Planar fuel cell

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A planar fuel cell is created by sandwiching a membrane electrode assembly between two current collector assemblies.
The membrane electrode assembly (MEA) is a single sheet of a polymer electrolyte membrane with an array of anodes on one side and an array of corresponding cathodes on the other side.
The current collectors may be supported by a plastic frame, and they have an interconnect tab that provides an electrical pathway beyond the perimeter of the MEA.
The interconnect tab is situated to provide electron transfer between the anodes and the cathodes such that the interconnect tab does not traverse the thickness of the polymer electrolyte membrane.
When the planar fuel cell is assembled, the interconnect tab is sealed to prevent leaking of fuel or oxidant gases.
Fuel is distributed to only one side of the membrane electrode assembly and oxidant is distributed only to the other side.
In our preferred embodiment, the solid electrolyte is a polymer electrolyte membrane (PEM).
Some typical materials for the PEM are perfluorinated sulfonic acids derived from fluorinated styrenes, perfluorinated sulfonic acid derived from fluorinated ethylenes, and polybenzimidazole.
PEMs are ionic polymers having very high ion conductivity.
The polymeric nature of PEMs makes them much easier to handle than liquid electrolytes, and the physical construction of the electrochemical cell is greatly simplified since elaborate seals and containment systems are not needed to contain corrosive liquid electrolytes.
PEMs have the following properties: (1) high ionic conductivity, (2) zero electronic conductivity, (3) very low permeability to gases, (4) chemical stability at operating temperature, (5) mechanical strength, (6) low sensitivity to humidity, and (7) compatibility with catalyst.
Fuel cells employing PEMs are described and known in the literature (see, for example, U.
S.
Pat.
No.
5,403,675), and since one of ordinary skill in the art is assumed to be familiar with PEM cells, they will not be further elaborated upon here