Composite membranes comprising functionalized Bentonite (HSO3-BEN)-sulfonated poly(ether ether ketone) (sPEEK) is fabricated as an alternative polymer electrolyte membrane (PEM) for direct methanol fuel cells (DMFCs). K+-Bentonite is functionalized through silane condensation to introduce organo sulfonic acid groups. Ion-exchange capacity, sorption and proton conductivity for the composite membranes have been investigated. These composite membranes are also characterised for their mechanical and thermal properties. DMFCs employing sPEEK-HSO3-BEN composite membrane delivered peak power density of 140 mW cm(-2), while peak power density of 71 mW cm(-2) is obtained for the DMFC employing pristine sPEEK membrane at 70 degrees C. The results show that these composite membranes exhibits lower methanol permeability in comparison to pristine sPEEK membrane. (C) 2014 Elsevier Ltd. All rights reserved.