Effect of Membrane Separators on the Performance of Direct Borohydride Fuel Cells

Abstract

The effect of the separator type on the performance of laboratory direct borohydride fuel cells (DBFCs) using hydrogen peroxide as the oxidant, is studied at room temperature. Five commercial ion exchange membranes from Nafion (N117, 115CS, NRE-212) and IONAC (MC-3470, MA-3475) brands are considered as separators for the DBFC. The membranes are directly compared by the observation and analysis of the corresponding DBFC's performance. Cell polarization, power density, stability, and durability tests are used for the evaluation. Energy densities and specific capacities estimated for a 2-hour cell operation at 0.6 V are up to 45 Wh kg−1 and 76 Ah kg−1, respectively, when using a Nafion NRE-212 membrane separator. A peak power density of 96 mW cm−2, at 0.6 V and 160 mA cm−2, is reported for the DBFC using Nafion N117, but these values cannot be sustained for appreciable operation times. For long term cell operation the IONAC MC-3470 membrane seems to outperform the stability of the benchmark Nafion membranes. The IONAC membranes’ lower cost is a good motivation but further optimization is required to improve their instantaneous power load.