Bipolar polymer electrolyte interfaces for hydrogen–oxygen and direct borohydride fuel cells

Direct borohydride fuel cells (DBFCs) using liquid hydrogen peroxide as the oxidant are safe and attractive low temperature power sources for unmanned underwater vehicles (UUVs) as they have excellent energy and power density and do not feature compressed gases or a flammable fuel stream. One challenge to this system is the disparate pH environment between the anolyte fuel and catholyte oxidant streams. Herein, a bipolar interface membrane electrode assembly (BIMEA) is demonstrated for maintaining pH control of the anolyte and catholyte compartments of the fuel cell. The prepared DBFC with the BIMEA yielded a promising peak power density of 110 mW cm−2. This study also investigated the same BIMEA for a hydrogen–oxygen fuel cell (H2–O2 FC). The type of gas diffusion layer used and the gas feed relative humidity were found to impact fuel cell performance. Finally, a BIMEA featuring a silver electrocatalyst at the cathode in a H2–O2 FC was successfully demonstrated.