Enhancement of oxygen reduction reaction rate by addition of water to an oxidatively stable ionic liquid electrolyte for lithium-air cells

•DEMETFSI ionic liquid is oxidatively stable in the presence of moisture.•Oxygen reduction rates in water saturated DEMETFSI show 10 × increase.•Oxygen reduction reaction (ORR) onset decreased by 40 mV.•Addition of water catalyzes ORR in DEMETFSI ionic liquid.

The oxygen reduction reaction in an ionic liquid (IL) consisting of N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (DEME) cation and the bis(trifluoromethanesulfonyl)imide (TFSI) anion was investigated in the anhydrous and water saturated conditions respectively. The IL was demonstrated to be stable in the operating range of a lithium air cell in both the anhydrous and water saturated conditions. The addition of water was found to lower the overpotential for the oxygen reduction reaction by 40 mV. Finally, the reaction rate constant was found to increase by an order of magnitude with the addition of water hence demonstrating the tendency of water to promote/catalyze the oxygen electrochemistry in non-aqueous systems.

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