DE102012200606A1 - Electrically conductive material - Google Patents

Abstract

The present invention is an electrically conductive material comprising cores (1) of a metal mixture comprising a base metal and at least one metal additive, wherein the base metal and the at least one metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, Silver, copper, iridium, ruthenium, osmium, rhenium, wherein the parent metal is present in a concentration greater than or equal to 90 atomic percent, and wherein the at least one metal additive is present at a concentration of less than or equal to 10 atomic percent, the concentrations of the parent metal and the add at least one metal additive to 100 atomic percent. In such a material segregation of the metal mixture can be effectively prevented.

Description

The present invention relates to an electrically conductive material, in particular an electrode material, and a method for producing such.

State of the art

In technical applications, thermally and corrosively highly stable electrode materials are required which are predominantly metallic and electrically conductive and have a nanoscale and regularly defined structure.

The publication US 2007/0251822 A1 describes chemochromic nanoparticles that can be used as pigments, paints, coatings and inks.

Disclosure of the invention

The present invention is an electrically conductive material comprising cores of a metal mixture comprising a base metal and at least one metal additive, wherein the base metal and the at least one metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, silver, copper , Iridium, ruthenium, osmium, rhenium, wherein the parent metal is present in a concentration greater than or equal to 90 atomic percent, and wherein the at least one metal additive is present at a concentration of less than or equal to 10 atomic percent, wherein the concentrations of the parent metal and the at least one metal additive add to 100 atomic percent.

In the context of the present invention, an "electrically conductive material" can be understood in particular to mean a material which has a specific conductivity of at least 10 ^-1 Sm.

Such an electrically conductive material may comprise cores of at least two metals, one of which represents the metal and the metal forms at least one further metal or a plurality of further metals.

Characterized in that the base metal and the metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium, wherein the parent metal is present in a concentration of greater than or equal to 90 atomic percent, and wherein the metal additive is present in a concentration of less than or equal to 10 atomic percent, the metals mix homogeneously in the solid phase or alloy together at high temperatures, such as about 550 ° C or above. In this case, this metal or shows this metal mixture, even at high temperatures, a good oxidation resistance or corrosion resistance, so that, for example, an oxidation in an oxygen-containing atmosphere is not or very slowly or only at the outermost layer.

Furthermore, it is prevented in particular by the above-mentioned proportion of the base metal or of the metal additive that, for example, even at a possible use temperature of 500 ° C or about even there is no segregation of at least two metals of the core. Rather, a homogeneous metal mixture remains even under such conditions.

As a result, components configured from the material according to the invention are particularly long-term stable, essentially independent of the operating temperature, and do not change their properties or not significantly.

The electrically conductive material can be produced in particular by a method explained later.

The material may furthermore have a conductivity of greater than or equal to 10 ³ Sm ^-1 , in particular greater than or equal to 10 ⁶ Sm ^-1 . In addition, the material may have a BET surface area of greater than or equal to 5 m ² / g.

For example, the group A metal mixture may be a metal mixture, in particular a metal alloy comprising two metals. Optionally, the metal mixture may further comprise at least one other metal selected from platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium. However, the group A may consist of only two metals including platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium and mixtures thereof.

The material according to the invention can be used, for example, as a material or additional material in sensors, catalysts and fuel cells, for example as electrode material. In particular, the material according to the invention can be used in, for example, ceramic exhaust gas sensors, for example lambda probes, in chemosensors, in particular field effect chemosensors, and in field effect transistors, in particular as a gate electrode material.

In one embodiment, the cores of at least one oxide of a metal or metal mixture selected from the group B consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron , Cobalt, nickel, iridium, palladium and zinc and mixtures thereof, at least partially.

For the purposes of the present invention, the term "lanthanides" is understood to mean, in particular, the elements: cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

In the context of the present invention, the semimetals (boron, silicon, germanium) are counted among the metals.

• – dass das Oxid beziehungsweise die Oxide Poren, die zumindest gasdurchlässige sind, beispielsweise eine durchschnittliche Porengröße von größer oder gleich 0,3 nm bis kleiner oder gleich 50 nm, aufweisen, und/oder
• – dass zwei oder mehr Kerne, die einander kontaktieren, und/oder
• – dass ein Kern oder mehrere Kerne, die eine Substratoberfläche kontaktieren,
• umfasst sind.

In particular, the cores of oxides of a metal or metal mixture, group B, may be substantially completely surrounded. In particular, "substantially completely surrounded" means that deviations based thereon:

• - That the oxide or oxides pores, which are at least gas-permeable, for example, have an average pore size of greater than or equal to 0.3 nm to less than or equal to 50 nm, and / or
• That two or more cores contacting each other and / or
• That one or more cores contacting a substrate surface
• are included.

