Plasma deposition of polymer to reduce fuel permeability and increase stability of ion-conducting polymer membrane useful in fuel cell uses highly crosslinked polymer of independent composition

摘要

In reducing the fuel permeability and increasing the thermal, chemical and long-term stability of ion-conducting polymer membranes by depositing a plasma polymerized, thin, densely crosslinked film with satisfactory ion conductivity as diffusion barrier on one or both sides of the original membrane, the composition of this film can be chosen independently of that of the membrane and hence so that it contributes little to the membrane resistance. Process for reducing the fuel permeability and increasing the thermal, chemical and long-term stability of ion-conducting polymer membranes involves depositing a plasma polymerized, thin, ion-conducting film on one or both sides of the original membrane by plasma deposition to form a densely crosslinked polymer film with satisfactory ion conductivity as diffusion barrier. Its high degree of crosslinking makes this very stable thermally and chemically and also inhibits permeation of fuel, preferably methanol and hydrogen and/or oxygen and also inhibits diffusion of other substances, e.g. reaction products such as carbon dioxide and water, through the membrane. The composition of this film can be selected independently of the composition of the membrane material to be coated and hence so that it contributes little to the membrane resistance.