Generation of superoxide ions in the electrochemical reduction of molecular oxygen in concentrated lithium bis(trifluoromethanesulfonyl)imide aqueous solutions

Electrolytic generation of superoxide ions (O₂^•-) from the reduction of molecular oxygen (O₂) was previously successful only by the formation of a hydrophobic reaction field on an electrode surface. However, in our study, O₂^•- was generated in concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) aqueous solutions that can be confirmed electrochemically or spectroscopically. In the concentrated LiTFSI aqueous solution, O₂^•- was more stable than it is in normal aqueous solutions, but it was not as stable as it is in organic solvents. When other related-concentrated electrolyte solutions are used, the electrolysis of O₂^•- greatly varies depending on the types of cations and anions used as electrolytes. Thus, a synergistic effect of reducing free water with cations and creating a hydrophobic atmosphere with anions was achieved.