Gas diffusion, transport characteristics and modelling in porous membrane systems with application for polymer electrolyte membrane fuel cells.

Fuel cells convert chemical energy in electrical energy and heat by consuming typically hydrogen and oxygen and producing water as the main by-product. This is achieved by reducing hydrogen at the anode (left hand side) and oxidising oxygen at the cathode (right hand side). The polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layer (GDL) and the catalyst layer (CL) are crucial components mainly responsible for the distribution of gases, chemical reaction, and water transport in any PEMFC. The GDL consists of two main layers which are the macroporous substrate (MPS) and microporous layer (MPL). The MPS comes before the gas flow field and provides gas diffusion through a carbon-based paper or carbon cloth and collects the current. MPL is generally used to reduce the contact resistance between the CL and GDL. The most important parameters of porous membranes are derived from Fick's first law which relates the molar flux to membrane permeability. All possible gas transport mechanisms in porous membrane have been investigated in literature such as Hagen-Pouiselle, Knudsen, surface diffusion, capillary condensation, and molecular sieving.