KR101342888B1 - Magneli Phase Titanium Oxide with High Specific Surface Area and the Fabrication Method Thereof - Google Patents

Abstract

The present invention relates to magellitic titanium oxide, and in detail, the magellitic titanium oxide according to the present invention has a specific surface area of 3 to 50 m ² / g, is characterized by containing nanopores, 35 wt% The above metal is characterized in that it is a magnetite phase titanium oxide to be loaded.

Description

Magnetic Phase Titanium Oxide with High Specific Surface Area and the Fabrication Method Thereof}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to large-area magenta-titanium oxide, and more particularly, to a magelli- tanite oxide which has a very large specific surface area and is easy to support a large amount of catalyst metal, and thus is suitable as a catalyst metal support of a fuel cell.

The demand for energy is increasing worldwide due to industrial development and population growth, but the production of oil and natural gas, the main energy sources, is expected to decrease gradually from about 2020. With the depletion of fossil fuels, there is an urgent need for research and development on alternative clean energy sources that do not pollute the environment.

In addition, the Kyoto Protocol was adopted in 1997 to ratify GHG emissions, which has been ratified by 119 countries, including Korea.

The technology that uses various natural resources such as solar heat, wind power and hydrogen energy as the energy source is being researched and developed, but unlike the existing thermal power generation, the thermodynamic limitation (Carnot efficiency) is not limited to the direct power generation without the combustion process or mechanical work. It does not receive power, has high power generation efficiency, does not emit air pollutants (NOx), sulfur compounds (SOx), etc., and can reduce CO ₂ emissions. Type power generation method is possible, and the field of medium and large power generation system of 100 ㎾ ~ 10 ㎿ class, small household power system of 1 ㎾ ~ 10 ㎾ class, automotive auxiliary power source, mobile power of several W ~ ㎾ class Fuel cell technology has been spotlighted as an alternative clean energy due to its ability to easily adjust power generation capacity.

A fuel cell is a device for directly converting chemical energy into electrical energy by reacting fuel gas such as hydrogen (H ₂ ) with oxygen (O ₂ ), and a fuel electrode and an air electrode are generally formed.

In the anode, hydrogen cations and electrons are generated by a catalytic reaction, and the hydrogen cations generated therein move through the electrolyte to the cathode, and electrons move from the anode to the cathode along an external circuit. In addition, in the cathode, water is generated by the reaction of hydrogen cations that have passed through the electrolyte and electrons that have moved along the external circuit with oxygen. At this time, a predetermined potential difference occurs between the fuel electrode and the air electrode.

Such fuel cells can be classified into various types according to the type of electrolyte used and operating temperature, but can obtain a high current density at a relatively low temperature of 100 ° C. or lower, and has an excellent energy conversion efficiency compared to other fuel cells. Polymer Electrolyte Membrane Fuel Cell (PEMFC), which uses hydrogen directly as a fuel, is attracting attention as a power source for automobiles, household power generation, and mobile devices.

However, the biggest problem in commercializing such a polymer electrolyte fuel cell is that the performance of the catalyst gradually decreases with a long time operation or start / stop repetition, thereby degrading the performance of the polymer electrolyte fuel cell. Such a decrease in performance is reported to be due to the decrease in the surface area of the platinum catalyst with the operation of the fuel cell.

In general, a polymer electrolyte fuel cell catalyst is used in the form of Pt / C on which a nano-sized platinum is supported on a carbon support having a high active area.

However, the polymer electrolyte fuel cell operates under conditions where carbon corrosion is likely to occur, such as high anode potential, low pH, and high oxygen concentration. Accordingly, in the case of the carbon-based support, while the polymer electrolyte fuel cell is operated, carbon is oxidized in the form of CO or CO ₂ to cause corrosion of the carbon supporting the catalyst, thereby reducing the active area of platinum. The problem of deterioration of fuel cell life due to deterioration of performance and reduction of durability occurs.

In order to improve this, as a new support to replace the carbon, a study on the support of the graphitized carbon, metal oxide-based support, and among them, the Magelli phase has better electrical conductivity than carbon and high durability even at high voltage operation A study to use Titanium Oxide (MPTO) Magneli Phase Titanium Oxide (MPTO) as a catalyst support (T. Ioroi, Z. Siroma, N. Fujiwara, S. Yamazaki, K. Yasuda, Electrochem. Commun. 7 (2005) 183 .; T. Ioroi, H. Senoh, S. Yamazaki, Z. Siroma, N. Fujiwara, K. Yasuda, J. Electrochem. Soc. 155 (2008) B321.).

