Novel sulfonated poly (ether ether ketone)/silica coated carbon nanotubes high-performance composite membranes for direct methanol fuel cell

The major risk of using carbon nanotubes (CNTs) to modify proton exchange membranes (PEMs) in fuel cells is possible short-circuiting due to the excellent electrical conductivity of CNTs. In this article, silica-coated CNTs (SiO2@CNTs) were successfully prepared by a simple sol–gel process and then used as a new additive in the preparation of sulfonated poly (ether ether ketone) (SPEEK)-based composite membranes. The insulated and hydrophilic silica coated on the surface of CNTs not only eliminated the risk of short-circuiting, but also enhanced the interfacial interaction between CNTs and SPEEK, and hence promoted the homogeneous dispersion of CNTs in the SPEEK matrix. Moreover, compared to the methanol permeability of the pure SPEEK membrane (3.42 × 10−7 cm2 s−1), the SPEEK/SiO2@CNT composite membrane with a SiO2@CNT loading of 5 wt% exhibits almost one order of magnitude decrease of methanol crossover, while the proton conductivity still remained above 10−2 S cm−1 at room temperature. The obtained results expose the possibility of SPEEK/SiO2@CNT membranes to be served as high-performance PEMs in direct methanol fuel cells. Copyright © 2015 John Wiley & Sons, Ltd.