| Alkaline fuel cells (AFCs) have the potential replace proton exchange membrane fuel cells in portable power applications due to its lower cost. However, this will require robust chemically stable alkaline anion exchange membranes (AEMs) to ensure long performance lifetimes in solid-state AFCs. In this study, we utilized solid-state chemistry to synthesize Nafion-based AEMs with a variety of covalently attached cations, including trimethylammonium, trimethylphosphonium piperazinium, pyrrolidinium, pyridinium and quaternized 1,4'-diazabicyclo[2.2.2]octane (DABCO). Infrared spectroscopy confirms the partial asymmetric functionalization of all AEMs synthesized except pyridinium. The conductivity of all AEMs were similar and approximately 5 fold lower than proton conducting Nafion at 80 °C and 90% relative humidity. The effect of cation type on AEM chemical and thermal stability was investigated as a function of various conditions (e.g., hydration levels, temperature, and pH). High chemical and thermal stability was observed for all successfully synthesized AEMs with the exception of the trimethylphosphonium cation AEM. A kinetic study on the reaction between dimethylpiperazine and the Nafion precursor revealed that the optimum conditions were at room temperature for 72 h. These results show that Nafion precursor derived AEMs provide promising membranes for future low-cost long-lasting AFCs. |
