Diffusion media, fuel cells, and fuel cell powered systems
In at least certain embodiments, the present invention provides a diffusion media and fuel cells and systems employing the diffusion media. In at least one embodiment, the diffusion media comprises a porous matrix having an outer surface and a hydrophilic polymeric coating on at least a portion of the porous matrix with the hydrophilic coating comprising the cured product of a formulation comprising a hydrophilic monomer.
1 . A porous diffusion media comprising:
a porous matrix having an outer surface comprising a first major face and a second major face; and,
a hydrophilic polymeric coating on at least a portion of the outer surface;
the hydrophilic coating comprising the cured product of a formulation comprising a hydrophilic monomer.
2 . The porous diffusion media of claim 1 wherein the hydrophilic coating is sufficiently hydrophilic to define a contact angle of less than 90° along one of the first and second major faces of the diffusion media.
3 . The porous diffusion media of claim 1 wherein the hydrophilic coating is sufficiently hydrophilic to define a contact angle of less than 25° along one of the first and second major faces of the diffusion media.
4 . The porous diffusion media of claim 1 wherein the hydrophilic coating is sufficiently hydrophilic to define a contact angle of 0° along one of the first and second major faces of the diffusion media.
5 . The porous diffusion media of claim 1 wherein the porous matrix comprises an electrically conductive material comprising at least one of: carbon paper, graphite paper, cloth, felt, foam, carbon or graphite wovens, carbon or graphite non-wovens, metallic screens or foams, and combinations thereof.
6 . The porous diffusion media of claim 4 wherein the porous matrix defines a thickness of between 20 μm and 1000 μm and the hydrophilic coating has a thickness between 1 nm and 1 μm.
7 . The porous diffusion media of claim 2 wherein the outer surface includes an inner surface portion extending between the first and second major faces, the coating being disposed on the inner surface portion and extending between the first and second major faces.
8 . The porous diffusion media of claim 7 wherein the hydrophilic monomer comprises a glycol acrylate or glycol methacrylate.
9 . The porous diffusion media of claim 8 wherein the hydrophilic monomer comprises polyethylene glycol acrylate.
10 . The porous diffusion media of claim 7 wherein the hydrophilic monomer is UV curable.
11 . The porous diffusion media of claim 10 wherein the formulation comprises polyethylene glycol acrylate, polyethylene glycol diacrylate, photoinitiator, and solvent.
12 . The porous diffusion media of claim 1 wherein the porous diffusion media further comprises hydrophobic material.
13 . The porous diffusion media of claim 12 wherein the hydrophobic material is disposed along one of the first and second major faces of the diffusion media.
14 . The porous diffusion media of claim 1 wherein the hydrophilic coating has portions distributed across a cross section of the porous diffusion media between first and second major faces of the diffusion media.
15 . The porous diffusion media of claim 1 wherein the hydrophilic polymeric coating comprises regions of hydrophilic polymeric coating and the diffusion media comprises uncoated regions, the regions of the hydrophilic polymeric coating and the uncoated regions alternate across at least one of first and second major faces of the diffusion media.
16 . The porous diffusion media of claim 12 wherein the hydrophilic polymeric coating comprises regions of hydrophilic polymeric coating and the hydrophobic material comprises regions of hydrophobic material.
17 . The porous diffusion media of claim 16 wherein the alternating regions are characterized by a periodicity of less than 5 cm.
18 . A fuel cell comprising:
an anode;
a cathode,
a PEM disposed between the anode and the cathode; and
a diffusion media disposed between at least one of the anode and the cathode and the PEM, the diffusion media comprising:
a porous matrix having an outer surface comprising a first major face and a second major face; and
a hydrophilic polymeric coating on at least a portion of the outer surface;
the hydrophilic coating comprising the cured product of a formulation comprising a hydrophilic monomer.
19 . A method for making a diffusion media, said method comprising:
providing a porous matrix; and
coating at least a portion of the porous matrix with a hydrophilic polymeric coating.
20 . The method of claim 19 wherein the coating step comprises:
exposing the porous matrix to a hydrophilic formulation comprising a hydrophilic monomer to form a coating precursor on the porous matrix;
masking a first portion of the precursor coated porous matrix while leaving a second portion of the matrix unmasked; and
exposing the precursor coated porous matrix to UV light to UV cure the coating precursor on the second portion of the matrix to form the hydrophilic polymeric coating on the second portion.