The oxide surrounding the cores at least partially may be both an oxide of a metal and a mixture of oxides of two or more metals or a mixed oxide. For example, the oxide may be a mixture of an oxide of a first metal of group B, for example selected from the group consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, Titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, iridium, palladium and zinc and mixtures thereof, and an oxide of a second, different group B metal, for example selected from the group consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, hafnium, niobium, tantalum, chromium, molybdenum, tungsten, manganese , Iron, cobalt, nickel, iridium, palladium and zinc and mixtures thereof. For example, the metal oxide may include or be zirconia.

In this embodiment, the oxide or oxides may, for example, be present associated with the metal mixture of the cores and also form a shell of corrosion-resistant and sinter-resistant material. As a result, the underlying cores can be protected particularly well against further structural changes and possible chemical attacks. The stability of the material can be further improved.

In particular, due to the oxidic environment, the electrically conductive material may advantageously be corrosion-resistant and / or temperature-stable. In this case, "corrosion-resistant" is understood to mean that the material after 10 hours at 400 ° C in a gas mixture of 10.00000 volume percent oxygen, 10.00000 volume percent water vapor, 0.00100 volume percent nitrogen monoxide, 0.00005 volume percent sulfur dioxide and 79 , 99895 volume percent nitrogen, undetectable by scanning electron microscopy. In particular, "temperature-stable" is understood to mean that the material does not detectably change after 10 hours at 400 ° C. in air by means of scanning electron microscopy. Furthermore, the material may be porous. Moreover, the cores and oxides in the material may be substantially homogeneously distributed. Furthermore, the electrically conductive material may have a regularly defined structure in the nanometer range. Furthermore, even in the single-digit nanometer range, determined by transmission electron microscopy (TEM), the chemical composition can remain unchanged, or undergo changes only in the context of impurities.

Preferably, the material also changes after 10 hours at 500 ° C, especially after 100 hours at 500 ° C, in a gas mixture of 10.00000 volume percent oxygen, 10.00000 volume percent water vapor, 0.00100 volume percent nitric oxide, 0.00005 volume percent sulfur dioxide and 79.99895 volume percent nitrogen, undetectable by scanning electron microscopy. Preferably, the electrical conductivity of the material when treated in the gas mixture, from 10.00000 volume percent oxygen, 10.00000 volume percent water vapor, 0.00100 volume percent nitric oxide, 0.00005 volume percent sulfur dioxide and 79.99895 volume percent nitrogen, does not decrease more than two orders of magnitude or in air by not more than two orders of magnitude, preferably by not more than one order of magnitude, in particular by not more than 50%.

In the context of a further embodiment, the material can be constructed of interconnected particles with pores in between in which the particles each have a core of a metal or metal mixture of group A, which is at least partially, in particular substantially completely, surrounded by an oxide layer of a metal or metal mixture of group B. This has the significant advantage that the cores are stabilized by the oxide layer. In particular, the cores are protected thereby substantially against thermally induced coarsening and sintering. Furthermore, the cores can be protected from environmental influences, in particular corrosive agents. Despite this protection, the material may be catalytically active due to the porosity, which may be advantageous for some sensor applications, for example. In the context of this embodiment, the material can, on the one hand, comprise pores lying between the particles and, on the other hand, pores in the oxide layer which are at least gas-permeable, for example an average pore size of greater than or equal to 0.3 nm to less than or equal to 50 nm, measured by scanning electron microscopy.

Within the scope of a further embodiment, the cores can at least partially have a diameter in a range from greater than or equal to 0.4 nm to less than or equal to 100 nm, for example greater than or equal to 5 nm to less than or equal to 50 nm, in particular greater than or equal to 10 nm to less than or equal to 25 nm as measured by Scanning Electron Microscopy or Transmission Electron Microscopy (TEM). Consequently, the cores in this embodiment can be formed in particular by nanoparticles. Particularly with nanoparticles, the above-described effect of preventing separation of the metals in the cores is advantageous, since, in particular with nanoparticles, even at, for example, low temperatures of, for example, 350 ° C. or below, the kinetic inhibition of segregation may not be sufficient. This may be particularly important if the materials have to meet a long service life such as 6000 hours in a critical temperature range. Because in this case there is always the risk of segregation if the mischmetal nanoparticles are not in thermodynamic equilibrium from a temperature sufficient for the kinetics of the mixture. This danger can be prevented according to the invention. For example, at least 75% of the cores or of the particles may have a diameter in a range from greater than or equal to 0.4 nm to less than or equal to 100 nm, for example greater than or equal to 5 nm to less than or equal to 50 nm, in particular greater than or equal to 10 nm to less than or equal to 25 nm as measured by scanning electron microscopy.

