The electrochemistry of an alkaline, aqueous cell based on sodium borohydride, NaBH4, oxidation has been studied, Cell performance has been elucidated in 3.6 cm(2) laboratory cells constructed with an air cathode and an anode current collector made of highly dispersed gold/platinum particles supported on high-surface area carbon silk. The number of electrons utilized per molecule of BH4- oxidized (similar to 6.9 out of a possible 8) implies efficient utilization of the BH4- oxidation. Specific energies > 180 W h/kg (based on total fuel weight) and power densities > 20 mW/cm(2) at room temperature and > 60 mW/cm(2) at 70 degrees C have been obtained.