PEM/AEM Junction Design for Bipolar Membrane Fuel Cells

Abstract

The combination of proton exchange membrane (PEM) and anion exchange membrane (AEM) materials to form a bipolar membrane (BPM) is of interest in hybrid electrochemical devices to mitigate the disadvantages of their monopolar counterparts. The PEM-AEM interface is a critical component in bipolar membrane fuel cell operation. In this study, mono- and di-membrane bipolar membranes were fabricated. Interfacial materials with varying conductivities were used in order to control the location of the junction within the di-membrane BPMs. Mono-membrane BPMs were constructed via conversion of a single face of a monopolar membrane (Nafion). The membranes were used in fully functional fuel cells and characterized via electrochemical impedance spectroscopy (EIS). For the di-membrane BPMs, use of a conductive interface consisting of a single ion conductive material resulted in devices with lower interfacial resistance as compared to a neutral interface. When comparing conductive interface materials, anion-conductive materials provided lower total membrane resistance than proton-conductive materials. This decrease is due to positioning the junction closer to the anode and farther from the air-cathode. These results show that the formation of the optimal junction is critically dependent on fabrication technique and location.