In a further embodiment, the base metal can be platinum and the metal additive can be rhodium. In this embodiment, the cores can thus consist of platinum and rhodium. Particularly in this composition, particularly advantageous effects of segregation prevention can be realized even at low temperatures. In particular, platinum is a particularly oxidation-resistant metal, in particular rhodium can improve the sintering stability. Even in the case that rhodium should form oxides, they are extremely stable.

• – größer oder gleich 60 Atomprozent bis kleiner oder gleich 99,5 Atomprozent an Metallen der Gruppe A, und
• – größer oder gleich 0,5 Atomprozent bis kleiner oder gleich 40 Atomprozent an Metallen der Gruppe B

umfassen, wobei die Summe der Metallatome der Gruppen A und B zusammen 100 Atomprozent ergibt. Bevorzugte Messmethoden umfassen diesbezüglich beispielsweise Energiedispersive Röntgenspektroskopie (EDX), Röntgenphotoelektronenspektroskopie (XPS), oder Sekundärionen-Massenspektrometrie (SIMS).In a further embodiment, the material, based on the total number of metal atoms in the material:

• Greater than or equal to 60 atomic percent to less than or equal to 99.5 atomic percent of Group A metals, and
• Greater than or equal to 0.5 atomic percent to less than or equal to 40 atomic percent of Group B metals

include, wherein the sum of the metal atoms of groups A and B together gives 100 atomic percent. Preferred measurement methods include, for example, energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), or secondary ion mass spectrometry (SIMS).

Because of the small amount in atomic percent of Group B oxide-forming metals, the Group A metal and Group B metal oxide metal advantageously is particularly well and stably electrically conductive. The proportion of metal oxide, which can essentially correspond to the fraction of metals according to the invention of group B, allows the stability of the material to be further improved.

• a1) Bereitstellen von Kernen eines Metallgemisches, umfassend ein Grundmetall und einen Metallzusatz, wobei das Grundmetall und der Metallzusatz ausgewählt sind aus der Gruppe A bestehend aus Platin, Rhodium, Gold, Palladium, Silber, Kupfer, Iridium, Ruthenium, Osmium, Rhenium, wobei das Grundmetall in einer Konzentration von größer oder gleich 90 Atomprozent vorliegt und wobei der wenigstens eine Metallzusatz in einer Konzentration von kleiner oder gleich 10 Atomprozent vorliegt, wobei sich die Konzentrationen des Grundmetalls und des wenigstens einen Metallzusatzes zu 100 Atomprozent addieren, und
• a1a) Behandeln des Materials aus Verfahrensschritt a1) bei mindestens 200 °C für 10 Minuten, beispielsweise bei mindestens 500°C für mindestens eine Stunde, zum Beispiel bei mindestens 600 °C für mindestens 2 Stunden, mit einem oxidierenden Gas oder Gasgemisch.

The invention further provides a process for producing an electrically conductive material, in particular an electrically conductive material according to the invention, for example an electrode material, comprising the process steps:

• a1) providing cores of a metal mixture comprising a parent metal and a metal additive, wherein the base metal and the metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium, wherein the base metal is present in a concentration greater than or equal to 90 atomic percent and wherein the at least one metal additive is present at a concentration of less than or equal to 10 atomic percent, the concentrations of the parent metal and the at least one metal additive adding up to 100 atomic percent, and
• a1a) treating the material from process step a1) at at least 200 ° C. for 10 minutes, for example at least 500 ° C for at least one hour, for example at least 600 ° C for at least 2 hours, with an oxidizing gas or gas mixture.

In method step a1), in particular nanoparticles or nanoparticles are used which comprise at least two metals and thus a metal mixture of group A. The nanoparticles can also be used in the form of a suspension of nanoparticles in a solvent. The metal mixture of group A can form a metal mixture, in particular a metal alloy, in process step a1).

In the process step a1a), annealing for producing the material takes place following.

The method according to the invention, for example for the production or conditioning of electrodes, can take place at elevated temperatures, such as greater than or equal to 500 ° C., preferably greater than or equal to 600 ° C., in particular in specific gas atmospheres. As a result, no changes in the finished electrode occur at a later use of the material as electrode material, for example, less than or equal to 500 ° C.

