Zinc Anode for Direct Borohydride Fuel Cells

Zinc is evaluated as a negative electrode for the direct electrochemical oxidation of sodium borohydride ͑NaBH 4 ͒.Open-circuit potential measurements, cyclic voltammetry, chronoamperometry, and chronopotentiometry are used to characterize the electrode behavior, namely, the oxidation reaction at the Zn/borohydride interface.Two consecutive oxidation steps are identified, and a possible working mechanism is proposed.A relatively low electrocatalytic activity of Zn for borohydride oxidation is indicated.A laboratory direct sodium borohydride/hydrogen peroxide ͑NaBH 4 /H 2 O 2 ͒ fuel cell using a Zn anode is studied at room temperature.Cell voltages of 2.14 V and short-circuit currents of 1.05 A cm -2 are reported but cell stability is limited to 6 h operation.Energy densities and maximum specific capacities of 2799 Wh kg -1 and 1577 Ah kg -1 , respectively, are obtained.A power density of about 470 mW cm -2 at a cell voltage of 1.10 V and a current density of 426 mA cm -2 is reported but it cannot be sustained for appreciable operation times.