JP2013518710A - Catalyst production method and catalyst - Google Patents

Abstract

The present invention is a method for producing a catalyst, wherein the catalyst contains a catalytically active substance and a carbon-containing support, and the carbon-containing support is impregnated in the metal salt solution in the first step, and then the carbon-containing impregnated metal salt solution is impregnated. The present invention relates to a method for producing a catalyst in which a support is heated to a temperature of at least 1500 ° C. in an inert atmosphere to form a metal carbide layer, and finally a catalytically active material is applied to a carbon-containing support provided with the metal carbide layer.
Furthermore, the present invention is a catalyst produced by this method, comprising a carbon-containing support and a catalytically active material, the carbon-containing support including a metal carbide layer, and the catalytically active material comprising a metal carbide layer. A catalyst applied to a carbon-containing support is provided.
[Selection figure] None

Description

  The present invention relates to a method for producing a catalyst, the catalyst comprising a catalytically active substance and a modified carbon-containing support. The present invention further relates to a catalyst comprising a modified carbon-containing support and a catalytically active material.

  A catalyst containing a catalytically active substance and a carbon-containing support is used, for example, as a heterogeneous catalyst for an electrochemical reaction. As a catalytically active substance for an electrochemical reaction, a platinum group metal or a platinum group metal alloy is usually used. The alloying components used are usually transition metals such as nickel, cobalt, vanadium, iron, titanium, copper, ruthenium, palladium, in each case individually or with one or more additional metals It is a combination. Such catalysts are used in particular in fuel cells. The catalyst can be used on both the anode side and the cathode side. Particularly on the cathode side, it is necessary to use an active cathode catalyst that is also corrosion resistant. Alloy catalysts are commonly used as active cathode catalysts.

In order to obtain a high catalyst surface area, the catalyst is usually supported. For electrochemical applications, the carrier used must be made conductive. Carbon is generally used as a carrier, for example, in the form of conductive carbon black. The carbon support used usually has a high specific surface area that allows fine dispersion of the particles of catalytically active material normally present as nanoparticles. The BET surface area is generally greater than 100 m ² / g. However, these carbon supports such as Vulcan XC72 having a BET surface area of about 250 m ² / g or Ketjen Black EC-300J having a BET surface area of about 850 m ² / g have the disadvantage of rapidly corroding. The corrosion of the carbon-containing supports can be compared by subjecting them to a potential in excess of 1 V in the presence of water, such as a wet stream of nitrogen or an aqueous electrolyte solution, optionally at an elevated temperature. Here, the carbon is converted to carbon dioxide and the resulting carbon dioxide can be measured. The higher the temperature and the higher the potential, the more rapidly the carbon-containing support will corrode. Thus, for example, in the case of Vulcan XC72, at a potential of 1.1 V, after about 15 hours, about 60% of the carbon is eroded away by oxidation to carbon dioxide. In the case of carbon black having a smaller specific surface area, such as Denka Black, which has a BET specific surface area of about 60 m ² / g, the support has a higher corrosion resistance due to the higher proportion of graphite in the carbon black. After 15 hours at 1.1 V, the corrosion corresponds to a loss of only 8% carbon. Catalyst particles on a carbon support with a smaller surface area are usually somewhat larger and therefore closer to each other. However, this often results in a decrease in performance since only a fraction of the amount of catalytically active material applied to the support can be utilized catalytically.

  According to WO 2006/002228 it is also known to subject the carbon-containing support to a surface treatment apart from the use of a carbon support having a low BET surface area. As a result of the surface treatment, the carbon comprises a metal carbide layer. The metal used to produce the metal carbide layer is, for example, titanium, tungsten or molybdenum. The catalytically active material is subsequently deposited on the metal carbide layer.

  For the production of the metal carbide layer, a metal salt solution is first applied to the surface of the carbon-containing support and then this solution is reduced to a metal. Subsequently, the support is heated to convert the metal to metal carbide. The heating for forming the metal carbide layer is performed at a temperature in the range of 850 to 1100 ° C. However, it has been found that metal carbide layers produced as described in WO-A 2006/002228 are not stable enough to provide a satisfactory improvement in corrosion stability.

