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 Fe 2 O 3 /CA cathode (3DOM–Fe 2 O 3 /CA) was fabricated by using self-assembled colloidal crystal template and proposed in solar photo-electro-Fenton (SPEF) process at neutral pH. 3DOM–Fe 2 O 3 /CA possessed 3D-ordered interconnecting marcopores (390–425   nm) with a hollow “cylindrical tube” in the vertical direction. Compared to the traditional Fe 2 O 3 /CA electrode, the 3DOM–Fe 2 O 3 /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–Fe 2 O 3 /CA. The dynamic analysis showed that the degradation of imidacloprid follows the pseudo-first order reaction. The apparent rate constant for 3DOM–Fe 2 O 3 /CA electrode is 0.326   h −1 , which 2 times higher than that of reference Fe 2 O 3 /CA electrode. The energy consumption was used more effectively in SPEF with 3DOM–Fe 2 O 3 /CA. EPR and radical trapping experiments revealed that the OH radicals were main oxidants in SPEF system and 3D-ordered macroporous favored the formation of OH. Besides, 3DOM–Fe 2 O 3 /CA electrode presented very low iron leaching (<1   ppm) and retained high catalytic activity after consecutive runs.