Fundamentals of Gas Diffusion Layers in PEM Fuel Cells
The main components of a proton exchange membrane (PEM) fuel cell are the gas diffusion layer, membrane and catalyst. Gas diffusion layers (GDLs) are commercially available in various forms such as carbon paper or woven carbon fabrics. These are placed on either side of the membrane in a fuel cell. A GDL should allow the flow of reactant gases H2, air/oxygen and product gases to pass through it. The water formed in a cell should not choke the pores of this paper or fabric and so they are pre-coated with polytetrafluoroethylene (PTFE), which changes the GDL material from hydrophilic to hydrophobic. PTFE is also commonly called Teflon. The platinum catalysts for both the anode and cathode side can be coated on the surface of a GDL. The hydrogen or oxygen reacts in three phases: interface-gas phase (hydrogen or oxygen), liquid phase (water) and solid phase (catalyst). The carbon paper or fabric serves as a structural support for the electrocatalyst layer as well as current collector. Some of the GDLs available on the market are not coated with PTFE and are thinner in size. In such cases, the user has to coat the GDL with PTFE.
KeywordsFuel Cell Cell Performance Catalyst Layer Proton Exchange Membrane Fuel Cell Membrane Electrode Assembly
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