  Corrosion of the carbon-containing support results in desorption of particles of catalytically active material, and hence performance degradation. In addition, the catalyst particles may also sinter, reducing the catalytically active surface area.

WO2006 / 002228

  An object of the present invention is to provide a method for producing a catalyst in which a catalyst having corrosion stability is produced when used as a cathode catalyst for an electrochemical reaction. In particular, the catalyst in which the catalyst particles interact with the surface region should be produced in such a way that the particles hardly change on the support, i.e. hardly sinter and desorb from the support.

The object is a method for producing a catalyst comprising a catalytically active substance and a carbon-containing support, comprising the following steps:
(A) impregnating a metal salt solution with a carbon-containing support;
(B) heating the carbon-containing support impregnated with the metal salt solution to a temperature of at least 1200 ° C. to form a metal carbide layer;
(C) A method comprising a step of applying a catalytically active material to a carbon-containing support provided with a metal carbide layer.

FIG. 1 shows a catalyst according to Comparative Example 1 before exposure to an electrochemical process. FIG. 2 shows the catalyst according to Comparative Example 1 after exposure to an electrochemical process. FIG. 3 shows the catalyst according to Example 1 before exposure to an electrochemical process. FIG. 4 shows the catalyst according to Example 1 after exposure to an electrochemical process.

  As a result of heating the carbon-containing support impregnated in the metal salt solution to a temperature of at least 1200 ° C., a stable metal carbide layer is formed. Thanks to the metal carbide layer on the support, the carbon binds to its surface and no longer reacts with any oxygen surrounding the support. The corrosion of the carbon-containing support can be reduced in this way and even completely avoided. A further advantage is that the catalytically active surface of the catalyst is not significantly altered by the formation of the metal carbide layer, so that high catalytic activity and long-term stability are always achieved. In addition, the loss of catalytically active material can be prevented beforehand by the metal carbide layer so that the catalytic activity of the catalyst is not reduced by the loss of catalytically active material. The fact that the catalytically active material does not desorb from its support is associated with particles of catalytically active material that adhere well to the support as a result of the metal carbide layer. Due to the fact that the catalyst particles hardly sinter and do not desorb from the support, the catalyst surface area of the catalyst particles is stable over a long period of time and the performance of the electrode remains high. Furthermore, only the carbide phase, not the oxide phase, can be observed in the X-ray diffraction pattern.

  The improvement in the adhesion of the catalytically active substance can be examined using, for example, a transmission electron microscope. Therefore, according to Journal of Power Sources, 2008, 185, 734-739, generating an image of an electrocatalyst in the same place before and after electrochemical treatment and observing the catalyst change caused thereby. Can do. Thus, for example, in the case of a pure carbon supported catalyst, the sintering or desorption of particles of the catalytically active material can be seen. On the other hand, in the case of the catalyst according to the invention, almost no change occurs under the same conditions.

A suitable carbon-containing support for the catalyst of the present invention is preferably carbon black. Carbon black can be produced by any method known to those skilled in the art. Commonly used carbon blacks are, for example, furnace black, frame black, acetylene black or any other carbon black known to those skilled in the art. The use of graphitized carbon, especially carbon having a low surface area, is particularly preferred. For the purposes of the present invention, low surface area means a BET surface area of 250 m ² / g or less, more preferably 100 m ² / g or less. Suitable carbon can be used as a support has, for example, SKW carbon having a BET surface area of 72m ² / g, Denka Black having a BET surface area of 53m ² / g, or a BET surface area of about 30 m ² / g, Evonik XMB206 or AT325 from Degussa GmbH. According to the invention, a metal carbide layer is applied to a suitable carbon support.

