The increasing global focus on alternative energy sources has led to a renewed interest in fuel cells, especially hydrogen and methanol powered fuel cells. Recent research has shown layer-by-layer (LBL) assembly to be a robust technique for the fabrication of solid state electrolytes. Previous LBL electrolyte systems have lacked the high ionic conductivity values which reduce performance losses and are critical for practical applications. We have recently reported the highest ionic conductivity values ever obtained from an LBL system.^[1] By sulfonating an aromatic polyether to a high degree and pairing it with an amine-based polycation, we can obtain LBL films with ionic conductivity values up to 3.5 x 10^-2 S/cm at 25°C and 98% RH. These multilayer systems also exhibit low liquid methanol permeability and have high chemical and mechanical stability; this provides a direct application as proton-exchange membranes in direct methanol fuel cells (DMFCs). We have demonstrated that simply coating traditional fuel cell membranes with 3 to 5 bilayers of these LBL films improves the power output of DMFCs by up to 50%.

[1] Argun, A. A.; Ashcraft, J. N.; Hammond, P. T., Highly Conductive, Methanol Resistant Polyelectrolyte Multilayers. Advanced Materials 2008, 20, (8), 1539-1543.