KR101505285B1 - Manufacturing method of oxygen reduction reaction catalysts and catalysts thereof, Cathode using oxygen reduction reaction catalysts - Google Patents

Abstract

The present invention relates to a method for producing an oxygen reduction catalyst, a catalyst therefor, and electrodes for metal-air batteries using the same, wherein a transition metal ion is adsorbed onto commercially available melamine foams and carbonized, The present invention relates to a method for producing an oxygen-containing catalyst capable of economically producing an oxygen-containing catalyst capable of maximizing the effect of accelerating an oxygen reduction reaction by supporting black, an oxygen-containing catalyst for metal- .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an oxygen reduction reaction catalyst,

The present invention relates to a method for producing an oxygen reduction catalyst, a catalyst therefor, and an electrode for a metal-air battery using the catalyst. More particularly, the present invention relates to a carbon- And a method for preparing the same. The present invention also relates to a catalyst for preparing the catalyst and a metal-air battery electrode using the same.

Metal-air cells are becoming increasingly popular as the demand for fossil fuel depletion and environmentally friendly, highly efficient alternative energy is increasing. In particular, most of the materials used are environmentally friendly, inexpensive, and have a lot of potential for future development, so it is possible to design a very high capacity battery in the future.

Zinc-air batteries, one of the metal-air battery types, are currently used in hearing aids and small-capacity devices, and their secondary cell applications are underway. Zinc-air batteries use zinc (Zn) powder or zinc plate for the negative electrode. In the case of zinc powder, a gelling agent or the like may be mixed and kneaded in an aqueous alkali solution, which is an electrolytic solution, to enhance the moldability of the zinc powder.

The anode of the zinc-air battery includes a catalyst layer, a diffusion layer, and a hydrophobic membrane. The catalyst layer may be composed of a catalyst, a carrier for supporting the catalyst, and a conductive agent. The diffusion layer may include activated carbon, A hydrophobic binder such as polytetrafluoroethylene (PTFE) or the like is used in order to maintain the hydrophobicity of the air electrode. It can be used as a diffusion layer by pressing it on a metal screen or a metal foam, or carbon paper, carbon fiber, or the like can be used.

Zinc-air cells are composed of a zinc gel or zinc plate, which is an anode, and a polypropylene (PP), a nylon filter, a polyethylene (PE), a polymer separator and an ion permeable separator separating the anode and cathode. A catalytic layer containing carbon and catalyst to cause a reaction, a diffusion layer made of carbon and a binder, a carbon species or carbon fiber, a metal layer having electron conduction, A PTFE (polytetraflouroethylene) hydrophobic membrane configured to extend the permeable membrane, and a diffusion layer for uniform diffusion of air from the outside.

The following Reaction Scheme 1 is one example of the case where zinc is used as a negative electrode in a metal-air battery cell. It is a matter of course that a reaction formula may be formed in the form of a variety of metal-air batteries when another metal is used instead of zinc.

Scheme 1

Anode: O ₂ + 2H ₂ O + 4e → 4OH ^-

^{Cathode: 2Zn + 4OH - → 2ZnO +} 2H 2 O + 4e -

The overall reaction: 2Zn + O ₂ → 2ZnO

Since zinc-air cells use atmospheric oxygen as a cathode active material, there is a great advantage that the use of a lightweight carbon cathode can reduce the weight of the battery and enable a higher energy density than a lithium-ion battery do.

However, since the oxygen reduction reaction is very slow compared to the oxidation rate of the metal cathode, the reaction of the whole battery depends on the rate of the oxygen reduction reaction of the cathode (anode).

Therefore, an effective oxygen reduction catalyst is required for a zinc-air battery having a high output and a high energy density. Carbon nanotubes and graphene, which are very complicated in manufacturing process, are mainly used for the catalyst support. However, an expensive noble metal catalyst using such a catalyst carrier is excellent in performance but is very expensive, so that economical efficiency, one of the greatest advantages of zinc-air batteries, is lost. In general, researches on catalysts which do not include metal oxides (manganese, cobalt, iron, etc.) and metal which is a substance in which nitrogen is substituted on the carbon face are actively studied in the case of a zinc- Has been pointed out that the process of substituting nitrogen on the carbon surface is very complicated and therefore difficult to synthesize.

