A poly(R1R2R3)-N+/H3PO4 composite membrane has been developed for use in a polymer electrolyte fuel cell (PEMFC). The quaternized polysulfone (QNPSU) membrane doped with H3PO4 showed high proton conductivity (0.12 S cm(-1)) at 160 degrees C and gave good performance in a single fuel cell tests. The peak power density with the QNPSU/H-3 PO4 composite membrane (at 150 degrees C, with dry H-2/O-2) was greater than 0.7 W cm(-2). The effect of the phosphoric acid doping level on fuel cell performances with the QNPSU membrane was investigated. The data show that the QNPSU/H3PO4 composite membrane is promising for higher temperature PEMFC applications. The study demonstrated that the poly(R1R2R3)-N+/H3PO4 composite system produced an effective method to connect phosphoric acid to a non-conducting polymer structure, to produce a promising membrane for phosphoric acid polymer electrolyte membrane fuel cells. (C) 2009 Elsevier B.V. All rights reserved.