Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
  • H01M4/921—Alloys or mixtures with metallic elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
  • B01J23/8913—Cobalt and noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/19—Catalysts containing parts with different compositions
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/14—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of noble metals or alloys based thereon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/8605—Porous electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
  • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
  • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
  • H01M8/1011—Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
  • H01M2004/8689—Positive electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M2008/1095—Fuel cells with polymeric electrolytes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the invention relates to a catalyst comprising an alloy of at least two different metals, wherein at least one metal is a metal of the VIII. Subgroup of the Periodic Table of the Elements according to the old name.
• the invention further relates to a process for the preparation of the catalyst and its use.
• Fuel cells are energy converters that convert chemical energy into electrical energy. In a fuel cell, the principle of electrolysis is reversed.
• the structure of the cells is basically the same for all types. They are generally composed of two electrode layers, an anode and a cathode, where the reactions take place, and an electrolyte between the two electrodes in the form of a membrane. This has three functions. It establishes the ionic contact, prevents the electronic contact and also ensures the separation of the media supplied to the electrode layers.
• the electrode layers are usually supplied with gases or liquids, which are reacted in the context of a redox reaction.
• the anode is supplied with hydrogen or methanol and the cathode with oxygen.
• the electrode layers are usually contacted with electronically conductive gas distribution layers. These are e.g. Plates with a grid-like surface structure consisting of a system of fine channels. The overall reaction can be broken down into anodic and a cathodic sub-step in all fuel cells. With regard to the operating temperature, the electrolyte used and the possible fuels, there are differences between the different cell types.
• GDE gas diffusion electrodes
• the electrolyte Adjacent to the membrane are electrode layers in which there are generally catalytically active species that catalyze the reduction or oxidation reaction.
• the electrolyte present in all fuel cells ensures ionic current transport in the fuel cell. He also has the task of forming a gas-tight barrier between the two electrodes. In addition, the electrolyte guarantees and supports a stable 3-phase layer in which the electrolytic reaction can take place.
• the polymer electrolyte fuel cell uses organic lo nenSermembranen, in the technically realized cases in particular perfluorinated cation exchange membranes, as electrolytes.
• a membrane electrode assembly which is generally composed of a membrane and two electrode layers respectively adjacent to one side of the membrane, is referred to as a membrane electrode assembly or MEA.
• Catalysts containing an alloy of at least two different metals, where at least one metal is a VIII subgroup metal are used e.g. used as electrocatalysts in fuel cells.
• such catalysts are suitable for use as cathode catalyst in direct methanol fuel cells (direct methanol fuel cells, DMFC).
• direct methanol fuel cells direct methanol fuel cells, DMFC.
• cathode catalysts in DMFCs In addition to a high current density for the reduction of oxygen, further requirements are placed on cathode catalysts in DMFCs. In the operation of a DMFC, the diffusion of methanol across the membrane to the cathode (crossover), which occurs when a fuel cell is operated with organic, water-soluble fuels, is problematic.
• the organic molecule at the catalytically active center of the cathode catalyst is burnt with oxygen directly to carbon dioxide and water.
• the active sites occupied by the combustion of organic molecules are no longer available for the actual electrochemical reaction - the electrochemical reduction of oxygen - so that the total activity of the cathode layer decreases.
• the direct oxidation of the organic molecule with oxygen lowers the electrochemical potential of the cathode layer and reduces the total voltage that can be tapped at the fuel cell. Since oxygen reduction and oxidation of the organic molecule occur at the same electrochemically active center, a so-called mixed potential is formed, which is lower than that of the oxygen reduction.
• the driving force (EMF) is lowered, the total cell voltage and thus the power is lowered.
• the cathode catalyst used must therefore be as inactive as possible against the methanol oxidation. That is, it must have a high selectivity for the oxygen reduction over the methanol oxidation.
• Temperature-treated porphyrin-transition metal complexes e.g. from J. Applied Electrochemistry (1998), pp. 673-682, or transition metal sulfides, for example ReRuS or MoRuS systems, as described e.g. from J. Electrochem. Soc, 145 (10), 1998, pages 3463-3471, see e.g. a high current density for the oxygen reduction and show a good tolerance to methanol.
• these catalysts do not achieve the activity of Pt-based catalysts and are also not stable enough to ensure a sufficient current density in the acidic environment of a fuel cell for a long time.
• the object is achieved by a catalyst comprising an alloy of at least two different metals, wherein at least one metal is a metal of the VIII. Subgroup.
