Effects of alkaline treatment of hydrogen storage alloy on electrocatalytic activity for NaBH₄ oxidation

Activation of the MmNi_4.03Co_0.42Mn_0.31Al_0.24 hydrogen storage alloy electrode is performed by immersing the electrode in a solution containing 6.0 mol dm^-3 NaOH and 0.1 mol dm^-3 NaBH_4. The effects of activation on the electrocatalytic activity of the electrode for NaBH₄ oxidation are investigated by cyclic voltammetry and chronoamperometry. Immersion activation greatly improves the electrocatalytic activity of the alloy electrode. Hydrogen was absorbed in the alloy during the immersion activation treatment and its electrooxidation is responsible for the high initial oxidation current. The stabilized current mainly results from the direct oxidation starting from the borohydride species. The effects of activation on structure and surface chemistry of the alloy are also discussed.