Influence of Chemical Structure and Temperature on Oxygen Reduction Reaction and Transport in Ionic Liquids

The ORR mechanism is studied in the context of metal-air batteries in three ionic liquids, 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([Py-1,Py-4]TfO), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm]TfO) and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([BDMIm]Tf2N). An electrochemical scheme combining four electrochemical techniques (CA, CV at macro-disk electrode, linear sweep voltammetry at rotating disk electrode (LSV at RDE) and CV at microelectrode (CV at ME)) is developed to perform fast determination of oxygen parameters (concentration c* and diffusion coefficient D) of electrolyte at various conditions. The electrochemical study has revealed the influence of acidity of ionic liquid to the reversibility of the O-2/O-2(center dot-) redox reaction. The influence of temperature (up to 100 degrees C) on the mechanism change of ORR as well as the changes of c* and D in three ionic liquids have been examined using the developed electrochemical method. The result has shown that the T-dependency of c* is much less prominent than that of D.