A kW-Class NaBH4/H2O2 Fuel Cell for Air Independent Propulsion

A kilo-Watt-class direct sodium-borohydride/hydrogen-peroxide (NaBH4 /H2 O2 ) fuel cell is fabricated and characterized in this research. Aqueous solution of NaBH4 is directly utilized at the fuel cell anode in place of gaseous hydrogen. Similarly H2 O2 /water solution is directly reduced at the cathode without being first converted through molecular oxygen. The direct utilization of fuel/oxidant results in much higher (35% higher) efficiency in energy utilization. The potential for a very high efficiency (over 80%) was fully validated in the experiments, because the use of H2 O2 overcomes the oxygen over-potential problem inherent to prior H2 /O2 fuel cell designs. Initial results indicate: 1) conversion efficiency over 50% at a practical current density of 200 mA/cm2 ; 2) power density over 0.5 W/cm2 , at 60 degree Celsius. The kilo-Watt-stack consists of 24 cells, generating an OCV (open circuit voltage) of ∼ 42 V. The design of the reactant manifold overcomes some issues unique to an all-liquid-reactant fuel cell. Such a technology is ideal for propulsion/power in air independent environment such as space and underwater.Copyright © 2006 by ASME