Abstract
Poly(tetrafluoroethylene) (PTFE) porous substrate-reinforced composite membranes for energy conversion technologies are prepared and characterized. In particular, we develop a new hydrophilic treatment method by in-situ biomimetic silicification for PTFE substrates having high porosity (60–80%) since it is difficult to impregnate ionomer into strongly hydrophobic PTFE porous substrates for the preparation of composite membranes. The thinner substrate having ~5 μm treated by the gallic acid/(3-trimethoxysilylpropyl)diethylenetriamine solution with the incubation time of 30 min shows the best hydrophilic treatment result in terms of contact angle. In addition, the composite membranes using the porous substrates show the highest proton conductivity and the lowest water uptake and swelling ratio. Membrane-electrode assemblies (MEAs) using the composite membranes (thinner and lower proton conductivity) and Nafion 212 (thicker and higher proton conductivity), which have similar areal resistance, are compared in I–V polarization curves. The I–V polarization curves of two MEAs in activation and Ohmic region are very identical. However, higher mass transport limitation is observed for Nafion 212 since the composite membrane with less thickness than Nafion 212 would result in higher back diffusion of water and mitigate cathode flooding.
Highlights
The unstable crude oil prices and global warming caused by greenhouse gases drive us to use alternative energy sources
The installation cost is still higher than conventional energy conversion technology such as internal combustion engine and the technical level of durability and reliability must be raised to a higher level to enter the full-fledged fuel cell market [8,9,10]
gallic acid (GA)/amino-terminated substances (ATS), which is caused by adhesive deposition of the mussel-inspired coating [35]
Summary
The unstable crude oil prices and global warming caused by greenhouse gases drive us to use alternative energy sources. Among the new and renewable energy, hydrogen had begun to be translated into the alternative energy source area due to easy deployment into electricity infrastructure, diversified energy sources to produce hydrogen from fossil fuels to biomass, improvement of local air pollution, and recent matured technologies such as fuel cells and electrolyzers [2,3]. There is no greenhouse gas emission when hydrogen is produced by water electrolysis using electricity supplied from renewable energy sources such as wind, solar, biomass, etc. The installation cost is still higher than conventional energy conversion technology such as internal combustion engine and the technical level of durability and reliability must be raised to a higher level to enter the full-fledged fuel cell market [8,9,10]
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