• the alloy is present in at least two phases with different degrees of alloying.
• An alloy is a homogeneous, solid solution of at least two different metals, with one element as the basic element and the others as alloying elements.
• the basic element is the element that has the largest mass fraction within the alloy.
• different phases result due to a different composition.
• the proportion of alloying elements in the basic element differs.
• the proportion of the base element is smaller than the proportion of at least one alloying element.
• the catalyst contains an alloy of two different metals, wherein at least one of the two metals is a metal of VIII. Subgroup of the Periodic Table of the Elements according to old name.
• the metal of VIII. Subgroup preferably forms the basic element of the alloy.
• Metals of Group VIII, which are useful, are iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum.
• the base metal of the alloy is particularly preferably platinum or palladium.
• both metals are preferably elements of subgroup VIII of the Periodic Table of the Elements.
• the alloy containing the catalyst selected from the group consisting of PtCo, PtNi, PtFe, PtRu, PtPd, PdFe.
• the alloy is present in at least two phases with different degrees of alloying.
• the individual phases in each case form metal crystallites which lie next to one another in disorder.
• the result is a heterogeneous structure of metal crystallites of the individual phases of the alloy.
• the inventively formed catalyst containing the alloy of at least two different metals, wherein the alloy is present in at least two phases with different degrees of alloying, is stable to acids and has a high current density for oxygen reduction, as desired in direct methanol fuel cells ,
• the catalyst formed according to the invention is also very tolerant of methanol impurities.
• the catalyst has a large specific surface area. This is preferably achieved by the catalyst further containing a carrier, wherein the alloy is applied to the carrier or is heterogeneously mixed with the carrier. To achieve a large surface area, it is preferred if the support is porous
• the catalyst When the catalyst is heterogeneously mixed with the carrier, individual catalyst particles are distributed in the carrier material. When the catalyst is supported on the carrier, individual particles of the catalyst material are generally contained on the carrier surface. Usually, the catalyst is not present as a continuous layer on the support surface.
• Suitable supports are, for example, ceramics or carbon. Particularly preferred as carrier material is carbon.
• the advantage of carbon as a carrier material is that it is electrically conductive.
• the catalyst is used as an electrocatalyst in a fuel Cell is used, for example, as the cathode of the fuel cell, it is necessary that it is electrically conductive to ensure the function of the fuel cell.
• Suitable carrier materials are e.g. Tin oxide, preferably semiconductive tin oxide, ⁇ -alumina, which is optionally C-coated, titanium dioxide, zirconium oxide, silicon dioxide, the latter preferably being highly dispersed, the primary particles having a diameter of 50 to 200 nm.
• Tin oxide preferably semiconductive tin oxide, ⁇ -alumina, which is optionally C-coated, titanium dioxide, zirconium oxide, silicon dioxide, the latter preferably being highly dispersed, the primary particles having a diameter of 50 to 200 nm.
• tungsten oxide and molybdenum oxide which may also be present as bronzes, that is to say as substoichiometric oxides.
• carbon When carbon is used as the material for the carrier, it is preferably present as carbon black or graphite.
• the carbon may alternatively also be present as activated carbon or as so-called nanostructured carbon.
• One representative of the nanostructured carbons are, for example, carbon nanotubes.
• a catalyst layer is applied either to the membrane or to the gas diffusion layer.
• the application of the catalyst layer is carried out by techniques known in the art. Suitable techniques include, for example, printing, spraying, knife coating, rolling, brushing and brushing.
• the catalyst layer can be applied by physical vapor deposition (PVD), chemical vapor deposition (CVD) or sputtering.
• a “DecaT” process in which the catalyst layer is first prepared onto a "release” film and then relaminated onto the membrane, can also be used, for which a homogenized process is applied analogously to the direct application of the catalyst layer to the polymer electrolyte membrane
• at least one catalytic active species optionally applied to a suitable carrier
• at least one ionomer and at least one solvent suitable solvents are water, monohydric and polyhydric alcohols, nitrogen-containing polar solvents, glycols and glycol ether alcohols and glycol ethers.
• Particularly suitable are, for example, propylene glycol, dipropylene glycol, glycerol, ethylene glycol, hexylene glycol, dimethylacetamide, N-methylpyrrolidone and mixtures thereof.
• the phases in which the alloy is present are cubic phases with different lattice constants.
