Synthesis of fluorinated biomimetic hydrophobic gas diffusion cathodes for catalytic hydrogen peroxide

Abstract

The electrochemical synthesis of dispersed hydrogen peroxide (H₂O₂) in acidic solutions is of significant interest for the electro-Fenton (EF) process. However, the development of robust and cost-effective catalysts for the selective two-electron oxygen reduction reaction (2e-ORR) remains a challenge. In this study, inspired by the hydrophobic surface of natural rose petals and mimicking their microstructure, we utilized the high adhesion property of polytetrafluoroethylene (PTFE) to bind highly conductive acetylene carbon black (ACET) onto the surface of graphite felt wire mesh. This formed a low-surface-energy, fluorine-doped hydrophobic cathode with a rough and defect-rich surface, optimized for gas diffusion. The cathode demonstrated an impressive H₂O₂ generation rate of 46.21 mg h⁻¹ cm⁻², meeting the requirements for the EF process. In continuous operation, the electrode exhibited exceptional catalytic performance and stability. This can be attributed to the variations in electron distribution density induced by F/C doping and surface defects, where high-density electron domains attract oxygen molecules at the interfaces of hydrated hydrogen ion (H₃O⁺) clusters, promoting the formation of the *OOH intermediate. The hydrophobicity of the interfaces weakly bind to *OOH, favouring desorption to enhance H₂O₂ generation and prevent the side reaction of hydrogen evolution on the wetted electrode surface and further reduction of generated H₂O₂ to H₂O. This study provides a new strategy for designing efficient and stable cathodes to guide future catalyst discovery.