EP0569062A2
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EP
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Method of making membrane-electrode assemblies for electrochemical cells and assemblies made thereby
Assignee: Motors Liquidation Co
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Filing: 1993-03-10
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Granted: —
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Expires: 2013-03-10
Abstract
Abstract There is provided a combination, unitary, membrane and electrode assembly (12) with a solid polymer electrolyte membrane (46), and first and second electrodes (42,44) at least partially embedded in opposed surfaces (50,52) of the membrane (46). The method leads to a very significant increase in catalyst utilization. The electrodes (42,44) each comprise a respective group of finely-divided carbon particles (60), very-finely divided catalytic particles (62) supported on internal and external surfaces of the carbon particles (60) and a proton-conductive material (64) intermingled with the catalytic and carbon particles (60,62). A first group of finely-divided carbon particles (60) forming the first electrode (42) has greater water-attraction and water-retention properties and is relatively more hydrophilic and less hydrophobic than a second group of finely-divided carbon particles (60) forming the second electrode (44). In a preferred method, the membrane electrode assembly (12) of the invention is prepared by forming a slurry of proton-conductive material (64) and at least one group of finely-divided carbon particles (60) and very finely-divided catalytic particles (62) supported on and in the carbon particles (60). The slurry is applied to the opposed surfaces (50,52) of the membrane (46); and heated whilst being pressed to the membrane (46) for a time and at a temperature and under a compressive load sufficient to embed at least a portion of the particles (60,62) into the membrane (46) to thereby form a membrane electrode assembly (12).
Inventors
- 👤 Sundararajan Swathirajan
- 👤 Youssef Morcos Mikhail
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 19:32
CPC Classifications
H; H01; H01M; H01M4/00; H01M4/86; H01M4/96; C; C25; C25B; C25B9/00; C25B9/17; C25B9/19; C25B9/23; H01M8/00; H01M8/10; H01M8/1004; H01M8/04; H01M8/04291; Y; Y02; Y02E; Y02E60/00; Y02E60/30; Y02E60/50; Y02P; Y02P70/00; Y02P70/50
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
187 words
A combination electrolyte and electrode structure (12) for an electrochemical cell comprising: a solid proton-conductive polymer electrolyte membrane (46) having first and second spaced-apart opposed surfaces (50,52) and an intermediate region (53); and first and second electrodes (42,44) each adhered to a respective one of the first and second surfaces (50,52) of the membrane (46); characterised in that the first and second electrodes (42,44) respectively comprise first and second groups of carbon particles (60), each one of the carbon particle groups including a plurality of the carbon particles (60) having internal and external surfaces defining a plethora of pores within and between the carbon particles (60), very finely-divided catalytic particles (62) supported on the internal and the external surfaces of the carbon particles; and a proton-conductive material (64) intermingled with the carbon particles (60) and the catalytic particles (62); the first group of carbon particles (60) forming the first electrode (42) are relatively more hydrophilic than the second group of carbon particles (60); and a portion of the carbon particles (60) forming a respective one of the electrodes is at least partially embedded in the membrane (46).
Claim 2
Dependent Claim
55 words
A combination electrolyte and electrode structure (12) according to claim 1, in which the first and second carbon particle groups are each characterized by a degree of acidity or basicity, and in which the first group of carbon particles (60) is relatively more acidic or less basic than the second group of carbon particles (60).
Claim 3
Dependent Claim
56 words
A combination electrolyte and electrode structure (12) according to claim 1, in which each one of the first and second carbon particle groups is characterized by a pH value, and in which the first group of carbon particles (60) has a pH value less than the pH value of the second group of carbon particles (60).
Claim 4
Dependent Claim
61 words
A combination electrolyte and electrode (12) structure according to claim 1, in which each one of the carbon particle groups has pores with an average size in the range of between about 5 to about 20 nm (about 50 to about 200 Angstroms), and at least about 40% of the pores having a size greater than about 2 nm (20 Angstroms).
Claim 5
Dependent Claim
54 words
A combination electrolyte and electrode structure (12) according to claim 3, in which the first group of carbon particles (60) has a pH value in the range of about 6 to about 7 and the second group of carbon particles (60) has a pH value in the range of about 8 to about 10.
