Effect of pressure on the electrochemical generation of hydrogen peroxide in undivided cells on carbon felt electrodes

Abstract

The electrochemical generation of H2O2 can be performed in aqueous solutions by cathodic reduction at carbonaceous cathodes of oxygen coming from air. The performances of the process in terms of concentration of H2O2 and current efficiency (CE) are limited by the low solubility of oxygen in water at atmospheric pressure. However, the solubility of oxygen can be increased upon enhancing the air pressure. The effect of pressure on the electrochemical generation of hydrogen peroxide was studied in undivided cells changing the pressure from 0 to 30 relative bar and the current density from 1 to 100mAcm−2. Simple carbon felt and compact graphite cathodes were first used. A dramatic effect of the pressure was shown: at carbon felt a concentration of hydrogen peroxide slightly lower than 30mM was obtained by working at 30bar and 20mAcm−2, about two orders of magnitude higher than that achieved at atmospheric pressure, as a result of mass transport intensification. The utilization of both a modified carbon felt (with carbon black and polytetrafluoroethylene) and relatively low pressures allowed to further enhance the generation of H2O2 and the CE. Under the best conditions (30bar and 100mAcm−2), concentrations up to 225mM together with the highest production rate (1.84mmol H2O2 cm−2h−1 and 98.9% CE) in an electrolytic system fed with air are reported.