• a2) Bereitstellen eines Metalls oder Metallgemisches, beispielsweise einer Metalllegierung, ausgewählt aus der Gruppe B bestehend aus Silizium, Germanium, Zinn, Bor, Aluminium, Gallium, Indium, Beryllium, Magnesium, Scandium, Yttrium, Lanthan, den Lanthaniden, Titan, Zirkonium, Hafnium, Niob, Tantal, Chrom, Molybdän, Wolfram, Mangan, Eisen, Cobalt, Nickel, Zink und Mischungen davon auf zumindest einem Teil der Oberfläche der Kerne, und/oder Bereitstellen mindestens einer Verbindung eines Metalls oder Metallgemischs, ausgewählt aus der Gruppe B bestehend aus Silizium, Germanium, Zinn, Bor, Aluminium, Gallium, Indium, Beryllium, Magnesium, Scandium, Yttrium, Lanthan, den Lanthaniden, Titan, Zirkonium, Hafnium, Niob, Tantal, Chrom, Molybdän, Wolfram, Mangan, Eisen, Cobalt, Nickel, Zink und Mischungen davon auf zumindest einem Teil der Oberfläche der Kerne, und
• a3) Behandeln des Materials aus Verfahrensschritt a2) bei mindestens 200 °C für 10 Minuten, beispielsweise bei mindestens 500°C für mindestens eine Stunde, zum Beispiel bei mindestens 600 °C für mindestens 2 Stunden, mit einem oxidierenden Gas oder Gasgemisch.

Within the scope of an embodiment, the method may comprise the further steps:

• a2) providing a metal or metal mixture, for example a metal alloy, selected from the group B consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, Hafnium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, zinc and mixtures thereof on at least part of the surface of the cores, and / or providing at least one compound of a metal or metal mixture selected from group B. consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, hafnium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt , Nickel, zinc and mixtures thereof on at least part of the surface of the cores, and
• a3) treating the material from process step a2) at least 200 ° C for 10 minutes, for example at least 500 ° C for at least one hour, for example at least 600 ° C for at least 2 hours, with an oxidizing gas or gas mixture.

An "oxidizing gas or gas mixture" can be understood to mean a gas or gas mixture in which, at temperatures of 200 ° C. or more, the group B metal or metal mixture or the compound of the metal or metal mixture of group B are oxidized. In particular, an "oxidizing gas or gas mixture" can be understood as meaning a gas or gas mixture in which at temperatures of 500 ° C. or more, in particular of 600 ° C. or more, the metal or metal mixture of group B or the compound of the metal or metal mixture the group B oxidized. In particular, the Group B metal or metal mixture or the Group B metal or metal compound compound can be completely oxidized. The oxidizing gas or gas mixture may be, for example, a gas mixture of 10 volume percent oxygen and 90 volume percent nitrogen.

The metal or metal mixture of group B can be used in process step a2) in the form of particles, in particular nanoparticles, or in the form of a suspension of particles, in particular nanoparticles, in a solvent. The compound of the metal or metal mixture of group B can be used in process step a2) in the form of particles, in particular nanoparticles, or in the form of a suspension of particles, in particular nanoparticles, dissolved in a solvent or in a solvent. Further, the Group B metal or metal mixture and / or the Group B metal or metal compound compound associated with the Group A metal or metal mixture may be introduced.

By method step a3), it is advantageously possible to form an envelope of corrosion-resistant and sinter-stable metal oxides of group B around metals of group A. In particular, a material may be made which comprises a metallic framework of Group A metals surrounded by Group B metal oxides. In this way, the group A metal or metal mixture can advantageously be protected from possible structural changes and chemical attack.

By such a method, advantageously, the above-described electrically conductive material, in particular electrode material, having the properties described above can be produced. This can, as already explained, be not only electrically conductive, but also predominantly metallic and / or corrosion-resistant and / or temperature-stable and / or porous. In this case, a porous material can be produced, for example, using nanoparticles of the metal A, whereas closed structures can also be possible by sputtering methods. In addition, an electrically conductive material produced by such a method, In particular electrode material having a regularly defined structure in the nanometer range.

The treatment with the oxidizing gas or gas mixture may in particular at a temperature of greater than or equal to 500 ° C to less than or equal to 1500 ° C, for example from greater than or equal to 550 ° C to less than or equal to 1000 ° C, and / or during a treatment time of more than one hour, for example more than 2 hours.

