The gas diffusion layers 222 and 224 serve to uniformly distribute hydrogen and oxygen, which are reaction gases, and to transfer the generated electric energy. To this end, the gas diffusion layers 222 and 224 may be disposed on respective sides of the membrane electrode assembly 210. That is, the first gas diffusion layer 222 may be disposed on the left side of the fuel electrode 214, and the second gas diffusion layer 224 may be disposed on the right side of the air electrode 216.

The first gas diffusion layer 222 may serve to diffuse and uniformly distribute hydrogen supplied as a reactant gas through the first separator 242, and may be electrically conductive. The second gas diffusion layer 224 may serve to diffuse and uniformly distribute air supplied as a reactant gas through the second separator 244, and may be electrically conductive.

Each of the first and second gas diffusion layers 222 and 224 may be a microporous layer in which fine carbon fibers are combined. However, the embodiment is not limited to any specific configuration of the first and second gas diffusion layers 222 and 224.