Membrane electrode assembly (MEA)

The MEA is the key component in a Proton exchange membrane fuel cell where hydrogen and air react electrochemically to generate electrical power. It is a five layer structure containing at the centre the proton exchange membrane electrolyte which separates the electrode structures to prevent reactant gas mixing and the formation of an electrical short. Each electrode consists of a gas diffusion substrate with the platinum based (Pt) electrocatalyst layers located between the membrane and the substrate. The electrocatalyst can be deposited in the case of a PEMFC either on the gas diffusion substrate or on the proton conducting membrane electrolyte using techniques such as screen printing, flexographic printing, gravure printing, spraying or rolling and calendering. Electrocatalyst layers are typically from 5 to 20 μm thick with the complete MEA being around 400 to 500 μm thick. The MEA layers are normally bonded together by hot pressing catalysed substrates to the membrane or, in the case of catalysed membranes, by compressing the gas diffusion substrate to the membrane during stack assembly.