Nafion®/SiO2/m-BOT composite membranes for improved direct methanol fuel cell performance

Abstract

Bentonite (BOT) has excellent hygroscopicity and large specific surface, so it is chosen as a dopant of Nafion® membranes in this paper. By using the sol–gel method, bentonite has been modified by dodecylamine and fixed to the Nafion 212 membrane to prepare a Nafion/SiO₂/m-BOT composite membrane. The results of SEM and FT-IR shows that m-BOT is successfully synthesized and bound well with the Nafion 212 membrane. The limiting current density of cathode methanol oxidation indicates that the methanol permeability of the composite membrane is 20.40% lower than that of the Nafion 212 membrane. Although the conductivity of the composite membrane (6.67 × 10⁻² S cm⁻¹) declines slightly compared with that of Nafion 212 (9.91 × 10⁻² S cm⁻¹), the performance of the cell using the composite membrane (135.17 mW cm⁻²) is better than the Nafion 212 membrane (118.7 mW cm⁻²) at 55 °C. Besides, as the anode methanol concentration increases, higher performance is obtained, which indicates that the composite membrane is more suitable for cells running with a high concentration of methanol.