Sulfonated graphene oxide/sulfonated poly (2,6‐ dimethyl – 1,4‐phenylene oxide) as a potential proton exchange membrane for iron air flow battery application

Abstract

AbstractA series of proton exchange membranes (PEMs) of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) with different sulfonated graphene oxide (SGO) (0, 0.25, 0.5, 0.75, 1.0, 1.5%) were prepared for possible application in Iron‐air/flow battery. The presence of SGO in the membrane improved the water uptake of all membranes prepared and decreased the swelling ratio. The SPPO/1% w/w SGO showed good properties with higher water uptake of 44.1%, water retention of 42.48% and swelling ratio of 21.4% at 25°C. However, the 0.75% SGO exhibited the highest proton conductivity of 0.98 S/cm and better dispersion, elemental distribution, and morphology. In addition, SGO improved the thermal stability of all composite membranes. The chemical stability of all membranes remained good after 7 days in a 1 M HCL solution. The SPPO/0.75%w/w SGO showed increased proton conductivity when degradation properties were evaluated. Compared to Nafion 117, all composites showed lower iron crossover. Nafion had a high permeability of 3.03 × 10−7 cm−2/s, which is 75% higher than the 7.6 × 10−8 cm−2/s of SPPO/SGO‐1.5% and 52% higher than the 1.46 × 10−7 cm−2/s of SPPO/SGO‐0.75%. The results indicate that SGO is a good inorganic filler for the composite proton exchange membrane and stable enough for possible application in an iron‐air/flow battery.