A Three-dimensional Floating Air Cathode with Dual Oxygen Supplies for Energy-efficient Production of Hydrogen...

The in situ and cleaner electrochemical production of hydrogen peroxide (H₂O₂) through two-electron oxygen reduction reaction has drawn increasing attentions in environmental applications as an alterantive to traditional anthraquinone process. Air cathodes avoid the need of aeration, but face the challenges of declined performance during scale-up due to non-uniform water infiltration or even water leakage, which is resulted from changing water pressures and immature cathode fabrication at a large scale. To address these challenges, a three-dimensional (3-D) floating air cathode (FAC) was built around the commercial sponge, by coating with carbon black/poly(tetrafluoroethylene) using a simple dipping-drying method. The FAC floated on the water-air interface without extensive water-proof measures, and could utilize oxygen both from passive diffusion and anodic oxygen evolution to produce H₂O₂. The FAC with six times of dipping treatment produced a maximum H₂O₂ concentration of 177.9 ± 26.1 mg L^-1 at 90 min, with low energy consumption of 7.1 ± 0.003 Wh g^-1 and stable performance during 10 cycles of operation. Our results showed that this 3-D FAC is a promising approach for in situ H₂O₂ production for both environmental remediation and industrial applications.