WO2021013565A1

WO2021013565A1 - Method for producing electrically conductive material for use as a pem catalyst material

Info

Publication number: WO2021013565A1
Application number: PCT/EP2020/069387
Authority: WO
Inventors: Markus Widenmeyer
Original assignee: Robert Bosch Gmbh
Priority date: 2019-07-22
Filing date: 2020-07-09
Publication date: 2021-01-28
Also published as: DE102019210825A1

Abstract

The invention relates to a method for producing electrically conductive material based on mischmetal nanoparticles (2) of general formula M₁ H₁ H₂ H₃...-NP, comprising the following steps: providing (22) a first starting compound in the form of heterometal oxide nanoparticles; providing (24) a second starting compound in the form of a metal salt of the elements M₁ = (Pt, Pd, Rh, Ir); producing (26) a mixture comprising the first and second starting compound; and thermally treating (28) the mixture to produce the mischmetal nanoparticles (2).

Description

description

title

Method of making electrically conductive material for use as a

P EM catalyst material

The present invention is based on a method according to the category of the independent method claim and a product according to the category of the independent product claim.

State of the art

Materials for use as P EM fuel cell catalyst material are known from the prior art. In particular, PtCo and PtNi mixed metal catalysts show significant improvements in activity in the oxygen reduction at the cathode of PEM fuel cells. In addition, a smaller amount of expensive precious metals can be used for a given functional requirement. Unfortunately, however, these catalysts tend to oxidize and leach, i.e. leach out the

Non-platinum metal components from the catalyst material. In addition to an associated loss of activity, when using PtCo and PtNi mischmetal catalysts, it cannot be ruled out that larger amounts of nickel or cobalt compounds, some of which are toxic, are released into the environment. Such materials also tend to become coarse and lose their active surface.

Disclosure of the invention

The invention relates to a method having the features of

independent process claim and an electrically conductive material according to the category of the independent product claim. Other features and Details of the invention emerge from the respective subclaims, the description and the drawings. Features and details that are described in connection with the method according to the invention naturally also apply in connection with the product according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

The inventive method according to the main claim is used

especially for use as a PEM fuel cell catalyst material. The advantage of the method is primarily to be seen in the fact that stable catalyst materials of small particle size and high activity, in particular high specific platinum activity, can be produced in a simple, fast and inexpensive manner using non-toxic or less toxic compounds. Thus, PEM fuel cell catalyst material with a size of less than 5 nm can by means of the method according to the invention in one

so-called "one-pot process" and in one

"One-step impregnation process can be produced.

The method according to the invention can preferably be used for the production of electrode materials, in particular

PEM fuel cell catalyst materials can be used. A use for the production of sensor materials or the like is also conceivable.

The method according to the invention for producing electrically conductive material based on mischmetal nanoparticles, in particular based on segregated mischmetal nanoparticles, includes the step of providing a first starting compound in the form of

Heterometal oxide nanoparticles, the step of providing a second starting compound in the form of a metal salt of at least one of the elements Mi = (Pt, Pd, Rh, Ir), the step of producing a mixture comprising the first and second starting compound and the step of a thermal Treatment of the mixture to produce the

Mixed metal nanoparticles. In the context of the invention, when preparing a mixture, the addition of a second starting compound to a first

Starting compound, as well as the addition of a first starting compound to a second starting compound. In addition, a mixture can also be produced by simultaneously adding a first and a second starting compound. In the context of the invention, a heterometal or a heterometal oxide is understood to mean, in particular, a metal or a metal oxide which does not represent or include any of the elements Mi = (Pt, Pd, Rh, Ir). The first output connection can vzw. in the form of heterometal oxide nanoparticles of the elements Hx = (Fe, Co, Ni, Re, Cr, Mo, W, Nb, Ta, Ti, Zr, Hf). The second starting compound in the form of a metal salt of the elements Mi = (Pt, Pd, Rh, Ir) can also, for example, in the form of platinum complexes, such as H ₂ PtCl ₆ , Pt (NOs) ₂ or the like, or for example already in the form of nanoparticles be formed, which then advantageously one

5 nm or less in diameter. It goes without saying that corresponding complexes of the elements Pd, Rh, Ir can also be used as the second starting compound.

