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
  • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/054—Electrodes comprising electrocatalysts supported on a carrier
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/069—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of at least one single element and at least one compound; consisting of two or more compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
  • C25B11/077—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/095—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one of the compounds being organic
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
  • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
• • 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
  • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
• • 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
  • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
  • H01M4/8668—Binders
• • 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
  • H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
• • 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
  • H01M4/923—Compounds thereof with non-metallic elements
• • 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
• • 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
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/33—Electric or magnetic properties
• • 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

Definitions

• the invention relates to a catalyst system comprising a carrier metal oxide and a metal oxide catalyst material.
• the invention further relates to an electrode which comprises the catalyst system.
• the invention further relates to a fuel cell or an electrolyzer comprising at least one such electrode and a polymer electrolyte membrane.
• efficiencies of only 50-60% are achieved.
• a main reason for this is the high overvoltages of the oxygen reduction reaction on a platinum catalyst. So far, platinum has been considered the best catalyst for reducing oxygen in a fuel cell, but due to its high price it should be avoided or at least used very sparingly.
• Another class of catalysts is represented, for example, by oxide-based compounds.
• US 2015/0 368 817 A1 discloses a catalyst system for the anode side of an electrolyzer, comprising a support and a large number of catalyst particles arranged on the support are.
• the carrier comprises a plurality of metal oxide particles or doped metal oxide particles.
• the catalyst particles are based on noble metals made of iridium, iridium oxide, ruthenium, ruthenium oxide, platinum or platinum black and are therefore correspondingly expensive.
• the particles of the carrier together with the catalyst particles are dispersed in a binder.
• DE 10 2008 036 849 A1 discloses a bipolar plate unit for a fuel cell comprising a base body, an anode-side coating and a cathode-side coating, the coatings being composed differently.
• the cathode-side coating comprises a metal oxide, in particular in the form of tin oxide, which is doped with fluorine.
• An electrically conductive carrier metal oxide is formed with an electrical conductivity oi of at least 10 S / cm, the carrier metal oxide having at least two first metallic elements, which are selected from the group of non-noble metals, and a structure comprising oxide grains with a grain size of at least 30nm,
• An electrically conductive, metal oxide catalyst material is formed with an electrical conductivity 02 of at least 10 S / cm, wherein the catalyst material has at least one second metallic element from the group of non-noble metals, the first metallic elements in the carrier metal oxide and at least one second metallic element is present in the catalyst material in a solid stoichiometric compound or solid homogeneous solution, the Carrier metal oxide and the catalyst material differ in their composition and are each stabilized with fluorine, and
• pzzp point of zero zeta potential
• the catalyst material and the carrier metal oxide form an at least two-phase disperse oxide composite.
• the advantage of the acidic catalyst on the surface is that the oxygen reduction is shifted more easily towards the product (water) in accordance with the law of mass action.
• the catalyst material can be inherently dispersed or coherently dispersed in the carrier metal oxide and / or on a surface of the carrier metal oxide.
• the catalyst system according to the invention manages without noble metals. It is therefore interesting in terms of price and opens up great potential for cost savings, especially in the automotive industry.
• the support metal oxide and the oxidic catalyst material are stabilized by doping with fluorine.
• the proportion of fluorine in the catalyst system is a maximum of 2 mol% based on the oxygen content.
• the fluorine is evenly distributed in the oxide lattice and increases the chemical long time stability and the electrical conductivity of the carrier metal oxide as well as the catalyst material of the catalyst system.
• the first metallic elements for forming the carrier metal oxide comprise at least two metals from the group tin, tantalum, niobium, titanium, hafnium, zirconium.
• the first metallic elements are used in combination, the electrochemical value of which is different.
• the first metallic elements comprise the tin and furthermore at least one metal from the group tantalum, niobium, titanium, hafnium, zirconium. A combination of the first metallic elements tin and tantalum or tin and niobium is particularly preferred.
