PEMFC

PEM

Proton exchange fuel cell (PEFC) has been extensively investigated in past decades due to their potential to supply clean energy for transport applications.

Figure 1. Schematic illustration of fuel cell vehicle and fuel cell stack
Figure 1. Schematic illustration of fuel cell vehicle and fuel cell stack

In early years, the researches on PEFC had focused on room temperature operation, and many issues such as CO poisoning of Pt catalyst and the complexity of water management in polymer electrolyte membranes (PEMs) have been revealed. Several approaches are in progress to overcome these problems, and operating PEFC at high temperature above 120 °C under nonhumidification conditions is considered to be the most promising solution. For the high temperature PEFC, there is a growing need to find new PEM systems offering reasonable proton conductivity without water.
In our lab, we developed new PEM systems, which is the fabrication of composite PEMs by incorporating ionic liquids (ILs) to replace water molecule in the block copolymer matrices. Compared with membranes having discrete ionic domains (including Nafion 117), our membranes revealed over an order of magnitude increase in conductivity with the highest conductivity of 0.045 S/cm obtained at 165 °C by inducing the nanostructure. We investigate the relationship between the morphology and the conductivity of PEMs comprising diverse ILs highlighting the important role of the types of self-assembled structures in determining the transport efficiency.

Figure 2. The relationship between morphology and conductivity in PEM electrolytes (Kim, S. Y. et. al. Nat. Commun. 2010, 1, 88, Kim, S. Y. et. al. Macromolecules, 2011, 44 (13), 5289, Kim, O. et. al. Macromolecules, 2012, 45 (21), 8702.)
Figure 2. The relationship between morphology and conductivity in PEM electrolytes
(Kim, S. Y. et. al. Nat. Commun. 2010, 1, 88, Kim, S. Y. et. al. Macromolecules, 2011, 44 (13), 5289, Kim, O. et. al. Macromolecules, 2012, 45 (21), 8702.)

In addition, we explore the fascinating experimental insights into confinement- and interface-driven modulation of ion transport properties for polymer electrolytes and study valuable insights into the factors affecting the proton transport efficiency of IL-containing polymers. Our research would provide the future prospects for designing desired nanostructures as efficient PEFCs.

Figure 3. The factors affecting the ion transport properties (a) The effect of dissimilar internal structures on conductivity (b) Proton transference number of PEM containing various ILs.
Figure 3. The factors affecting the ion transport properties (a) The effect of dissimilar internal structures on conductivity (b) Proton transference number of PEM containing various ILs. (Kim, O. et. al. J. Phys. Chem. Lett., 2013, 4 (13), 2111, Kim, S. Y. et. al. Macromolecules, 2014, 47(3), 1099.)

Nowadays, we developed a new block copolymers tailored with phosphonic acid as a protogenic group. The direct comparison with sulfonated block copolymers was allowed to elucidate the role of the protogenic group in determining the phase behavior of acid-containing polymers. We first reported nanostructured phosphonated polymers which have the potential to be alternatives to the widely studied sulfonated polymers. Our research would provide the future prospects for designing desired nanostructures as efficient PEFCs.

Figure 4. The various nanostructures of phosphonated block copolymers containing ILs (Jung, H. Y. et. al. Macomolecules, 2015, 48(17), 6142, Jung, H. Y. et. al. Macromol. Rapid Commun., 2016)
Figure 4. The various nanostructures of phosphonated block copolymers containing ILs
(Jung, H. Y. et. al. Macomolecules, 2015, 48(17), 6142, Jung, H. Y. et. al. Macromol. Rapid Commun., 2016)