Korean Patent Publication No. 10-2010-0122706 (Nov. 23, 2010) Korean Patent Laid Open Publication No. 10-2011-0105051 (September 26, 2011) Korean Patent Registration Registration No. 10-0875105 (December 15, 2008)

In order to solve the above problems, an object of the present invention is to adsorb transition metal ions onto a commercial melamine foam carrier, to carbonize the melamine foam carrier, to support carbon black in the porous structure of the carbonized melamine foam carrier, Which can maximize the effect of accelerating the oxygen reduction reaction, and to provide an oxygen reaction catalyst for the metal-air battery produced therefrom.

Another object of the present invention is to provide an electrode for a metal-air battery using the composite catalyst.

The present invention provides a carbonized melamine foam carrier comprising adsorbed iron ions, the carbonized melamine foam carrier comprising: And a carbon black carried on the porous structure of the carbonized melamine foam carrier. The present invention also provides an oxygen reduction catalyst comprising the carbon black supported on the porous structure of the carbonized melamine foam carrier.

In a preferred embodiment, the oxygen reduction catalyst may comprise 50 to 80 wt% of a carbonized melamine foam carrier containing the adsorbed iron ion and 20 to 50 wt% of carbon black.
In a preferred embodiment, the iron ions may comprise 1-10 wt%, based on the total weight percent of the carbonized melamine foam.
In a preferred embodiment, the iron ion may be provided from an aqueous solution of at least one iron selected from FeCl ₂ .4H ₂ O, FeCl ₃ .6H ₂ O, and Fe (NO ₃ ) ₃ .6H ₂ O.
In a preferred embodiment, the carbon black may be at least one selected from Denka Black, Acetylene Black, Ketjen Black, Furnace Black, Thermal Black, and Lamp Black.

The present invention also provides, in another embodiment,
And an electrode for a metal-air battery using the oxygen reduction catalyst, wherein the oxygen reduction catalyst is mixed with activated carbon and a binder.

In a preferred embodiment, the negative electrode of the metal-air battery may be zinc or lithium.

The present invention also provides, in another embodiment,
a) preparing a melamine foam carrier;
b) preparing an aqueous solution of ferric ion complex;
c) impregnating the melamine foam carrier with an iron ion complex aqueous solution;
d) drying the melamine foam carrier impregnated with the iron ion complex aqueous solution;
e) carbonizing the dried melamine foam carrier by heat treatment in an inert gas atmosphere to produce a carbonized melamine foam carrier containing the adsorbed iron ion;
f) mixing the carbonized melamine foam carrier containing adsorbed iron ions with carbon black to produce a final catalyst by supporting the carbon black on the porous structure of the carbonized melamine foam carrier; and And a method for producing an oxygen reduction catalyst.

In a preferred embodiment, the step f) comprises: 50 to 80 wt% of a melamine foam carrier in which iron ions are carbonized; And 20 to 50 wt% of carbon black.
In a preferred embodiment, the carbonized melamine foam carrier may contain 1 to 10 wt% of iron ions based on the total weight% of the carbonized melamine foam carrier.
In a preferred embodiment, the step d) may dry the impregnated melamine foam carrier for at least 24 hours in a temperature range of 40-50 degrees Celsius.
In a preferred embodiment, the step e) may carbonize the melamine foam carrier containing the dried adsorbed iron ion in an inert gas atmosphere at 600 to 900 degrees Celsius for 1 to 2 hours.
In a preferred embodiment, the iron ion complex aqueous solution may be at least one selected from FeCl ₂ .4H ₂ O, FeCl ₃ .6H ₂ O, and Fe (NO ₃ ) ₃ .6H ₂ O.
In a preferred embodiment, the carbon black may be at least one selected from Denka Black, Acetylene Black, Ketjen Black, Furnace Black, Thermal Black, and Lamp Black.

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

As described above, the present invention is a simple one-pot reaction in which transition metal ions are introduced into melamine foams which are widely used in the market, based on a water-soluble solution, and burned under a nitrogen atmosphere at a high temperature, By making a carbon-nitrogen-transition metal as a reaction site and physically putting carbon black, which is a conductive carbon, into a large three-dimensional hole of a carbonized melamine foam, an oxygen reduction catalyst is produced, The present invention is a useful invention having a merit that mass production is possible and the synthesis process is very simple and the produced catalyst has similar performance as a platinum catalyst of a noble metal.

