Oxidative breakdown of electrolyte solutions in 3-methyl oxazolidin-2-one (NMO) on photoexcited TiO2, and platinum electrodes was studied by (photo)electrochemistry, in-situ FTIR and GC-MS. The solvent oxidation at the platinum electrode starts at about 4.5 V vs. LiLi+. It proceeds by a stepwise mechanism, while an intermediate product is detectable within a time scale of 10(1) to 10(2) s. Carbon dioxide is one of the final products. Another product is an electrochemically active species, showing irreversible reduction at 3.7 to 3.9 V, and pseudo-reversible reduction/oxidation at 2.9 to 3.1 V. This product was tentatively identified as a nitrogen-containing heterocycle.