Confining Treatment of Hydrogen in AB5 Type Hydrogen Storage Alloys

Shinya MORISHITA*, Yasuhito KONDO, Yutaka OHYA, Shin-ichi TOWATA and Katsushi ABE

Toyota Central Research and Development Laboratories, Inc.; 41-1 Yokomichi, Nagakute, Aichi 480-1192 Japan

In order to confine hydrogen in hydrogen storage alloys, a new method, i.e. immersion of the alloy into a solution consisting of some kind of oxidants, was examined. Strong confining effect of hydrogen was observed by the immersion of the alloy in the solution containing chromate ion even after the alloy was kept under the atmosphere for more than 5000 hours.
It was shown from results of XPS and AES that nickel particles on the alloy surface which act as active sites for hydrogen absorption/desorption were changed into nickel oxide by the confining treatment, and the oxide remained to be stable by residual chromate ion on the alloy surface. By formation of the nickel oxide, i.e., vanishment of surface active sites, it is presumed that hydrogen was confined in the hydrogen storage alloy after the treatment.
In the case of Ni-MH batteries, remaining capacity of negative electrodes agree well with the capacity evaluated from the amounts of hydrogen in the hydrogen storage alloys (active material for negative electrode) after the treatment.

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