Silane cross-linked proton electrolyte membranes based on branched sulphonated poly(ether ether ketone)s with high sulphonation degree for direct methanol fuel cells

In this study, the silane cross-linked membranes based on branched sulphonated poly(ether ether ketone)s (BSPEEK) with a high sulphonation degree of 1.2 have been successfully prepared for direct methanol fuel cells. 3-Mercaptopropyltrimethoxysilane (MPTMS) was grafted onto the BSPEEK backbone via the thiol–ene click reaction between propenyl and thiol groups. The expected silane cross-linked structure within the membrane was confirmed by Fourier transform infrared spectroscopy and solubility test. The silane cross-linked membranes displayed excellent chemical stability and improved mechanical property. Furthermore, the water uptake and methanol permeability of the membranes decreased with the increasing proportion of MPTMS. The dense membrane structure formed by Si–O–Si cross-linking made a great contribution to the improvement of the membrane’s properties. Therefore, the as-prepared membranes may be potential proton electrolyte membrane for fuel cells.