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

Hydrogen peroxide (H 2 O 2 ) in situ electrosynthesis by O 2 reduction reaction is a promising alternative to the conventional Fenton treatment of refractory wastewater. However, O 2 mass transfer limitation, cathodic catalyst selectivity, and electron transfer in O 2 reduction remain major engineering obstacles. Here, we have proposed a systematic solution for efficient H 2 O 2 generation and its electro-Fenton (EF) application for refractory organic degradation based on the fabrication of a novel ZrO 2 /CMK-3/PTFE cathode, in which polytetrafluoroethylene (PTFE) acted as a hydrophobic modifier to strengthen the O 2 mass transfer, ZrO 2 was adopted as a hydrophilic modifier to enhance the electron transfer of O 2 reduction, and mesoporous carbon (CMK-3) was utilized as a catalyst substrate to provide catalytic active sites. Moreover, feasible mass transfer of O 2 from the hydrophobic to the hydrophilic layer was designed to increase the contact between O 2 and the reaction interface. The H 2 O 2 yield of the ZrO 2 /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 H 2 O 2 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 H 2 O 2 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 H 2 O 2 electrosynthesis.