In Situ Study of Oxygen Reduction in Dimethyl Sulfoxide (DMSO) Solution: A Fundamental Study for Development of the Lithium Oxygen Battery
To develop a lithium oxygen (Li O2) battery with an extremely high specific energy, mechanisms for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) on a flat gold electrode in the aprotic polar solvent of dimethyl sulfoxide (DMSO) has been systematically investigated by electrochemistry in combination with in situ UV vis absorption spectroscopy, surface enhanced Raman vibrational spectroscopy (SERS) and ex situ infrared spectroscopy. In the Li free DMSO solution, O2 is efficiently reduced to the superoxide, which forms an ion pair with the tetrabutylammonium (TBA) cation and shows an excellent stability in DMSO. The adsorption of the superoxide on the gold electrode surface has been observed by an in situ SERS measurement. When the Li ion is included in the DMSO, O2 can be further electrochemically reduced to lithium peroxide (Li2O2) and deposited on the electrode surface, although a large amount of superoxide is still produced in the solution. The latter oxide shows a UV vis a.