A Janus-gas diffusion electrode with suitable hydrophilicity and aerophilicity for highly efficient H2O2 electrosynthesis

Abstract

Low solubility and slow oxygen transport in the electrolyte lead to poor hydrogen peroxide (H2O2) generation performance through oxygen reduction reactions (ORR) at traditional submerged cathodes. Herein, we fabricated a Janus-gas diffusion electrode with asymmetric wettability, high gas permeability, and abundant catalytic active sites using HNO3-modified graphite felt as the substrate, polytetrafluoroethylene (PTFE) as a hydrophobic gas diffusion layer (GDL), and polyvinylidene fluoride (PVDF)/acetylene black(AB) composite as a hydrophilic and aerophilic catalyst layer (CL). Using air as an oxygen supply and a working current density of 10.0mA∙cm-2, the constructed Janus-gas diffusion electrode achieves an H2O2 yield of 39.0mg∙L-1∙cm-2, a current efficiency of 97.8%, and an oxygen utilization ratio of 3.5% at 60min, indicating excellent two-electron ORR performance. The enhanced performance is attributed to the superaerophilicity of the PTFE-based hydrophobic GDL, which provides sufficient oxygen mass transfer and supply. The hydrophilic PVDF-based CL remains good aerophilicity and contains abundant active functional groups due to the AB and graphite felt modified with nitric acid. AB increases the electrode’s specific surface area and gas permeability, allowing for more effective oxygen collection and transport. The electrode is stable for continuous use and indicates a promising application in in-situ H2O2 production.