The electrochemical oxidation of BH4 − in a molten NaOH–KOH eutectic mixture (0.515:0.485 mole fractions), is investigated for the first time by cyclic voltammetry and electrochemical impedance spectroscopy. Anodically oxidized Ni is electrocatalytically more active than Pt for BH4 − oxidation in the molten alkali electrolyte as shown by the more than three times higher exchange current density (i.e. 15.8 mA cm−2 vs. 4.6 mA cm−2 at 185 °C). Next the proof-of-concept for a novel BH4 −/IO4 − molten alkali electrolyte battery is presented. Using oxidized Ni mesh anode and Pt mesh cathode a maximum power density of 63 mW cm−2 is achieved at 185 °C.