Polymer electrolyte membranes (PEMs) consisting of copper(II)phthalocyanine tetrasulfonic acid tetra sodium salt (CuPCSA) and disulfonated poly(arylene ether sulfone) (SES0005) are prepared. The TEM analysis results prove the incorporation of CuPCSA as nanoparticles into the composite membranes. Catalytic activity of CuPCSA towards peroxide degradation is shown by CV. Addition of CuPCSA increases the dimensional stability in contact with water (18% vs. 43% linear swelling for pristine SES0005). Addition of 10 wt% CuPCSA (SES0005-IM10) increases the proton conductivity four fold to 16.8 mS cm(-1) at 120 degrees C and 50% relative humidity (rh). Activation energy decreases with CuPCSA content, reducing the conductivity's temperature dependence. Membranes were tested in low and medium temperature PEM fuel cells at 65 and 120 degrees C, respectively, at 50% rh. In the LT-PEMFC, 40 mu m thick SES0005-IM10 and Nafion 212 based MEAs exhibited current densities of 470 and 454 mA cm(-2) at 0.7 V, respectively. In the MT-PEMFC, SES0005-IM10 based MEAs demonstrated a current density of 405 mA cm(-2) at 0.5 V, 2.4 folds more than pristine membrane based MEAs. In the DMFC, SES0005-IM10 enabled a peak power density of 153 mW cm(-2) at 70 degrees C and 1 M methanol feed, 20% higher than Nafion 212, 38% higher than mPES60. (C) 2015 Elsevier B.V. All rights reserved.