The oxidizing gas or gas mixture can be, for example, greater than or equal to 1 volume percent to less than or equal to 100 volume percent, for example, greater than or equal to 1 volume percent to less than or equal to 20 volume percent, more preferably greater than or equal to 1 volume percent to less than or equal to 15 volume percent oxygen and from greater than or equal to 0% by volume to less than or equal to 99% by volume, for example greater than or equal to 80% by volume to less than or equal to 99% by volume, in particular greater than or equal to 85% by volume to less than or equal to 99% by volume of nitrogen or one or more noble gases, In particular, argon, or a mixture of nitrogen and one or more noble gases, in particular argon, comprise, wherein the sum of the volume percent of oxygen, nitrogen and the noble gases together gives 100 volume percent.

In one embodiment of the process, in step a2), the compound of the metal or metal mixture of group B is dissolved in a solvent (as a solution). In this way it can be achieved that the group A nanoparticles are substantially completely surrounded by an oxide layer.

In process step a2), however, the compound of the metal or metal mixture of group B can also be provided in the form of nanoparticles. The metal or metal mixture of group B can also be provided in method step a2) in the form of nanoparticles. For example, the nanoparticles may be provided as a bed.

In a further embodiment of the process, in step a2) the metal or metal mixture of group B in the form of a suspension of nanoparticles in a solvent and / or in process step a2) the compound of the metal or metal mixture of group B in the form of a suspension of nanoparticles provided in a solvent. In this way, a high homogeneity of the electrically conductive material can be achieved.

Preference is given to using polar protic solvents, such as dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, or protic solvents, such as ethanol, ethylene glycol, hexanoic acid or tripropylamine, as solvent.

After the process steps a1) or a2), the process may comprise the process step b01): applying the material from process step a1) and / or a2) to the surface of a carrier element, for example a zirconium oxide carrier element or a silicon wafer. In particular, the material from process step a1) and / or a2) in process step b01) can first be applied to the surface in a solvent. The solvent can then be removed / dried in a process step b02) following the process step b01).

Within the scope of a further embodiment of the process, the process according to process steps a1) / a2), b01) and / or b02) comprises process step b03): treating the material at at least 350 ° C. for at least 20 minutes, in particular at at least 500 ° C. for at least 1 hour, for example at least 550 ° C for at least 1.5 hours, for example at least 600 ° C for at least 2 hours, with a non-oxidizing, especially reducing, gas or gas mixture. In this way, inter alia, an alloy formation between metals of groups A and B can be promoted. The treatment with the non-oxidizing, in particular reducing, gas or gas mixture may, for example, at a temperature of greater than or equal to 500 ° C to less than or equal to 1500 ° C, for example from greater than or equal to 550 ° C to less than or equal to 1000 ° C, and / or during a treatment time of more than one hour, for example more than 2 hours.

A "non-oxidizing gas or gas mixture" may be understood to mean a gas mixture in which, at temperatures of 350 ° C. or more, the metal or metal mixture of group A and the metal or metal mixture of group B and the compound of the metal or metal mixture of the group B are not oxidized. In particular, a "non-oxidizing gas or gas mixture" can be understood as meaning a gas mixture in which at temperatures of 500 ° C. or more, for example of 550 ° C. or more, for example of 600 ° C. or more, the metal or metal mixture of group A. and the Group B metal or metal mixture and the Group B metal or metal compound compound are not oxidized. For example, as a "non-oxidizing gas or gas mixture" a gas mixture of 5 percent by volume of hydrogen and 95 percent by volume of nitrogen are understood.

A "reducing gas or gas mixture" may be understood to mean a gas mixture in which, at temperatures of 350 ° C. or more, compounds, for example oxides, of the metal or metal mixture of group B having an oxidation number greater than zero are at least partially reduced. In particular, a "reducing gas or gas mixture" can be understood as meaning a gas mixture in which at temperatures of 500 ° C. or more, for example of 550 ° C. or more, for example of 600 ° C. or more, compounds, for example oxides, of the metal or metal compound of group B having an oxidation number of greater than zero are at least partially reduced. Optionally, the reducing gas or gas mixture may also partially or completely reduce compounds, the metal or metal mixture of group A having an oxidation number greater than zero, which may optionally occur as impurities in the nanoparticles.

The non-oxidizing, in particular reducing, gas or gas mixture may, for example, be greater than or equal to 0.001% by volume to less than or equal to 100% by volume, for example greater than or equal to 0.01% by volume to less than or equal to 20% by volume, in particular greater than or equal to 0.1% by volume less than or equal to 10% by volume, for example, greater than or equal to 1% by volume to less than or equal to 5% by volume of hydrogen or carbon monoxide or a mixture of hydrogen and carbon monoxide and greater than or equal to 0% by volume to less than or equal to 99.999% by volume, for example greater than or equal to From 80% by volume to less than or equal to 99.99% by volume, in particular from greater than or equal to 90% by volume to less than or equal to 99.9% by volume, for example greater than or equal to 95% by volume to less than or equal to 99% by volume of nitrogen or one or more Noble gases, in particular argon, or a mixture of nitrogen and one or more noble gases, in particular argon, comprise, wherein the sum of the volume percent of hydrogen, carbon monoxide, nitrogen and the noble gases together gives 100 volume percent.

