Semi-interpenetrating network based on cross-linked poly(vinyl alcohol) and poly(styrene sulfonic acid-co-maleic anhydride) as proton exchange fuel cell membranes

A series of promising proton conducting membranes have been synthesized by using poly(vinyl alcohol), with sulfosuccinic acid (SSA) as a cross-linking agent and poly(styrene sulfonic acid-co-maleic acid) (PSSA-MA) as proton source, which form a semi-interpenetrating network (semi-IPN) PVA/SSA/PSSA-MA membrane. A bridge of SSA between PVA molecules not only reinforces the network but also provides extra proton conducting paths. PSSA-MA chains trapped in the network were the major sources of protons in the membrane. FT-IR spectra confirmed the success of the cross-linking reaction and molecular interactions between PVA and PSSA-MA. Associated characteristics of a proton conducting membrane including ion-exchange capacity (IEC), proton conductivity and water uptake were investigated. The measured IECs of the membranes increased with increase of PSSA-MA content varying from 20 to 80% and correlated well with the measured uptake water and proton conductivity. The semi-IPN membranes with PSSA-MA over 60% exhibited a higher proton conductivity than Nafion-115 and also a reasonable level of water uptake. Fuel cell performance of membrane electrode assemblies (MEA) was evaluated at various temperatures with H₂/air as well as H₂/O₂ gases under ambient pressure. A power density of 0.7 W cm^-2 was obtained for the MEA using PVA/SSA20/PSSA-MA80 membrane using H₂/O₂ at 50 °C.