WO1999018623A2 - Electrode comportant une couche de particules de catalyseur sensibles au monoxyde de carbone - Google Patents

Electrode comportant une couche de particules de catalyseur sensibles au monoxyde de carbone Download PDF

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Publication number
WO1999018623A2
WO1999018623A2 PCT/DE1998/002953 DE9802953W WO9918623A2 WO 1999018623 A2 WO1999018623 A2 WO 1999018623A2 DE 9802953 W DE9802953 W DE 9802953W WO 9918623 A2 WO9918623 A2 WO 9918623A2
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WO
WIPO (PCT)
Prior art keywords
carbon monoxide
electrode
particles
catalytically active
minimum value
Prior art date
Application number
PCT/DE1998/002953
Other languages
German (de)
English (en)
Other versions
WO1999018623A3 (fr
Inventor
Frank Henglein
Wolfgang Unkauf
Andreas Friedrich
Dieter Meissner
Ulrich Stimming
Roland Vogel
Andrea Marmann
Original Assignee
Forschungszentrum Jülich GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Forschungszentrum Jülich GmbH filed Critical Forschungszentrum Jülich GmbH
Priority to EP98955370A priority Critical patent/EP1029379A2/fr
Priority to AU12239/99A priority patent/AU1223999A/en
Publication of WO1999018623A2 publication Critical patent/WO1999018623A2/fr
Publication of WO1999018623A3 publication Critical patent/WO1999018623A3/fr

