Borohydrides in alkaline media are potential fuels for fuel cells due to their high energy and power density. In this work, we studied the anodic oxidation of borohydrides on a nickel electrode. The open-circuit potential was found to be about 0.15-0.2 V more negative than the hydrogen potential, depending on the concentration of BH4-. The results of polarization measurements indicated that a high power density can be achieved for the BH4-/Ni system. However, the coulombic efficiency was found to be 50% or less due to hydrogen evolution. A further investigation showed that hydrogen gas was not only generated from the hydrolysis reaction, but also from the electrochemical reaction. The actual anodic reaction of borohydride on the Ni electrode was proved to be a four-electron process rather than an eight-electron one. (C) 2003 The Electrochemical Society.