Effect of surface treatment with boiling alkaline solution on electrochemical properties of the ZrNi alloy electrode

•The ZrNi powder or electrode was immersed in a boiling 6 M KOH aqueous solution.•The outer ZrO2 native surface was replaced Ni(OH)2 by the boiling alkaline treatment.•The initial discharge capacity at 333 K for the surface treated ZrNi electrode was 320 mAh g−1.•The ZrNi alloy particles were pulverized for the charge–discharge cycles.

Electrochemical properties of the ZrNi alloy electrode with the boiling alkaline treatment were investigated. The boiling alkaline treatment was performed by immersing ZrNi powder or electrode in a boiling 6 M KOH aqueous solution for 4 h. During the boiling alkaline treatment, the bulk structure of the ZrNi powder, the B33-type (CrB) structure, remained, whereas the outer ZrO2 native surface was replaced by Ni(OH)2. The initial discharge capacity at 10 mA g−1 and 333 K for the ZrNi alloy electrode was increased from 18 to 320 mAh g−1 by the boiling alkaline treatment. However, cycle performance got worse, because the ZrNi alloy particles were pulverized for the charge–discharge cycles.