Based on Nafion (R)/phosphosilicate (NPS) glass and sulfonated poly(ether ether ketone) (SPEEK) polymer, proton-conducting NPS/SPEEK composite membranes are prepared by a simple mechanical ball-milling approach. The chemical structure, morphology, pore structure, and proton conductivity of the NPS/SPEEK composite membranes are investigated. Due to the incorporation of the SPEEK polymer, the obtained composite membranes exhibit sufficient flexibility and remarkably reduced pore volume compared to fragile and highly porous NPS glass. On the other hand, the NPS/SPEEK composite membranes exhibit improved proton conductivities compared with pure SPEEK. Specifically, the composite membranes display quite high proton conductivities of above 10(-3) S cm(-1) in the temperature range from 30 to 80 C at 90% relative humidity, while pure SPEEK shows moderate proton conductivities of 10(-3)-10(-4) S cm(-1) under the same conditions. For a single H(2)/O(2) fuel cell equipped with the NPS/SPEEK composite membrane, a peak power density of 322 inW cm(-2) is obtained at 65 degrees C. (C) 2011 Elsevier B.V. All rights reserved.