Building the Direct Ethanol Fuel Cell: Quaternary Ammonium Salt-­Exchanged Nafion

Abstract

Today’s world is quickly growing and demanding more energy. This rise in demand leads to more need for energy other than from coal and oil. The direct ethanol fuel cell (DEFC) is a great way to bypass coal and oil because it is efficient and uses cheap fuel that is easy to produce. There are difficulties with the DEFC, however, that must be dealt with in order for the DEFC to be an effective energy source. This thesis focuses on altering the proton exchange membrane (PEM), Nafion, to block ethanol from crossing over the cell and at the same time preserving the conductivity. In recent studies Lieb has found that cetyl trimethylammonium cations are helpful in this area with fuel cell performance. In this study cations with smaller carbon chain lengths branching from the nitrogen are studied in aqueous solution and deep eutectic solvents (DESs) to determine their ability to perform cation exchange with Nafion as well as gauge the effect the size of the cation has on conductivity and ethanol crossover. The experiments include a titration to measure the extent of cation exchange with Nafion, impedance testing to measure resistance and an ethanol permeation test to measure the ethanol flux through Nafion. The DESs of tetrabutylammonium and tetrapropylammonium bromide show an advantage over their aqueous equivalents in ethanol crossover with relatively similar resistance change. The size of the ammonium cations seems to have no strikingly different abilities in ethanol crossover or resistance. That said, this thesis provides promising ammonium cation-­‐altered Nafion to function well in a fuel cell performance test.