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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
    • 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
    • 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
    • H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
    • 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 an electrode which has an electrically conductive substrate. On the substrate are out. Precious metal existing particles brought.
  • the noble metal is catalytically active, e.g. B. to oxidize methanol, hydrogen or carbon monoxide.
  • the invention further relates to the use of a substrate with applied particles consisting of noble metal.
  • Phosphorus fuel cell which comprises a diffusion and a catalyst layer.
  • the catalyst layer has porous bodies on which a catalyst is dispersed.
  • One goal is the economical use of the catalyst material.
  • EP 0 275 466 A1 describes a membrane-electrode structure in which there are catalyst particles with a diameter of up to approximately 1 cm on an ion exchange membrane. The aim is to create suitable membrane electrode assemblies.
  • An electrode of the type mentioned initially comprises an electrically conductive substrate, on which the particles consisting of noble metal are applied.
  • the electrode is used in fuel cells, for example.
  • a fuel cell known for example from the publication DE 42 41 150 Cl, has a layer system consisting of cathode, electrolyte and anode.
  • the cathode becomes an oxidizing agent such as air or oxygen and the anode becomes a fuel, e.g. B.
  • the cathode and anode of a fuel cell generally have a continuous porosity, so that the two operating media, namely the oxidizing agent and the fuel, can be supplied to the active areas of the electrodes and the product water can be removed.
  • PEM fuel cells in which proton-conducting membranes are used as the electrolyte.
  • the operating temperatures are below 130 ° C, so as not to destroy the commonly used Nafion membrane.
  • the fuel is formed in the presence of the fuel
  • Precious metal catalyst Pro_onen The protons pass through the electrolyte and combine on the cathode side with the oxygen from the oxidizing agent to form water. Electrons are released and electrical energy is generated.
  • the electrically conductive, porous electrode in a fuel cell can consist of highly porous carbon. Platinum metals, in particular z. B. platinum or
  • the hydrogen required for a fuel cell can be generated from methanol through an external refor ization reaction.
  • methanol is electrochemically oxidized directly at the anode to protons and CO 2 ; ,
  • the hydrogen-rich gas obtained through a reforming reaction is contaminated with carbon monoxide, among other things.
  • carbon monoxide poisons the catalyst of the anode, in particular at low temperatures of 80 ° C.
  • the performance of the fuel cell drops accordingly.
  • the catalytically active material is therefore as possible applied fine-grained on a substrate. Particle sizes of 2 - 5 nm are common for electrodes for fuel cells.
  • the particle density that is to say the number of particles per unit area, is also regularly low. The individual particles then do not regularly touch each other.
  • the object of the invention is to create an inexpensive, catalytically active electrode with a comparatively good carbon monoxide compatibility.
  • the object of the invention is also to provide an advantageous use.
  • the task is accomplished by a device with the
  • the electrode with the features of claim 1 comprises an electrically conductive substrate.
  • Catalytically active particles consisting of noble metal in particular of platinum metal such as Ru or Pt, are applied to the substrate.
  • the particles are chosen so large and / or applied so densely that there are coherent surfaces consisting of the noble metal which (on average) exceed a minimum value.
  • the minimum value is chosen so that when it is exceeded, the oxidation of carbon monoxide or the carbon monoxide compatibility of the catalytically active particles consisting of noble metal is practically (essentially) constant. If the minimum value is undershot, the oxidation of carbon monoxide or the carbon monoxide compatibility of the catalytically active particles consisting of noble metal deteriorate. The catalytic effect is then reduced comparatively strongly by adsorption of carbon monoxide.
  • z. B the particle density chosen to be comparatively large, so that a comparatively large number of catalytically active particles touch each other. From a sufficiently high density, large, coherent surfaces are then formed which have a minimum size within the meaning of claim 1.
  • the particles can be combined to form agglomerates and thus coherent surfaces with the Form features of the first claim. A high density of the agglomerates is then not necessary.
  • the particle sizes can therefore be chosen so large that the particle surface already has or exceeds the minimum size as claimed.
  • the minimum diameter D ai in the particles or agglomerates is selected such that from D m -, the carbon monoxide compatibility or carbon monoxide oxidation is practically no longer improved with increasing diameter of the particles.
  • diameters that are smaller than D ⁇ - have a significantly poorer carbon monoxide tolerance or
  • Platinum particles are already measurably worse than those of approximately 15 nm large platinum particles. However, a particle size above 15 n no longer changes the carbon monoxide tolerance. It was found that the carbon monoxide compatibility of an electrode with 15 nm catalyst particles applied was equal to that Carbon monoxide compatibility of an electrode made entirely of platinum.
