ELECTROCHEMICAL CHARACTERIZATION OF HYDROGEN STORAGE ALLOYS MODIFIED WITH METAL-OXIDES

Negative electrodes were made from hydrogen storage alloys (MmNi3.6Mn0.4Al0.3Co0.7) modified by mixing them with metal oxide powders. The discharge capacity of cathodes was greatly increased by the modification with metal oxides with high electric conductivity, for example RuO2 and Co3O4. An exchange current density (J(o)) for the hydrogen electrode reaction was also increased remarkably by modification with metal oxides. High-rate dischargeability was found to increase asymptotically with an increment of J(o). An impedance analysis indicated that the modification of the alloy powder with the metal oxides decreased the charge-transfer resistance. The mode of action of metal oxides was discussed on the basis of the electrocatalytic activity of the modified surface.