The compound of a metal or metal compound of group B may be, for example, an inorganic or organic salt and / or an inorganic or organic complex of a metal or metal mixture (that is, two or more metals) of group B.

In a further embodiment of the process, the compound of a metal or metal compound of group B is an oxide, nitrate and / or halide of a metal or metal mixture of group B.

In a further embodiment of the process, the compound of a metal or metal mixture of group B is an alcoholate, for example a methoxylate, ethoxylate, n-propoxylate, isopropoxylate, an n-butoxylate or an isobutoxylate, in particular an ethoxylate, isopropoxylate or isobutylate, of a metal For example, a compound of a Group B metal or metal compound may be tantalum pentaethoxide, zirconium tetraisopropoxide, titanium tetraisobutoxylate, cerium acetate, or yttrium acetate. For example, a Group B metal or metal compound may be a Group B metal mixture or an organic acid salt, for example an Actetate. The organic acid may also be, for example, a beta-dicarbonyl compound, such as acetylacetone.

In a further embodiment of the method, the group A consists of platinum and rhodium, wherein in particular platinum can form the base metal and rhodium can form the metal additive. In this case, platinum can be present in a concentration of greater than or equal to 90 atomic percent and rhodium in a concentration of less than or equal to 10 atomic percent, wherein the proportions of platinum and rhodium can add up to 100 atomic percent. For example, platinum may be present in a concentration of greater than or equal to 95 atomic percent, and rhodium may be present in a concentration of less than or equal to 5 atomic percent. Furthermore, platinum can be present in a concentration of greater than or equal to 97 atomic percent and rhodium can be present in a concentration of less than or equal to 3 atomic percent.

Preferably, the Group A metal or metal mixture, based on the total number of Group A metal atoms, is greater than or equal to 60 atomic percent to less than or equal to 99.5 atomic percent, for example, greater than or equal to 70 atomic percent to less than or equal to 98 atomic percent, especially from greater than or equal to 80 atomic percent to less than or equal to 95 atomic percent of a metal selected from Group A consisting of platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium, and mixtures thereof of greater From 0.5 atomic percent to less than 40 atomic percent, for example from greater than or equal to 2 atomic percent to less than or equal to 30 atomic percent, in particular greater than or equal to 5 atomic percent to less than or equal to 20 atomic percent of a metal selected from group B consisting of silicon, germanium, Tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, Ti tan, zirconium, hafnium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, iridium, palladium and zinc, and mixtures thereof, wherein the sum of the atoms of metals A and B together is 100 atomic percent.

Optionally, the Group B metal compound can be one oxide or more oxides of boron.

Preferably, the group B consists of aluminum, gallium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, hafnium, niobium, tantalum, chromium, tungsten, manganese, iron or a mixture thereof.

In a further embodiment of the method, the group B consists of aluminum, cerium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium or a mixture thereof, in particular of yttrium, cerium, titanium, zirconium, tantalum or a mixture thereof.

For example, the Group B metal or metal mixture and / or the Group B metal or metal compound compound, based on the total number of Group A metal atoms, may be greater than or equal to 70 atomic percent to less than or equal to 100 atomic percent aluminum, cerium, titanium, Zirconium, hafnium, niobium, tantalum, chromium or a mixture thereof, and greater than or equal to 0 atomic percent to less than or equal to 30 atomic percent of silicon, germanium, tin, boron, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, Praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, molybdenum, tungsten, manganese, iron, cobalt, nickel, zinc or a mixture thereof, wherein the sum of the atoms of aluminum, cerium, titanium, zirconium, hafnium, niobium, tantalum, chromium, silicon, germanium, tin, boron, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, praseodymium, neodymium, promethium, samariu m, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, molybdenum, tungsten, manganese, iron, cobalt, nickel and zinc together gives 100 atomic percent.

In process step a2), two or more compounds of a metal or metal mixture can also be provided. In this case, the compounds may differ both in the type of metal and / or in the nature of the binding particle, in particular the salt former or complexing agent. For example, in process step a2) a first compound, for example an ethoxylate, isopropoxylate or isobutylate, of a first metal of group B, for example selected from the group consisting of yttrium, cerium, titanium, zirconium and tantalum, and a second, of the first same or a different compound, for example an ethoxylate, isopropoxylate or isobutylate, a second, of the first identical or different, in particular different, metal of group B, for example selected from the group consisting of yttrium, cerium, titanium, zirconium and tantalum.

