ELECTROCHEMICAL CHARACTERIZATION OF SURFACE-MODIFIED NEGATIVE ELECTRODES CONSISTING OF HYDROGEN STORAGE ALLOYS

Negative electrodes consisting of MmNi3.6Mn0.4Al0.3Co0.7 alloy powder filled in a porous nickel substrate were modified by using different electroless plating baths or alkaline solutions containing hypophosphite as a reducing agent. The deposited metals function as a microcurrent collector and then increase the discharge capacity of the negative electrodes. In contrast, modification with a reducing agent gives rise to high electrocatalytic activity of the negative electrodes which leads to a remarkable reduction in overvoltage in charging and discharging even at the first cycle. It was found that such simple surface modifications improved the performance of negative electrodes under appropriate conditions with respect to the amount of electroless deposit or the concentration of reducing agent.