FIG. 1 is a flowchart showing a process for producing a melamine foam and a Ketjen black composite catalyst functionalized with iron ions according to an embodiment of the present invention.
FIG. 2 is a SEM image of a catalyst composite prepared according to an embodiment of the present invention (melamine foam (left) functionalized with iron ion (left), melamine foam prepared with ketone black and carbon black composite catalyst (right)
3 is a comparative graph of a catalyst prepared in an oxygen saturated atmosphere according to an embodiment of the present invention by linear sweep voltammetry.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention relates to a method for adsorbing a transition metal ion on a melamine foam having a porous structure which naturally contains a large amount of nitrogen substituted in a carbon skeleton and has a three-dimensionally large pore structure and then burns the metal ion at an elevated temperature in an inert gas atmosphere, A carbonized melamine foam containing a large amount of carbon-nitrogen-transition metal as a reaction site is prepared, and the prepared foam and carbon black are simply physically mixed to produce a catalyst maximizing the effect of accelerating the oxygen reduction reaction.

That is, based on a commercially available melamine foam and a polymer containing nitrogen from the beginning, a simple circle for carbonization by additionally introducing transition metal ions to maximize the effect of the catalyst and burning it in an inert gas atmosphere at a high temperature, The present inventors have developed a method using a one-pot reaction to maximize the problem of synthesis and the effect of the catalyst, and furthermore, since the three-dimensional structure unique to the melamine foam remains after the carbonization process, Is a method for producing an effective oxygen reduction catalyst by additionally introducing carbon black which is inexpensive and already widely used conductive carbon. The production method of the present invention for producing such a catalyst,

a) preparing a melamine foam carrier;
b) preparing an aqueous solution of ferric ion complex;
c) impregnating the melamine foam carrier with an iron ion complex aqueous solution;
d) drying the melamine foam carrier impregnated with the iron ion complex aqueous solution;
e) carbonizing the dried melamine foam carrier by heat treatment in an inert gas atmosphere to produce a carbonized melamine foam carrier containing the adsorbed iron ion;
f) mixing the carbonized melamine foam carrier containing the adsorbed iron ions with carbon black to form carbon black on the porous structure of the carbonized melamine foam carrier to produce a final catalyst.

delete

delete

delete

delete

delete

The step of preparing the melamine foam carrier a) and the step of preparing the aqueous solution of the iron ion complex b) are not related to each other since they are not related to each other.

The manufacturing method after the step c) may be performed in a sequential order.

The melamine foam carrier used in the home is often used in cleaning or other cleaning of tableware or the like in home, and it contains a large amount of nitrogen substituted in the carbon skeleton naturally, its structure is three-dimensionally formed, The melamine foam pores have a thickness of about 100 microns. In the examples of the present invention, a commercially available magic block manufactured by BASF, Germany or the like was used. Of course, you can use any melamine foam.

The melamine constituting such a melamine foam carrier is a heterocyclic amine, which is an organic base and a trimer of cyanamide. 66% of the mass is made of nitrogen, and when mixed with resin, it has fire-proof property.

Usually, the oversized standard melamine foam carrier has a size of about 110 mm (width) * 270 mm (length) * 40 mm (height), which can be cut to about 50 mm * 50 mm * 40 mm. However, it should be understood that these numerical values are illustrative and that they can be cut to any desired size.

The iron ion is an aqueous solution of iron ion complex. As the iron ion complex aqueous solution, any one or more selected from among FeCl ₂ .4H ₂ O, FeCl ₃ .6H ₂ O and Fe (NO ₃ ) ₃ .6H ₂ O can be used.

The concentration of the iron ion complex aqueous solution is preferably 5 mM to 20 mM. If the concentration is lower than the lower limit, the adsorption rate of the iron ions is low and the catalytic efficiency is lowered. If the concentration is higher than the upper limit value, the iron ions are adsorbed and no longer adsorbed.

For reference, in the case of iron ion, 1.1 g of melamine foam is immersed in 50 mL of 5 mM FeCl ₂ · 4H ₂ O aqueous solution, and absorption is fully performed.

That is, the mixing ratio (wt%) between the iron ion complex and the melamine foam carrier contained in the aqueous solution of 5 mM to 20 mM FeCl ₂ .4H ₂ O is 0.56 to 2.25: 1.

At such a value, iron ions capable of optimally exhibiting the catalytic performance of the melamine foam carrier of the present invention are impregnated. In the case of the impregnation rate, the amount of iron ion is 1 to 10 wt% based on the total weight% of the carbonized melamine foam carrier. If more or less than this amount is included, the performance of the catalyst deteriorates.

In the step of drying the melamine foam carrier, the iron ion complex impregnated at room temperature (25 ° C) is impregnated with a melamine foam carrier, and then the impregnated melamine foam carrier is immersed in a temperature range of 40 to 50 degrees Celsius Allow to dry thoroughly for more than 24 hours. In such a temperature range, it is dried sufficiently without changing physical properties upon drying.

