(50a) Functional Graphenes Oxide Coating with Speek Coaxial Electrospun Fibers for Proton Exchange Membranes

Proton exchange membrane fuel cell (PEMFC) is considered to be clean and efficient energy storage and conversion in the 21th century. As one of the key components of PEMFC, proton exchange membrane (PEM) with properties of cost-effectiveness, high conductivity and low fuel crossover attracts much attention. Many efforts have been done on the inorganic hybrid PEMs for the good barrier or hygroscopic abilities of inorganic fillers as GO, ZrP, SiO₂ etc. While poor compatibility between inorganic and organic components becomes the most challenging issue.

In this study, the inorganic/organic compatibility is improved by coaxial electrospinning method. Encapsulation of sulfonated organosilane functionalized graphene oxide (SSi-GOs) in the core of sulfonated poly (ether ether ketone) (SPEEK) nanofibers prevents the inorganic component from dropping off, and thus facilitates high compatibility, conductivity and single cell performance. Strong electric force induces the alignment of SSi-GOs sheets along the electrospun fiber, which is evidenced by the spindle-like morphology of the SSi-GOs containing fibers through TEM. As comparison, SSi-GOs cure up and float between the hybrid electrospun fibers due to the lack of restriction. With the increase of SSi-GO content, water absorption of the membranes increases to a maximum value at around 2.5 wt% and then decreases, while the swelling ratio keeps decreasing to as low as 10% in 70^oC water. The sulfonated organosilane functional groups on SSi-GO contribute to better ionic aggregations, as a result, the co-electrospun membranes exhibit high conductivity of around 160mS cm^-1 with 2.5 wt% SSi-GO content, 1.4 and 1.5 folds of that with 2.5wt% SSi-GO hybrid electrospun and without SSi-GO electrospun membranes, respectively. Better single cell performances, including higher power density and lower hydrogen crossover current density are achieved with the co-electrospun membranes comparing with the hybrid electrospun membranes and even Nafion membranes.