However, in the case of the magnetellitic titanium oxide support, it has a very small specific surface area of 0.1 to 1.5 m ² / g, which makes it difficult to support a large amount of catalyst on the support. The maximum catalyst metal loading reported so far is less than 10 wt%, and the catalyst layer becomes relatively thick and the gas inlet diffusion distance becomes longer when the catalyst is supported with a lower loading, which decreases the performance and durability by increasing the gas diffusion resistance. There is a problem that occurs, and still have a technical limit to be applied to a fuel cell.

T. Ioroi, Z. Siroma, N. Fujiwara, S. Yamazaki, K. Yasuda, Electrochem. commun. 7 (2005) 183. T. Ioroi, H. Senoh, S. Yamazaki, Z. Siroma, N. Fujiwara, K. Yasuda, J. Electrochem. Soc. 155 (2008) B321.

The present invention has been made to solve the above-described problems, and in detail, an object of the present invention is to provide a magnetic phase titanium oxide (Magneli Phase Titanium Oxide) having a very large specific surface area and a manufacturing method thereof, and a fuel cell It is to provide a magnetite-like titanium oxide and a method for producing the same as a support for supporting a catalytic metal of.

The present invention provides a magnetic phase titanium oxide (Magneli Phase Titanium Oxide), characterized in that, the magnetic phase titanium oxide according to the invention is 3 to 50 m ² / g, more specifically 10 to 20 m ² / g of It is characterized by a very large specific surface area.

The titanium oxide according to the present invention contains Ti ₄ O ₇ and Ti ₅ O ₉ , more particularly, the titanium oxide is 80 wt% or more, and more particularly 90 wt% to 98 wt% of Ti ₄ O ₇ and Ti ₅ O ₉ is contained.

Titanium oxide according to the present invention, together with Ti ₄ O ₇ and Ti ₅ O ₉ , Ti _k O _{2k- (1 + 2l)} (natural number of 4≤k≤10, natural number of 1≤l≤ (k-1)) It is characterized by further containing the stoichiometric titanium oxide.

Titanium oxide according to the present invention is characterized in that the nano pores are formed, the average diameter of the nano pores is characterized in that 10 to 20 nm.

More specifically, the titanium oxide according to the present invention is characterized by having a surface area with a large number of pores, and based on the radius (R) of the titanium oxide particles, the thickness of the surface area is characterized in that 10 to 40%. have.

The titanium oxide according to the present invention is characterized in that the metal loading is more than 35 wt%, the metal includes a catalytic metal used in the fuel cell.

The present invention provides a catalyst for a fuel cell containing the above-mentioned magneto-type titanium oxide, and provides a fuel cell equipped with the catalyst for the fuel cell.

Magnetic phase titanium oxide according to the present invention has the advantage of having an extremely high specific surface area, has the advantage of loading more than 35 wt% metal, has excellent electrical conductivity, very durable at high voltage, high corrosion under oxygen conditions It has resistance, can be used as a catalyst metal support in fuel cells by replacing the conventional carbon-based, it is possible to manufacture a thin catalyst layer has the advantage of preventing the increase in gas diffusion resistance.

1 is a diagram showing the X-ray diffraction results of the magneto phase titanium oxide according to the present invention,
2 is a view showing the nitrogen adsorption and desorption results and pore distribution of magellitic titanium oxide according to the present invention,
3 is a transmission electron micrograph of the magneto-type titanium oxide according to the present invention,
4 is another transmission electron micrograph of the magneto-type titanium oxide according to the present invention,
5 is a scanning electron micrograph of the magellitic titanium oxide according to the present invention,
6 is a scanning electron micrograph of a commercially available magenta-type titanium oxide.

Hereinafter, the magellitic titanium oxide of the present invention will be described in detail with reference to the accompanying drawings. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the following drawings may be exaggerated in order to clarify the spirit of the present invention. Also, throughout the specification, like reference numerals designate like elements.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

Applicant has made numerous experiments and efforts to solve the problem that Magneti Phase Titanium Oxide is difficult to be used as a fuel cell catalyst due to its small specific surface area even though it has excellent electrical conductivity and high high voltage durability. As a result, it has been possible to develop and file a magnetellitic titanium oxide having a very large specific surface area of 3 to 50 m ² / g, more particularly 10 to 20 m ² / g.

