Facile synthesis of metal oxide nanofibers and construction of continuous proton-conducting pathways in SPEEK composite membranes

In this study, a facile approach was used to prepare hydrophilic TiO2 nanofibers (TiNFs) by calcining electrospun polyacrylonitrile nanofibers embedded with titanium precursors. A high-performance proton exchange membrane (PEM) was achieved by incorporating the TiNFs into a sulfonated poly(ether ether ketone) (SPEEK) matrix. The high aspect ratios of the inorganic nanofibers permitted interconnecting of ion-conducting channels, thereby significantly improving proton conductivity in the membrane. In addition, the TiNFs provided tortuous pathways for methanol transport, suppressing the methanol permeability coefficient. The maximum power density of the SPEEK/TiNFs-1.0 composite membrane was 1.4 times higher than that of the pristine SPEEK membrane at 100% relative humidity and 60 °C. Furthermore, the stable fiber skeleton improved the mechanical stability of the composite membrane. The SPEEK/TiNFs-1.0 membrane exhibited superior mechanical properties with the tensile strength of 40.4 MPa and maximum elongation at break of 76%.