Flow-through electro-Fenton using nanoconfined Fe-Mn bimetallic oxides: Ionization potential-dependent micropollutants degradation mechanism

Herein, we present a flow-through electro-Fenton system for highly efficient and selective degradation of organic contaminants. The essential to this design was a functional nanohybrid filter cathode consisting of an electroactive carbon nanotubes (CNT) filter functionalized with bimetallic Fe/Mn oxide nanoparticles under nanoconfinement. Results suggested that the nanoconfined Fe/Mn-in-CNT filter exhibited a much higher organic degradation kinetics (1.65 times) relative to its unconfinement counterpart (Fe/Mn-out-CNT). Singlet oxygen was the primary reactive oxygen species in the Fe/Mn-in-CNT-based system, in sharp contrast with the hydroxyl radical-mediated pathway in the Fe/Mn-out-CNT-based system. The efficacy was closely correlated with the ionization potential of target organic molecules, with preferentially oxidized organics with the electron-donating ability. Both experimental evidences and theoretical results collectively revealed the superior performance associated with the synergistic effects among Fe, Mn, CNT, and electric field in the nanoconfined system.