Magellitic titanium oxide according to the present invention is characterized by having a very large specific surface area of 3 ~ 50 m ² / g, more specifically 10 ~ 20 m ² / g.

Conventional magellitic titanium oxide has an irregular shape and a smooth surface and has a very small specific surface area of 0.1 to 1.5 m ² / g, but the magellitic titanium oxide according to the present invention has an extremely large specific surface area, There is a characteristic to be pore.

In the present invention, the magnetic phase titanium oxide is a titanium sub oxide (titanium sub oxide), the magnetic phase titanium oxide includes TinO _2n-1 (a natural number of 4≤n≤10), Ti ₄ O ₇ Commercially available ebonex in which Ti ₅ O ₉ , Ti ₆ O ₁₁ , Ti ₇ O ₁₃ and Ti ₈ O ₁₅ coexist in the base.

Characteristically, the magellitic titanium oxide according to the present invention contains Ti ₄ O ₇ and Ti ₅ O ₉ , and more particularly, the titanium oxide contains 80 wt% or more of Ti ₄ O ₇ and Ti ₅ O ₉ . More specifically from 90 wt% to 98 wt% Ti ₄ O ₇ and Ti ₅ O ₉ .

Specifically, the magellitic titanium oxide according to the present invention contains 140 to 200 parts by weight of Ti ₅ O _{9 based} on 100 parts by weight of Ti ₄ O ₇ .

The magellitic titanium oxide may further contain at least one titanium oxide selected from Ti _m O _{2m −1} (natural water having 6 ≦ _m ≦ 10) and non-protonous titanium oxide, in addition to Ti ₄ O ₇ and Ti ₅ O ₉ . In addition, more specifically, Ti ₄ O ₇ And Ti ₅ O ₉ It is characterized by further containing the above non-protonous titanium oxide. In this case, the non-protonous titanium oxide includes Ti _k O _{2k− (1 + 2l)} (a natural number of 4 ≦ k ≦ 10 and a natural number of 1 ≦ _l ≦ (k-1)).

As described above, the magnetellitic titanium oxide according to the present invention is characterized by containing nanopores. Specifically, the magellitic titanium oxide according to the present invention is characterized by containing nanopores having an average diameter of 10 to 20 nm, the nanopores are characterized by having a uni-modal distribution.

As described above, while the conventional magneto-type titanium oxide has an irregular shape, the magneto-type titanium oxide according to the present invention is characterized by being a particle having a faceted projection shape. The angular projection shape includes a shape consisting of flat lines on at least one side of the shape, and includes a shape consisting of flat lines on at least two different sides of the projection shape, wherein the two sides of the flat line are curved or flat. The edges of the two sides of the line include a shape that is discontinuously bent. More particularly, the magellitic titanium oxide according to the present invention has a polygonal projection shape including a square or a hexagon.

Characteristically, the magnetic phase titanium oxide according to the present invention is characterized by having a structure in which a porous surface region surrounds a dense interior. More specifically, the titanium oxide according to the present invention is characterized by having a surface area in which the pores are distributed in a large number, and based on the radius R of the titanium oxide particles, the thickness of the surface area is 10 to 40%. have.

The magnesium phase titanium oxide according to the present invention has a metal loading of 35 wt% or more, and the metal includes a catalytic metal used in a fuel cell. Examples of the catalyst metal include noble metals including platinum (Pt), ruthenium (Ru), palladium (Pd), and iridium (Ir); And transition metals including cobalt (Co), molybdenum (Mo), iron (Fe), cesium (Ce), and lanthanum (La); or a single metal or two or more alloys thereof. In view of good catalytic activity, the catalytic metal preferably comprises platinum.

The present invention provides a catalyst for a fuel cell containing the above-mentioned magneto-type titanium oxide, and provides a fuel cell equipped with the catalyst for the fuel cell. In this case, the fuel cell includes a polymer electrolyte fuel cell.