If it is burned at high temperature (900 degrees Celsius) in an inert gas atmosphere without being fully dried, the whole melamine foam carrier may burn out.

The step of carbonizing the dried melamine foam carrier by heat treatment in an inert gas

It should be burned in an inert gas atmosphere such as in a nitrogen atmosphere or an argon atmosphere. When burned in the air, it is not converted to absolute carbon, it is converted to CO _2, and it is blown into the atmosphere.

The inert gas includes not only an inert gas belonging to group 18 of the periodic table but also a gas which does not participate in the reaction under the above conditions such as nitrogen.

In addition, when the heat treatment temperature is increased and the heat treatment time is prolonged, the content of N (nitrogen) is generally decreased. If the content of N is decreased, the place where the Fe ion can adsorb is reduced, so that ORR (Oxygen Reduction Reaction) It will fall. Therefore, the preferred temperature is 600 to 900 degrees Celsius, which is the best carbonization performance. In addition, the burning time is 1 to 2 hours in all the carbonization is done.

In the step of mixing the carbonized melamine foam carrier having the porous structure with the carbon black at a predetermined ratio to prepare the final catalyst, the mixing ratio of the carbonized melamine foam as the support to the carbon black supported thereon is The ratio of 50 to 80 wt% carbonized melamine foam and 20 to 50 wt% carbon black on a weight% basis. The reason for this numerical limitation is that when the amount of carbon black is less than 20 wt%, the conductivity is lowered and the performance is not good. When the amount of carbon black is more than 50 wt%, the amount of carbon black becomes too large, Because it shows degraded performance.

The carbon black may be at least one selected from Denka black, acetylene black, Ketjen black, furnace black, thermal black and lamp black.

In one embodiment, the carbon black carbon used in the present invention is a commercially available conductive material, Ketjenblack 600-JD, which is much cheaper than expensive carbon nanotubes.

A temporary example of the carbonization step and the catalyst preparation step may be a step of grinding the carbonized melamine support into a powder form, and mixing the carbonized powder with 20 to 50 wt% of carbon black to prepare a final catalyst.

A method of applying the shape (lump or powder) of the catalyst thus prepared to electrodes for metal-air batteries will be described below. Hereinafter, the metal-air battery in the present invention may be a zinc-air battery or a lithium-air battery using zinc or lithium as a metal constituting the cathode.

Basically, the manufacturing method of the air electrode comprises mixing the active carbon + the composite catalyst + binder according to the present invention at a predetermined ratio, kneading, and then pushing the mixture.

That is, in the method of manufacturing a metal-air battery air electrode according to the present invention,

1. Sludge preparation stage

The composite catalyst prepared by the catalyst preparation method of the present invention may be prepared by mixing a carbon support capable of supporting the composite catalyst with a binder.

As the binder, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), NAFION, or the like can be used as a binder.

The viscosity of the slurry varies depending on the type and amount of the binder and the solvent (solvent is used to dissolve the binder, which is then volatilized and blown off, such as isopropyl alcohol). Depending on the viscosity of the slurry, the catalyst layer is applied to the diffusion layer The method can be different.

Here, the carbon carrier generally uses a spherical carbon carrier such as activated carbon, but any carbon carrier capable of forming a structure capable of introducing air and having conductivity can be used.

At this time, the mixing ratio between the composite catalyst of the present invention, carbon and the carrier binder may be in accordance with a conventional electrode production example.

2. Catalyst layer formation step

Hereinafter, various methods of forming the catalyst layer constituting the air electrode are shown. The slurry may be formed on the air electrode (the first diffusion layer of the air electrode) by any one of the methods listed. Other methods known to those skilled in the art are also possible.

(One). A method of forming a catalyst layer on a cathode by using a roll press or a hot press.

(2). A method of forming a catalyst layer by using Doctor blade or Roller coater.

(3). A method of forming a catalyst layer using an electrospinning method.

(4). A method of forming a catalyst layer using an electrospray method.

The following is a preferred embodiment of the present invention. The following examples illustrate preferred embodiments of the present invention, but the present invention is not limited by these examples.

