Bipolar Membrane Fabrication for Hybrid Acid/Alkaline Fuel Cell Systems

Bipolar membranes fuel cells utilizing both anion and cation conductive materials have several advantages compared to their purely acidic or alkaline counterparts. The potential advantages include improved water management through self-hydration and facile electrode kinetics. Material transport properties play an important role in determining viability of membrane and ionomer materials. In addition, the cation-anion junction itself is a critical element in determining device performance because it must be sufficiently conductive to ionic species and mechanically stable to withstand the internal pressure from water formation. A series of electrochemical devices using different bipolar membranes have been fabricated for use in direct methanol and hydrogen fuel cells. This study examines both single- and two-membrane systems containing cation-anion junctions. These fuel cells were characterized by performance metrics and electrochemical impedance spectroscopy to determine specific areas for improvement in the bipolar devices. Operation under varying humidity was studied in order to understand water management necessary for bipolar fuel cells. These results will be used in the future optimization of bipolar devices. Financial support from US Office of the Deputy Assistant Secretary of the Army for Defense Exports and Cooperation (DASA-DE&C) is gratefully acknowledged.