In the context of the invention it has been recognized that by the

Process steps according to the invention, segregated mischmetal nanoparticles can be produced in which the atoms of the elements (Pt, Pd, Rh, Ir) are arranged essentially in an outer shell area and the atoms of the at least one heterometallic element are arranged essentially in an inner core area, so that so-called Core-shell nanoparticles can be generated in which there is no or a reduced risk of leaching and the release of toxic compounds due to the arrangement according to the invention. The invention makes use of the fact that the reduction of heterometal oxides is thermodynamically favored by the addition of atoms of the elements (Pt, Pd, Rh, Ir).

With regard to a simple, inexpensive and reproducible production of the electrically conductive material according to the invention, it is proposed within the scope of the invention that the first starting connection is produced from a metal precursor, the metal precursor preferably is first converted into an intermediate stage in the form of a metal diolate compound, in particular in the form of a metal glycolate compound.

For example, by adding diols to a suitable starting compound, a corresponding metal diolate solution can be prepared, vicinal diols, in particular ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol or 2,3-butylene glycol being used can. It is understood that triols or polyols can also be used.

A tungsten diolate solution can be produced from, for example

Tungsten alcoholates (e.g. W (OEt) e) or halides or oxyhalides (e.g. WCI6, WOCI4) can be produced, whereby W compounds of the VI oxidation state can be used. Tungsten is only to be regarded as an example of one of the aforementioned heterometals. Likewise, a

corresponding production of other heterometal compounds take place.

In particular, tungsten oxide, tungstic acid or a tungstate, e.g.

Ammonium tungstate in ethylene glycol can be treated with heat until a clear to slightly cloudy solution is obtained.

The reaction can preferably be carried out at a temperature of 90-200 ° C., in particular 120-190 ° C., for a period of 15 minutes to 30 hours, in particular 1 hour to 8 hours.

Advantageously, a mass fraction of 0.5% to 50%, more preferably 1% to 25% of the tungsten compound, based on WO ₃ , can be used and optionally treated under an inert gas, for example N2.

The system is preferably so open that H2O can escape, which is advantageous since the removal of H2O from the system favors the synthesis of diolates.

Substances that react with water, for example dimethylformamide-dimethylacetal or trimethoxymethane, can optionally also be added. Likewise can Bases added such as NH3, dimethylamine, trimethylamine, triethylamine, tripentylamine,

Decylamine, dimethyldodecylamine, triethanolamine, guanidine and derivatives, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, NaOH or KOH, the bases preferably in a molar ratio: base: tungsten from 1: 100 to 1: 1, more preferably from 1:20 to 1: 4 can be added.

Optionally, any remaining solids can also be removed by filtration or sedimentation, e.g. by centrifugation.

The method described is particularly suitable here for being able to produce particularly durable intermediate stages or connections.

As part of a simple and effective further processing

according to the invention it can also be provided that the intermediate stage by thermal treatment and addition of water in the first

Starting compound is transferred.

The inventive reaction of the metal diolate to be produced in the manner described with water and preferably further diol makes it possible in particular to produce a first starting compound according to the invention.

Furthermore, it can be provided according to the invention that further auxiliary solvents are added to produce the intermediate stage and / or to produce the first starting compound.

Optional ingredients are, for example, a base, an acid, a

Tetraalkylammonium compound, polymers or monoalcohols, these preferably being added in amounts that tungsten in

Tungsten proportions by weight (based on WO3) from 0.2% to 30%, more preferably from 0.5% to 15%, even more preferably from 1% to 10%.

Advantageous proportions by weight of water can also be 0.5 to 25%, more preferably 1% to 18%, in particular 2% to 12%. A base such as NaOH, KOH, NH ₃ , dimethylamine or the like can also advantageously be used in molar proportions to tungsten of 0.01% to 80%, preferably from 0.1% to 40%, more preferably from 1% to 25% will admit.

The solution can be thermally treated, for example, at temperatures from 20 ° C to 250 ° C, more preferably at temperatures from 60 ° C to 220 ° C, in particular at temperatures from 100 ° C to 195 ° C.

