Patent ID: 8703355

Claim:
A membrane electrode assembly (MEA) for a fuel cell comprising: a proton exchange membrane; and a gradient catalyst structure comprising a plurality of catalyst nanoparticles disposed on layered buckypaper, wherein, along a direction perpendicular to the surface of the layered buckypaper, the gradient catalyst structure exhibits one selected from the group consisting of: a non-uniform pore size distribution, a non-uniform porosity, a non-uniform catalyst nanoparticle distribution, and combinations thereof, wherein the layered buckypaper comprises at least a first layer and a second layer, wherein the first layer has a lower porosity than the second layer, and wherein a first weight percentage of the plurality of catalyst nanoparticles is disposed on the first layer and a second weight percentage of the plurality of catalyst nanoparticles is disposed on the second layer, wherein the first weight percentage is at least 5 wt-% more than the second weight percentage, wherein the first layer comprises a mixture of: (i) at least one of single-walled carbon nanotubes, small diameter multi-wall nanotubes, or both; and (ii) carbon nanofibers and large diameter multi-wall nanotubes; and wherein the second layer comprises carbon nanofibers and large diameter multi-wall nanotubes, wherein the small diameter multi-wall nanotubes have a diameter of less than 10 nm, and wherein the large diameter multi-wall nanotubes have a diameter of greater than 10 nm.