Gas diffusion

Mixing of two gases with the use of molecular movements. Gases diffuse faster than solids and liquids. This is caused by molecular collision, which leads to slow diffusion in liquids and solids.

Gas Diffusion Layer (GDL) 

Conductive, porous, and thin carbon fabric that is semi-waterproof and thereby regulates the flow or flow per area of the gas reactants of a fuel cell.