it stand at 15 to 20 ° C for 24 hours;

4) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting copper zinc hydroxide/oxide nanosheets.

The prepared copper zinc hydroxide/oxide nanosheet has an average thickness of 1 micrometer, a size of 10 to 100 micrometers, a copper-zinc metal foil core thickness of less than 100 nanometers, and an average thickness of the copper zinc hydroxide/oxide nanosheet. 5 nanometers.

Example 6

1) Will be 30g The 300-mesh reduced cobalt powder and 40 stainless steel balls with a diameter of 1 cm were mixed and placed in a ball mill, ball-milled at 300 rpm for half an hour, and then ball milled at 500 rpm for 5 hours to obtain micron-cobalt powder;

2) mixing micron cobalt powder and 15 ml of deionized water, and letting stand at 20 to 25 ° C for 48 hours;

3) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting cobalt hydroxide/oxide nanosheets.

Figure 8 is a micron cobalt powder prepared in this example.

Figure 9 is an electron micrograph of the cobalt hydroxide/oxide particles prepared in this example.

Figure 10 is an electron micrograph of a cross section of the cobalt hydroxide/oxide particles prepared in this example. It can be seen that there is a large amount of gap between the sheet and the sheet layer of the self-supporting cobalt hydroxide/oxide particles. The overall shape is good. However, compared to the sheet-like nanosheets, the core remains more and the specific surface area is smaller.

Comparative example 1:

The same as in Example 1, except that the flaky cobalt powder obtained by ball milling was reacted at 100 ° C for 2 h to prepare a nano material.

The results show that nanomaterials with self-supporting metal hydroxide and/or metal oxide nanosheets could not be prepared.

Example 7

1) The average size of 10g is 1 The μm cobalt powder was mixed with 5 ml of 1 M KOH solution (pH=14), and the reaction was allowed to stand at room temperature (22-28 ° C) for 48 hours;

2) Finally, the product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting cobalt hydroxide/oxide nanosheets.

The prepared cobalt hydroxide/oxide nanosheets have an average size of 1 μm and an average thickness of 5 The self-supporting nanosheet particle size is about 5 [mu]m.

Figure 12 is an electron micrograph of the cobalt powder raw material used in the present example, and it can be seen that the powder is a spherical powder having an average size of 1 Mm. Figure 13 is an electron micrograph of the cobalt hydroxide/oxide nanosheet prepared in this example. It can be seen that there is a large amount of gap between the sheet and the layer of the self-supporting cobalt hydroxide/oxide nanosheet. The overall shape is good. Figure 14 is a cross-sectional view of the sample with the metal core inside it clearly visible.

The cobalt hydroxide/oxide nanosheets prepared in this example were subjected to a current test to further characterize the energy storage characteristics of the nanosheets. The specific test method is:

1) The self-supporting metal hydroxide and/or metal oxide nanosheet prepared in Example 7 was dispersed in deionized water at a concentration of 2 mg/ml;

2) 10 μl of the suspension was evenly dropped on a 0.07 cm ² glassy carbon electrode as a positive electrode as a three-electrode system, the counter electrode was a platinum wire, the reference electrode was a Hg/HgO electrode, and the electrolyte was 1 mol/L. The potassium hydroxide solution was tested for its OER performance using an electrochemical workstation with a scan speed of 5 mV/s, an accuracy of 1 mV, and a voltage window of 0.3 to 1 V.

The self-supporting cobalt hydroxide/oxide nanosheet current-voltage curve prepared in Test Example 7 is shown in Fig. 20 (voltage is a standard hydrogen electrode voltage). It can be seen that the nanosheets have better electrocatalytic properties.

Example 8

1) The average size of 10g is 100 The iron powder of nm (Fig. 15) is mixed with 5 ml of deionized water, and the reaction is allowed to stand at 70 to 80 ° C for 5 hours;

2) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting iron hydroxide/oxide nanosheets.

The prepared iron hydroxide/oxide nanosheets have an average size of 200 nm, an average thickness of 5 nm, and a self-supporting nanosheet particle size of about 1 Mm.

Example 9

1) The average size of 10g is 20 Mixing μm of nickel-cobalt alloy powder with 5 ml of deionized water, and letting the reaction stand at 30-450 ° C for 36 hours;

2) The product was washed and dried at 60 ° C for 9 hours to obtain a nanomaterial having self-supporting nickel cobalt hydroxide/oxide nanosheets (Fig. 16).

The prepared nickel cobalt hydroxide/oxide nanosheets have an average size of 1 μm, an average thickness of 5 nm, and a self-supporting nanosheet particle size of about 3 Mm.

