Design of a neutral photo-electro-Fenton system with 3D-ordered macroporous Fe2O3/carbon aerogel cathode: High activity and low energy consumption

A novel three-dimensional ordered macroporous Fe2O3/CA cathode (3DOM-Fe2O3/CA) was fabricated by using self-assembled colloidal crystal template and proposed in solar photo-electro-Fenton (SPEF) process at neutral pH. 3DOM-Fe2O3/CA possessed 3D-ordered interconnecting marcopores (390-425 nm) with a hollow "cylindrical tube" in the vertical direction. Compared to the traditional Fe2O3/CA electrode, the 3DOM-Fe2O3/CA presented higher photocatalytic and Fenton oxidation ability. The interconnecting macropores generated multiple scattering and slow-photon effect for increasing light harvesting efficiency, while the nice channels minimized tortuosity and provided much more efficient mass transport. Almost complete removal of 200 mg L-1 imidacloprid was achieved in 2.5 h with 3DOM-Fe2O3/CA. The dynamic analysis showed that the degradation of imidacloprid follows the pseudo-first order reaction. The apparent rate constant for 3DOM-Fe2O3/CA electrode is 0.326 h(-1), which 2 times higher than that of reference Fe2O3/CA electrode. The energy consumption was used more effectively in SPEF with 3DOM-Fe2O3/CA. EPR and radical trapping experiments revealed that the (OH)-O-center dot radicals were main oxidants in SPEF system and 3D-ordered macroporous favored the formation of (OH)-O-center dot. Besides, 3DOM-Fe2O3/CA electrode presented very low iron leaching (<1 ppm) and retained high catalytic activity after consecutive runs. (C) 2015 Elsevier B.V. All rights reserved.