Construction of a Microchannel Aeration Cathode for Producing H2O2 via Oxygen Reduction Reaction.

Electrochemical oxygen reduction is a promising method for in situ H2O2 production. Its important precondition is that dissolved oxygen molecules have to diffuse to and arrive at the cathode surface for reacting with electrons. Obviously, shortening the diffusion distance is beneficial to improve the reaction efficiency. In this study, a novel microchannel aeration mode was proposed to confine the diffusion distance of O2 to the micrometer level. For this mode, an aeration cathode was fabricated from a carbon block with microchannel arrays. The diameter of each channel was only 10-40 μm. Oxygen will be pumped into every microchannel from the top entry, while an aqueous solution will permeate into microchannels through the bottom entry and pores in the channel wall. This microchannel aeration cathode exhibited a H2O2 yield of up to 4.34 mg h-1 cm-2, about eight times higher than that of the common bubbling aeration mode. The corresponding energy consumption was only 7.35 kWh kg-1, which was superior to most reported results. In addition to H2O2, this aeration cathode may also produce •OH via a one-electron reduction of H2O2. In combination with H2O2 and •OH, phenol, sulfamethoxazole, and atrazine were degraded effectively. We expect that this microchannel aeration cathode may inspire researchers focused on H2O2 production, water pollutant control, and other multiphase interfacial reactions.