The Solvent Effect on H O Generation at Room Temperature Ionic Liquid|Water Interface.

H O is a versatile chemical and can be generated by the oxygen reduction reaction (ORR) in proton donor solution in molecular solvents or room temperature ionic liquids (IL). We investigated this reaction at interfaces formed by eleven hydrophobic ILs and acidic aqueous solution as a proton source with decamethylferrocene (DMFc) as an electron donor. H O is generated in colorimetrically detectable amounts in biphasic systems formed by alkyl imidazolium hexafluorophosphate or tetraalkylammonium bis(trifluoromethylsulfonyl)imide ionic liquids. H O fluxes were estimated close to liquid|liquid interface by scanning electrochemical microscopy (SECM). Contrary to the interfaces formed by hydrophobic electrolyte solution in a molecular solvent, H O generation is followed by cation expulsion to the aqueous phase. Weak correlation between the H O flux and the difference between DMFc/DMFc redox potential and 2 electron ORR standard potential indicates kinetic control of the reaction.