Proton conductivity measurements of PEM performed in EasyTest Cell

The paper presents dc measurements of proton exchange membranes (PEMs) as an integral part of a membrane electrode assembly (MEA) performed in a novel EasyTest Cell testing device. Depending on their operating temperature PEMs are divided in two groups. The commercial Nafion membranes (Alfa Aesar) as well as the self-prepared interpenetrating network of poly(acrylamidepropylsulfonic acid) and poly(acrylamide) (PAMPS-PAM), and Nafion 117 with grafted PAMPS chains (Nafion graft-PAMPS) are tested in the low temperature range (upto 80 degrees C). The PEMs from the second group (prepared in the frame of EU project AUTOBRANE, FP 6) - phosphoric acid doped polybenzimidazole (PBI/PA) and PBI, containing cross-linked poly(vinylphosphonic acid) (CR-PVPhA) - are investigated for high temperature applications (120-200 degrees C). The EasyTest Cell is a three electrode electrochemical test that offers the possibility to obtain steady state polarization curves at strict self-regulated constant hydrogen and water vapor partial pressures. The initial slope of the polarization curves, corrected by the electronic resistance of the electrodes under study is used as a criterion for the proton conductivity of the investigated PEMs. The results obtained for the commercially available Nafion are in a good agreement with the available literature data. The PAMPS grafting from Nafion 117 results in 1.5 fold higher proton conductivity compared to the non-grafted one. The proton conductivity of the PBI/PA membrane is almost independent on the relative humidity (RH) in the range of 15-40% (0.110-0.117 S cm(-1) at 180 degrees C) which makes the water management redundant, this way facilitating the fuel cell management. The proton conductivity of the PBI/CR-PVPhA membrane is in the range of 7 x 10(-3) S cm(-1) (170 degrees C, 20% RH). The EasyTest Cell working principle and single chamber design allows precise control of vital working parameters (temperature and RH) for the proton conductivity of PEM. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.