Based on the total number of Group A metal atoms of the first and second compounds, from greater than or equal to 1 atomic percent to less than or equal to 99 atomic percent, for example greater than or equal to 45 atomic percent to less than or equal to 55 atomic percent of the first compound, for example zirconium tetraisopropoxide or Tantalum pentaethoxide, and from greater than or equal to 1 atomic percent to less than or equal to 99 atomic percent, for example, greater than or equal to 45 atomic percent to less than or equal to 55 atomic percent, second compound, for example, cerium acetate or yttrium acetate, wherein the sum of the metal atoms of the first and second compound together gives 100 atomic percent.

The present invention furthermore relates to an electrode comprising an electrically conductive material according to the invention.

Drawings and examples

Further advantages and advantageous embodiments of the subject invention are illustrated by the drawings and explained in the following description. It should be noted that the drawings have only descriptive character and are not intended to limit the invention in any way. It shows

1 a highly schematic cross section through a first embodiment of an electrically conductive material according to the invention;

2 a highly schematic cross section through a further embodiment of an electrically conductive material according to the invention;

3 a highly schematic cross section through a further embodiment of an electrically conductive material according to the invention;

4a a highly schematic cross section through a further embodiment of an electrically conductive material according to the invention;

4b a highly schematic cross section through a further embodiment of an electrically conductive material according to the invention;

5 a highly schematic cross section through a further embodiment of an electrically conductive material according to the invention;

6 an SEM image showing an embodiment of an electrically conductive material; and

7 a SEM image showing another embodiment of an electrically conductive material.

1 shows that the electrically conductive material in one embodiment is cores 1 comprising a group A metal mixture. In particular, the electrically conductive material in this embodiment consists of cores 1 from a metal mixture of group A. In this case, the material or have the cores 1 a base metal and at least one metal additive, wherein the base metal and the at least one metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium, wherein the base metal in a concentration is greater than or equal to 90 atomic percent, and wherein the at least one metal additive is present at a concentration of less than or equal to 10 atomic percent, with the concentrations of the parent metal and the at least one metal additive adding up to 100 atomic percent.

2 shows a further embodiment, wherein the cores 1 of at least one oxide 2a a metal or metal mixture of group B are at least partially surrounded. Such a material can be produced, for example, in accordance with process step a2) by using nanoparticles of groups A and B of equal size.

3 shows that the electrically conductive material according to 2 characterized by the electrically conductive material according to 1 differentiates that were used in step a2) for the group B nanoparticles, which are significantly smaller than the nanoparticles of group A.

4a illustrates a particle 3 which - according to process step a2) or a3) - results from the oxidation of nanoparticles which both metals of group A and metals of group B results. 4a shows that the particle produced in this way 3 a core 1 of a metal or metal mixture of group A, which completely with an oxide layer 2 B surrounded by a group B metal or metal mixture. 4a further shows that the transition from core 1 to oxide layer 2 B is fluent.

4b illustrates a particle 3 which - according to process step a2) or a3) - results from the reaction of group A nanoparticles with a solution of a compound of a metal of group B and subsequent oxidation. 4b shows that the particle produced in this way 3 a core 1 of a metal or metal mixture of group A, which completely with an oxide layer 2c surrounded by a group B metal or metal mixture.

5 illustrates that the electrically conductive material of another embodiment of interconnected particles 3 with pores in between 4 is constructed, the particles 3 one core each 1 of a metal or metal mixture of group A, which at least partially, in particular substantially completely, with an oxide layer 2a . 2 B surrounded by a group B metal or metal mixture. Such a material may consist of both the oxidation of nanoparticles comprising both Group A metals and Group B metals, as well as the reaction of Group A nanoparticles with a Group B metal compound solution followed by oxidation , getting produced.

Example 1:

Example 1, shown in 6 , is a material that consists of 97 atomic percent platinum and 3 atomic percent rhodium. It forms a porous, slightly sintered structure of nanoparticles, which are essentially particles with a diameter of around 20 nm. This material behaves as a metallic conductor and shows no segregation even at low temperatures.

An exemplary manufacturing method for Example 1 is as follows:
Nanoparticles consisting of 97 atomic percent of platinum and 3 atomic percent of rhodium are applied colloidally in a solvent-dissolved form to a zirconium dioxide surface and dried. The resulting layer is subjected to the second treatment in air as an oxidizing atmosphere at 600 ° C for five hours.