Claim 6
Dependent Claim
71 words
A combination electrolyte and electrode structure (12) according to claim 4, in which the first group of carbon particles (60) has an average pore size in the range of about 9 to about 11 nm (about 90 to about 110 Angstroms) and the average pore size of the second group of carbon particles (60) is in the range of about 6 to about 8 nm (about 60 to about 80 Angstroms).
Claim 7
Dependent Claim
69 words
A combination electrolyte and electrode structure (12) according to claim 1, in which the catalytic particles (62) of the first and second electrodes (42,44) are each formed of platinum, and wherein the platinum loading of the second electrode (44) is less than about 0.07 milligrams per cm² of electrode surface area, and the platinum loading of the first electrode (42) is less than that of the second electrode (44).
Claim 8
Dependent Claim
77 words
A combination electrolyte and electrode structure (12) according to claim 1, further comprising first and second sheets of graphite paper (80,82) impregnated with polytetrafluoroethylene, the first group of carbon particles (60) being disposed between the first surface (50) of the membrane (46) and the first sheet of graphite paper (80), and the second group of carbon particles (60) being disposed between the second surface (52) of the membrane (46) and the second sheet of graphite paper (82).
Claim 9
Dependent Claim
53 words
A combination electrolyte and electrode structure (12) according to claim 1, in which the catalytic particles (62) are platinum supported on the carbon particles (60) in a proportion based on 100 parts by weight, where the platinum particles (62) constitute up to about 15 parts and the carbon particles (60) the balance thereof.
Claim 10
Dependent Claim
25 words
A combination electrolyte and electrode structure (12) according to claim 1, in which the proton-conductive material (64) consists essentially of a perfluorocarbon sulphonic acid polymer.
Claim 11
Dependent Claim
29 words
A combination electrolyte and electrode structure (12) according to claim 1, in which the proton-conductive material (64) consists essentially of a mixture of perfluorocarbon sulphonic acid polymer and polytetrafluoroethylene.
Claim 12
Dependent Claim
28 words
A combination electrolyte and electrode structure (12) according to claim 1, in which the electrolyte membrane (46) and the proton-conductive material (64) each comprise perfluorocarbon sulphonic acid polymer.
Claim 13
Dependent Claim
63 words
A combination electrolyte and electrode structure according to claim 1, in which each one of the electrodes (42,44) is formed of the proton-conductive material (64) and the catalytic and carbon particles (60,62) in a proportion based on 100 parts thereof, there being about 30 to about 50 parts proton-conductive material (64) present, with the balance thereof being the catalytic and carbon particles (60,62).
Claim 14
Dependent Claim
131 words
A method of making a combination electrolyte and electrode structure (12) for an electrochemical cell according to claim 1, characterised in that the method comprises: forming a slurry of proton-conductive material (64) and at least one group of finely-divided carbon particles (100) and very finely-divided catalytic particles (62) supported on and in the carbon particles (60); applying the slurry onto a first surface (50) of the membrane (46); applying the slurry onto a second surface (52) of the membrane (46); and heating the applied slurry whilst pressing the applied slurry for a time and at a temperature and under a compressive load sufficient to embed at least a portion of the particles (60,62) in, respectively, the surfaces (50,52) of the membrane (46) to thereby form the first and second electrodes (42,44).
Claim 15
Dependent Claim
32 words
A method according to claim 14, in which the compressive load applied is in the range of about 70.304 to about 140.607 Kg/cm² (about 1,000 to about 2,000 pounds per square inch).
Claim 16
Dependent Claim
22 words
A method according to claim 14, in which the time is in the range of about 1 minute to about 5 minutes.
Claim 17
Dependent Claim
20 words
A method according to claim 14, in which the temperature is in the range of about 120°C to about 150°C.
Claim 18
Dependent Claim
39 words
A method according to claim 14, in which, before the step of heating whilst pressing, the applied slurry is dried by heating for a time and at a temperature sufficient to vaporize any volatile liquid components of the slurry.
