A simple and cost-effective gel-casting technique has been developed to fabricate phosphotungstic acid (HPW) supported on mesoporous silica (MCM-41) electrolyte membrane (HPW/MCM-41) for direct methanol fuel cells (DMFCs). The effect of HPW loading on the stability of MCM-41 structure has been analyzed by small-angle X-ray scattering (SAXS), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG) techniques. In particular, the effect of solid state loading and HPW loading on the microstructure, water gain ratio, swelling ratio and conductivity of the HPW/MCM-41 membranes have been studied in detail. The results showed that a large proportion of loaded HPW is anchored in the mesoporous silica matrix, forming an effective proton conduction pathway. The results also showed that the composite membrane can operate successfully at temperatures below 200 degrees C for a long duration, based on the TGA curve of organic network formed during the gelation stage. The single cell assembled from HPW/MCM-41 membrane with 65 wt.% HPW loading gives a peak power of 101 mW cm(-2) in methanol/air at 150 degrees C without any humidification. (C) 2012 Elsevier B.V. All rights reserved.