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Understanding of the electrogenerated bulk electrolyte species in sodium-containing ionic liquid electrolytes during the oxygen reduction reaction

journal contribution
posted on 26.10.2017, 00:00 authored by Cristina Pozo-GonzaloCristina Pozo-Gonzalo, L R Johnson, E Jónsson, C Holc, Robert KerrRobert Kerr, D R MacFarlane, P G Bruce, Patrick HowlettPatrick Howlett, Maria ForsythMaria Forsyth
An understanding of the species generated in the bulk ionic liquid electrolyte in the presence of superoxide anion, O2•-, is of interest due to its close relationship to the nature of the electrode reduction products. Unlike conventional organic solvents, ionic liquids are composed entirely of ions, thereby requiring an understanding of the intermediates generated in the bulk electrolyte. The generation of a complex species, [O2•-][C4mpyr+]n[Na+]m, is envisioned in the bulk sodium cation pyrrolidinium-based ionic liquid with a composition depending on the Na+concentration. In this work, the superoxide anion, O2•-, has been considered in theoretical calculations regarding the oxygen reduction reaction in order to determine its average coordination number and also its dynamics in these mixtures. Most interestingly, the final reduction product can be tuned depending on the Na+concentration, whereby a limited supply of Na+favors the superoxide product while a sufficient excess of Na+leads to the formation of the peroxide product. These findings have been identified using a pressure cell and corroborated by rotating ring-disk electrode measurements. Thus, the preferential generation of Na2O2over NaO2could drastically improve the specific energy of the Na-air battery due to a higher number of electrons exchanged.

History

Journal

Journal of Physical Chemistry C

Volume

121

Issue

42

Pagination

23307 - 23316

Publisher

American Chemical Society

Location

Washington, D.C.

ISSN

1932-7447

eISSN

1932-7455

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2017, American Chemical Society