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/cm2 operation with a low inlet gas humidity. As the PEMFCs were operated at 60∘C with 100% RH, the results showed the maximum power density (PDmax)(PDmax) of PNS was: PDmax=717mW/cm2 at i=1452mA/cm2 with both H2H2 and O2O2 flow rates of 300 ml/min, and PDmax=1042mW/cm2 at i=2785mA/cm2 with H2H2 flow rate of 360 ml/min and O2O2 flow rate of 600 ml/min, which were much higher than the PDmax=4677mW/cm2 at i=1130mA/cm2 of Nafion-112 with both H2H2 and O2O2 flow rates of 300 ml/min. The PDmaxPDmax of PNS was: 700mW/cm2, 656mW/cm2, and 577mW/cm2 at i=1400mA/cm2 as the operating temperature and inlet gas humidity were set at 90∘C with 67.7% RH, 100∘C with 46.8% RH, and 110∘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∘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.