The duration of the treatment is preferably 0.2 hours to 200 hours, more preferably 0.5 hours to 100 hours, even more preferably 1 hour to 50 hours.

With regard to the most effective possible mixing of the first and second starting material, the invention can provide that the first starting compound with an average particle size (dso) of less than 50 nm, preferably less than 20 nm, particularly preferably less than 10 nm, in particular of less than 5 nm is provided.

In the context of a simple and effective production of an electrically conductive material, it can furthermore be provided according to the invention that a carrier material is coated with the first and / or second starting compound, the coating preferably taking place wet-chemically. As an alternative to coating or impregnating a carrier material with the second starting compound after coating or impregnating with the first starting compound, the carrier material can also be coated or impregnated with the second starting compound before the carrier material is coated or impregnated with the first

Output connection takes place. The carrier material can preferably be in the form of a carbon carrier or the like with a large surface or with a small diameter. Likewise, e.g.

Silicon wafer, glass or metal surfaces or catalyst materials, such as Al2O3, T1O2, ZrÜ2, WO3, Sn0 ₂ , S1O2, Al-S1O2, the catalyst material preferably having a surface area of at least 1 m ² / g. The coating and / or impregnation is advantageously carried out using a colloidal liquid in which the nanoparticles are dissolved or suspended. By coating or impregnating the carrier material with the first and second

Starting compound, it is particularly possible to achieve an alloy formation between the various metallic elements (Mi and Hx). After impregnating or coating the nanoparticles or the

Metal compounds or the metals on the carrier material, the material can be dried and then thermally treated. The drying can preferably take place at a temperature between room temperature and 250 ° C., in air or another gas, in a gas stream or in a vacuum.

With W0 ₃ nanoparticles or similar metal oxide nanoparticles in the form of a solution, a substrate can be coated or impregnated directly, ie without further modification. Optionally, the solution can be concentrated, for example at 80 ° C. with stirring, for example in a gas stream or in a vacuum, whereby the concentration of the nanoparticles is increased, which can be advantageous for some coating processes.

Other compounds such as alcohols, acid amides,

Acetamide derivatives, lactams, ethers, esters, carboxylic acids, surfactants, polymers or water or the like can be added.

With regard to a particularly simple and effective production of an electrically conductive material, it can be provided according to the invention that a carrier material is coated simultaneously with the first and the second starting compound, the coating preferably being carried out wet-chemically. As part of the simultaneous coating, the first and second

The starting compound is advantageously present in the same solution, such a solution preferably having a proportion of between 0.1 and 50% by weight of the sum of the metallic elements. Solvents that can be used are, for example, water or alcohols, such as, for example, ethanol, propanol, hexanol, 1-methoxyethanol or esters such as ethylene glycol esters or diols such as ethylene or propylene glycol or dimethylformamide, N-methylpyrrolidone or carboxylic acids, amines such as ethylamine , Trimethylamine or triethylamine or ethers such as THF or the like can be used. In a special and preferred embodiment of a simultaneous coating, tungsten oxide nanoparticles are combined with metals or metal oxides of other metals, with the aim of producing corresponding mixed coatings. In a preferred form, suitable for this purpose

Metal precursor compounds are added to the coating liquid.

With regard to improved control of certain reaction properties and with regard to a greater variety of products, the invention can furthermore provide that additives and / or precursor materials are added. The additives can advantageously be in the form of

Surfactants, polymers or complexing agents be formed. The

Precursor materials can, for example, deliberately not be present in the form of nanoparticles and preferably contain no elements from group Mi.

The precursor materials can advantageously be present in the form of compounds such as, for example, Co (NOs) 2, (NH ^ MoC ^, FeCh, SnC, La (NOs) 3, NH4Re04, or the like. It goes without saying that the precursor materials are also to be understood in particular as heterometal atoms according to the invention which, in contrast to the first starting compound, are not in the form of nanoparticles.

In order to have a sufficiently high activity with respect to the production of

To achieve mixed metal nanoparticles, the invention can in particular provide that at least 35 at%, preferably at least 50 at%, in particular at least 65 at% of the heterometal atoms in the form of

Nanoparticles are introduced.