• the lattice constant describes the mean distance of the atoms at the corners of the cubic lattice, which forms the cubic phase. Since different metal atoms each have a different diameter, the lattice constants differ in different composition of the alloy. In this way, the different phases can be characterized.
• the crystallite size of the individual phases is preferably in the range from 1 to 10 nm, particularly preferably 2 to 5 nm.
• the alloy containing the catalyst is a PtCo alloy.
• the phases of the PtCo alloy preferably have lattice constants of 0.388 nm and 0.369 nm. At a grating cost of 0.38 nm, the Co content in the alloy is about 11 atomic percent. The proportion of Co in the alloy with a lattice constant of 0.369 nm is approximately 41 ⁇ 5 atomic percent.
• the further object is achieved by a process for producing a catalyst comprising an alloy of at least two different metals, where at least one metal is a metal of transition group VIII, which comprises the following steps:
• the individual atoms within the metal lattice of the alloy have sufficient mobility to be able to reorient themselves. In this way, it is possible for individual atoms to leave their lattice site and exchange with other atoms.
• Tammann temperature is the temperature at which atoms within the lattice have sufficient mobility to reorient. Usually, the Tammann temperature is at a level of about 30 to 50% of the melting temperature of the alloy.
• the selected temperature at which the alloy is annealed, below the stability limit of the at least two phases with different is different degrees of alloy, which are to be adjusted by the method according to the invention.
• the proportion of the alloying element is greater than the proportion of the alloying element in the low alloying element phase and less than the alloying element content in the alloying element Phase with the larger proportion of the alloying element.
• the ratio of the phases to one another can likewise be adjusted by the proportion of the alloying element in the alloy formed.
• the alloy is formed by any method known to those skilled in the art.
• the at least one further metal is first deposited on the metal of subgroup VIII.
• the deposition of the at least one further metal can take place, for example, in solution.
• metal compounds may be dissolved in a solvent.
• the metal may be bound covalently, ionically or complexed.
• the metal can be deposited, for example, reductively or alkaline by precipitating the corresponding hydroxide.
• the base member i. H. the metal of VIII. Subgroup is first deposited on the carrier. This is preferably the same as described above for the at least one further metal.
• a salt of the base element and then a salt of the alloying element is precipitated. After precipitation, drying and temperature treatment are performed to form the alloy. It is possible that the temperature treatment at the same time includes the annealing in step (b).
• the deposition of the further metal on the metal of the VIII is achieved.
• Subgroup in step (a) by precipitating a corresponding metal salt from a solution in the presence of a carrier. By annealing at a temperature below the melting temperature in step (b), the alloy is formed.
• the solution is preferably filtered off after precipitation and the catalyst is washed.
• the solvent in which the precipitation is carried out any solvent is suitable. It is only necessary to ensure that the salts of the metals that form the alloy dissolve in the solvent.
• Preferred as a solvent is water. Alcohols, especially ethanol, serve to reduce, for example, platinum.
• the precipitation also takes place in aqueous solution, in contrast to platinum, preferably alkaline and not reductive.
• the protective gas in whose presence the drying is carried out is preferably nitrogen or argon. Also, a drying under vacuum is possible. When drying under reducing conditions is desired, drying is generally carried out under a hydrogen atmosphere.
• the hydrogen can be either pure or as a mixture with nitrogen or argon.
• the annealing step is preferably carried out in the presence of hydrogen. Furthermore, however, it is also possible to carry out the annealing step in the presence of nitrogen.
• Pt (NO 2 ) 2 As the salt of the first metal and Co (NO 2 ) 2 as the salt of the second metal.
• carbon black in water is preferably initially introduced in a first step.
• a solution of Pt (NOs) 2 in water and ethanol is combined with the carbon black suspension.
• the resulting reaction mixture is then stirred and then heated. This precipitates on the carbon platinum.
• the precipitated on the carbon platinum is filtered off and then washed with water nitrate-free. Finally, drying takes place under a nitrogen atmosphere.
• the carbon thus produced with platinum precipitated thereon is subsequently placed in water.
• This suspension is a mixture of Co (NO 3) 2 * 6H 2 O dissolved in water was added.
• a soda solution By adding a soda solution, the pH is kept constant. Cobalt precipitates on the platinized carbon.
• the solid is filtered off and then dried under nitrogen atmosphere.
• To produce an alloy on the carbon support the solid is then tempered at elevated temperature. The temperature is preferably above the Tammann temperature of the alloy.
