Nafion membranes for e-fuel cell applications

Direct liquid fuel cells have been extensively studied and regarded as a promising candidate for wide commercialization among the various existing energy conversion technologies. However, their real applications still encounter many challenges mostly arising from the sluggish reaction kinetics of the liquid fuels. Recently, a novel system, powered with an electrically rechargeable liquid fuel (e-fuel), named the e-fuel cell has been presented with superior cell performance. However, studies regarding ion exchange membrane, which is an indispensable component in the liquid e-fuel cell, are still limited. Herein, a comparative study has been conducted to evaluate the performance of four Nafion series membranes. These membranes with different thicknesses have been examined and characterized at both membrane level and cell level. It is found that the thickness of membrane shows critical effects on its area resistance, as well as vanadium-ion crossover rate, which further significantly affects the e-fuel cell performance. Overall, the thinnest membrane (Nafion 211) is revealed to be preferable for the purpose of attaining a high peak power density, while the thickest membrane (Nafion 117) provides a lower self-discharge rate for the cell.