MEMBRANE ELECTRODE ASSEMBLY HAVING CATALYST DIFFUSION BARRIER LAYER
A membrane electrode assembly includes an anode; a cathode; a membrane between the anode and the cathode and having a thickness defined between the anode and the cathode; and a catalyst diffusion barrier layer in a location bounded on one side by an interface between the membrane and the cathode, and bounded on the other side by a plane approximately 50% of the thickness of the membrane from the cathode. A method of manufacture is also provided.
1 . A membrane electrode assembly, comprising:
an anode;
a cathode;
a membrane between the anode and the cathode and having a thickness defined between the anode and the cathode; and
a catalyst diffusion barrier layer in a location bounded on one side by an interface between the membrane and the cathode, and bounded on the other side by a plane approximately 50% of the thickness of the membrane from the cathode.
2 . The assembly of claim 1 , wherein the barrier layer comprises a web structure impregnated with ionomer.
3 . The assembly of claim 1 , wherein the cathode contains a platinum catalyst, and wherein the barrier layer inhibits migration of soluble platinum from the cathode past the barrier layer.
4 . The assembly of claim 3 , wherein the barrier layer comprises an ePTFE layer.
5 . The assembly of claim 1 , wherein the barrier layer is a separate layer between the membrane and the cathode 16 , and wherein the barrier layer has a thickness of between about 1 micron and about 15 microns.
6 . The assembly of claim 1 , wherein the barrier layer is positioned within the membrane 12 , and wherein the barrier layer has a thickness which is between about 25% and about 33% of the total membrane thickness.
7 . A method for mitigating decay of a membrane electrode assembly, comprising operating a membrane electrode assembly having an anode, a cathode, a membrane between the anode and the cathode, and a catalyst diffusion barrier layer in a location bounded on one side by an interface between the membrane and the cathode, and bounded on the other side by a plane approximately 50% of the thickness of the membrane from the cathode so that the catalyst diffusion barrier layer is between the cathode and a plane of potential change between the anode and the cathode.
8 . The method of claim 7 , wherein the barrier layer comprises a web structure impregnated with ionomer.
9 . The method of claim 7 , wherein the cathode contains a platinum catalyst, and wherein the barrier layer inhibits migration of soluble platinum from the cathode past the barrier layer.
10 . The method of claim 9 , wherein the barrier layer comprises an ePTFE layer.
11 . A method for manufacturing a membrane having a desired total thickness, and containing a layer at a desired location within the desired total thickness, comprising the steps of:
providing a first membrane component having a first thickness less than the desired total thickness and containing the layer;
providing a second membrane component having a second thickness less than the desired total thickness; and
laminating the first membrane to the second membrane.
12 . The method of claim 11 , wherein the layer comprises a catalyst diffusion barrier layer.
13 . The method of claim 11 , wherein the first membrane has a layer on one side.
14 . The method of claim 11 , wherein the second membrane is provided by casting a membrane having the second thickness.
15 . The method of claim 11 , where electrodes are pre-attached to one or both of the membrane components.