Anion exchange membranes (AEMs), used as the solid electrolyte, play an important role in the alkaline fuel cell (AFC) performance. Long-life operation and high conductivity are two requirements of a good AEM. We previously proved that modification of the imidazolium cation by attaching 2,4,6-trimethoxyphenyl groups provide an efficient way to improve the cation stability.1 Our current work focuses on a bulky tris(2,4,6-trimethoxyphenyl) phosphonium, whose structure is shown in Figure 1. Besides contribution for the duration enhancement, we are more interested in the bulky cation’s influence on the transportation behavior. Ion transport in the AEM derives from a combination of several membrane properties. The transportation directly relates to the local morphology that whether there are unimpeded channels for anions pass through.2 Water molecules located in the membrane facilitates anionic groups transfer by providing sufficient anion hopping sites.3 In our study, the water transportation is measured by using of pulsed field gradient NMR, and the anion transport property is quantified by the conductivity measurements. Insight on the anionic groups movement based on the number of water molecules per cation is investigated. A new understanding of the interplay of transport and morphology is being developed. Since ambient carbon dioxide will react with the OH- to form a mixture of CO32- and HCO3- in the film, conductivity OH- form is studied using an airtight BekkTech conductivity cell. All the other measurements are performed with Br- anions, as synthesized. Reference 1 Liu Y.;Wang J.H.; Yang Y. et al. J. Phys. Chem. C. 2014, 118, 15136-15145. 2 Hou J.B.; Li J.; Mountz D. et al. J. Membrane Sci. 2013, 448, 292-299. 3 Agmon N. Chem. Phys. Lett. 1995, 244, 456-462.

Morphology and transport in a tris(2,4,6-trimethoxyphenyl) phosphonium functionalized PPO for alkaline fuel cells

249th National Meeting (2015)

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