Thermal crosslinked and nanodiamond reinforced SPEEK composite membrane for PEMFC

SPEEK has been widely considered as a promising alternative to Nafion(R) membrane for PEMFC. However, a conflict between high degree of sulfonation (DS) and poor mechanical strength needs to be resolved prior to wide application. In this work, such an effort was made by double strategies: thermal crosslinking and adding nanodiamond into high DS SPEEK matrix. The obtained sample was characterized by XRD, high resolution TGA and dynamic mechanical analysis (DMA). Small part of -SO3H groups within SPEEK matrix participated in the crosslinking process by forming -SO2- bridge bond, while the rest large part of -SO3H groups still contributed to the proton transport. Mechanical and thermal stability of SPEEK membrane were modified by crosslinking-induced three-dimensional (3D) networks and interactions of SPEEK with nanodiamond. In addition, the water uptakes of composite membranes were also slightly improved possibly due to the capillary condensation in nanodiamond particles.