A novel composite membrane consisting glass microfiber (GMF) and polytetrafluoroethylene (PTFE) nanoporous film is applied to phosphoric acid fuel cell (PAFC) for performance enhancement and reducing electrolyte leakage. With 93% high porosity, the GMF can fully load phosphoric acid to maintain high proton conductivity. However, the large opening of the GMF membrane cannot effectively prevent the leakage of phosphoric acid. Therefore, in this study, a 25 gm thick PTFE thin film with pore size 50 -400 nm is employed to cover the surface of GMF for preventing phosphoric acid leakage. This composite proton exchange membrane possesses both thermal and chemical stability at the working temperature of phosphoric acid fuel cell, while providing high proton conductivity. The proton conductivity of the composite membrane (0.71 S/cm at 150 degrees C) is much higher than those of reported phosphoric acid porous membranes (similar to 10(-25)/cm at 150 degrees C). The fuel cell using the composite membrane with Pt/C catalyst exhibits excellent performance with peak power density of 614 mW/cm(2) and current density of 1761 mA/cm(2) at 140 degrees C under pure H-2 and O-2 supply, while proton conductivity is maintained 2.6 times higher than that of the pure GMF membrane due to the less phosphoric acid leakage by using PTFE film. (C) 2018 Published by Elsevier Ltd.