With a view to converting the first and second starting connection to the electrically conductive material according to the invention as effectively as possible, provision can also be made in particular for the thermal treatment to take place at a temperature of at least 300 ° C, preferably at least 500 ° C, in particular at least 700 ° C . To protect the product to be manufactured, provision can also be made for the thermal treatment not to exceed a temperature of 1000 ° C. The temperature can be maintained at over 300 ° C. for at least 30 minutes, preferably at least 60 minutes and are preferably approached by means of a defined ramp with, for example, 10 K / min or 20 K / min. Furthermore, provision can optionally be made for a first thermal treatment between 80 and 300 ° C., in particular between 100 ° C. and 200 ° C., before a second thermal treatment

to be carried out, as a result of which very small, finely dispersed metallic nanoparticles made of platinum or with a high proportion of platinum can form. The

The temperature here can be above 100 ° C. for at least 15 minutes, for example.

After coating a surface or combining the solution with a catalyst material, the volatile constituents can first of all be removed by heating, blowing over with gas and / or applying a vacuum before the actual thermal treatment.

One example is the removal of the volatile constituents at 10 ° C. to 300 ° C., preferably 50 ° C. to 200 ° C., in air or N2.

Then the coated or impregnated material can be used

Maximum temperatures of 100 to 1500 ° C., preferably 180 ° C. to 1200 ° C., more preferably 350 ° C. to 1100 ° C. for a period of 1 minute to 100 hours, more preferably 20 minutes to 20 hours.

The aforementioned maximum temperatures can preferably be defined in

Ramps can be approached, e.g. from 10 K / min, 2 K / min or 40 K / min.

The baking conditions have an influence in particular on the size of the nanoparticles produced. If, for example, pure tungsten oxide nanoparticles are to be deposited on surfaces, the size of the resulting nanoparticles can be set by selecting the baking conditions. With mild heating or drying conditions (e.g. below 250 ° C), the small nanoparticles obtained by wet chemical processes usually remain small (e.g. below 5 nm).

In the context of a reduction of the first starting compound, provision can also be made for the thermal treatment to take place in a non-oxidizing atmosphere. With regard to an even more effective reduction, In particular the first starting compound, it is also conceivable to carry out the thermal treatment in a reducing atmosphere, for example in a CO, H2, HCOOH or methane atmosphere, the aforementioned gases being typical carrier gases such as Ar or N2

or can be used as clean gases and in particular in a

Concentration between 2 vol .-% and 100 vol .-% of the reducing species can be used. The reducing atmosphere can optionally be used with pressures of over 1 bar to reduce the

Effectively reduce metal precursors to metal. For example, hydrogen at 10 bar or at 50 bar can be used for the reduction.

The composition of the mischmetal nanoparticles in particular can be modified by the selection and conditions of the combined compounds.

For example, tungsten oxide / metal oxide mixed coatings can be produced if metal precursor compounds are added to the coating liquid and the coated or impregnated substrate is tempered only slightly or in a non-reducing manner. Examples of

Precursor compounds (Ei) are: Compounds that contain alkali, alkaline earth or rare earth metals or compounds of metals such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mn, Re, Fe, Co, Ni, Cu, AI, Ga, In or from semi-metals such as B, Si, Ge.

Compounds of these elements can, for example, oxides, hydroxides, alkoxides, halides, carbonates, hydrogen carbonates, nitrates, nitrites,

Be phosphates, carboxylates, acetylacetonates, zirconates or phosphates.

Tungsten oxide-metal mixed systems, on the other hand, can be formed, for example, if a metal is more noble than tungsten

Metal precursor compounds are added and only moderately reducing, neutral or oxidizing tempering conditions are set. The group of metals that are more noble than tungsten (E2) are, for example, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au. Finally, tungsten-metal mixed metal systems can be produced if metal precursor compounds of noble metals from group E2 are added to the coating liquid (e.g. platinum, palladium, copper, cobalt or nickel complexes or salts) and the coated or impregnated substrate in a reducing gas atmosphere is tempered.

It is also possible to add base metals, i.e. at least one from the element group egg.