• Combinations of tin and titanium, tin and hafnium, tin and zirconium, titanium and tantalum, titanium and niobium, zirconium and niobium, zirconium and tantalum, hafnium and niobium or hafnium and tantalum have also been used to form the carrier metal oxide proven.
• the oxidic catalyst material preferably has a structure comprising oxide grains with a grain size in the range from 1 nm to 50 nm.
• the at least one second metallic element of the oxidic catalyst material is preferably formed by at least one non-noble metal from the group tantalum, titanium, niobium, zirconium, hafnium, iron, tungsten. In particular, at least two second metallic elements are used in combination.
• the second metallic elements in particular have an electrochemical valency that is different, such as (Ta, Fe) 20s, (Ti, Fe) 02, (Nb, W) 20s and the like.
• the carrier metal oxide has a first crystal lattice structure comprising first oxygen lattice sites and first metal lattice sites, the carrier metal oxide preferably being doped with at least one element from the group comprising titanium, zirconium on the first metal lattice sites on which the first metallic elements are arranged , Hafnium, vanadium, niobium, tantalum, aluminum, iron, tungsten, molybdenum, iridium, rhodium, ruthenium, platinum. Doping elements are removed chooses whose value is different from the first metallic elements.
• the doping element is preferably installed on a first metal grid position instead of a first metallic element.
• the doping is preferably present in a mole fraction fraction of at most 0.1 of the first metallic elements in the carrier metal oxide.
• the carrier metal oxide has a first crystal lattice structure comprising first oxygen lattice sites and first metal lattice sites, the carrier metal oxide preferably being doped on the first oxygen lattice sites with at least one element from the group comprising nitrogen, carbon, boron.
• the doping element replaces oxygen on a first oxygen lattice site ,
• the doping is preferably present in a mole fraction fraction of at most 0.06, based on non-metallic elements in the carrier metal oxide.
• the catalyst material has a second crystal lattice structure comprising second oxygen lattice sites and second metal lattice sites, the catalyst material preferably being doped on the second metal lattice sites with at least one element from the group comprising titanium, zirconium, hafnium, vanadium, niobium, tantalum, iron, tungsten , Molybdenum, iridium, rhodium, ruthenium, platinum.
• the use of iridium to adjust the electrical conductivity is preferred as a stable generator of oxidic mixed phases.
• Doping elements that are different from the at least one second metallic element are selected.
• the doping element is preferably installed on a second metal lattice site instead of a second metallic element.
• the doping is preferably present in a mole fraction fraction of at most 0.1 of the at least one second metallic element.
• Platinum can additionally be applied to a surface of the catalyst system in a maximum amount of 0.1 mg / cm 2 based on a coating area and regardless of a layer thickness of the catalyst system. This increases the guideline ability of the catalyst system without significantly increasing the costs.
• the object is also achieved for an electrode which comprises a catalyst system according to the invention.
• the current densities achievable with such an electrode are 5 to 8 times higher at a cell voltage in the range from 700 to 800 mV than with the known oxide compounds from the above-mentioned prior art.
• the electrode is designed as a cathode.
• the electrode further preferably comprises at least one ionomer and at least one binder.
• the at least one binder preferably comprises at least one fluorinated hydrocarbon and / or at least one polysaccharide.
• the poly sugar consists of carboxymethyl cellulose and / or xanthan and / or alginate and / or agar-agar and / or another acid-stable poly sugar.
• the electrode preferably has a layer thickness in the range from 0.5 to 20 pm.
• platinum is applied to a free surface of the electrode in a maximum amount of 0.2 mg / cm 2 . This increases the electrical conductivity of the electrode again without significantly increasing its cost.
• the object is further achieved for a fuel cell or an electrolyser in that it is / are formed comprising at least one electrode according to the invention and at least one polymer electrolyte membrane.
• the fuel cell is an oxygen-hydrogen fuel cell.
• the electrode in particular forms the cathode of a cell.
• the electrode is preferably arranged on a cathode side of a bipolar plate, it being possible for a gas diffusion layer to be arranged between the electrode and a metallic carrier plate of the bipolar plate.
