| dc.description.abstract | There are few drawbacks in fuel cell proton exchange membranes that need implementation. They include: (1) dehydration of water at high-temperature leads to poor conductivity, (2) severe fuel permeability and cross-over suppresses power output; (3) weak membrane strength and insufficient chemical stability for long term operation. Improving upon all these deficiencies is a challenging task in fuel cell membrane development.
Proton exchange membrane bears hydrophilic channel saturated with ion conducting medium, water. Ion transport is therefore heavily contingent upon the microstructure of this morphological texture. However, relationships between these structural features with ion conductivity have rarely been discussed. Even fewer are the studies of improvement on ion conductivity by means of tailoring channel morphology.
Present research uses external electric field poling to create preferentially ordered channel morphology with high structural integral hydrophobic region in the membrane, has shown to effectively improved all prior-mentioned deficiencies. Validity of this approach is demonstrated in the miscible sPEEK/PES composite processed under electric field. The study has demonstrated that electric poling treatment created membrane bearing preferentially ordered hydrophilic channel morphology and densely packed hydrophobic region. Due to more densely packed amorphous hydrophobic domain, the membrane showed lower degree of swelling in water and methanol, and improved mechanical strength and chemical stability. The composite membrane of 3PES/E shows the proton conductivity up to 7.43x10-2 S/cm. Also at the high temperature and low humidity (80℃, 20%RH) environment can still maintain 9.69x10-4 S/cm. Nearly 60% increase of DMFC power output is observed using this membrane, and the best power density is recorded at 170 mA/cm2 (80℃, 1M Methanol).
These results made it clear that although high degree of sulfonation is essential to ion conductivity, it is actually more efficient to elevate ion conductivity through architected hydrophilic channel morphology that makes full utilization of the sulfonate groups and established more direct ion transport path. This approach effectively propelled ion conduction using materials bearing lower degree of sulfonation and resolved the long standing dilemma of fuel cell membrane development. The technique is also beneficial to the development of next generation high performance membrane developments encounter in many renewable energy technologies. | en_US |