The ratio of tungsten to an E2 element for tungsten oxide-metal mixed systems or tungsten-metal mixed metal systems W / E2 can preferably be 0.05 to 50, more preferably 0.1 to 20, even more preferably 0.15 to 10 Metals from group E2 can also be partially replaced by metals from group Ei. The degree of replacement is preferably a maximum of 50%, more preferably a maximum of 25%. examples are

Metal mixtures of 65% W and 35% Pt, 50% W, 40% Pt and 10% Ti or 33% W and 67% Pd.

The invention also relates to an electrically conductive material based on mixed metal nanoparticles, in particular segregated ones

Misch metal nanoparticles of the general formula Mi Hi H2 H3 ...- NP, where Mi is an element from the group Pt, Pd, Rh, Ir and Hx is a heterometallic element, the mischmetal nanoparticles having an inner core area and an outer shell area, wherein the atoms of the element from the group Mi = Pt, Pd, Rh, Ir are arranged essentially in the outer shell area and the atoms of the at least one heterometallic element are arranged essentially in the inner core area of the nanoparticles. The electrically conductive material according to the invention thus has the same advantages as already detailed in relation to the method according to the invention

Manufacture of an electrically conductive material have been described. Under an arrangement according to the invention essentially in the inner core area or an arrangement according to the invention essentially in the outer

In the context of the invention, the shell area is understood to mean, in particular, an arrangement of at least 70 at% of the number of atoms in question in the corresponding area, so that according to the invention in particular at least 70% of the platinum atoms are arranged in the outer shell area and at least 70% of the heterometal atoms are arranged in the inner core area.

With regard to improved stability and activity properties, it is also conceivable according to the invention that the atomic ratio of the

Heterometal atoms Hx to the total number of metal atoms Hx + Mi in the

Misch metal nanoparticles between 10% and 95%, preferably between 20% and 90%, in particular between 30% and 85%.

In the context of a targeted control of product properties, it is also conceivable for the electrically conductive material to additionally comprise metal oxide nanoparticles, the metal oxide nanoparticles preferably being arranged in the inner core area. The metal oxide nanoparticles can preferably be formed in the form of ZrC> 2, Ta2C> 5, WO ₃ or WO _x and in particular be arranged in a “separate” core area. In this way, the mischmetal nanoparticles can, for example, have an outer

Shell area made of platinum or predominantly (> 70 at .-%) made of platinum atoms and have an inner core area which is formed from at least one heterometal. This core area can then advantageously have a further core area which has a metal oxide, for example in the form of ZrC> 2, Ta2C> 5 or WO ₃ or WO _x . Alternatively, an inner core region can be formed from a metal oxide and comprise a first shell, which is formed from Zr _y Pt _z , Ta _y Pt _z or W _y Pt _z (with y = 0.01 - 1, z = 0 - 0, 99) and a second outermost shell, which at least. 70 at .-% is formed from Pt.

Finally, also the subject matter of the invention is a foregoing

described electrically conductive material produced by a method according to a method described above for producing an electrically conductive material.

Further advantages, features and details of the invention emerge from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. There the features mentioned in the claims and in the description can be essential to the invention individually or in any combination.

Show it:

1 shows a schematic representation of a cross section of the structure of a nanoparticle according to the invention according to a first exemplary embodiment as a basis for an electrically conductive material,

2 shows a schematic representation of a cross section of the structure of a nanoparticle according to the invention according to a second exemplary embodiment as a basis for an electrically conductive material,

3 shows a schematic representation of the individual steps of a

Process according to the invention for the preparation of a first starting compound according to the invention,

4 shows a schematic representation of the individual steps of a

Method according to the invention for producing an electrically conductive material according to the invention.

1 shows a schematic representation of a cross section of the structure of a segregated mixed metal nanoparticle according to the invention according to a first exemplary embodiment as a basis for an electrically conductive material. The mischmetal nanoparticle of the general formula Mi Hi H ₂ H ₃ ...- NP comprises in the present case

12 atoms of the group Mi = (Pt, Pd, Rh, Ir) 8, which in the present case are formed from Pt and are arranged in an outer shell region 6, and 7 atoms of a heterometal in the present case formed from W, which are arranged in an inner core region 4. The inventive arrangement of

Heterometallic atoms in the inner core area 4, an oxidation and the process of leaching heteroatoms from a mischmetal nanoparticle can be prevented. All nanoparticles of an electrically conductive material according to the invention should ideally be of the same type and thus also have similar cores.