  The catalyst used includes platinum group metals, transition metals, alloys of these metals, alloys containing at least one metal of the platinum group, and the like. The catalytically active material is preferably selected from platinum, palladium, alloys of these metals, and alloys containing at least one of these metals. The catalytically active material is very particularly preferably platinum or a platinum-containing alloy. Suitable alloying metals are nickel, cobalt, iron, vanadium, titanium, ruthenium, copper and the like, in particular nickel and cobalt. Suitable alloys containing at least one platinum group metal are selected from the group consisting of, for example, PtNi, PtFe, PtV, PtCr, PtTi, PtCu, PtPd, PtRu, PdNi, PdFe, PdCr, PdTi, PdCu and PdRu Is done. A platinum-nickel alloy or a platinum-cobalt alloy is particularly preferred. When the alloy is used as a catalytically active substance, the proportion of platinum group metal in the alloy is preferably in the range of 25-85 atomic%, more preferably in the range of 40-80 atomic%, even more preferably in the range of 50- It is in the range of 80 atomic%, especially in the range of 60-80 atomic%.

  Apart from the alloys mentioned above, it is also possible to use alloys containing two or more different metals, such as ternary alloy systems. It is also possible to include further components such as metal oxides, usually in a proportion of less than 1% by weight.

  In order to produce the catalyst of the present invention, the carbon-containing support is impregnated with a metal salt solution in the first step. In order to impregnate the carbon-containing support with the metal salt solution, for example, the carbon-containing support can be dispersed in the metal salt solution, and then the dispersion can be concentrated.

  As a result of the impregnation, the metal salt solution penetrates into the pores of the carbon-containing support. A layer of metal salt is also formed on the outer surface of the carbon-containing support.

  The complete conversion of carbon to metal carbide is such that the advantageous base structure of the carbon used, such as carbon black, is too greatly influenced by the performance of the catalyst produced therefrom or the processability of the catalyst The surface is preferably converted to metal carbide.

  A metal salt solution for impregnating the carbon-containing support is preferred in order to prevent all the carbon of the support from reacting to form metal carbide and forming a metal carbide layer only on the surface of the support. Added in stoichiometric amount. For the purposes of the present invention, stoichiometry means that less than 90% by weight of metal is used, based on the sum of metal and carbon. The ratio of the metal is usually 5 to 75% by mass, preferably 20 to 50% by mass in each case based on the sum of the metal and carbon.

In order to obtain a stable metal carbide layer on the carbon-containing support, the metal of the metal salt solution is tungsten, molybdenum, titanium, vanadium or zirconium, preferably tungsten or molybdenum. As a result of the use of the corresponding metal salt solution, the metal carbide layer formed on the carbon-containing support is a tungsten carbide layer or a molybdenum carbide layer. Further, the layer can also include a mixed carbide of two or more metals. It also allows the metal carbide layer to be doped with a second metal. The advantage of the metal carbide layer is that the advantageous structure, conductivity and surface properties of the carbon-containing support are substantially retained and the corrosion resistance is greatly improved. The retention of the properties of the carbon-containing support depends on the carbide content on the support surface.
As the metal salt solution impregnated with the carbon-containing support, a tungstate solution such as an ammonium tungstate solution can be used.

  In order to produce the metal carbide layer, in the second step, the carbon-containing support impregnated with the metal salt solution is heated to a temperature of at least 1200 ° C. in an inert atmosphere. An inert atmosphere means that the atmosphere does not contain any material that can react with the carbon or metal salt of the support. A suitable atmosphere is, for example, a rare gas atmosphere or a nitrogen atmosphere. The inert atmosphere is preferably a nitrogen atmosphere.

  The temperature at which the carbon-containing support impregnated with the metal salt solution is heated is at least 1200 ° C., preferably at least 1300 ° C., in particular at least 1500 ° C.

  In order to form a sufficiently stable metal carbide layer on the carbon-containing support, the carbon-containing support impregnated with the metal salt solution is impregnated with the metal salt solution for at least 30 minutes, preferably at least 1 hour, in particular at least 2 hours. The allowed carbon-containing support is maintained at a heated temperature. The heat treatment is particularly preferably carried out at a temperature of 1500 ° C. for 2 hours. This results in a metal carbide layer formed on the carbon-containing support surface that improves the corrosion stability of the carbon-containing support.

