Faculty of Engineering and Natural Sciences
Polyelectrolyte Multilayers for Fuel Cells and Beyond
Avni A. Argun and Paula T. Hammond
Department of Chemical Engineering, Massachusetts Institute of Technology,
The increasing focus on clean and sustainable energy sources has led to an interest in electrochemical energy devices such as batteries, fuel cells, and dye-sensitized solar cells. At the core of these devices is an electrolyte which facilitates charge transport between electrodes. Layer-by-layer (LBL) assembly is a simple and elegant method of constructing highly tailored polymer and organic-inorganic composite thin films from environmentally benign aqueous solutions. We have utilized this method to develop proton-exchange membranes for fuel cells. Previous LBL assembled electrolyte systems have lacked the high ionic conductivity values which reduce performance losses. 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 7.0 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).2 We have demonstrated that simply coating traditional fuel cell membranes with few layers of these LBL films improves the power output of DMFCs by over 53%. We are currently investigating to adapt these novel polyelectrolytes for dye-sensitized solar cells, redox flow cells, and catalytic water splitting.
(1) Argun, A. A.; Ashcraft, J. N.; Hammond, P. T., “Highly Conductive, Methanol Resistant Polyelectrolyte Multilayers.” Advanced Materials 2008, 20(8), 1539-1543.
(2) “In Search of Forever” The Economist, 6/14/2008, pp 97. (html)
October 22, 2008, 13:40-14:30, FENS G032