Mg and Mg alloys are expected to be an active material for the negative electrode of air batteries ¹⁾ because they dissolve actively in the aqueous solution at less noble potential. However, the hydrogen evolution is occurred on the Mg and Mg alloys during the anodic dissolution in the aqueous solution, which calls the negative difference effect, NDE ^{2, 3)}. It may lead to the self-discharge and loss of discharge capacity of air batteries in operation.

In the present study, we determined the hydrogen evolution rate on Mg and Mg alloys during anodic dissolution by gas-chromatographic analysis. Song et al. ⁴⁾ reported the hydrogen evolution behavior of Mg and Mg alloys. They ⁴⁾ carried out the gas collection by using a burette vertically mounted over the funnel to estimate the volume of hydrogen gas generated on Mg alloys at different applied current density. Comparing to this, we previously developed an electrochemical cell combined with a gas chromatograph ⁵⁾ to perform an in-situ determination of hydrogen evolution rate on Mg during anodic dissolution. In this system, the gas generated on the working electrode is directly delivered to a gas chromatograph by a stream of carrier gas ⁵⁾, namely, the qualitative and quantitative analysis of the gas generated on the working electrode can be carried out. It enables us the analysis of gases involving nitrogen and oxygen during anodic dissolution of Mg and Mg alloys. The details of the developed system and measurement conditions are described in our previous work ⁵⁾. In the present study, hydrogen evolution rate on various kinds of Mg alloys during anodic dissolution were determined by developed system and the gases evolved on Mg alloys during anodic dissolution were discriminated.

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