GB2039686A

GB2039686A - Fuel cells

Info

Publication number: GB2039686A
Application number: GB7939281A
Authority: GB
Original assignee: Ford Motor Co Ltd; Ford Motor Co
Current assignee: Ford Motor Co Ltd; Ford Motor Co
Priority date: 1978-11-21
Filing date: 1979-11-13
Publication date: 1980-08-13
Also published as: US4195119A

Description

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SPECIFICATION Fuel cell

5 The present honeycomb structure used by the Ford Motor Company as a substrate for an auto exhaust catalyst has approximately 47 openings per square centimeter of front face surface. These substrates are manufactured from a ceramic material, essential-10 ly cordierite, and are made by an extrusion process. The resultant honeycomb has a plurality of cells which run the axial length of the honeycomb. These cells have a square cross section with an inside dimension of about 1.1 mm and are separated from 15 one another by walls that are 150-250 micron thick. These cell walls are approximately 35-40% porous, with the pores having an average diameter of about 10 micron.

It struck me that a honeycomb structure could be. 20 used as a separator to form an overall lightweight fuel cell. The honey comb separator would be used in a manner such that its cells define a plurality of separate fuel compartments and oxidant compartments. With alternate cells being fuel and oxidant 25 compartments, the structure allows for a high interface area between opposite compartment with considerable overall strength.

I am aware of U.S. patent 3,206,332 for an "Electrolytic Cell Structure". This patent shows an 30 electrolyte-support structure in the form of a plurality of triangular-shaped parallel cells 10 of a ceramic material. The cells 10 are used to support spaced-apart electrodes, one electrode being the right hand electrode identified by the numeral 1 and the other 35 electrode being the left hand electrode identified by the numeral 1'. The right hand electrode is the oxidant electrode, and the left hand electrode is the fuel electrode. The cells 10 are impregnated throughout their entire volume with a suitable electrolyte so 40 that the necessary electrochemical reactions may take place to cause a current to flow to an exterior electrical load. The walls of the cells are made porous so that the oxidation products of the cell may escape therefrom.

45 The 3,206,322 patent does not, in any manner, propose that the electrolyte be retained only in the cell walls of the cells 10 and that the individual volume defined by the various walls of the cells be alternately formed as oxidant compartments and as 50 fuel compartments, as I am teaching in this specification. I am unaware of any proposal to use a honeycomb separator as the device for defining the separate fuel and oxidant compartments of a fuel cell.

55 This application discloses a fuel cell and, more particularly, a fuel cell of high strength which may be built at a relatively low cost.

In accordance with the general teachings of this invention, the fuel cell is formed by the following 60 structure. A honeycomb separator is provided which has a plurality of cells therein to define separate fuel compartments and oxidant compartments. The honeycomb separator is formed of a material having a porosity which allows a capillary transport there-65 through of an electrolyte forthe fuel cell. An electrolyte reservoir is placed in contact with at least a portion of the honey comb separator so that the honeycomb separator may wick the electrolyte throughout its entire extent. A fuel supplying device is provided for supplying a fuel to every other cell in a checkerboard fashion thereby to define fuel compartments in the honeycomb separator.

In a similar manner, an oxidant supply device supplies oxidant to every cell not a fuel compartment thereby to define oxidant compartments in the honeycomb separator. The fuel compartments and the oxidant compartments are in a side-by-side relationship throughoutthe honeycomb separator. An electrode catalyst material is deposited on the walls of the honeycomb separator defining the fuel compartments and the oxidant compartments. Current carrying devices are provided in each of the fuel compartments and the oxidant compartments for providing an electric circuit to the electrode catalyst material in each of the compartments. A first current collecting terminal is connected to each of the current carrying devices located in the fuel compartments of the honeycomb separator to provide a first poleforthefuel cell. In a like manner, a second current collecting terminal is connected to each of the current carrying devices located in the oxidant compartments of the honeycomb separator to provide a second poleforthefuel cell. An exhaust device is provided for removing excess fuel and oxidant respectively from the fuel compartments and the oxidant compartments of the honeycomb separator, as well as oxidant product.

In such a manner, a fuel cell of relatively inexpensive construction can be made. The fuel cell does have the characteristic of excellent strength because of the use of the honeycomb separator.

In accordance with a preferred embodiment of this invention, the honeycomb separator is formed from a separator material such as used to form the substrate for a catalytic device associated with an automobile engine.

The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of the specific embodiment when read in conjunction with the accompanying drawing which is an elevational view, mostly in cross section, of a fuel cell constructed in accordance with the teachings of this invention.