Example 10:

1) Will be 10g 300 mesh nickel-iron-cobalt alloy powder (molar ratio 1:1:1) and 50 ml of deionized water were mixed, and the reaction was allowed to stand at 15 to 20 ° C for 48 hours;

2) The product was washed and dried at 70 ° C for 8 hours to obtain a nanomaterial having self-supporting nickel iron cobalt hydroxide/oxide nanosheets (Fig. 17).

The prepared nickel iron hydroxide/oxide nanosheets have an average size of 3 μm, an average thickness of 50 nm, and a self-supporting nanosheet particle size of about 10 Mm.

Example 11

1) The average size of 10g is 10 Μm of cobalt powder (Figure 18) and 50 ml of pH = 10 (KOH adjusted) deionized water, heated to 60 ° C, stirred for 2 hours;

2) The product was washed and dried at 70 ° C for 8 hours to obtain a separated cobalt hydroxide/oxide nanosheet (Fig. 19).

The prepared cobalt hydroxide/oxide nanosheets had an average size of 200 nm and an average thickness of 20 nm. The Raman map (Fig. 21) shows that the material is Co ₃ O ₄ (having 481, 519, 616, 686, which are four characteristic peaks).

Comparative example 2:

Same as Example 7, except that the reaction temperature was 100 °C.

The results showed no significant nanostructures in the obtained product.

Claims (19)

 A nano material having self-supporting metal hydroxide and/or metal oxide nanosheets, the nano material having a metal core, and the metal core having a particle size of 0.05 μm to 20 Μm, the surface of the metal core is a self-supporting structure formed by corresponding metal hydroxide and/or metal oxide nanosheets. The nanomaterial according to claim 1, wherein the metal core is in the form of particles or flakes. The nanomaterial according to claim 2, wherein the granular metal core has a particle diameter of 0.05 μm to 10 μm; the sheet metal core has a particle size of 0.05. Mm ~ 10 μm. The nanomaterial according to claim 2 or 3, wherein the sheet metal core has an average thickness of 0.01 to 1 μm. The nanomaterial according to any one of claims 1 to 4, wherein the nanosheet has an average thickness of from 1 nm to 50 nm. The nanomaterial according to any one of claims 1 to 5, wherein the nanosheet has a length of from 100 nm to 100 μm. The nanomaterial according to any one of claims 1 to 4, wherein the metal is an alloy of a transition metal element or a transition metal. The nanomaterial according to claim 7, wherein the metal is at least one selected from the group consisting of cobalt, nickel, copper, iron, zinc, manganese, and molybdenum, or an alloy formed of at least two metal elements. A method for preparing a nano material having a plurality of layers of self-supporting metal hydroxide and/or metal oxide nanosheets, comprising the steps of: 1) The average particle size is from 1 μm to 100 The metal piece or metal particle of μm is mixed with the aqueous solution, and the reaction is sufficient at not higher than 80 ° C; 2) After the reaction is completed, it is filtered, washed, and dried at not higher than 100 ° C to obtain a nanomaterial having a self-supporting metal hydroxide and/or metal oxide nanosheet. The process according to claim 9, wherein the pH of the aqueous solution is from 7 to 14. The production method according to claim 9 or 10, wherein the metal is an alloy formed of a transition metal element or a transition metal. The production method according to claim 11, wherein the metal is at least one selected from the group consisting of cobalt, nickel, copper, iron, zinc, manganese, and molybdenum, or an alloy of at least two metal elements. The preparation method according to any one of claims 9 to 12, characterized in that the particle diameter of the particulate metal core after the reaction is 0.05 μm to 10 Mm; the flaky metal core has a particle size of 0.05 μm to 10 μm. The production method according to any one of claims 9 to 13, characterized in that the average thickness of the sheet-like metal core after the completion of the reaction is 0.01 to 1 μm. The preparation method according to any one of claims 9 to 14, characterized in that the average thickness of the nanosheets after the end of the reaction is from 1 nm to 50 nm. The production method according to any one of claims 9 to 15, wherein the length of the nanosheet after the reaction is completed is from 100 nm to 100 μm. The preparation method according to any one of claims 9 to 12, wherein the metal sheet is prepared by mixing metal particles having an average particle size of from 1 to 50 μm and a surfactant, and ball milling to obtain a metal piece. The preparation method according to claim 13, wherein the surfactant is polyethylene glycol in an amount of from 0.5 to 5% by mass based on the mass of the metal particles. Use of a nanomaterial having self-supporting metal hydroxide and/or metal oxide nanosheets as a catalytic, adsorbing or energy storage material, characterized by: nanoparticles with self-supporting metal hydroxides and/or metal oxide nanosheets The material is prepared by any one of claims 1 to 8, or by the preparation method according to any one of claims 9 to 18.