  After formation of the metal carbide layer, the carbon-containing support provided with the metal carbide layer is cooled and applied with a catalytically active material. Application of the catalytically active material can be carried out by any method known to those skilled in the art. Application of the catalytically active substance can be carried out, for example, by deposition in solution. For this purpose, for example, a metal compound containing a catalytically active substance can be dissolved in a solvent. The metal can be bound covalently, ionicly, or by complexation. Furthermore, metals can be reductively deposited as precursors or using alkali to deposit the corresponding hydroxide. Further possible methods of depositing platinum group metals are impregnation of metal-containing solutions (primary wetting), chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods, and also methods by which metals can be deposited. All the additional methods known to those skilled in the art used. First, it is preferable to deposit a platinum group metal salt. Precipitation follows after drying and heat treatment to produce the catalyst.

When the catalytically active material is applied by precipitation, for example, reduction precipitation such as platinum from platinum nitrate using NaBH ₄ can be carried out in ethanol. Alternatively, platinum acetylacetonate is mixed with the carbon-containing support with a metal carbide layer or the like, decomposition and reduction with H ₂ / N ₂ gas mixture are also possible. It is preferable to carry out reductive precipitation using ethanol.

  If an alloy containing palladium or a platinum group metal is used in place of platinum as the catalytically active material, the catalytically active material is similarly applied.

  The catalyst produced by the method of the present invention contains a carbon-containing support and a catalytically active material, the carbon-containing support has a metal carbide layer, and the catalytically active material is applied to the carbon-containing support provided with the metal carbide layer. Has been. As described above, the corrosion of the carbon support and, as a result, delamination and loss of the catalytically active material can be greatly reduced by the metal carbide layer.

Therefore, the specific surface area and also the BET surface area of a carbon-containing support with a metal carbide layer depends on the carbon-containing support originally used. A carbon-containing support having a BET surface area of 250 m ² / g or less is preferred. A carbon-containing support having a BET surface area of 100 m ² / g or less is particularly preferred.

  In order to use the catalyst of the present invention as, for example, a heterogeneous catalyst for an electrochemical reaction, the catalytically active substance is a platinum group metal or an alloy containing at least one platinum group metal. Those are preferred. Suitable metals for white metals are in particular platinum and palladium. It is also possible that platinum and palladium form a catalytically active material as a mixture.

  When the catalytically active material is an alloy containing at least one platinum group metal, this alloy is preferably PtNi, PtFe, PtV, PtCr, PtTi, PtCu, PtPd, PtRu, PdNi, PdFe, PdCr, PdTi, PdCu And PdRu.

  To achieve corrosion reduction, the metal of the metal carbide layer of the catalyst is preferably selected from the group consisting of tungsten, titanium, molybdenum, zirconium, niobium, vanadium and mixtures thereof. The metal of the metal carbide layer is particularly preferably tungsten.

  The catalyst of the present invention is particularly suitable for use as an electrode catalyst in a fuel cell. Here, the catalyst is particularly suitable as a cathode catalyst.

  In electrocatalytic corrosion, a distinction is generally made between two phases: first, sintering of a catalytically active material such as platinum, and second, corrosion of carbon. Sintering of the catalytically active material occurs at a relatively low potential, and carbon corrosion occurs at a higher potential, for example, greater than 1V. During fuel cell operation, carbon corrosion is significant because a large amount of carbon can corrode and separate even at very short potential peaks up to 1.5V. As a result of the corrosion of the carbon, there are firstly changes in the electrode structure that can lead to performance degradation, and secondly, the binding to the catalytically active material can be impaired. As a result, the corresponding catalytically active particles are no longer available for catalytic reaction and can be discharged from the system. Not only does this cause performance degradation, but it can also be a significant cost factor, especially when noble metals are used.

An accelerated aging test can be performed to preselect a corrosion stable carrier. Thus, it is possible to test the corrosion stability of the carrier in a fuel cell configuration where only the carrier is used on the cathode side instead of the catalyst, and a humidified nitrogen stream is introduced as the carrier gas instead of the air stream. . A voltage of at least 1 V, such as 1.1 V or 1.2 V, is applied, the CO ₂ produced by the oxidation of the carbon support and discharged into the gas stream is measured and converted into carbon loss of the support . The measurement is usually carried out at an elevated temperature such as 180 ° C. Because J. According to Power Sources, 2008, page 444, the corrosion rate is about 4 orders of magnitude faster than room temperature.

