Functionalized Graphene Nanofiber-Incorporated Fumion Anion-Exchange Membranes with Enhanced Alkaline Stability and Fuel-Cell Performances

Anion-exchange membranes (AEMs) with high hydroxide conductivity, strong alkaline stability, and outstanding single-cell performance are in great demand for use in fuel cells and water electrolyzer applications. In this study, carboxylic acid-functionalized graphene nanofibers (c-GNF) were used as an effective filler to improve the electrochemical and physicochemical characteristics of the commercial FAA3 for anion-exchange membrane fuel-cell (AEMFC) application. The effects of c-GNF incorporation on the structural, morphological, and electrochemical performances of the composite membrane were systematically investigated. Introducing c-GNF into the FAA3 matrix increased the electrochemical performance and physicochemical stability of FAA3 membranes. Notably, the nanocomposite membrane containing 1.70 wt % of c-GNF reached a maximum hydroxide conductivity of 58.8 mS cm^-1 at 90 °C, whereas the pristine FAA3 presented only 28.7 mS cm^-1. In addition, the maximum peak power density (PPD) of 115.9 mW cm^-2 was observed for the FAGNF at 1.70 wt % in a H₂/O₂ AEMFC at 60 °C. Moreover, the alkaline stability test demonstrated that c-GNF inclusion had a significant influence on membrane chemical stability by retaining the conductivity up to 71% after 500 h of immersion in 5 M NaOH at 60 °C. Overall, this study demonstrates the enhancement of properties of a commercial membrane for AEMFC application.