Afuel cell, generally identified by the numeral 10, is shown in the associated drawing, this fuel cell includes a honeycomb separator 12 having a plurality of walls 14-14throughoutthe entire extent thereof. The drawing shows only the first row of walls, other rows being in front and behind the row shown. In accordance with the teachings of this invention, the walls of the honeycomb separator are formed of a material having a porosity which allows a capillary transport therethrough of an electrolyte.

In accordance with the teachings of the preferred embodiment of this invention, the honeycomb separator 12 is a substrate such as is used for

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exhaust gas catalysts for automotive engines. A particular type of substrate manufactured by an extrusion process would have 47 cells per square centimeter of front face, the individual cells are the 5 volumes defined between the cell walls 14-14. The cells run the axial length of the honeycomb separator and have a square cross section with an inside dimension of 1.1 mm, and are separated from one another by the walls 14-14 that are 150-250 microns 10 thick with a porosity in the range of 35-40%. The pore diameter for the porosity is generally in the range of about 10 micron. Normally, these honeycomb separators are made from a ceramic material such as cordierite.

15 In general, however, the requirements of the honeycomb separator are that it be made from a material having a porosity sufficient to permit the wicking of an electrolyte therethrough. The material must also be resistant to any chemical attack thereon 20 by the electrolyte. Other materials which maybe suitable for the honeycomb separator are materials such as plastics, such as Teflon. Also, the cell density and wall thickness may be varied to achieve the electrical characteristics desired from the particular 25 fuel cell.

An electrolyte reservoir 16 is defined by electrolyte confining walls 18. In accordance with the preferred embodiment, the electrolyte reservoir 16 contains a sulfuric acid electrolyte material, for example, a 30 sulfuric acid having an acid concentration of 35 weight percent. The porosity of the honeycomb separator 12 permits a wicking of the electrolyte material from the reservoir throughout the honeycomb separator so that all of the cell walls 14-14 35 contain the electrolyte material generally throughout their entire extent.

On top of the honeycomb separator 12 there is provided a current collecting structure, generally identified by the numeral 20. The full construction of 40 this structure will be defined at a later time. It is only of interest to indicate now that this structure has a plurality of passageways 22-22 extending therethrough, each passageway being associated with a volume defined between the walls 14-14 of the 45 honeycomb separator 12.

A fuel supply header, generally designated by the numeral 24, is located on top of the current collecting structure 20. The fuel supply header 24 has an inlet pipe 26 through which a fuel, such as hydrogen, 50 is supplied. The inlet pipe is connected to a plurality of distribution chambers 28, which chambers are connected by means of alternate passageways 22-22 of the current collecting structure 20 to alternate cells of the honeycomb separator 12 which are 55 hereinafter referred to as fuel compartments 30-30.

In a similar manner, an oxidant supply header, generally identified by the numeral 32, is also provided. This header has an inlet pipe 34 for supplying an oxidant such as oxygen to a distribu-60 tion chamber 36. The distribution chamber 36 of the oxidant supply header 34 is connected by a plurality of passageways 38 formed in the fuel supply header 24 and alternate ones of the plurality of passageways 22-22 formed in the current collecting structure 65 20 to compartments in the honey separator which are hereinafter identified as oxidant compartments 40-40.

In such a manner, fuel compartments 30-30 and oxidant compartments 40-40 are located in a checkerboard fashion next to one another throughout the entire extent of the honeycomb separator 12. The fuel compartments are filled from top to bottom with a fuel such as the mentioned hydrogen, while the oxidant compartments are filled from top to bottom with an oxidant material such as the mentioned oxygen. The compartments are separated by the walls 14 which contain the electrolyte material which permits generation of a current by means of an oxidation taking place of the fuel in the medium of the electrolyte.

In order to permit the carrying out of the mentioned reaction, it is necessary that the fuel compartment walls and the oxidant compartment walls be lined with a suitable electrode catalyst material. In accordance with the teachings of the preferred embodiment of this invention, the walls of the fuel compartments 30-30 and oxidant compartments 40-40 are coated with an electrode catalyst material 42.

In accordance with the teachings of this disclosure, the electrode catalyst 42 is applied as a wash-coat to the different compartments. A different catalyst material may be applied to alternate compartments by use of a suitable plug to first plug off one set of compartments, while the other is being treated, and then a reversing of that procedure, for example, the fuel compartment may be treated with an electrode catalyst material such as carbon and platinum, while the oxidant compartments are treated with a material such as carbon and platinum.

