Nafion membranes modified with silica and silica sulfuric acid are fabricated for the elevated temperature and lower humidity operation of proton-exchange membrane fuel cells. An incorporation of silica sulfuric acid promotes the amorphous phase which in turn influences the segmental motion of polymeric chains. By the endeavor of sulfonic acid moieties, ion channels are extended and facilitate the high ionic diffusion. With the hygroscopic effort, high water molecules retention is favored which provokes the self humidification of Nafion membrane. The electrochemical properties of the composite membranes are varied in terms of the permeation effect of different sized silica particles in to the viable channels of Nafion membrane. Though higher electrochemical properties are obtained for the Nafion-silica sulfuric acid composite membranes, a balance between the electrochemical and physical properties is also highly maintained as that of bare Nafion membrane. The inclusion of silica sulfuric acid provides more sulfonic acid functional groups for the conscription of electrochemical properties and ceramic property of the material strengthens the perfluorinated polymer back bone which collectively extends the fuel cell performance of composite Nafion membranes and influences its potential application. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.