• the polymer electrolyte membrane and the ionomer of the electrode are preferably formed from identical materials. This significantly improves the transition of the oxygen ions formed on the surface of the electrode designed as a cathode, that is to say the cathode surface, into the polymer electrolyte membrane and thus the efficiency of a fuel cell or an electrolyser.
• FIG. 3 shows a section III-III through the arrangement according to FIG. 1;
• FIG. 1 shows an electrode 1 on a bipolar plate 2, which has a carrier plate 2a.
• the electrode 1 contains the catalyst system 9 (see FIG. 3) and forms a cathode.
• the electrode 1 has a layer thickness in the range from 1 to 2 pm and in addition to the catalyst system 9 further comprises an ionomer and a binder in the form of agar-agar.
• the bipolar plate 2 has an inflow region 3a with openings 4 and an outlet region 3b with further openings 4 ' , which are used to supply a fuel cell with process gases and to remove reaction products from the fuel cell.
• the bipolar plate 2 also has a gas distributor structure 5 on each side, which is provided for contact with a polymer electrolyte membrane 7 (see FIG. 2).
• FIG. 2 schematically shows a fuel cell system 100 comprising a plurality of fuel cells 10.
• Each fuel cell 10 comprises a polymer electrolyte membrane 7, which is adjacent on both sides by bipolar plates 2, 2 ' .
• the same reference numerals as in FIG 1 denote the same elements.
• FIG. 3 shows a section III-III through the bipolar plate 2 according to FIG. 1.
• the same reference symbols as in FIG. 1 identify the same elements.
• the carrier plate 2a which is formed here from stainless steel, can be seen, which can be constructed in one part or in several parts.
• a gas diffusion layer 6 is arranged between the carrier plate 2a and the electrode 1, which contains the catalyst system 9. Furthermore, it can be seen that a further anode-side coating 8 of the carrier plate 2a is present.
• This is preferably a coating 8, which is designed according to DE102016202372 A1.
• a further gas diffusion layer 6 ' is located between the coating 8 and the carrier plate 2a.
• the gas diffusion layers 6, 6 ' are electrically conductive, in particular formed from a fiber mat made of carbon material.
• FIG. 4 shows a section through two bipolar plates 2, 2 ′ and a polymer electrolyte membrane 7 according to FIG. 2 arranged between them, which together form a fuel cell 10.
• the same reference numerals as in Figures 1 to 3 denote the same elements. It can be seen that the electrode 1 of the bipolar plate 2 as the cathode and on the other hand the coating 8 of the bipolar plate 2 ' as the anode are arranged adjacent to the polymer electrolyte membrane 7. Furthermore, the gas diffusion layers 6, 6 'can be seen .
• the course of activity of the two oxides at 1500 ° C. in the respective mixed phases is shown in FIG. 6 (J. Am. Ceram. Soc., 95 [12], 4004-4007, (2012)).
• the stable thorelaurite phase SnTa207 is not included in this phase diagram according to FIG. 6.
• the tin is tetravalent in this compound.
• With the solid solution of tin oxide with tantalum oxide the electrical conductivity of the tin oxide is increased drastically.
• tantalum oxide up to the maximum a solubility of 1.1 mol% to tin oxide, electrical conductivities of 7x10 2 S / cm 2 are achieved.
• the composition of the heterogeneous structure can be calculated at given concentrations according to the lever law. For example, if one chooses a total concentration of 10 mol% Ta20s in Sn02, the result is a composition of the heterogeneous structure of 88% Sno, 99Tao, oi02 and 2% SnTa207 as oxide composite.
• the electrically highly conductive tin dioxide phase Sno, 99Tao, oi02 forms the carrier metal oxide and the thoreaulite phase SnTa207 forms the catalyst material, which is finely dispersed in the grain of the carrier metal oxide.
• the excretion conditions are determined on the one hand by the grain size produced and on the other hand by the temperature-time diagram for setting the microstructure. By varying the composition, the ratios of the two phases of the oxide composite change.
