Patent ID: 6803143
Filing Date: 2004-10-12
Classification: H01M,Y02E,Y02P

Abstract:
A gas diffusion structure for polymer electrolyte fuel cells comprising a hydrophobic, sheet-like carbon substrate and having two main opposing surfaces and a contact layer on one of these surfaces, said contact layer comprising an intimate mixture of at least one hydrophobic polymer selected from the group consisting of polyethylene, polypropylene and polytetrafluoroethylene and finely divided carbon particles, wherein the weight percentage of the carbon particles relative to the total weight of the contact layer amounts to 40 to 90 wt. %, wherein said carbon substrate is made hydrophobic by at least one hydrophobic polymer and the hydrophobic polymer is restricted to two layers extending from said two main opposing surfaces of said carbon substrate into said carbon substrate down to a depth of from 5 to 40 &mgr;m, said carbon substrate having a measureable pore volume, and the hydrophobic polymer filling from 20 to 60% of the pore volume within said two layers.