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

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