FIG. 2 shows a schematic representation of a cross section of the structure of a segregated mixed metal nanoparticle according to the invention according to a second exemplary embodiment as a basis for an electrically conductive material. The mischmetal nanoparticle according to the second exemplary embodiment also includes

12 atoms of the group Mi = (Pt, Pd, Rh, Ir) 8, which in the present case are formed from Pt and are arranged in an outer shell region 6, and 6 atoms of a heterometal in the present case formed from W, which are arranged in an inner core region 4 a metal oxide compound arranged centrally in the inner core area 4, which is formed in the present case in the form of a WO3 compound. Such an integration of metal oxide atoms in a centrally arranged innermost core area 4 allows in particular the specific adaptation of properties of the electrical material according to the invention.

3 shows a schematic representation of the individual steps of a method according to the invention for producing a first starting compound according to the invention.

In a first step 20 of the method according to the invention, a metal diolate compound is initially produced, in particular in the form of a metal glycolate compound, by using a suitable metal precursor such as H2WO4, WCI ₆ or W (OEt) ₆ to form a Given diol and treated in heat.

In a second step 22 of the method according to the invention, a metal oxide solution is then produced in that the metal diolate compound produced in step 20 is mixed with a diol and water and other optional additional solvents.

In the third step 24 of the method according to the invention, finally, the production of metal oxide nanoparticles takes place by the production in step 22 Metal oxide solution is thermally treated at temperatures of 70 - 220 ° C for 1 to 20 hours.

1st embodiment of a first output connection:

10 g of H ₂ WO ₄ are stirred in 50 g of ethylene glycol for 3 h at 160 ° C., mass losses after the reaction being compensated for with ethylene glycol, so that 60 g of total mass result.

2.6 g of this tungsten glycolate solution are mixed with 2.6 g of a solution of 0.33% triethylamine in ethylene glycol, before 0.45 g of H2O and 4.35 g of ethylene glycol are added.

The solution contains 4% by weight of tungsten (based on WO ₃ ), 4.5% by weight of H ₂ O and 0.086% by weight of triethylamine (tungsten: triethylamine approx. 20: 1). The rest is ethylene glycol or glycolate units.

The solution is treated in a closed vessel in an oven at 125 ° C. for 12 h.

A yellow, clear solution of very small tungsten oxide nanoparticles with a diameter of approximately 1-2 nm results (see FIG. 4). The solution obtained can be used directly as a coating liquid for coatings when a coating of oxide particles is required.

4 shows a schematic representation of the individual steps of a method according to the invention for producing an electrically conductive material according to the invention.

In a first step 30 of the method according to the invention, the first starting compound is initially provided in the form of

Heterometal oxide nanoparticles, the production of which is described above has been. The first starting compound can advantageously be provided with an average particle size (dso) of less than 50 nm, preferably less than 20 nm, particularly preferably less than 10 nm, in particular less than 5 nm.

In a second step 32 of the method according to the invention, a second starting compound is then provided in the form of a metal salt of the elements Mi = (Pt, Pd, Rh, Ir). The second starting compound can be in the form of platinum complexes, such as H2PtCl6, Pt (NOs) 2 or the like or, for example, already in the form of nanoparticles, which then advantageously have a diameter of 5 nm or less.

In a third step 34 of the method according to the invention, a mixture is finally produced, comprising the first and second

Output compound.

The mixture can be produced in particular by applying the first and second starting compounds to a carrier material.

In the context of a simple and effective production of an electrically conductive material, it can furthermore be provided according to the invention that a carrier material is coated in succession with the first and second starting compound (or vice versa), the coating preferably being carried out wet-chemically.

Alternatively, it can also be provided that a carrier material is coated at the same time with the first and the second starting compound, the coating preferably taking place wet-chemically.

After impregnating or coating the nanoparticles or the

Metal compounds or the metals on a carrier material, the material can be dried and thermally treated in a final step 36. The drying can here preferably at a temperature between room temperature and 250 ° C, in air or another gas, in one

Gas flow or take place in a vacuum.