Example 1:
In order to modify the surface of DenkaBlack carbon black, 22 g of ammonium heptungstate was dissolved in 580 g of water, and 15 g of DenkaBlack carbon black was added thereto. The mixture was homogenized using an Ultra-Turrax at 8000 rpm for 30 minutes. The carbon black suspension was concentrated on a rotary evaporator and heated in a tube furnace under nitrogen at 1500 ° C. for 6 hours and 400 ° C. for 1 hour.

Tungsten loading was 47%. In X-ray diffraction, two tungsten carbide phases were observed: WC has a particle size of about 40 nm and W ₂ C has a particle size of about 23 nm. Hereinafter, the surface-modified carbon support produced by this method will be referred to as WC / Denka.

  In order to produce a platinum catalyst, 7.0 g of the support thus produced was dispersed in 500 ml of water and homogenized using an Ultra-Turrax for 15 minutes at 8000 rpm. 5.13 g of platinum nitric acid was dissolved in 100 ml of water and slowly added to the carrier dispersion. 200 ml of water and 800 ml of ethanol were subsequently added to the mixture and the mixture was refluxed for 6 hours. After cooling overnight, the suspension was filtered and the solid was washed with 2 liters of hot water to remove nitrates and dried under reduced pressure. The platinum loading was 29.8%, and the average crystallite size in XRD was 3.4 nm.

Example 2:
To modify the surface of carbon black C2 (AT325 from Evonik Degussa GmbH), 5.9 g ammonium heptungstate was dissolved in 580 g water and 16 g carbon black C2 was added thereto; the whole was 8000 rpm And homogenized with an Ultra-Turrax for 30 minutes. The carbon black suspension was concentrated on a rotary evaporator and heated in a tube furnace under nitrogen at 1500 ° C. for 6 hours and 400 ° C. for 1 hour.

  Tungsten loading was 16%. X-ray diffraction observed one tungsten carbide phase: WC had a crystallite size of about 65 nm.

  To produce a platinum catalyst, 10.5 g of the support thus produced was dispersed in 500 ml of water and homogenized using an Ultra-Turrax for 15 minutes at 8000 rpm. 7.77 g of platinum nitric acid was dissolved in 100 ml of water and slowly added to the carrier dispersion. 500 ml of water and 450 ml of ethanol were then added to the mixture and the mixture was refluxed for 6 hours. After cooling overnight, the suspension was filtered and the solid was washed with 2 liters of hot water to remove nitrates and dried under reduced pressure. Platinum loading was 28.4%, and the average crystallite size in XRD was 3.1 nm.

Comparative Example 1
7.0 g of carbon black C1 (XMB206 from Evonik Degussa GmbH) was dispersed in 500 ml of water and homogenized using an Ultra-Turrax for 15 minutes at 8000 rpm. 5.13 g of platinum nitric acid was dissolved in 100 ml of water and slowly added to the carbon black dispersion. 200 ml of water and 800 ml of ethanol were then added to the mixture and the mixture was refluxed for 6 hours. After cooling overnight, the suspension was filtered and the solid was washed with 2 liters of hot water to remove nitrates and dried under reduced pressure. The platinum loading was 27.1%, and the average crystallite size in XRD was 3.4 nm.

Comparative Example 2
The adjustment was performed in the same manner as described in Comparative Example 1 except for the carbon black support. Carbon black C2 was used instead of carbon black C1. The platinum loading was 27.4%, and the average crystallite size in XRD was 3.1 nm.

Comparative Example 3
Surface modification was carried out in a manner similar to that described in Example 2, except that the carbideization step (similar to WO 2006/002228) was an intermediate temperature step of 6 hours at a temperature of 850 ° C. and 1 hour at 400 ° C. It was carried out while pinching. Tungsten loading was 7%. The calculated value was 20%, that is, tungsten could not be deposited quantitatively. No tungsten carbide phase was observed in XRD, and only H ₂ WO ₄ * H ₂ O was observed.