Example 2:

Example 2, shown in 7 , is an electrically conductive material consisting of 81 atomic percent platinum and 9 atomic percent rhodium and 10 atomic percent zirconium, present as zirconium oxide. It forms a porous, slightly sintered structure of nanoparticles, which are essentially particles with a diameter of around 10 nm. This material behaves as a metallic conductor and shows no segregation even at low temperatures.

An exemplary manufacturing method for Example 2 is as follows:
Nanoparticles consisting of 81 atomic percent platinum, 9 atomic percent rhodium and 10 atomic percent zirconium become colloidal, in a solvent dissolved form on a zirconia surface and dried. The resulting layer is first subjected to a first treatment in a non-oxidizing atmosphere comprising 2.5% by volume of elemental hydrogen at 650 ° C for five hours and then in air as an oxidizing atmosphere at 600 ° C for five hours of the second treatment.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2007/0251822 A1 [0003]

Claims (10)

Electrically conductive material comprising cores ( 1 ) of a metal mixture comprising a parent metal and at least one metal additive, wherein the base metal and the at least one metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium, wherein the Base metal is present in a concentration of greater than or equal to 90 atomic percent and wherein the at least one metal additive is present in a concentration of less than or equal to 10 atomic percent, wherein the concentrations of the base metal and the at least one metal additive add up to 100 atomic percent. Material according to claim 1, wherein the cores ( 1 ) of at least one oxide ( 2a . 2 B . 2c ) a metal or metal mixture selected from the group B consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, hafnium, vanadium, niobium, Tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, iridium, palladium and zinc and mixtures thereof are at least partially surrounded. Material according to claim 2, wherein the material consists of interconnected particles ( 3 ) with intervening pores ( 4 ), the particles ( 3 ) each have a core ( 1 ) of a metal or metal mixture of group A, which at least partially with an oxide layer ( 2 B . 2c ) of a metal or metal mixture of group B is surrounded. Material according to claim 3, wherein the between the particles ( 3 ) lying pores ( 4 ) have an average pore size of greater than or equal to 0.3 nm to less than or equal to 50 nm as measured by scanning electron microscopy. Material according to one of claims 1 to 4, wherein the cores ( 1 ) at least partially have a diameter in a range of greater than or equal to 0.4 nm to less than or equal to 100 nm. A material according to any one of claims 1 to 5, wherein the parent metal is platinum and the metal additive is rhodium. Material according to one of claims 1 to 6, wherein the material, based on the total number of metal atoms in the material: Greater than or equal to 60 atomic percent to less than or equal to 99.5 atomic percent of Group A metals, and Greater than or equal to 0.5 atomic percent to less than or equal to 40 atomic percent of Group B metals wherein the sum of the metal atoms of groups A and B together is 100 atomic percent. Process for producing an electrically conductive material, in particular an electrically conductive material according to one of claims 1 to 7, for example an electrode material, comprising the process steps: a1) providing cores ( 1 ) of a metal mixture comprising a parent metal and at least one metal additive, wherein the base metal and the at least one metal additive are selected from the group A consisting of platinum, rhodium, gold, palladium, silver, copper, iridium, ruthenium, osmium, rhenium, the And wherein the at least one metal additive is present in a concentration of less than or equal to 10 atomic percent, the concentrations of the parent metal and the at least one metal additive adding up to 100 atomic percent, and a1a) treating the material from process step a1) at least 200 ° C for 10 minutes, for example at least 500 ° C for at least one hour, for example at least 600 ° C for at least 2 hours, with an oxidizing gas or gas mixture. The method of claim 8, wherein the method comprises the further steps of: a2) providing a metal or metal mixture, for example a metal alloy, selected from group B consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, Scandium, yttrium, lanthanum, the lanthanides, titanium, zirconium, hafnium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, zinc and mixtures thereof on at least part of the surface of the cores ( 1 ), and / or providing at least one compound of a metal or metal mixture selected from the group B consisting of silicon, germanium, tin, boron, aluminum, gallium, indium, beryllium, magnesium, scandium, yttrium, lanthanum, the lanthanides, titanium, Zirconium, hafnium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, zinc and mixtures thereof on at least part of the surface of the cores ( 1 ), and a3) treating the material from process step a2) at least 200 ° C for 10 minutes, for example at least 500 ° C for at least one hour, for example at least 600 ° C for at least 2 hours, with an oxidizing gas or gas mixture , An electrode comprising an electrically conductive material according to any one of claims 1 to 7

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