The thermal treatment takes place at a temperature of at least 300 ° C., preferably of at least 500 ° C., in particular of at least 700 ° C., a temperature of 1200 ° C. preferably not being exceeded. The

The temperature can for example be kept at the minimum temperature or above for at least 30 minutes, preferably at least 60 minutes, and can be approached by means of a defined ramp with, for example, 2 K / min, 10 K / min, 40 K / min.

1st embodiment of an electrically conductive material according to the invention:

10 g of a solution described above as an exemplary embodiment with W0 ₃ nanoparticles in ethylene glycol with 4% by weight of W, a solution of 570 mg of Pt (N0 ₃ ) _{2 is added} with stirring.

This solution is applied to a silicon wafer substrate. The coated substrate is then dried in air at 150 ° C for 30 min.

then heated for 30 minutes at 200 ° C. and then for 1 hour at 650 ° C. in 5% H ₂ in N ₂ .

The result is a highly electrically conductive, metallically reflective layer of a tungsten-platinum mixed metal made of nanoparticles with average diameters of around 5 nm.

By means of the method according to the invention, it is possible in particular to be able to produce stable catalyst materials of small particle size and high activity, in particular high platinum-specific activity, in a simple, fast and inexpensive manner using non-toxic or less toxic compounds.

Claims

Expectations

1. A process for the production of electrically conductive material based on mischmetal nanoparticles (2) of the general formula Mi Hi H2 H3 ...- NP, comprising the steps:

- Providing (30) a first starting compound in the form of

Heterometal oxide nanoparticles,

- providing (32) a second starting compound in the form of a metal salt of the elements Mi = (Pt, Pd, Rh, Ir),

- producing (34) a mixture comprising the first and second starting compounds,

- Thermal treatment (36) of the mixture for the production of

Misch metal nanoparticles (2).

2. The method according to claim 1,

characterized,

that the first starting compound is provided with an average particle size (d 50) of less than 50 nm, preferably of less than 20 nm, particularly preferably of less than 10 nm, in particular of less than 5 nm.

3. The method according to claim 1 or 2,

characterized,

that a carrier material with the first and / or second

Starting compound is coated, the coating preferably being carried out wet-chemically.

4. The method according to any one of the preceding claims,

characterized, that a carrier material is coated simultaneously with the first and the second starting compound, the coating preferably being carried out using a wet chemical process.

5. The method according to any one of the preceding claims,

characterized,

that additives and / or precursor materials are added.

6. The method according to any one of the preceding claims,

characterized,

that at least 35 at%, preferably at least 50 at%, in particular at least 65 at% of the heterometal atoms are introduced in the form of nanoparticles.

7. The method according to any one of the preceding claims,

characterized,

that the thermal treatment takes place at a temperature of at least 300 ° C, preferably of at least 500 ° C, in particular of at least 700 ° C.

8. The method according to any one of the preceding claims,

characterized,

that the thermal treatment takes place under a non-oxidizing, preferably under a reducing atmosphere.

9. Electrically conductive material based on mischmetal nanoparticles (2) of the general formula Mi Hi H ₂ H ₃ ...- NP,

where Mi is an element selected from the group consisting of Pt, Pd, Rh, Ir and Hx

Represents heterometallic element.

10. Electrically conductive material according to claim 9,

characterized,

that the mischmetal nanoparticles (2) have an inner core area (4) and an outer shell area (6), the atoms (8) of the element from the group Mi = Pt, Pd, Rh, Ir essentially in the outer shell area (6 ) and the atoms (10) of at least one

Heterometallic element are arranged essentially in the inner core area (4) of the nanoparticles.

11. Electrically conductive material according to claim 9 or 10,

characterized,

that the atomic ratio of the heterometal atoms Hx (10) to

The total number of metal atoms Hx + Mi in the misch metal nanoparticles (2) is between 10% and 95%, preferably between 20% and 90%, in particular between 30% and 85%.

12. Electrically conductive material according to one of claims 10 or 11, characterized in that

that the electrically conductive material additionally comprises metal oxide nanoparticles (12), the metal oxide nanoparticles (12) preferably being arranged in the inner core area (4).

13. Electrically conductive material according to one of claims 9 to 12,

producible by a method according to one of claims 1 to 8.