The fuel cell catalyst according to the present invention has a metal loading amount of 35 wt.% As the support has magnetite-type titanium oxide having a very large specific surface area of 3 to 50 m ² / g, more specifically 10 to 20 m ² / g. It has a characteristic of more than%, has an electrical conductivity of 3 S / cm or more, substantially, has a very good electrical conductivity of 3 ~ 5 S / cm, very durable at high voltage, and has a feature of having a high corrosion resistance under oxygen conditions. In addition, 35 wt% or more of the metal may be uniformly dispersed and supported in the form of nanoparticles, and thus, a thin catalyst layer may be manufactured to prevent an increase in gas diffusion resistance.

The fuel cell equipped with a catalyst for a fuel cell according to the present invention may be provided with a thin catalyst layer as a support of the above-described magneto-type titanium oxide loaded with a large amount of metal, and may be provided with a thin catalyst layer, and the gas may be introduced by a thin catalyst layer. As the diffusion distance is shortened, it is possible to prevent a decrease in performance and durability due to an increase in gas diffusion resistance.

Hereinafter, it provides a preferred method for producing the magnetellitic titanium oxide according to the present invention described above.

The magnesium phase titanium oxide is a titanium oxide on anatase, titanium oxide on rutile or a mixture thereof as a precursor, and after mixing the precursor and the carbon powder, the precursor is phase-converted to the magnetic phase (phase Including the first heat treatment to transition and the second heat treatment to remove the carbon powder, characterized in that the magneto phase titanium oxide having a specific surface area of 3 ~ 50 m ² / g is produced.

Specifically, the magnetic phase titanium oxide is a) a first heat treatment step of heat-treating a mixture containing a precursor and carbon powder which is a titanium oxide in an inert or reducing atmosphere; And b) a second heat treatment step of heat treatment in an oxidizing atmosphere after the first heat treatment.

In this case, the precursor includes anatase titanium oxide, rutile titanium oxide or a mixture thereof, and the carbon powder includes carbon black, carbon nanotubes, carbon nanofibers, graphite powder or mixtures thereof.

As described above, the method for producing magellitic titanium oxide according to the present invention uses anatase titanium oxide, rutile titanium oxide, or a mixture thereof as a precursor of magellitic titanium oxide, and the precursor and carbon powder A raw material containing a mixture of is characterized in that the raw material is first subjected to phase transformation (primary heat treatment) of titanium oxide, and then heat-treated in an oxidizing atmosphere (secondary heat treatment) to remove carbon.

This gives a magnetellitic titanium oxide having a very large specific surface area of 3 to 50 m ² / g, more particularly 10 to 20 m ² / g.

Preferably, the raw material contains 100 to 300 parts by weight of carbon powder with respect to 100 parts by weight of the precursor of the magnetellitic titanium oxide, the average particle size of the precursor is 2 to 100 nm, the average particle size of the carbon powder Is preferably from 10 to 100 nm.

The first heat treatment is performed in an inert atmosphere or a reducing atmosphere, wherein the inert atmosphere includes nitrogen, argon, helium or an atmosphere in which these are mixed, and the reducing atmosphere includes hydrogen or a mixed gas atmosphere of hydrogen and an inert gas. When the first heat treatment is performed in a mixed gas atmosphere of hydrogen and an inert gas, the mixed gas preferably contains 5 to 95 vol% of hydrogen.

The first heat treatment for the phase transformation of the precursor is characterized in that it is carried out at 1050 ~ 1100 ℃ under inert atmosphere or reducing atmosphere described above, the first heat treatment is preferably performed for 3 to 24 hours.

The second heat treatment is performed in an oxidizing atmosphere, and the oxidizing atmosphere includes oxygen, air, or a mixed gas atmosphere of oxygen and an inert gas. The second heat treatment for removing the carbon powder is characterized in that it is carried out at 600 ~ 950 ℃ under the oxidizing atmosphere, the second heat treatment is preferably carried out for 1 to 6 hours.

1 is a mixture of 10 g of carbon black (Vulcan XC72) and 20 g of anatase titanium oxide (Aldrich), followed by heat treatment at 1050 ° C. for 15 hours in a reducing atmosphere mixed with 5 vol% hydrogen and 95 vol% nitrogen. And X-ray diffraction results of the magnetellitic titanium oxide obtained by heat treatment at 800 ° C. for 3 hours in an air atmosphere.

