Influence of metal nanoparticles in proton conductivity and water absorption of polymeric membranes for fuel cells

• We synthesized ionic membranes from styrene and acrylic acid.
• We synthesized gold and silver nanoparticles.
• Membranes were doped with nanoparticles.
• Water uptake and charge transfer resistance enhanced for doped membranes.
• Proton conductivity reduced for doped membranes.

Polymeric membrane fuel cells (PEMFC) are a reality nowadays in several mobile applications, although, their massive use is still not achieved due to the high cost of some components. Alternative membranes of sulfonated poly(styrene-co-acrylic acid) copolymers were prepared, as well as gold and silver nanoparticles through reduction of their salts. The water absorption and proton conductivity of the membrane were evaluated after addition of such metal nanoparticles into the copolymer. Water absorption increased independent of the quantity or nature of the nanometal, compared with a non-doped membrane. Proton conductivity, however, measured through electrochemical impedance spectroscopy (EIS), showed a reduction in values after addition of the nanoparticles, independent of their nature and concentration in the copolymer. On the other hand, a charge transfer resistance, related to the resistance to transfer electrons at the membrane/electrode interface, was enhanced for the nanoparticle doped membranes.