Polytetrafluoroethylene-based gas diffusion electrode for electrochemical generation of hydrogen peroxide

Hydrogen peroxide (H2O2) is a versatile oxidizing agent with numerous applications in various industries. One application of H2O2 is for water treatment, where it is combined with an ultraviolet (UV) radiation source to produce hydroxyl radicals. For point-of-use water treatment devices, the in-situ electrochemical generation of H2O2 is a more attractive solution compared with the external addition of chemicals. One common electrode for H2O2 production is gas diffusion electrode (GDE), which facilitates oxygen transport to the reaction zone. In our study, a GDE was developed based on an expanded polytetrafluoroethylene (ePTFE) substrate for the in-situ cathodic production of H2O2. The GDE characterization indicated its longevity and tolerance to a pressure difference of more than 70 psi, which is typical in residential water distribution systems. The performance of the GDE was evaluated in an electrochemical cell based on various parameters. The cell generated ∼0.6 mM H2O2 at a catalyst loading of 0.22 mg cm–2, flow rate of 40 mL min–1, and current density of ∼200 A m–2. When coupled with a UV-LED array, the ePTFE-based cell was able to oxidize >60% of methylene blue. To the best of our knowledge, this is the first study in which an ePTFE-based GDE has been applied to the electrochemical generation of H2O2, with the ePTFE network as the gas diffusion layer (GDL), thus making the system practically leak-free. The air-breathing electrochemical cell with the ePTFE-based GDE is a reliable means of generating H2O2.