Highly efficient electro-generation of H₂O₂ by adjusting liquid-gas-solid three phase interfaces of porous...

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.