A fuel cell system optimizing the ratio of width of a channel to a width
of a rib forming a passage for supplying fuel and air, the ratio of width
thereof to a height of a channel, and the number of passages, thereby
improving the fuel diffusing performance and reducing a pressure drop
therein is provided. The fuel cell system includes at least one stack for
generating electrical energy by an electrochemical reaction between
hydrogen and oxygen, a fuel supply portion for supplying fuel to the
stack, and an oxygen supply portion for supplying oxygen to the stack.
The stack is formed into a stacked configuration having a plurality of
membrane electrode assemblies separated by separators. The separators
have ribs which closely contact the adjacent membrane electrode
assemblies and form channels through which the oxygen and hydrogen flow.
The ratio of the width of a channel to the height of the same is between
about 0.6 and about 0.8.