Nafion (R) 211 differs from previous versions of Nafion in that the membrane is cast from a dispersion rather than being melt-extruded. As such, the water sorption properties are different, as is the rate of increase in water content with temperature. Kinetic and mass-transport parameters for dispersion-cast Nafion (R) 211 were determined using solid-state electrochemistry in the temperature range 30-70 degrees C, 100% relative humidity, and 30 psi oxygen pressure. Exchange current densities, Tafel slopes, and transfer coefficients for ORR in Nafion (R) 211, are similar to those observed in Nafion (R) 117; mass-transport parameters are not. At 30 degrees C and 100% RH oxygen solubility and the diffusion coefficient is determined to be 1.16 x 10(-5) mol cm(-3) and 1.13 x 10(-6) cm(2) s(-1), respectively. Oxygen permeability at 30 degrees C (1.28 x 10(-11) mol cm(-1) s(-1)) is lower than in Nafion (R) 117 (5.31 x 10(-11) mol cm(-1) s(-1)) by factor of 4, while at T > 60 degrees C the permeability of Nafion (R) 211 increases significantly to values higher than Nafion (R) 117, and is correlated with the increase in water content and hydration number (lambda) with temperature. (C) 2010 Elsevier B.V. All rights reserved.