• the temperature treatment is preferably carried out in the presence of nitrogen and hydrogen. After the temperature treatment, preference is given to passivation at room temperature in the presence of a nitrogen and air atmosphere.
• the thermally treated catalyst is preferably slurried in sulfuric acid and stirred under a nitrogen atmosphere.
• sulfuric acid preferably 0 to 1 M, preferably 0.4 to 0.6 M sulfuric acid is used.
• the temperature is in the range between 60 and 100 0 C, preferably between 85 and 95 0 C.
• the catalyst is finally filtered off from the solution and dried under vacuum.
• the catalyst prepared according to the invention is suitable e.g. for use as electrode material in a fuel cell. Suitable fields of application are the electrooxidation of methanol or hydrogen and / or the electroreduction of oxygen. Also for other electrochemical processes, such as the chloralkali electrolysis and water electrolysis, the catalyst of the invention is applicable.
• the catalyst according to the invention can also be used, for example, in auto exhaust gas catalysis, for example as a 3-way catalyst or diesel oxidation catalyst, or for catalytic hydrogenation or dehydrogenation in the chemical industry. These include, for example, hydrogenations of unsaturated aliphatic, aromatic and heterocyclic compounds.
• dehydrations include the dehydrogenation of paraffins, naphthenes, alkylaromatics and alcohols.
• the hydrogenation or dehydrogenation can be carried out both in the gas phase and in the liquid phase.
• the catalyst according to the invention is used for an electrode in a direct methanol fuel cell.
• the electrode for which the catalyst is used is in particular a cathode of the direct methanol fuel cell.
• the catalyst according to the invention exhibits a high current density for the oxygen reduction.
• the catalyst according to the invention is tolerant of methanol impurities. This means that the catalyst according to the invention is essentially inactive towards the methanol oxidation.
• the catalyst thus prepared was examined by X-ray diffractometry.
• double lines occur at 40.3 ° and 41.7 °, at 46.3 ° and 48.5 °, at 68.2 ° and 71.4 °, and at 82.3 ° and 86.6 °, respectively.
• the crystal size and the lattice constant of the two phases can be determined as follows:
• Phase 1 crystallite size 3.0nm; Lattice constant: 0.388nm phase 2: crystallite size 8.4nm; Lattice constant: 0.369nm
• the PtCo / C material ES has not been heat-treated at 600 0 C but under otherwise identical conditions at 400 0 C 271st In this case, it has been shown that no double phase occurs.
• the crystallite size of the single resulting phase is 2.9nm and the lattice constant is 0.38nm.
• This catalyst was also slurried after the thermal treatment with 0.5 MH 2 SO 4 and stirred at 90 0 C under nitrogen for one hour. Finally, the catalyst was filtered off with suction and dried. In the following, the material produced in this way is called ES 275.
• the diffractogram for ES 275 shows only single lines and no appearance of double lines. It can be seen from this that the temperature-treated at 400 0 C material is only single-phase.
• the X-ray diffractogram shows that the material ES 297 no longer shows double lines but only single lines.
• the catalysts ES 275, ES 294, ES 297 prepared according to the preparation example and the two comparative examples were each processed into an ink.
• 6 mg of the catalyst 1 g of 5% strength Nafion solution and 7.07 g of isopropanol were mixed.
• 200 .mu.l of this ink were applied in 20 .mu.l portions of a measuring head with a cross-sectional area of 100 mm 2 of a 3-electrode assembly with a calomel reference electrode to a ring disk electrode and dried with a hot air dryer.
• the methanol tolerance experiments were carried out in 1 MH 2 SO 4 at 70 0 C.
• the electrolyte was saturated with oxygen for one hour before starting the measurement.
• the current density for the oxygen reduction in the inventively prepared catalyst is more than twice as high as in a non-temperature-treated catalyst and still greater than 30% greater than in a catalyst in which the 2. Phase has been dissolved out. Furthermore, it is found that the measured O 2 reduction currents hardly differ in a solution without methanol and in a solution with 0.1 M methanol for the catalyst according to the invention, whereas in the non-temperature-treated catalyst a drop in the current density of about 40% can be observed and the catalyst with the phase leached out shows a drop of about 62%.

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  • 2008-08-01 CA CA2697118A patent/CA2697118A1/en not_active Abandoned
  • 2008-08-01 CN CN200880108470A patent/CN101808734A/zh active Pending
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