Fe(II)-Modulated Microporous Electrocatalytic Membranes for Organic Microcontaminant Oxidation and Fouling Control: Mechanisms of Regulating Electron Transport toward Enhanced Reactive Oxygen Species Activation.

Regulation of the fast electron transport process for the generation and utilization of reactive oxygen species (ROS) by achieving fortified electron "nanofluidics" is effective for electrocatalytic oxidation of organic microcontaminants. However, limited available active sites and sluggish mass transfer impede oxidation efficiency. Herein, we fabricated a conductive electrocatalytic membrane decorated with hierarchical porous vertically aligned Fe(II)-modulated FeCo layered double hydroxide nanosheets (Fe(II)-FeCo LDHs) in an electro-Fenton system to maximize exposure of active sites and expedite mass transfer. The nanospaced interlayers of Fe(II)-FeCo LDHs within the microconfined porous structure formed by its vertical nanosheets highly boost the micro/nanofluidic distribution of target pollutants to active centers/species, achieving accelerated mass transferability. Aliovalent substitution by Fe(II) activates in-plane metallics to maximize the available active sites and makes each Fe(II)-FeCo LDH nanosheet a geometrical nanocarrier for constructing a fast electron "nanofluidic" to accelerate Fe(II) regeneration in Fe(III)/Fe(II) cycles. As a result, the Fe(II)-FeCo LDHs exhibited improved reactivity in catalyzing H2O2 to •OH and 1O2. Accordingly, the membrane exhibited a higher atrazine degradation kinetic (0.0441 min-1) and degradation rate (93.2%), which were 4.7 and 2.1 times more than those of the bare carbon nanotube membrane, respectively. Additionally, the enhanced hydrophilic and strongly oxidized reactivity synergistically mitigated the organic fouling occurring in the pores and surface of the membrane. These findings clarify the activation mechanism of ROS over an innovative electrocatalytic membrane reactor design for organic microcontaminant treatment.