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
  • H01M4/9025—Oxides specially used in fuel cell operating at high temperature, e.g. SOFC
  • H01M4/9033—Complex oxides, optionally doped, of the type M1MeO3, M1 being an alkaline earth metal or a rare earth, Me being a metal, e.g. perovskites
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/42—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on chromites
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/403—Cells and electrode assemblies
  • G01N27/406—Cells and probes with solid electrolytes
  • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
  • G01N27/4075—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
  • H01B1/08—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances oxides
• • 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 novel electrode material for hydrocarbon sensors and a novel sensor and a method for its production.
• the concentration of unburned fuels in oxygen-containing gases can be determined in the combustion gas stream in m-situ by sensors, such as on a solid electrolyte, e.g. Yttrium stabilized Z ⁇ r ⁇ on ⁇ ox ⁇ d, two Elektro ⁇ en, which react in different ways to the sample gas.
• the potential of one electrode is largely determined by the equilibrium oxygen partial pressure ⁇ es Gaeses, that of the other predominantly determined by the partial pressure of the fuel gas, so that a voltage can be measured between the electrons in the same gas, which depends on the hydrocarbon concentration depends.
• Gold and alloys of gold and platinum are preferably used as CH-sensitive electrodes (e.g. A. Vogel, G. Baier, V. Fisch, Sensors and Actuators 15-16 (1993) 147-150).
• the parameter z is either equal to 0 or is in the range from 0.01 to 0.29, from 0.3 to 0.6 or from 0.19 to 0.4.
• Element A can be present with increasing z m of an oxidic phase next to the mixed oxide, so that the electrode is present as a whole m mixed phase.
• the element o ⁇ er the element B mixture can also be heterogeneous as oxide neoen ⁇ em Mischoxi ⁇ present at a level of 0, 1 to 70. 5
• a sensor according to the invention for combustible gases, in particular for hydrocarbons has a solid electrolyte and at least 2 electrodes, of which at least one electrode contains an electro material with the advantageous features described so far.
• the second electrode has the same chemical composition as the first electrode.
• a good sensitivity to fuel gas is then achieved by providing means for generating a temperature difference between the first and the second electrode.
• the temperature difference between transition metal and B is at least a three- or two-valent redox-stable cation, an electrode with a perovskite structure for an electrochemical sensor can be created which, after sintering on a solid electrolyte or a ceramic carrier material, is stable for a long time even in an aggressive high-temperature environment.
• fuel gas generally means gaseous and oxi ⁇ ieroare components under the operating conditions of the sensor
• element or element mixture A and / or the element or element mixture has a germicidal catalytic activity .
• msoeson ⁇ ere is advantageous if A em element or a mixture of elements from the group manganese, chromium, cobalt, iron, titanium.
• the element or the element mixture B is preferably selected from the group consisting of gallium, aluminum, magnesium, calcium, gadolinium and other redox-stable rare earth elements.
• A is manganese or chromium or a mixture or both and if an element or mixture of gallium, aluminum and magnesium.
• An electrode material has been found to be particularly advantageous, where ⁇ is A and B is gallium.
• Ln is a lanthanide or a mixture of lanthanides, especially lanthanum itself has particularly advantageous properties in the context of the present invention.
• the parameter x is in the range from 0.001 to 3.99, in particular 0.1 to 0.9, preferably 0.1 to 0.8 or 0.2 to - 6 -
• the carrier material can be a solid electrolyte, but it can also directly on an oxide ceramic carrier material, such as. B. AI2O3 can be printed and a solid electrolyte can be arranged above or next to it.
• H 0 and / or organic solvents are advantageous as solvents, hydrophilic or organic solvents can be used.
• a safe, complete oxidation of the electrode material is ensured if the reaction takes place in air or oxygen. If the reaction product forms a sinter cake, an additional annealing step can be carried out after comminuting the reaction product, in which the complete homogeneous reaction of the components is ensured.
• the component Ln: 0 :. can also be a mineral such as cerite for industrial production. A composition which essentially corresponds to monazite is particularly advantageous.
• a sensor according to the invention or a sensor which is produced according to the advantageous method can be used in particular as a hydrocarbon sensor for use in the exhaust gas of a combustion point, the combustion point being an internal combustion engine with internal or external combustion (in particular a gasoline engine or a diesel engine) or a heating system, such as an oil or natural gas heater.
• the combustion point being an internal combustion engine with internal or external combustion (in particular a gasoline engine or a diesel engine) or a heating system, such as an oil or natural gas heater.
• a good hydrocarbon sensitivity can be achieved if the solid electrolyte is from about 8 mole .- * Y: is made: 0 3 ZrO vollstabi ⁇ lêtem. By doping with Y ; 0 ; , empty spaces are generated in the partial oxygen lattice of the solid electrolyte.
