Enhancement of Proton Conduction at Low Humidity by Incorporating Imidazole Microcapsules into Polymer Electrolyte Membranes
writer：Jingtao Wang, Xiujun Yue, Zizhuo Zhang, Zheng Yang, Yifan Li, Han Zhang, Xinlin Yang, Hong Wu, and Z
keywords：Water preservation; Fuel cell; Membrane material
source：期刊
specific source：Adv. Funct. Mater., 22 (21), 4539-4546
Issue time：2012年
Design and fabrication of hierarchically structured membranes with high
proton conductivity is crucial to many energy-relevant applications including
proton exchange membrane fuel cell (PEMFC). Here, a series of imidazole
microcapsules (IMCs) with tunable imidazole group loading, shell thickness,
and lumen size are synthesized and incorporated into a sulfonated poly(ether
ether ketone) (SPEEK) matrix to prepare composite membranes. The IMCs
play two roles: i) Improving water retention properties of the membrane.
The IMCs, similar to the vacuoles in plant cells, can render membrane a
stable water environment. The lumen of the IMCs acts as a water reservoir
and the shell of IMCs can manipulate water release. ii) They form anhydrous
proton transfer pathways and low energy barrier pathways for proton hopping,
imparting an enhanced proton transfer via either a vehicle mechanism
or Grotthuss mechanism. In particular, at the relative humidity (RH) as low
as 20%, the composite membrane exhibits an ultralow proton conductivity
decline and the proton conductivity is one to two orders of magnitude higher
than that of SPEEK control membrane. The enhanced proton conductivity
affords the composite membrane an elevated peak power density from
69.5 to 104.5 mW cm ? 2 in a single cell. Moreover, the application potential
of the composite membrane for CO 2 capture is explored.