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Oxygen and hydrogen gas recombination in NiMH cells
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2012 (English)In: Journal of Power Sources, ISSN 0378-7753, Vol. 208, 232-236 p.Article in journal (Refereed) Published
Abstract [en]

The kinetics of oxygen and hydrogen gas recombination on the metal hydride electrode in a NiMH cell is investigate as function of gas pressure, temperature, cycling and a hydrophobic additive. Both oxygen and hydrogen gas recombination rates in the NiMH cells are found to be linearly proportional to the gas pressure, indicating that surface processes with a constant number of reaction sites could be the rate limiting step. The rate of oxygen gas recombination is, however, more than 10 times faster than that of hydrogen at the same pressure. As the temperature increases, both reaction rates increase very rapidly, even though the solubilities of the gases in the KOH electrolyte decrease with temperature. The activation energies for oxygen and hydrogen gas recombination are 32.6 kJ mol(-1) and 27.0 kJ mol(-1), respectively. The reactions rates also increase as the cells are cycled. This indicates, that the number of active sites increases, as the surface area increases, due to the continuously decrepitating of the alloy particles. The hydrogen gas absorption rate increases dramatically after a large number of cycles due the drying of the MH electrode. A hydrophobic FTFE additive in the MH electrode can significantly improve hydrogen absorption efficiency in NiMH cells.

Place, publisher, year, edition, pages
2012. Vol. 208, 232-236 p.
Keyword [en]
NiMH batteries, Cell pressure, Gas recombination
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-80006DOI: 10.1016/j.jpowsour.2012.02.028ISI: 000303286500029OAI: diva2:552547


Available from: 2012-09-14 Created: 2012-09-12 Last updated: 2012-09-14Bibliographically approved

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Noréus, Dag
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