“We will need economical fuel cells. And consumers will need the technology and the education to safely use it “
A proton exchange membrane (PEM) ( animation)is a semipermeable membrane generally made from ionomers and designed to conduct protons while being impermeable to gases such as oxygen or hydrogen. This is their essential function when incorporated into a proton exchange membrane fuel cell: separation of reactants and transport of protons. PEMs can be made from either pure polymer membranes or from composite membranes where other materials are embedded in a polymer matrix. One of the most common and commercially available PEM materials is Nafion which is made by DuPont. While nafion is an ionomer with a perfluorinated backbone like Teflon, there are many other structural motifs used to make ionomers for proton exchange membranes. Many use polyaromatic polymers while others use partially fluorinated polymers.
Proton exchange membranes are primarily characterized by proton conductivity (s), methanol permeability (P), and thermal stability.
In the auto-thermal reforming process, natural gas or liquid hydrocarbons, steam and oxygen are reacted in a single vessel with a combustion zone and a reforming zone. The heat from the exothermic partial oxidation reaction balances that for the endothermic steam reforming reaction. The process gas then goes to the standard shift reaction and hydrogen purification steps.
To produce power in large amounts, many of these cells are combined into a fuel cell stack. The image at right shows a fuel cell stack composed of 36 cells.