The X-ray diffraction is a diffraction result of the obtained powder phase, and the X-ray diffraction is a result obtained under the conditions of a sampling width of 0.002 ° and a scanning speed of 2 ° / min using Cu-Kα rays.

As can be seen in FIG. 1, the magellitic titanium oxide of the present invention, together with Ti ₄ O ₇ and Ti ₅ O ₉ , contains a non-protonous titanium oxide, Ti ₄ O ₅ , of 60.1 wt%. Ti ₅ O ₉ , 34.1 wt% Ti ₄ O ₇ , 5.8 wt% Ti ₄ O ₅ . As a comparative example of FIG. 1, shown with the X- ray diffraction results of the commercial magneto Marinelli the titanium oxide (Atraverda four, Ebonex ^ⓡ).

Figure 2 shows the adsorption volume (Fig. 2 (a)) and the pore distribution (Fig. 2 (b)) measured using the pressure measured by the nitrogen adsorption and desorption method, similar to Figure 1 commercial Magelli phase of titanium oxide (Atraverda four, Ebonex ^ⓡ) it is shown with a nitrogen adsorption-desorption and the resulting pore distribution.

As can be seen in Figure 2, the magnetic phase titanium oxide according to the present invention shows a very large nitrogen adsorption / desorption capacity compared to conventional commercial magnetic phase titanium oxide, there is a nano-pores having an average size of 13 nm Able to know.

As a result of measuring the specific surface area of the commercially available magenta-type titanium oxide and the magenta-titanium oxide according to the present invention, the commercially available magenta-titanium oxide has a specific surface area of 0.8 m ² / g. It can be seen that the oxide has a specific surface area of 15 m ² / g and has a specific surface area of 18 times or more that of commercially available magnesium phase titanium oxide.

3 to 4 are transmission electron micrographs of the magneto-type titanium oxide according to the present invention, FIG. 5 is a scanning electron micrograph of the magneto-type titanium oxide according to the present invention, and FIG. 6 is a commercial magneto-type titanium oxide. Scanning electron micrograph of.

As can be seen in Figures 3 to 4, it can be seen that the magnetellitic titanium oxide according to the present invention has a dense internal region and a porous surface region. That is, the magellitic titanium oxide according to the present invention can be seen that the inside has a high density, the outside has a structure of increasing porosity. As a result of analyzing a plurality of magellinium-titanium oxide particles by transmission electron microscope, it was confirmed that the outer porous portion of the prepared magellinium-titanium oxide powder was formed at about 10 nm level.

As can be seen in Figures 3 to 5, the magellitic titanium oxide according to the present invention can be seen that the two-dimensional projection shape of the square or hexagon angled particle shape, as observed in Figure 5, very rough It can be seen that it has a surface.

On the other hand, as can be seen in Figure 6, commercial magenta-type titanium oxide has an irregular (irregular) shape, it can be seen that it has an extremely smooth surface.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (11)

It has a specific surface area of 10 to 20 m ² / g, has a dense internal region and a porous surface region surrounding the inner region and the nano pores are distributed, the porous surface region is 10 to 10 based on the particle radius (R) Magellitic titanium oxide particles with a thickness of 40%. The method of claim 1,
The titanium oxide particles are magnesium phase titanium oxide particles, characterized in that containing Ti ₄ O ₇ and Ti ₅ O ₉ . 3. The method of claim 2,
The titanium oxide particles are magnesium phase titanium oxide particles, characterized in that containing at least 80 wt% Ti ₄ O ₇ and Ti ₅ O ₉ . 3. The method of claim 2,
The titanium oxide further comprises aprotic titanium oxide having Ti _k O _{2k-(1 + 2l)} (a natural number of 4≤k≤10, a natural number of 1≤l≤ (k-1)). Phase Titanium Oxide Particles. delete The method of claim 1,
Magellinium-titanium oxide particles, characterized in that the average diameter of the nano-pores is 10 to 20nm. delete delete The method of claim 1,
Magnetic phase titanium oxide particles, characterized in that the metal loading of the titanium oxide is 35wt% or more. A catalyst for a fuel cell containing the magnetellitic titanium oxide particles of any one of claims 1 to 4, 6 and 9. A fuel cell equipped with the catalyst of claim 10.

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