Proton conductivity performance and its correlation with physio-chemical properties of proton exchange membrane (PEM)

Graphene oxide (GO) filler containing diversified Nafion-based proton exchange membrane (PEM) is studied to know the unique physical and chemical properties and performances of PEM. Nafion-SPEEK 1%-GO 0.75% (NSG-0.75%) composite shows the highest proton conductivity of 0.327 S·cm⁻¹ at 90 °C and 100% RH (relative humidity) among all the PEM investigated. The descending order of significant proton conductivity is found as; Nafion-sPGO(1%) 0.306 S·cm⁻¹ > Nafion/ZIF-8@GO 0.280 S·cm⁻¹ > Nafion/PGO (2%) 0.277 S·cm⁻¹ > Nafion/GO-sulfur (3%) 0.232 S·cm⁻¹ > Nafion/GO-poly-SPM-co-PEGMEMA(1%) 0.229 S·cm⁻¹ > Nafion/Ce-sPGO(1%) 0.215 S·cm⁻¹. The proton conductivity, water uptake capacity and ion exchange capacity, hydration number, thermal and oxidative stability, mechanical integrity (tensile strength), maximum power, and current density are found to be increased while activation energy and fuel crossover show a decrement as GO or modified GO is incorporated in the Nafion matrix. Principal component analysis (PCA) predicted a significant correlation between the proton conductivity and the properties; the water uptake capacity, ion exchange capacity, hydration number, maximum power density, and maximum current density are 0.598%, 0.688%, 0.894%, 0.980%, and 0.852% accordingly. A multiple linear model equation of proton conductivity is defined with the parameters of water uptake capacity, ion exchange capacity, hydration number, maximum power density, and maximum current density whereas the regression coefficient is 0.9923.