  • the approx. 10 nm or approx. 15 nm large platinum particles can consist of - e.g. B. about 4 nm large - particles to agglomerates.
  • n is accordingly 10 nm to 20 nm.
  • the catalyst particles or agglomerates are applied to the substrate of the electrode with such a high density that there are coherent surfaces with the features as claimed.
  • Carbon monoxide compatibility is improved with increasing density of the catalyst particles on the substrate.
  • Particle density is the number of particles per unit area.
  • a substrate made of carbon with 10 nm platinum particles applied with a low particle density had the same carbon monoxide compatibility as a carbon substrate with 3 nm platinum particles applied with a significantly higher particle density.
  • the oxidation reaction of carbon monoxide depends on the size of the connected surface of the catalyst. If a certain size of the coherent surface is undershot, it deteriorates Oxidation of carbon monoxide-carbon monoxide is then increasingly adsorbed on the catalyst and thus inhibits the catalytic effects. In this sense, the carbon monoxide tolerance decreases.
  • the particles therefore preferably have a maximum diameter D ⁇ ⁇ X , the z. B. a maximum of five times the minimum diameter. Then D-, .x ⁇ 5 • D- ⁇ . D M ⁇ 2 • D ⁇ preferably applies
  • the mean diameters of platinum particles or agglomerates are therefore not larger than approx. 70 to 80 nm, preferably not larger than approx. 40 nm. Otherwise, the provision of large, catalytically active surfaces is comparatively expensive, since a disproportionate amount of precious metal is consumed becomes. For the same reasons, the density of the particles made of noble metal should not exceed a maximum value.
  • a coherent surface should therefore have a maximum size that does not significantly exceed the minimum value.
  • the coherent surfaces of the noble metal particles be at most one order of magnitude
  • the invention is based on the knowledge that catalyst particles consisting of noble metal, the catalytic effects of which can be damaged by carbon monoxide, should in no way be as small as possible and at the same time be applied to a substrate with a low density. If the carbon monoxide compatibility or the oxidation of carbon monoxide is to be optimized, particles are to be applied to a substrate in such a way that there are coherent, in particular closed surfaces of the catalyst or of the catalytically active material which do not fall below a minimum size. Contiguous surfaces that exceed a minimum size within the meaning of the claims can be achieved by means of sufficiently large particles and / or sufficiently large densities of the particles on the substrate.
  • the anode in particular is from
  • the anode preferably has the features as claimed.
  • Carbon monoxide poisoning and the associated loss in performance of the anode catalyst can thus be reduced with little financial outlay.
  • a substrate with the applied particles can advantageously be used for the catalytic oxidation of carbon monoxide.
  • applications are the catalytic oxidation of hydrogen-rich, carbon monoxide-containing synthesis gases or the catalytic oxidation of methanol.
  • the good oxidation of carbon monoxide is of interest in order to maintain the catalytic effect for further oxidation reactions.
  • the catalytic effect is less affected compared to the prior art by carbon monoxide in the hydrogen-rich gas.
  • the substrate does not have to be electrically conductive for this purpose.
  • the use of the substrate for methanol oxidation is advantageous since CO is released during the methanol oxidation.
  • the above is
  • Figure 1 shows an image of an electrode with platinum particles. Shown are platinum agglomerates 1 which are applied to a carbon substrate 2 (light areas). The agglomerates 1 are composed of 4 nm particles. The image also shows dark areas 3, which are formed by boron salts. The boron salts are production-related residues from colloid solutions (see publication "P. R-van Rheenen et al., Journal of solid State chemistry 67, 151-169 (1987)").
  • Figure 2 shows the size distribution of the agglomerates shown in Figure 1.
  • the majority of the agglomerates have a diameter of 15 nm.
  • FIG. 3 shows a photograph of a further substrate consisting of carbon with applied agglomerates consisting of platinum 1.
  • FIG. 4 illustrates the size distribution of the agglomerates 1 shown in FIG. 3. The majority of the agglomerates 1 here have a diameter of 10 nm.
  • the curves shown in FIGS. 5 to 7 were determined as follows. It was in a liquid Electrolytes generates a voltage between a (catalytically active) electrode with the platinum particles 1 and a reversible hydrogen electrode. Depending on the set voltage, the current flow of the electrode was measured with the platinum particles and a third electrode. The third electrode was also in the liquid electrolyte.
  • FIG. 5 shows the course for the catalytically active electrode with the 15 nm agglomerates 1 according to FIG. 1.
  • FIG. 6 shows the course for the catalytically active electrode with the 10 nm large agglomerates 1 according to FIG. 3.
  • FIG. 7 shows the course for a catalytic active electrode with 3 nm agglomerates consisting of platinum, which have been applied with a density corresponding to FIGS. 1 and 3 onto a substrate made of carbon.
  • Figure 5 shows a peak at a voltage of 740 mV.
  • Figure 6 shows a peak at a voltage of 920 mV.
  • Figure 7 shows a peak at a voltage of 1038 mV. If a catalytically active electrode consisting of solid platinum was used, the corresponding peak occurred at a voltage of approximately 740 mV.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Inert Electrodes (AREA)
  • Catalysts (AREA)

