Fuel cell is a energy conversion device that converts chemical energy into electrochemical energy, and is receiving a lot of attention as a very efficient device with low greenhouse gas emission. In particulary, anion exchange membrane fuel cell(AEMFC) have been developed as a alternative to proton exchange membrane fuel cells(PEMFCs) owing to high energy efficiency and usage of non-platinum catalyst.
In this study, composite membranes were prepared for 5 species with various content of functionalized GO(GO-Im) to investigate electrochemical performance and physical/chemical properties of AEM. First, branched poly(arylene ether sulfone)(BPAES) and poly(phenylene oxide)(PPO) were synthesized, followed by the chloromethylation reaction proceeded. After mixing two synthesized polymers, GO-Im was added in various content to prepare a composite membranes.
The chemical structure of the polymers used for blending was confirmed through 1H-NMR and FT-IR, and the degree of chloromethylation of CM-BPAES and CM-PPO was confirmed to be about 4-50%. Subsequently, the successful functionalization of GO nanosheets was achieved through hydrolysis and substitution reaction using (3-chloropropyl)trimethoxysliane(CTMS) and 1-methylimidazole. XPS and FT-IR analysis proved introduction of functional group into GO nanosheets. Additionally, introduced functional groups were confirmed through FE-SEM and EDS mapping. The thermal properties of the prepared membranes were confirmed by TGA and DSC. Water uptake, swelling ratio, and ion exchange capacity(IEC) were performed to characterize membranes. Overall, when the GO-Im content increased, the ionic conductivity tended to increase, but the excessive introduction of GO-Im reduced the number of ion conducting channels due to aggregation, confirming that the ionic conductivity was low. This indicates that the introduction of an appropriate amonunt of inorganic material is essential for the electrochemical performance. The QBPAES/PPO-GO-Im-0.9wt% composite membrane had a high water uptake and suitable dimensional stability, and achieved a high ionic conductivity of 116 mS cm-1 at 90 ℃. As a result, the prepared composite membrane have an excellent potential as an AEM for AEMFC.