Extended catalyzed layer for minimizing cross-over oxygen and consuming peroxide
View Patent ↗A membrane electrode assembly includes an anode, a cathode, a membrane disposed between the anode and the cathode, and an extended catalyzed layer between the cathode and the membrane, the extended catalyzed layer being adapted to consume oxygen and decompose hydrogen peroxide to produce water.
1. A membrane electrode assembly, comprising:
an anode;
a cathode;
a membrane disposed between the anode and the cathode; and an extended catalyzed layer between the cathode and the membrane, the extended catalyzed layer being adapted to reduce oxygen, and decompose hydrogen peroxide and free radicals to produce water, wherein the layer is less porous than the anode and the cathode, and wherein the extended catalyzed layer contains catalyst particles and has a thickness (t) determined as follows:
t
≥
3
π
Rn
,
wherein,
t is layer thickness,
R is catalyst particle radius, and
n is catalyst particle concentration, and wherein the extended catalyzed layer has a porosity of less than 30%.
2. The assembly of claim 1 , wherein the particles are selected from the group consisting of particles of carbon, particles of platinum, particles of platinum alloy and combinations thereof.
3. The assembly of claim 2 , wherein the particles are supported on carbon.
4. The assembly of claim 2 , wherein the particles are platinum alloy selected from the group consisting of platinum cobalt, platinum nickel and combinations thereof.
5. The assembly of claim 1 , wherein the extended catalyzed layer is electrically connected to the cathode.
6. The assembly of claim 5 , wherein the extended catalyzed layer is electrically connected to the cathode through a support material.
7. The assembly of claim 6 , wherein the support material is carbon.
8. The assembly of claim 1 , wherein the extended catalyzed layer is substantially non-porous.
9. The assembly of claim 1 , wherein the extended catalyzed layer has porosity which is flooded with water.
10. The assembly of claim 1 , wherein the extended catalyzed layer has an oxygen reduction rate which is substantially the same or greater than the cathode.
11. The assembly of claim 1 , wherein the extended catalyzed layer extends from the edge of the cathode facing the membrane into the membrane the distance t.
12. The assembly of claim 1 , wherein the extended catalyzed layer comprises particles of a catalyst which is the same catalyst as is present in the cathode.
13. A membrane electrode assembly, comprising:
an anode;
a cathode;
a membrane disposed between the anode and the cathode; and an extended catalyzed layer between the cathode and the membrane, the extended catalyzed layer being adapted to reduce oxygen, and decompose hydrogen peroxide and free radicals to produce water, wherein the extended catalyzed layer comprises a catalyst layer disposed in the membrane and having an oxygen consuming potential between a low value of about 0.3V above the hydrogen potential and a high value of about 100 mV less than open circuit voltage, and wherein the layer is centered around a position X 0 determined according to the following:
X
o
=
H
H
2
·
D
H
2
·
C
H
2
o
H
H
2
·
D
H
2
·
C
H
2
o
+
2
·
H
O
2
·
D
O
2
·
C
O
2
o
wherein:
H H 2 is the Henry constant of hydrogen from gas into ionic polymer of the membrane;
D H 2 is the diffusion constant of hydrogen in the ionic polymer;
C o H 2 is concentration of hydrogen at the anode;
H O 2 is the Henry constant of oxygen from gas into ionic polymer of the membrane;
D O 2 is the diffusion constant of oxygen in the ionic polymer, and
C o o 2 is concentration of oxygen at the cathode, further comprising an additional extended catalyzed layer positioned between the anode and the membrane and adapted to reduce oxygen and decompose hydrogen peroxide to produce water, and wherein the extended catalyzed layer has a porosity of less than 30%.
14. The assembly of claim 13 , wherein the layer contains catalyst particles and has a thickness (t) determined as follows:
t
≥
3
/
π
Rn
,
wherein
t is layer thickness,
R is catalyst particle radius, and
n is catalyst particle concentration.
15. The assembly of claim 13 , wherein the catalyst layer is electrically connected to the cathode through a resistance selected to provide the catalyst layer with the oxygen consuming potential.
16. The assembly of claim 13 , wherein the additional extended catalyzed layer contains catalyst particles and has a thickness (t) determined as follows:
t
≥
3
/
π
Rn
,
wherein,
t is layer thickness,
R is catalyst particle radius, and
n is catalyst particle concentration.
17. The assembly of claim 13 , wherein the additional extended catalyzed layer contains catalyst particles, and wherein the particles are selected from the group of particles of carbon, particles of platinum, particles of platinum alloy and combinations thereof.
18. The assembly of claim 17 , wherein the particles are supported on carbon.
19. The assembly of claim 13 , wherein the extended catalyzed layer is substantially non-porous.
20. A membrane electrode assembly, comprising:
an anode;
a cathode;
a membrane disposed between the anode and the cathode; and an extended catalyzed layer between the cathode and the membrane, the extended catalyzed layer being adapted to reduce oxygen, and decompose hydrogen peroxide and free radicals to produce water, wherein the layer is less porous than the anode and the cathode, and wherein the extended catalyzed layer contains catalyst particles and has a thickness (t) determined as follows:
t
≥
3
/
π
Rn
,
wherein,
t is layer thickness,
R is catalyst particle radius, and
n is catalyst particle concentration, wherein the extended catalyzed layer is a porous electrically connected and ionically conductive structure having a porosity of between about 0% and about 30%, wherein the catalyst is present in an amount between about 5 and about 50% vol based upon volume of the layer, and ionomer is present in an amount between about 5 and about 50% vol based upon volume of the layer.
21. The assembly of claim 1 , wherein the membrane is a reinforced membrane.