  The platinum catalyst thus produced had a 28.9% platinum loading (similar to Example 2) and an average crystallite size of 3.4 nm.

Comparative Example 3 *
The preparation was carried out in a manner similar to that described in WO2006 / 002228. For this purpose, 8 g Vulcan XC72 was suspended in 1000 g water and homogenized using an Ultra-Turrax for 30 minutes at 8000 rpm. 3.2 g ammonium tungstate was dissolved in 200 ml water and slowly added to the suspension. An additional 750 ml of water was added to the mixture and the mixture was refluxed for 4 hours. Thereafter, 30.4 g of NaBH ₄ was dissolved in 100 ml of water and added dropwise over 1 hour with active release of gas and the mixture was refluxed for an additional 20 minutes. The reaction mixture was filtered and the solid was washed with 2 l of water. The still wet filter cake was heated in a tube furnace first at 100 ° C. for 1 hour and then at 900 ° C. for 1 hour.

  A platinum catalyst was produced on the support thus produced. The platinum loading was 28.2%, and the average crystallite size in XRD was 2.0 nm. A slight trace (0.05%) of tungsten could be detected.

Comparative Example 4
The adjustment was performed by a method similar to the method described in Comparative Example 1 except for the carbon black support. Carbon black XC72 was used instead of carbon black C1. The platinum loading was 27.7%, and the average crystallite size in XRD was 1.9 nm.

Comparative Example 5:
The adjustment was performed by a method similar to the method described in Comparative Example 1 except for the carbon black support. DenkaBlack carbon black was used instead of carbon black C1. The platinum loading was 27.7%, and the average crystallite size in XRD was 3.7 nm.

  The mass loss for four different carbon supports is shown in Table 1.

  Carbon Black C1 is XMB206 from Evonik Degussa GmbH, Carbon Black C2 is AT325 from Evonik Degussa GmbH, and WC / Denka is a surface modified carbon support prepared as described in Example 1.

  It can be seen that the corrosion rates of sample C1 and WC / Denka are not significantly different. Thus, the differences observed between the catalysts containing the respective supports only arise from the interaction between the catalyst particles and the supports.

  The degradation of the electrocatalyst performance can also be estimated by accelerated degradation tests. Thus, for example, the catalytic activity for oxygen reduction (cathode reaction) can be measured before and after the potential cycle. To measure the degradation in performance, a 150 potential cycle between 0.5 and 1.3 V was performed in an oxygen saturated electrolyte at a rate of 50 mV / s. The results are shown in Table 2. In Table 2, WC / Denka is tungsten carbide on DenkaBlack carbon black, WC / C1 is tungsten carbide on carbon black C1, and tungsten carbide on WC / C carbon black C2.

  Comparison of Example 1 and tests with no catalyst and tests with catalytically active materials, such as WC / Denka, show that the catalyst with each support shows a large difference despite the nearly equal large corrosion of the pure support. Is shown.

  In the case of a pure carbon support, i.e. in the case of a support that does not contain a tungsten carbide layer, the result of the corrosion of pure uncatalyzed carbon and the reduced performance of the applied catalyst can be assumed by the same decomposition mechanism. They are related to each other.

  It can be seen from Examples 1 and 2 that the application of the metal carbide layer also affects the performance degradation. The more metal carbide is applied to the support, the smaller the performance degradation. Furthermore, it has been found from WO-A 2006/002228 and the like that the known metal carbide production method is insufficient for improving the corrosion resistance of the carrier. This can be understood from Comparative Examples 2 and 3, or 3 *.

The figure shows transmission electron micrographs showing in each case the catalyst according to the prior art and the catalyst according to the invention before and after exposure to an electrochemical process.
FIG. 1 shows a catalyst according to Comparative Example 1 before exposure to an electrochemical process,
FIG. 2 shows the catalyst according to Comparative Example 1 after exposure to an electrochemical process,
FIG. 3 shows the catalyst according to Example 1 before exposure to an electrochemical process,
FIG. 4 shows the catalyst according to Example 1 after exposure to an electrochemical process.
In the figure, the uncoated carrier is indicated by reference numeral 1, the support coated with carbide is indicated by reference numeral 3, and the platinum particles are indicated by reference numeral 2.

