A novel strategy toward the advancement of proton exchange membranes through the incorporation of propylsulfonic acid-functionalized graphene oxide in crosslinked acid-base polymer blends

Abstract

Propylsulfonic acid-functionalized graphene oxide (PrSGO) was introduced into the sulfonated poly(ether ether ketone) (SPEEK)-sulfonated poly(benzimidazole) (SPBI) blend in this study to understand the impact on glass transition temperature (Tg), structural properties, increase mechanical properties, proton conductivity, and single-cell performance. At different loadings of PrSGO, atomistic molecular dynamics (MD) simulations of SPEEK/SPBI, cross-linked SPEEK/SPBI (XSPEEK/SPBI), and XSPEEK/SPBI/PrSGO composite systems were performed. Tg was increased after cross-linking the polymer systems and increasing the loading percent of PrSGO filler and SPBI in the polymer systems. The mechanical properties, chemical and thermal stability of the XSPEEK/SPBI/PrSGO nanocomposite membranes significantly increased PrSGO loading because of the strong interfacial interaction between PrSGO and the XSPEEK/SPBI matrix. XSPEEK/SPBI/PrSGO nanocomposite membrane at 4 wt % PrSGO loading demonstrated a considerable improvement in proton conductivity up to 0.17 S/cm at 100% relative humidity (RH) at 90 °C. Furthermore, the XSPEEK/SPBI/PrSGO nanocomposite membrane at 4 wt% PrSGO loading demonstrated good fuel cell (FC) performance with a maximum power density of ∼0.82 W/cm2 at 100% RH, 80 °C. Incorporating PrSGO nanofillers in the polymer matrix considerably improved proton conductivity of the membranes, other significant properties, and overall FC performance due to their hygroscopic nature, a higher number of sulfonic acid groups, and excellent interaction of the acid functionalized fillers with the cross-linked SPEEK/SPBI-based matrix.