The porisity of the walls 14-14 of the honeycomb separator 12 dictate the particular size of the catalyst material which may be used therein. If the electrode catalyst material 42 is too small, it can penetrate from one compartment to the other thereby setting up a partial short of the fuel cell. This is undesirable and must be prevented. One way of accomplishing this is by the use of fuel porosity walls. The particular structure can be formed by making the original walls 14-14 of the honeycomb separator so as to have a small pore size and, thereafter, applying a coarse ceramic washcoat material thereto followed by a resintering of the entire body. This action gives the wall an outer large pore size with a small interior pore size, the outer pore being used to accommodate and hold a large size particle of the electrode catalyst material.

Electrical contact is made to the electrode catalyst 42 in each of the fuel compartments 30-30 and oxidant compartments 40-40 by means of a small wire 44-44 located in each of the compartments. This small wire may be made from a material such as nickel.

As previously mentioned, the cell of this structure includes the current collecting structure 20. This structure includes an upper current collecting terminal 46 and a lower current collecting terminal 48. The upper terminal is connected by means of the small wires 44-44 to the electrode catalyst 42-42 located in the fuel compartments 30-30. In a similar

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manner, the lower terminal 48 is connected by the small wires 44-44 to the electrode catalyst 42-42 located in each of the oxidant compartments 40-40. In this manner, the upper terminal and the lower 5 terminal provide the two poles of the cells 10 which may be connected to a load such that the power generated within the fuel cell by oxidation of the fuel may be consumed by the load to accomplish a desired function.

10 A fuel exhaust header 50 is provided to remove any extra fuel from the fuel compartments 30-30. The construction of the fuel exhaust header 50 is similarto the construction of the fuel supply header 24 and no further discussion thereof will be under-15 taken herein. The fuel exhausted from the cell may be passed through ay suitable treatment device to remove extra moisture therefrom and the fuel thereafter returned to the device which supplied the fuel to the inlet pipe 26 of the fuel supply header 24. 20 In a similar manner, an oxidant exhaust header 52 is also provided to remove excess oxidant from the oxidant compartments 40-40. The oxidant may also be recycled to the inlet pipe 34 after it has been dried. During the reactions of a fuel cell, moisture is 25 generated and this should be removed from the exhausted fuel and oxidant materials if they are to be recycled.

The exterior surface of the cell 10 may be sealed with a plastic sealant 54 in order to produce a 30 finished fuel cell structure.

While a preferred embodiment of the invention has been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from 35 the invention, and it is intended to cover in the appended claims all such modifications and equivalents as fall within the true spirit and scope of this invention.

What is claimed is:

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Claims

CLAIMS 1. A fuel cell comprising:

a honeycomb separator having a plurality of walls 45 which form cells thereby to define a plurality of separate fuel compartments and oxidant compartments, said walls of said honeycomb separator being formed of a material having a porosity which allows a capillary transport therethrough of an 50 electrolyte;

an electrolyte reservoir in contact with at least a portion of said honeycomb separator;

a fuel cell electrolyte in said reservoir, said fuel cell electrolyte being wicked into said walls of said 55 honeycomb separator;

fuel supply means for supplying fuel to every other cell in a checkboard fashion thereby to define fuel compartments in said honeycomb separator; oxidant supply means for supplying oxidant to 60 every cell notafuel compartment thereby to define oxidant compartments in said honeycomb separator, said fuel compartments and said oxidant compartments being in a side-by-side relationship throughout said honeycomb separator; 65 electrode catalyst material deposited on said walls of said honeycomb separator defining said fuel compartments and said oxidant compartments;

current carrying means in each of said fuel compartments and said oxidant compartments for 70 providing an electrical circuit to said electrode catalyst material in each of said compartments;

a first current collecting terminal means connected to each of said current carrying means located in said fuel compartments of said honeycomb separ-75 atorto provide a first pole for said fuel cell;

a second current collecting terminal means connected to each of said current carrying means located in said oxidant compartments of said honeycomb separator to provide a second pole for said 80 fuel cell; and exhaust means for removing oxidation products and excess fuel and oxidant respectively from said fuel compartments and said oxidant compartments.
2. The fuel cell of Claim 1 wherein: said hon-85 eycomb separator is formed of a ceramic material.
3. The fuel cell of Claim 2 wherein: said ceramic material is cordierite.
4. The fuel cell of Claims 1,2 or 3 wherein, said fuel is hydrogen, said oxidant is oxygen, and said

90 electrolyte is sulfuric acid.

Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited, Croydon Surrey, 1980.

Published by the Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.