Claim 19
Dependent Claim
194 words
A method of making a combination electrolyte and electrode structure (12) for an electrochemical cell according to claim 1, characterised in that the method comprises the steps of: forming a first slurry of proton-conductive material (64) and at least one group of finely-divided carbon particles (60) and very finely-divided catalytic particles (62) supported on and in the carbon particles (60); forming a second slurry of proton-conductive material (64) and at least one group of finely-divided carbon particles (60) and very finely-divided catalytic particles (62) supported on and in the carbon particles (60), the group of particles (60,62) in the second slurry being more basic or less acidic than the group of particles (60,62) in the first slurry; applying the first slurry onto a first surface (50) of the membrane (46); applying the second slurry onto a second surface (52) of the membrane (46); and heating the applied slurry whilst pressing the applied slurry for a time and at a temperature and under a compressive load sufficient to embed at least a portion of the particles (60,62) in, respectively, the surfaces (50,52) of the membrane (46) to thereby form the first and second electrodes (42,44).
Claim 20
Dependent Claim
101 words
A method according to claim 19, in which the step of applying the first slurry is conducted by coating the first slurry onto a surface of a first sheet of polytetrafluoroethylene-impregnated graphite paper (80) and then placing the coated surface in contact with the first surface (50) of the membrane (46); and in which the step of applying the second slurry is conducted by coating the second slurry onto a surface of a second sheet of polytetrafluoroethylene-impregnated graphite paper (82) and then placing the coated surface of the second sheet in contact with the second surface (52) of the membrane (46).
Claim 21
Dependent Claim
72 words
A method according to claim 19, in which the first group of the finely-divided carbon particles (60) has an average pore size in the range of about 9 to about 11 nm (about 90 to about 110 Angstroms), and in which the average pore size of the second group of the finely-divided carbon particles (60) is in the range of about 6 to about 8 nm (about 60 to about 80 Angstroms).
Claim 22
Dependent Claim
74 words
A method according to claim 19, in which each one of the first and second groups of the finely-divided carbon particles (60) is characterised by a pH value, and in which the first group of finely-divided carbon particles (60) has a pH value in the range of about 6 to about 7 and the second group of finely-divided carbon particles (60) has a pH value in the range of about 8 to about 10.
Claim 23
Dependent Claim
66 words
A method according to claim 19, in which the catalytic particles (62) of the first and second slurries are each of platinum, and wherein the second slurry has a concentration of platinum sufficient to provide a platinum loading less than about 0.07 milligrams per cm² of electrode surface area, and wherein the platinum concentration of the first slurry is less than that of the second slurry.
Claim 24
Dependent Claim
51 words
A method according to claim 19, in which the very finely-divided catalytic particles (62) are of platinum supported on the carbon particles (60), and, in a proportion based on 100 parts by weight, the platinum particles constitute up to about 15 parts and the finely-divided carbon particles (60) constitute the balance.
Claim 25
Dependent Claim
23 words
A method according to claim 19, in which the electrolyte membrane (46) and the proton-conductive material (64) each comprise perfluorocarbon sulphonic acid polymer.
Claim 26
Dependent Claim
55 words
A method according to claim 19, in which each one of the slurries consists essentially of the proton-conductive material (64) and the catalytic and carbon particles (60,62) in a proportion based on 100 parts, of about 30 to about 50 parts proton-conductive material (64) and the balance thereof being the catalytic and carbon particles (60,62).
Claim 27
Dependent Claim
20 words
A method according to claim 19, in which the temperature is in the range of about 120°C to about 150°C.
Claim 28
Dependent Claim
32 words
A method according to claim 19, in which the compressive load applied is in the range of about 70.304 to about 140.607 Kg/cm² (about 1,000 to about 2,000 pounds per square inch).
Claim 29
Dependent Claim
39 words
A method according to claim 19, in which before the step of heating whilst pressing, the applied slurry is dried by heating for a time and at a temperature sufficient to vaporize any volatile liquid components of the slurry.
Claim 30
Dependent Claim
68 words
A method according to claim 19, in which the method includes a preliminary step of ball-milling the first group of carbon particles (60) for a time sufficient to provide an average pore size therein in the range of about 9 to about 11 nm (about 90 to about 110 Angstroms) with at least about 50% of the pores having a size greater than about 2 nm (20 Angstroms).
References Cited (Backward Citations)
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