  Transmission electron micrographs (TEMs) of the same catalyst area tested before and after exposure to the electrochemical process were taken with the catalyst of Example 1 and Comparative Example 1. Exposure to the electrochemical process was achieved using a 3600 potential cycle with an increase of 1 V / s between 0.4 and 1.4V.

  It can be seen from TEMs that the electrocatalysts differ greatly in spite of the same support stability. FIG. 1 before exposure to the electrochemical process and FIG. 2 after exposure to the electrochemical process on the pure carbon support according to Comparative Example 1 show that the platinum particles 2 are detached from the support 1 and therefore the catalytic reaction is lost. It shows that it was broken. In contrast, in the case of the support 3 having a carbide layer according to Example 1, it can be seen that the binding of the platinum particles 2 to the support is retained. This can be seen in FIG. 3 representing the catalyst of Example 1 before exposure to the electrochemical process and FIG. 4 representing the catalyst of Example 1 after the electrochemical process.

  As a result of the desorption of platinum from the carbon support, a significant reduction in the performance of the electrode catalyst is expected even on a highly corrosion resistant carbon support. In order to counter this, it is necessary to improve the adhesion of the platinum particles to the carrier. This is achieved by the modification according to the invention of the carbon surface with a carbide layer.

Claims (16)

A method for producing a catalyst comprising a catalytically active material and a carbon-containing support,
The following steps:
(A) impregnating a metal salt solution with a carbon-containing support;
(B) heating the carbon-containing support impregnated with the metal salt solution to a temperature of 1200 ° C. in an inert atmosphere to form a metal carbide layer;
(C) applying a catalytically active material to a carbon-containing support provided with a metal carbide layer.   The method of claim 1, wherein the metal salt solution impregnating the carbon-containing support is added in a stoichiometric amount.   The method according to claim 1 or 2, wherein the metal of the metal salt solution is tungsten, molybdenum, or a mixture or alloy containing at least one of these metals.   The method according to claim 1, wherein the metal salt solution is a tungstate solution.   The method according to any one of claims 1 to 4, wherein the heating in the step (b) is carried out in an inert atmosphere.   The method according to claim 1, wherein the catalytically active metal is a white metal or an alloy containing at least one metal of the white metal.   The alloy containing at least one platinum group metal is selected from the group consisting of PtNi, PtFe, PtV, PtCr, PtTi, PtCu, PtPd, PtRu, PdNi, PdFe, PdCr, PdTi, PdCu and PdRu. The method described in 1.   The method according to claim 6, wherein the platinum group metal is platinum or palladium. The method according to claim 1, wherein the catalytically active substance is applied to the carbon-containing support comprising the metal carbide layer by reduction deposition or by decomposition and reduction in a H ₂ / N ₂ gas mixture. The method according to claim 1, wherein the carbon-containing support has a BET surface area of 250 m ² / g or less. A catalyst produced by the method according to any one of claims 1 to 10,
Containing a carbon-containing support and a catalytically active substance,
The carbon-containing support has a metal carbide layer,
The catalyst, wherein the catalytically active substance is applied to a carbon-containing support having the metal carbide layer. The catalyst according to claim 11, wherein the carbon-containing support has a BET surface area of 250 m ² / g or less.   The catalyst according to claim 11 or 12, wherein the catalytically active substance is a metal of a white metal or an alloy containing at least one metal of a white metal.   The alloy comprising at least one platinum group metal is selected from the group consisting of PtNi, PtFe, PtV, PtCr, PtTi, PtCu, PtPd, PtRu, PdNi, PdFe, PdCr, PdTi, PdCu and PdRu. The catalyst according to 1.   The catalyst according to any one of claims 11 to 14, wherein the metal of the metal carbide layer contains tungsten and / or molybdenum.   A method of using the catalyst according to any one of claims 11 to 15 as an electrocatalyst for a fuel cell.

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