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Insights into the reversible oxygen reduction reaction in a series of phosphonium-based ionic liquids
journal contributionposted on 2014-10-22, 00:00 authored by Cristina Pozo-GonzaloCristina Pozo-Gonzalo, Patrick HowlettPatrick Howlett, J L Hodgson, L A Madsen, D R MacFarlane, Maria ForsythMaria Forsyth
New findings supporting the stability of the superoxide ion, O2˙(-), in the presence of the phosphonium cation, [P6,6,6,14](+), are presented. Extended electrochemical investigations of a series of neat phosphonium-based ILs with different anions, including chloride, bis(trifluoromethylsulfonyl)imide and dicyanamide, demonstrate the chemical reversibility of the oxygen reduction process. Quantum chemistry calculations show a short intermolecular distance (r = 3.128 Å) between the superoxide ion and the phosphonium cation. NMR experiments have been performed to assess the degree of long term degradation of [P6,6,6,14](+), in the presence of superoxide and peroxide species, showing no chemically distinct degradation products of importance in reversible air cathodes.