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 °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 °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 °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 × 10−3 S cm−1 (170 °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.