• the chemical activities of the first and second metallic elements in the oxides remain unchanged in the two-phase area, as do the respective basic electrical and chemical-physical properties.
• the three-phase limit lengths (“Triple Phase Boundary” lengths) and the energetic surface conditions of the carrier metal oxide can be set via the quantity and size ratios. Since the two phases, i.e. the carrier metal oxide and the catalyst material, are in different crystallographic structures. If they are present, they are inherently dissolved with one another, ie the catalyst material is present as inherently dissolved dispersoids in the carrier metal oxide.
• the individual phases were separated from the two-substance mixture.
• Sn02 with about 1 mol% Ta205 was used as the carrier metal oxide, the mass fraction of this phase being in the range from 70 to 95% by weight.
• Table 1 below shows results on catalyst systems according to the invention. The results were determined by means of a single cell, which consisted of two end plates, two graphite plates, two bipolar plates 2, 2 ' made of graphite, two gas diffusion layers 6, 6 ' , the electrode 1 according to the invention (cathode side), a standard Pt / C -Catalyst (anode side) and a polymer electrolyte membrane 7 was formed from Nafion.
• the process gases, here air and hydrogen, were humidified differently on the cathode side and the anode side.
• the electrode 1 had an electrode area of 30mm x 30mm.
• a reference humidification temperature TB was set at 80 ° C.
• the prepared layer thicknesses of the electrode 1 were in the range from 1 to 5 pm.
• a sintering temperature must be set so high that grain agglomeration is not to be expected later and, on the other hand, the catalyst system is also sufficiently stable for use at lower temperatures. This risk would exist if the mutual solubilities in the a- and ß-phase changed significantly.
• the platinum was deposited on the surface of the coating 6 by means of sputter technology with an area coverage of ⁇ 0.1 mg / cm 2 .
• the platinum cluster sizes were determined from different samples using TEM measurements and X-ray if fractometry.
• Niobium oxide has a somewhat higher solubility in tin oxide than tantalum oxide.
• the limit solubility for niobium oxide is 2.5 at .-%.
• Stable stoichiometric phases SnNb207 (“Froodite”) similar to the thoreaulite phase are formed with niobium oxide.
• the measured activities are lower than with the tantalum-based catalyst systems, which can be explained, among other things, by the different pzzp values. However, it should be noted at this point that the activities depend very much on the manufacturing conditions.
• catalyst systems based on titanium niobium oxide were examined. In order to increase the electrical conductivities, these oxides were doped with iridium. A doping of 0.1 mol% in the catalyst system was sufficient to set electrical conductivities s> 5 * 10 2 S / cm 2 .
• the catalyst system based on Ti-Ta-0 has also proven itself with the setting of the two-phase region on the tantalum oxide-rich ⁇ phase, which is in equilibrium with the stoichiometric phase ThTa20n in the two-phase region.
• a reverse setting was tested here, in which the active ⁇ -phase acts as a carrier metal oxide and the stoichiometric phase is excreted nanodispersed.
• the surface of the coating 6 - as described above - is covered with platinum - metal islands.
• the temperature treatment of the catalyst system has a major influence on the desired results in terms of activity and electrical conductivity of the catalyst system in several respects.
• the density of the carrier metal oxide for example the stoichiometric tin oxide, is set by taking the temperature into account, taking the decomposition pressure of the compound into account at sintering temperatures above 950 ° C.
• the temperature treatment determines the precipitation conditions of the dispersoids, ie the catalyst material.
• pure Ta20s is excreted at the grain boundaries of the tin oxide. It follows from this that the temperature treatment, as described above, must take place in such a way that the phases which are stable for fuel cell operation are established.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Engineering & Computer Science (AREA)
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• General Chemical & Material Sciences (AREA)
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• Organic Chemistry (AREA)
• Inert Electrodes (AREA)
• Catalysts (AREA)
• Fuel Cell (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 2018
  • 2018-07-09 DE DE102018116508.0A patent/DE102018116508A1/de active Pending
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