Nafion/PTFE/silicate membranes for high-temperature proton exchange membrane fuel cells

Fuel cell performance of membrane electrode assemblies (MEAs) prepared from poly (tetrafluoroethylene)/Nafion/silicate (PNS) membrane and Nafion-112 membrane were investigated. Due to the low conductivity of PTFE and silicate, PNS had a higher proton resistance than Nafion-112. However, in this work we show that PNS performs better than Nafion-112 for a high current density i > 500mA/cm(2) operation with a low inlet gas humidity. As the PEMFCs were operated at 60 degrees C with 100% RH, the results showed the maximum power density (PDmax) of PNS was: PDmax = 717 MW/cm(2) at i = 1452 mA/cm(2) with both H-2 and O-2 flow rates of 300 ml/min, and PDmax = 1042 mW/cm(2) at i = 2785 mA/cm(2) with H-2 flow rate of 360 ml/min and O-2 flow rate of 600 ml/min, which were much higher than the PDmax = 4677 mW/cm(2) at i = 1130 mA/cm(2) of Nafion-112 with both H2 and 02 flow rates of 300 ml/min. The PDmax of PNS was: 700 mW/cm(2), 656 mW/cm(2), and 577 mW/cm(2) at i = 1400 mA/cm(2) as the operating temperature and inlet gas humidity were set at 90 degrees C with 67.7% RH, 100 degrees C with 46.8% RH, and 110 degrees C with 33.1% RH, respectively However, no output power was detected for Nafion-112 MEA when the cell was operated at a temperature higher than 90 0 C and an inlet gas humidity lower than 67.7% RH. The high PEMFC performance of PNS at high current density and low humidity is attributed to the presence of silicate in the PNS membrane, which enhances water uptake and reduces electro-osmosis water loss at a high current density.(c) 2008 Published by Elsevier Ltd. on behalf of International Association for Hydrogen Energy.