Highly efficient electro-generation of H2O2 by adjusting liquid-gas-solid three phase interfaces of porous carbonaceous cathode during oxygen reduction reaction

Abstract

Equilibrium of three reactants (oxygen, proton and electron) in oxygen reduction reaction at large current flux is necessary for highly efficient electro-generation of H2O2. In this work, we investigated reactants equilibrium and H2O2 electrochemical production in liquid-gas-solid three phase interfaces on rolling cathodes with high electroactive area. Electrocatalytic reaction accelerated the electrolyte intrusion into hydrophobic porous catalyst layer for higher electroactive surface area, resulting in a 21% increase of H2O2 yield at 15 mA cm−2. Air aerated cathode submerged in air/O2 aeration solution was unable to produce H2O2 efficiently due to the lack of O2 in three phase interfaces (TPIs), especially at current density > 2.5 mA cm−2. For air breathing cathode, stable TPIs inside the active sites was created by addition of gas diffusion layer, to increase H2O2 production from 11 ± 2 to 172 ± 11 mg L−1 h−1 at 15 mA cm−2. Pressurized air flow application enhanced both oxygen supply and H2O2 departure transfer to obtain a high H2O2 production of 461 ± 11 mg L−1 h−1 with CE of 89 ± 2% at 35 mA cm−2, 45% higher than passive gas transfer systems. Our findings provided a new insight of carbonaceous air cathode performance in producing H2O2, providing important information for the practical application and amplification of cathodes in the future.