FeOCl Nanoparticles Loaded onto Oxygen-Enriched Carbon Nanotubes and Nickel-Foam-Based Cathodes for the Electro-Fenton Degradation of Pollutants

Electrochemical advanced oxidation processes (EAOPs) are a class of promising technologies for wastewater remediation. The challenge of EAOPs is the in situ generation and activation of hydrogen peroxide (H₂O₂) to evolve reactive oxygen species (ROS) simultaneously with low energy consumption and high performances. In this work, we designed an EAOP system, coupling FeOCl nanoparticles on oxygen-enriched carbon nanotubes (O-CNTs) and a nickel foam (FeOCl/O-CNTs/NF) cathode for electro-Fenton (EF) reactions and an IrO₂/Ti anode for anodic oxidation (AO) simultaneously. Specifically, the defects and oxygen functional groups on O-CNTs introduced by a modified Hummers’ method could induce the charge redistribution of O-CNTs for outstanding two-electron oxygen-reduction-reaction performances (H₂O₂ selectivity of 73%) and provide more anchoring sites for the loading of active cocatalyst nanoparticles. Thus, abundant FeOCl nanoparticles were successfully loaded onto O-CNTs. Such a FeOCl/O-CNTs/NF cathode exhibited a high H₂O₂ production rate of 95 mmol g_cat^–1 h^–1 because of the improved exposure of catalytic active sites supported on nickel foam to attain a large specific surface area. ^•OH was generated from H₂O₂ via both heterogeneous and homogeneous EF processes induced by the FeOCl/O-CNTs/NF cathode and leached ferrous ions accordingly. Sulfamethoxazole (SMX) was completely removed within 30 min at a low specific energy consumption of 0.024 kWh g^–1 SMX^–1. Thus, the simultaneous FeOCl/O-CNTs/NF-based EF system and AO provide an efficient and cost-effective technology for organic contaminant remediation.