Interest in alkaline fuel cells, from both industrial applications and academic research, is growing in the recent years. However, the solid principles in guiding the design of polymer structure for anion-exchange membranes are urgently in demand, due to the limited understanding about the correlation between morphology of hydrated membrane and polymer structure. Above all, the transport mechanism of hydroxide in the membrane is not fully understood yet. By performing systematic molecular dynamics based on APPLE&P and ReaxFF force fields, five poly(p-phenylene oxide)-based polymers, at degree of functionalization 50%, were investigated. In addition to analysis of dynamic and structural properties, quantitative effects of modified functional groups on membrane and OH- transport efficiency were derived from evaluation of water channel size, defining water channels into two patterns: water-rich domain and narrow pocket of water channel, which connects two neighboring water-rich domains. The decomposed mean square displacement was calculated to explore the transport mechanism of OH- in hydrated membrane. And different diffusion patterns of OH- can be assigned based on the relative location of OH- in water domain. The importance of Grotthuss mechanism was demonstrated in facilitating the transport of OH- through the pocket of water channel, while overall contribution from vehicular mechanism is significant.

Structural correlations and transport mechanism of hydroxide in hydrated anion exchange membrane: A molecular dynamics simulation study

255th National Meeting (2018)

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