Passivating surface states of graphitic carbon nitride for improved photocatalytic Fenton-like decontamination

Graphitic carbon nitride (g-C3N4) is a promising photocatalyst for peroxymonosulfate (PMS) activation towards water treatment, but its inherent surface defects always lead to serious recombination wasting charge carriers. Herein, we constructed cobalt doped aluminum oxide overlayer (AlOx-Co) on g-C3N4 nanosheets, passivating surface states for accelerated photocatalytic PMS activation. The AlOx coating prevents dangling bonds associated with surface recombination, and the Co doping reduces dynamic barrier. Thus, g-C3N4/AlOx-Co (0.0745 min−1) exhibits a 3.5 times higher activity than bare g-C3N4 (0.0168 min−1) towards iohexol degradation. Systemic spectroscopic and photoelectrochemical measurements reveal that AlOx-Co overlayer could weaken in-band recombination and relieve Fermi level pinning, which facilitate the charge transfer. Meanwhile, this overlayer has suitable thickness (3 ∼ 5 nm) for feasible tunneling effects to generate surface-bound radicals. Our work attempts to overcome inefficient surface charge separation and transfer simultaneously for improved contaminant removal via photocatalytic Fenton-like catalysis.