Sulfonated graphene oxide/Nafion composite membranes for high temperature and low humidity proton exchange membrane fuel cells

Iron oxide (Fe₃O₄) nanoparticles anchored over sulfonated graphene oxide (SGO) and Nafion/Fe₃O₄-SGO composites were fabricated and applied as potential proton exchange membranes in proton exchange membrane fuel cells (PEMFCs) operated at high temperature and low humidity. Fe₃O₄ nanoparticles bridge SGO and Nafion through electrostatic interaction/hydrogen bonding and increased the intrinsic thermal and mechanical stabilities of Nafion/Fe₃O₄-SGO composite membranes. Nafion/Fe₃O₄-SGO composite membranes increased the compactness of ionic domains and enhanced the water absorption and proton conductivity while restricting hydrogen permeability across the membranes. The proton conductivity of Nafion/Fe₃O₄-SGO (3 wt%) composite membrane at 120 °C under 20% relative humidity (RH) was 11.62 mS cm^-1, which is 4.74 fold higher than that of a pristine recast Nafion membrane. PEMFC containing the Nafion/Fe₃O₄-SGO composite membrane delivered a peak power density of 258.82 mW cm^-2 at a load current density of 640.73 mA cm^-2 while operating at 120 °C under 25% RH and ambient pressure. In contrast, under identical operating conditions, a peak power density of only 144.89 mW cm^-2 was achieved with the pristine recast Nafion membrane at a load current density of 431.36 mA cm^-2. Thus, Nafion/Fe₃O₄-SGO composite membranes can be used to address various critical problems associated with commercial Nafion membranes in PEMFC applications.