Hydrogen and Hydrogen Peroxide Formation in Trifluorotoluene-Water Biphasic Systems

Hydrogen or hydrogen peroxide can be generated in liquid-liquid biphasic systems, where the organic phase contains sufficiently strong electron donor (whose redox potential is lower than the potential of reversible hydrogen electrode). H2O2 generation with acidified aqueous phase occurs prior to H2 evolution when oxygen is present. No other organic solvent than highly toxic 1,2-dichloroethane (DCE) has been reported in biphasic system for H2 or H2O2 generation. In this work, we have used trifluorotoluene (TFT) instead of carcinogenic DCE, and studied these reactions in TFT-water biphasic system. To evaluate H2 flux, scanning electrochemical microscopy potentiometric approach curves to the TFT-water interface were recorded. H2O2 was detected voltametrically at a microelectrode located in the vicinity of the interface. H2 and H2O2 are formed and both reactions occur also in the absence of a hydrophobic salt in the organic phase. Their thermodynamics was discussed on the basis of Gibbs energies determined electrochemically with droplet-modified electrodes. The results show that DCE can be replaced by a noncarcinogenic solvent and the biphasic system for H2 and H2O2 generation can be simplified by elimination of the uncommon hydrophobic salt from the organic phase.