• the electrodes are placed on a solid electrolyte with a lower degree of doping at Y : 0 :. or the corresponding proportion of another cation with lower value the first and second electrodes are advantageously between 100 ° C and 200 ° C.
• the second electrode is advantageously of the chemical composition Ln -, C y D0-, where Ln has already been explained above, C em is alkaline earth metal and D is at least trivalent transition metal. C is in particular strontium. D is advantageously manganese and / or chromium. Ln can be a different element or a different element mixture in the second electrode than in the first ⁇ lektro ⁇ e.
• the parameter y is advantageously in the range 0.01 to 0.9, in particular 0.02 to 0.7, 0.05 to 0.5, 0.1 to 0.3 or 0.2
• a method for producing a sensor for combustible gas using an electrode material according to the invention comprises the following steps:
• Example 3 Printing and baking the paste on a carrier material.
• the respective citrate or nitrate conversion of the starting materials can, for example, also be selected as the starting material.
• the compound La 0 gosSrc.oosCrOs from the oxides L3 2 ÜJ H : 0, C ⁇ z0 2 and SrC0 3 is weighed in a stochiometric ratio and mixed 20 mm in a ball mill. The mixture is then converted into air in a aluminum oxide crucible at 1400 ° C. for 20 h. The sinter cake obtained is milled and annealed at 1650 ° C for 30 mm.
• the electrode materials according to Example 1 and Example 2 can in a simple, electronics-compatible layer technology such as. B. screen printing on a solid electrolyte and then used in addition to a so-called equilibrium electrode, for example made of platinum.
• the electrode material according to example 3 forms a mixed oxide of the perovskite type with negligible fuel gas sensitivity and can be used in addition to the electrodes according to example 1 and example 2 instead of the plate electrode.
• the output signal of the sensor according to the invention is essentially dependent on the concentration of fuel gases in this exhaust gas, that is to say of hydrocarbons which have never been completely burnt or afterburned by the catalytic converter.
• the oxides La : 0 were used to produce the compound LaCr - 0 Ga .0 . , H_0, Cr_0. and Ga_0 weighed in a stochiometric ratio and mixed 20 mm in a ball mill. The mixture is then reacted in a sintered corundum crucible at 1400 ° C. for 20 hours in air. The sinter cake obtained is milled and annealed at 1650 ° C for 30 mm. The complete formation of the desired product can be demonstrated with the aid of X-ray diffractometer images.
• the oxides La 2 O-HO, Cr 0 and Al.O are weighed in a stochiometric ratio and mixed 20 mm in a ball mill and reacted in air at 1400 ° C. for 20 hours in a corundum crucible.
• the sinter cake obtained is ground and subjected to an annealing process at 1650 ° C. for 30 mm in order to obtain the desired compound as pure as possible.
• a sensor can be manufactured in which both electrodes are arranged on the same substrate, but a temperature gradient is set via the sensor, so that a temperature difference between the electrodes of 100 K to 150 K results. This temperature gradient can be generated in particular by a heating conductor printed on the carrier material of the sensor.
• This embodiment has the advantage that both electrodes can be applied to the substrate or to the solid electrolytes in one production step.
• the elements with the atomic numbers 57 to 71 are to be considered as lanthanides, the elements with the atomic numbers as trivalent transition metals. - 12 -
• Electrode material according to one of the preceding claims characterized in that B em element or a mixture of elements from the group Ga, Al, Mg.
• Electrode material according to one of the preceding claims characterized in that A is Cr.
• electrode material according to one of the preceding claims, characterized in that B is Ga.
• Electrode material according to one of the preceding claims, characterized in that Ln em element or a mixture of elements from the group La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb or Lu.
• Electrode material according to one of the preceding Ansprü ⁇ che, characterized in that Ln em element or a mixture of elements from the group of rare earth elements and alkaline earth metals.
• Electrode material according to one of the preceding claims, characterized in that x is in the range from 0.001 to 0.99.
• Electrode material according to one of the preceding claims characterized in that x is in the range from 0.01 to 0.9.
• Electrode material according to one of the preceding claims characterized in that x is in the range from 0.1 to 0.8.
• Electrode material according to one of the preceding claims characterized in that x is in the range from 0.2 to 0.5.

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• Measuring Oxygen Concentration In Cells (AREA)
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• 1996
  • 1996-09-25 EP EP96933384A patent/EP0852820A2/de not_active Withdrawn
  • 1996-09-25 JP JP51313297A patent/JP2001513188A/ja active Pending
  • 1996-09-25 WO PCT/EP1996/004184 patent/WO1997012413A2/de not_active Application Discontinuation
  • 1996-09-25 US US09/043,519 patent/US6090249A/en not_active Expired - Fee Related

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