Composite membranes from quaternized chitosan reinforced with surface-functionalized PVDF electrospun nanofibers for alkaline direct methanol fuel cells

In order to obtain a dual-functional nanofiber framework that could simultaneously serve as an ultra-strong reinforcing substrate and a fast ion transport medium, herein, silica coated poly(vinylidene fluoride) (SiO2@PVDF) electrospun nanofiber mat was firstly prepared using a universal polydopamine-assisted sol-gel method. After grafting with dense quaternary ammonium groups, quaternized SiO2@PVDF (QSiO(2)@PVDF) was yield. This mat with densely cationized surface can not only provide a reliable mechanical support for superhydrophilic quaternized chitosan (QCS), but also significantly improve the ionic conductivity of the whole system. The resulting QCS impregnated membrane exhibits satisfactory wet strength of as high as 11.9 MPa while pure QCS is hardly self-supporting. Moreover, the surface high-concentration cationic groups can establish channel-like ion transport pathways with the aid of 1D continuous nanofibers, thus obtaining high ionic conductivity of 0.041 S cm(-1) (80 degrees C), which is about 1.3 times higher than that of pure QCS. The single alkaline fuel cell using this membrane demonstrates a maximum power density of 98.7 mW cm(-2). Therefore, this relatively independent design of mechanically support fiber core and high-concentration ion conduction surface provides a new methodology for fabricating high-performance anion exchange membranes.