Abstract

L'invention concerne une électrode comportant une couche de particules d'un métal précieux. Cette électrode comprend un substrat électroconducteur sur lequel sont déposées des particules de métal précieux, à effet catalytique. La taille moyenne des surfaces contiguës desdites particules de métal précieux dépasse une valeur minimale. Cette valeur minimale est sélectionnée de sorte que la compatibilité desdites particules avec le monoxyde de carbone soit constante dès le dépassement de la valeur minimale. On a constaté que, lorsque cette valeur minimale n'était pas atteinte, la compatibilité du métal précieux, catalytiquement actif, avec le monoxyde de carbone se détériorait. Pour parvenir à des bonnes comptabilités avec le monoxyde de carbone, on utilise la valeur minimale des surfaces contiguës. On peut obtenir de grandes surfaces contiguës au moyen de particules suffisamment grosses et/ou de densités de particules suffisamment élevées. En général, on peut utiliser de façon avantageuse un substrat, sur lequel ont été déposées les particules selon l'invention, pour l'oxydation catalytique de monoxyde de carbone.
PCT/DE1998/002953 1997-10-06 1998-10-05 Electrode comportant une couche de particules de catalyseur sensibles au monoxyde de carbone WO1999018623A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP98955370A EP1029379A2 (fr) 1997-10-06 1998-10-05 Electrode comportant une couche de particules de catalyseur sensibles au monoxyde de carbone
AU12239/99A AU1223999A (en) 1997-10-06 1998-10-05 Electrode with a layer of carbon monoxide-sensitive catalyst particles

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19744028A DE19744028C2 (de) 1997-10-06 1997-10-06 Elektrode mit aufgebrachten, kohlenmonoxidempfindlichen Katalysatorpartikeln sowie deren Verwendung
DE19744028.2 1997-10-06

Publications (2)

Publication Number Publication Date
WO1999018623A2 true WO1999018623A2 (fr) 1999-04-15
WO1999018623A3 WO1999018623A3 (fr) 1999-06-24

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PCT/DE1998/002953 WO1999018623A2 (fr) 1997-10-06 1998-10-05 Electrode comportant une couche de particules de catalyseur sensibles au monoxyde de carbone

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EP (1) EP1029379A2 (fr)
AU (1) AU1223999A (fr)
DE (1) DE19744028C2 (fr)
WO (1) WO1999018623A2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19757320C2 (de) * 1997-12-23 2001-08-02 Forschungszentrum Juelich Gmbh Elektrode mit guter Kohlenmonoxidverträglichkeit für Brennstoffzellen
EP1207572A1 (fr) * 2000-11-15 2002-05-22 Dr. Sugnaux Consulting Electrodes mésoporeuses pour cellules électrochimiques et leur méthode de production

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993004222A1 (fr) * 1990-07-31 1993-03-04 Physical Sciences Inc. Electrode a haute efficacite, a diffusion de gaz et contenant du metal catalytique sur un support, procede de fabrication de ladite electrode et cellule l'utilisant
EP0549543A2 (fr) * 1991-12-04 1993-06-30 Tanaka Kikinzoku Kogyo K.K. Procédé de préparation d'un catalyseur comprenant des particules métalliques finement dispersés sur un support
EP0736921A1 (fr) * 1995-04-05 1996-10-09 Johnson Matthey Public Limited Company Electrode à deux électrocatalyseurs

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU582059B2 (en) * 1986-12-19 1989-03-09 Dow Chemical Company, The A composite membrane/electrode structure having islands of catalytically active particles
CA2139167C (fr) * 1993-12-29 1997-12-02 Keijiro Yamashita Electrode utilisee dans une reaction electrochimique et pile a combustible comportant cette electrode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993004222A1 (fr) * 1990-07-31 1993-03-04 Physical Sciences Inc. Electrode a haute efficacite, a diffusion de gaz et contenant du metal catalytique sur un support, procede de fabrication de ladite electrode et cellule l'utilisant
EP0549543A2 (fr) * 1991-12-04 1993-06-30 Tanaka Kikinzoku Kogyo K.K. Procédé de préparation d'un catalyseur comprenant des particules métalliques finement dispersés sur un support
EP0736921A1 (fr) * 1995-04-05 1996-10-09 Johnson Matthey Public Limited Company Electrode à deux électrocatalyseurs

Also Published As

Publication number Publication date
WO1999018623A3 (fr) 1999-06-24
AU1223999A (en) 1999-04-27
EP1029379A2 (fr) 2000-08-23
DE19744028A1 (de) 1999-04-15
DE19744028C2 (de) 2000-03-09

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