(Example 1) Catalyst production method

FIG. 1 is a flowchart illustrating a process for producing a melamine foam and a Ketjen black composite catalyst functionalized with iron ions according to an embodiment of the present invention. Referring to FIG. According to an embodiment of the present invention,

1. Cut melamine foam (BASF), which is widely used in commerce, into about 50mm * 50mm * 40mm.

2. Prepare a 10 mM FeCl ₂ .4H ₂ O aqueous solution.

3. Immerse melamine foam in the amount of 50 ml of 2 times of aqueous solution.

4. Dry the wet melamine foam with an aqueous solution of iron ion at 40 ° C for 24 hours.

5. Heat treatment at 900 ° C for 2 hours in a tube furnace under a nitrogen atmosphere.

6. Mixing 0.3 g of the carbonized melamine foam carrier and 0.3 g of Ketjenblack to prepare the final catalyst.

(Test Example 1)

FIG. 2 is a SEM photograph of a catalyst composite prepared according to an embodiment of the present invention. The left photograph shows a carbonized melamine foam carrier functionalized with iron ions, and the right photograph shows the prepared melamine foam carrier and a Ketjen black carbon composite catalyst Fig.

SEM pictures show a carbonized melamine foam carrier (left) and a ketamine block (right) mixed in the carbonized melamine foam carrier.

(Test Example 2)

3 is a comparative graph of a catalyst prepared in an oxygen saturated atmosphere according to an embodiment of the present invention by linear sweep voltammetry.

The current value was measured by changing the scanning voltage to about 10 mV / s from 0 V to 1.0 V. It can be seen that the larger the absolute value of the current is, the higher the electrochemically better performance, the higher the performance of the catalysts of the composite catalyst using the Ketjenblack according to the present invention.

It can be seen that the platinum catalyst has similar performance to the catalyst of the present invention.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims and their equivalents. Of course, such modifications are within the scope of the claims.

Claims (18)

A carbonized melamine foam carrier containing adsorbed iron ions; And carbon black supported on the porous structure of the carbonized melamine foam carrier.
The method according to claim 1,
Wherein the oxygen reduction reaction catalyst comprises 50 to 80 wt% of a carbonized melamine foam carrier containing the adsorbed iron ion and 20 to 50 wt% of carbon black.
The method according to claim 1,
Wherein the iron ion is contained in an amount of 1 to 10 wt% based on the total weight% of the carbonized melamine foam.
delete The method according to claim 1,
Wherein the iron ion is provided from an aqueous solution of at least one iron selected from FeCl ₂ .4H ₂ O, FeCl ₃ .6H ₂ O and Fe (NO ₃ ) ₃ .6H ₂ O.
delete The method according to claim 1,
Wherein the carbon black is at least one selected from Denka black, acetylene black, Ketjen black, furnace black, thermal black, and lamp black.
An electrode for a metal-air battery using an oxygen reduction catalyst, wherein the oxygen reduction catalyst according to any one of claims 1, 2, 3, 5 and 7 is mixed with activated carbon and a binder.
The method of claim 8,
The electrode for a metal-air battery using the oxygen reduction catalyst, wherein the metal-air battery is zinc or lithium.
a) preparing a melamine foam carrier;
b) preparing an aqueous solution of ferric ion complex;
c) impregnating the melamine foam carrier with an iron ion complex aqueous solution;
d) drying the melamine foam carrier impregnated with the iron ion complex aqueous solution;
e) carbonizing the dried melamine foam carrier by heat treatment in an inert gas atmosphere to produce a carbonized melamine foam carrier containing the adsorbed iron ion;
f) mixing the carbonized melamine foam carrier containing adsorbed iron ions with carbon black to produce a final catalyst by supporting the carbon black on the porous structure of the carbonized melamine foam carrier; and A method for producing an oxygen reduction catalyst.
The method of claim 10,
Wherein the step (f) comprises: 50 to 80 wt% of a melamine foam carrier having iron ions carbonized; And 20 to 50 wt% of carbon black.
The method of claim 10,
Wherein the carbonized melamine foam carrier comprises 1 to 10 wt% of iron ions based on the total weight% of the carbonized melamine foam carrier.
The method of claim 10,
Wherein the impregnated melamine foam carrier is dried for at least 24 hours in a temperature range of 40 to 50 degrees Celsius.
The method of claim 10,
Wherein the step (e) comprises carbonizing the melamine foam carrier containing the dried adsorbed iron ions in an inert gas atmosphere at 600 to 900 ° C. for 1 to 2 hours.
delete The method of claim 10,
Wherein the iron ion complex aqueous solution is at least one selected from FeCl ₂ .4H ₂ O, FeCl ₃ .6H ₂ O, and Fe (NO ₃ ) ₃ .6H ₂ O.
delete The method of claim 10,
Wherein the carbon black is at least one selected from Denka black, acetylene black, Ketjen black, furnace black, thermal black, and lamp black.

Images