Influence of Additives on the Reversible Oxygen Reduction Reaction/Oxygen Evolution Reaction in the Mg -Containing Ionic Liquid N-Butyl-N-Methylpyrrolidinium Bis(Trifluoromethanesulfonyl)imide.

The influence of different additives on the oxygen reduction reaction/oxygen evolution reaction (ORR/OER) in magnesium-containing N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([BMP][TFSI]) on a glassy carbon electrode was investigated to gain a better understanding of the electrochemical processes in Mg-air batteries. 18-Crown-6 was used as a complexing agent for Mg ions to hinder the passivation caused by their reaction with ORR products such as superoxide and peroxide anions. Furthermore, borane dimethylamine complex (NBH) was used as a potential water-removing agent to inhibit electrode passivation by reacting with trace impurities of water. The electrochemical processes were characterized by differential electrochemical mass spectrometry to monitor the consumed and evolved O in the ORR/OER and determine the number of transferred electrons. Crown ether and NBH efficiently masked Mg . A stochiometric excess of crown ether resulted in reduced formation of a passivation layer, whereas at too high concentrations the reversibility of the ORR/OER was diminished.