Boosting hydrogen peroxide electro-generation by adjusting the wetting state of porous Janus electrode during oxygen reduction reaction

Abstract

This study aims to design a porous Janus polyacrylonitrile-based carbon fiber (PCF) electrode with asymmetric interfacial wettability for the simultaneous management on oxygen diffusion and ion transfer for H₂O₂ electro-generation. The wetting state of PCF electrode is adjusted by the facile deposition of polytetrafluoroethylene (PTFE) via capillarity. In contrast to single aerophobic and aerophilic electrodes, the Janus PCF electrodes provide a stable gas film for promoting oxygen transfer while ensuring rapid ion migration and release. Compared to the other Janus electrodes, the porous PCF electrode subjected to three cycles of PTFE modification (named Janus-3) exhibit richer functional groups that improves two-electron oxygen reduction reaction (2e⁻-ORR) performance with reduced onset potential and higher current increase rate. And the excellent characteristics of Janus-3 contribute to the highest H₂O₂ production rate of 10.61 ± 0.13 mg h⁻¹ cm⁻² in a flow-through electrochemical system, along with the highest current efficiency (CE) and oxygen utilization efficiency (OUE) values of 83.63 ± 1.01 % and 81.22 ± 4.13 %, respectively. The oxygen mass transfer and ion transport mechanism of H₂O₂ electro-generation are revealed. Lastly, long-lasting operation stability of Janus-3 and its high H₂O₂ production, CE, and OUE suggest great potential to replace normal gas diffusion electrodes for H₂O₂ electro-generation.