Title: Effect of silica nanoparticles on PVA-SSA as polymer electrolyte membranes
Fluorocarbon and hydrocarbon based polymer electrolyte membranes (PEM) are studied widely for fuel cell applications. Among them, Nafion® has aquired commercial status due to its high proton conductivity under humidified conditions. However, it is expensive, environmentally not benign, and chemically degradable at the fuel cell operating temperatures. As a result, there is a need to develop membranes using polymers which are environmentally benign, chemically stable with good mechanical properties, low cost and easy processability. Poly (vinyl alcohol) is a versatile, water soluble polymer which can be used as a Polymer Electrolyte Membrane (PEM). However, it has lower proton conductivity when sulphonated using sulphosuccinic acid (SSA) in comparison to Nafion. The presence of multiple hydrophilic groups (–OH and -SO3H+) in PVA-SSA is shown to result in competitive hydration and reduction in proton conductivity. In presence nano-silica particles fewer hydroxyl groups are available for hydration, sulphonic groups have higher chances for solvation by the water molecules, resulting in an H+ion dissociation without much hindrance and eventually a higher conductivity. This work aims to study the role of silica in PVA-SSA system, to optimise the filler concentration and the proton conductivity under fully hydrated and humidified conditions. Effect of distribution of nano-silica on water uptake and ion exchange capacity (IEC) is used to understand how proton conduction in PVA-SSA is affected by the addition of nano-silica particles.