Efficient H2O2 Electrosynthesis and Its Electro-Fenton Application for Refractory Organics Degradation

Hydrogen peroxide (H2O2) in situ electrosynthesis by O2 reduction reaction is a promising alternative to the conventional Fenton treatment of refractory wastewater. However, O2 mass transfer limitation, cathodic catalyst selectivity, and electron transfer in O2 reduction remain major engineering obstacles. Here, we have proposed a systematic solution for efficient H2O2 generation and its electro-Fenton (EF) application for refractory organic degradation based on the fabrication of a novel ZrO2/CMK-3/PTFE cathode, in which polytetrafluoroethylene (PTFE) acted as a hydrophobic modifier to strengthen the O2 mass transfer, ZrO2 was adopted as a hydrophilic modifier to enhance the electron transfer of O2 reduction, and mesoporous carbon (CMK-3) was utilized as a catalyst substrate to provide catalytic active sites. Moreover, feasible mass transfer of O2 from the hydrophobic to the hydrophilic layer was designed to increase the contact between O2 and the reaction interface. The H2O2 yield of the ZrO2/CMK-3/PTFE cathode was significantly improved by approximately 7.56 times compared to that of the conventional gas diffusion cathode under the same conditions. The H2O2 generation rate and Faraday efficiency reached 125.98 mg·cm−2·h−1 (normalized to 5674.04 mmol·g−1·h−1 by catalyst loading) and 78.24% at −1.3 V versus standard hydrogen electrode (current density of −252 mA·cm−2), respectively. The high H2O2 yield ensured that sufficient ·OH was produced for excellent EF performance, resulting in a degradation efficiency of over 96% for refractory organics. This study offers a novel engineering solution for the efficient treatment of refractory wastewater using EF technology based on in situ high-yield H2O2 electrosynthesis.